Diesel Engine Powered Cogeneration for a Dairy Farm. Jennifer Fan. A thesis submitted in partial fulfillment of the requirements for the degree of

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1 Diesel Engine Powered Cogeneration for a Dairy Farm Jennifer Fan A thesis submitted in partial fulfillment of the requirements for the degree of BACHELOR OF APPLIED SCIENCE Supervisor: J. S. Wallace Department of Mechanical and Industrial Engineering University of Toronto March, 2007

2 Abstract Cogeneration emerges as a sustainable alternative to conventional energy production methods. By recovering wasted heat during electricity production, cogeneration offers higher efficiency, reduced costs and reduced greenhouse gas emissions. In agriculture, on-site diesel engines generators are used to provide electricity for farm equipment. By adding a heat recovery system to the engine generator set, heat rejected to the coolant and exhaust can be used to fulfill water or space heating needs. The feasibility of applying a diesel engine powered cogeneration system to a 110-cow dairy farm in Waterloo, Ontario was investigated. A conceptual diesel engine powered cogeneration system was designed based on specific heating and electrical requirements of the dairy farm. A simulation was developed to evaluate the system s performance under different operating conditions. This report explains the procedures undertaken in the analysis and provides insight on the technical, economical, and environmental aspects of the implementation. It was concluded that the dairy farm would not benefit from the adoption of a diesel engine powered cogeneration system.

3 Acknowledgement The author wishes to acknowledge the following for their assistance in the completion of this study. Professor J. S. Wallace for his support, guidance, and advice. Mr. Michael Schramm and Ms. Amelia Gulkis of EnSave Inc. for providing additional information regarding the Brown Farm energy assessment. Ms. Nancy Wang of Modine Manufacturing Co. Inc., Mr. Arthur Sams of Polar Power Inc. and Mr. Greg MacLeod of Exergy LLC. for their input on exhaust heat exchangers. Mr. Jack Rodenburg, Mr. Brian Lang, Ms. Vicky Osborne, Mr. Gerald Townsend, Mr. Harold House of the Ontario Ministry of Agriculture, Food and Rural Affairs for their valuable input on dairy farm equipment and usage. Mr. Guy Séguin and Ms. Karen Mantel of the Dairy Farmers of Ontario for their valuable input on hot water and electricity consumption on dairy farms. Mr. Frank Daly of Kinvrio Limited, Mr. Mark Binns of Lister Petter, Mr. Mike Cocking of Marathon Engine Systems and Ms. Ashley Grist of EcoPower for answering inquires and providing information on commercially available small-scale cogeneration systems. Mr. Stephen Chan for his support and assistance in editing the thesis report. i

4 Table of Contents ABSTRACT...II ACKNOWLEDGEMENT... I TABLE OF CONTENTS...II LIST OF SYMBOLS... V LIST OF FIGURES... VII OBJECTIVE INTRODUCTION COGENERATION OVERVIEW POTENTIAL BENEFITS OF COGENERATION SYSTEMS ON DAIRY FARMS DIESEL ENGINE COGENERATION SYSTEM SYSTEM OVERVIEW ENGINE GENERATOR CONTROL SYSTEM HEAT RECOVERY SYSTEM PART-LOAD CHARACTERISTICS PERFORMANCE CHARACTERISTICS ANALYSIS OF A DAIRY FARM S ENERGY REQUIREMENT BACKGROUND MILKING SYSTEMS WATER HEATING LIGHTING VENTILATION SPACE HEATING OTHER EQUIPMENT CALCULATING HEAT AND ELECTRICAL DEMAND ELECTRICAL DEMAND SPACE HEATING DEMAND HEATING REQUIREMENT FOR THE MILKING CENTRE HOT WATER HEATING DEMAND ii

5 5.4 DEMAND PROFILES SYSTEM DESIGN OVERVIEW DIESEL ENGINE GENERATOR COOLANT-TO-WATER HEAT EXCHANGER SPACE HEATING SYSTEM EXHAUST-TO-WATER HEAT EXCHANGER SIMULATION DIESEL ENGINE GENERATORS COOLANT-TO-WATER HEAT EXCHANGER 1 (FOR FLOOR HEATING) COOLANT-TO-WATER HEAT EXCHANGER 2 (FOR HOT WATER HEATING) EXHAUST-TO-WATER HEAT EXCHANGER LIMITATIONS TESTING CONDITIONS ANALYSIS RECOMMENDATIONS ECONOMIC COSTS ENVIRONMENTAL CONCERNS CONCLUSION REFERENCES FIGURES AND TABLES APPENDIX A - TEMPERATURE DATA FOR WATERLOO, ONTARIO APPENDIX B-1 - BROWN FARM ELECTRICAL DEMAND PROFILE - SPRING APPENDIX B-2 - BROWN FARM ELECTRICAL DEMAND PROFILE - SUMMER APPENDIX B-3 - BROWN FARM ELECTRICAL DEMANDPROFILE - AUTUMN APPENDIX B-4 - BROWN FARM ELECTRICAL DEMAND PROFILE - WINTER APPENDIX B-5 BROWN FARM HOT WATER DEMAND APPENDIX C: SPECIFICATION DATA FOR CUMMINS DIESEL GENERATOR SET MODEL DNAE 60HZ APPENDIX D-1 - GENERATOR EFFICIENCY CALCULATION iii

6 APPENDIX D-2 - FUEL CONSUMPTION AS A FUNCTION OF ENGINE LOAD APPENDIX D-3 - VOLUMETRIC EFFICIENCY AS A FUNCTION OF BMEP APPENDIX D-4 - EXHAUST OUTLET TEMPERATURE AS A FUNCTION OF BMEP APPENDIX E - FLUID TEMPERATURE FOR FLOOR HEATING AS A FUNCTION OF SUPPLEMENTARY HEAT REQUIRED APPENDIX F-1 SIMULATION RESULTS FOR SPRING APPENDIX F-2 SIMULATION RESULTS FOR SUMMER APPENDIX F-3 SIMULATION RESULTS FOR AUTUMN APPENDIX F-4 SIMULATION RESULTS FOR WINTER APPENDIX G-1 - THERMODYNAMIC PROPERTIES SPECIFIC HEAT CAPACITY OF AIR 91 APPENDIX G-2 - THERMODYNAMIC PROPERTIES SPECIFIC HEAT CAPACITY OF 50/50 ETHLYENE GLYCOL APPENDIX G-3 - THERMODYNAMIC PROPERTIES SPECIFIC HEAT CAPACITY OF WATER APPENDIX G-4 - THERMODYNAMIC PROPERTIES DENSITY OF AIR APPENDIX G-5 - THERMODYNAMIC PROPERTIES DENSITY OF 50/50 ETHYLENE GLYCOL APPENDIX G-6 - THERMODYNAMIC PROPERTIES - DENSITY OF WATER APPENDIX H - FORMULAS USED FOR SIMULATION OF DIESEL ENGINE COGENERATION SYSTEM iv

7 List of Symbols T fluid : fluid temperature change in the floor heating system A: Area Cp coolant: specific heat capacity of coolant Cp water : specific heat capacity of water F: fluid flow rate of the floor heating system H: height L: length : mass flow rate of fuel m fuel m : mass flow rate of fuel at full load fuel_ full m hx1_ coolant: mass flow rate of coolant in coolant-to-water heat exchanger 1 m hx1_ water: mass flow rate of water in coolant-to-water heat exchanger 1 m hx2 _ coolant : mass flow rate of coolant in coolant-to-water heat exchanger 2 m hx2 _ water : mass flow rate of water in coolant-to-water heat exchanger 2 m m hx _ exhaust hx _ water Q : heat transfer : mass flow rate of exhaust in exhaust-to-water heat exchanger : mass flow rate of water in exhaust-to-water heat exchanger Qcoolant1: the amount of heat rejected to coolant from engine 1 Qcoolant2: the amount of heat rejected to coolant from engine 2 Qexhaust: the amount of heat rejected to exhaust from engine 1 Qrequired: the amount of heat required Q ceiling : heat loss in the ceiling Q coolant : heat rejected to coolant from the engine Q coolantfulload : heat rejected to coolant from the engine at full load Q hx1_ coolant : coolant side heat transfer of coolant-to-water heat exchanger 1 Q hx1_ water : water side heat transfer of coolant-to-water heat exchanger 1 Q hx2 _ coolant : coolant side heat transfer of coolant-to-water heat exchanger 2 Q hx2 _ water : water side heat transfer of coolant-to-water heat exchanger 2 v

8 Q Q Q Q Q Q Q Q hx _ exhaust hx _ water perimeter surround surroundfullload supple ventilation wall : exhaust side heat transfer of exhaust-to-water heat exchanger : water side heat transfer of exhaust-to-water heat exchanger : heat loss around the perimeter : heat rejected to surrounding from the engine : heat rejected to surrounding from the engine at full load :supplementary heat required :heat loss through ventilation : heat loss in the wall T coolantin : inlet temperature of coolant T coolantout : outlet temperature of coolant T engine: torque in the engine T exhaustin : inlet temperature of exhaust T exhaustout : outlet temperature of exhaust T fullload : torque in the engine under full load Tin: Indoor temperature Tout: Outdoor temperature T waterin : inlet temperature of water T waterout: outlet temperature of water U: heat transfer coefficient W: width vi

9 List of Figures Figure 1: Conceptual diagram comparing the efficiency and losses of cogeneration and the conventional system. [8] Figure 2: Energy consumption by farm type in Ontario in 1997 (%) [9] Figure 3: Energy consumption by energy type in Ontario dairy farms in 1997 (%) [9] Figure 4: Graph showing applications and percentage of total electricity use on the Brown Farm Figure 5: Electrical requirement calculation for the Brown Farm Figure 6: Conceptual diagram of the diesel engine powered cogeneration system Figure 7: Operation flow chart of diesel engine cogeneration system Figure 8: Electrical demand vs. time Figure 9: Graphical layout of the simulation program Figure 10: System efficiency vs. time Figure 11: Indoor temperature of milking centre vs. time Figure 12: Water temperature (to end use) vs. time vii

10 Objective The purpose of the thesis was to investigate the feasibility of adapting a diesel engine powered system to produce heat and electricity for a small dairy farm 110-cow in Waterloo, Ontario. The thermal and electrical demand of the farm analyzed and quantified and seasonal usage profiles were developed based on an energy assessment of the Brown Farm. A conceptual diesel engine powered cogeneration system was designed based on the site s thermal and electrical requirements. A simple simulation model was developed to evaluate its performance under various operating conditions. The performance, cost, and emissions of the system were analyzed and a conclusion was formed regarding its feasibility for the location. 1

11 1.0 Introduction Cogeneration is an efficient method of generating energy by making use of electricity and heat produced from one single source. There has been increased interested in small onsite cogeneration systems for power generation at locations where both electricity and heat is required. Currently, the most established technology is reciprocating engines, include spark-ignited and diesel engines. The use of spark-ignited engines for cogeneration is restricted to locations where a supply of natural gas is available. The use of diesel engines, on the other hand, is not limited by location, as diesel fuel can be easily transported. Diesel engine generators are widely used in agriculture and can be converted into cogeneration system by adding a heat recovery system. Dairy farms have both electrical and hot water needs that make them a good candidate for cogeneration. On the dairy farm, electricity is used for milking, milk cooling, lighting and ventilation. Immediately after cows are milked, the milk lines and milking equipment require a large amount of high temperature water for cleaning and sanitization. The purpose of this thesis is to study the feasibility of adopting a diesel engine powered cogeneration system on a 110-cow farm in Waterloo, Ontario. The following questions will be answered: Is the implementation technically feasible? Is the implementation economically feasible? 2

12 Does the implementation comply with federal laws and regulations with respect to exhaust emission levels? Finally, a decision would be made regarding whether the diesel engine powered cogeneration system designed should be installed on the farm. 3

13 2.0 Cogeneration 2.1 Overview Cogeneration, also known as combined heat and power, is the simultaneous production of electrical or mechanical energy and useful thermal energy from a single energy stream such as oil, coal, natural or liquefied gas, biomass or solar [1] In conventional energy production, electrical power and heat are produced from separate sources (for example, coal and natural gas). This method is highly inefficient, as only 30-35% of the fuel s energy is converted into electricity, while the rest is lost mostly as heat. [2] Cogeneration reduces energy loss by making use of both heat and electricity produced from one source, increasing efficiency to 80-90%. [3] Increased efficiency results in benefits of lower costs and reduction in greenhouse gas emissions [3] as less fuel is used. Figure 1 illustrates conceptually the benefits of using cogeneration. Applications of cogeneration are most beneficial where electricity and heat energy are both required. The electricity produced can be used to power equipment or appliances and the recovered heat can be used for water heating, space heating, steam production or absorption cooling. There has been increased interest in small-scale onsite cogeneration systems worldwide. Many countries have established targets to increase the use of cogeneration. A cogeneration system normally consists of a prime mover turning an alternator to produce 4

14 electricity and a waste heat recovery system to capture heat from the exhaust and cooling water jacket. [4] Currently, most commercially available cogeneration systems use reciprocating internal combustion engines as the prime mover. Reciprocating engines include compression ignition (Diesel) engines and spark ignition engines. Diesel engines are generally used for larger cogeneration applications while spark ignition is more suitable for smaller cogeneration applications. Other technologies in development include microturbines, Stirling engines and fuel cells. An analytical evaluation comparing the applicability of several prime mover technologies for small scale cogeneration was performed by Aceves, Martinex-Frias, and Reistad. Thermodynamic models were used to evaluate each option s performance in two cases. The first case is the requirement for power and heating and the second case is the requirement for power and chilling. Results showed that diesel engines have the highest fuel utilization efficiency and highest savings in energy of all systems under consideration. However, due to the high cost of diesel fuel compared to natural gas, the cost of operating a diesel engine cogeneration system is higher than the costs of operating a conventional system consuming natural gas. [4] 2.2 Potential Benefits of Cogeneration Systems on Dairy Farms Large energy consumption, the availability of diesel and the vital need of backup power suggests applying diesel engine cogeneration on dairy farms would be very beneficial. 5

15 Dairy farms in Ontario are the second largest energy consumers of all farm types. They use 18% of the total agricultural energy consumption in Ontario in 1997 as shown in Figure 2. [9] Diesel fuel is the main fuel source of dairy farms, representing 42% of total energy consumption as shown in Figure 3. [9] Back-up power is also vital to the live of livestock in the event of a power outage, as demonstrated in the 1998 great ice storm. Areas of Eastern Ontario and Western Quebec were without electricity for weeks due to collapsed power lines. Dairy farmers were at great risk of losing their livestock, because they were unable to heat and ventilate the barns and run milking machines. Not milking cows often enough could lead to udder deterioration and life threatening infectious diseases. The Ontario Ministry of Agriculture, Food and Rural Affairs called on Rental Tools and Equipment Co., a provider of mobile diesel generators to provide immediate solutions. This incident illustrated the importance of back-up power to diary farms and also the potential of having the diesel engine cogeneration system as backup power. [10] There have been test cases of the cogeneration applications on dairy farms. In 2004, Plug Power had installed 5kW fuel cell cogeneration unit was installed at a dairy farm in New York to provide electricity and heat for the farm s parlour. [11] The farm has 300 cows and 200 calves. Cows were milked three times a day. The use of a fuel cell, which primarily emits only water vapour and carbon dioxide, displaces green house gases that would have been emitted by conventional power production. 6

16 3.0 Diesel Engine Cogeneration System 3.1 System Overview The basic elements of a diesel engine cogeneration system include the engine, generator, heat recovery system, and controls. The piston movement of the engine in a two stroke or four stroke cycle drives the generator to produce electricity. [3] Heat is recovered from the exhaust and cooling system of the engine using heat exchangers. 3.2 Engine A diesel engine converts chemical energy into mechanical energy through the instantaneous combustion of fuel in compressed air. The piston moves between the top dead center and bottom dead center during the stages of intake, compression, power and exhaust in a four stroke cycle. The linear movement of the piston forces the rotational movement of the crank shaft by using an off-centre link.[6] Engines can be naturally aspirated, supercharged or turbocharged. A naturally aspirated engine draws in air in the cylinder at atmospheric pressure. A supercharged or turbocharged engine supplies high pressure air to the cylinder. Superchargers are driven by an engine auxiliary output shaft or separate driver while turbochargers are driven by turbine powered by exhaust gases. [7] The use of chargers delivers more air to the engine cylinder, thus providing oxygen and allowing a greater quantity of fuel to be burned. Engine efficiency increases as a result. [6] 7

17 The combustion process from a reciprocating engine produces mainly nitrogen oxides (NO X ), carbon monoxide (CO) and sulphur oxides (SO x ) and particulates. All have a negative impact on the environment and human health. [3] Nitrogen oxides are produced in combustion when fossil fuels are burned in the presence of oxygen [3]. It contributes to acid rain and smog. Carbon monoxide is a poisonous gas produced by the incomplete combustion of fossil fuels due to inadequate oxygen or insufficient residence time at high temperature. [3] Sulphur oxides are produced in combustion of fossil fuels containing sulphur. Sulphur has a corrosive effect on the cogeneration unit, particularly the heat exchangers and exhaust system. [3] Particulates are incomplete combustion of fuel hydrocarbon and also hazardous to human health. [3] Diesel engine exhaust after-treatment system uses oxidation catalysts to combine with the pollutant to produce less harmful compounds. [3] Some engines may use particulate filters in combination with catalysts to reduce emissions. There is limited economical after-treatment technology for NO x emissions for engines of small sizes. [5] 8

18 3.3 Generator A generator converts the mechanical or shaft power of the engine into electrical power. An external force, torque produced from the engine, rotates a loop of wire in a magnetic field, inducing an electromotive force. If an external circuit exists, a current is produced [7]. There are two basic types of generators for alternative current (AC) production. Induction generators are used in parallel with an existing AC power source. Interconnection with the utility power system is simple. Synchronous generators can operate independently or operate in parallel to an AC power source. However, interconnection requires careful planning and design. [7] The commercial standard power frequency in North America is 60Hz. A generator rotational speed is a multiple of 60, typically 1500 or 1800 rpm (rotations per minute). [6] Generators are rated by standby power and prime power. Standby power is a rating for a brief and infrequent operating regime [7] and the prime power is a rating for continuous operation. 3.4 Control System The control system monitors the cogeneration system performance to ensure its safe and efficient operation. The control system should be programmed to shut down the system when the system is operating out of specification or due to failure of its components, It 9

19 should also make necessary adjustments when problems arise with the utility grid. The control system also manages the electrical and thermal output, for example, dumping excess heat when storage is full or operating the engine at partial load when electrical demand is low. [6] 3.5 Heat Recovery System The diesel engine rejects heat from mainly four sources, the jacket coolant, exhaust gases, and low temperature heat from lubricating oil cooling water and turbocharger cooling [3]. Other sources of minor heat loss include radiation and convention from the engine, generator and radiators. [3] The most common sources for heat recovery are the engine exhaust gases and jacket coolant. Exhaust gas heat recovery Exhaust gases at high temperatures can be recovered to produce hot water or steam ranging from 100 to 120 o C [3]. The amount of heat recovered is limited by the temperature of the exhaust gas allowed and the required temperature of the available heat sink. [8] The fouling of materials used for the heat exchanger is also a concern. [8] Jacket water recovery Jacket water used to cool the engine can be fully recovered to produce hot water of temperature between 85 to 90 o C [3] Shell and tube or plate type heat exchangers are most common for this application. The selection of heat exchangers involves the consideration of heat transfer performance and 10

20 fluid mechanical limitations of pressure drop. Total pressure drop in the heat exchanger and piping must not exceed the maximum back pressure drop specified by the engine manufacturer. Material selection of the heat exchanger must also be considered if corrosion issues should arise. The water inlet temperature of the exhaust-to-water heat exchanger must be kept above dewpoint to avoid reaction with sulfur in the exhaust to produce sulfuric acid. The typical arrangement for the heat recovery system involves the use of a secondary heat exchanger to heat the water prior to entering the exhaust-to-water heat exchanger. The same results can also be achieved by using the exhaust-to-water heat exchanger in series with the engine jacket. 3.6 Part-Load Characteristics Diesel engines have good partial load characteristics. The system remains at relatively same electrical efficiency up to 75% of full load. Operating below this point results in a decrease in efficiency, i.e. more fuel is required to produce each kwh of electricity. Thermal efficiency increases as electrical efficiency decreases, there is an increased amount of heat generated from the jacket coolant and exhausts gases. [3] 3.7 Performance Characteristics Cogeneration systems are often evaluated by their electrical efficiency, thermal efficiency, and overall efficiency. [3] Efficiency is defined ratio of the amount of desired output to the amount of required input to produce that output. 11

21 Electrical Effiency ThermalEff iency Electrical Output(kW ) FuelInput(kW) ThermalOut put(kw ) FuelInput(kW) The overall efficiency of a cogeneration system, also known as prime energy ratio (PER), is defined as the fraction of the primary energy (input energy) that can be converted into useful energy (heat and electricity). [3] OverallEff iency Electrical Output(kW) ThermalOut put(kw) FuelInput(kW) Fuel input is calculated using the lower heating value of the fuel (LHV). The lower heating value of the fuel is defined as fuel energy density required to form water vapour during combustion. [7] Efficiency of a cogeneration system depends on the prime mover, its size, the temperature at which heat can be recovered, and its operating strategy. [3] 12

22 4.0 Analysis of a Dairy Farm s Energy Requirement The design specification of the diesel engine cogeneration simulation was developed based on an energy assessment on a 110-cow dairy farm, the Brown Farm, conducted by EnSave Energy Performance Inc. in [11] The assessment examines energy use of the farm and recommended measures to increase energy efficiency and production. The equipment s face plate wattages and operational characteristics were used to calculate the electrical and thermal demands for the simulation. 4.1 Background The dairy farm audited in this assessment is a 110 cow dairy operation. 168,893 kwe of electricity was used during the 12 months of the audit from March 2004 to February This amounts to $20,267 for the cost of electricity at a rate of $0.12 per kw. Dairy cows are milked twice a day, from 5:00 AM to 10:00 AM and from 6:00 PM to 11:00 PM. The electrical energy consumption of the farm is shown in Figure 4. Energy consumption on the dairy farm is dominated by demands for milking operations; 35% of the total electricity use is used to run the milking system, 18% is used for water heating to clean and sanitize the milking equipment, and 9% is used for milk cooling to maintain milk quality. Another large component of energy consumption for the dairy farm is lighting at 25%. 13

23 Energy used on the farm is divided into five major sections: milking systems, milk cooling, water heating, lighting and ventilation. 4.2 Milking Systems Vacuum pumps are used to draw milk through the piping system to the receiver jar. [11] The pumps are used during the milking cycle and washing cycle. The Brown farm operates a 5.6kW (7.5 hp) vacuum pump motor and a 3.7kW (5 hp) vacuum pump motor with 8 milking units for a total of 12.5 hours per day. [11] A 0.75kW (1 hp) milk transfer pump is also used for 2.5 hours per day. Milk needs to be cooled after milking and kept at a chilled temperature to maintain quality. Milk leaves the cow body at approximately 39 o C and needs to be cooled to 3 o C within hours of milking. [15] The basic refrigeration system consists of a bulk tank, a compressor unit, and a condenser unit. [16] Compressors pressurize and circulate coolant through the refrigeration system. The coolant removes heat from milk stored in the bulk tank. Condensers remove heat from the coolant to an air or water heat sink. [17] At the Brown farm, 3552 kg (7830) pounds of milk need to be cooled daily from 34.4 o C (94 o F) to 3.3 o C (38 o F). A plate cooler, using well water in a heat exchanger, partially cools the milk to 19.4 o C (67 o F) before it enters the bulk tank. Two 3.7kW (5 hp) compressors in the bulk tank further cool the milk down to 3.3 o C (38 o F). Each compressor is equipped with two 0.37kW (0.5 hp) condenser fans. Both compressors and the four condenser fans operate 2.5 hours per day after the milking cycle [11]. 14

24 4.3 Water Heating Hot water is needed for cleaning the milking equipment, bulk tank and milk parlour equipment. [18]. High quality milk production with low bacteria count and long shelf life requires the cleaning and sanitizing of milking equipment after every milking cycle. [33] Bulk tanks are washed usually every second day. [19] The bulk tank and milking equipment are cleaned typically using four cycles, pre-rinse, wash, acid rinse and sanitize.[19] Temperature of the water is critical to soften fat and break up protein [32]. The steps for cleaning the system are described below.[33][32] Pre-rinse cycle uses water at 43 o C to 60 o C to remove milk solids and warm up the milk lines immediately after milking. [32]. Wash cycle uses water with a hot solution of chlorinated alkaline cleaner [33] at 71 o C to 76 o C with a circulation time of 6 to 10 minutes. The system is rinsed with cold water. Acid rinse cycle neutralizes residues and dissolves mineral deposits for easy removal for 5 minutes. The recommended water temperature is 35 o C 43 o C. The system is drained completely. Sanitize cycle uses water at 43 o C with chlorine to clean the lines for 3 to 4 minutes immediately before the next milking To reduce energy, the water heater can be controlled to be offline during electrical demand peak hours and online two or three hours before washing is required. [19] A heat recovery system can also use the heat from the compressor and condenser in milk cooling to pre-heat the water. [21] 15

25 The Brown farm uses a 454 L (120 gallon) water tank heated by a 4.5 kw electrical heater. 1056L (279 gallons) of water is heated per day from 12.7 o C (55 o F) to 71.1 o C (160 o F). [11] 4.4 Lighting A well-lit barn creates a healthy environment for cows, workers and better milk quality. In North America, cows reduce food consumption and milk production in respond to shorter daylight hours in winter. To maintain supply of milk during winter months, dairy farmers can use artificial lighting to simulate summer conditions for cows. At the Brown farm, lighting is required in the stalls, milk house and hospital area. Below is a list of lighting fixtures used on the farm. Thirty-three 100 W incandescent fixtures in the tie-stall area for 6 hours per day Four 100 W incandescent fixtures in the hospital area for 11 hours per day Seven 175 W mercury vapour fixtures in the free stall area for 10 hours per day Two 165 W T12 fluorescent fixtures in the hospital area for 10 hours per day Twenty-six 165 W T12 fluorescent fixtures in the free stall for 12 hours per day Four 90 W T12 fluorescent fixtures in the hospital area for 12 hours per day Nine 165 W T12 fluorescent fixtures in the hospital area for 11 hours per day Two 90 W T12 fluorescent fixtures in the milk house for 11 hours per day 16

26 4.5 Ventilation Ventilation is needed at all times in confinement livestock housing to provide oxygen, remove moisture and odors, prevent heat buildup and dilute air-contained disease organisms. [27] Ventilation can be natural, by using the design of the building or mechanical through the use of fans. Ventilation in the summer removes heat produced by dairy cows to maintain a desirable indoor temperature. [27] Heat stress in cows can affect their health, milk productivity and reproduction. [22] A temperature of 8 o C to 10 o C in the barn is desired. Ventilation is also needed in the winter to remove moisture and odor in additional to removing heat produced by cows. [27] Supplementary heating may be required in winter to assist ventilation by reducing humidity and allowing more moisture to be removed by ventilation. The Brown farm uses one 61cm 0.37kW (24-inch 0.5 hp) and three 91cm 0.37kW (36- inch 0.5 hp) circulating fans and one 122cm 0.75kW (48-inch 1 hp) fan for 24 hours a day for 120 days of the year. 4.6 Space Heating The heating requirement depends on the local climate of the barn, the number of cows, ventilation and insulation. [23] The energy assessment did not indicate a need for space heating for the Brown farm located in New York. The weather pattern of Waterloo, Ontario was studied to estimate the heating demand requirement. 17

27 4.7 Other Equipment The Brown farm operates two 1000 W stock waterer for 8 hours a day for 150 days a year. A 1000W engine block heater is also used for 4 hours per day at night. There are also miscellaneous plug loads which are not accounted for in calculating the electrical demand. 18

28 5.0 Calculating Heat and Electrical Demand The diesel engine powered cogeneration system should be sized according to the farm s electrical demand or thermal demand. When the system can only provide part of the requirement, additional energy needs to be purchased. Inadequately sized systems can result in overloaded circuits and fire hazards. 5.1 Electrical Demand The peak load and average load calculations are shown in Figure 5 and described below. The operating load (name plate wattage) of each equipment was obtained from the energy assessment as described in Chapter 4. Annual energy use of the equipment (kwh) is calculated by multiplying the operating load (kw) to the number of hours the equipment is used in a year. All equipment is assumed to be in operation for 365 days a year, unless otherwise noted in the assessment. Efficiency of the equipment was assumed to be 90% if no information is available. Lighting loads have an efficiency of 100% because they are resistance loads. Calculations were verified with the figures from the Brown Farm energy assessment and data from Ensave [11][13Error! Reference source not found.]. The average load for the farm is calculated by dividing the total annual energy use of all equipment (kwh) by the number of hours in a year. The average electrical load for the Brown Farm is calculated to be kw. 19

29 The peak load is the highest sum of the operating loads of the equipment likely to be used simultaneously. Peak periods for the Brown Farm and all dairy farms occur during the milking cycle. It is assumed that all milking equipment, lighting, ventilation is operating during this period. The peak load for the Brown Farm is kw. The diesel engine generator was selected such that its prime rating is approximately the same as the average load. In practice, the startup load, which can be estimated as four times as the operating load, should be used in peak load calculation. Startup load figures were not available from the energy assessment. 5.2 Space Heating Demand Waterloo, Ontario was chosen for the purpose of calculating space heating demand requirements of the farm. Waterloo, Ontario currently has 279 licensed milk production units. [24] Weather data, including daily maximum, minimum and average temperatures for each month are provided by Canadian Climate Normals, a collection of weather data from 1971 to 2000 (Appendix A). The Canadian Plan Service and the Ontario Ministry of Agriculture, Food and Rural Affairs identify three types of barns, cold barn, modified barn, and warm barn, depending on the type of insulation. A barn must have proper ventilation even in winter to remove moisture and reduce condensation. In addition, a comfortable temperature for both cows and workers must be maintained. The ideal ambient temperature for a dairy cow is between 5 to 10 o C. [25] 20

30 Using construction plans developed by Canada Plan Services, a free-stall barn and milking center was designed for a farm of 110 cows. The free-stall barn provides housing for cows. The milking center consists of a milk house to store the equipment for cooling milk and a milk parlour, where milking takes place. [26]. No supplement heating is required in a well-insulated barn until the ambient temperature falls below -20 o C. Maternity and calf areas will require extra heating. The milk parlour and milk house also need supplement heating to reduce humidity and keep milk above freezing temperatures. [26]. The building dimensions and R value of the construction material, if provided, were used in the thermal requirement calculation. The Degree-Day method was used initially to calculate the thermal requirement. An assumption was made that the free-stall barn, milking centre had walls of insulation of RSI-value 8.5. A more detailed method outlined in Environment Control for Confinement Livestock Housing by Purdue University Cooperative Extension Service provides a more accurate way of calculating the amount of supplementary heat required. It includes other heat losses, (for example, heat loss due to ventilation) and heat gain, (for example, heat produced from the cows). This method was used to calculate the supplement heat requirement based on the input of outdoor temperature. It was assumed that the free-stall barn, as mentioned above, would not require supplementary heating. Supplementary heating would only be required in the milking 21

31 centre, which includes the milk house and milking parlour. Supplementary heating will be provided using floor heating, further discussed in Chapter Heating Requirement for the Milking Centre The Herringbone milking center with single alley return way (Plan M-2501) provided by Canada Plan Services is designed for a double 8 stall herring bone milking parlour complete with milk room, office, mechanical equipment room and small washroom. The building is 7.2m x 18m with a wall height of 2.45m (if the ceiling is fastened to 38mm ceiling strapping). The ceiling has an insulation of RSI-4.9 and the walls RSI-3.5. The concrete foundation is well-insulated. [28] The optimum temperature suggested for a dairy cow is 10 o C [27][23], while for calves it is 21 o C. For the purpose of the simulation, the desired temperature of the barn will be 10 o C. Animals convert 25% to 40% of its feed energy into heat. Cows produce 944 W of heat when the surrounding temperature is 10 o C. The milking parlour has 8 milking units, Assuming all milking units are used during the milking cycle, the heat produced by 8 cows is equal to 7550W. The heat provided by the cows is considered a heat gain, and will reduce the amount of supplement heat required. However, for simulation purposes, the heat gain was not considered because cows were not in the milking center at all times. 22

32 The paper also explains the procedure in calculating ventilation rates for moisture control, odour control based on the moisture content the animal produces and the moisture content of the air. This number should vary between summer and winter. Since supplement heating is only required at temperatures below 10 o C, the ventilation rate for cold weather was used to calculate ventilation heat loss. The recommended ventilation rate of 0.23m 3 /min (8 cfm) for milking house and milking parlour was used. [27] A balance of heat gain and heat loss is required to maintain a constant indoor temperature. The total heat loss in the milking centre is the sum of the heat loss in the ceiling, walls, foundation, perimeter of the wall and through ventilation. A sample calculation is as follows. Temperature Difference: 10 o C inside -10 o C outside. Building Dimensions L = 18m W = 7.2m H = 2.45m Heat Loss: U * A * (T in T out ) Ceiling (RSI=4.9) U = 4.9hr *ft 2 * o F/ BTU * 2 o 1m * C / hr * ft * W F/ BTU o 1 U= W/m 2 o C ceiling W *(7.2m*18m)*(10 2 o m * C o C ( 10 o C)) 23

33 Q ceiling = W Walls (RSI=3.5) U = 3.5hr *ft 2 * o F/ BTU * o 1 C*m hr * ft 2 / W o * F/ BTU 1 U = W/m 2 * o C wall W * 2 * 2.45m * (7.2m 2 o m * C 18m) * (10 o C ( 10 o C)) Q wall = W Perimeter (RSI=1.23, assume concrete without perimeter insulation) U = 1.23hr *ft* o F / BTU * o hr *ft* C*m / W o F / BTU 1 U = W/m* o C perimeter 1.407W/m o C*2*(7.2m 18m)*(10 o C ( 10 o C)) Q perimeter = W Foundation (RSI = 5.03, assume concrete, lightweight, holes filled with vermiculite) U = 5.03hr *ft 2 * o F/ BTU * o 1 C* m hr * ft 2 / W o * F/ BTU 1 U = W/m 2 * o C Q foundation foundation W / m = W 2 o C * (7.2m *18m) * (10 o C ( 10 o C)) Ventilation Loss Recommended ventilation = 8cfm ventilation 18BTU 8cfm* *(50 3 o 1000ft F o F o 60min 1000W 14 F)* * hr BTU / hr 24

34 Q ventilation =91.16 W Supplement heat required: sup ple ceiling wall Q supple = W perimeter foundation ventilation This calculation suggests that W of heating needs to be provided to the milking centre to maintain an indoor temperature of 10 o C when the outside temperature is -10 o C. The milking centre is attached to the free-stall barn at the 7.2m *2.45m wall in the construction plan. For simplification, it was assumed the milking centre exists as a separate building and the free-stall barn has no effect on its temperature. The slope of the ceiling was not taken into consideration and assumed to have the area as the foundation. A similar calculation was performed using data for the free-stall barn. The free-stall barn would require greater heating demand than both diesel engine generators can provide. Therefore, it was assumed the free-stall barn is well-insulated and requires no supplement heating. Only the milking centre would require supplementary heating. 5.3 Hot Water Heating Demand A large amount of hot water is required at a high temperature for cleaning and sanitizing the milk equipment. It was assumed that hot water is required one hour after each milking cycle. (From 10:00 AM to 11:00 AM and 12:00 AM to 1:00 AM) 25

35 The amount of water required for the cleaning depends on the size of the milking equipment, such as the volume of the bulk tank and length of the milk lines. Information is not available specific to the equipment used by the Brown Farm to construct a usage profile that varies with time. However, it is known that the farm requires 1056 L of water to be heated daily in a 454 L tank. It was assumed that the water heater operates from 5:00 to 9:00 AM, and from 6:00PM to 11:00 PM. Water heating also occurs from 10:00 AM to 11:00 AM. The required water temperature in the tank is 60 o C. The water temperature for the 4 cleaning cycles ranges from to 43 o C to 76 o C. For the simulation, a desired water temperature 75 o C was inputted during periods of the washing cycle. The total amount of water used for the pre-rinse, wash, and rinse cycle is assumed to be the full tank, 454L. It should be noted though, that in reality a water tank is not used to its full capacity. If the washing cycle occurs for one hour, the required water flow rate would be (454 L/ 60min) 7.6 L/min. Other uses of water occur some time during the day and do not require temperatures above 60 o C. These uses were not accounted for in the hot water demand as the water is available at the desired temperature in the tank. Water is drawn from the water tank when it is needed. 26

36 5.4 Demand Profiles Electrical demand profiles and a hot water profile were created for the Brown Farm as shown in Appendix B. A daily electrical demand profile was created for each season according to the equipment s operational characteristics described in Chapter 4. (Appendix B-1 to B-4) The electrical demand and floor heating demand varies with outdoor temperature as more ventilation or heat is needed to regulate the indoor temperature of the barn and milking centre. Although some equipment or appliances such as fans and lighting are only used during 1 or 2 months during a season, they were considered to be in operation for all 3 months in the seasonal demand profile. Figure 8 illustrates the electrical demand profile for all four seasons. Note that the lines are not illustrating loads in between the half-hour intervals, they are only used for illustration purposes. One temperature is used for each seasonal demand profile. Outdoor temperatures for Waterloo, Ontario were obtained from the Canada Climate Normals as shown in Appendix A. For Spring (March to May) and Autumn (September to November), the average daily temperature for the season was used. For Summer (June to August), the highest temperature for the season was used, and for Winter (December to February), the lowest temperature was used. Using the hottest temperature in the summer and the coldest temperature in winter gives a range of the performance capacity of the cogeneration system in extreme weather conditions. 27

37 One hot water demand profile was used for all seasons. (Appendix B-5) No data was available from the energy assessment regarding seasonal hot water use. Therefore, it was assumed that the amount of water needed for the milk equipment cleaning cycles, feeding and other uses do not vary greatly with outdoor temperatures. A seasonal analysis is appropriate at this preliminary stage in deciding the feasibility of the cogeneration system. For developing a detailed cost savings analysis and appropriate operation strategy of the system, hourly energy data is required. [6] 28

38 6.0 System Design After analyzing electrical and heating demands of the Brown Farm, a diesel engine powered cogeneration system was selected from commercially available products or created by choosing components to meet the requirements Most commercially available small-scale cogeneration systems are internal combustion engines driven by natural gas. A few companies make natural gas-based cogeneration system with the option of using fuel oil or diesel. SenerTec s product, Dachs, has an electrical output of 5.3kW and thermal output of 10.5kW and an overall efficiency of 90% using fuel oil. [10] Polar Power provides cogeneration systems running on natural gas but can be modified to use a diesel engine. It has an electrical and thermal capacity of 6kW and 8.78kW respectively. [3] EC Power has a small size diesel engine cogeneration system that can provide a thermal output of 24 kw and 17kW of electrical output. It has an overall efficiency of 85% [11] Many companies offer diesel engine and generators as a set package, without a heat recovery system. Cummins, Alturdyne, Caterpillar, Lister-Petter and Kubota provide a wide range of diesel engine generator sets with different power ratings. Due to the lack of commercially diesel engine powered cogenerations systems available. A theoretical cogeneration system was designed for the Brown Farm by selecting a diesel engine generator set and heat recovery components. 29

39 6.1 Overview A diesel engine cogeneration system was designed to provide the electrical demand, hot water heating and space heating needs for a small dairy farm, such as the Brown farm discussed in Chapter 4. The system was designed such that electrical demand was always satisfied, if the system could not supply all the hot water heating and space heating needs, additional energy needs to be purchased. The system uses two 14.4 kw diesel engine generators, two coolant-to-water heat exchanger and one exhaust-to-water heat exchanger. Figure 6 and Figure 7 illustrates the design and operating strategy of the diesel engine cogeneration system. Electrical demand is supplied by two diesel engine generators. Diesel Engine Generator 1, the primary generator, will be operating continuously. Diesel Engine Generator 2 will serve as the secondary generator when the electrical demand exceeds the generator s prime rating of 14.4kW. The benefit of having two diesel engine generators is that the secondary generator can serve as a back-up generator should the primary one fail or require maintenance. It is assumed the farm is connected to the electricity grid, and any additional requirements not provided by the diesel engine cogeneration system will be supplemented. Floor heating is achieved by pumping hot water through pipes embedded in concrete floors of the farm. Water is heated by using recovered heat rejected to the coolant from the engine jacket in a coolant-to-water heat exchanger. Only the coolant system from diesel engine 1 is attached to this coolant-to-water heat exchanger. A thermostat signals the pump to circulate water when the outside temperature falls below 10 o C. 30

40 Hot water heating is provided by a second coolant-to-water heat exchanger in line with diesel engine generator 2. Hot water demand on the dairy farm follows a regular pattern during the course of the day; controls can be programmed to automatically divert coolant flow to the heat exchanger. For hot water demands at 60 o C or lower, some or all of the coolant is diverted to the heat exchanger to heat water drawn from the cold supply. Heated water can be stored in a water tank until it is used. A blending valve in the system will mix cold water from water from the hot water tank, if water less than 60 o C is desired. When hot water at 60 o C or higher is needed, water is drawn from the tank and passed through the exhaust-to-water heat exchanger that is connected with diesel engine generator 1. The following sections describe each component in greater detail. 6.2 Diesel Engine Generator Base on the average electrical load of 13.44kW (Figure 5) and a peak load of 26.92kW. Two Cummins diesel generator set Model DNAE 60Hz with a prime rating of 14.4 kw were selected. Prime rating was used to select the generator set as it represents the output for unlimited running time. The extra capacity of the generator (28.8kW 26.92kW = 1.88kW) allows the accommodation of extra components to the system such as the pumps for floor heating, controls for the system. The engine used in the set is a Onan LPW4 naturally aspirated, liquid cooled engine with a constant rotation speed of 1800 rpm. The coolant for the engine was assumed to be 31

41 50/50 ethylene glycol. It was assumed the rated load is the full load for the engine and the data listed in the specification sheet were at the full load unless otherwise specified (Appendix C). The generator efficiency, or the ratio of electrical output to brake power of the engine, is 86% as shown in the calculation in (Appendix D-1). 6.3 Coolant-to-Water Heat Exchanger Liquid to liquid heat exchanger are widely available commercially. The following procedure was used to size the heat exchanger. At the rated load, the heat transfer to the coolant from the engine is kw. The initial temperature difference between the inlet water and inlet coolant (ITD) is (94.8 o C (coolant) 15 o C (water) = 79.8 o C. The heat transfer in W/ o C is calculated = W / 79.8 o C = 167 W/ o C. This is required at a coolant flow rate of 43.9 L/min. The required heat transfer and flow rate point is plotted on a heat transfer (W/ o C) vs. flow rate curve provided by the company. If the heat transfer curve is above the point at the required flow rate, the heat exchanger will exceed the required performance. The pressure drop of the heat exchanger at the required flow rate is noted from the pressure drop vs. flow rate graph. The total pressure drop, including the heat exchanger and pipelines, must not exceed the maximum coolant friction head of the engine of 9.7 kpa. 32

42 Heat exchangers can also be selected using online models provided by the company. Mueller suggested the following heat exchangers for coolant-to-water heat exchanger 1 (for floor heating) differing in different plate styles. [44] All heat exchangers listed uses 316 Stainless Steel for plates and C-20 Carbon Steel for frames. Coolant o C inlet and 90 o C outlet Water: o C. inlet and 55.7 o C outlet Heat transfer: kw Model 4G: 14 plates. Pressure drop: coolant side: 7.98 kpa, water side: 6.21 kpa Model 10G: 6 plates. Pressure drop: coolant side: 5.82 kpa, water side 7.35 kpa Model 405MHV: 4 plates. Pressure drop: coolant side: kpa, water side: kpa. The model was not able to provide any data for coolant-to-water heat exchanger 2 (for water heating). Other deciding factors in selecting a heat exchanger would include space and cost. For simulation purpose, it was assumed that the selected heat exchanger would provide the heat transfer required and operated within the pressure limitation set by the diesel engine manufacturer Space heating system The required supplement heat can be supplied in 4 different ways, overhead radiant heating, floor heat, unit or space heaters, and make-up air heaters. Unit or space heaters heat and recirculate the air, and make-up heaters heat incoming ventilation air. [27] 33

43 Floor heat is supplied either by electric resistance cable or hot water running through pipes embedded in concrete. Floor heating was chosen as the heating source for the dairy farm. The advantage of this system over other heating methods includes its ease of maintenance, avoided problems with dust and clogged air filters, higher efficiency, ability to provide uniform and rapid heating [29] Radiant heat, in general, is also beneficial to the well-being of humans and animals. Also, floors can retain heat for a long time due to its high thermal mass. [29] Floor heating also has disadvantages. It has high costs relative to other heating systems and it may not provide sufficient heating in the cold weather. [29] The basic floor heating system consists of a hot water heater or boiler, circulating pump, expansion tank, under-floor pipes, controls, valves. [29] The water gains heat at the boiler and is then pumped through pipes embedded in the floor in a closed loop. In the diesel engine cogeneration simulation, a coolant to water heat exchanger will act in place of a boiler to heat the water. The water flow rate and outlet fluid temperature of coolant-to-water heat exchanger must be selected to provide the desired level of heat output and allow for a temperature drop in the floor pipes while maintaining relatively uniform floor temperatures. [29] Floor pipe spacing will also affect the desired level of heat output. 34

44 It is assumed that the water flowing through the floor pipes is driven by a pump at a constant speed, regardless of the amount of supplementary heat required. A flow rate for the pump was chosen using the following equation *Qsup ple F [29] T fluid where F is the flow rate of water [L/min] Q supple is the supplementary heat required [kw] Tfluid is the temperature change of water from the inlet to outlet of the coolant to water heat exchanger [ o C]. The flow rate of the pump varies proportionally with the amount of supplementary heat required. For the extreme case of an outside temperature of -24 o C, if the desired temperature inside the barn is 10 o C, kw of supplement heat is required for the milking center (calculated using the method described in Section 5.2.1). In general, a change between the inlet and outlet fluid temperature of 5-8 o C of the floor heating system is desirable to maintain uniform floor temperature [29]. For a water temperature change of 8 o C, the flow rate is, F 14.33*Q T fluid sup ple F = 14.33* 19.46kW / 8 o C F= L/min A constant flow rate of 35 L/min is used for the floor heating system. The lowest temperature for winter in Waterloo according to the Climate Normal Average is -11 o C. (Appendix A), although an extreme temperature of o C has been recorded in

45 The chosen flow should provide the floor heating system with more flow than is required. One disadvantage, however, is inefficiency due to the wasted electrical energy required to operate the pump. The circulating pump selected should provide the above flow rate at the pressure loss of the entire system. Pressure loss should not exceed 60 kpa for most system. [29] The fluid temperature required for the specified floor heating output is calculated using data provided by Radiantec as shown in Appendix E. Other Considerations Using a pipe spacing of 12 (300mm), room of 7.2*18m will require m 2 / 0.3m = 432 m of total pipe length. Each loop has a maximum pipe length of 122m if 7/8 pipe is used.[30] Therefore 4 loops will be required. An expansion tank installed before the circulating pump accommodates the increased volume of heated water. It is usually 10% of the total system volume. [29] The fluid used in the water heating system may be ethylene glycol, water or other heating fluids. If water is used, de-mineralized or soft water, with corrosion inhibitors added to prevent scale build-up in pipes caused by hard water. This should not be a problem for floor heating if plastic pipes are used. [29] A back flow preventer is required on the water supply connection.. [29] 36

46 6.4 Exhaust-to-Water Heat Exchanger The high temperature of the exhaust allows great potential for heat recovery. However, material complications limit the inlet temperature of water used in a heat exchanger. The selection of a heat exchanger is based on the limits of the pressure drop (both sides of both fluids and the heat recovery requirements) [35] Pressure drop of the exhaust gas system which includes the exhaust piping, heat recovery unit, auxiliary silencer and tailpipe must not exceed the back pressure allowed by the engine manufacturer. [35] For the diesel engine generator selected, the maximum back pressure is 5.0kPa. High back pressure can lead to reduced engine capacity, loss of efficiencies and engine overheating [62] Water will condense on surfaces that are at a temperature below the water dewpoint temperature. Sulfur or hydrogen sulfur from the exhaust will react with water in air to form sulfuric acid. This may results in corrosion of the heat exchanger. To prevent condensation and corrosion, the metal surfaces of the heat exchanger must be kept above the applicable dewpoint. This requires the inlet temperature of the water to be above 72 o C (93 o C if the fuel contains sulfur or hydrogen sulfide ) [35]. Most exhaust heat exchangers are fabricated using stainless steel. Special corrosion resistant alloy can also be used to prevent this problem. The exhaust lines from diesel engine generator one is connected to the exhaust-to-water heat exchanger. When hot water is needed at above 60 o C, water is drawn from the hot 37

47 water tank and passed through the exhaust-to-heat exchanger. Several commercially available products are available. Bowman has a wide range of shell and tube heat exchangers that can reduce exhaust gas from 600 o C to 170 o C with an exhaust pressure drop of 2.4 to 3.0 kpa. The maximum working exhaust gas pressure and temperature is 50 kpa and 700 o C. The maximum working pressure and temperature for the water side is 400kPa and 110 o C. [35] Maxim Silencers offers the WHS which is a combination of a heat recovery unit and chamber type silencer designed primarily for reciprocating engines. [36] PolarPower Inc. s Model 30 Heat Exchanger is ideal for 5 to 20kW. It is made with 304 stainless steel and claims to have no limitation on water inlet temperature. [37] [38] Greg MacLeod of Exergy LLC remarked that an inlet temperature of o C for the exhaust gas is too high. The standard material for exhaust heat exchanger, stainless steel 316L, has a maximum temperature of 450 o C. A custom heat exchanger using a high nickel alloy is recommended. [39] Due to the lack of information available for the exhaust heat exchanger, it was assumed, for the purpose of simulation, that a custom heat exchanger would provide the heat transfer required and operated within the pressure limitation set by the diesel engine manufacturer. 38

48 7.0 Simulation A computer simulation was designed to evaluate the diesel engine cogeneration system s performance given the electrical and heating demands developed in Chapter 5. The simulation was programmed in Excel using Macros. Input parameters include Electrical demand [kw], Status of the hot water heater [ON/OFF], Outside temperature [ o C] Desired water outlet temperature [ o C] Desired water flow rate [L/min] After entering the required parameters and clicking the Calculate button, results are displaced on the Excel spreadsheet. The operating conditions such as flow rates, temperatures and energy output of each component in the system are displayed as shown in Figure 9. The system efficiency is also calculated and displayed. Density and specific heat capacity of the fluids used in the calculations are thermodynamic properties. Both properties are evaluated at the average temperature of the fluid at the inlet and outlet. Curve-fitted equations were developed for thermodynamic properties for water, air and 50/50 ethylene glycol as shown in Appendix G. 39

49 The simulation was programmed in accordance to the operation strategy in Figure 7 and the equations listed in Appendix H. 7.1 Diesel Engine Generators Assuming the power generated is equal to the user s input for electrical demand, engine characteristics such as BMEP, Torque, fuel consumption were calculated using the equations described in Appendix H. The following assumptions and observations were also made: The electrical output of the generator is equal to the user s input for electrical demand, where the maximum electrical output for one generator is 14.4kW and the maximum electrical output for both generators is 28.8 kw. Generator efficiency was calculated to be 86%. (Appendix D-1 ) A constant value is used for all loads assuming the variation with load is not more than 10%. The electrical output is proportional to the load of the engine, where percentage load is defined as the ratio between the engine torque and its full torque. This case is only true if the engine runs at a constant speed, as in a generator. Percentage load = T T engine fullload *100 The heat rejected to coolant and the heat rejected to surrounding is linearly proportional to the mass flow rate of fuel, which is a function of percentage load. m m fuel fuel_ fullload coolant coolant_ fullload and m m fuel fuel_ fullload surrounding surrounding _ fullload 40

50 Fuel consumption as a function of percentage load was curve-fitted based on engine specification data as shown in Appendix D-2. The density and lower heating value of diesel fuel is assumed to be constant at 850kg/m 3 and kj/kg respectively as diesel fuel is in liquid state. Volumetric efficiency was assumed to have a linear relationship with percentage load. The engine has 82% at full load and 88% at no load. This calculation was verified in Appendix D-3. The exhaust temperature varies with BMEP. An equation for the exhaust temperature as a function of BMEP was curve fitted as shown in Appendix D-4. The coolant flow rate is determined by an engine-driven pump. It is constant at 43.9 L/min The return temperature for coolant to the engine is constant at 90 0 C. The air flow rate through the radiator is a function of percentage load. A fan driving forced air through the radiator is driven by an alternator. 7.2 Coolant-to-Water Heat Exchanger 1 (for floor heating) The heat balance of the heat exchanger can be described as: hx1 _ coolant hx1 _ water m hx 1 _ coolant *Cp coolant *(T coolantin T coolantout ) m hx1 _ water *Cp water *(T waterin T waterout ) 41

51 The heat transfer and the flow rate of the coolant side is determined by the supplementary heat requirement and amount of heat rejected to coolant from diesel engine 1. There are 2 cases to be considered: Case 1: Qparlour (supplementary heat required) > Qcoolant1 The supplementary heat requirement exceeds the amount of heat rejected to coolant in engine 1. All coolant from engine 1 will be used in the heat exchanger. The desired indoor temperature cannot be reached. Additional heating sources are required. Case 2: Qparlour <= Qcoolant1 The supplementary heat requirement is less than the amount of heat rejected to coolant in engine 1. Some coolant from engine 1 will be used in the heat exchanger. The desired indoor temperature can be reached. The remaining coolant will be cooled by the radiator. The following assumptions and observations were made in the coolant-to-heat exchanger calculations The outlet temperature of coolant is constant at 90 o C. The inlet temperature of coolant is dependent on the operating conditions of the engine, regardless of the supplement heat requirement. It can be calculated as follows, Assuming all the heat was cooled by the radiator, T coolantin T coolantout m hx _ coolant coolant *Cp coolant. 42

52 The maximum volumetric flow rate of coolant is specified by the engine, 43.9 L/min. The maximum heat transfer of the heat exchanger is the heat rejected to coolant at full load, 13.33kW. The volumetric flow rate of water is constant at L/min as determined in Section The outlet temperature of water is dependent the supplementary heat required. A equation was developed using data from Radiantec. (Appendix E) 7.3 Coolant-to-Water Heat Exchanger 2 (for hot water heating) This heat exchanger is only used when the hot water input is TRUE and engine 2 is running. The heat transfer balance on the cooler is: hx2 _ coolant hx2 _ water m hx 2 _ coolant *Cp coolant *(T coolantin T coolantout ) m hx2 _ water *Cp water *(T waterin T waterout ) The heat transfer required to satisfy the user specified flow rate and water temperature is determined. There are two cases to be considered: Case 1: Qrequired > Qcoolant2 The amount of energy required to heat the water at the desired temperature and flow rate exceeds the heat rejected to the coolant by diesel engine generator 2. The maximum heat transfer for the heat exchanger equals to the heat rejected to the coolant. The specified flow rate will be provided at a reduced water outlet temperature. 43

53 Case 2: Qrequired <= Qcoolant2 The amount of energy required to heat the water at the desired temperature and flow rate is less than the heat rejected to the coolant by diesel engine generator 2. Both the flow rate and temperature requirement specified by the user can be satisfied. The remaining heat from the coolant is cooled by the engine s radiator. The following assumptions and observations are made: The outlet temperature of coolant is constant at 90 o C The inlet temperature of coolant is dependent on the operating conditions of the engine, regardless of the water heating requirement. It can be calculated as described above in 7.2. The maximum volumetric flow rate of coolant and maximum heat transfer is specified by the engine, at 43.9L/min and 13.33kW respectively. The inlet temperature of cold water supply is assumed to be constant at 15 o C regardless of outside temperature. The maximum outlet temperature of water is 60 o C. For water needs higher than 60 o C, water is drawn from the tank and passed through the exhaust heat exchanger. 7.4 Exhaust-to-Water Heat Exchanger This heat exchanger is connected the exhaust line of diesel engine 1. It is used when the user specified temperature is above 60 o C. Water is pumped from the hot water tank to the 44

54 heat exchanger. All exhaust gas is diverted to the heat exchanger. The heat transfer balance on the cooler is: hx _ exhasut hx _ water m hx _ exhaust *Cp exhaust *(T exhausttin T exhaustout ) m hx _ water *Cp water *(T waterin T waterout ) The heat transfer required to satisfy the user s specified flow rate and water temperature is determined, Qrequired. There are two cases to be considered: Case1: Qrequired> Qexhaust The heat required to heat the water to the desired flow rate and temperature The following assumptions and observations are made: The simulation does not check if there is water in the tank. The simulation does not keep record of the total amount of water pumped into the tank. The water tank is assumed to be well insulated and the inlet temperature of water is assumed to be constant at 60 o C. The temperature of the exhaust gas is determined by the operations of the engine as a function of BMEP. (Appendix D-4) The exhaust is assumed to have same specific heat as air evaluated at the same temperature. 45

55 7.5 Limitations The simulation of the diesel engine powered cogeneration system assumed many constant parameters to simplify calculations. In reality, many of the parameters are vary with time or engine operating conditions. Other general assumptions were: It is assumed there is minimal heat loss through convention or radiation as fluid travels from the engine to the heat exchangers. The heat rejected to the environment will not affect the indoor temperature of the milking centre. The simulation does not take into account transient effects of the sudden spikes demands of electrical energy or the time required for water to heat up. Start-up load was not considered of the electrical equipment as the information was not available. In practice, the start-up load should also be considered when sizing the generator. Fluid mechanics were not considered in the design of the system. Heat exchangers, pumps have pressure limitations and maximum flow requirements that need to be considered. 7.6 Testing Conditions Electrical demand profiles, hot water usage profiles and the outdoor temperatures averages developed in Section 5.4 were used for the input of the simulation. 46

56 In each demand or usage profile, a 24 hours period is divided into half hour intervals resulting in 48 test points per profile. There are 4 different profiles corresponding to the 4 seasons. This results in 192 test points in total. For each test point, the following data is required as input: Outdoor temperature. [ o C] Electrical requirement [kw] Hot water heater status (ON/OFF) Desired hot water flow rate [L/min] Desired hot water temperature [ o C] The output of each test point was evaluated for the following: Was the electrical requirement satisfied? (YES / NO/ Not Applicable) o If not, what is the generator output? Was the hot water demand for the water tank satisfied? (YES / NO / Not Applicable) o If not, what is the outlet water temperature? Was the hot water demand (T>60 o C) satisfied? (YES / NO / Not Applicable) o If not, what is the outlet water temperature? Was the space heating demand satisfied? (YES / NO / Not Applicable) o If not, what is the indoor temperature? The fuel consumption and system efficiency is also noted. 47

57 8.0 Analysis Each test point was evaluated for the criteria listed in Section 7.6. Results are shown in Appendix F. The following observations were made for each season. Spring The outdoor temperature for all spring test conditions was taken as 5.3 o C. Only a small amount of heating was required, thus the desired indoor temperature of 10 o C was achieved for all cases. The system has a range of efficiency from 25.7 to 46.8% with an average of 34.4%. Lowest efficiency occurred during 1 to 4:30 AM when only the only electrical demand of 1kW was required by the engine block heater. Highest efficiency was during the wash cycle, when hot water at 75 o C was required, the water heater was on, and space heating was required. During the period 3:00 6:00 PM, no electricity was required. During the milking cycle, when the electrical demand falls to 19.17kW, the coolant-to-water heat exchanger was unable to heat hot water to the desired temperature of 60 o C. Summer The outdoor temperature for all summer test cases was 25.9 o C. No heating was required. 48

58 The system has a range of efficiency from 17.5 to 44.6% with an average of 27.9%. Lowest efficiency occurred during the afternoon of 12:30 to 6:00 PM. Highest efficiency occurred during the wash cycle when most of the wasted heat was utilized. When the electrical demand falls to kw or lower, the desired temperature for the water heater could not be met. Autumn The outdoor temperature for all autumn test cases was 8.3 o C. Minimal heating was required. The 10 o C indoor temperature requirement was always satisfied. The system has a range of efficiency from 22.9 to 43.8% with an average of 30.8%. Lowest efficiency occurred during the afternoon. Highest efficiency occurred during the wash cycle when most of the wasted heat was utilized. The desired temperature for the water heater was met for all cases. In the night milking cycle, the 30.98kW electrical demand cannot be satisfied with both generators running kw was used for the simulation. Winter The outdoor temperature for all winter cases was -11 o C. In instances where the electrical demand was too low, there is insufficient amount of heat from the coolant to achieve the desired indoor temperature of 10 o C. These periods occurred between milking cycles. From 12:30PM to 6:00PM, the indoor temperature was -2.7 o C, and from 1:30 to 4:30AM, it was -1.6 o C. Additional sources of heating needs to be considered. 49

59 The system has the a range of efficiency from 41.6 to 54.9 % with an average of 48% In the night milking cycle, the 30.98kW electrical demand cannot be satisfied with both generators running. Figure 10 compare the system efficiency for all seasons in a 24 hour period. Most reciprocating engine powered cogeneration systems have a system efficiency of 85 90% and an electrical efficiency of 28%-39%. [3] The designed system has an average efficiency of % for the year. This indicates that the thermal efficiency has little contribution to the system efficiency. For all seasons, it was observed that the system is used most efficiently during the hour after the milking cycle. It makes the most use out of the wasted heat in heating water up to 75 o C, heating hot water in the tank, and providing space heating if needed. The exhaust-to-water heat exchanger is not used for other time during the day outside of the washing cycle, as hot water of high temperature is not required. This results in wasted heat. The system has the best performance in winter as there is a higher demand for space heating. There are several factors contributing to the low system efficiency. A high hot water demand only occurs immediately after the milking cycles. In other times, during the day, there is little use of the exhaust or coolant heat recovered if space heating is not required. Also, the secondary diesel engine generator operates only for 12 hours a day. (Figure 8) On average it operates at an electrical output of 9.52 kw, which is 66 % of its rated load. The generator has excess capacity most of the time during the afternoon and night as there is no electrical demand. 50

60 Figure 12 compares the hot water temperature from the system to the demand in a 24 hour period. The system is able to deliver water at 60 o C to the water tank except for a few instances in spring and summer. At these points, there was a lack of demand for electricity; hence there was insufficient amount of heat from the coolant for water heating. The water flow rate to the tank is set arbitrarily to 2L/min. This number is relatively low and may cause mechanical instability in the pump. If the flow rate was increased, then an outlet water temperature of 60 o C for the water tank cannot be satisfied. To operate at a higher flow rate, for example, 3L/min, the combined output of the generators has to be above 24 kw. Figure 11 illustrates the temperature of the milking centre in a 24 hour period for all seasons. In spring and autumn, the indoor temperature of the milking centre could be maintained at 10 o C. In the summer, heating was not required. In the winter, the electrical demand was too low in the afternoon and during the night to supply heating. The indoor temperature of the milking centre falls below 0 o C during these periods. 8.1 Recommendations Several recommendations is made to the system design or the operating strategy to improve its performance. 51

61 Hot water heating Instead of flowing cold water through the coolant-to-heat exchanger and into the hot water tank, water should be circulate through a close loop to heat a full tank of water. This was difficult to model in the simulation program, as the inlet water temperature of the coolant-to-water heat exchanger changes with time as the water in the tank heats up. If there are no material complications with the exhaust-to-water heat exchanger, it can be used to provide hot water heating. Both coolant-to-water heat exchangers can be used for floor heating to satisfy all space heating requirements. However, special design considerations and setups are needed to divert the correct amount of coolant back to each engine. Operation strategy The current operating strategy is known as load tracking [6] in which the diesel engine cogeneration system s output levels is determined by the farm s electrical requirements. As illustrated by Figure 8, the farm s electrical requirement falls below the prime rating of one generator, 14.4kW, for 12 hours in a day. This indicates the second diesel engine generator is idled half of the time. Other cogeneration operation strategy should be considered to improve the efficiency of the system. The baseloaded operating strategy may be considered if selling power back to the electric utility is a viable option. Both generators can run at their prime power rating all 52

62 the time to provide the farm s needs. Any surplus energy generated is sold to the electric utility. [6] Another strategy which can be considered is peak-shaving, in which the cogeneration system operates during limited hours of the day when there is a high electrical demand. There are two modes possible. The first mode consists of operating during the peak load hours defined by the utility, when electrical costs are the highest. The second mode consists of operating during the farm s peak hours. For example, the generator would only be used during the milking hours and 1 hour for the cleaning cycle. In both modes, the system can be reduced to one generator. However, heat recovery may not be cost effective [6], as the space heating requirement can no longer be satisfied at all times. Absorption Chiller Another major use of electricity for the farm is milk cooling. Milk has to be cooled rapidly to a low temperature to reduce bacteria count and maintain the quality of the milk before pick-up. At the Brown Farm, compressors operate for only 2.5 hours daily to cool the milk [13]. High insulation of the bulk tank keep the milk at the cool temperature until it is ready to be picked up. [13] Low pressure steam can be recovered using the exhaustto-water heat exchanger to drive an absorption chiller. The chiller would produced cool water that can be circulating in a closed loop in the bulk tank to provide milk cooling. A steam driven absorption chillers can reduce the operating costs of the compressors and condenser fans. Steam can be produced by running water to the exhaust-to-water heat exchanger. The compressors use 15,121 kwh and the condenser fans use 3,024 kwh 53

63 annually. This amounts to a potential saving of $2177 per year. Absorption chilling may be more beneficial to farms where milk is not picked up on a daily basis and requires longer cooling periods. 54

64 9.0 Economic Costs Costs are often the determining factor in whether a new technology or process is implemented despite its technical feasibility and environmental benefits. Cogeneration promises reduced costs with the more efficient use of energy. However, if capital costs are high and there is lack of demand for heating, switching from the power grid to on-site cogeneration may not be a cost-effective option. Costs analyses are used to decide whether the implementation of the on-site cogeneration is economically justified. [6] For this feasibility study, a simple cost analysis was performed to compare the economic benefits of cogeneration with its capital costs and operating costs. This analysis would be adequate for preliminary levels of decision making. A more detailed cost analysis would be required if the project was to be implemented. [6] A savings in operating costs and the simple payback method were calculated. The latter is defined as the total cost of project divided by savings for the first year of operation. The calculation represents the number of years it takes for the value of savings to equal the total required investment. [6] All figures are in American Dollars USD. Captial Cost of the System Engine generator set: $ 5000 each * 2 = $10,000 Heat recovery/rejection system: Coolant-to-water heat exchanger [45] 3000 each *2 = 6000 Exhaust-to-water heat exchanger [38] $1900 each * 1 = $

65 Total cost of equipment $17,900 Operating Costs without Cogeneration Energy usage (Calculated according to electrical demand profile) Spring kwh/day * 92 days = 28,658 kwh Summer kwh/day * 92 days = 30,332 kwh Autumn kwh/day * 91 days = 34,716 kwh Winter kwh/day * 90 days = 34,335 kwh Total energy usage for the year 128,041 kwh Average cost of electricity $0.12/kWh Total cost of electricity 128,041 kwh * $0.12/ kwh = $15,365 Operating Costs with Cogeneration Amount of fuel used: Spring L/day * 92 days =10,810L Summer L/day * 92 days = 11,509L Autumn L/day * 91 days = 12,676L Winter L/day * 90 days = 12,537L Total amount of fuel used: 47,532L Cost of diesel fuel ($1.5/gal) [4] $0.396/L Total cost of fuel 47, 532L * $0.396/L = $18,823 Savings Operating costs saved by using cogeneration $15,365 - $18,823 = $-3458 These calculations suggest that the use of a diesel engine cogeneration system with the current operating strategy at the Brown Farm would not lead to cost savings. Instead, the Brown Farm would have to pay $3458 more each year for the supply of diesel fuel. The number of payback years was not calculated because the savings is a negative value. The implementation will not cover the total cost of investment. 56

66 It should be noted that the capital cost is more than $17,900. The costs for piping, pumps, valves, controls and exhaust treatment system were not included. The cost of operating with cogeneration should also include the purchase of electricity or supplementary heating when the system cannot satisfy the needs. In this calculation, only the cost of fuel was considered, assuming that the system can satisfy all energy requirements. 57

67 10.0 Environmental Concerns The combustion process in diesel engines produce emissions, including NO x, SO z and particulate matter, contribute to air pollution and acid rain. Reducing emissions while optimizing efficiency and dealing with the corrosive nature of emissions are design challenges of the cogeneration systems. Strict environmental regulations make diesel engine cogeneration systems less attractive as a choice for cogeneration technology due to its higher sulphur oxides and nitrogen oxides emissions than other technologies. In efforts to reduce the environmental impacts of engine emissions, there are environmental laws governing particulate emissions for off-road uses of diesel engines and sulfur content in diesel fuels. In Canada, the Canadian Environmental Protection Agency has emission standards for diesel engines under the Off-Road Compression- Ignition Engine Emission Regulations. in compliance with the United States Environmental Protection Agency s rules for off-road diesel engines. [43] Maximum levels of CO, particulate matter and combined non-methane hydrocarbon (NMHC) and NO x emissions have been established for engine power ranges. [43] These levels were recently modified and are applicable to all engines manufactured after The Onan LPW4 Engine used in the diesel engine generator has a rated engine power of 16.7 kw and falls under the Tier 2 category. The exhaust emissions data from the engine is as follows, Component HC ( Total Unburned Hydrocarbons): g per kwh (1.64 g per HP-hour) 58

68 NO x (Oxides of Nitrogen as NO 2 ): CO (Carbon Monoxide) PM (Particulate Matter) g per kwh (12.60 g per HP-hour) g per kwh (3.13 g per HP-hour) g per kwh (0.66 g per HP-hour) CEPA Maximum Emissions Levels Components NMHC + NO x (non methane hydrocarbon and nitrogen oxides) CO (Carbon Monoxide) PM (Particulate Matter) 7.5 g per kwh 6.6 g per kwh 0.80 g per kwh The engine s emissions exceeds the maximum levels set specified by the CEPA in terms of the PM and NMHC + NO x. Cummins Model DNAE 60 Hz diesel generator set was designed to meet the levels under the previous EPA regulations. Recent changes to the EPA regulations that became effective in 2007, suggest that the selected diesel engine generator cannot be used for offroad applications, including on-site power generation. Another diesel engine generator set of similar capacity with significantly lower NO x emissions needs to be considered. Other alternatives include using cleaner diesel fuels, or adding an exhaust treatment system to the engine to reduce emissions. 59

69 11.0 Conclusion The purpose of this thesis was to study the feasibility of applying a diesel engine powered cogeneration system to a 110-cow farm in Waterloo, Ontario. The performance, economic cost and environmental benefits were considered. It was concluded that the adoption of a diesel engine powered cogeneration system would not be beneficial to the farm. The thermal and electrical demands were analyzed from an energy assessment conducted by EnSave on a farm of the same size. Weather conditions for Waterloo were used to estimate the space heating requirements of the site. A conceptual diesel engine powered cogeneration system was designed to meet the needs of the site based on the selection of components. The system s performance was evaluated using a simulation. The energetic analysis of the system s performance indicated that the system could supply the thermal and electrical demand most of the time. The system however operated at a very low efficiency. There was a lack of demand for hot water outside of the washing cycle. There was an insufficient amount of heat available to supply space heating in the winter during the afternoon and night as electrical demand was very low during nonmilking hours. It was suggested that a change to a peakload operating strategy or the use of an absorption chiller would improve efficiency. The economic analysis indicated the system was not economically viable. The implementation of the diesel engine cogeneration system for the Brown farm would result in the additional costs of $3458 per year for diesel fuel. 60

70 The environmental analysis indicated that recent changes to the CEPA regulation would not allow the use of the chosen diesel engine generator set. Other choices needed to be considered. For the reasons indicated above, the implementation the diesel engine cogeneration system on the 110 cow dairy farm was not recommended without significant changes to the system design or operating strategy. Diesel engine cogeneration may be more beneficial on dairy farms of larger scale where there is greater demand for electricity and heat. Further investigation is required to confirm this. It is believed, however, that renewable energy production for dairy farms is possible. Liquid nitrogen gas produced from cow manure through an anaerobic digester can be used to drive a generator to provide electricity for the farm. This technology greatly reduces the amount of methane released from animal waste and displaces green house gas emissions from fossil fuel power generation. [46] 61

71 12.0 References 1. ASHRAE Handbook HVAC Systems and Equipment. USA: ASHRAE, Inc; UNEP. Cogeneration Energy Technology Fact Sheet Onovwiona, H. I., Ugursal, V.I. Residential cogeneration systems: review of the current technology. Renewable & Sustainable Energy Reviews; 2006:10: Kenyon, Paul. Cummins Power Generation. Evaluating Cogeneration for your Facility. EvaluateCoGen.pdf 5. Aceves, Salvador, M. Martinex-Frias, Joel, and Reistad, Gordon M. Analysis of homogenous charge compression ignition engines for cogeneration application. Journal of Energy Resources Technology; 2006: 128: Orlando, Joseph A. Cogeneration Design Guide. USA: ASHRAE, Inc.; Petchers, Neil. Combine Heating, Cooling and Power Handbook: Technologies and Applications USA: The Fairmont Press; U.S. Department of Energy - Federal Energy Management Program. Integrated Systems; Khakbazan, Mohammad. Descriptive analysis of on-farm energy use in Canada. A report to Natural Resources Canada. Prepared for the Canadian Agricultural Energy End Use Data and Analysis Centre.; Knable, Dave. Mobile diesel generators help save Canadian dairy industry. EGSA Powerline Magazine; Diesel Progress Reviews. Fuel cells on the farm? Plug Power LPG fuel cell system providing heat and power at New York dairy farm; EnSave Energy Performance Inc. Dairy Development Energy Program Energy Audit Report 13. Schramm, Micheal. Personal communication. EnSave Energy Performance Inc. 14. Genesis Energy. Genesis Energy Dairy Savings; Biffa Plc. Mass balance studies. Agricultural waste Chapter4: Focus on enterprise energy Sandford, Scott. Energy conservation in agriculture: Refrigeration systems. University of Wisconsin-Extension;

72 17. Winfield, R.G. Heat recovery from milk cooling systems; Sandford, Scott. Energy conservation in agriculture: Heating water on dairy farms. University of Wisconsin-Extension; Cuthbertson Harold. Energy opportunities: Hot water, energy and the milking center; Seguin, Guy P.Eng. Personal Communication. Dairy Farmers of Ontario. 21. Wisconsin Public Service Corporation. In-line milk cooling for farms; Efficiency Maine. Giant ventilation fans improve animal health and save money Ontario Ministry of Agriculture Food and Rural Affairs Staff. Your future dairy barn: will it be cold, have a modified environment or warm? Dairy Farmers of Ontario. Dairy Statistical Handbook; Jones, Gerald M. and Charles C. Stallings, Reducing Heat Stress for Dairy Cows; Canada Plan Services. Dairy Cattle Housing and Equipment; Jones, Don D., Friday, William H. and DeForest, Sherwood F. Environment Control for Confinement Livestock Housing; html 28. Canada Plan Service. Herringbone Milking Center (Single Return Alley) Leaflet and Plan.; Canada Plan Service. Hot Water Heating Radianttec. Design and Construction Suggestion Manual; National Food and Energy Council. Water Heating for Production Agriculture Norris, Brenda. Checking temperatures to stay out of hot water Gamroth, Mike. Four Basics of Cleaning. Western Dairy News;

73 34. State of Michigan. CIP Cleaning Guidelines Maxim Silencers. Heat Recovery Application Manual Bowman International Ltd. Exhaust Gas Heat Exchangers Polar Power Inc. Heat Exchanger Model Sams, Adams. Personal Communication. Polar Power Inc. 39. MacLeod, Greg. Personal Communication. Exergy LLC. 40. Yunus Çengel, Micheal Boles. Heat and Mass Transfer: A Practical Approach. McGraw- Hill; Engineering Tool Box. Water Thermal Properites Engineering Tool Box. Ethylene Glycol Heat Transfer Fluid CEPA Environmental Agency. Off-Road Compression-Ignition Emission Regulations; Mueller. Accu-Therm Plate Heat Exchangers; fm 45. McMaster Carr Central Vermont Public Service Cow Power. Why Farm Generation

74 13.0 Figures and Tables Figure 1: Conceptual diagram comparing the efficiency and losses of cogeneration and the conventional system. [8] Figure 2: Energy consumption by farm type in Ontario in 1997 (%) [9] 65

75 Figure 3: Energy consumption by energy type in Ontario dairy farms in 1997 (%) [9] Electricity use on the Brown Dairy Farm Water Heating 18% Engine Block 1% Ventilation 5% Lighting 25% Other 6% Milking 35% Stock Watering 1% Milk Cooling 9% Milking Stock Watering Milk Cooling Lighting Water Heating Ventilation Engine Block Other Figure 4: Graph showing applications and percentage of total electricity use on the Brown Farm 66

76 Figure 5: Electrical requirement calculation for the Brown Farm 67

77 Figure 6: Conceptual diagram of the diesel engine powered cogeneration system 68

78 Figure 7: Operation flow chart of diesel engine cogeneration system 69

79 Figure 8: Electrical demand vs. time 70

80 Figure 9: Graphical layout of the simulation program 71

81 Figure 10: System efficiency vs. time 72

82 Figure 11: Indoor temperature of milking centre vs. time 73

83 Figure 12: Water temperature (to end use) vs. time 74

84 Appendix A - Temperature Data for Waterloo, Ontario 75

85 Appendix B-1 - Brown Farm Electrical Demand Profile - Spring 76

86 Appendix B-2 - Brown Farm Electrical Demand Profile - Summer 77

87 Appendix B-3 - Brown Farm Electrical DemandProfile - Autumn 78

88 Appendix B-4 - Brown Farm Electrical Demand Profile - Winter 79

89 Appendix B-5 Brown Farm Hot Water Demand ** Highlighted regions indicate when diesel engine generator 2 is operating 80

90 Appendix C: Specification Data for Cummins Diesel Generator Set Model DNAE 60Hz Diesel Generator Set Model DNAE 60 Hz 16.0 kw, 20.0 kva Standby 14.4 kw, 18.0 kva Prime Base Engine Onan LPW4, naturally aspirated, diesel-fueled Displacement 1.9L Rated Speed 1800rpm Cooling Fan Load [kw] 0.2 Coolant Flow Rate [L/min] 43.9 Heat Rejection to Coolant [MJ/min] 0.8 Heat Rejection to Room [MJ/min] 0.3 Maximum Coolant Friction Head [kpa] 9.7 Maximum Coolant Static Head [m] 3.7 Air Combustion Air [m 3 /min] 1.4 Alternator Cooling Air [m 3 /min] 5.0 Radiator Cooling Air [m 3 /min] 62.3 Fuel Consumption Load ¼ 1/2 3/4 Full L/hr Power Output BMEP at Rated Load [kpa] Bore [mm] 85.9 Stroke [mm] 80.0 Piston Speed [m/s] 4.8 Compression Ratio 18.5:1 Exhaust Exhaust Flow at Rated Load [m 3 /min] 4.0 Exhaust Temperature [ o C] Max. Back Pressure [kpa]

91 Appendix D-1 - Generator Efficiency Calculation Torque at full load T 3 BMEP *Vd 1m 1N / m * * 2 *n 1000L 1Pa r Pa * kpa where BMEP is the brake mean effective pressure [kpa] n r is the number of crank shaft revolutions per power stroke = 2 Vd is the engine displacement [L] T is the torque [N*m] T kPa *1.9L 1m 1N / m * * 2 * L 1Pa Pa * kpa T = Nm Brake power at full load BP 2 1min N *T * * revolution 60s 1J * 1Nm 1W * 1J / s 1kW 1000W where BP is the brake power of the engine [kw] N is the engine speed [rpm] T is the torque [N*m] BP 2 1min 1800*88.62Nm* * revolution 60s 1J * 1Nm 1W * 1J / s 1kW 1000W BP = 16.7 kw Generator efficiency Gen1 Gen1 Gen 1 P gen1 BP 14.4kW 16.7kW 0.86 Generator efficiency varies according to load. Assuming this variation is not more than 10%, 1 Gen is used for all loads. 82

92 Appendix D-2 - Fuel Consumption as a Function of Engine Load The volumetric flow rate of fuel is a function of load. Data points from the specification sheet was used to curve fit an equation as shown below. Fuel Consumption Data for Diesel Engine Generator Set Model DNAE 60 Hz Fuel Consumption Load ¼ 1/2 3/4 Full L/hr Fuel consumption = *(percentload) [L/hr] The fuel consumption is not a linear relationship. At no load, the fuel consumption should equal to 0. However, this is not the case. This indicates inefficiency in the engine. 83

93 Volumetric Efficiency MIE496Y1Y-Thesis: Diesel Engine Powered Cogeneration for a Dairy Farm Appendix D-3 - Volumetric efficiency as a function of BMEP Theoretical air flow rate = V * N 2 3 1m * 1000 L where V is the engine displacement [L] N is the engine speed [rpm] At full load Theoretical inlet air flow rate = m revolution *1800 min 3 s 1 * 2 Theoretical inlet air flow rate = 1.71 m 3 /min Actual inlet air flow rate = 1.4m 3 /min Volumetric efficiency at full load v = actual inlet air flow rate / theoretical inlet air flow rate v = 1.4m 3 /min / 1.71 m 3 /min v = Typically an engine has 88% volumetric efficiency at no load and 82% volumetric efficiency at full load. The volumetric efficiency at no load for this engine is assumed to be 88%. A linear relationship is approximated using a linear trendline on the graph of BMEP, brake mean effective pressure. v versus At full load, BMEP = kpa. At no load, BMEP = 0kPa Volumetric Efficiency vs. BMEP for Diesel Engine Model DNAE 60Hz v = (BMEP) BMEP (kpa) Volumetric efficiency = * (BMEP)

94 Appendix D-4 - Exhaust outlet temperature as a function of BMEP Based on Figure from the book, Internal Combustion Engine Fundamentals by John B. Heywood, the exhaust temperature can be predicted based on BMEP. The curve in Figure is shifted such that the BMEP at full load (586.1kPa) and exhaust temperature at full load (548.9 o C) lies on the curve. Data from Figure BMEP (kpa) Exhaust temperature ( o C) For Diesel Engine Model DNAE 60Hz at full load. BMEP = kpa and the temperature of the exhaust gas is o C T_exhaust = ( *(BMEP) *(BMEP) 2 ) ( ) 85

95 Appendix E - Fluid Temperature for Floor Heating As a Function of Supplementary Heat Required Radianttec provided data for the required fluid temperature in floor heating corresponding to heat output for floor heating. [30] Data from graph Fluid Temp. [ o C] Heat output [W/m 2 ] Heat Output = *(T fluid ) [W/m 2 ] 86

96 Appendix F-1 Simulation Results for Spring 87

97 Appendix F-2 Simulation Results for Summer 88

98 Appendix F-3 Simulation Results for Autumn 89

99 Appendix F-4 Simulation Results for Winter 90

100 Appendix G-1 - Thermodynamic Properties Specific Heat Capacity of Air Curve-fitted using data from [41]. Applicable Range: 0 o C 727 o C 91

101 Appendix G-2 - Thermodynamic Properties Specific Heat Capacity of 50/50 Ethlyene Glycol Curve-fitted using data from [42]. Applicable Range: 4.4 o C 93.3 o C 92

102 Appendix G-3 - Thermodynamic Properties Specific Heat Capacity of Water Curve-fitted using data from [41]. Applicable Range: 0.01 o C 100 o C 93

103 Appendix G-4 - Thermodynamic Properties Density of Air Curve-fitted using data from [40Error! Reference source not found.]. Applicable Range: 0 o C 2000 o C 94

104 Appendix G-5 - Thermodynamic Properties Density of 50/50 Ethylene Glycol Curve-fitted using data from [42]. Applicable Range: 4.4 o C 93.3 o C 95

105 Appendix G-6 - Thermodynamic Properties - Density of Water Curve-fitted using data from [41]. Applicable Range: 0.01 o C 100 o C 96