ASHRAE AEDG K-12K Why Geothermal HVAC Systems Fill The Bill Kirk Mescher, PE Education Wxá zç Performance Innovation Experience ENGINEERING Bright Solutions in Engineering P PE 1 Simply Efficient 1
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AEDG Components Problem Identification Goal Setting- Overall SYSTEM Efficiency Building envelope Systems Lighting and Power Operation Service Water heating Verification Training Operation 4
Goal Setting 5
DOE Climatic Zones 6
Determining an Energy Budget EPA-Energy Budget Software Developed By Stephen Kavanaugh, Phd. 7
Where is the energy used? Source: ASHRAE AEDG K-12 2008 8
Compliance Responsibilities 9
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Prescriptive Approach 11
System Choices 12
The Goal- Provide an effective efficient engineering solution to the client. Identifying the problem Evaluate System Load Components Identify Possible system solutions Design an effective efficient engineering solution Renewables System Complexity System Cost 13
Load Identification What are the primary components of the HVAC load? Roof Wall Fenestration Ventilation Occupants Internal Loads 14
Cooling Load Components Load Identification Ventilation Represents 30-40% of Load Envelope People Ventilation Power Solar Lights Solar Loads Wall transmission Roof transmission Glass transmission Door transmission Floor Transmission Lighting Power People 10% Safety Ventilation Fans Conduction/ envelope represents <20% of the system load 15
Identifying the Big Targets? 50% 16
Enthalpy Energy Recovery 17
Energy Recovery: The Real Story 5 15 25 Enthalpy - BTU per Pound Dry Air 35 Outdoor air conditions to HVAC system without energy recovery Outdoor Air conditions to HVAC System with Total Energy Recovery Preconditioning 120 (TERS) 100 80 60 40 20 Humidity Ratio - Grains of Moisture 0 20 40 60 80 100 Dry Bulb Temperature - Degree F 18
Load Results Total Transmission losses- 118,000 Btuh Solar Load- 57,000 Btuh Ventilation Load (2700 CFM) 117,000 Btuh Energy Savings Potential for 75% effective ERV 88,000 BTUH 19
This Means? Building transmission losses are dictated by envelope configuration and materials. Building internal heat gains are controlled by lighting and use of the building. System Energy use is dictated by efficiency- (system selection) Simulation shows that the Building EER for the cooling system is 13.5 When energy recovery is taken into account, Building EER raises to 14.3 System EER is improved by 6% 20
Want to control Humidity?? 21
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What does this mean for the architect? Envelope trade offs are not allowed. The base design must comply with Standard 90.1. To gain building efficiency- The base building must exceed envelope requirements Control of lighting and internal heat producing appliances is as important as a good envelope Mechanical Engineer Must select efficient systems which control Ventilation Control High mechanical efficiency Good space control. 23
Heat pump / Unitary approach When Speaking of water to air heat pumps a few questions should be considered during design. 1- Do these systems require constant temperature water? 2- Do these systems require constant flow? 3- What is their static pressure capacity? 4- Should I use VAV distribution with them? 24
A High Efficiency System Provide a demand centered heating, cooling and ventilation system Simplified System Design Simple maintenance and operator interface Low first cost 25
Components of System efficiency Fan power Pump Power Chilling equipment power Heating Equipment energy Duct sizing Pipe sizing Filtration Selection Maintenance 26
Pumping Power Rather than looking at improved equipment efficiency look at equipment loads. 27
System Efficiency Killers Poor Hydronic Design High pump horse powers Control malfunction / poor design Poor Duct Design Improper filter selection and filter maintenance The moose on the loose outside air control. 28
What is next? What % of building load is conduction? What % of building load is Occupancy Driven? Can Mechanical systems be designed that Are occupancy driven and control humidity with occupancy? Are properly sized to meet Unoccupied loads? 29
Getting Started with Ground Source References ASHRAE Commercial Geothermal System design Manual Rafferty and Kavanaugh ASHRAE HVAC Simplified- Kavanaugh GCHPCALC- Loop sizing program Steve Kavanaugh IGSHPA- Various articles 30
A Few Ground Rules Central Pumping is a Parasitic load NO MORE THAN 5HP/100 tons of cooling Loops spacing must be kept 20 on centers Thermally enhanced grout which is pumped into the BOTTOM of the heat exchanger (Bentonite( has a TC of.3) Conduct Test Bore and Thermal Conductivity Test in the DESIGN phase of the project Use Design Conditions of 85ºF F and 45ºF Keep it simple, Avoid Buzzers and Bells. 31
Ground Source Systems Can have Higher first costs Budget Considerations Well Drilling 2000-3000 $/ton of cooling Compressor noise must be evaluated Must be Simply implemented to provide superior energy efficiency. VAV systems add residual minimum static pressure to the air distribution systems. Some zones may require reheat to maintain conditions during minimum flow. Do we need to discuss multi zone applications? Simultaneous heating and cooling during shoulder seasons. 32
Why Simply Designed? Basically its $ Boiler and tower plants 1100-1800 1800 $/ton Well Drilling- 2000-3000 $/ton Annual Energy savings 175-250 $/ton Payback on boiler plant 4-74 7 years, without regard for maintenance costs. Complexity adds $ but does not add VALUE 33
Typical Complex Additions Variable speed pumping systems Motorized valves at each unit DDC control- 6-12 points per unit Variable Volume Boxes with hot water reheat 34
Maintenance Costs - ASHRAE Various HVAC Systems Maintenance Costs in 2004 Dollars ($/ft2-yr) Age of System (Years) 0 2 5 10 20 GSHP (WLHP less Cooling Tower)* $ 0.208 $ 0.215 $ 0.226 $ 0.243 $ 0.277 WLHP $ 0.360 $ 0.367 $ 0.378 $ 0.395 $ 0.429 DX-Cooling/Electric Heating $ 0.382 $ 0.388 $ 0.399 $ 0.416 $ 0.450 2-Pipe Fan Coil w/ CI Boiler & Recip Chiller $ 0.523 $ 0.530 $ 0.541 $ 0.558 $ 0.592 VAV w/ Firetube Boiler & Recip Chiller $ 0.634 $ 0.641 $ 0.651 $ 0.668 $ 0.703 4-Pipe Fan Coil w/ CI Boiler & Recip Chiller $ 0.686 $ 0.693 $ 0.703 $ 0.720 $ 0.755 * Cooling Tower Reduction Estimate not in ASHRAE Chapter Original work in 1983 dollars, here inflated to 2004 dollars using US Dept of Commerce CPI rate of 1.90 ASHRAE 1995 Applications Handbook, Chapter 33, Table 4 Based upon analysis by Dohrmann and Alereza (1986) Costs are from office buildings only 35
Geothermal Design (the bucket theory) Flow into the bucket = Heat of rejection from Heat pumps Bucket volume = Short term thermal Capacity of the well field Temperature rise Level = Temperature fall Leak out of the bucket = Thermal capacity of the well field 36
What Are Geothermal Systems Cooling Season HVAC System with Recycled Energy Heating Season Geothermal Well Field Thermal Storage Thermal Conductivity 37
Hybrid Systems Beyond the scope of this presentation but: Hybrid systems offer a way to balance the energy load on a well field. In cooling dominated climates, a supplemental fluid cooler would be necessary to put a well field in balance. The heating load would be much smaller and the well field could be designed to meet the heating requirement. 38
Thermal Conductivity Testing 90 80 70 y = 5.1007Ln(x) + 64.27 R 2 = 0.9806 60 50 40 GPM temp in temp out average Temp Log. (average Temp) 30 20 10 0 0 5 10 15 20 25 30 35 40 45 50 Time Period Slope Average He (Btu/hr-ft) at Input (W/ft) Thermal Conductivity (Btu/hr-ft- F) 10 44 4.3 72.5 21.25 1.34 39
The Conventional Way PD VFD 12ºF T T T M M M System flow is designed to provide 12ºF at the loop field. 40
The Solution Geothermal heat pumps Simplified piping design Thermostat operator interface Occupied and Unoccupied operational modes MERV 6 to 10 filtration Lower classroom noise levels over previous unit ventilation systems Space by Space demand oriented system 41
Well Field Sizing Thermal Conductivity testing provides essential information for the sizing of well field Energy Simulations which indicate the Pulses of energy to the well field are essential to field design Test bore is essential to describe the drilling conditions and methods to contractors Maximum Heat exchanger Depth-500 ft. Remember- the ground is a heat sink and a heat source without proper energy inputs the heat sink will be oversized or undersized. Continuous operation of poorly designed pumps represent a significant load on the well field (cooling load). 42
Sample Well Field Once it s in the ground, you can add to it but you can t stretch the loops apart. HDPE SDR 11 UNI-LOOP 20 MIN Total Field Pressure Loss 20 H20 Thermally enhanced grout 43
Well Field Don ts Don t use vaults Don t require cross trenching Always use reverse return or close headers Don t use Pure Bentonite Grout Put wells any closer than 20 OC. PVC or Copper Bentonite Grout 44
Improving System Efficiency A well designed unitary approach fills the bill For short run, low pressure loss air distribution. 45
Is variable frequency performance linear? Does inverter efficiency remain at a constant 90+% efficiency over the range of control? Is the additional complexity of Inverter logic worth it? Due to Static pressure control do we ever gain on system Efficiency? Is there another way? 46
Variable Frequency Drive Performance INVERTER EFFICIENCY INPUT EFFICEINCY 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 1 5 10 25 100 0.1 0 0 10 20 30 40 50 60 70 80 90 100 LOAD Source: ASHRAE Research NY 08-044 Dr. Sally McInerny 47
Parallel Pump Curve Parallel pump operating point 3.1 HP (3.8 HP/100 tons) Individual pump operating point 1.75HP (2.1 HP/100 tons) Single pump and Parallel pump operation allows for greatly reduced pump horsepower usage during normal operation. No speed control is required. 200 gpm @ 40 Parallel Pumps 165 gpm @27 Single pump 48
One Pipe System Advantages Primary pumps can be sized to match block load instead of equipment flow requirements. System energy usage is directly connected to system load and equipment demand without variable flow controls. Low primary flow system head Reduced piping length (Lower first cost) Reduced piping system complexity P PE 1 Single Pipe Technology Simply Efficient 49
Normal Schools Renovation Project Requirements Provide space cooling at no additional operating cost to the Owner vs. heating only application. Individual classroom temperature control Individual classroom ventilation control Easily maintained systems NO DDC control Comply with ASHRAE and IBC standards Project Budget $16.00 - $18.00/ ft^2 $ $ $ $ 50
Initial Condition 51
Existing System Room mounted heating only unit ventilators Excessive fan noise Previous piping system repair replaced under floor system with in room mounted distribution piping 52
3 different mechanical rooms and boiler systems to correspond to building physical requirements. 53
New System New room by room vertical unit ventilators Quiet design Setback thermostats, integrated with lighting. Individual ventilation dampers 54
System Design Pumping strategy Parallel Primary Pumping based on thermal demand Primary Circulation pumps designed for 12ºF, when considering building block load. Unit by unit constant volume Room Temperature control Thermostat Control (space by space) Setback Interlocked with Lighting Building Diversity Piping system offers space by space load diversity 55
Mechanical / Electrical Systems Systems cannot impede learning New designs must Minimize mechanical system noise Provide Proper Temperature and Humidity Control Exhibit Poor Humidity Control Control Particulate dispersion through the space Provide appropriate ventilation/ oxygenation Be energy efficient Must be adaptable to the changing educational environment Education Wxá zç Performance Innovation Experience 56
Oakdale School- Normal Illinois System results Oakdale Energy Cost Oakdale Energy Use $0.0600 800,000.0 700,000.0 600,000.0 Total energy budget Initial-59 kbtu/ft^2/yr As renovated- 04-05 05-06 28 kbtu/ft^2/yr 06-07 $/kbtu $0.0500 $0.0400 $0.0300 $0.0200 04-05 05-06 06-07 07-08 07-08 $0.0100 500,000.0 Energy ( Kbtu) 400,000.0 300,000.0 $- Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month Comparison 04-05 to 06-07 200,000.0 100,000.0 0.0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month Energy Usage 37.3% Energy $ - 77% 206% increase in $/kbtuh 57
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Repeatable Results Oakdale Energy Use Glenn Energy Usage 800,000.0 700,000.0 Oakdale School Energy usage 28.1 KBTU/sq ft 400,000.0 350,000.0 Glenn School Energy usage 27.9 KBTU/sq ft 600,000.0 300,000.0 E n e r g y ( K b t u ) 500,000.0 400,000.0 04-05 05-06 06-07 07-08 Ene r g y ( K b t u ) 250,000.0 200,000.0 04-05 05-06 06-07 07-08 300,000.0 150,000.0 200,000.0 100,000.0 100,000.0 50,000.0 0.0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month 0.0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month Base electrical usage Carbon Equivalent Savings 510 tons/year 59
88 Carbon Equivalent Savings 510 Tons per Year 60
AEDG Results 54.4 kbtu/ft^2-yr 61
AEDG Results 59.8 kbtu/ft^2-yr 62
Conclusions Geothermal solutions offer low first cost solutions to energy efficiency. Using a system where energy is recycled will result in substantial al primary source energy savings. It does not take sophisticated control systems to provide superior comfort and energy efficiency Control of lighting and plug loads represents a MAJOR area for system load rightsizing. Ventilation, everyone s s whipping boy, presents an opportunity for space humidity control if properly managed. Apply sound thermodynamics and system design principals before falling on the control sword. An improperly designed system will never be fixed with controls. 63
The Future Decoupling Humidity and Temperature Control Energy recovery ventilation dehumidifier 15 cfm per person/.33 cfm/sq. ft./ 24 grains G Active Chilled Beams 64
Questions? 65
Out of the Box Way (distributed primary secondary system) S1 12ºF S2 One pipe configuration allows primary pumps to be sized for block cooling and heating loads TC System flow is designed to provide 12ºF at the loop field. During part load, one primary circulating pump may be used Reducing system horsepower consumption significantly 66