Efficient Use of Natural Gas Energy in Cogeneration in Households

Transcription

1 /cons Efficient Use of Natural Gas Energy in Cogeneration in Houseolds Ināra Laube 1, Ilmārs Bode 2, Ivars Platais 3, 1-3 Institute of Heat, Gas and Water Tecnology, Riga Tecnical University Abstract. In order to save primary energy resources, te member states of te European Union are implementing te required measures for using alternative energy. Tere are various potential routes to zero carbon ousing, but te most practical one is communal and ouseold microgeneration. Microgeneration produces eat and even electricity for domestic ouseolds. By te year 2050 micro-cogeneration systems could provide 30 40% of te electricity demand in Great Britain. In Latvia, te consumption by ouseolds accounts for 38% of te total energy consumption. 87% of te total consumption of energy resources is used for eating ouses and producing ot water; 13% (electricity) is used for operating ouseold devices and ligting. Te operating ours of a ouseold eating unit are equal to approximately ours per year; if a micro cogeneration unit wit te electrical capacity 1 3 kw is installed, it can cover te self-consumption of an average ouseold. Te annual electricity generation can amount to kw. Keywords: microcogeneration, energy efficiency and savings I. INTRODUCTION During te time period from 2010 to 2030, te estimated increase in energy consumption is planned up to 50%; te largest sare of te consumption will be used for providing eating, ventilation and cooling. Similar developments could look to alternative energy sources, suc as wind or biomass, to supply te non-solar fraction, tus acieving truly zero carbon communities. How muc solar or wind power is available at any given moment is completely unpredictable. Storing electrical energy surplus from wind turbines or solar potovoltaics (PVs) is more problematic tan storing eat. More efficient production of energy contributes to te saving of primary energy resources, monetary resources and leads to te reduction of armful emissions to te environment [1, 2, 14]. Cogeneration is simultaneous generation of electricity and production of eat witin one termal dynamic cycle by using te same type of fuel. Tis process is referred to as te combined production of eat and electricity. Energy can be produced by a steam or gas turbine, or internal combustion engine tat is connected to a power generator. Fig. 1. Possible types of energy production. Cogeneration is implemented by applying internal combustion engines, steam and gas turbines, fuel elements, and microturbines [1, 2]. Te ratio of te installed termal capacity of cogeneration equipment to te consumer s maximum eating load is te eating system rate and it is calculated as follows: termal max( eat cog max vent) cog cog aver( ot. water) cog p. boiler (1) were α termo te coefficient of termofication; cog te ratio of te installed termal capacity of cogeneration; max te maximum eating load of consumer. Index α is used for denominating tis ratio, and tis is te quality index of a cogeneration system describing ow many kw of electricity can be generated on te basis of one kw of eat delivered to te customer. Tis index describes te possibilities of termal engines in electricity generation witin te cogeneration system, and it depends on a number of factors, including te eat consumption: load; te type of te eat carrier (steam, water); te parameters of te eat 64

2 2013 /14 carrier (temperature, pressure). Termofication factor normally ranges witin in order to get as many ours of use of cogeneration plant installed capacity as possible. If cogeneration equipment is designed in compliance wit te eat demand it as several advantages: more efficient use of te fuel energy; emission reduction; considerable reduction in te energy production costs contributing to te competitiveness of a company; a possibility to offer ceaper energy to consumers, including ouseolds; less transmission loss in te decentralised system; te creation of competitive environment in te energy production sector; a comparatively sort payback period of te equipment. Te eat tat is produced witin te cogeneration cycle can be used as follows: for eating and ot water production; for steam production; for cooling; in tecnological processes by using te eat of exaust fumes. Te electricity generated witin te cogeneration cycle can be used for te needs of te cogeneration plant for ensuring its production processes; te surplus can be sold to a licensed electricity transmission or distribution company (see Table I). Trigeneration is te combined production of electricity, eat and cooling. Cold can be produced: in te compressor-type cooling equipment, were electrical engines are used for drive; in te absorption-type cooling equipment, were instead of electricity ceap eat sources are used, suc as emitted exaust gases, ot water, etc. Micro-cogeneration equipment it can be used in ouseolds (in bot individual and apartment ouses), otels, ospitals, swimming pools for eating, ventilation and ot water production; te possible electrical load is up to 50 kw. Low capacity cogeneration equipment it can be used in apartment ouses, otels, ospitals, swimming pools for eating, ventilation and ot water production; te possible electrical load is up to 1MW. Hig capacity cogeneration plant for te provision of energy supply and production processes: eating, ventilation and ot water production; te possible electrical load is above 1 MW. II. CLASSIFICATION OF COGENERATION EUIPMENT Decentralised combined electricity and eat production is an important tecnological solution for improving energy efficiency, saving primary energy resources, improving te security of energy supply, reducing CO2 emissions, and saving money resources at te same time. Small-scale local cogeneration plants ave also lower energy transmission losses. Micro and low-capacity cogeneration plants operate wit te module of an internal combustion engine or gas turbine [3]. Low-capacity cogeneration gives a customer an opportunity to coose te most profitable type of energy supply (see Fig. 2). Fig. 2. Te types of use of cogeneration units for commercial and public buildings and ouseolds. 65

3 TABLE I THE TYPES OF USE OF THE ENERGY PRODUCED IN THE MICRO AND LOW-CAPACITY COGENERATION CYCLE Use of eat Use of electricity District eating boiler ouses Heating, ot water production Ligting, operation of pumps, te surplus is sold to te grid Offices, buildings otels, ospitals, Heating, ot water production Ligting, ventilation, te surplus is sold to te grid swimming pools Houseolds Heating, ot water production Ligting, operation of pumps, te surplus is sold to te grid Te European Union and te governments of some countries, for example, Germany and Great Britain, promote te use of cogeneration for attaining bot te international and national goals as regards te reduction of carbon dioxide emission. For example, te government of Great Britain as set te goal to reduce CO2 emissions in te ouseold sector to 60% by By te year 2050 micro-cogeneration systems could provide 30 40% of te electricity demand in Great Britain. Generally, large- and small-scale cogeneration systems for industrial use or for te application in small-scale organisations, for example, scools, ospitals, district centres or residential areas, ave demonstrated good results. However, te researc is ongoing for ensuring tat micro-cogeneration systems could be used on a wider scale in ouseolds. Micro-cogeneration is particularly interesting to small and medium family ouses, smaller buildings, small and medium businesses due to te following tecnical and operational features: ig total energy transformation efficiency (for example, above 90%); low maintenance costs in comparison wit a similar gas-fired eating boiler for a ouse; low noise and vibration level for devices at ome; low NOx, CO2, SOx and particle emissions. By installing a cogeneration unit, te following benefits can be obtained: te provision of te eat supply and partial electricity supply of a building; te reduction in te building electricity costs; te reduction in te total building energy costs; te reduction in CO 2 emissions. Te following benefits cannot be obtained by means of cogeneration: free of carge electricity (fuel as to be consumed for its generation); instant savings of money; money savings if te unit is not operated. Primary energy Production loss Transmission loss Energy available for use Plant Transmission Fig. 3. Energy produced in te condensing mode. 66

4 2013 /14 Primary energy Production loss Energy available for use Micro cogeneration Fig. 4. Energy produced in micro and low-capacity cogeneration units. Witin te framework of te project implemented by te International Energy Agency on te simulation of te fuel elements and oter cogeneration systems integrated in buildings, a common approac to te implementation of micro and low-capacity cogeneration units in te residential sector was developed [4]. Te results of te researc demonstrated considerable benefit. Te efficiency of te power generation by smallscale fuel elements, Stirling and internal combustion engines was witin te range from 9% to 28%, and te total efficiency was 55% and above for certain units. In recent past te use of cogeneration systems in te residential sector was restricted because of te unavailability of equipment. Tanks to te successful development of te manufacturing of micro cogeneration units and te elimination of tecnical drawbacks, a vast and accessible market of cogeneration units is becoming a reality [11]. III. USE OF NATURAL GAS IN COGENERATION IN HOUSEHOLDS Wen micro cogeneration units are installed as te replacement of conventional boilers te fuel consumption decreases, tus reducing releases of armful emissions into te environment. A broader application of cogeneration in ouseolds is a way to reduce carbon dioxide emissions, tus complying wit te obligations imposed upon te European countries by te Kyoto Protocol. Natural gas is te most popular fuel tat is used in low-capacity cogeneration units. Tis is one of te most profitable and environmentally friendly types of fuel as it produces less CO2 and NOX, does not produce as and sulpur compounds (SO2 and SO3) as opposed to coal or HFO. Wareouses or reservoirs are not required for storage of natural gas, and te full automation of equipment is also possible, etc. During a researc project financed by te European Union and including te analysis of te potential market for micro cogeneration units in te old member states it was concluded tat approximately 13.5 million ouseolds were potentially suitable for installing tis type of units wit te electrical capacity in te range of 1 to 5 kw. Te Dutc experts ave estimated tat te reduction in carbon dioxide emissions will amount to approximately 1000 kg per ouseold micro generation unit. Te annual primary energy consumption is calculated as follows: p ( ) E, (2) w p were p te annual primary energy consumption, m 3 /; te annual energy demand for eating, m 3 /; w te annual energy demand for ot water production, m 3 /; Ep te efficiency rate of te equipment. Fig. 5. Te operation of a micro and low-capacity cogeneration system 67

5 From te external visual appearance and te eat capacity, te ouseold micro cogeneration unit is identical to te existing gas-fired boilers installed in kitcens. In addition to eat, te unit also generates electricity. Depending on te required eat load, te micro engine is supplemented wit a igly efficient gas burner and also wit a eat accumulation tank, if it is required. Te automated control system ensures tat te unit generates electricity only wen tere is demand for eat. Domestic microgeneration gives te same comfort as a gas boiler, but wit lower energy payment and CO2 emission [5]. Te gas microgeneration systems are being installed in te Neterlands, Germany, and Great Britain. Te power generation capacity of te unit is intentionally designed low, up to 5 kw to ensure tat it covers te basic load of te power consumption by an average ouseold. Te results of te study carried out by te International Energy Agency demonstrated tat a cogeneration system reduced te consumption of primary energy resources by up to 33% and te emission of greenouse gases by up to 23% in comparison wit te conventional steam boiler or water eater. In Europe, te following companies manufacture micro cogeneration units Viessmann, WisperGen, Bosc Termotecnik/ Buderus, Baxi, Vaillant, Senertec. Tecnical Parameters of a Micro Cogeneration Unit Natural gas consumption 2.1 m3/; eat capacity 12.5 kw; electrical capacity 5.5 kw; eat capacity of te condensing gas burner 15.5 kw; total efficiency rate 89%; efficiency rate in te condensing mode 100%, dimensions 720x1070x1000 mm; weigt 530 kg; service after te operation of Fig. 7. Houseold micro cogeneration unit. been sold to ensure te energy supply of ouseolds, commercial enterprises and public buildings [13]. It as been calculated tat 13.5 million ouseolds in te European Union are suitable for tis microgeneration installation. Te best microgeneration option for a project may be a combination of two or more separate but compatible tecnologies [15]. Fig. 6. Te sceme of te operation of a micro cogeneration unit. In te Neterlands, gas-fired eating systems are installed in more tan 6 million ouses and approximately units are replaced by more modern ones every year [12]. In Germany, a village of 30 residential ouses wit installed micro cogeneration units as been built. In Germany, 85 tousand of micro and low-capacity cogeneration units ave Volume of natural gas consumption as increased in recent years in Latvia. Major part of gas in Latvia is consumed for eat production, as well as it is consumed on an everyday basis in manufacturing and ouseolds. Te company, wic provides natural gas to consumers, sould forecast te volume of gas consumption for te next years in order to make timely canges in supply volumes, tereby satisfying te consumers and efficiently utilizing its own resources. In Latvia, te consumption by ouseolds accounts for 38% of te total energy consumption. 87% of te total consumption of energy resources is used for eating ouses and producing ot water; 13 % (electricity) is used for operating ouseold devices and ligting. 68

6 2013 /14 In Latvia, tere is a ig deficit of electricity generation capacity. In 2010, ouseolds in Riga region consumed 580 GW of electricity, and it accounted for approximately 25% of te total energy consumption in Riga region (see Figure 8). If state support instruments are provided for te installation of micro cogeneration units in ouseolds, and also if ouseolds are motivated to invest teir resources in teir energy independence additional electricity generation by ouseolds is feasible and tis would reduce te electricity deficit [ 6, 7] Oter Electrical transporation of te city Industry Trading and catering companies Non-industrial consumption Houseolds Fig. 8. Sales of electricity to consumers in Riga region (GW). In te territory of Latvia, gas-fired eating units are installed in 39 tousand ouseolds of wic 60% (24 tousand ouseolds) are located in Riga region; teir allowed load is up to 6 m3/. Te operating ours of a ouseold eating unit are equal to approximately ours per year; if a micro cogeneration unit wit te electrical capacity 1 3 kw is installed it can cover te selfconsumption of an average ouseold. Te annual electricity generation can amount to kw. If micro cogeneration units were installed in 30% of te ouseolds (7.2 tousand) in Riga region, te annual power generation could amount to 108 GW or 18% of te electricity demand of te ouseolds in Riga region [8]. It is necessary to estimate te maximum ourly consumption of natural gas (m 3 /) to ensure te stability of gas supply, te secure operation of te units for te current gas consumers, as well as provide te possibility of installing innovative units. Te estimated ourly consumption of natural gas d (m 3 /) as to be estimated by adding up te rated gas consumption of gas-fired devices and taking into account te rate of teir simultaneous operation: were d m i1 K sim q nom n i, (3) d K K sim sim m i1 nom te sum of te multiplication of te values; q n from i to m; i te rate of simultaneous operation, for residential ouses in compliance wit te standard LVS 417:2011 [9]; q nom te rated gas consumption (m3/) of te device or a group of devices based upon te data of te unit certificate or te tecnical description; n i te number of te units or groups of units of te same type; m te number of types of te devices or groups of devices. Based upon te estimations of natural gas consumption, it is also necessary to perform te ydraulic assessment of te system of gas pipelines [9, 10]; as regards te current low pressure gas supply system, te allowed pressure drops sould also be evaluated. At present, te existing low pressure external distribution gas pipelines are eavily loaded and pressure drops in tem start to exceed te standards; owever, te existing system of medium pressure gas distribution pipelines can supply te load of additional units in te residential areas. If te replacement of gas distribution pipelines is necessary, also te tecnical costbenefit analysis sould be carried out for te purpose of assessing eventual investment. 69

7 IV. CONCLUSIONS Te European Union experience regarding te installation of micro cogeneration units in ouseolds as been evaluated. Te possible consumption of electricity generated in cogeneration per ouseold as been estimated. By te installation of cogeneration units in ouseolds, te savings of primary energy resources are gained; in Riga region it is possible to generate up to 25% of te electricity required for ouseolds. It is necessary to develop a field standard for te design and installation of gas-powered cogeneration plants in te territory of Latvia. Te existing medium pressure gas distribution pipelines in te residential areas provide for te installation of innovative devices micro cogeneration units. Te support of te government is required for te installation of micro cogeneration units in ouseolds were natural gas is consumed. REFERENCES [1] Implementing te Energy Performance of Buildings Directive (EPBD), European Union, [2] Energy Efficiency Requirements in Building Codes- Energy Efficiency Policies for New Buildings, OECD/IEA, [3] AGFW Regelwerk, Arbeitsblatt FW 308 Zertifizierungvon KWK Anlagen Ermittlung des KWK Stromes, Berlin, Januar [4] Te European Educational Tool on Cogeneration, Second Edition, European Union, [5] Bundesministerium fur Umwelt, Naturscutz und Reaktorsicereit, Energie Dreifac Nutzen, Strom, Warme und Klimascutz: Ein Leitfaden fur kleine Kraft Warme Kopplungsanlagen (Mini KWK), Bonn [6] Regulations No.9 Requirements for Combined Heat and Power (CHP) Plant and Procedures by wic Purcase; Price of Surplus Electricity Produced sall be Determined, te Cabinet of Ministers of Latvia Riga, 8 January [7] Regulations (No.221) Regarding Electricity Production and Price Determination Upon Production of Electricity in Cogeneration, te Cabinet of Ministersof Latvia, Riga, 10 Marc [8] A. Davis I. Laube, I. Bode, Use of natural gas in cogeneration at ouseolds, presented at WEC Central & Eastern Europe energy forum, FOREN 2012, Bukarest, Romania, [9] LVS 417:2011. Gāzes sadales un lietotāju sistēmas. Ārējie gāzesvadi un regulēšanas iekārtas. Projektēšana, Latvijas valsts standarts, [10] I. Platais, P. Graudiņš. Gāzapgāde. 2.daļa. Dabasgāzes gāzapgādes sistēmu izveide, ierīkošana un apkalpe. Rīga: RTU, pp.220. [11] J. Klimstra, M.Hotakainem, Smart Power Genration, 4 t improved edition. Helsinki: Printing House Arkmedia Vaasa, pp [12] E. J. Foster, Distribution Grid Operation Including Distributed Generation, P.D. dissertation, Tecnical University of Eindoven, Neterlands, [13] J. Klimstra, Te Road to Obtaining te Ultimate Performance of Gas Engines Opportunities and callenges in Presented at 5 t Dessau Gas Engine Conference, Dessau, Saxony Germany, [14] S. Solomon, D.in, M.Manning, (edc). Climate Cange Te Pysical Science Basis. ISBN United Kingdom and New York, USA: Cambridge University Press, [15] A.Vuorinen, Planing of Optimal Power Systems. ISBN Espoo. Finland: Ekoenergo Oy, Ināra Laube received a ualification of Civil Engineer from te Faculty of Building and Civil Engineering, Riga Polytecnic Institute (1984). Se obtained a Master of Science Degree in Heat, Gas and Water Tecnology in At te moment, se is a doctoral student specialising in Heat, Gas and Water Tecnology at Riga Tecnical University. I.Laube is te Head of te Gas Supply Development Division of JSC Latvijas Gāze. Se is a Member of te Latvian Union of Heat, Gas and Water Tecnology Engineers. inara.laube@lg.lv. Ilmārs Bode obtained is Master of Science Degree in Heat, Gas and Water Tecnology in At te moment, I.Bode is a doctoral student specialising in Heat, Gas and Water Tecnology at Riga Tecnical University. I.Bode is te Head of te Operation and Maintenance Division of JSC Latvijas Gāze. He is a Member of te Latvian Union of Heat, Gas and Water Tecnology Engineers. ilmars.bode@lg.lv. Ivars Platais is a Doctor at Riga Tecnical University (RTU) since te 1970s. He as worked at JSC Latvijas Gāze for 50 years and as eld leadersip positions. He as been te Head of te Training Centre of JSC Latvijas Gāze for 15 years. Currently I.Platais is an Administrator of te Latvian Union of Heat, Gas and Water Tecnology Engineers. 70