Biomass Cogeneration in Europe: economical, technical and environmental evaluation

Transcription

1 Biomass Cogeneration in Europe: economical, technical and environmental evaluation D.Vamvuka* 1, E. Mavrou 2, G. Bandelis 2, T.Tsoutsos 3, and I. Papamicheal 4 1 Associate Professor, Mineral Resources Engineering Department, Technical University of Crete, Greece. 2 Researchers, Mineral Resources Engineering Department, Technical University of Crete, Greece. 3 Assistant Professor, Environmental Engineering Department, Technical University of Crete, Greece. 4 Scientific Collaborator, Centre of Renewable Energy Sources, Picermi, Athens, Greece Abstract Cogeneration of Heat and Power (CHP), using biofuels, is a challenging subject combining the benefits of the conventional and alternative technologies with very high overall. Several actions have been taken to promote the widespread development of CHP in Europe and worldwide. The EU and the member states have funded several RTD projects in order to imply, develop and promote CHP technologies. The use of biomass as a fuel is attractive, due to the environmental benefits and to the barriers that are evoked. The aim of this study was to evaluate and compare current CHP biomass fired technologies, in order to conclude to a clear state-of the-art of the current technological status. The study focuses on the European status and on the benefits of biomass used as a fuel. A detailed analysis was conducted providing technical economic and environmental data and trends. Through specific indicators, key issues in the implementation of biomass CHP in Europe were compared, aiming to facilitate the goal of 26 Mtoe biomass CHP installations to be reached by Keywords: CHP, biofuel, thermal power Introduction Cogeneration, also known as combined heat and power (CHP), is the simultaneous generation of heat and power, both of which are used [1]. CHP units have better total than conventional energy systems, since better exploitation takes place and energy is used for the production of heat as well. Electricity and heat can be generated in a large variety of scale. Usually, the environmental performance of CHP biomass plants is good, compared to fossil fuels. Theoretically, if biomass is grown in a sustainable, carbon-neutral manner, the energy conversion systems lead to neutral CO 2 emissions [2]. The emissions can be reduced by the implementation of improved methods of CO 2 capture, or new CHP technologies. Specific Objectives Although there is a great progress concerning CHP biomass systems and the literature is optimistic about their future [3], there is a slow integration in the European energy market system. The purpose of this study is to support a brief evaluation of CHP biomass systems in Europe. The current status of biomass CHP technologies in EU is presented and data is compared, in order to conduct an evaluative study of recent trends, aiming to facilitate the goal of 26 Mtoe biomass CHP installations to be reached by Status in the European Union In the European Union (EU) there is lack of homogeneity concerning the CHP energy sector. In Figure 1, the share of existing solid biomass CHP plants is given, while in Figure 2 the technologies used are shown. These technologies studied are Steam Turbine System, Steam Engine System, Internal Combustion Engine Systems (ICE), micro turbines, Combined Cycle Systems (CCS), Stirling Engine and Organic Rankine Cycle (ORC). number of units The 5 reasons of the variety of status relates with the obstacles 0 met for the penetration of CHP in the energy market. Germany, Austria, Finland and Denmark use more CHP technologies than other countries. Austria has a significant energy policy promoting CHP. The existence of district heating network is also an Figure 1: Status of CHP biomass units in Europe [4] Austria Denmark Finland France Germany The Italy Portugal Slovenia No cofiring Co- firing Sweden Switzerland Greece G.B. The reason of the variety of status relates with the obstacles met for the penetration of CHP in the energy market. Germany, Austria, Finland and Denmark use more CHP technologies than other countries. Austria has a significant energy policy for CHP. The existence of district heating network is an important factor, as well as the public s participation. The only two commercial ORC biomass plants in the EU are located in Austria (in Admont 0.4 MWe, 1.8MWth; in

2 Leinz 1 MWe, 4.4 MWth). The efficiencies of the two plants are shown in Figure 3. Figure 2: Distribution of solid biomass CHP plants [4] Denmark targeted to be independent from oil import since It has a well-integrated DH network and several laws and institutions providing economic benefits and funding for new green technologies. Germany has a strong environmental energy policy. Several laws protecting CHP are installed, whilst there are measures for the promotion of CHP and renewable energy. (%) % 1% 11% admond 1% 1% 1% 4% 9%2% 1% 2% 8%0% 8 leinz 20% Holland Italy Portugal Slovenia Sw itzerland Sw eden Turkey UK Austria Bulgaria Denmark Finland France Germany electric thermal total Figure 3: Efficiencies of Small Scale ORC biomass power plants Finland has energy policies that favour bioenergy. Taxation measures, spread of relative information, educative policy, wood industry and exportation of energy technology lead to the good integration of biomass CHP to the energy sector. Finland supports R&D on new and renewable energy technologies. Some of the reasons of inserting new trends in the energy sector are listed in Table 1. The role of environmental issues is not always clearly defined [3]. The basic obstacles for CHP spreading are as follows. First, the current status of fossil fuels in the energy market makes more difficult the change. The rather high procurement cost of CHP technology is an obstacle, which can be overcome with funding support. The liberalization of the electricity market leads to a decline in the price of electricity [3], which does not make the use of CHP attractive in the short-, but can make attractive the investments in small-scale CHP in the long-term [3,5]. In addition, there is lack of information concerning CHP trends, leading to lack of confidence in CHP, insecurity, economic competition with other forms of electricity generation and lack of public administration support [3,9]. Evaluation methodology In order to compare and to evaluate the different CHP technologies, the definition of indicators through the performance parameters of the systems is necessary. Using technical, economic and environmental data and trends, an analysis was conducted. The typical parameters used to measure the performance of a cogeneration plant are [10]: electrical, heat and overall and the power/heat ratio. Additionally, the investment, operating and maintenance costs should be taking into account. Another important indicator is the environmental performance of the systems. The indicators studied in this work are shown in Figure 4. The data have been collected through R&D articles on recently constructed biomass CHP plants in Europe, or cogeneration reports. The data was collected, categorized and presented in Tables 2 through 4. Table 1:Operational environment of energy generation [3,5-8] Political Economic Social Technological Taxation Standard of living Population structure Natural conditions Legislation and regulation Energy production infrastructure Distribution of incomes Availability of electricity and fuels International agreements Purchasing power Organizations operating on the Life style Existing technologies and their features Political stability of society Governmental support Political definitions (emission trade, nuclear energy) market Economic development Interest rates Liberalization of energy market Inflation Location Price of energy, fuel, technology 2 Opinions on green issues Awareness of new technologies and possibilities Standard of education Traditions Rate of technological development

3 Table 2: Technical indicators of CHP biomass systems Indicator/ Power/heat Overall Reliability and availability Partial load Technology Steam turbine [10], 80%[10] most common[10], suppliers, 0.49 [21] good techn expertise [10, 11] Steam engine 0.18 [13] 80%[10], [13] good [10] 9.5% 75-85% [12] (electric) [13] Electric Automation Operation and maintenance 10-30% [10] proven [10,11] 12.6% (nominal load) [13] 10-20% [12] 6-20% [10] proven [10] CCS 1-1,25 [10] 90% [10] 90% [25] 45-50% [10] regular maintenance and service [15] ICE 0.4-1[15], 1/3 [22], [16] 85-90% [15] 75-85% [16] Micro turbine [16] 80% [10] 75-85% [16,12] Stirling engine [16] 75-85% [16] 90%[17,18] 80-90% [12] ORC [10,12] 70% [21] 85-95% [12] high level [15] 25-45% [15] at full load [16] good [15] reduced [15] 15-35%[12] 20-30% [10] average availability:80%[17] 25-30%[10] 15-35% [16,12] 20% [17] high (up to 98%) [21] 90-98% [20] high [21] up to 18%, very high[20] 16.5% (>excellent) [17] 10-20% [10,12] 15% [21] 18% (nominal load) [17] fully automated[17, 18] fully automatically [11,13]] regular [15] periodic maintenance, high levels of availability minimal maintenance (low requirements) [15] ease operation, low maintenance [21] very good performance[20] 3

4 Table 3: Economical indicators of CHP biomass systems Indicator/ Technology Steam turbine Investment costs Taxation and consumables Maintenance costs low[22] Steam engine /kwe [21] (payback time 13yrs) production cost: 0,138 /kwe [21] ,23 /kwhe [1] CCS electricity production cost: 10,18-11,00$c/kWh (depending on the fuel) [25] maintenance cost 0,75 $c/kwh ICE ($/kW) [16] 1,2-2,0 $c/kw [16] maintenance costs differ with the type, speed, size ad umber of cylinders of an engine[15] generally:0,008-0,013s/kwh[23] Micro turbine ($/kw) [16] high service cost [16] Stirling engine ($/kw) [16] decreased need for service [16] ORC cost effective plant (payback 4-8yrs) [21] 3,2 k payback time:7yrs[20] capital costs: 380 /kwe (or ~0,08 /kwhe)[17] low [15] 0,5-1,5 $c/kw [16] $c/kw [16] total operation cost: 381 k /a (maint:50 k /a). low maintenance demands and man power [20] total electricity production cost: 0,12 /kwhe[22] operation cost:0,1 /kwhe[17] Table 4: Environmental indicators of CHP biomass systems Technology Steam turbine >5MWe, lower than ORC [21] Emissions Steam engine good environmental. performance[13] CCS reduction of environmental emissions [10,14] ICE CO 2 and SO 2 emissions are strongly dependent on the fuel used, the amounts of NOx, CO and incombustible hydrocarbons in exhaust gases depend on other conditions of combustion, like the temperature and the amount of air. [16] Micro turbine low[15], esp NOx [16] Stirling engine low (esp NOx) [16] [17, 18, 19]: *THE CO EMISSIONS OF THE MORE RECENT R&D SHOWS LOWER DATA (comparing [18] and [19]) ORC low, [10] very low, important contribution to environmental protection [20] 4

5 CRITICAL REVIEW Economical Investment Operating Maintenance costs INDICATORS Technical Power/heat Overall Reliability and availability Partial load Operation and maintenance Automation Figure 4: Schematic methodology Environmental Emissions DECISION MAKING Results and Discussion The Steam Turbine System is one of the most common technologies used. This results in a good technological expertise and sufficient suppliers. The systems present high total efficiencies in district heating (DH) applications, operating experience and reliability, whilst they have a standardized plant design, which results at shorter construction time and lower investment costs. The smaller units (< 5MWe) are of simple design, whilst the larger ones are more complex [10,11, 19]. They have low maintenance costs, good efficiencies, proven operation and maintenance and good environmental performance. The Steam Engine systems are used commonly for industrial application, while there are limited suppliers for small-scale units. The systems present good overall efficiencies, good availability and reliability, proven operation and maintenance, whilst the payback period can be reached at 13 years (for a unit producing 730kWe, 4.800kWth, and operating 3.000MWh/a) [1, 10, 12,13]. Combined Cycle Systems (CCS) require regular maintenance and service, present very good overall, high for electricity production and reduction of environmental emissions [10,14]. The use of biomass as a fuel to CCS units (also mentioned as BIGCC) is still under development [15], while it improves the environmental performance of the units [14]. Internal Combustion Engines (ICE) have very good overall, present high levels of availability and require periodic maintenance [15]. They present low level of environmental emissions, although the CO 2 and SO 2 emissions depend on the fuel used and the amounts of NOx, CO and incombustible hydrocarbons in exhaust gases depend on other combustion conditions (temperature, amount of air) [16]. They have low capital 5 cost, wide service infrastructure and low operating cost. They provide reliable onsite energy and large power range [15, 16]. Micro-turbines present good technical performance: they have low noise and vibration, low weigh and small size. They require minimal maintenance and have proven good overall, good reliability and availability, but reduced partial load. They have low emissions, especially NOx, which makes them more environmental friendly [10,12,15,16]. Other advantages are their compact size, small number of moving parts and short delivery time [15], but they have high service cost [16]. Stirling Engines are an interesting option, as well. They are fully automated, which decreases the need for service, have very good environmental indicators, and show even lower CO emissions. It is a new technology with very good performance and perspective. It is suitable for buildings, because of the power/heat ratio, low noise, and lower need for service, good partial load behaviour and ability to handle quick load changes [12,16,17,18, 19]. The technology is under R&D, but has improving results and bigger units are constructed, using improved technology and implying further development. Organic Rankine Cycle technology shows interesting potential as well, although it has increased investment costs. The environmental indicators are very low [20,10,17,21]. The technology is still under R&D, but the two plants presented at Section 2, have shown very promising results. Conclusions Current trends on energy production demand that energy systems have good environmental performance, like CHP units using biomass as a fuel. They present better exploitation of the fuel, better environmental performance, in terms of emissions, and reduction of biomass residues. The ORC, CCS and Stirling engine technologies show better environmental results in the most recent studies. New biomass energy production systems have good performance and reliability, which improves constantly. The steam turbine systems are more secure and reliable, due to the technological expertise and the standard plant design, while steam engines are most common for industries. The CCS present very good overall, availability and reliability. The ORC technologies have proven to be cost effective with low maintenance cost, while Stirling engine seems to have higher investment and maintenance costs than microturbine. This is the first phase of such work. Further work is going to be developed in cooperation with the potential technology suppliers and their associations. This study presented a critical review of the recent trends on biomass CHP technologies in Europe, providing a tool to energy decision makers in order to

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