CHP
Distributed generation for sustainable development – Case Finland Research Manager Satu Helynen VTT Processes P.O.Box 1603 40101 Jyväskylä Finland Tel. +358 20 722 2661 [email protected]
Abstract During 1980’s CHP production increased rapidly because the production of forest industry was growing fast and district heating networks were enlargened. Electricity prices were moderate because of large capacity additions using nuclear power. The competitiveness of CHP plants using solid fuel needed a minimum heat load of 200-300 GWh/a, which meant about 30 MW electricity. Natural gas fired CHP plants were competitive when annual heat loads were over 50 GWh. In the 1980’s power plant investments, price of energy, and imports of fuels and electricity were regulated. Also most of the largest energy companies were owned by the state. Privatisation and deregulation started in the 1990’s; deregulation of the electricity market was completed in 1996. In 1990’s the smallest solid fuel CHPs were providing 5 MW electricity, the economy was guaranteed by investment subsidies up to the level of 30 %. Presently the competitiveness level has decreased to 1 – 3 MW electricity, and novel technologies with higher power-to-heat ratios have been developed. Kokemäki CHP plant, having start-up in 2005, with a fixed bed gasifier for wood fuels connected combustion engines is presented, as well as other new demonstrated concepts. Both technical, economical and institutional issues on distributed generation and its connection to transmission and distribution networks of electricity, district heat and natural gas are described. The role of distributed generation in the deregulated energy market and the emission trade is discussed.
Risø-R-1517(EN)
288
1 Introduction In Finland, energy consumption per capita is high due the severe climate, long distances and energy-intensive basic industry. Industry consumes over 50% of the total energy demand, and space heating 19%. Self-sufficiency in energy supply is in Finland less than 50%, because all the fossil fuels and also up to 15% of electricity are imported to Finland. The gross efficiency of combustible fuel based electricity generation is exceptionally high (65%), because one third of power generation is covered by cogeneration plants (Fig. 1). Half of those plants produce power and district heat for municipalities and and the other half operate in the industry producing power and process steam. The utilisation of local renewable energy sources for heat and electricity production is promoted by the Finnish energy strategy in order to reduce greenhouse gas emissions and to increase security of the energy supply (MTI 2001). Also positive effects on employment and economy of rural areas are significant.
C H P – d is tric t h ea tin g C H P - in d u s try
N u c lea r p o w e r C o n d e n s in g p o w er H yd ro a n d w in d p o w e r N e t im p o rts
Figure 1. Electricity production in Finland (Kara 2004). Bioenergy covers in Finland 20% of the primary energy consumption and 10% of the electricity demand which are the highest figures within the industrialised countries. Possibilities to increase the total use of bioenergy by 50% and nearly to double the generation of bioelectricity before 2015 has been identified by VTT Processes (MTI 2000). Biomass-based fuels have traditionally included residues from the chemical and mechanical forest industry and wood fuels used for heating homes. Forest chips from harvesting residues, straw, perennial energy crops, such as reed canary grass, biogas and recycled fuels have complemented the supply of biomass-based fuels during the last decade. Multifuel operation of boilers and cofiring biomass with coal are preferred in large power plants because the availability of many types of biomass is seasonal and can have significant variations from year to year.
Risø-R-1517(EN)
289
2 Role of combined heat and power (CHP) production in Finland 2.1 Increased competitiveness of CHP The major source of distributed energy generation in Finland is combined heat and power (CHP) production that typically decreases about 30% of the fuel demand compared to separated heat generation by boilers and power generation by condensing power plants. The share of CHP of the total electricity consumption was 32 % in 2004, and the share has increased steadily (Fig. 2).
S h a re o f p o w er p ro d u c tio n o n th e p rim a ry e n e rg y d e m an d
S h are o f C H P o n p o w er g ene ratio n
Figure 2. The share of CHP in the total electricity generation in Finland (Kara 2004). During the late 1980’s CHP production increased rapidly because the production of forest industry was growing fast and district heating networks were enlargened. Electricity prices were moderate because of large capacity additions using nuclear power. The competitiveness of CHP plants using solid fuel needed a minimum heat load of 200-300 GWh/a, which meant about 30 MW electricity. Natural gas fired CHP plants were competitive when annual heat loads were over 50 GWh. In the 1980’s power plant investments, price of energy, and imports of fuels and electricity were regulated. Also most of the largest energy companies were owned by the state. Privatisation and deregulation started in the 1990’s; deregulation of the electricity market was completed in 1996. In 1990’s the smallest solid fuel CHPs were providing 5 MW electricity, the economy was guaranteed by investment subsidies up to the level of 30 % (MTI 2003). Presently the competitiveness level has decreased to 1 – 3 MW electricity when using solid fuel, such as wood chips (Fig. 3).
Risø-R-1517(EN)
290
C a p ac ity o f th e C H P p la n t, p o w e r/h e a t p ro d u c tio n (M W )
Figure 3. Effects of capacity of the CHP plant on specific investments (Kara 2004) Combined heat and power (CHP) production in the forest products industry and district heating networks of municipalities based on fluidised bed boilers and steam turbines is still the dominant technology for bioenergy utilisation in Finland. Power-to-heat ratio has improved with higher steam values, and supercritical once-through circulating fluidised bed boilers using also biomass as a cofiring fuel with coal are under design.
2.2 Possibilities to increase CHP The available heat loads for CHP are smaller and smaller, because larger, most competitive heat loads have already been utilised. The share of district heating has increased steadily replacing especially use of fuel oil for heating (Fig. 4) providing heat load also for CHP. Another favoured option to replace exported fuels is the use of wood fuels in farms, homes and separate buildings, especially heating systems for wood chips and pellets have been installed widely during the last years.
E lec tric h eatin g
D is tric t h e a tin g G ro u n d h ea t L ig h t fu e l o il
H ea vy fu e l o il
N a tu ra l g as
Coal P ea t
W o o d fu e ls
Figure 4. Energy sources for heating in Finland (Kara 2004).
Risø-R-1517(EN)
291
Process industry can provide a high number of annual operating hours for CHP plants which improves economy. Mechanical wood processing, such as saw mills, has both wood residues for fuel and heat demand for drying purposes, which creates favourable conditions for CHP.
3 New technologies The fluidised bed combustion is dominant for large-scale applications of bioenergy world-wide, and the market leaders of those technologies are operating in Finland. About 100 large-scale cogeneration units (district or process heat 10-500 MWth, electricity 5250 MWe) are operating with fluidised bed boilers and steam turbines in Finland. Smaller units (0.5- 5 MWe) use typically grate boilers (Figure 5).
Figure 5. Modular CHP plants with rotating grates 1 – 4,5 MWe power + district heating (Wärtsilä Biopower). Fixed and fluidised bed gasifiers using wood chips have been applied for heat generation since 1980’s. The implementation of product gas cleaning enables the use of gas eegines or turbines for electricity generation with a high power-to-heat ratio. The Kokemäki demonstration plant is under construction (Fig.6) by Condens Oy. Its technological innovations are connected novel tar reforming and gas filtering which reduce the demand of product gas scrubbing considerably. Test facilities at VTT in Espoo include 0.6 MW gasifier pilot plant with catalytic gas cleaning, gas filtration and scrubber, pilot boiler with flue gas cleaning equipment and special gas burner as well as laboratory and benchscale test rigs for gas cleaning R&D.The investment cost for the 1,8 MW electricity and 4,3 MW district heat demonstration plant is 4,5 million euros.
Risø-R-1517(EN)
292
gasifier
tar reformer
product gas scrubber gas cooler gas filter JMS 316 engines
ash bin
Figure 6. Kokemäki demonstration plant using a fixed bed gasifier and gas engines (Condens Oy). The future target is CHP plants for ever-smaller heat consumers, because the available large heat loads for district and industrial process heating in Finland are already utilised for combined heat and power consumption (Fig 7.). Diesel and steam engines, and steam and gas turbines are now applied in small-scale CHP of 200 kW - 3 MW electricity. Microturbines, fuel cells, Organic Rankine Cycle (ORC) and Stirling engines are future options for smaller capacity classes.
Gasification + H2 separation Gasification + fermentation Hydrolysis + fermentation Gasification + synthesis Fast pyrolysis + upgrading Biogasification (+ upgrading) Gasification + gas cleaning
Hydrogen
Mobile IC-engine
Ethanol
Fuel cell
Methanol/ F-T-fuel
Reformer
Bio-oil
Micro turbine
Methane
Stationary IC-engine
Fuel gas Pellets
Pelletising
Raw material
Conversion technology
Fuel
Small boiler Stirling engine
Utilisation technology
Utilisation system
Figure 7.Alternatives for distributed energy systems using biomass (Kara 2001). All these new options need standardised concepts and mass or serial production to obtain competitiveness without significant subsidies or other promotion measures. The serial production of CHP plants could be a major measure to decrease investment costs in lowest capacity classes. Earlier steam boilers and turbine plants with all auxiliary systems and buildings have been tailored plant by plant which increases planning and
Risø-R-1517(EN)
293
project management cost significantly. In the same, possibilities to reduce material and manufacturing costs are not fully utilised. Wärtsilä has reported that costs could be reduced by more than 40% if plants have advanced serial production (Fig. 8).
100
Relative costs, %
90 80 70 60
Work Materials Project management Planning
50 40 30 20 10 0
Custom tailored
Series of 5
Tens of plants
Figure 8. Possibilities for cost reduction of (2 and 5 MWe) using serial production ( Wärtsilä Biopower).
small
CHP
plants
The further targets of development of CHP in Finland are summarised in the Figure 9.
CHP products
Electricity District heat Process heat
1960
1980
Back pressure turbine
CHP technologies
Power-toheat ratio
1970
Clean water
0.1%
The share of total CHP electricity in Finland
28%
Combined cycle plants Heat storage
Conventional 0.4 CHP Micro-CHP
The share of district heating CHP electricity in Finland
1990
0.45
0.50
District cooling
2000
Hydrogen
2010
Micro-plants (microturbine, fuel cell,..) Cold storage
28%
Hydrogen storage 1.2-1.5
1.0 0.15-0.20
28%
2020
1.0
14%
16%
28%
31%
37%
50%
Figure 8. Targets of the development of CHP in Finland (Kara 2001).
Risø-R-1517(EN)
294
4 Conclusions The main option for Finland to increase the efficiency of power generation has been the switch from condensing power plants to combined heat and power production (CHP). CHP plants today produce already over 35 % of the total electricity supply in Finland, but the feasible goal could be about 50 % in 2030. About 75 % of district heat is provided from cogeneration plants with a typical overall annual efficiency of 85-90 %. CHP is an efficient way to utilise local energy sources, such as wood fuels, agrobiomass, biogas and peat, and heat loads for electricity generation. New technologies to utilise ever smaller heat loads and local renewable fuels with higher power-to-heat ratios are under development. Fixed and fluidised bed gasifiers connected to combustion engines using solid biofuels are presently under commercialisation. Stirling engines, gas turbines and fuel cells need high value fuels, such as gaseous and liquid biofuels or pellets. Use of natural gas networks for the delivery of biogas and other biomass-based gases is one possible option for enabling small-scale CHP plants using bioenergy. Concept of combined heat and power production could be widened to the distributed production of cooling or desalination of seawater. Mills of the forest and food industry sectors provide an optimal platform for biorefineries that could generate, in addition to steam and electricity, also liquid biofuels for the transport sector and also green chemicals and other biogenic products. Integration of the industrial processes and energy production would increase total efficiencies and decrease specific investment costs.
5 References Kara, M., R. Hirvonen, L. Mattila, S. Viinikainen, and S. Tuhkanen (eds.), Energy Visions 2030 for Finland, VTT Energy, Helsinki (2001). Kara,M.et al (eds.), Energia Suomessa, VTT Processes, Helsinki (2004). MTI, Action Plan for Renewable Energy Sources, Ministry of Trade and Industry, Publications 1/2000, Finland (2000). MTI, National Climate Strategy. Finland. Government Report to Parliament, Ministry of Trade and Industry, Publications 5/2001, Finland (2001). MTI, Implementation of the National Climate Strategy, Ministry of Trade and Industry, Publications 4/2003, Finland (2003).
Risø-R-1517(EN)
295
Abstract During 1980’s CHP production increased rapidly because the production of forest industry was growing fast and district heating networks were enlargened. Electricity prices were moderate because of large capacity additions using nuclear power. The competitiveness of CHP plants using solid fuel needed a minimum heat load of 200-300 GWh/a, which meant about 30 MW electricity. Natural gas fired CHP plants were competitive when annual heat loads were over 50 GWh. In the 1980’s power plant investments, price of energy, and imports of fuels and electricity were regulated. Also most of the largest energy companies were owned by the state. Privatisation and deregulation started in the 1990’s; deregulation of the electricity market was completed in 1996. In 1990’s the smallest solid fuel CHPs were providing 5 MW electricity, the economy was guaranteed by investment subsidies up to the level of 30 %. Presently the competitiveness level has decreased to 1 – 3 MW electricity, and novel technologies with higher power-to-heat ratios have been developed. Kokemäki CHP plant, having start-up in 2005, with a fixed bed gasifier for wood fuels connected combustion engines is presented, as well as other new demonstrated concepts. Both technical, economical and institutional issues on distributed generation and its connection to transmission and distribution networks of electricity, district heat and natural gas are described. The role of distributed generation in the deregulated energy market and the emission trade is discussed.
Risø-R-1517(EN)
288
1 Introduction In Finland, energy consumption per capita is high due the severe climate, long distances and energy-intensive basic industry. Industry consumes over 50% of the total energy demand, and space heating 19%. Self-sufficiency in energy supply is in Finland less than 50%, because all the fossil fuels and also up to 15% of electricity are imported to Finland. The gross efficiency of combustible fuel based electricity generation is exceptionally high (65%), because one third of power generation is covered by cogeneration plants (Fig. 1). Half of those plants produce power and district heat for municipalities and and the other half operate in the industry producing power and process steam. The utilisation of local renewable energy sources for heat and electricity production is promoted by the Finnish energy strategy in order to reduce greenhouse gas emissions and to increase security of the energy supply (MTI 2001). Also positive effects on employment and economy of rural areas are significant.
C H P – d is tric t h ea tin g C H P - in d u s try
N u c lea r p o w e r C o n d e n s in g p o w er H yd ro a n d w in d p o w e r N e t im p o rts
Figure 1. Electricity production in Finland (Kara 2004). Bioenergy covers in Finland 20% of the primary energy consumption and 10% of the electricity demand which are the highest figures within the industrialised countries. Possibilities to increase the total use of bioenergy by 50% and nearly to double the generation of bioelectricity before 2015 has been identified by VTT Processes (MTI 2000). Biomass-based fuels have traditionally included residues from the chemical and mechanical forest industry and wood fuels used for heating homes. Forest chips from harvesting residues, straw, perennial energy crops, such as reed canary grass, biogas and recycled fuels have complemented the supply of biomass-based fuels during the last decade. Multifuel operation of boilers and cofiring biomass with coal are preferred in large power plants because the availability of many types of biomass is seasonal and can have significant variations from year to year.
Risø-R-1517(EN)
289
2 Role of combined heat and power (CHP) production in Finland 2.1 Increased competitiveness of CHP The major source of distributed energy generation in Finland is combined heat and power (CHP) production that typically decreases about 30% of the fuel demand compared to separated heat generation by boilers and power generation by condensing power plants. The share of CHP of the total electricity consumption was 32 % in 2004, and the share has increased steadily (Fig. 2).
S h a re o f p o w er p ro d u c tio n o n th e p rim a ry e n e rg y d e m an d
S h are o f C H P o n p o w er g ene ratio n
Figure 2. The share of CHP in the total electricity generation in Finland (Kara 2004). During the late 1980’s CHP production increased rapidly because the production of forest industry was growing fast and district heating networks were enlargened. Electricity prices were moderate because of large capacity additions using nuclear power. The competitiveness of CHP plants using solid fuel needed a minimum heat load of 200-300 GWh/a, which meant about 30 MW electricity. Natural gas fired CHP plants were competitive when annual heat loads were over 50 GWh. In the 1980’s power plant investments, price of energy, and imports of fuels and electricity were regulated. Also most of the largest energy companies were owned by the state. Privatisation and deregulation started in the 1990’s; deregulation of the electricity market was completed in 1996. In 1990’s the smallest solid fuel CHPs were providing 5 MW electricity, the economy was guaranteed by investment subsidies up to the level of 30 % (MTI 2003). Presently the competitiveness level has decreased to 1 – 3 MW electricity when using solid fuel, such as wood chips (Fig. 3).
Risø-R-1517(EN)
290
C a p ac ity o f th e C H P p la n t, p o w e r/h e a t p ro d u c tio n (M W )
Figure 3. Effects of capacity of the CHP plant on specific investments (Kara 2004) Combined heat and power (CHP) production in the forest products industry and district heating networks of municipalities based on fluidised bed boilers and steam turbines is still the dominant technology for bioenergy utilisation in Finland. Power-to-heat ratio has improved with higher steam values, and supercritical once-through circulating fluidised bed boilers using also biomass as a cofiring fuel with coal are under design.
2.2 Possibilities to increase CHP The available heat loads for CHP are smaller and smaller, because larger, most competitive heat loads have already been utilised. The share of district heating has increased steadily replacing especially use of fuel oil for heating (Fig. 4) providing heat load also for CHP. Another favoured option to replace exported fuels is the use of wood fuels in farms, homes and separate buildings, especially heating systems for wood chips and pellets have been installed widely during the last years.
E lec tric h eatin g
D is tric t h e a tin g G ro u n d h ea t L ig h t fu e l o il
H ea vy fu e l o il
N a tu ra l g as
Coal P ea t
W o o d fu e ls
Figure 4. Energy sources for heating in Finland (Kara 2004).
Risø-R-1517(EN)
291
Process industry can provide a high number of annual operating hours for CHP plants which improves economy. Mechanical wood processing, such as saw mills, has both wood residues for fuel and heat demand for drying purposes, which creates favourable conditions for CHP.
3 New technologies The fluidised bed combustion is dominant for large-scale applications of bioenergy world-wide, and the market leaders of those technologies are operating in Finland. About 100 large-scale cogeneration units (district or process heat 10-500 MWth, electricity 5250 MWe) are operating with fluidised bed boilers and steam turbines in Finland. Smaller units (0.5- 5 MWe) use typically grate boilers (Figure 5).
Figure 5. Modular CHP plants with rotating grates 1 – 4,5 MWe power + district heating (Wärtsilä Biopower). Fixed and fluidised bed gasifiers using wood chips have been applied for heat generation since 1980’s. The implementation of product gas cleaning enables the use of gas eegines or turbines for electricity generation with a high power-to-heat ratio. The Kokemäki demonstration plant is under construction (Fig.6) by Condens Oy. Its technological innovations are connected novel tar reforming and gas filtering which reduce the demand of product gas scrubbing considerably. Test facilities at VTT in Espoo include 0.6 MW gasifier pilot plant with catalytic gas cleaning, gas filtration and scrubber, pilot boiler with flue gas cleaning equipment and special gas burner as well as laboratory and benchscale test rigs for gas cleaning R&D.The investment cost for the 1,8 MW electricity and 4,3 MW district heat demonstration plant is 4,5 million euros.
Risø-R-1517(EN)
292
gasifier
tar reformer
product gas scrubber gas cooler gas filter JMS 316 engines
ash bin
Figure 6. Kokemäki demonstration plant using a fixed bed gasifier and gas engines (Condens Oy). The future target is CHP plants for ever-smaller heat consumers, because the available large heat loads for district and industrial process heating in Finland are already utilised for combined heat and power consumption (Fig 7.). Diesel and steam engines, and steam and gas turbines are now applied in small-scale CHP of 200 kW - 3 MW electricity. Microturbines, fuel cells, Organic Rankine Cycle (ORC) and Stirling engines are future options for smaller capacity classes.
Gasification + H2 separation Gasification + fermentation Hydrolysis + fermentation Gasification + synthesis Fast pyrolysis + upgrading Biogasification (+ upgrading) Gasification + gas cleaning
Hydrogen
Mobile IC-engine
Ethanol
Fuel cell
Methanol/ F-T-fuel
Reformer
Bio-oil
Micro turbine
Methane
Stationary IC-engine
Fuel gas Pellets
Pelletising
Raw material
Conversion technology
Fuel
Small boiler Stirling engine
Utilisation technology
Utilisation system
Figure 7.Alternatives for distributed energy systems using biomass (Kara 2001). All these new options need standardised concepts and mass or serial production to obtain competitiveness without significant subsidies or other promotion measures. The serial production of CHP plants could be a major measure to decrease investment costs in lowest capacity classes. Earlier steam boilers and turbine plants with all auxiliary systems and buildings have been tailored plant by plant which increases planning and
Risø-R-1517(EN)
293
project management cost significantly. In the same, possibilities to reduce material and manufacturing costs are not fully utilised. Wärtsilä has reported that costs could be reduced by more than 40% if plants have advanced serial production (Fig. 8).
100
Relative costs, %
90 80 70 60
Work Materials Project management Planning
50 40 30 20 10 0
Custom tailored
Series of 5
Tens of plants
Figure 8. Possibilities for cost reduction of (2 and 5 MWe) using serial production ( Wärtsilä Biopower).
small
CHP
plants
The further targets of development of CHP in Finland are summarised in the Figure 9.
CHP products
Electricity District heat Process heat
1960
1980
Back pressure turbine
CHP technologies
Power-toheat ratio
1970
Clean water
0.1%
The share of total CHP electricity in Finland
28%
Combined cycle plants Heat storage
Conventional 0.4 CHP Micro-CHP
The share of district heating CHP electricity in Finland
1990
0.45
0.50
District cooling
2000
Hydrogen
2010
Micro-plants (microturbine, fuel cell,..) Cold storage
28%
Hydrogen storage 1.2-1.5
1.0 0.15-0.20
28%
2020
1.0
14%
16%
28%
31%
37%
50%
Figure 8. Targets of the development of CHP in Finland (Kara 2001).
Risø-R-1517(EN)
294
4 Conclusions The main option for Finland to increase the efficiency of power generation has been the switch from condensing power plants to combined heat and power production (CHP). CHP plants today produce already over 35 % of the total electricity supply in Finland, but the feasible goal could be about 50 % in 2030. About 75 % of district heat is provided from cogeneration plants with a typical overall annual efficiency of 85-90 %. CHP is an efficient way to utilise local energy sources, such as wood fuels, agrobiomass, biogas and peat, and heat loads for electricity generation. New technologies to utilise ever smaller heat loads and local renewable fuels with higher power-to-heat ratios are under development. Fixed and fluidised bed gasifiers connected to combustion engines using solid biofuels are presently under commercialisation. Stirling engines, gas turbines and fuel cells need high value fuels, such as gaseous and liquid biofuels or pellets. Use of natural gas networks for the delivery of biogas and other biomass-based gases is one possible option for enabling small-scale CHP plants using bioenergy. Concept of combined heat and power production could be widened to the distributed production of cooling or desalination of seawater. Mills of the forest and food industry sectors provide an optimal platform for biorefineries that could generate, in addition to steam and electricity, also liquid biofuels for the transport sector and also green chemicals and other biogenic products. Integration of the industrial processes and energy production would increase total efficiencies and decrease specific investment costs.
5 References Kara, M., R. Hirvonen, L. Mattila, S. Viinikainen, and S. Tuhkanen (eds.), Energy Visions 2030 for Finland, VTT Energy, Helsinki (2001). Kara,M.et al (eds.), Energia Suomessa, VTT Processes, Helsinki (2004). MTI, Action Plan for Renewable Energy Sources, Ministry of Trade and Industry, Publications 1/2000, Finland (2000). MTI, National Climate Strategy. Finland. Government Report to Parliament, Ministry of Trade and Industry, Publications 5/2001, Finland (2001). MTI, Implementation of the National Climate Strategy, Ministry of Trade and Industry, Publications 4/2003, Finland (2003).
Risø-R-1517(EN)
295
