Final Report Summary - LARGE-SOFC (Towards a Large SOFC Power Plant)
The main task of the LARGE-SOFC project has been the development and verification of concepts, components and sub-systems for solid oxide fuel cell-based (SOFC) power plants with a potential for hundreds of kW to several MW. Thus the aim of the project was to address the basic problems when moving from kW to MW size SOFC power plants. The focus was on technologies with long term potential for:
- unit output hundreds kW to several MW
- cost below 1000 euro/kW at production scale
- 50,000 hours durability
- efficiencies exceeding 60 % electrical and 80 % for CHP.
The project's primary aim was to address the basic problems of moving from existing kW size SOFC units to units of several hundred kW to MW size SOFC power plants. The work is divided into two parts:
The first and largest part of the project targets the systems, components and sub-system challenges of large scale SOFC units in the following work packages:
- system analysis, balance of plant (BoP) modelling and validation
- System layout and integration
- Components and sub-systems
- Development of industrial scale stack
- Verification of the systems and sub-systems
- Fuel flexibility.
This system development and verification work was supported by a second part, which are packages of work examining the required infrastructure and socio economic issues that will affect installation and operation of SOFC systems. Thus these packages involve:
- fuels
- connection to grid
- safety and life cycle assessment (LCA)
- training and dissemination of information.
Three different plant concepts were investigated, all using anode recycling to avoid steam production.
The first concept (comparable to the original Wärtsilä concept) uses a catalytic burner and heats up the cold air by the cathode off-gas. This leads to a relatively big air pre-heater, because the mass flow is a bit lower on the hot side and the hot inlet temperature is relatively low (about 700 degrees Celsius). The anode off-gas is cooled by the anode inlet gas, which restricts the cooling to about 500 degrees Celsius. After mixing with anode fuel gas the operating temperature for the recycling blower is in the range of 400 to 450 degrees Celsius. Also the pre-reformer operates at a quite low temperature of about 450 degrees Celsius. So nearly no methane is reformed.
The FZJ-hot concept uses the after-burner off-gas with about 840 degrees Celsius to heat the cold air. This results in a reduction of the air pre-heater size to about 30 %. Cancelling the anode gas pre-heater (or anode off-gas cooler) increases the blower operating temperature by about 100 K to about 550 degrees Celsius. The pre-reformer temperature increases to about 500 degrees Celsius, which results in a reforming rate of about 10 %. This concept has the lowest number of components.
In the FZJ-cold concept the recycled anode gas is cooled by the incoming air to about 200 degrees Celsius before it is mixed with the anode fuel gas, which results in a blower operating temperature of 170 degrees Celsius. This requires a heating of the pre-reformer. This concept has the same number of components as the Wärtsilä concept, except for the necessity of a heated pre-reformer. But it has the lowest temperature for the recycling blower. The size of the air pre-heater is reduced to 40 % and the fuel cooler also helps reducing the size of the air pre-heater.
Adsorption of one or more contaminants over a fixed bed of specific adsorbents was selected as the best clean up technology, which requires coupling with other unit operations when the level of impurities is particularly high.
The life cycle analysis performed shows favourable environmental performances for a SOFC system in comparison with a conventional power plant. Fuel production phase strongly influences the environmental impacts of the electricity generation via SOFC. It is clear that bio-fuels can significantly reduce the environmental burdens associated with the up-stream processes. Besides, it results that, if there are not significant changes for the environmental profile of the manufacturing stage, the pressurisation of the fuel cell unit entails lower impacts then the atmospheric units, as effect of a higher efficiency. In particular, focusing on global warming, the bio-methanol solution seems highly attractive from the life cycle point of view.
- unit output hundreds kW to several MW
- cost below 1000 euro/kW at production scale
- 50,000 hours durability
- efficiencies exceeding 60 % electrical and 80 % for CHP.
The project's primary aim was to address the basic problems of moving from existing kW size SOFC units to units of several hundred kW to MW size SOFC power plants. The work is divided into two parts:
The first and largest part of the project targets the systems, components and sub-system challenges of large scale SOFC units in the following work packages:
- system analysis, balance of plant (BoP) modelling and validation
- System layout and integration
- Components and sub-systems
- Development of industrial scale stack
- Verification of the systems and sub-systems
- Fuel flexibility.
This system development and verification work was supported by a second part, which are packages of work examining the required infrastructure and socio economic issues that will affect installation and operation of SOFC systems. Thus these packages involve:
- fuels
- connection to grid
- safety and life cycle assessment (LCA)
- training and dissemination of information.
Three different plant concepts were investigated, all using anode recycling to avoid steam production.
The first concept (comparable to the original Wärtsilä concept) uses a catalytic burner and heats up the cold air by the cathode off-gas. This leads to a relatively big air pre-heater, because the mass flow is a bit lower on the hot side and the hot inlet temperature is relatively low (about 700 degrees Celsius). The anode off-gas is cooled by the anode inlet gas, which restricts the cooling to about 500 degrees Celsius. After mixing with anode fuel gas the operating temperature for the recycling blower is in the range of 400 to 450 degrees Celsius. Also the pre-reformer operates at a quite low temperature of about 450 degrees Celsius. So nearly no methane is reformed.
The FZJ-hot concept uses the after-burner off-gas with about 840 degrees Celsius to heat the cold air. This results in a reduction of the air pre-heater size to about 30 %. Cancelling the anode gas pre-heater (or anode off-gas cooler) increases the blower operating temperature by about 100 K to about 550 degrees Celsius. The pre-reformer temperature increases to about 500 degrees Celsius, which results in a reforming rate of about 10 %. This concept has the lowest number of components.
In the FZJ-cold concept the recycled anode gas is cooled by the incoming air to about 200 degrees Celsius before it is mixed with the anode fuel gas, which results in a blower operating temperature of 170 degrees Celsius. This requires a heating of the pre-reformer. This concept has the same number of components as the Wärtsilä concept, except for the necessity of a heated pre-reformer. But it has the lowest temperature for the recycling blower. The size of the air pre-heater is reduced to 40 % and the fuel cooler also helps reducing the size of the air pre-heater.
Adsorption of one or more contaminants over a fixed bed of specific adsorbents was selected as the best clean up technology, which requires coupling with other unit operations when the level of impurities is particularly high.
The life cycle analysis performed shows favourable environmental performances for a SOFC system in comparison with a conventional power plant. Fuel production phase strongly influences the environmental impacts of the electricity generation via SOFC. It is clear that bio-fuels can significantly reduce the environmental burdens associated with the up-stream processes. Besides, it results that, if there are not significant changes for the environmental profile of the manufacturing stage, the pressurisation of the fuel cell unit entails lower impacts then the atmospheric units, as effect of a higher efficiency. In particular, focusing on global warming, the bio-methanol solution seems highly attractive from the life cycle point of view.
