With recent advances in currently avaliable SOFC micro-CHP technology, the use of fuel cell micro-CHP systems has the potential to be an efficient and reliable way to provide heat and power in office buildings. In early 2015, CIBSE acquired and installed a Solid Oxide Fuel Cell (SOFC) micro CHP system at its headquarters in Balham, London; a converted and recently renovated Victorian town house.
The increasing demand for industrial energy due to economic growth in developing countries, as well as increasingly energy-intensive domestic lifestyles, is posing a serious environmental challenge as well as a financial one. The problem of whether these competing demands for energy can be satisfied in a future of shrinking fossil fuel resources and global warming is of serious concern. This is especially true in countries like the UK where domestic and office heating is a major user of electricity, and it's something CIBSE has been addressing recently with its codes of practice on Heat Networks and Surface Water Source Heat Pumps, but could new technology hold the key?
|CIBSE's Balham HQ in 2015|
Combined Heat and Power (CHP) is the simultaneous production of electrical and useful thermal energy from the same primary energy source such as oil, coal, natural and liquefied gas, or solar. A variety of micro-CHP systems are currently available, or under research and development. Some of these micro-CHP systems include steam turbines, reciprocating internal combustion engines, combustion turbines, micro turbines, Stirling engines and fuel cells. Fuel cell systems have become the focus of interest due to their high electrical efficiency, and their ability to provide a low heat-to-power ratio means the system can run at high electrical and thermal efficiency throughout the year.
Though early in market entry, fuel cell micro-CHP systems for residential and small commercial applications are the focus of interest as the prime mover technology for micro-CHP systems. These products could be used to meet the electrical and thermal demands of a building for space heating and domestic hot water and, potentially, for absorption cooling. In comparison with all the other existing technologies, SOFC-based micro-CHP systems would have a better performance. With its high electrical efficiency, over 50%, and low heat-to-power ratio it offers significant benefits, effectively supplying the total electrical demand of a building throughout the year.
|The two 1.6MWe natural gas CHP engines at |
The Pimlico District Heating Undertaking
Several Fuel cell micro-CHP products were compared, with the main criteria chosen being performance and reliability, as well as availability and the supplier’s previous experience. Although overall system performance and viability was compared, there was no independent data to compare any of the fuel cell micro-CHP systems. Therefore the selection process was mainly based on the company’s ability to supply and maintain the system. System upfront cost and a good technical support system were also factors for choosing the product.
The micro-CHP system generates 1.5kWh electricity and about 200 L/day of hot water, reducing both heat and power bills. The high electrical demand at CIBSE HQ of 25 kWh means that the electricity generated by the SOFC-micro-CHP system is all consumed and there is no need for exporting to the grid. Also, the 200 L/day of hot water generated from the system is used to cover most of the 250 L/day domestic hot water demand at CIBSE HQ.
Based on the experience gained at CIBSE there are three key issues that need to be considered before embarking on the installation of the SOFC micro-CHP system:
- The base load power requirement of the building (the minimum level of electricity demand)
- The domestic hot water requirement of the building
- Can the system be safely and efficiently integrated with the buildings current system or will it be a replacement to the current system?
|Unused electricity can be exported to the grid|
The system providers can help in developing a business case which will consider the heat and power demand of the proposed building. It is critical to explore different options for plant layout with as many system installers as possible with the aim to minimise the installation time and cost.
Key requirements for the SOFC micro-CHP installation:
- Natural Gas: The building will need to be connected to a mains gas supply
- Electricity: The building will need to be connected to the electricity grid at all times – as the electricity that is not used is exported to the grid
- Water: The building will need to be connected to mains water
- Internet: Connection to the internet is required for unit control/monitoring