Friday, 22 July 2016

Small is beautiful

A year after CIBSE installed a micro CHP system in its Balham headquarters, we look at a report by Dr. Alem Tesfai, Fuel Cell Systems Research Associate, Dr. Anastasia Mylona, CIBSE Research Manager, and Professor of Chemistry at the University of St Andrews Prof. John Irvine to see how it's been performing and what we've learned about the technology, in this week's blog.

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
In recent years, this concern has intensified the search for more reliable and sustainable energy sources. Fuel cells have been proposed as the most efficient way to convert Hydrogen, or hydrogen rich hydrocarbons, to heat and power at the point of use for decentralised stationary power systems and for transportation. The efficiency of fuel cells stems from the fact that, unlike the conventional fossil fuel power stations where there are many intermediate energy conversion steps, the conversion of the chemical energy in the fuel cell system takes place in a single step. Avoiding these intermediate steps reduces the irreversible losses of energy to the atmosphere and enables fuel cells to achieve efficiency in the region of 40–60%.

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
  
CIBSE has installed a SOFC based micro-CHP system for testing and demonstration purposes. Fuel Cell micro-CHP for residential and commercial building is a new technology in the UK, but well established in other markets such as Japan and Germany. Due to commercial secrecy and low production volumes, information on historical and current prices for fuel cell micro-CHP is not widely disseminated. However based on our research in UK and other markets, currently 1kW fuel cell micro-CHP cost about €16000 at the moment, the equivalent of around £13000. Achieving mass production and technically advanced durable product, is expected to reduce the price, possibly to about €6,000/£4,500 by the year 2020.

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


No comments:

Post a Comment