Opportunities for combined heat and power
Here we explain the installations, applications and efficiencies of different CHP technologies. There is information about heat demand, locations for CHP, management, maintenance and the future of CHP.
Combined heat and power (CHP), also known as co-generation, refers to the simultaneous generation of usable heat and electricity. Fuel efficiency can be further increased through cooling using an absorption chiller. This set up is referred to as 'tri-generation'.
Heat demand primarily determines the scale of the scheme. There are three questions that need to be answered when determining the potential opportunities for CHP:
1. Is the heat density high enough for CHP?
The Energy Saving Trust suggests that at least 55 new dwellings per hectare are necessary for a financially viable scheme. Also, a recent study for the Department of Energy and Climate Change (DECC) suggests a minimum heat density of 3,000kW per square kilometre per annum. Densely populated areas such as town centres, high density residential developments or groups of large energy users in industrial estates are well suited for district heating CHP. To assist in identifying opportunities, DECC has developed a heat map for the UK. Many sub-regional and local areas have more detailed maps.
Heat map for the UK - on the DECC website
2. What are the levels of heat demand to be served by the scheme?
Heat demand is determined by the use and energy efficiency of buildings. Older buildings tend to have a higher heat demand, although this can be reduced by fitting insulation and other improvements. The scale of a CHP scheme can be determined by the total heat demand of the end users to be connected to the CHP heat network.
3. Are heat demand patterns appropriate for CHP?
Consistent heat demand is best for CHP. However, in most cases heat demand fluctuates throughout the course of the day and the year. The most viable opportunities will be in those situations in which a mix of uses (commercial, public and residential buildings) can be served by a CHP plant. Inclusion of buildings, such as hospitals, hotels and swimming pools will provide large and steady demand for heat over 24 hours.
More information on heat demand is available in on the LDA Design website:
Availability of space
Sufficient space is required for the plant and related infrastructure. The space available will have implications for the scale of the scheme and the chosen fuel source. For example, biomass requires storage space, while natural gas can be supplied via the gas grid, if available, requiring no on-site fuel storage.
There may be other physical barriers to the development of CHP and district heating including:
- railway lines
- major highways
- large buildings
Although a way around these barriers can normally be found, it is likely to increase project costs and may even make a project unviable.
Management and maintenance
Micro, mini and packaged CHP units can be left to run without much need for user interaction. Routine maintenance is required at least every 1,000 hours of operation. This needs to be carried out by qualified technicians. Installers will be able to provide all the necessary information.
Industrial and district heating CHP require operational staff and annual routine maintenance of the plant.
CHP in the future
There are emerging technologies which could be economically viable in the near future - these include fuel cells and organic rankine cycle.
1 May 2012