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Wales Energy Crops Information Centre

Electricity production and CHP

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One of the options open to energy crop growers is supply of fuel to larger energy users such as Aberthaw Power Station.  Long term contracts are often on offer and these can be an attractive option to some growers. However, in order to access this market there are stipulations that crops are grown within a given radius of the main supply company, as transport costs over greater distances make supply economically restrictive as well as reducing the environmental benefits of the crops.

There are also options for growers to generate their own power. Combined Heat and Power (CHP) systems can generate electricity and heat. Heat and electricity can be used locally or the electricity can be sold back into the national grid.  As heat cannot be transported it must be used in adjacent buildings.  CHP systems are best suited to enterprises with large heat and electricity requirements.

Combined heat and power systems are more efficient users of fuel than heat only systems, with potential for costs to be around 30% lower than conventional electricity and heating. Typically 50% of fuel is converted into heat and 30% into electricity.

Small-scale gasification CHP systems are available from 50 kW in size. In a gasification CHP system biomass is converted into a fuel gas.  In addition biogas produced by anaerobic digestion can be used to fuel certain CHP systems.

There are a number of engine options for powering the generator in CHP systems, including external combustion (EC) engines, internal combustion engines and fuel cell. Stirling technology (EC-engine) now encompasses biomass as a fuel and is an example of an option for small-scale systems under 150kW.

The suitability and economic feasibility of each option is largely dependent upon the scale of operation and the demand for electricity and heat, with the economic benefits increasing in line with increasing usage and scale of plant. Economic considerations can be accessed via the economics page.

Key points

  • The electricity produced is eligible for renewable obligation certificates.
  • Economies of scale: The smaller the scale of operation the larger the unit costs are.
  • Domestic scale biomass CHP is still a developing market and not yet fully commercialised.
  • Wider CHP opportunities can be accessed by farmers/communities working together to form co-operatives. This has the benefit of taking advantage of the economies of scale that exist for both the local heat use, and the electricity.
  • The technology is progressing all the time and micro-systems are entering the market.  One of the smaller systems currently on the market is a biomass fuelled generator  provided by Talbotts, this system has been adopted by Harper Adams College in Shropshire and may be suitable to larger farm, or small community enterprises.