Combined heat and power (CHP) generation is considered as one of the best means to save energy and to reduce carbon dioxide emissions from power and heat production. The European Commission has proposed a target for the EU to double the share of cogeneration electricity from 9 % to 18 % by the year 2010. Reliable CHP statistics are therefore essential for the monitoring of the progress towards this goal.

In April 1999, the Finnish District Heating Association published a report prepared by Protermo Ltd presenting methods to calculate the generation of CHP electricity and heat in power plants. The recommendations of this report “Guidelines for Calculating Energy Generation in Combined Heat and Power Plants” were discussed in Brussels with the representatives of the DG XVII Energy, Eurostat, COGEN Europe and EuroHeat & Power. It was concluded, that the report could form a basis for revising Eurostat methodology of compiling CHP statistics, especially if the guidelines could be further simplified.

As a result of discussions with the above mentioned organisations, the Finnish District Heating Association in collaboration with Protermo Ltd applied for financing from the European Commission to prepare this manual, which presents simplified methods for the calculation of CHP electricity and heat.

The aim of the manual is to serve as a practical tool for the power companies to calculate and report CHP generation data requested by the statistics organisations of the member states of the European Union.

Summary of the Manual for Calculating CHP Electricity and Heat

The manual describes simplified methods for the calculation of CHP electricity and heat for the Eurostat statistics. The calculation methods are based on overall efficiency and Power to Heat Ratio of the power plant unit in question. The minimum amount of data that must be known from the power plant on an annual basis is the following:

• gross electricity generation
• internal electricity consumption
• heat generation (useful heat generation)
• total fuel utilisation (total fuel input)

With this information it is possible to calculate the annual overall efficiency of the power plant unit:

η = (net electricity generation + heat generation) / fuel utilisation

In the above formula net electricity generation is received by deducting internal consumption from gross generation. If the overall efficiency is sufficiently high, it can be assumed that all the generated electricity is CHP electricity and it can as such be reported to the Eurostat statistics. If the overall efficiency, however, falls short of the given minimum default values, further calculations are needed. For these calculations, it is necessary to know the amount of heat that is not generated in connection with CHP electricity generation, i.e. one has to know:

• separate heat generation

The knowledge of the separate heat generation is necessary also for the reporting of CHP heat in the statistics. When the amount of separate heat generation is deducted from total heat generation, the result is the annual amount of CHP heat. This can be used to calculate CHP electricity by the means of the Power to Heat Ratio of the power plant unit in question. The manual includes a calculation form as shown in the following page. This form can be applied for all power plant types. The actual overall efficiency and the Power to Heat Ratio of the power plant can be used in the calculation, if the values are known. Otherwise, the default values given in the calculation form can be applied.