Carbon Savings

Carbon savings associated with microCHP result from offsetting the carbon emissions which would otherwise result from electricity consumed from the grid.

The electricity supplied by the grid has an associated carbon intensity, that is for every kWh or electricity supplied to the meter of a property there is an associated emission of CO2. For the average kWh supplied from the grid, 0.43kg of CO2 is emitted into the atmosphere; this figure is made up of all the different types of generation, from nuclear base load, through gas, to oil and coal and renewable.

MicroCHP typically generates electricity at times when the occupants want heat and this coincides with the peak daily demands for electricity. At these times the electricity grid ramps up so called marginal generation plant which is a mixture of gas, coal and oil fired power stations. This marginal generation has a much higher carbon intensity closer to 0.8kg CO2 for every kWh delivered to the meter. Now comparing this to the carbon intensity of electricity produced from a microCHP product which is typically 0.25kg CO2/kWh significant savings in carbon emissions are possible.

Example.

A typical heat led microCHP such as a Stirling engine or Kingston’s organic Rankine cycle may have a carbon intensity of say 0.25kgCO2/kWh of electricity produced, given these devices generate at peak times, then we can compare to peak marginal central generation plus losses of say 0.8kgCO2/kWh.
So if a microCHP produces 2000kWh or 3000kWh of electricity p.a. it would save: 2000 x (0.8 -0.25) = 1100kgCO2 or at 3000kWh generated, 1650kgCO2.

When compared to say a household electricity consumption of 4000 kWh p.a., this time if we use the average UK grid carbon intensity of 0.43kgCO2/kWh we could say that an average households electricity consumption would result in emissions of 1720kgCO2 p.a. or if using comparable average marginal generation carbon intensity of 0.69kgCO2/kWh then this would be 2760kgCO2 p.a.

Using the figures above, this suggests microCHP can substantially reduce the carbon emissions resulting from typical household’s heat and electricity consumption. As there a several important variables, from the house size and heat demand to the carbon intensity figures used in the calculations, exact figures will be determined from specific cases,  however, even if a range of values are used, the annual household carbon saving will be significant.