Low Carbon CHP (Green Certificated Gas)

A CHP engine when fed with 100 kW of gas produces roughly 35kW of electricity, 45kW of heat and 10kW of waste heat (flue gas and radiated heat). More often than not this is better than a power station which  generally has limited use for the large quantities of heat it produces and incurs transmission losses down the line.

Taking the example above at 2018 rates the cost to buy 45kW of heat and 35kW of electricity would be c £5.00.  If the same was generated by CHP it would cost c.£2.50.  Allowing £1.50 for maintenance leaves a "profit" of £1.00.

This also delivers about a 11% reduction in carbon equivalence.  This can be increased significantly if gas from the "green gas certification scheme" is used.  This is non-fossil fuel gas from sources such as anerobic digestion plants.  

When a company buys large quantities of electricity, its pays through wholesale pricing  which is banded green (nights and weekends - cheapest), amber (week days) and red (week days 16:00 to 19:00).  It is also subject to costs for the transmission infrastructure.  Knowing these factors it is possible to model different scenarios to get the optimum size and operating strategy for the CHP.   

For industrial operations it is common to have a situation where all the electricity and heat from a CHP can be used all year around with a payback circa two years. 
On retail and residential operations it is more common to have more power required than heat. In this situation it is necessary to produce a detailed heat and power model using such information as wholesale tarriffs to assess the viability of the project.   

Permission needs to be sought from the district network operator to connect such generating assets onto their networks.  All will require G59 equipment to be fitted that shuts the CHP down if the network fails.  Some may require an export limiter to prevent the CHP exporting to the grid. Some will not give permission if the local network is not capable of dealing with the fault level represented by all the connected generating loads (e.g. PV's, Wind Farms, CHP and battery systems) on the local network.