Baxi Ecogen and Building Control, 09/12/10 By Ruairi Kay
British Gas were onsite today installing the Baxi Ecogen Micro-CHP and new wet radiator system. CHP (combined heat and power or cogeneration) is the process of producing both electricity and useful heat from one source. Large scale CHP has been around for some time, but reliable micro domestic models are only starting to become available. The Ecogen unit produces an output of 1kW of electricity while providing 6kW of heat via a free piston Stirling engine. An addition output of 18 kW can be provided via a supplementary burner with no electricity generation. At the design stage we had difficulty getting estimations from Baxi as to how much electricity per year the unit would generate in this case, so in the end we used our own formula. Using our annual space and domestic hot water requirements from PHPP, (PassivHaus Planning Package) and a series of assumptions on boiler operation we have come up with a figure of 455 kWh per year electricity generation. The monitoring phase of this project we will give us vital information on how the unit actually performs. The install looks good though I am suspicious the cylinder supplied does not have 80mm insulation as per our requirements. Some trawling on the internet office confirmed my suspicions. When I initial contacted British Gas about this they claimed that they cannot get a cylinder with anymore than 50mm foam insulation and that beyond that it’s not worth adding anymore anyway! This is contrary to what I believe to be true after seeing a good presentation on the efficiency of hot water systems by Alan Clarke and Nick Grant at Ecobuild this year. This has now been resolved and the correct cylinder will be installed on this project and our 3 other retrofit projects in Crawley.
The Baxi Ecogen
We also had the Building Control officer onsite today to inspect the work. His main concerns were; the effect of the increase of 28mm on ground floor (from the Spacetherm C insulation) where the floor meets the first stair rise, the new drainage and insulation works below ground and the loading of the new plant deck in the attic. He was happy with all the work he saw, though the below ground work had all been backfilled before he got a chance to visit site. Good we have lots of photos I can send him!
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