carbon limited

I saw on zerochampion that GTC Europe have got together with Cambridge Consultants to produce a single-house micro CHP unit. The key difference between this unit and the Mircogen or Whispergen is that it’s based on a Rankine cycle engine rather than a Stirling engine.

It’s got a similar electric-to-heat output ratio as the Whispergen and Microgen (1 kWe/9 kWt) but they claim that it operates at high efficiency at part load. They also say 2000 units will be available for sale by the end of this year at around €5000 each. It’ll be impressive if they hit the release target as the unit seems to have come out of nowhere.

The unit is basically a small, efficient steam engine. They’re using a scroll compressor (like you find in a heat pump) to put an organic working fluid under high pressure before heating it and releasing the vapour through a turbine to generate electricity.

They’re not taking part in the Carbon Trust field trials but insist they’ve done their own trials and that the results have been very positive. We’ve been here before. It would be nice to have an objective assessment, but it doesn’t look like there will be any before the unit goes into production.

Without impartial trial data or actual installations it’s hard to say whether GTC’s micro-CHP will be able to overcome the problems that the other single-house CHP units have run into. Will the controls and warm-up time allow it to track the intermittent loads of a single house? Given the size of the heat outputs, how will it reduce carbon for anything other than a poorly insulated house with high heat loads and a long heating season? Will people stomach the price tag? If they’ve addressed these issues and we can see the results, I’d like to start including them in suitable projects.

As an aside, they seem to be targeting some interesting markets, including Thailand. I’m not sure what good a 9kWt micro-CHP engine would be in a house in the tropics, unless maybe you’re using heat-driven cooling such as an absorption chiller. Given recent experience in the UK, I’m concerned about technology that’s adopted on the momentum of green marketing despite its appropriateness. I hope that isn’t the case here.