December 03, 2007

If Not Hot Water, Then Something Else?

In a recent email (after my follow-up posting about the solar-water-utility), Jeff wondered if I'd heard of heat pumps and whether they'd be a better solution than solar water panels.

They are something I'd heard of, in fact I saw one in the flesh during the tour of the AC Architects practice a couple of years back. They also had photos taken during the installation, when they sunk the boreholes for the pipework. More recently I'm sure I've heard about air-to-air heat pumps, which I imagine aren't as efficient but don't need you to dig deep holes in your garden.

It isn't something I'd considered with respect to the Green Utility (I can't call it the Solar Water Utility now, can I?) and I'm not going to invest any more time looking into it now, but it's a good idea.

However, today the House 2.0 blog has a post about some experiments that Barratt have been carrying out with Manchester University which give some interesting data points for anyone who would be building the Green Utility. Not taking into account inflation (or presumably other possible energy price increases), they've calculated the payback period for a number of green technologies:

Domestic wind turbines
Although in theory these are a useful approach, with the current technology (possibly the electrics side, rather than the wind "capture") in practice they aren't any use.
Photo-voltaic panels
A £4,500 solar electricity generation system would take 37.5 years to pay for itself
Ground source heat pump
Not as efficient as makers claim, but still worthwhile. A £7,800 system will reduce a home’s carbon emissions by 62% and has a payback period of 15 years.
Solar hot water
They didn't work out the payback period for solar hot-water but did comment that, although they heated water to much higher temperatures, the evacuated tube collectors didn't really provide any benefit over flat-plate collectors, so weren't worth their extra ~£1,000 cost.
Micro CHP (Combined Heat and Power - units that generate both heat and electricity)
No payback figures on these either, although they give figures for the power generated during the year's testing. It might also be worth reading another House 2.0 entry about micro CHP which comments on a report casting doubts over their validity in domestic situations.


Posted by Adrian at December 3, 2007 11:10 AM | TrackBack

This blog post is on the personal blog of Adrian McEwen. If you want to explore the site a bit further, it might be worth having a look at the most recent entries or look through the archives or categories over on the left.

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If you could install Human Beings 2.0 into the House 2.0, I think you'd crack the problem and the world might be a better place.

Posted by: Richard Madeley at December 8, 2007 12:05 AM

I got a flyer through the post from some crowd called "Solar Direct" seem to do solar hot water systems but don't give much information about it on their website:
(though they do predict the imminent end of the world).
Much more interesting, though, is the American company of the same name:
who actually mention things like price and power output.

Posted by: Malcolm at January 17, 2008 06:01 PM
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