Wednesday, September 8, 2010

Heat pumps, the solution but also the problem

If I could be permitted to comment on the BBCs choice
of picture, it would seem that the ground loop
is far too shallow!
8 Sept 2010: Report in the BBC Website - reporting on Heat Pumps, in the Science and Technology section from an Energy Saving Trust report. 47-50% of a house's energy demand is in Space Heating, 22% in Hot water.
  They say that Heat pumps are the way of the future, especially for people off the gas grid and looking to manage without oil, or to manage with electricity only.
  However, they also say that too many heat pump installations are done poorly, many installations are difficult to fit into existing houses, the companies in the UK are still fragmented into different operators (eg, most UK heat pump suppliers don't do the plumbing, electrics or the hole drilling, the customer has to find those); related technologies like underfloor heating are not always suitable; and existing Heat pump installation are not being sufficiently monitored for their efficacy and efficiency.
   It seems that in other countries, like Sweden, the industry is more holistic, so you the customer are not left flailing about trying to Google for hole drillers and plumbers with GSHP knowledge, like we were in 2006. In the UK, there are few people off the gas grid.

See also, the New Energy Focus article on the same story.

I ask: "What is the motivation for people to have heat pumps? is the only reason because they are off the gas grid, and they see the heat pump merely as a boiler replacement? Do they think that because the heat comes from the ground or air, they can actually waste more energy than before when they used oil? Or do they recognise that if they tune their lifestyle accordingly, they can use the heat pump for a genuine carbon saving? And if they think that, do they want to see their heat pump working more efficiently, and perhaps even capable of benefitting from an augmentation system like sunboxes?"

I admit that when we first had ours installed, we thought "Great, we are getting free heat from the ground, four times as much as we burn, so can have plenty of hot water etc" As time went on, it became clear that the consumption was far more than anticipated, the ground chilled significantly during the winter, and over the first two years, the COP appeared to be an average of 2.65, not the hoped for 4. The COP in a stand-alone lab condition may well be 4, but the COP that matters to us is the performance in practical working application, in which there are many heat transfers and longish pipes, and there are system losses. In a house, heat loss from circulating pipes helps with incidental heating, but heat loss in a trench between your house and the garage (if you keep your heat pump there) is a total loss.
   I have heard of people putting Heat pumps (usually air source) into buildings too large for the capacity of heat pump, and not well enough insulated, and then doing no energy monitoring thereafter. And, as I found with mine, there are things you can and perhaps need to do to make it work more efficiently - lifestyle adaptations as well as technological fixes. Don't believe salesmen who mention COP above 3! And DO MONITOR the consumption!

3 comments:

  1. Me and my husband just had a very professionally done heat pump installation for our rural property. The main reason that we wanted to stray away from traditional skirting radiators was because my excema acts up terribly considering how poorly and sparsely they distribute heat. With the heat pump installed, my itching has subsided considerably. I can understand the cost analysis for people who simply want one to save money though!

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  2. Hi Sarah. I guess from what you say that you used underfloor heating? or are you using your existing radiators, but topping the heat up with a wood burning stove? We are in an urban area, connected to the gas grid, but for me it was an article of faith to manage with renewal energy somehow. Have you thought of adding a solar thermal panel to augment the activity of your GSHP? and is it based on a horizontal or vertical ground loop?

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  3. if you choose our underfloor heating packs then you'll also need to factor in the cost of insulation board, screed and heating controls, as well as an electrician's call out and labour charge - our tradespeople costs guide has some typical jobs and charges to use as a benchmark for underfloor heating packs.

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