Geothermal V. Wood Pellet & Solar

RedLady

Hi,

I dont know if this has been discussed before but can anybody tell me what are the main advantages/disadvantages of going down the geothermal route to provide hot water for UFH and DHW over a wood pellet boiler and solar panel to provide the same. They both seem to cost the same to buy initally and also to run for a year. PLus, you have the extra inconvience of ordering/storing pellets along with having to fill/clean the boiler. The solar panels with eventually pay for themselves and thus you will be able to recieve 'Free' energy.

I am torn between which one to choose.

Any thoughts??

Regards

tcoen

What suits your interior design?
First decide your heat distribution method. Do you want to use Under floor heating (UFH) or Radiators? Will UFH suit the floor coverings you want and can it be incorporated upstairs with screed or concrete floor?

This site has good info on ground source heat pumps (gshp) etc. http://www.sustenerg.org/SEBlog/
A specific installer who may answer your questions can be found at: http://www.eil.ie/
www.sei.ie also have info and your local energy agency can also give advice for info see http://www.aiea.ie/
If you get your electricity from airtricity you could have very little co2 released from your house with gshp.
There are other discussions on this site and on askaboutmoney.com on this topic, use the search function to locate them.

patrido

hi RedLady

it really depends on what you want to achieve - is it low running costs, more certainty on costs in the future, doing your bit for the environment??? It also depends on what you consider to be good value... getting your money back in 10 years would traditionally be considered reasonable. Also, if you are paying mortgage interest on the initial investment, this should really be added as a running cost. Does 400 euro per year on a 10000 investment sound reasonable?

from every point of view, the first priority is always insulation up to current building regs standard, thermal bridging, water storage, pipe lagging, etc. second priority is control of your heating system. i.e. clever controls, zoned heating, etc.

assuming you have these bases covered your heat requirement is now quite low in comparison with older houses of almost any age.

Solar:
you are quite likely to have seen solar manufacturers claim that they will provide a system that will provide 70% of you hot water requirements. Is this 70% of your DHW only, or does this include space/room heating. If it's only DHW, then your "free" energy is only saving you about 300 euro per year or even less. Take mortgage interest out and how much are you saving?

Of course if oil prices double (and most other fuels will follow to some extend), your payback period reduces somewhat, but interest rates could also double. I'm quite dubious about the value of investing in solar panels, though I do love the idea of them.

Geothermal: very high installation costs, but the running costs should be quite low. Electricity is twice the price of oil, but night rate is roughly the same as oil per kwh of energy.
If the coefficient of performance of the heat pump (COP = number of units you get out for every unit of electricity you put in) is 5, each kwh of energy costs between one and two fifths of the price of oil and it seems like good value. To avail of night rate leccy, you really need a thermal store, so add the cost of that to the initial installation.
So again the value really depends on the intial cost, and your heating requirement.

Note that air source heat pumps also seem attractive, but the COP varies with the external temperature. I've read that the COP can reduce to 2 in very cold weather, so the saving is nearly eliminated.

Pellet Stoves:
The usual criticism is that they are way overpriced, and uncertainty about supply of fuel.

Recent posts here suggest that the cost per kwh (assuming the pellets are bought in bulk) is half that of oil, and I have since seen that from other sources. Though I seem to recall that the figures on the SEI site suggested the price differential was much less.

If it really is half, then it seems excellent value. Again it's easy to work out the payback based on saving and initial investment, but one calculation I did for myself suggested payback in 7 years. They're also quite attractive unlike heat pumps They are far more efficient than the open fire they are likely to substitute, and that carries the benefit of reduced ventilation heat losses through the chimney too.

I would worry about security of supply, and price stability. Timber prices have always fluctuated a lot, and you would expect any by products of the timber industry to do likewise. Also, all other fuels (gas, electricity, even green electricity) go up in price when oil does, so it's possible wood pellets will do likewise.

Do heat pumps and pellet stoves require regular servicing? This should be added to the running costs also.