air source heat pump - Viability over oil

Furts

anotherbaldrick wrote: »

If you do that you will not be having windows with trickle ventilation and will therefore have to install an in/out fan ventilation system with heat reclaim or the house will soon smell like a sumo wrestlers jock strap

A good point, but not always true.

I do not tick the box for an average home - by this I was picturing a typical three bed semi.

My home has copious trickle vents, which are used to no pattern, a chimney, enormous roof ventilation, and there is no ventilation system or heat reclaim. The house is large, detached and exposed. My heating costs are minimal, but the boiler exists as do the radiators so at times they are used.

In addition sometimes I use the boiler to give a top up boost to the hot water cylinder - it is far quicker than using electricity.

As a rule, three mini oil filled radiators keep the house up to temperature, and times like today none are needed. The boiler is just to give a boost usually when the wind is breezy. Low temperatures and calm conditions do not give the same requirement, but the boiler might be used - it depends how long the low temperatures last.

In lieu of the boiler I could buy another mini oil filled radiator - but this is another item causing clutter and it has to be stored in the summer. But this backs up my point - the boiler and radiators are not required, but they are a convenient, quick form of heating.

In essence one reads about eco features, new types of heating and the German concept of Pasiv Haus. These are worthy items but in the real mse world of money saving people can heat their homes without going to these lengths and for reasonable cost.

patman99

If I had the choice between an ASHP and a GSHP, I'd go for the GSHP.
These work by circulating the water through a coil that goes down a bore-hole or is laid in a deep pit.
As the ground acts as a giant absorber of heat, the water when fed through a pipe to a depth of 30+ metres, it heats up to close on 90 deg. C.

These systems don't suffer from the issues that affect ASHPs when the temperature drops below 6 degrees.

tberry6686

As the ground acts as a giant absorber of heat, the water when fed through a pipe to a depth of 30+ metres, it heats up to close on 90 deg. C.

Don't know where these figures come from but they are way out. The average thermal gradient in the earth (for the UK) is ~35 deg C per km.

It may be that when it has passed through a heat exchanger and compressor it will reach a useable temperature for heating homes but it will not be the fluid that is circulated in the borehole.

patman99

On 'Restoration Man' there were a couple who turned an old water pumping station in to a home.
They re-used the 65ft borehole to aid the heating of the water (along with a bio-mass boiler). When George Clark asked them how well the system worked, they told him that the water temperature was raised to 65 deg. when it came back out the bore hole, thus taking the weight off the bio-mass boiler.

Also, in Manchester, they drilled a 250ft borehole to heat water for some kind of small steam-powered power plant and the water came out the pipe as steam.

Anyway, considering that the ideal temperature for a house is 20 deg., then 35 deg. is more than enough to heat a home.

Davesnave

patman99 wrote: »

On 'Restoration Man' there were a couple who turned an old water pumping station in to a home.
They re-used the 65ft borehole to aid the heating of the water (along with a bio-mass boiler). When George Clark asked them how well the system worked, they told him that the water temperature was raised to 65 deg. when it came back out the bore hole, thus taking the weight off the bio-mass boiler.

Also, in Manchester, they drilled a 250ft borehole to heat water for some kind of small steam-powered power plant and the water came out the pipe as steam.

Anyway, considering that the ideal temperature for a house is 20 deg., then 35 deg. is more than enough to heat a home.

I think you are muddling geothermal heating with ground source heating, but they are entirely different.

In geothermal, the heat comes from fissures in the rock which allow the Earth's heat from way below 250' to warm up ground water, such as in the hot springs at Bath. That sort of heat isn't available just anywhere, which is why hot springs are rare in this country.

Ground source heat pumps work in almost the same way as air source, but draw heat from relatively cool soils, sub-soils and rocks instead of from the air. Unlike air, these ground sources shouldn't go below zero in the UK, hence their advantage.

You can stick coils for ground source vertically into the ground if there isn't much space, but if you own a field, it's probably cheaper to go horizontally with them.