RSS feedsWhat have you been up to?
I've been busy having one of those ground loops and a heat pump put in.
A what now? Heat pumps and ground loops? They sound like something
the kids might be doing at their discos and youth clubs. Or round the back of
them.
To you maybe. In the real world, they are a system of coiled or curved loops
that transfer heat from the ground to buildings. It's a cleantech thing, but
hardly a new or particularly cutting-edge one. In fact, they've been around for
50-odd years, and there are already a lot of them out there.
How much are they then?
Not cheap, in fact it costs a lot more than a standard boiler. Your entry point
is about £6,000, but that's for a house and if you're looking for something for
work they are likely to be a lot more expensive. But although they are pretty
pricy to set up, in the long run they should save you plenty of cash. Some
estimates suggest that when installed in an electrically heated home, a ground
source heat pump could save almost a grand a year on heating bills alone. What's
more, they are reckoned to be four times more efficient than oil and gas boilers
and six times more efficient than air conditioning units.
And it saves you carbon too?
Yes, indeed. Almost seven tonnes of carbon dioxide a year for that average
electrically heated home.
What's the deal then? How does it work?
Basically, a mixture of water and antifreeze is pumped around an underground
pipe, absorbing heat from the ground as it goes.
Wuh?
Think of it as a refrigerator in reverse. While the loop in the white box in the
kitchen draws the cold through it, the one under the ground draws in heat,
flushing it through a pipe. A compressor is then typically used to save or boost
the heat.
What's a compressor?
It's like those humming pipes on the back of the fridge. It takes the warmed
liquid and, um, compresses it as and when it needs to, making it warmer still.
Doesn't that require energy though?
Yes. It's not a zero-carbon technology, but the amount of power required is
small change in comparison to that used by a conventional boiler. The
Energy Saving Trust says: "
The efficiency of a ground source heat pump system is measured by the
co-efficient of performance (CoP). This is the ratio of units of heat output for
each unit of electricity used to drive the compressor and pump for the ground
loop. Average CoP over the year, known as seasonal efficiency, is about 3-4,
although some systems may produce a greater rate of efficiency."
Again, wuh?
In English, that means that for every unit of electricity used to pump or
compress the heat, three to four more units of heat are produced. Add in the
lower maintenance bills and you have one extremely cost- and carbon-efficient
means of heating a building.
How do you get the heat into the building?
In much the same way as a conventional boiler system. You can use the heated
pipes for underfloor heating or use it to power your radiators. Although in the
case of the latter you may need a slightly larger radiator than you are used to,
but if you're talking about offices, that's not really a problem. The fact that
most of the heat can be conducted under the floor also means that trendy,
open-plan, cubicle hellholes can be heated really efficiently.
So it's good for homes and businesses then?
Indeed it is. The US Environmental Protection
Agency (EPA) called geothermal heat pumps, as the technology is also known,
one of the most energy-efficient, clean and cost-effective solutions available –
which isn't a bad endorsement. It's an increasingly mature technology too, with
a million installations in the US. Any specialist engineer should be able to
install one, and they last for years with next to no maintenance.
Underground pipes, though? You'd have to have your garden dug up
then?
You can either have trenches dug or bore holes drilled. If you don't want to
upset the begonias the bore holes are probably the best option.
