Where there's no mains gas and electricity costs too much, you might think coal is the only way to power homes. Not so, as Jenny Hampton reports – geothermal energy can be a cheaper alternative, even in existing properties
Two pensioners lugging buckets of coal in from the yard seems like an image from a bygone era. But it was an everyday reality for tenants on the Chy An Gweal housing estate in Ludgvan, Cornwall – and not because their landlord was too mean to install central heating.

In the extremities of the county there is no gas supply. Electricity and oil are expensive, so there was no alternative to old-fashioned coal boilers – until now. Penwith Housing Association has come up with a way to install a heating system based on geothermal energy, something that had only been used for new-build housing.

For some time, the association had been looking for an alternative energy source to heat the 14 bungalows for elderly residents it manages at Chy An Gweal. Senior architectural assistant Denys Stephens explains: "Solid fuel is a real drawback for the elderly. It's difficult to handle, and the dust and ashes it creates are far from ideal.

"But of the other fossil fuels, the only one that provided what we consider 'affordable warmth' is oil, and even that is becoming very expensive to install."

So Penwith turned to geothermal power, which uses natural heat from underground sources (see "How does it work?", below).

The association already had some experience of this: it installed a ground source heat pump system in a new-build development in Marazion, Cornwall, in 1998. But putting it into existing properties was another matter.

"This system normally uses underfloor heating when it's put into new build," says Stephens, "but that would be far too difficult to install in an existing property, so we are using specially designed radiators."

Penwith Housing Association wanted to make sure it had tenants on board from the start, not least because they would need to learn how to use the new system.

"We had a meeting in April last year with all the residents and explained our plans," said Stephens. "We did a presentation with Powergen, which provided heat pumps and technical support. The residents were keen – the prospect of a clean and cost-efficient heating system was very welcome."

Tenants have responded positively. Peter Birtles lives on the estate with his wife. He says they are happy to be getting a new heating system. "It will save lugging the coal around and get rid of the dust and ashes the coal creates, which is a pain in the neck. They say this is cheaper, which is good because we're both on a pension."

The system works differently from traditional heating in that it's most efficient if it's left on for longer. Stephens explains: "The radiators only get up to about 60° centigrade, compared to 80° for gas central heating, so giving it a quick blast for 20 minutes won't get the best out of it."

Clearly, the new system will take some getting used to. To help residents adjust, the association is sending an energy adviser to all the affected houses once the heating is installed, to guide residents in its use. It will also provide a telephone advice service when the system is up and running.

The practicalities
The project was partly funded by power supplier Powergen, says Stephens. "I put together a funding bid with Powergen, which was very detailed and took a long

time to produce. It's about the size of a telephone directory. But it was worth it because we got £47,000." Penwith district council gave the project £25,000 and the government-sponsored Clear Skies fund helped too.

Difficulties were encountered soon after work began on site in mid-December: the drilling hit the water table 70 m down. Luckily the contractor was able to deal with the problem without damaging homes. Now there's a tanker standing by, passing water from the drilling rig to tarpaulins containing the mess. Instead of drilling one 70 m bore hole, two were drilled at 35 m each.

Delays were also caused by the need to take residents into account. "Usually when this system is installed, you're drilling on a building site. It doesn't matter how much mess and noise you make. But we were working in people's gardens and homes," says Stephens. "Health and safety was very important: the drilling area had to be sealed off. Paying attention to these things did delay the project, but we wanted to get it right."

Each bungalow takes a week to convert – two days for drilling and four to five days for the plumbing. Work should finish by April.

Clear Skies funding requires sharing information with others, and a number of associations are also eager to develop geothermal systems. Humping coal buckets around could soon be consigned to the past where it belongs.

Cost of heating (per kWh)

  • Smokeless fuel 6p
  • Oil 2.5p
  • Ground source heat pump 1.5p

How does it work?

The ground source heat pump works by absorbing the warmth from the earth. Underneath the top soil, the earth is a consistent 12°C across the UK. Penwith drills one or two boreholes in the gardens of the houses, 70m deep in total. A flexible tube is fed into the holes, then connected to the heat pump in the houses. The tube’s warmth heats water in the pump, which concentrates it and uses it to heat properties.

Energy efficiency

Energy efficiency is rated through the Standard Assessment Procedure, the Carbon Index and carbon dioxide emissions. The SAP scores the energy efficiency of a home on a scale of 0 to 100, where zero is very poor and 100 very good. The CI measures how carbon efficient a building is: it is based on the CO2 emissions associated with space and water heating in a home, but adjusted for floor area, so that it is independent of dwelling size. The CI is expressed on a scale of 0 to 10. The higher the number, the better the performance. Annual CO2 emissions are calculated by the National Home Energy Rating. A representative bungalow on the Chy An Gweal estate with solid fuel heating has a SAP rating of 38, a CI rating of 1.9 and CO2 emissions of 5.7 tonnes per year. The same bungalow with the geothermal system has a predicted SAP performance of 80, CI of 7.7 and CO2 emissions of 2.1 tonnes per year.

Source

Housing Today