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The ups and downs of solar thermal heating

It is no secret that renewable and sustainable energy production is already providing opportunities for suppliers to generate new sales and that this will continue to increase over the coming years, says Howard Johns, Solar Trade Association chairman.

It therefore makes sense for contractors and installers to ensure that they are up to date with the latest developments, covering both aspects of technical requirements and grants available, in addition to making sure that their work is in line with the latest legislative requirements.

While a number of companies are leading the way in this area, providing training for both technical and sales personnel as well as working closely with clients, some in the industry are expressing concern that these are in the minority. And according to Solar Trade Association chairman Howard Johns, all in the garden is not rosy.

Declining demand

The introduction of the feed-in tariff for solar electric systems means that the sector is experiencing rapid growth. “You might expect the solar thermal sector to be experiencing the same sort of revolution,” says Mr Johns. “But unfortunately, it is not.”

With over 100,000 solar thermal systems installed across the UK, numbers were typically increasing at a rate of 15,000-20,000 a year, he continues. However, in recent months the demand for solar thermal technology has considerably dropped off.

“Solar technologies’ simple nature normally means they are the starting point for people considering using small scale renewable energy systems.

“Both solar thermal and photovoltaic (PV) are the most flexible of all the onsite renewable technologies and integrate easily with other technologies such as biomass and heat pumps.

“When coupled with energy efficiency measures, they can massively reduce both the bills of a property and its carbon footprint,” says Mr Johns.

He refers to the government’s financial incentives to support renewable technologies, such as the feed-in tariff launched last April. “The STA are fully in support of this scheme and can clearly see the huge benefit it is bringing to the growth of the electricity generating (including PV) sector,” he says.

By using a MCS-registered installer company and product, the customer is paid for every unit of electricity generated. Combined with a reduction in the amount of energy required, solar PV really makes financial sense, he adds.

Mr Johns also refers to the Renewable Heat Incentive, intended for launch next April, although this date is now in doubt (see News, p1). “We hope more details on the scheme will be forthcoming as part of the ­government’s Comprehensive Spending Review due towards the end of October,” he says.

There is concern about the government’s commitment to solar thermal technology, however, following the closure of the Low Carbon Buildings Programme. “This lack of clarity and the sudden change in policy over the support measures means that industry has been left in limbo,” he says.

“Without the launch of an effective RHI, there will most likely be a loss of jobs across the sector as companies involved purely in solar thermal are having either to restructure or to fold.”

A recent survey conducted among STA member companies gave a very strong message that confirmation is urgently required on RHI if trust in the industry is to be restored, investment in growth resumed and increased employment realised.

“The ideal home of the future will feature a solar thermal system surrounded by a PV array allied to another back-up heat source,” says Mr Johns.

IntaEco commercial director Cynthia Fisher agrees that solar thermal heating technology is very much in vogue. “It’s easy to see why - costs are not prohibitive (typically around £4,800) and maintenance costs are very low. Systems can generate up to 70 per cent of a home’s hot water needs from sunlight, and an average domestic system can reduce carbon emissions by up to 0.75 tonnes per year.”

With reports of rapid rises in interest, Ms Fisher also says the details of the government’s Renewable Heat Incentive will be eagerly received.

Although the boiler scrappage scheme has ended, she points out that there are still Warm Front grants available to the value of £6,000, aimed at people on lower income or benefits when a renewable energy solution like solar thermal is recommended.

Warm warning

There is, however, one cautionary note, she says: “Things sitting in the sun can get very hot indeed in a fairly short period of time.
“While this is great news for anyone planning on harnessing the rays as an eco-friendly heating solution, it means that water temperatures within solar systems can get up to 100 deg C - a staggeringly high temperature for a domestic heating system to deal with,” she says.

“As severe scalding can occur at water temperatures as low as 40 deg C, clearly the water from a solar system cannot be delivered directly to a shower, tap or bath without some form of thermostatic mixing.

“New Part G legislation introduced in April now makes it compulsory to use an anti-scald valve, also known as a thermostatic mixing valve (TMV), for any new or refurbished bathrooms.”

As the maximum inlet temperature of standard TMVs is 85 deg C, they are just not suitable for use within a solar heating system.
The solution is to integrate a solar anti-scald valve specially designed to function across a wider temperature band, says Ms Fisher.

hese have enhanced performance to accommodate the high flow rates needed to blend a high differential in hot and cold, bringing outlet water to a safe temperature in practical quantities.

“Correctly fitted and regulated, solar valves will provide years of sound service,” she says. “The same advice of course goes for all other components within a solar thermal system - do make sure you specify correctly and check carefully at the point of fitting.

“Fitting the incorrect part could cause serious damage - not just to an unsuspecting end user, but also to our industry’s reputation.”