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Solar Should Complement High Efficiency Lp Gas Boiler

David Pepper, managing director of Lochinvar, looks at the implications of applying solar in conjunction with traditional lp gas-fired systems and how working with other specialist manufacturers will often be the best option.

In terms of supplying domestic hot water, solar energy has become one of the most popular renewable solutions in the industrial and commercial sector. The drive towards carbon reduction has placed a high emphasis on the selection of low/zero carbon (LZC) technologies, and applications using lpg can also benefit from their specification and use.

Careful consideration should be given to the complete system, including the use of traditional water heaters – for example, direct lpg gas-fired water heaters have been used extensively with commercial and industrial properties in non-mains gas areas over the years. Using some form of renewable energy on new buildings and major refurbishments is now a major consideration for those designing or installing heating and hot water systems. While solar systems have become increasingly popular for supplying domestic hot water, one of the drawbacks has been the perceived financial payback, with most new installations unlikely to achieve this in less than 20 years.

The forthcoming Renewable Heat Incentive should provide a further boost for solar water heating. While the new government has committed to go ahead with the scheme, the expected start date is now June 2011.

Initial plans for the scheme suggested that retrospective claims could be made, and a further announcement is expected before the end of this year, when the exact details will hopefully be published. The government is hoping this scheme will offer a strong incentive for commercial and industrial companies to invest in renewables, and this will certainly be a positive step towards reducing the UK’s carbon emissions.

Solar thermal is likely to be one of the technologies that can usually provide between 25 and 30 per cent of the annual hot water consumption for the average commercial property. The solar system will need to be integrated with a more traditional hot water system, and it makes sense to complement the solar installation with high efficiency equipment.

In commercial applications, one of the most effective ways to supplement the hot water generated by solar is to use direct gas-fired water heaters, whether they are fuelled by natural gas or lpg. Such products can be integrated with a solar system, where the solar gain will be used to provide preheated feed water. As the largest proportion of a building’s hot water demand will be generated via the traditional method rather than the solar technology itself, the selection of the primary method of generating hot water is equally, if not more, important than the solar proportion.

The use of twin coil cylinders is commonplace in residential dwellings, with the lower coil being used to transfer the solar gain, and the upper coil being supplied with hot water via the building’s central heating boiler. However, the effect of the solar gain is reduced by the indirect coil from the heating boiler and, furthermore, this indirect method of generating hot water is not as efficient as a direct lpg-fired water heater.

With this in mind, there is a strong case for using gas-fired water heaters, be they natural or lp gas models, in conjunction with solar thermal systems. Based upon the principles of low storage but fast recovery of hot water, this technology uses fuel more efficiently than an indirect system. This concept has been around for more than 30 years, and currently most water heater manufacturers are utilising condensing technology, with operating efficiencies reaching as high as 98 per cent based upon gross calorific value (CV).

Solar is still an evolving market in the UK and it appears that the heating industry is still on a sharp learning curve. For this reason, Lochinvar has adopted the philosophy of ‘partnering’ by working with specialist solar company Rayotec Ltd. Our combined expertise has already helped many companies to design and install integrated solar thermal and gas-fired water heater systems, which provide true long-term benefits.

In addition, an increasing number of contractors and heating specialists are prepared to take on the solar installation themselves, so Lochinvar is now offering products on a ‘supply only’ basis. This ensures contractors can benefit from Lochinvar and Rayotec’s joint expertise, without having to commit to an installation that could be carried out in-house.

If the Renewable Heat Incentive has the positive impact on the uptake of solar thermal that we all hope it will, this will clearly be a step in the right direction towards lowering the UK’s carbon emissions. When specifying a solar project, the integrated system and traditional method of hot water generation requires careful consideration. This approach will ensure UK buildings are truly as energy efficient as possible and are successful in reducing carbon emissions.

Contact Lochinvar on 01295 269981 www.lochinvar.ltd.uk

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