Careful consideration should be given to the complete water heating system, including the use of traditional fossil-fuel water heaters, says David Pepper
Using some form of renewable energy on new buildings and major refurbishments is now a major consideration for specifiers.


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. Hot water from solar gain will be used to provide pre-heated feed water to the gas-fired water heater installation. 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 this primary source of 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 this indirect method of generating hot water is not as efficient as a direct, gas-fired water heater.
With this in mind, there is a strong case for using gas-fired water heaters in conjunction with solar thermal systems. Based upon the principles of low storage but fast recovery of hot water, this direct gas-fired technology uses fuel more efficiently than an indirect system.

This concept has been around for more than 30 years, and most water heater manufacturers are now using condensing technology, with operating efficiencies reaching as high as 98 per cent based upon gross CV.

Lochinvar has adopted the philosophy of 'partnering' by working with specialist solar company Rayotec. An example of the Lochinvar/Rayotec partnership is the installation at Hartcliffe Community Centre in Bristol. The centre wanted to use renewable technology.

A 12 solar collector installation was designed in conjunction with two Lochinvar LBF300 gas-fired water storage heaters. The use of solar energy in providing pre-heated feed water will reduce fuel consumption and consequently carbon emissions.

However, an increasing number of contractors and heating specialists are prepared to take on the solar installation themselves, so Lochinvar is now also offering products on a 'supply only' basis. In addition, the company has expanded its solar offering with the addition of flat plate collectors alongside the existing evacuated tube solutions.