Solar heating saves money and proves a company’s green credentials but don’t ignore the primary heat source, warns David Pepper of Lochinvar.
Heating engineers and contractors are under what seems to be continued pressure from the commercial end-user to install renewable systems. As far as hot water supply is concerned, undoubtedly the most popular appears to be solar thermal.
For the contractor, it is relatively easy to install in conjunction with a traditional system and as the hot water supply can be a significant proportion of a building's energy use, it is logical to make use of what is a truly renewable energy source. It is also highly visible which could account for the dramatic rise of solar thermal during the last few years.
Use of solar as an energy source for hot water provision should continue to be encouraged but that is not the complete picture. It is important to bear in mind that the maximum a solar installation will provide is between 25% and 30% of annual hot water consumption for the average-sized commercial property such as a hotel, school or leisure centre.
More thought needs to be given to the traditional and primary source of hot water generation than the solar proportion.
An excellent way of providing a reliable, economical and efficient supply of hot water
With the drive to be green, sometimes this isn't always the case and building owner/operators could be forgiven for thinking renewable technologies are the only answer to their future energy needs and the quest to conserve fuel and reduce carbon emissions.
Heating professionals may be faced with having to convince customers that the selection of the traditional equipment is of equal, if not greater, importance.
Traditional boilers and water heaters are not considered to be trendy but direct gas-fired options are still an excellent way of providing a reliable, economical and efficient supply of hot water.
These products have been used successfully in a range of commercial applications for more than 30 years and most manufacturers have condensing models which further improve operating efficiency and reduce carbon emissions. Such products can, of course, be installed as part of a package which includes solar thermal.
The principle of using solar gain to supply hot water is that the collector array will be connected to a pre-heat storage cylinder. Despite low temperatures in the winter, up to 30 degrees Celsius water temperature can be delivered with higher levels achievable during the summer. As the primary water heating source burns less fuel when heating pre-heated water, fuel savings can be made.
The use of twin coil cylinders is commonplace in domestic applications, with the lower coil being provided by the solar gain and the upper coil being the indirect heating system supplied via the heating boiler. Cost considerations and space restriction are probably the main reasons why twin-coil cylinders are utilised but this is not the best method of capturing the maximum amount of solar gain as the upper coil will, in part, reduce some of the hot water generated via the solar gain in the lower coil.
Unfortunately such systems are sometimes used in commercial applications where, in addition to the reduction in solar gain, the primary method of hot water generation is indirect and as such less efficient than a direct gas-fired system. The lesser-efficient primary water heater system will reduce and could even eliminate the cost saving and carbon reducing benefits.
This could result in disappointment for the end user when the system does not deliver all they had envisaged. Many local authorities now insist a proportion of future energy be generated on new buildings via renewable sources before granting planning permission.
Clearly these authorities would have some questions to answer if the forecast renewable contributions and carbon emission reductions do not materialise. This underlines the importance of paying close attention the primary hot water source.
It is important to reduce carbon emissions but it is vital we ensure effective use of renewable systems to help achieve this. But if care is not taken, we are doing a disservice to our customers by not giving due consideration to the primary source which is an integral part of building energy usage.