Solar Thermal Systems
Whether brought about by obligation under CRC, by financial incentive through RHI or by prompting DECs and EPCs, businesses are actively reducing their carbon emissions and improving energy efficiency. In commercial buildings, energy audits are resulting in improved building fabric and air tightness measures. As space heating and domestic hot water requirements typically represent the greatest energy demand, this is resulting in the predominant heating load shifting from space heating to domestic hot water. Capturing latent energy to pre-heat the mains cold feed to a direct fired water heater is a most effective use of low to zero carbon (LZC) technologies and solar thermal energy is a prime example of how an LZC solution can be integrated into a building services system.
The role of the collector array is crucial to the performance and longevity of solar thermal system components, and there are several options that can provide a perfectly matched solution when designed for a specific application or location.
Glazed Flat Plate
Glazed flat plate collectors are the most familiar design having been on the market for many years. This collector type is usually installed at an inclination between 20 and 45 ° to ensure optimum performance. With this in mind they are suited to installation on a pitched roof or with specific angled mounting frames for flat roof applications and in this situation spacing of collector rows should be considered to avoid inter-row shading. As a guide, the ratio between stored water volume and the area of the Glazed Flat Plate collector array should be 50 litres per square meter.
Direct Flow Evacuated Tube
Evacuated tube collectors employ vacuum sealed collector tubes which reduce thermal losses, thereby making them a most efficient method of generating solar hot water, even in wet and windy conditions. The solar transfer fluid flows through each tube, hence direct flow. The collector comprises a number of tubes inserted into a manifold, allowing the rotation of each tube to meet the desired inclination. This flexibility and space efficiency enables the collector to be layed flat on a flat roof or even vertically on a building façade.
Similar in appearance to direct flow evacuated tubes, the heat pipe collector uses a dry pocket connection and condenser bulb principle, enabling individual tubes to be replaced without draining down the system offering lifetime repair and maintenance savings. Each pipe contains a small volume of evaporatorfluid, and to allow the heat pipe evaporation cycle to operate the collectors should be installed with a minimum inclination of 20°. In leading edge models, the heat pipes contain a device which, in the event of low hot water demand and continued collector heat gain, prevents the condensed content of the pipe from leaving the condenser bulb. This feature, which provides protection from overheating and its consequences, makes such heat pipes ideally suited to buildings with low summertime hot water demand or irregular demand patterns such as schools and sports facilities.