056 HPM 0415

HPM April 2015

Got a story? Ring us on 01732 748041 or e-mail twood@unity-media.com RENEWABLEENERGIES Unvented solutions for renewables Jason Hobson, managing director at Gledhill, the cylinder specialist, looks at some unvented solutions for heat pumps and solar... While thermal stores are often the focus of discussions about the best ways to maximise heating and domestic hot water from renewable technologies, including uncontrolled heat sources, for solar and heat pump installations, unvented cylinders are not only an alternative approach but may even be a preferred choice. A cost-effective solution that offers the installer a familiar product and installation techniques with renewables compatibility is an unvented cylinder. This can be the ideal choice for hot water only solar and heat pump installations. However, it’s essential that a robust and high quality cylinder is chosen that has been specifically designed for the renewable technology input installed. WHY SPECIFY UNVENTED? Unvented cylinders that have been designed for use with renewable technologies are a practical solution. By positioning the cylinder as near as possible to the heat source (solar or heat pump), it helps to reduce heat loss and maximise heat transfer for a more energy efficient and higher performance configuration. As a result, unvented cylinders are an excellent choice for both new and retrofit installations, especially where slimline options are available to provide space saving advantages. In addition, because unvented cylinders are mains fed, and, therefore, do not require a cold water feed tank, the removal of the feed tank in the loft space can enable the specifier to select a horizontal unvented cylinder for the installation to utilise the available space. This enables homeowners to free up more usable space in the house by positioning the cylinder away from the living area. Whether it’s a less mainstream product like a WWW.HPMMAG.COM horizontal unvented cylinder or a standard unvented solar or heat pump model, one of the biggest advantages of unvented cylinders as the UK continues to embrace renewable technologies, is that the heating and plumbing sector is familiar with unvented cylinder installation techniques. That familiarity equates to faster and more straightforward installations - an ideal scenario for both homeowners in a retrofit scenario and residential developers with tight deadlines for each phase of a scheme. HEAT PUMPS The latest Renewable Heat Incentive (RHI) accreditation figures (relating to installations from April to December 2014) demonstrate there is an increasing appetite for heat pump technology, with those across ground and air source heat pumps for new and legacy accreditations amounting to 51% of all accreditations. Heat pump technology provides a great source of sustainable energy, regardless of the time of day or year, but the lower temperatures generated by heat pump installations require a higher flow rate through the cylinder to maximise heat transfer from the input. It’s essential, therefore, that unvented cylinders for heat pump installations have specially designed coils to increase that flow rate. The configuration needs to be completed by an immersion that will be activated automatically to bring the water temperature above 60ºC and pasteurise it for safe use. The RHI accreditation figures for April to December 2014 demonstrate that legacy installations make up the largest proportion of solar installations and often an unvented cylinder provides a ideal replacement for an 56 APRIL 2015 HEATING & PLUMBING MONTHLY existing hot water cylinder. However, just like heat pump installations, solar installations require a specialist unvented cylinder with a solar coil that will maximise heat transfer from the solar circuit to the stored water. Once again, the installer should consider whether a standard, slimline or horizontal model should be used and this depends on the design of the property. For retrofit installations where there was a regular hot water cylinder, a standard or slimline solar unit will provide an ideal replacement. A horizontal model positioned in the loft, meanwhile, offers optimum space saving benefits positioned closest to the energy source. It is also possible to use an unvented cylinder as a single system solution combining both solar and heat pump energy by specifying a cylinder which incorporates both solar and heat pump coils. TRIED AND TESTED While the unvented cylinders manufactured for solar and heat pump installations are specialist products for the renewables sector, best practice specification and installation considerations relating to all unvented cylinders apply here too. It’s important to use a well-insulated unit to minimise standing heat loss and a lightweight model will be lighter to transport, easier to manoeuvre round site and provide load bearing advantages. Clever design features developed to aid speed and ease of installation will also help to underpin installation integrity and Gledhill has invested heavily in R&D to drive innovation in unvented cylinder design. To ensure both quality and service standards are met in the cylinder manufacturing industry, the Hot Water Association has introduced a Charter Member scheme. The Charter offers consumers quality assurance, product satisfaction and confidence in the manufacturer, that it will deliver a service beyond just supplying the product. As uptake of renewable technology continues to grow, the options for configuring the system are also developing. Unvented cylinders provide a bridge between familiar domestic hot water installations and a low carbon, sustainable future. enquiry number 144 Gledhill’s Stainless Lite unvented hot water cylinder maximises the lower temperatures available from the heat pump


HPM April 2015
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