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Getting the best out of green solutions

Renewable and low carbon technologies should be hailed as the saviour of commercial heating, helping users to reduce their carbon emissions and cut energy costs. However recent research suggests that in some cases, green technologies are falling short of these high expectations – often due to incorrect specification – with users left counting the cost. Sean Green explains why sizing and specification are key to optimum savings

Many organisations are switching to new technologies to help them cut carbon emissions, energy bills and meet the increasing legislative demands made on their business. Heating and hot water can account for a considerable amount of a commercial operation’s energy use, so it makes sense that this should be as efficient as possible to help achieve green targets. But while more and more companies are investing in combined heat and power (CHP), solar thermal and heat pumps, they are not all reaping the benefits.

According to a benchmarking exercise carried out by CarbonBuzz (the RIBA and CIBSE platform for tracking energy use in buildings from design to operation) many new builds are using between 1.5 and 2.5 times the amount of energy predicted during their design. A major factor contributing to these gaps between actual and predicted energy use is carbon saving technology that does not perform as it was intended to, and in particular technologies incorrectly specified for the application.

These statistics may paint a somewhat gloomy picture but of course they are not representative of every installation. There are lots of examples where notable carbon and operational savings have been achieved using low carbon or renewable technologies, but these results are usually for projects where the building type, product technology and installation have all been properly considered.

When things go awry, we usually find an application where renewable or low carbon technology has been incorrectly specified, which will significantly hamper the technology’s performance and the energy savings achievable. In too many cases, the ‘10 per cent for luck’ rule is used, leaving users with larger plant than is actually necessary. In addition to being more expensive to purchase in the first place, bigger plant does not mean better performance – in fact, often the contrary.

One issue that we are seeing a rise in is the use of large-scale CHP units where they are not appropriate. CHP is a well-established technology which is becoming very popular in Europe – it doesn’t depend on weather or ground conditions or other unpredictable factors and can generate both heat and electricity. Unlike many other renewable solutions, it can be easily retrofitted, making it a flexible solution for existing or new buildings.

To work effectively, CHP needs to be kept as small as possible. Micro-CHP units offer a versatile heating solution for various sized applications, particularly as they can be used in cascade to meet the demands of larger properties when required. We would always advise that a CHP unit should be sized so that it is capable of meeting a building’s base load heating requirements on its own; to maximise its electrical generation potential. By ensuring the CHP’s engine is working hard, users benefit from continually generated low cost, low carbon electricity as a by-product of producing the base load heating. Oversized units do not have enough demand to run continuously and therefore the amount of electricity produced will be well below the customer’s expectations.

In fact, the closer you can match the user’s demands to the capabilities of the CHP, the better efficiencies achievable. A CHP unit should run for at least 4,000 hours per year for the best return on investment, so is not recommended for buildings with low demand for heat such as offices or shops. Better paybacks and CO2 savings are achieved in buildings with year-round demand for heat, such as apartment blocks, sheltered housing, fire stations, care homes and hotels. These users will also benefit from regular Renewable Heat Incentive (RHI) payments too if they have a qualifying installation, to further improve their returns.

CHP is a reliable and proven technology capable of delivering great savings and reducing a building’s carbon footprint.

With careful specification, considering the needs of the end user and how they will use their equipment, CHP can help commercial customers maximise energy savings and their return on investment. Low carbon and renewable technologies are here to stay and we must ensure they perform to their full potential to encourage more businesses to make the switch to a greener future.

// The author is the senior product manager at Baxi Commercial //

8 July 2014

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