Combined heat & power
Sites with year-round requirements for electricity and high grade heat are suited to using CHP
www.heatingandventilating.net
Five steps to CHP
efficiency
Combined Heat and Power provides businesses with an affordable route to cleaner energy and long-term economic savings in buildings with a high and constant heat and power demand. Mike Hefford, Remeha CHP’s general manager, offers advice on how to achieve optimum results from this low carbon technology
efficiency measures. And improving heating efficiency brings the added benefit of helping create more comfortable buildings and increasing occupant wellbeing and productivity.
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In buildings with a high, year-round demand for high grade heat and power, Combined Heat and Power (CHP) is a cost-effective, strategic tool for long-term financial and carbon savings. By generating heat and power in a single process at the point of use, CHP can reduce energy bills by up to 30% compared with traditional heating plant and electricity supplied solely from the grid. As a result, payback is rapid and can be achieved in under five years, in our experience.
So how to ensure maximum benefits from CHP?
1. Check building demand CHP operates most efficiently and generates greater cost and carbon emissions savings if it is running constantly and, preferably, at full output. The first question to ask, therefore, is does the building have sufficient demand for heat and electricity to benefit from CHP?
Mike Hefford, Remeha CHP's general manager
or businesses and organisations, reducing energy usage makes perfect economic and environmental sense, helping reduce operational costs and carbon emissions. As a large user of energy, heating is a natural target for
4,000 operating hours is usually the minimum
requirement to achieve an acceptable return on investment from CHP. So sites like residential care homes, student accommodation, leisure centres with heated swimming pools, and schools and universities with extended hours will all benefit from CHP. Analysing gas and electrical energy usage in existing buildings will help profile the demand as part of a wider feasibility study. And as no- one knows a product as well as its supplier, it’s a good idea to involve them from the outset for expert advice on CHP best practice.
2. Get the sizing right Is the CHP correctly sized? Good CHP suppliers
will stress time and again the importance of accurate sizing. This is because an oversized CHP, designed to meet winter demand, will shut down more frequently in summer periods of low demand, resulting in a high number of stop/starts. The simplest approach is generally to match the CHP heat output to the baseload, or lowest heat demand of the building, with condensing boilers operating in conjunction to meet peak heat demand. This results in the longest running hours and shortest payback period. Unfortunately, there’s no straightforward way to size CHP as each building will have its unique requirements. Get the sizing right and a continuously-running CHP unit will generate low cost, low carbon electricity as a by-product of producing base load heating. For optimum sizing, capital and operating costs need to be taken into
consideration to minimise the total costs of energy supply for the site. Again, consulting with suppliers at the planning stage is advisable as they will be able to offer support in achieving accurate sizing.
Matching the CHP heat output to the baseload, or lowest heat demand, of the building with condensing boilers operating in conjunction to meet peak heat demand, is a simple approach to accurate sizing
3. Design for success Does getting the most from CHP mean sacrificing another product’s efficiency? Not necessarily. In a well-designed system, the hydraulic design will enable each component to achieve its highest possible efficiency. It’s important to bear in mind that CHP units operate more efficiently and for longer with lower system return temperatures. The CHP return should therefore be connected to the lowest available temperature to guarantee the longest
32 July 2018
www.heatingandventilating.net
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