Combined heat & power
Swimming pools typically use five times as much energy per square metre as offices
www.heatingandventilating.net
CHP – a holistic approach
In sites with high demand for heat, CHP continues to offer an economic option for significant energy savings, says Mark Gibbons, Remeha CHP’s national sales manager. And taking a holistic approach to system design will maximise the benefits
designed new properties will require very different commercial heating solutions. Electrification of heating is one means by which
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the government intends to move to a low carbon economy. But while equipment such as heat pumps will increasingly be used in new build projects, in older buildings there may not be the budget to upgrade the electricity supplies to meet the requirement. Equally, due to the nature of the heating system in these buildings, higher temperature heating solutions may prove to be more suitable. One technology that continues to offer a highly-
efficient, economic solution to lower cost high grade heat is Combined Heat and Power (CHP).
s the government steers the UK towards full decarbonisation of heat, it’s important to bear in mind that older buildings and efficiently-
35% energy savings
To illustrate the energy-saving potential of CHP technology, let’s consider a recent project at Penrith Leisure Centre. At this complex, installation of a new CHP system has reduced primary energy use by an impressive 35%, as revealed by recent energy data. The key to the success of this project? Adopting a holistic approach to system design and observing best practice at every stage of the project.
Feasibility
The first question when considering CHP should be, is the demand there? In fact, leisure centres are notoriously intensive energy users. Facilities with swimming pools, like Penrith Leisure Centre, typically use five times as much energy per square metre as offices, according to CIBSE. CHP is able to meet the constant demand for
space heating and hot water while keeping heat and power costs low. This made it a commercially compelling option for strategic, long-term energy and emissions savings for the centre’s owners, Eden Borough Council, and operator, GLL.
Sizing and selection
A Remeha R-Gen 20/44kWe CHP unit, working in conjunction with three Remeha Gas 310 Eco Pro condensing boilers, is generating lower cost heat and power at Penrith Leisure Centre and reducing total primary energy use by 35%
28 July 2019
Choosing the most energy efficient equipment is also key. So when replacing the old plant serving the centre, mechanical and electrical engineers Thomas Armstrong recommended installing a Remeha R- Gen 20/44kW ultra-low NOx condensing CHP unit
operating in conjunction with three Remeha Gas 310 Eco Pro high efficiency condensing boilers. Accurate sizing is crucial. CHP only delivers
savings when it is operating, hence suppliers’ repeated emphasis on the need for accurate sizing. But the system must also be designed for optimum performance. To achieve this, it’s necessary to consider how the technology will operate within the system.
Condensing the design
When pairing CHP with condensing boilers, for example, as at Penrith Leisure Centre, care should be taken to ensure that it is the lead ‘boiler’ and that the condensing boilers are not brought on too early. Typically, this means using the CHP as a preheat for the boilers so that the CHP sees the load first. In the case of condensing boilers, for full
condensing to occur – where the boilers are most efficient – the return water temperature needs to be below dew point, which is normally at or below 54°C. The location of the hydraulic connection could therefore have a major impact on the operation and seasonal efficiency of both the boilers and the CHP. And that could result in significant additional costs during the lifecycle of the system. Depending on the temperature difference, boiler
efficiency could be increased by as much as 9.5%. Even lowering the return water temperature by just 10°C would increase boiler efficiency by around 4.5%. In real terms, for a 500kW input boiler running for 4,000 hours a year at 3.9p per kWh, this 4.5%
Mark Gibbons
www.heatingandventilating.net
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