Combined heat and power (CHP) oers organisaons huge energy and carbon saving potenal in a welldesigned, wellmanaged system. Mike Heord, Remeha CHP’s General Manager, oers advice on how to achieve opmum performance from this low carbon technology.

carbon footprint. In buildings with a high requirement for heating and hot water, CHP is increasingly seen as a strategic solution that can generate significant long-term financial savings.


How so? By generating heat and power simultaneously on site, CHP can deliver significant primary energy savings of up to 30% and an emissions reduction of up to 20% (see panel). Given the high achievable efficiencies, payback of CHP can be rapid – less than five years in our experience. While CHP can be installed as part of a standalone heating system, it is frequently paired with high efficiency condensing boilers to enable the system to perform to its full potential. Yet still there are reports of underperforming CHP units that fail to deliver the anticipated money or carbon savings. So how can building services professionals ensure that CHP installations deliver maximum performance and benefits?

Check running hours

The first key consideraon with CHP is that it will only operate eciently and generate cost savings if it is running constantly at full output. For this reason, an inial feasibility study is required to assess whether the building has enough demand for heat and electricity.

The first key consideration with CHP is that it will only operate efficiently and generate cost savings if it is running constantly at full output. For this reason, an initial feasibility study is required to assess whether the building has enough demand for heat and electricity. As a general rule of thumb, a minimum of 4,000 operating hours is usually required to achieve an acceptable return on investment from CHP.

In existing buildings, obtaining gas and electrical energy usage will help profile the demand. If in doubt, good suppliers will have a dedicated technical team on hand to advise and help with these requirements.

Size maers

Sizing of the CHP is the next step. It’s essential to get the sizing right to minimise the total costs of energy supply for the site.

The best approach is traditionally to match CHP heat output to the building base load, with condensing boilers operating in tandem to meet peak heat demand.

In existing buildings, analysis of gas and electrical energy usage will help to profile the demand. Get the sizing right

Top ps on maximising eciency

u4,000 minimum operating hours usually required for acceptable return uGet the sizing right – match CHP thermal output to the building base load uReturn water from lowest temperature point on heating system uData connection for remote monitoring


HP is becoming a popular choice as organisations and businesses look to reduce their building’s energy costs and

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MAXIMISING CHP EFFICIENCY Getting the best from the equipment

and a CHP unit running continuously will generate low cost, low carbon electricity as a by-product of producing base load heating. But oversize the CHP and the unit will shut down during periods of low thermal demand, resulting in frequent stop/start cycling. Is there a shortcut to accurate sizing? Unfortunately, there’s no straightforward way to size CHP as each building will have unique requirements. But the Golden Rule is that it’s always better to undersize than oversize. Again, suppliers will be able to provide valuable technical support, so tap into their expert knowledge from the outset.

Hydraulic connecon

The success of any heating system will always depend on how well it is designed and CHP is no exception. Taking a holistic view is essential to help optimise the operation and seasonal efficiency of each component and the system as a whole.

For this reason it’s important to understand how to get the best from the equipment. When pairing CHP with condensing boilers, for example, it’s important to remember that these boilers operate most efficiently at low return temperatures.

Connecting the CHP to the common

return supplying the boilers will increase the return temperature. While this is not an issue with non-condensing boilers, it will reduce the efficiency of condensing boilers.

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. Configuring the system so that the CHP is connected to the common return from the heating system will ensure lower return temperatures and higher efficiency.

Depending on the temperature difference, boiler efficiency could be increased by as much as 9.5% (see chart). Even lowering the return temperature by just 10°C would increase boiler efficiency by around 4.5%. For a 500kW input boiler running for 4000 hours a year at 3.9p per kWh, this 4.5% increase would equate to an annual saving of £986.05 – or £14,790.81 over a 15-year life time.

Lifeme eciency

Once installed and operational, a long- term CHP maintenance contract is put in place to enable the supplier to monitor the system. This helps guarantee optimum performance and operational life.

CHP suppliers offer remote monitoring or visualisation of CHP units via a data connection – usually to either a data connection or mobile network. CHP engines are maintained on a running hours’ basis so remote monitoring is a valuable tool that alerts both user and service team when a service is becoming due. Furthermore, with 85% of reported CHP faults able to be corrected and reset remotely according to our experience, visualisation can reduce downtime, inconvenience and unnecessary costs. Yet while remote management should be

CHP is effectively a micro power station, but more than twice as efficient.

Remeha’s CHP technology

burns natural gas to generate useful heat on site, while also providing electricity to supplement or replace the grid supply.

Instead of rejecting the ‘waste’ heat to atmosphere like traditional power stations, the heat generated by CHP can be re-used in the heating/hot water systems. And by generating electricity on site, businesses can produce electricity that is less carbon

part of the service plan, all too often this is not possible as there is no data in place. So it’s vital to ensure that visualisation is discussed at the early stages to enable faults to be corrected or even predicted – and therefore avoided. As system designs grow more complex, bringing together designers, contractors and suppliers at the early stages is increasingly important to share collective knowledge and best practice. CHP is a case in point. This low-carbon technology has the potential to deliver huge energy and carbon savings. And by adopting a bespoke approach to the design of each project and encouraging greater collaboration from the outset, we can help optimise CHP performance and achieve the maximum benefits.

uThe Remeha RGen CHP range, from 5.5 – 2,000 kWe, is the sustainable soluon to providing highlyecient heat and power to commercial buildings that demand significant, consistent heang and electricity.

uCondensate chart. Energy and carbon savings from CHP

intensive at lower gas prices. In this way, CHP helps businesses and organisations meet the energy efficiency requirements of Part L of Building Regulations while providing impressive cost, carbon, competitiveness and energy resilience benefits. Mike Hefford, Remeha CHP’s General Manager, heads up a dedicated team of CHP specialists who provide support at every stage of the project. Remeha’s CHP range spans 5.5kWe to 100kWe. To arrange a Remeha CPD on CHP, contact


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