Energy efficiency
the National Grid, providing certain criteria are met.
If your building is suitable for CHP, then it is worth considering an upgrade. CHP saves money when it runs; a boiler costs money when it runs so we want that to be switched off and the CHP to be on. The ideal applications are those with large domestic heating requirements. In a large care home, the expectation would be to run a CHP 24 hours a day in colder weather, dropping to 12-14 hours a day at warmer times of the year. This gives an average running time of 18 hours per day throughout the year or 6700 run hours per year. Cost savings could be up to £50,000.
The environment
When choosing whether to operate CHP, the environmental impact of local co- generation should also be considered. Carbon savings have long been an advantage of CHP and can still be achieved, but that is changing because grid supplied electricity is getting much cleaner. There has been a strong downward trend in emissions from electricity production since 2014 due to increases in the use of wind and solar power and the closure of coal fired power stations. However, on average, CHP provides a carbon benefit over the year, although the actual intensity fluctuates both daily and seasonally.
In the future smart controls will adapt CHP run times to ensure it operates when it is most carbon advantageous. For a CHP that runs for 14 hours per day, for example, the smart controls will ensure that the 10 hours when it does not operate align with the clean grid periods and not the period when carbon intensity is at its highest.
Even so, we recognise that the value of carbon savings with CHP will continue to fall in comparison to previous years. Instead, attention is now turning to nitrogen oxides (NOX
) savings.
A by-product of the combustion of hydrocarbon fuels, NOX
are a major
contributing factor to poor air quality, the most toxicologically significant being a combination of nitric oxide (NO) and nitrogen dioxide (NO2), which can cause lung irritation and respiratory infections as well as being linked to cancer, asthma, stroke and heart disease.
Although all CHP with a catalytic converter is cleaner than the grid, taking into account electrical efficiency, on average the wider CHP industry produces the same NOX
emissions as large scale
power generation. The downside for CHP has been that historically carbon-based
28
Comparing CHP to other local energy generation technologies shows that it costs less to run than a heat pump. It is also easier to install than a PV and results in greater savings
power generation has been located outside major urban areas, but the drive for low carbon buildings is bringing even more potential emissions into our cities. Most CHP is likely to have a slight positive impact on air quality nationwide, but because those installations will typically be in urban/residential areas, that CHP will have a negative impact. Therefore, localised NOX
emissions from
‘dirty’ co-generation is becoming a concern. Where CHP is used to offset condensing boiler run hours, if the CHP is dirtier than the condensing boiler then local emissions are greater. Despite air pollution and NOX
mainly
arising from road traffic (half of NO X pollution in major urban areas is
attributed to vehicles) emissions from decentralised energy production are now being seen as a contributing factor. It is therefore of great importance that the NOX
to the future, can help improve local air quality.
At the end of the day, the building and its use should drive decision making, but for the care home, perhaps the greatest advantage of all is the assurance that residents will have continuity of comfort through the provision of heating and hot water. It is in this role that CHP delivers a business critical need in the care home environment.
Reference 1. Centrica Business Solutions. (2018) The Energy Advantage Report, June 2018.
TCHE
emissions from new CHP units are lower than they are from condensing boilers if they are to have a positive effect. An assessment of NO X
emissions from
CHP manufacturers undertaken by Adveco showed wildly fluctuating figures, ranging from 64 mg/kWh to 596 mg/kwh and older units were far worse. Despite heat recovered by CHP being considered NOX
neutral, it is vitally important to recognise that there is a considerable difference between dirty CHP and the latest generation of low-NOX
CHP. Conclusion
Comparing CHP to other local energy generation technologies shows that it costs less to run than a heat pump. It is also easier to install than a PV and results in greater savings. CHP can result in energy cost savings for a building, so it always makes sense to run it if you already have it and if you don’t, to install it in the right type of building. Upgrading to CHP in mid to high occupancy residential care homes will provide a good payback period and be a solid investment over a 10-year period as long as a guaranteed maintenance schedule is put in place. Selecting the right CHP can also provide carbon savings and more importantly, as we look
Bill Sinclair
Bill Sinclair is technical director for Adveco, which also trades in the UK as AO Smith Water Heaters. Bill has almost 20 years’ industry experience in mechanical engineering. Having joined the company in 2011 as technical manager, he now has responsibility for product and system development as well as managing the bespoke design and engineering teams. Prior to joining Adveco, he was installation manager at Millside Heating Services Ltd and technical manager at Rinnai UK Ltd.
www.thecarehomeenvironment.com • March 2020
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