ENERGY SAVING
Saving energy or renewing it?
Professor Dick Powell of Refrigerant Solutions discusses Energy Effi ciency in the age of renewables.
R
-emitting fossil fuels, a change that creates both challenges and opportunities for the refrigeration, air conditioning and heat pump industries, in this article collectively termed ‘thermal pumping’. When the UK becomes carbon neutral, presumably around 2050, thermal pumping equipment will be using very low GWP refrigerants, so will neither be contributing directly to global warming, nor indirectly via CO2 emissions. Thermal pumping technologies will essentially have zero TEWIs, so will energy effi ciency continue to be a signifi cant concern? My view is that answer is most defi nitely ‘yes’, for two main reasons, one economic, the other environmental.
enewable energy is increasingly replacing CO2
‘Renewable’ certainly does not mean ‘free’; energy will still have a cost, whether consumed by a large organisation or an individual household. Competition in the thermal pumping industry to provide customers with the most cost-eff ective equipment will obviously continue. As always, effi ciency against capital cost will still need to be balanced. But renewables, wind, photovoltaic, hydro, tidal and biomass together with nuclear, mainly deliver power as electricity. In the low carbon future, thermal pumping customers will be competing for energy directly with transport, industrial processes and space heating, applications currently satisfi ed by diff erent fossil
fuels each with its own separate distribution network, each representing considerable historical investment. Adapting these systems or replacing them by an up-rated national grid will cost money which will ultimately be paid for by customers through their bills, so economics will dictate that energy effi ciency will continue to be important.
But what about the environment? Despite renewable electricity eliminating CO2 emissions and reducing air pollution, like most revolutions, the renewable revolution could have undesirable consequences. On-shore wind turbines are already disliked because they intrude into British landscape, especially since many of windiest sites are in areas of great scenic beauty. Complaints about noise levels are not uncommon. Off - shore wind turbines avoid visual and sound pollution but are implicated in unacceptable levels of bird deaths. Photo-voltaic ‘farms’ are perhaps less intrusive but compete for land that might otherwise be used for food production, wildlife conservation, and perhaps biomass fuel or sustainable feedstocks for the chemical industry. The old cliché about ‘no free lunch’ certainly applies to renewables as much as it does to fossil fuels. Environmentally the number of renewable energy installations should be kept to a minimum, consistent with maintaining an acceptable standard of living.
While the thermal pumping industry can help reduce its indirect impact on the environment by progressively improving the energy effi ciency of its equipment, it can make a substantial and specifi c contribution to improving the effi ciency of space heating. In the UK, many homes and buildings are presently heated by gas-fi red, hydronic systems. Two major technologies are vying as replacements: electric heat pumps and hydrogen gas boilers. In terms of simple energy effi ciency, a heat pump appears the better bet since it can deliver ~ 3 kW of heat per kW of electrical power. In contrast, the renewable electricity could be used to electrolyse water, an ~80% effi cient process, to generate ‘green’ hydrogen, which, on combustion in a condensing boiler, will deliver ~90% of its heat content giving an overall effi ciency of ~72%, clearly about ~four times worse than a heat pump. In environmental impact terms, four times as many turbines or PV cells are required to supply the same space heating via ‘green’ hydrogen gas boilers as by heat pumps.
For new builds insulated to high standards where ventilation is perhaps more important than heating,
26 January 2021
www.acr-news.com
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