ENERGY SAVING
Energy storage for HVACR
“The future belongs to those who prepare for it today.” –Malcolm X
UK refrigeration, air conditioning and heat pump equipment is mainly powered by a National Grid that increasingly relies upon renewable energy renewables, notably intermittent wind and photovoltaic (PV). Dick Powell asks how can the potential gap between supply and demand be bridged when the wind isn’t blowing, or the sun isn’t shining?
E
ven before renewables, electricity generation required careful management, because the output from baseload coal and nuclear plants could not be increased rapidly in response to sudden surges in load, the
classic event being the turning on of millions of electric kettles to brew tea at the end of a popular TV programme. ‘Spinning reserve’ - expensive, but fast response gas turbine generators - provided a solution. In the 1970s the Dinorwig pumped hydro-electric storage scheme was
built in Snowdonia, whereby water was pumped by reversible turbines from a lower to an upper reservoir using off -peak power, and then released through the turbines to generate power at times of peak demand. Although an elegant engineering solution which paid for itself within a few years, pumped storage does not appear to be economically viable under the UK open-market arbitrage whereby power is bought from competing suppliers at spot prices as demand varies. Increasingly important for a major power user is the option of being a
‘disconnectable’ customer who might forego at least part of the Grid supplied power at times of high demand in return for a preferential tariff when demand is low, an approach which allows the electricity industry to maximise its asset utilisation. Could this be the incentive to install local energy storage? As well as electrical energy using batteries, refrigeration and HVAC systems have the technical potential for storing energy thermally, either as cool or heat, but does it make economic sense rather than relying upon the Grid? This question has been given extra urgency by politicians promising UK
carbon emission neutrality by 2050, or even sooner, with electricity being generated mainly from intermittent renewables. Whatever the political
36 January 2020
complexion of the UK House of Commons after the December General Election, we must anticipate more regulation of energy consumption. The ban on gas fi red central heating in new-builds from 2025 has already been enacted, and it is anticipated that even for older dwellings electrically powered heat pumps will replace gas boilers. Indeed, some local authorities have already begun trialling heat pumps
in council houses. Simultaneously the National Grid will also face increasing demand from electric vehicles and anticipated increasing temperatures from global warming leading to a greater conditioning demand. The general view is that energy storage will therefore be vital to managing the future UK electric power supply. For the refrigeration and HVAC industries this will create new market opportunities to introduce systems incorporating thermal energy storage, a development that will be complicated by the simultaneous move to low GWP refrigerants as the HFCs are phased-down and ultimately out. In fact, energy storage has been an integral part of the refrigeration
industry since its beginnings in the last quarter of the 19th Century when early ammonia fridge sets produced ice for cool distribution to individual premises. ‘Ice batteries’ integrated with air conditioning installations for the cooling large buildings are already available. Even allowing the Grid to disconnect the air conditioning set in a large building for a short period allowing the temperature to rise slightly and then re-connecting when power demand drops, essentially utilises the building’s thermal mass for cool storage. On a smaller scale the Japanese ‘Eco-cute’ water heater couples a transcritical R744 heat pump to a hot water storage tank. In addition to the storage technologies already available, numerous
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