DOMESTIC AIR CONDITIONING
The actual incentive is paying back 2.57 pence for every unit (in kWh) of heating produced with an air source heat pump. This means that on average the energy cost for heating with a heat pump is completely covered by the incentive.
That makes the system consisting in a Water Loop Heat Pump System with an air source heat pump for heat injection and dry cooler for heat rejection into the loop, quite interesting especially in a retrofit perspective, substituting just the boiler of existing systems with an air source heat pump.
It is very interesting to understand what would be the payback time for an entire substitution of a boiler with an air source heat pump using this incentive and applied to an existing WLHP system:
The average cost for a 1000kW air source heat pump plus boiler decommissioning is £95,300. Energy bill savings – incentive included (yearly) £23,100.
In just over 4 years the new installation cost will be paid back. From year 4 onwards there would be many years of four digit savings, with the average lifespan of a heat pump is 15 years.
EPC
When running an EPC assessment of a building, the proper category of heating / cooling system has to be selected.
■ Within the General Section of the assessment software we have to select WLHP - Water Loop Heat Pump System in order to define it in every area of the building where this type of system is implemented.
There is no possibility of modifying the indoor unit’s efficiencies and performance, consequently the energy consumption of the heating / cooling system is characterised just by the system in integration of the loop (injecting, rejecting heat).
This type of equipment can be chosen in the Heating / Cooling section.
■ In heating section among many available options a natural gas boiler or an air source heat pump could be selected. They are the most common options for this type of system.
■ In cooling section there is no option of selecting ‘dry cooler’ device, than the only relevant option is “chiller”. See the paragraph below on how to set it up properly.
When performing an assessment for a specific building some different options could lead to much different results. ■ If there is no option for ‘dry cooler’, a chiller could be selected instead. There is the possibility to change the standard full load and seasonal efficiency.
While usually for a modern chiller these are full load efficiency ≈3; seasonal efficiency ≈4, for a dry cooler is variable according to the temperature control strategy on the loop, but they usually are full load efficiency ≈30; seasonal efficiency ≈35.
This will model the heat rejection device accordingly. Usually a building assessment is affected heavily by: ■ Yearly energy requirement for heating. A great benefit in having an air source heat pump instead of a gas boiler could be targeted;
■ Yearly energy requirement for cooling. Usually due to UK weather the requirement for cooling is not such high, and with water loop heat pump technology the requirement for the dry cooler is most of the time negligible comparing to other energy costs;
■ Yearly energy requirement for lighting. It is not influenced by the heating cooling system, but sometimes it is quite important in terms of EPC assessment, especially for old buildings;
■ Yearly energy requirement for hot water for sanitary purposes.
In some applications it is negligible, in some not. If it does heavily affect the EPC assessment, it would be beneficial to consider a high efficiency device to produce the hot water, such as an air source heat pump.
www.acr-news.com
March 2017 53
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