Commercial opportunities boost heat pump sector
Heat pumps bring significant benefits to the commercial buildings sector, says Mike Nankivell
Since they are part renewable, part electric technology, heat pumps can achieve far greater operating efficiencies than all electric or fossil fuel (gas or oil), combustion based boilers. Heat pumps in domestic applications have thus been recognised as being capable of helping us reach our carbon emission reduction targets not to mention greatly reducing our household heating bills. However, often overlooked is the fact that heat pump technology has been achieving this in the commercial sector for many years and more recent developments are further extending these benefits.
In the commercial sector, the pre-eminent heat pump is the air source air-to-air type, which can satisfy the space heating and cooling requirements. However, the sanitary hot water services are still, in the main, provided by secondary systems such as point of use all electric water heaters or central gas/oil fired boilers. Fortunately, this is set to change thanks to new developments in air source heat pump technology.
In the mid-1980s, Daikin Industries developed a new heat pump technology known as Variable Refrigerant Volume or VRV (with later derivatives known as variable refrigerant flow or VRF). This revolutionised the commercial air conditioning market because, for the first time there was a single system that could efficiently cool and heat commercial buildings, reducing dependence on fossil fuel boilers, which would now only be needed, in smaller capacities, for providing hot water.
What's more, rapid development meant that soon VRV could offer simultaneous cooling and heating from the same system by re-distributing waste or rejected heat that would be otherwise discharged to atmosphere.
VRV offered many other benefits apart from superior energy efficiency, it was a modular concept so proved much more flexible in terms of the space it occupied and in programming the installation works.
Electrical loads were reduced and the speed with which VRV was able to respond to demand was far quicker than any chilled water/secondary heating system. No surprise then that modular VRV/VRF overtook central chiller systems in terms of popularity in the broader commercial sector.
Before the development of modular heat pumps, most commercial buildings were cooled by air or water-cooled chillers circulating chilled water to air handling units and/or wall mounted or ducted fan coil units. A secondary heating system was required, normally a combustion based gas or oil fired 'wet' central heating system. This heating system would either use the AHU, fan coil units or serve conventional radiators, in addition to the DHW.
Chiller system applications
Certain commercial applications remain better suited to chiller systems, for example in large areas with a single temperature set-point or where response times are less critical, spaces with larger cooling loads or very high ceilings.
So, has chiller development learned any lessons from the success of VRV? Heat pump chillers have also been available for some years, but at a premium that hindered their success.
Such chillers could only operate in cooling or heating. In heating mode, there were limitations and in certain conditions a secondary heating source would still be required to fully satisfy the heating or DHW demand.
This has been largely resolved with the more recent introduction of inverter technology (which VRV/VRF had adopted years earlier). Inverter technology enables the heat pump chiller's compressor/s to be boosted, in more extreme conditions, with a frequency increase that exactly follows the required thermal load, resulting in a wider operating range and reducing or eliminating the need for secondary heating.
Heat recovery heat pump chillers manage to get a little closer to VRV/VRF capabilities because, the chillers offer cooling and heating as before - but - in cooling mode, heat absorbed from the conditioned space and from the compressors, instead of being rejected to atmosphere, is recovered and directed to a second heat exchanger. The recovered heat energy can then be used in areas calling for heating or transferred to a thermal storage facility for sanitary hot water.
In this way chillers can offer simultaneous heating and cooling, a common requirement in commercial buildings, at remarkably high efficiencies. The use of heat recovery should be considered in any building with simultaneous heating and cooling requirements, or in facilities where the heat can be stored for future use.
Buildings such as hotels with high year-round internal cooling loads combined with high hot water demand are also excellent opportunities for heat pump, heat recovery chiller technology. Importantly, heat pump heat recovery systems can allow for substantially downsizing or even eliminating fossil fuel, combustion based heating equipment such as gas boilers.
Modular developments continue
Not to be outdone, the development of modular air to air and air to water heat pumps continues apace.
To manage the heating and cooling and hot water requirements of our commercial buildings it's not so much a question of 'why install heat pumps?' rather than 'why consider any other technology?' No other systems offer anything like the combined energy efficiency, carbon emission reductions and cost effectiveness.
This is a fact that we in the industry trust will be acknowledged in phase 2 of the Government's Renewable Heat Incentive scheme.
// The author is marketing director of Space Airconditioning //
17 April 2013