Heat Pumps Today

12 Richard Warry, Managing Director of ICG Heat Pumps looks at the growing commercial heat pump market C0 2 Heat Pumps – The only way to heat high demand hot water Heat pumps are becoming the go to solution for heating and hot water in commercial buildings. This is largely stimulated through the energy & carbon targets required to achieve building regulation compliance, the public sector decarbonisation scheme (grant scheme for the public sector) and, end users desire to achieve their zero carbon/net zero targets. When it comes to high demand hot water, we at ICG Heat Pumps always recommend C0 2 heat pumps. Applied correctly, they will be 5-6 times lower carbon than gas boilers and circa 20% cheaper to run. In comparison with conventional heat pumps, they will be circa 40% lower in carbon and running cost. What is a C0 2 Heat Pump? Like conventional heat pumps, C0 2 heat pumps absorb heat energy from the air (or water) and use this and pressure created by compressors to evaporate a refrigerant that in turn is used to transfer heat energy to water. It is important to be clear that a C0 2 heat pump is a heat pump which uses C0 2 (R744) as the heat carrying refrigerant. Those from outside the industry will have heard “heat pumps” and “C0 2 ” in the same sentence. We have been asked before; “aren’t all heat pumps C0 2 heat pumps?” All heat pumps will help reduce operational carbon emissions; the heat pumps we discuss here have C0 2 in them. Achieving the best efficiency When selecting a heat pump solution for any commercial application, many things should be considered to ensure an effective and efficient outcome. To achieve the lowest energy, lowest carbon and lowest running cost solution, it’s important to understand that with conventional heat pumps, the higher the water flow temperature that is required, the lower the efficiency will be and vice versa. June | July 2023 C O MM E R C I A L H E A T P U M P S This is true for all heat pumps, although much less applicable in relation to heat pumps which use C0 2 (R744) as the refrigerant. C0 2 (R744) heat pumps efficiency is much less effected by the flow temperature, whether targeting 50,60,70 or 80˚C the efficiency does not reduce much. What impacts the efficiency of a C0 2 heat pump most is return water temperature. To give a good efficiency, the return temperature needs to be below 40˚C – this will result in efficiencies/SCOP’s (seasonal coefficient of performance) circa 3. To give the best efficiency, the return needs to be below 31˚ C most of the time, this will result in SCOP’s circa 3.7 – 4. Ensuring a low return temperature, requires a system to be configured and controlled very differently than a conventional heat pump hot water system. Using a number of buffers (2-3) piped in series will help increase the likelihood that the return temperature stays low. Monitoring the temperature and operating the heat pump and water circulation pumps at the right time are crucial and this is where contractors and designers often get it wrong. We service other suppliers’ equipment and have seen many C0 2 systems in the field that are returning poor efficiency and this is usually due to the return temperature being too high. A challenge for the trade It seems that the complexity is a real barrier and so we’ve chosen to provide a support solution for C0 2 systems. We fully design, supply and install the parts of the system which are usually a challenge for the trade. The only connections that the M&E contractor needs to make are; mains cold feed and secondary return and flow to the building – the same as what they would do with a boiler. Our controls and hydraulics control stratification in a single buffer vessel and will ensure that the return temperature to the heat pump is always in the sweet spot which gives good efficiency. Why is it that the return temperature effects efficiency most? I’ve tried to simplify this bit so hopefully anyone can understand it. Let’s go back to our school science lesson for a moment. To understand why C0 2 ’s efficiency is most effected by return water temperature, we need to understand/remind ourselves of two relevant bits of science: 1. Before we change the temperature of any matter, we need to either dry it (before heating it) or hydrate if we intend to reduce its temperature. This removal, or absorption of moisture is described as latent heating or cooling. This part of the state change is not measurable on a thermometer. Once dried or hydrated, we can then start to affect the temperature of the matter – this part of the state change is termed as sensible heating and cooling – this is where we see temperature change on a thermometer. 2. Most of us know that all matter can exist as a solid, liquid or gas. What is less known is that there is a 4th state, which is known as the plasma state. If we continue to heat and pressurise any matter, it will eventually transform to a plasma. Plasma has no latent property (there is no moisture in it) and so any increase in pressure or absorption of energy will result in an increase in temperature. Richard Warry, Managing Director of ICG Heat Pumps