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I moved house in 2022 and the property had a heat pump already installed. On initial inspection, it was clear that the 12-year-old heat pump was very poorly designed and commissioned. This explained why my energy bill in November was over £1,000 due to several flaws in the system. The settings on the heat pump were wrong and I could see that the heat pump was struggling to manage in higher flow temperatures, for example when it’s completed a hot water cycle, which indicated to us that the compressor was failing. This was likely because it had had to work so hard due to the poor design of the system, for the past 10 years. We calculated that the heat pump was running at a COP of only 2.5 which is very poor.
Arguably the next step would be for us to simply replace the heat pump with a like-for-like but larger model or replace it with an air source pump. However, I decided that rather than simply buying another heat pump we would review and redesign their whole heating system to ensure that it met their needs and reduced my energy bills.
We started the process by doing a heat loss calculation which confirmed that the heat pump and ground connector were far too small and were the root cause of the poor performance of the heating system. The result was that the brine temperature was minus 8 which created a permafrost in the ground which created a ground heave that was lifting the slabs as much as 50mm, thereby damaging the customer's patio. There was a real risk that if left unaddressed the permafrost could have moved the foundations of the house. Having discovered that the collector was too small we decided it was impractical and costly to dig up my garden or drill a borehole
Consequently, I designed and installed Scotland’s first NIBE Photovoltaic Thermal heating system. I was already considering investing in PV, so this allowed me to incorporate both systems together. The PV-T system meant that we could increase the collector size by taking heat from the ground as well as the roof. One of the challenges this presented was that we had to run pipes from the roof to the plant room in a discreet manner. Also, PV-T systems are for new installations not to replace existing heating systems which also made it challenging. Therefore, doing this as a retrofit was incredibly challenging as we had to work around the house and old system unlike fitting it in a new build.
The heating system we installed was the NIBE PV-T system, which included 8x450W PVT battery and an S1155 12kW Nibe giving me two sources of heat for the ground source heat pump.
The result was that the new heating system runs at a very impressive COP typically of 5.0 compared to a COP of only 2.5 which the old system was running at. The system became one of the best-performing systems on heatpumpmonitor.org.
My energy bills have been significantly reduced, from £1,000 in the first November to £250 the following November despite the house running at a comfortable 21 degrees. During the winter, thanks to my battery, I can heat my home and hot water at the off-peak rate. During the summer I am almost bill-free.
Consequently, we have fitted Scotland’s first PV-T system with a battery, that gives them a multi-source heating system that is highly efficient and more importantly, meets all of my family’s needs while reducing my energy bills and carbon footprint.
