At tepeo our mission is to become a leader in the decarbonisation of home heating. So it is painful for us to see the slow progress of heat pump adoption, with the latest update from the Government indicating that there’s been roughly 250 thousand heat pumps installed, in a total of over 27 million homes.
Heat pumps are a fantastic, mature, high-performing technology that significantly contribute to the decarbonisation of heating. The environmental impact of us using fossil fuels in our homes is well publicised, so the only reason heat pump uptake is slow can be the cost to consumers. This isn’t due to the purchase cost of the heat pump, as they are on the Energy Saving Material (ESM) list and therefore currently incur a 0% VAT rate, and are supported by the Boiler Upgrade Scheme (BUS), where up to £7500 of the cost of purchase and installation is grant funded. That’s more than enough to cover the heat pump itself and all the essential ancillary components.
So where is the cost that is deterring homeowners from upgrading from their heating systems to a heat pump? It is in the installation and the installer.
At the right time of year a well set-up heat pump married to an optimised heating system has the potential to deliver amazing results, with a Coefficient of Performance (CoP) well above 5. For this you need to go large with your emitters and pipework, remove buffers and secondary circulating pumps, and keep the load on the heat pump as consistent as possible by removing zone valves, underfloor mixer valves, and thermostatic radiator valves (TRV). In effect you run the heat pump all the time under a lowish load, just offsetting the heat loss of the house. The problem with this approach is that most heating systems were designed for the complete opposite of this, and therein lies the rub.
For decades the majority of houses have had a seemingly limitless supply of fuel for their heating system, literally on tap, and at a very reasonable price all the time, no matter when it was used. Installing a central heating system and burning mains gas, even inefficiently, enabled homeowners to warm up the leakiest housing stock in Europe to a comfortable level several times a day. Retrofitting houses with small radiators and microbore pipework to minimise disruption wasn’t an issue, as the wider system and heat source could be designed around very high flow temperatures and therefore still deliver the required heat.
Unsurprisingly a heating system designed to deliver large dollops of energy at high power in short bursts of time isn’t ideal for heat pumps that work best when dribbling energy into a house all the time at low flow temperatures. Inevitably this leads to installations where the heat pump is oversized, to give it the grunt to work well enough with the existing emitters and ensure that the homeowners don’t freeze in the winter. However this then highlights a separate issue with heat pumps, when ironically they should be working at their highest CoP, that of cycling.
Cycling isn’t unique to heat pumps, gas boilers have the same issue, in that under low loads they can’t modulate their output power low enough. So they shut down, wait a bit, then start back up again. For a heat pump cycling on and off like this has a huge effect on compressor longevity and reliability, so much so that all have an anti-cycling feature that ensures the heat pump operates for something like 10 to 20 minutes at a time, and limits the number of cycles to 2 or 3 every hour. And low loads aren’t really that low for a mid- to high-power heat pump, certainly above several thousand watts. The sort of load that you see for long periods of the shoulder heating season.
Enlarging radiators and pipework costs money, and so do the skills and experience required to design, install and configure a heating system that will unlock a heat pump’s absolute best CoP. MCS training and certification is also not cheap, and installers recoup that cost through their installations. And this is why, even with 0% VAT and a grant of £7500, homeowners still have to find many thousands of pounds themselves to replace their gas boiler with a heat pump.
However, imagine if there were a heat source that had the performance of a gas boiler so it could be plumbed straight into an existing heating system, didn’t have the reliability and longevity issues that come with cycling a heat pump, and still delivered the environmental benefits of using electricity as its fuel. Well, imagine no more, the heat source you’re looking for is a smart heat battery such as tepeo’s ZEB®.
The ZEB is built around a thermal store that can be charged with up to 40kWh of heat, enough to meet the demand of a small to medium sized house from a single off-peak charge. It can be plumbed straight into an existing heating system using the same pipework that fed the old gas boiler. It can deliver 15kW of power at flow temperatures up to 80C, coping seamlessly with changes in load as zone valves and TRVs open and close. And it can modulate its power output down to a few hundred watts to avoid cycling, although as the process of discharging the thermal store is simply blowing air through it using a brushless fan, there is no wear and tear on the fan, and no need to configure the ZEB or the thermostat to set minimum on times or limit cycling the call-for-heat.
The ZEB is available now and removing tonnes of CO2e from homes already. We’re trying hard to get the ZEB on the ESM list, alongside draught strips, loft insulation and wood fired boilers, and included as a part of BUS. Additionally, for a long time we’ve been looking at how we integrate the ZEB with residential microgeneration, so that our customers can heat their homes directly off the solar array on their roof. For us this means modulating the electrical power the ZEB uses to charge the thermal store, and matching that to the excess generation that is being exported back to the grid. We have very high standards, and it has taken us far longer to reach the level of performance we are happy with than we originally planned or expected. But we’re close now, so please bear with us just a little bit longer on all of this.
If you want to know more about the ZEB, please check out our website (www.tepeo.com), get in contact with your local tepeoPRO installer (https://www.tepeo.com/find-an-installer/), or reach out to us directly on 02070 725462.