Will Heinzelmann, product director at Passiv UK asks should we focus on smarter controls?

The UK will have to decarbonise domestic heating if it is to meet its 2050 net zero targets. Since those targets were first enshrined in law, heating has been the elephant in the room of the ‘big three’ areas for decarbonisation - power, transport, and heating. The transition to low-carbon power has been rapid, with emissions from electricity generation falling by more than 60% since 1990. Transport is also well on its way, with the millionth electric vehicle having been registered in January. Decarbonisation of heating, however, has been much slower.

The Government supports heat pumps as one of the main solutions, whether installed individually outside our homes or as part of larger, centralised heat networks. That’s a good thing and the right decision but decarbonisation with heat pumps depends on them running efficiently.

An efficient heat pump is one with a good Coefficient of Performance (CoP). Heat pumps are, generally, very efficient. A new gas boiler can have an efficiency of 85% if it’s set up correctly but a heat pump can have an efficiency of well over 300%. No, that’s not breaking the laws of physics - that’s because a heat pump extracts ‘free’ energy, usually from the air or ground.

The efficiency of a heat pump is determined by the flow temperature that it runs at. A lower flow temperature means a higher CoP. It’s the heat pump or its controls that determines this flow temperature.

A third of heat pumps are installed and commissioned to operate at a fixed flow temperature. That’s easy for an installer, but a disaster for your heat pump’s efficiency. The other two-thirds use a weather compensation curve - that’s some settings the installer puts in the heat pump that tell it what flow temperature to produce for a given outdoor temperature. The idea is that the colder it is outside, the hotter your radiators need to be to keep the house warm.

This is great for the efficiency of your heat pump if the installer gets the settings exactly right, which they won’t because it's an impossible thing to do. They calculate the weather compensation curve at the point of installation using the best information that they have. Probably a heat loss calculation they have produced for your home.

But that weather compensation curve doesn’t change if they get it wrong and it doesn’t adjust to new information. Nor can it look at weather forecasts or factor in how the homeowner uses their heating system. So, it's better than using a fixed flow temperature, but we can do better. That’s where smart controls come in.

The Passiv controls have been designed specifically to work with a heat pump and remove the need for an installer to set a weather compensation curve. Instead, from the moment they are installed, they learn how a home heats up and cools down, and how the heating system behaves. They also use local weather forecasts to calculate the optimal way to meet a homeowner’s comfort requirements, continuously optimising the heat pump’s flow temperature to maximise its CoP. The outcome is a dynamic weather compensation curve, and one that is always right.

The Energy Saving Trust has verified that the Passiv controls increase the CoP of a heat pump by 17% against a manufacturer’s standard weather-compensated controls.

It’s good that the Government seems to have recognised the need to tackle the elephant in the room, but maybe they’ve picked the wrong elephant. Most of the heat pumps you can buy seem similar. Perhaps it's the controls that can make the big difference.