Pitfalls of heat pump retrofit in high temperature heating systems

Pitfalls of heat pump retrofit in high temperature heating systems

The transition toward a decarbonised economy requires the electrification of the existing gas load. 

In other words, we need to deliver space heating through electricity. The application of H2 to replace natural gas in its entirety comes with its own economic and engineering challenges, which we will cover in one of our upcoming posts. 

The application of electric heating would require a lower investment for the consumer but the grid is not designed to take on the national gas load. 

Therefore, for space heating applications, the use of heat pumps would reduce the amount of electricity needed to offset natural gas. This is because they use reduced power to extract heat from the external air working with a seasonal coefficient of performance (the average yearly efficiency of the system) that in the north of England could be around 2.5. 

Therefore for each watt of electricity used by the heat pump, the heat pump will deliver 2.5 Watts of heat.

In existing buildings, retrofitting gas or electric resistive heating equipment with heat pumps comes with its own challenges. 

These challenges need to be prepared for if you want a successful installation of a heat pump:

1) Space – the power density of heat pumps is much lower compared to that of a boiler. Therefore, at parity of thermal output, heat pumps require a much larger space for their installation. This means that you need to consider if you have available external room to install a heat pump in a position relatively close to your existing heating plant room.

2) Noises – No matter how quiet your heat pump is it will add background noise to the existing ambient levels. In dense urban environments demonstrating that the heat pump will not exceed the existing noise levels could be a critical issue to overcome to get planning permission approval.  This issue can be resolved by adding noise dampers around the heat pump but this will increase the project cost.

3) Engineering – Heat pumps work most efficiently when delivering heating water at relatively low temperatures (30-60°C). Depending on whether the heat pump will support the existing system taking over the boilers when the external air T stays over a certain level or it replaces the gas boilers entirely, there are several engineering aspects to consider: availability of power supply, turn down ratios, distribution systems, capacity or radiators/fan coil units, controls, access for maintenance and so on.

Decarbonising your heating system is not something that should be done overnight and certainly not without due consideration and planning.

 At Watts-ON Consultants we would recommend monitoring the way your building uses heating energy and how your HVAC systems operate to assess what would be the optimal size (in terms  of output and dimensions) of your decarbonised solutions. 

The monitoring would also identify opportunities to reduce the building load in operation, therefore, lowering the capital investment needed to replace your existing heating system. 

Our Fault Detection and Diagnostic and metering platform, Watts-ON, is the perfect tool to plan and support decarbonisation projects and monitor the operation of the new systems to make sure that decarbonisation is delivered successfully and at minimum cost, especially when, at the moment, the use of a heat pump will not have a financial payback.