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Seasonal Coefficient of Performance (SCoP) figure and use that for calculations relating to system design. While this works at a broader level, it ignores nuances of the building’s performance and how the heat pumps will actually perform. It’s a bit like that well-worn phrase of taking a sledge hammer to crack a nut! So AM17 guides consultants in a different direction. The CIBSE guidance
recommends that system designers should calculate Seasonal Performance Factor (SPF) for the specific building load and heat pump selections, instead of using a more “broad brush” SCoP. And that’s where the importance of collaboration is underlined in the guidance – linking nicely to the section about Stakeholders. In order to make the system, product and building specific calculations CIBSE
recommends, consultants will need to use data from various sources, and more specifically using COPs provided by a manufacturer across a range of ambient temperatures and part load conditions. This will provide an accurate Seasonal Performance Factor (SPF) for a heat pump in a range of commercial applications. The COP (coefficient of performance) shows the instantaneous performance of the machine at a specific condition (external temperature, flow temperature, machine load). However, the SPF gives the performance of the machine supplying heating energy to a system throughout a season or for a specific period of time, where the parameters required in the system vary based on: external temperature, fabric of building, thermal inertia, etc. Therefore, having such data available from a manufacturer is the most effective approach to calculating the amount of heating energy produced – and consumed – by the machine in all of the circumstances for the time period considered. Figure 1 helps to illustrate this point. Here you can see how the COP varies
significantly for identical flow/external temperatures at min/max loads of the compressor. However, not all manufacturers can provide continuous sets of data across all models and part load conditions. So, using detailed manufacturer data provides consultants with the confidence to deliver detailed calculations that suit the specific needs of their client.
Renewables
Figure 1. Variation of COP In practice, this means that manufacturers and consultants are going to need to work in tandem. Manufacturers of heat pumps will need to provide more data than they’re perhaps used to. In ELCO’s case, we already offer all of this data, which allows us to work collaboratively with consultants to deliver heating systems that are well designed and maximise heat pump output throughout the year.
By offering the consultants detailed information about the capacities and
performance covering practically all the scenarios in terms of loads and operating temperatures that they need early in the design process, and working with them throughout the design phase, we’re able to help them engineer systems which respond as expected in real world conditions – bridging the aforementioned performance gap. It’s definitely a relationship that has a win- win outcome!
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