FOCUS: HEATING & VENTILATION
Guidance calls for collaboration in non-domestic heat pump applications
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The launch of CIBSE’s AM17 guidance document for heat pumps in large buildings is a welcome addition to best practices in the industry, according to Silviu Catana, specification manager at ELCO Heating Solutions. He takes a look at AM17, and what it means specifically for collaboration within the world of heat pumps in non- residential applications
or some it has to be John Lennon and Paul McCartney. For others, of a certain age, Morecambe and Wise. And for yet more: Sergei Brin and Larry Page. Great partnerships that proved collaboration can – and indeed will – change the world. It might be a cliché in business that more can be achieved by working together, but that doesn’t mean there isn’t a hefty dollop of truth in it. In our industry, if you have a look
around you’ll see that partnerships and collaborations are actively encouraged – some might say “baked in” to the regulatory framework. Take CIBSE’s newly released guidance AM17 on heat pumps in non- domestic buildings as an example. While the snappily-titled AM17 might not set pulses racing, it is actually specifically recommending collaboration and cooperation as best practice. It’s an approach that we have been utilising at ELCO for many years already – but we’re very happy to see it written down in official guidance. So, why was AM17 introduced and why is it so important? AM17 followed its well-received companion AM16, which concentrated on heat pumps in multi-unit residential buildings. AM17’s focus is entirely on non- residential buildings. When the guidance was commissioned, CIBSE said its desire was to “ensure that heat pump installations follow best practice and are delivered safely, legally and to a high quality.”
The document is wide-ranging and covers
a great deal of technical and detailed information, ultimately setting out clearly what best practice looks like. It covers various areas in depth, including the specification and configuring of systems – whether ground source or air source heat pumps – and highlights the advantages of various types of heat pump technology. The comprehensive document also goes on to look in detail at the risks and challenges associated with various installations, particularly in large buildings, as well as the impacts of heat pump installations.
Chapter six – which is what we’re focusing on in this article, looks at System Optimisation Modelling as well as the relationships between stakeholders. The guidance contained in this chapter shows the change in approach and how best practice is all about collaboration – between manufacturer and system designer, client and installer. It also is very clear on how technical data about any heat pump system
should be shared and used in the design and installation process. The detailed information on system modelling for optimum performance addresses the “performance gap” of how a system is designed on paper, versus how it works in the real world. It’s the difference between the energy estimated to be used in the design stage, as opposed to the actual energy used in the completed building. CIBSE takes the view that, where possible, metered data from comparable, existing buildings should be used to validate the energy model. And that annual energy modelling for a heat pump system should account for building-specific factors such as occupancy, equipment and operational profiles. It also recommends sensitivity studies to examine the effect of varying conditions. The guidance also makes recommendations on how a consultant should calculate system performances. Previously, a consultant would often just take a standard 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
22 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JANUARY 2023
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.
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.
Read the latest at:
www.bsee.co.uk
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