Renowned for his work in retrofitting commercial heat pumps, Draper has made substantial reductions in carbon and costs in large commercial properties, using an innovative and lean engineering approach.

The award judges praised him for encouraging others to make the changes necessary for large buildings to decarbonise in a cost-effective way. ‘While we saw many great examples of leadership and development of teams, the winner stood out for his creativity and practical delivery of innovation,’ they said. ‘He clearly has a passion for the development and growth of engineering.’

British Land’s 350 Euston Road was the first large-scale heat pump retrofit in a commercial office building. The project was led by Draper who, in 2012, was working for British Land. ‘It was a really steep learning curve,’ he recalls.

British Land was on a mission to reduce its energy use by 40% by 2015. The seven-storey office building’s three gas-fired condensing boilers and two air cooled chillers were approaching the end of their life. Retrofitting heat pumps was the obvious solution, Draper says, because, like most commercial offices, this one required concurrent heating and cooling for a large part of the year.

Model geometry for dynamic heat pump analysis with surrounding built environment

‘If you have a building that needs heating and cooling simultaneously, why would you run a separate heating and cooling plant when you could run a 4-pipe heat pump unit to help improve the building’s energy performance and reduce its carbon footprint,’ he says.

A major challenge in replacing the gas-fired boilers with an air source heat pump (ASHP) is the lower temperature of the heating supply. At Euston Road, the boilers supplied fan coil units (FCUs) on the office floors with water at 70^oC. While heat pumps can now produce water at this temperature, at the time they did not. Instead, the heat pumps were designed to operate at a much more efficient system temperature of 45^oC; with the FCUs supplied with heat at this lower temperature.

The project uses a Climaveneta ASHP, which has three basic operating modes: chilled water only; hot water only; and simultaneous hot and chilled water production. ‘When simultaneous heating and cooling demand occurs, heat energy can be obtained almost for free,’ Draper says.

In 2014, ASHP technology was unable to deliver a sufficient quantity of high-grade heat to meet the heating demand when ambient temperatures were low. For the Euston Road project, when ambient drops below 5^oC the building’s gas boilers kick in to meet the heat demand.

The solution worked. ‘The additional expenditure to retrofit the air source heat pump achieved payback within a year and now saves occupiers £60,000 every year,’ Draper says. In addition, the switch to using an electric heat pump as the primary heat source, as opposed to gas boilers, is helping to reduce carbon emissions by 470 tonnes a year and improve local air quality.

Draper frequently works with Darren Coppins, of Built Physics

Ten years on and the installation is still delivering. ‘What this first project demonstrated quite successfully is the use of a heat pump as a means of recovering heat,’ Draper explains.

Having proven the methodology, Draper has continued to build on this experience and the lessons learned from that initial project, both as an employee of British Land and, subsequently, as managing director of his own consultancy, Twenty One Engineering. He says retrofitting heat pumps is more demanding than installing them in new-build projects. ‘With new-build applications, there is generally more space and it is much easier to design systems from the outset to operate at a lower system temperature of 45^oC/50^oC to maximise heat pump efficiency,’ Draper explains.

He says the challenges for heat pump retrofits include ‘restrictions on plant space using existing plantrooms, limitations on the electrical power available, and the need to provide sufficient heat to existing equipment sized to operate at a higher supply temperature’. In addition, heating demands in offices tend to be higher now than they would have been in a 1990s office, because heat outputs from computer monitors and lighting are less, and office densities are generally lower. On the plus side, with a retrofit you will have the benefit of detailed metering information from the building, ‘so there will be far fewer unknowns’, he says.

My journey from apprentice to CIBSE Engineer of the Year

Draper has gone from ‘worst apprentice’ to ‘true leader’

I started out on an engineering apprenticeship, as a tool maker for e2v. Unfortunately, I cannot stand still, so, at the age of 18, I was told I was the worst apprentice they’d ever had and I was moved to facilities, where I undertook an electrical apprenticeship.

The e2v factory manufactures semiconductors and specialised components for medical, space and industrial applications. It has Class 10 and Class 10,000 clean rooms, and 11 substations – all high-end stuff. Learning about building services on a complex scale changed my mindset and I progressed to factory service engineer.

I left e2v to work for metering company EP&T, as technical lead. Our first big win was for British Land, where I designed and installed the metering system for nine of its buildings. I subsequently drove the energy management process for each, based on the operating data.

In 2011, British Land asked me to join them as senior engineering manager of its Regent’s Place complex. With experience of operating a Class 10 cleanroom, it is easy to transfer these skills to operating commercial office buildings. For the next three years, I drove operations at Regent’s Place to make the multi-let campus one of the most efficient.

In 2012, I started work on retrofitting a heat pump to 350 Euston Road – the first large-scale heat pump retrofit in a commercial building. By 2014, I was in a more central role, advising on how more of British Land’s buildings could target net zero. I started to engage with CIBSE and the Better Building Performance Group.

I left British Land to work, briefly, for a company called Cavendish, before setting up my own company, Twenty One Engineering, to use my skills and experience to deliver turnkey solutions for clients. These included British Land, where I continue to be involved in heat pump retrofits.

I’m a big advocate for apprenticeships, because that’s the route I’ve taken. Until now, no winner of CIBSE Engineer of the Year had done a hands-on apprenticeship – I should not be the only one.

The CIBSE BPA Judges said: ‘While we saw many great examples of leadership and development of teams, the winner stood out for his creativity and practical delivery of innovation. He clearly has a passion for the development and growth of engineering. A true leader by example and a genuine practitioner of engineering leadership.’

To assess the viability of a heat pump retrofit, Draper often works with Darren Coppins, of Built Physics, to model the building and its systems. The model references the metered operational data to confirm its accuracy. When the metered energy data does not match that predicted by the model, the team must assess whether the problem is with the building or the model, says Coppins. He adds that it might be down to problems with the existing controls or excessive infiltration, or parts of the building may not be working as they were intended.

‘We can drill into that data to see if it is something that needs to be addressed with building maintenance or whether the model needs to be tweaked to factor in something I’ve not allowed for,’ Coppins says.

When all parties are happy with the accuracy of the model, it is used to assess the operation of the proposed heat pump retrofit.

For an effective heat pump installation, Draper believes designers have to start to think differently about a project. ‘The historical approach to heating and cooling design was focused on meeting peak loads, but the average temperature in the UK probably sits between 8^oC and 15^oC,’ he says.

A heat pump being craned into position

It’s a point on which Coppins picks up. ‘We’ve got very used to using gas, which can be turned on and off very easily, but a heat pump does not work like that,’ he says. ‘With heat pumps, if we size them for peak capacity their lowest turndown won’t be low enough for them to operate efficiently or, potentially, reliably.’

For this reason, Coppins says it is important to optimise the heat pump for how it will run for the majority of the time: ‘We can predict that through building physics; rather than saying this building has a peak load of 3MW, for most of the time its load might actually only be half of that peak.’ He says a smaller-sized 4-pipe heat pump – ‘with a bit of top-up’ from an additional reversible heat pump – can be used to boost the heating and cooling outputs as required, and can provide a more reliable installation.

The downside of this type of solution is that the plant has to be hydraulically separated. For his latest project, however, Draper worked with Coppins to develop a conceptual retrofit design without the need for additional kit. ‘The system has been designed to work efficiently at 50^oC, but – to meet peak demand – we’re planning to boost the heat pump system temperature from 50^oC to 70^oC,’ he says.

Innovative solutions such as this are feasible because Draper is keen to involve manufacturers. ‘Before we finalise our design, we will get the manufacturers in to have a conversation, because not every heat pump is the same and not every application is the same,’ he explains.

Inside a 4-pipe simultaneous heat pump

Another reason the team at Twenty One Engineering is able to develop innovative solutions, Draper believes, is ‘the open relationship we have with British Land as the customer and with Built Physics’.

In the 10 years since Draper became involved in retrofit heat pump installations, he says the biggest technological advance has been with refrigerant gases, because these allow higher circuit temperatures.

‘At Euston Road, we could achieve a circuit temperature of 50^oC at an outside air temperature of 5^oC. When the outside temperature dropped to 0^oC, the system only achieved a temperature in the low-40s – while, at -5^oC, you would struggle to get up to 40^oC,’ he says.

‘Now, with different refrigerant gases, heat pumps can give us a system temperature of 55^oC at -5^oC ambient.’

The post Plantroom pioneer: CIBSE Engineer of the Year Phil Draper appeared first on CIBSE Journal.

The rollout of heat pumps powered by low carbon electricity is a central feature of climate change policies in many countries, including the UK, usually with an emphasis on their use in dwellings. Much less attention has been paid to non-domestic buildings, though their aggregate energy consumption for space and water heating is comparable with that in dwellings, and non-domestic heating makes up 30% of all heating systems in the UK.

To encourage the uptake of heat pumps in these buildings, an ongoing UK-led International Energy Agency (IEA) project, Developing the market for retrofitting heat pumps to non-domestic buildings, is looking at providing tools and guidance for building owners and managers of non-domestic buildings. Following a review of literature in the sector, the project felt that there was a particular gap in guidance for building owners, whereas building service engineers are partially catered for by CIBSE AM17: Heat pumps for large non-domestic buildings, one of the few documents on heat pumps in non-domestic buildings.

The project – headed by the Department for Energy Security and Net Zero, alongside organisations in Austria, Canada, Ireland, Italy, and the Netherlands – aims to address the gap in high-level guidance for non-specialists, and collate and share exemplar case studies.

An interactive tool is being developed that will ask users about their existing buildings and systems, and their principal objectives and constraints, before offering them a shortlist of possible system types.

The tool interface will guide users towards the options that appear to be most promising; these can then be evaluated in more detail, using expert advice as necessary. Their shortlist will be linked to generic descriptions of the relevant system types and their principal characteristics, and to two-page summaries of case studies in buildings that resemble their own.

The most suitable choice for a retrofit heat pump system depends on a complicated interplay between: the size, use and complexity of the existing building and its heating system(s); the range of heat pump system options that are possible; and the priorities and concerns of the building owner.

It is likely, especially for smaller organisations, that initial decisions around replacing heating systems will fall to individuals who are not experienced in navigating this maze. At the current low levels of market penetration, they are also unlikely to be familiar with existing heat pump installations. These are the individuals and organisations that this project aims to help.

The decision-support tool will need to map a large number of possible system configurations against the information provided by a tool user. Its basic logic structure – which has been agreed and is now being developed – has three stages that progressively reduce the number of options being considered (see Table 1).

Initially, the tool identifies constraints that limit the range of practicable options; then it focuses on those that are compatible with the existing heat-distribution system; and, finally, it produces the shortlist of options that best match the priorities identified by the tool user.

In most cases, it is expected that the initial two stages will reduce the number of feasible options to a manageable number that can be ranked according to the priorities of the tool user. The third ranking stage requires a set of comparative costs and seasonal efficiencies, such as would be used during design evaluations.

It is expected that tool users will have varied backgrounds, priorities and levels of prior knowledge, reflecting the multiple and sometimes complex procurement procedures that could be used for various levels of retrofit and type of organisation. Guidance will need to be accessible and relevant to, and understandable by, a wide range of ‘decision influencers’.

Exemplar case studies

More than 70 case studies have been identified across the participating countries (including a few in other countries). About 25% are in the UK and are predominantly public sector buildings supported by the Public Sector Decarbonisation Scheme (for which measured performance data is not yet available). In the UK, the projects are predominantly air source heat pumps, often bivalent or high-temperature.

Case studies illustrate the practical application of particular combinations of systems and buildings. With sufficient measured data, they can also provide evidence of performance in use. As the portfolio of case studies grows, the guidance provided by the tool will be compared with systems that were actually selected, which will provide an indication of whether this logic needs modifying.

Preliminary comparative ratings have been carried out on the UK case studies to assess the heat pump types with the lowest capital cost, highest carbon savings and highest carbon savings per £ of capital expenditure (capex). See Figure 1. 

• We are keen to collect information from building owners, facilities managers, system designers and contractors who have already been involved in retrofitting heat pumps in non-domestic buildings, or who are thinking about a retrofit. Contact roger.hitchin@hotmail.com
• The project website is: heatpumpingtechnologies.org/annex60

The post The bigger picture: non-domestic heat pump retrofits appeared first on CIBSE Journal.

Despite this industry-wide push, however – and engineering calculations that indicate usage will be lower – consultants and contractors are hesitant to trust the efficiency of all-electric systems. They are also inexperienced in determining accurately the peak electrical loadings for all-electric buildings.

They do not understand, or are not ready to believe in, the efficiency of these recent technologies. This is partly because they are not willing to trust the calculations made in the design stages and tend to overdesign margins. This is a significant barrier to widespread adoption of all-electric designs – not just in schools, but in all types of buildings.

As the first wave of all-electric schools start to reach completion, it is up to building services engineers to bridge the gap and help educate the industry, so we all have confidence in the calculations. We need to look at how these first all-electric schools perform in operation by regularly measuring and reporting the performance.

This is not something we have historically been good at as an industry, and it requires a step change to get everyone on the same page. Once you start looking at these schools, numbers are clear, and they go a long way to helping understand actual demands and usage. They can then be fed back into calculations in the design stages of future schemes.

Recently, Cundall was part of the project team that completed West Coventry Academy, a 12,000m² secondary school with a sports block and swimming pool. Part of the DfE’s School Rebuilding Programme and Net Zero Carbon in Operation Pathfinder scheme, it was handed over in September 2023, and is all-electric in operation except for a small gas boiler that serves the pool’s water-heating system. The school has air source heat pumps (ASHPs) for heating and kitchen hot water, and direct electric hot water for everything else. It also has LED lighting and controls, and a small photovoltaic (PV) array (100% PV array was not specified in the brief, but there is room to add this in the future).

The building has a well-insulated and airtight façade, featuring Innovare structural insulated panels and high-performance glazing. The design peak heating load is 280kW, just 23W/m². Ventilation is hybrid, incorporating mechanical ventilation units with heat recovery for all occupied spaces for tempered fresh air in winter, and natural cross-ventilation via circulation atria roof turrets for summertime ventilation. The only cooling is to the server room, and some classrooms have exposed ceiling fans to aid thermal comfort.

The school had taken part in the DfE’s ‘pathfinder scheme’ and, in 2021, had employed the then new DfE Output Specifications and technical annexes that had not been put into practice on any scheme previously, and had continued as a test location for these new specifications. When we designed West Coventry Academy, we called on our experience with a previous Priority School Building Programme project, finished in 2018, that we knew had resulted in a maximum in-use electrical demand of just 276kVA (17.2W/m²).

Many did not believe we had achieved such low figures, but we had the electric bills and meter readings to validate this over several years. With this in mind, we designed West Coventry Academy to have a maximum in-use electrical demand of 550kVA (48.2W/m²), and we were confident our design would generate results similar to previously acheived. When the design and build subcontractor took over at RIBA Stage 4, however, they were not so confident in our calculations and an 800kVA supply was installed.

Six months on from West Coventry Academy being handed over, the school has experienced a winter that included a particularly icy -8°C cold snap, on 18 January 2024. The Cundall team visited the site a few weeks later to gather data and discovered that the maximum demand recorded was just 398kVA (33.7W/m²) – lower than even we had predicted for maximum energy demand, and far, far less than the 800kVA supply that had been installed.

This is a clear demonstration of the efficiency of all-electric designs, even in extreme conditions. It also highlights the potential cost implications of overdesigning maximum electrical demand and the associated infrastructure and low-voltage supplies.

It is a habit that we, as an industry, have acquired after years of designing low-efficiency, poorly insulated gas-fired schools. This overdesign not only adds cost, but also carbon – in construction and for the school itself, which, potentially, is left with a lifetime legacy of higher standing charges for a capacity it will not use.

On a lot of new or replacement schools, this can lead to expensive substation upgrades and high-voltage network reinforcement, which, again, may be unnecessary for the school in the long term.

Another reason the industry tends to overdesign schools is that the BSRIA BG9 2011 design guide suggested an electrical services load of 35W.m^-2 for naturally ventilated schools (or 50W.m^-2 for mechanically ventilated ones), and this assumes that heating and DHWS energy is fed by gas or other non-electric sources. The guidelines are based on 12-year-old data from gas-fired heating and hot water, and haven’t been updated to account for all-electric schools. (BG 9 has now been superseded by BG 84/2024 ‘Space and Weight Allowances’ ).

Typically, total connected loads are established based on good design data, and percentage-based diversity factors are then applied to equipment, ASHPs, domestic hot water systems, and other loads. These percentage based diversities are no longer appropriate.

In recent years, we have seen electrical infrastructure designs presented of typically 120W/m² – nearly four times the maximum demand recorded at West Coventry Academy on the coldest day of the winter. Some designs are even higher, and this is clearly based on guesswork, not empirical data or good practice.

We cannot really blame designers for this; the guidelines have not kept up with the current rate of change when it comes to best practice on how we design our schools.

To counteract this problem, Cundall has established a school daily demand profile tool (see graph, left). The peak loads have been taken from actual meter readings of all-electric schools that we have designed. The daily data around these peaks is based on metered annual consumption data, with some adjustments applied depending on school specific facilities for design and technology or computing. BIN weather data is employed to simulate annual profiles based on the available data. When a full set of seasonal meter readings are available they will be used to improve the model.

West Coventry Academy has air source heat pumps for heating and kitchen hot water

The central premise is that the sum of all hourly and daily loads can be used as a check and equated back to an annual load. We must design schools to achieve specific DfE energy use intensity targets, expressed as kW/annum/m², and, clearly, if these are exceeded in this check sum, you have overestimated a particular load.

This data can be extrapolated and used on any other school type to assist with future design estimates, and is a far more accurate way of calculating maximum in-use electrical demand until the guidelines catch up.

My hope is that we can speed up that process and replace the simplistic rules of thumb by feeding the irrefutable data we have collected already into upcoming design specifications.

In the meantime, the key for everyone in the industry, but especially building services engineers, is to keep measuring and reporting regularly on the in-use operational performance of the buildings we design. 

• Peter Hazzard is a partner and schools sector lead at Cundall

The post Essential lessons from electric schools appeared first on CIBSE Journal.

When we say ‘fabric first’ in the context of renewables, however, we are really asking what can be done to the building envelope to reduce heat loss. A reduction in heat loss means that a lower kilowatt (kW) capacity of heating plant is required, meaning lower capital and installation costs. It also means heat pumps can run more efficiently (see panel, ‘Why heat pumps suit fabric first’).

However, if heat losses are high because the fabric first approach cannot be taken, heat pumps will struggle to compete with the boilers they are replacing in terms of running costs. (Improving the fabric efficiency may not be possible if costs are prohibitively high or buildings cannot be altered for conservation reasons.)

So, what can be done if a building owner wants to decarbonise their heat and the existing building thermal envelope cannot be improved? One option, which is nearly always fast, affordable and efficient, is to design a hybrid system combining boilers and heat pumps – but this won’t do if the client brief is for full electrification of heat.

Many argue that high-temperature air source heat pumps (HT ASHPs) have been developed to solve this problem. However, the solution is not as simple as it is often made out to be. For anyone considering this route, it is essential to investigate the building and system to ensure an appropriate design and specification. 

This article considers possible solutions for high-temperature heat pump retrofits and looks at the key areas to investigate before undertaking such a project.

Switching boilers for heat pumps 

Discussions of high-temperature heat pumps allude to bringing the operation range into the familiar 82/71°C or, potentially, 80/60°C range. This, however, can be slightly optimistic, as an 80°C flow temperature for even the most modern of R290 (propane) ASHPs is at the very top end of the performance envelope. 

BS EN 14825:2022, which recommends conditions for testing heat pumps, states that a high-temperature heat pump must deliver 65°C at -7°C/-8°C (dry-bulb/wet-bulb) ambient conditions, with medium and low classifications required to deliver 52°C and 35°C respectively at the same ambient conditions. Even when HT ASHPs are able to deliver 80°C, this falls slightly short of the 82°C flow required by 82/71°C circuits. Added to which, most heat pumps prefer to operate in the 5-10K ΔT range, making a straight swap on 80/60°C circuits not impossible, but challenging. From my experience, in 82/71°C circuits the boiler(s) will nearly always be set to ~85°C to mitigate hydronic inefficiencies, the most common of these being temperature dilution.

Pragmatically, the challenges involved in the detailed design of swapping out boilers for heat pumps are not to be trivialised. Before embarking on a project of this sort, we strongly recommend that a significant amount of investigative engineering is undertaken. Try to ascertain (but not be limited to) the following:

• What were the original design temperature and loads?
• Are there hydronic inefficiencies – such as exposed, poorly insulated pipework or temperature dilution – that can be addressed?
• Has the building been extended/reduced/zoned or had alternative heating systems installed in localised areas
• Can the true building load requirements in summer, winter and transient months be measured or calculated with a degree of accuracy?
• Are any bounding spatial constraints yielding enough to allow for new plant to be installed?
• Does budget allow for 100% of the required heating power to be via ASHPs?
• Are electrical capacities sufficient?
• Are there factors to offset the potential higher running costs, such as PV? 

Design information for dated buildings is often limited to a hand-drawn schematic on the plantroom wall. To add to the confusion, many will have seen a dated building run, at some point, on one boiler out of three during winter, with no complaints. 

Improving our understanding of the building profile can be done through installing items such as ultrasonic heat meters, undertaking a full heat-loss calculation (if budget and time allow) and using known data, such as gas-meter readings. Extrapolation of live data or interpolation of fragmented historic data help piece together the jigsaw, for a greater insight into the true thermal profile.

The goal here is to understand what might be changeable, what can’t change, and the risks. For example:

• Flow temperatures may be reduced by fixing hydronic inefficiencies. 
• Bracketing of the heating system may reduce the requirement to run all circuits at 80°C or 82°C all year, improving running costs (see below, ‘Bracketing’).
• Spatial challenges can be solved by sizing real requirements through measuring and calculation.

This may take months to complete, and can be further complicated by seasonal conditions. Ideally, this would involve at least a year’s worth of data, with any subsequent installation planned for warmer months. 

Bracketing 

Bracketing involves consolidating the heating system into frames of known and weighted data. For example, if the survey data shows a sizable constant temperature (CT) circuit serving an air handling plant exclusively, the decision may be taken to ‘bracket’ this out of the overall heating system.

By bracketing this circuit and serving it directly from its own heat pump plant, we are now able to change the tempering or reheat coils to suit a 55°C flow temperature (or lower). This decision alone could increase the heat pump efficiency by up to 150% from a design temperature of around 80°C.

The same principle can be applied to variable temperature (VT) circuits when the CT circuit is unable to deviate from the current design flow temperature. 

VT circuit bracketing can yield massive efficiency rewards, as the weather compensation can be undertaken at the plant without the use of mixing valves.

With direct weather compensation on HT ASHPs, the flow temperature could range from 35°C-80°C. If heat losses mitigations have been carried out then, potentially, emitters may be changed when and if possible, to allow a more aggressive reduction in flow temperature. 

The proportion of the year when the HT ASHPs must remain at 80°C flow may be offset, in terms of net efficiency, by the period of time that flow temperatures are not required at 80°C via direct weather compensation. 

The weighted aspect of bracketing involves understanding the split in capacity required for each circuit. If VT equates to 80% of the overall load requirement, then addressing that in isolation, with CT remaining on 80°C flow, may impact the overall efficiency of the building sufficiently, without the need to replace air handling unit (AHU) coils. 

Figure 1 shows a two-boiler reverse return header setup, with CT and VT circuits, that is typical of many 82/71°C legacy designs. Using data from the current VT setup (if available), the VT minimum temperature can be reduced below current settings to assess whether the target space temperatures may still be maintained. Even a modest reduction in flow temperature will ensure higher efficiencies.   

Most HT ASHPs would deliver a coefficient of performance (COP) of approximately 2.2 at 65°C flow and -2°C ambient conditions. 

If we were able to drop the weather compensation to below 60°C, output from medium-temperature (MT) and HT ASHPs may be blended, potentially reducing any siting or budget complexities of a full HT. 

In the blended MT/HT example solution shown in Figure 2, the heat pumps are cascaded, with a three-port diverting valve being used to deliver heat to the calorifier. Typically, the MT ASHP(s) would act as lead for the directly weather-compensated circuit, supported by the HT ASHP(s) during peak demands. When higher temperatures are required for more challenging design conditions, the HT ASHP can increase the thermal store temperature up to 80°C.

If Figure 1 (the reverse return arrangement) had been designed on a ΔT of 20K, one solution is the alternate cascading method shown in Figure 3. This uses the thermal store lower and upper stratified sections to provide a cascaded temperature rather than the load. This is an identical philosophy to that used with most hybrid solutions. Temperatures are still key, and with good weather compensation a blend of MT and HT ASHPs can still work. However, this solution is more suited to HT ASHPs as, at a higher design temperature of 80/60°C, MT ASHPs are unable to delivery any useful heat.  

Managing expectations

As clients start to review boiler-replacement projects and the achievable options to decarbonise asset heat, we must still ensure fabric options are considered first. 

Emitter replacement to suit low-temperature heating will tend to yield a higher efficiency overall than a high-temperature heat pump system. Heat pumps should not be over-specified in terms of capacity, for economic and spatial reasons. 

Ultimately, perfect is the enemy of the good when it comes to decarbonising buildings unable to offer a significant improvement from fabric upgrades. 

However, a well-considered assessment of the building thermal profile delivers essential intelligence for a clearer understanding of the impact of the potential system solutions, to ensure true life-cycle benefit.  

About the author
Ryan Kirkwood is engineering solutions manager at Baxi

The post High hopes: overcoming challenges with high-temperature heat pump integration appeared first on CIBSE Journal.

Why is TM51 Ground source heat pumps due an update now?

Ground and water source heat pumps are projected to become the dominant technology for heating buildings in the UK. With their immense potential for reducing energy consumption and carbon emissions, there’s a necessity for an authoritative guide on best practice, especially as their applications can range from single domestic properties to large district heating or cooling systems. 

Ten years ago, when the first edition of TM51 was published, heat pumps were almost unknown as a means for heating buildings. The new, completely rewritten edition aims to lay out how ground source heat pump (GSHP) systems should be designed to achieve maximum efficiency, lowest carbon emissions, and the optimum occupant comfort.

How would you summarise it?

TM51 Ground source heat pumps is a comprehensive Technical Memorandum aimed at promoting best engineering practices for the design, installation and maintenance of ground and water source heat pump systems. 

It caters for a wide audience, including system designers, building services engineers, and building owners and occupiers. The guide also examines the specifics of GSHPs and why these systems are well adapted to the unique challenges of inner-city environments.

What are the three most important things you would like to put across?

• Understanding of heat pumps: the guide addresses the lack of understanding surrounding heat pumps, looking at misconceptions and initial cost concerns, and making them more accessible and accepted by a broader audience.
• Heat networks: it offers insights into two primary heat network configurations. It also discusses the benefits and challenges of each system, ensuring effective energy distribution and efficiency.
• Inner-city challenges: the publication recognises the challenges of space constraints, and introduces innovative solutions, including directional drilling techniques using technology developed by the oil and gas sector.

Does it cover heat networks and single-building schemes?

Yes, the publication goes into detail on heat networks using a large central heat pump and those using multiple smaller heat pumps on a shared ground loop. The guide also acknowledges the challenges and solutions for implementing GSHPs in apartment buildings, especially in constrained inner-city areas.

How does it work in conjunction with the heat networks technical assurance scheme (HNTAS)?

TM 51 Ground Source Heat Pumps aligns closely with the objectives and core principles set out by the HNTAS. The HNTAS aims to standardise quality assurance processes for heat networks, leading to cost-effective, reliable, and environmentally-friendly heating solutions. 

TM51 provides the practical knowledge, guidelines, and best practices to achieve these objectives. 

It acts as a tool to ensure that the outcomes focused, preventative, proportionate, deliverable, adaptable, and enforceable principles of HNTAS are effectively implemented and adhered to. 

The post Heat pump design from the ground up: upcoming TM51 update appeared first on CIBSE Journal.

When considering an existing gas-fired heating system that is operating with relatively high water flow temperatures of
70-80^oC –compared with today’s typical designs of ≤55^oC – application of an electrically driven alternative to match those flow temperatures is fairly straightforward. 

Managing the impact on operational costs and capital expenditure (capex) is much more complex, however, especially given the disproportionate cost per kWh of gas vs electricity currently, and the relatively high capex cost of technologies, such as heat pumps, compared with fossil-fuel alternatives. 

This is where a bivalent approach can become attractive and possibly help bridge some of these gaps. Focusing on using heat pumps as part of this bivalent solution, we can consider two broad types of configuration: bivalent in parallel and bivalent changeover (see Figure 1). 

It is typical in the UK for peak space heating capacity (100% load) to only be required for a small number of hours in the year and, therefore, this makes up a relatively small amount of the total kWh of heat energy delivered. This opens up the possibility of deliberately undersizing your heat pump, in comparison with peak load, and only operating it for certain parts of the year, allowing the gas boiler to provide the extra peak capacity or peak flow temperatures when needed. This approach can help reduce upfront costs and plant space requirements. 

We know that operating a heat pump at the lowest possible flow temperature and the warmest source temperature will usually deliver the highest efficiency and lowest operating cost. But we must also consider how any heat generated is emitted into the building – this is where the infrastructure of the existing system begins to influence the design approach.

The existing heat emitters (fan coils, air handling unit coils, radiators, and so on) must be assessed to understand their deliverable output capacity at different mean temperatures. This will demonstrate what mean temperature is needed at certain ambient conditions to deliver the required capacity. This is a key piece of information needed to model bivalent parallel and bivalent changeover configurations.

Bivalent changeover configuration:

In a bivalent changeover arrangement, the heat pump is deliberately designed not to deliver the peak flow temperature or capacity of the heating system. It will only operate up to a temperature and capacity chosen to match the heat-emitter capabilities and building load at that changeover point.As a result, the heat pump will operate in isolation from the boiler, providing heat to the existing heat emitters until its maximum flow temperature and capacity are reached. At this point, it will turn off and the boiler will take over, delivering the higher-temperature water and increased capacity required to meet the increasing building load. 

This arrangement will deliver a lower proportion of annual space heating load from the heat pump compared with bivalent parallel. However, as the heat pump will not operate at peak design conditions, or be asked to deliver high flow temperatures, it will benefit from increased efficiency, resulting in a lower operating costs.

To maximise the ratio of kWh contribution from the capacity of heat pump provided, our research shows the optimum will be approximately 50-75% of the building peak load, with the maximum flow temperature being approximately 55^oC. Depending on overall system design and existing heat-emitter capabilities, other combinations can also deliver good results. See Table 1 for an example of a bivalent changeover arrangement. Examples are modelled on the Mitsubishi CAHV-R450 YA-HPB.

Bivalent parallel configuration:

This requires the heat pump to be capable of delivering the peak flow temperature of the system, allowing it to work side by side with the boiler at any time of the year. This means the heat pump can be sized to any capacity and, as Figure 4 shows, deliver heat energy on its own when it has the capacity, or in conjunction with the boiler when the load is greater than the heat pump capacity (the example shows a heat pump sized at 50% of peak load). Flow temperature can be fixed or weather-compensated, but the key design principle is that the heat pump is able to deliver the required flow temperature to meet peak heating demands via the existing heat emitters.

This arrangement will deliver a large proportion of annual space heating load from the heat pump, and probably result in the lowest overall carbon emissions. However, operating the heat pump at potentially high flow temperatures and low ambient conditions will reduce its efficiency, so this configuration will probably result in an increased operational cost compared with the gas boiler-only system. 

Special consideration must also be given to the choice of heat pump, to ensure it delivers the necessary flow temperature and capacity in all operational conditions. A cascade arrangement or high-temperature natural refrigerant product may be needed to achieve the required flow temperature. The capacity of the heat pump can be freely selected to meet any site constraints of power supply or plant space, and consideration can be given to capital costs to achieve the optimum balance. 

To maximise the ratio of kWh contribution from the capacity of heat pump provided, our research shows the optimum capacity in relation to the building peak load is likely to be approximately 25-50%. See Table 2 for an example of a bivalent parallel arrangement. Calculations shown are for comparison purposes only

Conclusion

As the two examples show, introducing even a relatively small heat pump into an existing heating system will lead to carbon reductions, but applying that same heat pump capacity in different ways can achieve different outcomes.

Choosing which configuration and capacity of bivalent system is best suited for a specific project depends on budget, existing infrastructure, desired outcome and, most importantly, how it is controlled.

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Unlike our vision, which operates in a limited range, our hearing covers a broader spectrum of 10-octave bands, making us more vulnerable to unwanted noise. 

With our brain’s auditory responses effectively never switching off, it can become almost impossible for us to adapt to the hum of building services equipment, a noisy workplace, or the rumble of a passing freight train, for example.

Isolators reduce noise and vibration if correctly selected

Despite the glaring impacts of neglecting acoustic considerations in building design, noise and vibration control within the built environment are still all-too-commonly an afterthought. One example is the installation of large heat pumps for heat networks or individual buildings, often replacing existing gas-fired boilers or CHPs (see panel, on page 48). If noise and vibration is not controlled in these installations, there is a danger that areas close to the plantroom could become unusable because of the disturbance to occupants.

CIBSE’s Guide B4, published in 2016, provides an in-depth guide to noise and vibration control for building services systems. It includes information and best practice solutions for noise and vibration control (bit.ly/CJB42016), and complements other guides in the series (B0 to B3) that cover heating, ventilation and ductwork, air conditioning, and refrigeration. The B4 Guide also aims to counter external sources of noise. 

Consequences of excess noise and vibration

A lack of sufficient noise control of building services equipment can lead to disturbance to building occupants and neighbouring properties, and a lack of compliance with planning requirements – leading to health issues, work disturbance, complaints and, ultimately, enforcement actions against the project.

Expansion joints depicted above allow movement and reduce risk of pipes resonating, leading to noise and future failure

Limited vibration control can result in excessive levels of vibration being transferred into a building structure, which is a major issue for sensitive manufacturing and scientific facilities. In extreme cases, this could be felt as tactile vibration, but, more commonly, the issue materialises as regenerated noise. Introducing noise and vibration control retrospectively is more difficult and expensive than incorporating it in the initial design.

To ensure that system designs are not blighted by noise or vibration, early engagement with acoustic consultancy following Guide B4’s robust guidelines is recommended. It will help designers reduce costs by avoiding common pitfalls and mistakes that may result in expensive rectifications, and reduce future upgrades or repairs necessary to combat noise and vibration problems for the end user.

The emergence of multifunctional spaces and the need to decarbonise are creating more complexity in buildings, making an integrated approach to noise and vibration increasingly important. 

There is a growing trend for structures to become more lightweight to reduce carbon and limit the cost of materials. The downside is that lightweight structures carry noise and vibration more effectively, increasing the need for considered acoustics, noise and vibration control. 

From the incorporation of office spaces and gym facilities to cinemas and restaurants, multifunctional spaces in residential and commercial developments are becoming ever more complex. Catering to the various needs of the end user requires careful acoustic planning in the early stages, to ensure optimal sound quality and minimal disturbances between distinct functions and building services.

The increased focus on health and wellbeing in buildings is another reason noise and vibration should be considered at an early stage, alongside other environmental factors such as indoor air quality and temperature control. A good acoustic strategy will contribute to a better quality of life for the end users.

Acoustic consultancy is a unique, yet vital, part of the design process. Understanding how building materials and services equipment interact with each other and the surrounding environment is vital to the successful and sustainable functioning of the building. Early engagement with noise and vibration strategies using CIBSE’s B4 Guide will create better holistic building designs. 

Kyriakos Papanagiotou is founder and director of KP Acoustics Group, and Adam Fox is director at Mason UK

CIBSE Guide B4 is available on the Knowledge Portal www.cibse.org/knowledge

References:

1 Noise complaint research, Churchill Insurance, 2022 bit.ly/3Qoh1Em

The post Sound advice appeared first on CIBSE Journal.

The Amicus Altus is available in three possible configurations: Two-pipe heating only, two-pipe heating or cooling, and four-pipe simultaneous cooling with heating and heat recovery, making it suitable for most types of commercial project.

The high temperatures achieved makes the Amicus Altus especially useful as a direct low carbon replacement for gas boilers in buildings with high hot water demands without requiring a substantial remodelling of the heating and/or hot water systems.

This makes the new range a valuable addition for specifiers looking for solutions that support net zero carbon strategies and help to reduce energy bills without major upfront capital costs.

The new range also operates with the very low global warming potential (GWP) refrigerant R290 (propane), which is one of the most climate-friendly refrigerants on the market. It has a GWP of just three compared to the popular traditional alternative R410A which is typically used in this type of application and has a GWP of 2,088.

R290 also has an ozone depletion factor (ODP) of zero and, according to the Intergovernmental Panel on Climate Change (IPCC), its GWP over a 20-year period remains below one – making it more environmentally friendly as a refrigerant than carbon dioxide (CO₂). Another benefit is that it does not contain any poly-fluorinated chemicals (PFAS) which are now subject to stricter restrictions in the UK and Europe.

Future proof
By going with this non-HFC ‘alternative’ refrigerant, Lochinvar has produced a future-proof solution that is in step with the latest UK regulations which require the industry to move away from higher GWP substances.

Under the current phase down timetable, the UK is looking to eliminate fluorinated gases (f-gases) from most heat pump applications by the end of the decade. This is in line with the European F-Gas Regulation that the UK continues to mirror despite its departure from the European Union.

The Altus units are also fully cascadable with outputs from 88 to 880kW and deliver an impressive Coefficient of Performance (CoP) of up to 5.5 – seasonal COP is around 3.95. They can also operate in heating mode down to external air temperatures as low as -20°C.

With built in controls and a BMS fault and remote on/off signal that prioritises hot water production this small footprint unit is easy to install and commission – and is supported by Lochinvar’s offer of free site visits for every installation.

“We are delighted to be bringing such an impressive step forward for heat pump technology to the market,” said Lochinvar’s product engineer Steven Hunt.  “Air-to-water heat pumps are generally highly energy efficient, but the Altus also delivers hot water temperatures comparable to those end users are used to with conventional gas boilers.

“This, allied to the low GWP and zero ODP factors, make them an attractive choice for anyone specifying a retrofit project with high performance and low environmental impact in mind.”

Air-to-water heat pumps can be integrated into a variety of heating systems, which makes them a flexible option for different types of buildings and installations – and although the initial installation cost will be higher than for a gas boiler, the long-term savings are potentially far greater and the building’s carbon footprint substantially reduced.

This new product follows last year’s launch by Lochinvar of the UK’s most powerful heat pump water heater the Amicus Aquastore.

It has an output of 8kW and 455 litres of hot water storage capacity in a compact monobloc package combining heat pump and storage vessel. It can deliver up to 65degC hot water in both efficiency and hybrid modes and up to 490 litres in a peak hour with a 50degC temperature rise.

Popular
The Aquastore and now the Altus are the latest additions to the extensive and popular Amicus range of air source heat pumps (ASHPs) which includes models delivering domestic hot water capacities from 7.7kW up to 210kW for a wide range of projects including large residential; medium and large commercial; and industrial applications.

“Heat pumps are playing an increasingly important role in helping the UK transition to low carbon heating and the Amicus Altus is just the latest in a line of innovations designed to make the technology available to the widest possible range of users with minimal disruption to the existing building services,” said Hunt.

“As well as our on-site support and technical back-up, another benefit to our customers is that Lochinvar can provide all the components needed to provide a complete low carbon system with heat pump technology at its heart. This considerably simplifies the specification, design, and installation process,” he added.

www.lochinvar.ltd.uk

The post Lochinvar launches high temperature low GWP heat pump appeared first on CIBSE Journal.

However, there can be a significant increase in spatial requirements and capital expenditure when using heat pumps as the lead heat-generation source for heat networks, compared with gas CHP and gas boiler solutions.

To tackle this issue, I propose a hybrid approach that combines heat pump and thermal storage with electric boilers. Thermal storage increases operational flexibility of heat pumps and maximises the annual target heat fraction that can be provided by the heat pumps.

My research, How hourly load modelling is revolutionising heat pump and thermal store sizing in hybrid energy centres, was presented at the CIBSE ASHRAE Technical Symposium 2023, at the University of Strathclyde, Glasgow, in April (www.cibse.org/symposium).

It provides a ‘rule of thumb’ for hybrid energy centres to support designers and developers early in the design stages, ensuring that heat pump size and thermal storage capacity are optimised to achieve the required target heat fraction contribution, which is the proportion of the total annual network consumption that is provided by the heat pumps.

The heat pumps are sized to deliver the majority of the site-wide annual heat demand, with large thermal storage used to reduce the required heat pump size by storing heat during times of lower demand and using it during periods of higher demand. Electric boilers are sized to act as ‘top up’ during periods of peak load demand.

It is important to consider equipment sizing early on in the design stages, as such decisions could be constrained later by architectural layouts, floor plans and building elevations. This is where my research comes in.

Modelling heating and hot water use

In my research, an hourly load model was built, which aims to model the domestic hot water (DHW) and space heating usage that can be assumed for each hour across an entire year for any given development.

The model takes into account several inputs to investigate the impact of equipment sizing on the heat pump’s annual heat fraction contribution. These include: heat network heat losses; heat interface unit heat losses; DHW hourly profile; space heating hourly profile; and annual DHW and space heating loads.

To be as flexible as possible, the model allows for easy variation of building size, DHW, space heating loads, expected heat losses, and geographical location. By doing this, the impacts of these factors on heat pump and thermal store sizing can be easily understood and assessed. The final model was then validated against load profiles taken from operational heat networks to provide confidence in the findings of the research.

While there are many benefits to oversizing thermal storage, a key constraint will be the spatial requirement within the energy centre. This is especially key when comparing this with traditional CHP thermal storage, which operates at higher temperatures and, therefore, requires a smaller volume.

The hourly load model allowed the thermal storage size to be modelled against the heat pump to determine the point at which any increase to thermal storage will have minimal impact on reducing the heat pump size. The study found that, as a rule of thumb, thermal storage should be sized at 50-75L·kW^-1, as shown in Figure 1. The percentages under the graph represent the annual target heat fraction contributions (for the heat pumps).

Because of the impact of the higher electricity tariffs compared with gas, it is critical that heat pump sizing is considered carefully. If the heat pump is undersized and unable to meet the required target heat fraction, end users will see a significant increase in their cost of heat because of the reliance on electric boiler top-up.

Equally, oversizing a heat pump presents a number of challenges, particularly when considering the spatial requirements against a gas CHP or gas boiler solution.

As such, the hourly load model was used to provide a rule of thumb for a given target heat fraction contribution as a percentage of the site-wide peak load. The findings demonstrate that a target heat fraction that is as high as 99% of the site-wide annual demand can be achieved by installing heat pump capacity of less than 50% of the peak load (see Figure 2).

A summary of the ‘rule of thumb’ findings are presented in Table 1. These findings provide a benchmark to support developers and designers early on in the design stages, to ensure energy centre sizing is fully considered until more detailed design calculations can be carried out at a later stage.

In conclusion, the research demonstrates that sizing a hybrid system for a heat network requires careful consideration of various factors, including the capacity of the heat pump and thermal store. Designers must take spatial limitations into account when estimating the required heat pump and thermal store size, to ensure these will not be constrained later in the design development, when the risk of undersizing will be critical.

The research provides targeted guidance for sizing heat pumps and thermal storage at concept design, in advance of detailed design, helping to pave the way towards more efficient and sustainable heat networks in the UK. To read the research paper, visit the ‘Research & writing’ page on FairHeat’s website: fairheat.com/research-writing

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The current reality is that a paltry 60,000 were installed in the UK last year – which, at two heat pumps per household, put the country at the bottom of the European heat pump league.

To increase the number of installations in new homes, the government is taking a ‘big stick’ approach and proposing to ban gas and oil boilers in new homes from 2026.

It’s a huge challenge, especially for small to medium-sized housebuilders that are familiar with gas boilers, and may not have the resources to design and develop homes based on alternative heating systems.

Building merchant Travis Perkins has recognised this predicament and launched a digital platform called WholeHouse, aimed at streamlining the design and delivery of low carbon homes.

Lee Jackson, WholeHouse director at Travis Perkins, says the industry lacks the skilled workers required to meet government heat pump targets, and a new digital approach is required that simplifies design and installation, and encourages the prefabrication of building systems.

‘I’ve opened too many airing cupboards where I’ve been met by a wall of pipework that’s 15 layers deep,’ says Jackson. ‘The average plumber has spent years installing combi boilers, and now they are expected to put back in a cylinder and install an air source heat pump [ASHP].’

Without help, Jackson believes plumbers will have to learn from job to job, and will deliver inefficient heat pump systems until they have gained experience.

Baxi’s is the only appropriate heating system featured in the software at the moment

WholeHouse is a 3D online design tool that allows the housebuilder to design any size home using a variety of materials and systems, including heat pumps. The software has strict parameters to ensure whatever is selected leads to the most energy efficient and cost-effective design possible. Once a design is settled on by the user, the program produces a set of drawings and the bill of materials in just 45 minutes.

In developing the software, Travis Perkins assembled a team of 20 suppliers and consultants to come up with design parameters that guarantee the software’s outputs are optimised for cost and energy efficiency.

‘Upfront design is undervalued in housebuilding,’ says Jackson, who is a trained architect. ‘It’s critical, with new technologies, to make sure the design is correct – then we have a fighting chance of delivering what we intend to.’

Some designs, such as the heating system, can be prefabricated off site, which cuts down on waste and reduces the need for people on site. Jackson calls this process ‘the industrialisation of design’.

The designs are incorporated in the software, alongside the latest housing standards and calculation methods, including SAP 10 and the CIBSE TM59 Overheating risk calculation, which is included in the latest Part L of the Building Regulations. This means that if users change window sizes, for instance, the software will automatically adjust other elements – such as insulation – to ensure compliance with Building Regulations.

Radiator sizes will be adjusted according to whether a boiler or heat pump is used as the heat source, and the system automatically inserts the most efficient pipework runs for plumbing, and ductwork for ventilation, positioning the necessary voids and holes in the floors and joists. It can include photovoltaics and decentralised mechanical extract fans, while more sophisticated mechanical ventilation with heat recovery units are also included.

One of the design partners is Baxi Heating, which supplied details of 160 understairs configurations featuring its range of ASHPs, water cylinders and pumps. (Gas boilers are also included.)

Andrew Miele, senior application engineer, offsite, at Baxi, was responsible for ensuring the design outputs did not feature a tangle of pipes in the understairs cupboard. By working with other partners on the design, he was able to ensure the plantroom was as streamlined as possible and could be prefabricated in the Baxi factory.

A prototype helped Baxi position its heating system under the staircase

It was decided by WholeHouse team to locate the cylinder under the stairs with the rest of the heating system, because it only took up 0.9m² of floor space compared with 1.5m² of floor space if it was in an upstairs utility cupboard.

Baxi worked closely with staircase manufacturer Staircraft to devise an efficient heating design that worked in the spaces created by the risers and treads. Staircraft provided Baxi with a staircase to create a prototype that validated software designs and calculations. The mock-up will soon be installed at a Baxi training facility.

To improve the efficiency of the design, Baxi also requested that a wall be moved 100mm, something that would have been impossible in a regular build, where Baxi would have come onto the project at a much later design stage.

Miele says he was given much more time to optimise the design: ‘In other projects, I will try to feed in design suggestions, but you can only make limited changes. Whereas here, everything’s up for discussion.

‘Going into this amount of design detail was of great benefit to us, because we can then repeat the design in the factory.’

Baxi used its experience with prefabricated utility cupboards and commercial heating and cooling systems to feed into the design discussions.

With more standardisation of design and repetition, offsite manufacturers will be able to achieve better economies of scale, says Jackson. They will also be able to plan for production because WholeHouse knows when working designs have been downloaded and when materials and systems need to be manufactured. ‘The visibility means that Baxi can make sure its supply chain is always sized to suit the demand coming through,’ says Jackson.

Any manufacturer can potentially have its products featured in WholeHouse – there are a number of suppliers’ door kits featured, for instance – but Jackson says Baxi’s is the only appropriate heating system featured at the moment.

A digital twin of the house is created, which can be used in the future if, for example, the occupier wants to add an extension (the project teams purposely created designs that could be extended in the most efficient and economical way possible).

It has not yet been decided who takes ownership of the digital twin  – it could be WholeHouse or it could be the regional housebuilder. ‘It will be whoever adds the most value,’ says Jackson.

The first two houses designed using the system are nearing completion and Jackson has ambitious plans for the system. As well as targeting the SME housebuilder market of up to 2,000 companies, he thinks it could also be used by selfbuilders and major housebuilders, with whom he is already in discussion about using elements of WholeHouse.

Jackson has also had talks with the Health and Safety Executive about incorporating manuals into the software and highlighting known safety issues. ‘We can bring more people to WholeHouse to refine the software further and iron out other issues,’ he says.

While Travis Perkins is advocating a standardised approach, it doesn’t mean that homes will look the same everywhere. This is part of the appeal to regional housebuilders, as they can reference the local vernacular with their choice of materials, says Jackson.

There is ‘beauty in standardisation’, he adds, with some of Britain’s best, most historical housing being based on only two or three house types, such as the Royal Crescent in Bath and Islington’s Georgian townhouses.

‘Pattern books are a fundamental part of our history of architecture and the landscape of towns and villages,’ says Jackson, who is talking to The Prince’s Foundation about using WholeHouse in heritage developments.

‘We tend to associate the term “house types” with some of the homes that major housebuilders churn out, but we shouldn’t think of standardisation in that way,’
says Jackson.

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