Regulations will require minimum technical standards, under a Heat Network Technical Assurance Scheme (HNTAS), for all new-build heat networks from 2025, including the 50,000 residential connections already happening each year. This could rise to 100,000 heat interface units being installed annually in the foreseeable future, partially driven by the regulations themselves.

All 14,000 existing (legacy) heat networks will also be covered, including the 500,000 residential customers currently supplied by heat networks. However, the number of networks is probably a significant underestimate, and improved data could easily indicate there are more like 18,000 legacy networks.

Both communal and district heat networks will be included in the regulations, with the majority of legacy networks being relatively small, communal (single block) networks. The regulations will recognise that many of these communal systems are old and not in the best state of repair, often resulting in poor performance and customer outcomes.

HNTAS is addressing how we can bring these up to a reasonable performance standard over a reasonable period of time. The technical standards will be outcomes-based, so networks will need to meet key performance indicators (KPIs) to gain Heat Network Certification.

For the past 18 months, the Department for Energy Security and Net Zero (DESNZ) has been developing HNTAS, building on CP1 (2020). The work has been led by technical author FairHeat, in partnership with Gemserv, which is focusing on procedural aspects of the assurance scheme.

HNTAS is proposing that a single ‘responsible person’ be accountable for each heat network

Normative documents have now been developed, setting out the necessary governance, structures, procedures and technical standards required to ensure a minimum level of performance and reliability for heat networks.

HNTAS core principles are that the scheme will be outcomes-orientated, preventative, proportionate, deliverable, adaptable, and enforceable. See ‘Assuring quality of heat networks’, CIBSE Journal, May 2023.

The technical normative documents set out clear and measurable KPIs (technical minimum requirements) to be met for each element of a network, plus the evidence required and depth of assessment, along with ‘key failures’ that need to be avoided.

Draft normative documents have been developed in collaboration with sector stakeholders through an extensive series of technical sub-working groups. This involved 25 technical sub-workshops, bringing together 69 stakeholders from 44 diverse organisations, including manufacturers, housing associations, local authorities, consultancies, developers, contractors, energy service companies, trade associations, and professional bodies. This industry engagement will continue with a HNTAS consultation in the summer.

HNTAS’s proposed approach is to certify individual heat networks. Our work-in-progress model is shown in Figure 1. It combines a series of assessment gateways (orange) that, ultimately, lead to certification (blue). Most of the detailed technical assessment work, carried out by registered and trained assessors, will take place across the orange stages, with the clipboards showing assessment points, and the dotted lines as gateways to proceed to the next stage.

The normative documents set out the detailed minimum requirements at each assessment through design, construction and commissioning. These design/construct/commissioning gateways aim to ensure the network is likely to meet future operational performance targets and gain full certification. There is a clear requirement to have binary yes/no decisions, with certification (authorisation to supply heat to customers) awarded to networks that meet minimum technical requirements. By requiring responsible persons to demonstrate that their heat network performance meets KPI thresholds, before allowing a network to pass through each assessment gateway, the scheme is ‘preventative’ and ‘outcomes-based’ (two of the core principles of HNTAS).

This approach aims to ensure that the great majority of heat networks pass at the point of certification, and that key failures in the market are avoided. There are 28 KPIs, categorised into six categories, that set a framework for measuring and monitoring heat network performance. The six categories are: energy centre; district distribution network; thermal substation; communal distribution network; consumer connection; and consumer heat system.

Existing legacy networks will, inevitably, find it harder to meet the HNTAS minimum standards than new networks. So, HNTAS is taking a pragmatic transitionary approach to bring legacy networks as close to full standard as possible, as soon as possible. HNTAS will set out a transition period, during which improvement plans will need to be submitted and minimum levels of metering will need to be installed. Once metering is in place, networks will be in a position to evidence-measure performance accurately and move to full certification.

Fixing legacy networks

For legacy networks, HNTAS aims to ensure the market is able to comply and that the very worst-performing networks are addressed early. To achieve a steady improvement in performance over time, the goal is for every network to be fully certified to a minimum level of performance by a set future date. The proposal for legacy networks is a two-stage transitional approach, which will require minimum levels of metering and monitoring to be installed, followed by the need to report performance, with a minimum threshold that all heat networks must meet within a set period.

Operators will be required to submit a Heat Network Improvement Plan, setting out how they will achieve certification within a set period following the installation of metering, and will need to prove in-use performance after two years of operation, based on real data. It is proposed that networks installed before 2015 will be allowed more relaxed targets than those installed post-2015, when the Heat Networks (Metering and Billing) Regulations came into force.

HNTAS is proposing that a single ‘responsible person’ – such as the owner or developer – be accountable for each heat network. Duty holders of the designated designer, contractor and heat network operator are accountable to the overall responsible person for the day-to-day running of each project stage. This designation of duty-holder responsibilities is similar to the requirements in the Building Safety Act.

The project team is keen to ensure that this is a deliverable scheme, which is proportionate and does not place too much burden or cost on heat network operators or consumers.

During the operational stage, if the network achieves HNTAS minimum performance standards it moves into a stage where the heat network operator regularly submits data to the HNTAS portal (currently being developed), to show that it is still meeting the HNTAS KPIs.

More detailed assessments are only triggered where it falls outside the KPIs. Essentially, this allows a level of ongoing self-assessment for networks that meet minimum performance levels.

Evidence and data requirements will form a ‘golden thread’ throughout all stages of a network’s life, requiring submission of data into the HNTAS and Ofgem digital platforms. It is hoped much of this data submission will be automated, to minimise time and cost.

It is clear that significant change is coming in 2025 as the sector transitions to a regulated heat network market, and setting minimum technical standards is a key part of this. Assessing and certifying heat networks that meet the minimum standards will raise sector performance.

HNTAS is moving into a pilot phase across 2024, to test that it works in practice on real networks, before final implementation in 2025. Engagement with stakeholders throughout this process will continue, as this is key to achieving sector buy-in for the assurance scheme.

There are significant benefits and opportunities that will come from HNTAS: a commercial market for trained and registered assessor services; a general improvement in heat network performance, with consumers seeing improved reliability and service levels; social landlords and local authorities being able to provide more affordable heat; and investors viewing networks as more investable.

There is still a great deal to do to develop heat network regulations, through consultations and secondary legislation. DESNZ aims to publish the HNTAS normative documents in some form this year. HNTAS piloting will take place throughout the year, and DESNZ is seeking heat network operators and assessors that would like to take part. Plans to update CIBSE CP1 are also being put in place, to ensure alignment before regulations are implemented in 2025. A methodology to calculate the carbon content of heat should also be in place by that date.

Heat networks are complex and introducing regulation is not straightforward, so it is important to give this sector early sight of direction of travel. As such, this is a work in progress and does not represent government policy. A DESNZ HNTAS consultation this summer will continue sector engagement, and this work will put in place the missing piece of the heat network jigsaw, namely heat assurance. 

• Based on a paper presented at the 2024 CIBSE Technical Symposium www.cibse.org/symposium

About the authors: 
Professor Phil Jones is an independent consultant working on the DESNZ HNTAS team; Gareth Jones is managing director of FairHeat, the HNTAS technical author

The post Heat networks: countdown to regulation appeared first on CIBSE Journal.

The proposals, published in December, are intended to bring heat networks into the mainstream and create a viable route for occupiers to decarbonise their properties.

Identifying the lower-cost solution to decarbonising heat will lift the barriers to sector investment, the government says.

Justin Etherington, energy consultant and UK lead for the London energy team at Buro Happold, agrees that cost is key: ‘Heat networks will only succeed if they are competitive on cost and carbon compared with the customer’s alternative solutions.’

Other government initiatives around heat networks will also be vital, says Etherington. ‘Technical standards, policy support and standardisation of approach – as well as the introduction of Ofgem as the regulator – are all key elements in creating confidence.’

The proposals

The government is advocating the creation of a new Heat Network Zoning Authority (Central Authority), which will oversee all heat networks and coordinate zones in England, and Zoning Coordinators, which will implement zoning policy, and work with local authority planning departments.

To encourage investment, the government is proposing that certain buildings in zones connect to a heat network. These will be: new buildings that receive planning permission after designation of a zone; pre-existing communally heated buildings; and other non-domestic buildings that meet certain criteria.

The proposals state that zoning should encourage local authorities and other public bodies to connect their estates to heat networks because it is a cost-effective way to decarbonise. 

Baxi sales director Stephen Hart says it is notable that some housing developers are already choosing community heat networks for larger estates where it is financially more attractive than installing individual heat pumps and associated hot-water cylinders.

‘It would be even more attractive to connect these developments to larger heat networks, where they exist, as the developer can avoid the need to install and operate a local low carbon energy centre,’ he says.

Pre-existing homes with individual heating systems will not have to connect, but Hart says it can make financial sense. ‘Heat networks could prove popular in low-rise, low-density upgrade projects as a cost-effective alternative to individual heat pumps,’ he adds.

Emissions limits

The government is proposing that heat networks in zones will be required to comply with national emissions limits from 2030, and is seeking views on three proposals for this limit – 44g, 83g or 147g CO2e/kWh.

Etherington would opt for the stricter limit: ‘The 44g figure seems a reasonable number for new networks that have the opportunity to start with low carbon sources.’ 

Baxi would advocate for the highest possible carbon intensity at the outset, but with a reducing intensity threshold over time, says Hart, who notes that the current maximum carbon intensity for schemes to qualify for funding under the government’s Green Heat Network Fund is 100g CO_2e/kWh. This allows for hybrid energy centres with a low carbon primary heat source, such as heat pumps, to be combined with a boiler to satisfy peak demand.

Gas-burning boilers in hybrid systems could migrate to hydrogen or direct electric as technology evolves and the electricity grid is reinforced and expanded, adds Hart. 

The government estimates that heat zones could supply 11% of UK heat under its preferred policy option. This means that 70% of buildings that are not required to connect to a heat network in a zone will have to connect voluntarily. For this to happen, the government will have to win hearts and minds, says Etherington: ‘There will need to be significant education and engagement with customers to ensure they are confident in connection to heat networks in zones.’ 

The post Zoning in: the new Heat Network Zoning consultation appeared first on CIBSE Journal.

Bradford Energy Limited (BEL), a joint venture (JV) between 1Energy and sustainable infrastructure investor Asper Investment Management, has been established to construct and operate the Bradford Energy Network (BEN). In its first phase, the scheme will deliver up to 60GW of low carbon heat to existing buildings in and around the city centre, generated by a series of giant air source heat pumps (ASHPs) and distributed via a network of large, insulated underground pipes.

The £55m project is partly funded by a £20m grant from the UK government’s Green Heat Network Fund alongside private investment from the 1Energy/Asper Investment Management JV. 

‘We are, we believe, the first heat network developer to bring private sector investment into the UK market to develop projects at city scale,’ says Jeremy Bungey, executive director 1Energy Group. ‘In addition to Bradford, we have three other heat networks in development, and several others are in the early stages of going for grant applications to help meet our ambition of 10 city-scale projects over the next few years.’=

1Energy’s commercial case for developing retrofit heat networks is based on the need for 22 million existing properties to stop burning gas for heating by 2050, when the UK has committed to be carbon net zero. ‘Really, there are only a couple of options available to decarbonise buildings: an individual building heat pump or connection to a heat network,’ explains Bungey. He says the heat network solution is by far the most economical way to access decarbonised heat, with ‘total whole-life costs around 30% cheaper than building-specific air source heat pumps’. 

The government has yet to commit to a date for the phase-out of gas, so the challenge currently faced by 1Energy is persuading organisations to connect to the heat network. ‘The government has not yet said when gas will be banned or ruled out,’ says Bungey. ‘Without that clarity, what we’re trying to do is convince customers that it’s better for the environment, and for them, to connect now, and to be part of this decarbonisation agenda sooner rather than later.’

He believes the situation will improve once the government introduces heat network zoning to towns and cities (see box, ‘

Bungey will not say how many buildings have so far signed up for connection to the BEN because that information is ‘commercially sensitive’. However, 1Energy is talking to all the city’s major public sector bodies and colleges, its university, courts, and social housing providers, as well as the council about connecting its buildings and the town hall. 

‘As part of our Green Heat Network Fund application, we have had letters of intent and we’re progressing those contracts now with a lot of public sector bodies,’ Bungey says. ‘We’ve also identified a lot of private sector organisations that are on the route and we are having discussions with those too.’

To engineer the Bradford scheme, 1Energy is working with heat network specialist FairHeat. The biggest engineering and economic challenge with the BEN is the need to develop a district heat network based on electric heat pumps, as opposed to a gas combined heat and power (CHP) engine. 

‘CHP was very economical for district heating because of the power generation that those systems provide, but decarbonising
the Grid has meant we can no longer rely on that technology as a low carbon solution, so we have to look at using large-scale heat pumps,’ says Michael Ridge, principal engineer at FairHeat.

Perhaps the most difficult aspect of using heat pumps is pairing existing buildings, with their conventional radiator heating, with a low carbon heat network reliant on heat pump technology. ‘Most of the buildings we are dealing with are designed with classic 82^oC/71^oC radiator systems, whereas heat pumps like to generate low-temperature heat to improve their operating efficiency,’ says Ridge.

FairHeat’s solution for BEN is a hybrid system of heat pumps paired with gas boilers and a weather-compensated system. In winter, the primary pipework system will deliver heat at 80^oC, generated through a combination of ASHPs and the gas boilers. The boilers will add ‘a little bit more temperature than the ASHPs for when system demand requires a higher temperature’, says Ridge. 

Currently, the design is for 25% of the heat to come from the gas boilers, with 75% provided by the heat pumps. To achieve zero carbon, BEN will use green Grid electricity and offset carbon from gas usage.

Phase One of the heat network is expected to reduce emissions by 8,000 tonnes of CO2e per year

Adding weather compensation to the system ensures that high flow temperatures will only present when the weather is at its coldest. At higher external temperatures, the system flow temperature is reduced in line with a reduction in heat demand from the buildings. 

‘We drop flow temperatures on the network in line with what the buildings actually need, down to 65^oC in summer, which means we are maximising heat pump efficiency throughout the year,’ explains Ridge.

1Energy did look at having a lower system temperature, but the cost to customers of upgrading their heating system and enhancing the fabric of their buildings would have been prohibitively expensive. ‘We have had to drop a bit of system efficiency by raising the supply temperature, even with this weather-compensated approach, but it is far more beneficial to do this than to try to get customers to modify their systems, because the capital cost would have been too high to make it worth their while’.

Customers access the heat network through a plate heat exchanger, slotted into their existing plantroom as a replacement for gas boilers. Another major technical challenge is the need for the system to maintain a large temperature differential between system flow and return to further maximise heat pump operating efficiency. 

‘We have to design the system to provide the flow temperature needed to keep the buildings warm, but a lot of these buildings also have really poor temperature differential control. So while we might have a flow temperature of 80^oC, it might only drop to 75^oC on the return, when our system would prefer a much lower return temperature,’ explains Ridge.

Rather than simply dictate the temperature differential that a customer’s system has to deliver, 1Energy is funding FairHeat to undertake surveys of potential customers’ buildings and heating systems. These help 1Energy, which will be operating the network, and its customers understand the interventions needed to increase the temperature differential, and the potential cost of these works. Armed with building-specific knowledge, 1Energy and FairHeat can support customers with their Public Sector Decarbonisation Scheme grant applications. 

‘It’s been a significant investment in time, but we simply wouldn’t have got to where we are in terms of helping building owners figure out the best way to decarbonise and connect to our network,’ says Ridge.

For the BEN, the ASHPs will be installed in a purpose-built energy centre. The units will be split, with dry evaporators mounted externally on the building’s roof  and the decoupled 2MW compressors and condensers housed on the energy centre’s ground floor, along with the gas boilers. The compressors are modular so the system can be expanded as demand increases over time, up to 8MW. Refrigerant will be a blend of CO₂ and a hydrocarbon.

The proposed energy centre in Bradford

Externally, the energy centre is also home to three large thermal storage tanks, of almost 600m³ capacity in total. ‘The more thermal storage the better in terms of flexibility,’ says Ridge. As well as allowing 1Energy to charge the stores when electricity is cheap, the large thermal store means the heat network can reserve a portion of storage uncharged, so the energy centre can respond to requests from the Grid to take power by running the heat pumps even when customer demand for heat is low. ‘The bigger the thermal storage, the more opportunity we have to play to those different market opportunities,’ says Ridge.

Grid balancing is not included in 1Energy’s business case, says Bungey. ‘If we can take advantage of it, that would be great as an extra, but it’s not core to what we’re doing.’

1Energy is also looking to take advantage of waste heat sources to top up the system. ‘Because we are self-sufficient in heat provision, we can supplement the system with waste heat by paying appropriate prices for it,’ Bungey explains.

Being self-sufficient in heat is also key to providing a resilient supply of heat, because customers are used to having a reliable gas supply. ‘We are in control of the heat pump heat source and the back-up provided by the gas boilers and thermal stores; these can be supplemented with waste heat as and when opportunities arise,’ says Ridge

He adds that this approach has been adopted successfully in Scandinavia, where a network will start off with a strategy in terms of distance, customers and capacity, but then additional heat sources will feed into that over time, to ensure a lot more flexibility in how heat is provided. 

‘We can’t look at that end goal as our starting point, but we are really excited about that part of the journey where our pipes go past someone’s front door and they ask us about the network. It’s about getting the initial project off the ground and then seeing it grow from there,’ says Ridge.

Currently, the 400mm-diameter flow and return pipes to deliver low carbon heat from the energy centre to buildings in and around the centre of Bradford are being buried beneath the city. Eventually, a network of pipes will run from the energy centre in the west via two main spines that will deliver heat to where it is required. 

A challenge with the installation that 1Energy is working to overcome is the limitations of the supply chain in the UK, which, Bungey says, is populated by a number of mostly small players. 

Pipework is being installed beneath the city’s streets

‘What we’re trying to do is work with those smaller players to help develop the market and the supply chain – which we need to do because we are looking at installing networks in 10 cities at this scale,’ he adds. 

‘Each heat network package is worth tens of millions of pounds, which is often larger than the entire turnover of some of these organisations, so we have to work with them to share risk and to help them develop.’ 

The system is designed to only supply heat; there is no cooling planned for Bradford. ‘Very few of the existing buildings we will be connecting to have a significant cooling demand, so the network is all about heating and hot water,’ says Ridge. However, Bungey adds that there ‘might be an opportunity to do something’ in other cities depending on the cooling demand and the business case for investment.

Green electricity will be used to power the heat pumps. This makes the carbon content of heat supplied to customers about 59g CO_2e/kWh, which, Bungey says, is about a ‘75% carbon saving against a gas boiler’.

Clearly, heat networks have a role to play in helping the UK achieve its net zero targets. The Climate Change Committee has estimated that around 18% of UK heat – including domestic, commercial, industrial and public – could come from heat networks by 2050, a significant increase on the current figure of around 2%. In Bradford, phase one of the heat network is predicted to reduce emissions by approximately 8,000 tonnes of CO₂e per year. 1Energy is aiming to have heat on in April 2026, which will take Bradford a step closer to its net zero goal. 

The post Bradford’s cultural connection: a model for low-carbon district heating appeared first on CIBSE Journal.

Factors such as insufficient space for air source heat pumps (ASHPs), oversizing of equipment, noise, vibration, the importance of controls, and inadequate legislation were highlighted as key issues. The event, sponsored by Baxi and held in London, explored ways of optimising heating systems.

The participants began by describing their decarbonisation projects and challenges. Mathew Stark, a senior mechanical engineer at Hoare Lea, cited a current refurbishment scheme. ‘We wanted to remove the gas boilers and use an all-electric system with ASHPs, but planning restrictions wouldn’t allow anything too tall on the roof,’ he said. ‘The cooling system uses air cool condensers on the roof and chillers in the basement. Instead, we changed it from a constant air volume to a variable air volume system so we could at least make the system more efficient and decarbonise in that way.’

Simon Wyatt, partner at Cundall and chair of the CIBSE Knowledge Generation Panel, said many building owners are struggling with the best way to decarbonise existing buildings. They question whether they should do minor works now or carry out a deep retrofit over a phased period. Wyatt is involved in decarbonising many existing buildings. His dilemma is whether to try to keep a high-temperature heating system or upgrade the building’s fabric.

Richard Brimfield

‘The cost of electrification and heat pumps is expensive, but it’s a drop in the ocean compared with the cost of upgrading the fabric,’ he said. ‘If you want to hit those energy intensity targets, this is a real issue and there’s no coherent solution.’ 

Richard Brimfield, associate at Ridge and Partners, and founding committee member of the CIBSE HVAC Group, argued that some of the obvious challenges are finding external space for heat pumps and boreholes, identifying the heat requirement for existing buildings, and simulating how a heat pump operates. He said a current project had hugely oversized existing boilers.

The participants agreed that oversizing is a big problem. Ryan Kirkwood, engineering solutions manager at Baxi, asked whether there is now better guidance on the correct sizing of equipment within the industry. ‘Personally, I have more confidence in reducing the size of things by the methods we use to do the space heating calculations,’ said Brimfield. ‘However, we’re still oversizing things; we’re never going to get everything perfect.’

Daniel Skidmore

Wyatt said that CIBSE is considering producing guidance on efficient sizing. Although there seems to be more confidence in sizing central plant, he agreed that people are still oversizing significantly, partly because of build quality. He cited schools where there is a lot of leakage because of poor airtightness and air permeability, resulting in oversized radiators. 

Daniel Skidmore, director of building engineering at Aecom, echoed these views. He highlighted the BBC, one of Aecom’s biggest clients, which wants to decarbonise much of its estate. Some difficulties encountered with this project, he said, include how flow temperatures with hot water generation are used, roof-plant acoustics and vibration, and long lead times on plant, and how this can affect the project’s planning and timing.

Jeremy Owen, principal mechanical engineer at SVM Building Services Design, said the company is installing ASHPs for a major supermarket. The noise and vibration produced by the heat pumps has been a significant problem given the proximity of housing, he added, so – at some stores – a two-storey gantry has been built above the plantroom where the ASHP and new air handling unit (AHU) are located. 

Jason Donoghue

Noise and vibration produced by ASHPs is an issue that some manufacturers and noise specialists have said is often overlooked. Hoare Lea has an acoustics team that assesses the operation of the ASHP, and it advises architects on the type of materials and vibration mounts that should be used. ‘A lot of the kit we’re using with ASHPs is a set size, but massive generation packages are needed on site, so there are space constraints,’ said Stark. ‘The acoustics are achievable, but the space needed is challenging. So, before we even involve an acoustics specialist, we allow enough space for these packages for all residential projects, because we know we will need it.’

Owen’s other main complaint relates to the Building Regulations. ‘If we want to decarbonise, the regulations need to be amended to make it work and enable the best technologies to be put forward,’ he said, citing a frustrating experience he had with a residential new build. To achieve the SAP calculation, he had to install gas combination boilers with photovoltaics instead of heat pumps. ‘This is not right, because the SAP calculation looks at affordability,’ said Owen. ‘An ASHP is given a C rating because it’s less affordable, while a gas combi boiler with PVs gets an A rating; it’s ludicrous.’

Louis Kimber

Louis Kimber, mechanical engineering technician at AtkinsRéalis, said embodied carbon is a growing issue. He has been working with the Government Property Agency’s (GPA’s) UK sites and exploring what can be done to decarbonise. 

‘Embodied carbon is not a criterion required by the GPA,’ said Kimber. ‘But when I’m writing the reports and suggesting things such as getting rid of boilers and installing PVs on the roof, not only are the costs increasing, but the embodied carbon is going up too, which really concerns me.’

Kirkwood said it was refreshing to hear his own concerns echoed. ‘We find there is a great deal of confusion and people are often looking for a quick fix,’ he added. ‘Engineers need time to engineer, to survey and to monitor. As an industry we’ve almost engineered that out and we need to engineer it back in.’

Matthew Stark

To optimise heating systems, Skidmore recommended metering be installed in existing buildings, to help understand heating use. An existing system with lower temperatures should be run to see how it behaves. Suggested improvements, he added, have included upgrades to building fabric, the introduction of ventilation, using domestic hot water with AHUs, and providing enough space for airflow in heat pumps, as correcting flows can be a problem. 

Skidmore also recommended using high-efficiency chillers to take the rest of the cooling, instead of implementing a blanket approach. In buildings that have a 24/7 operation where there is a constant cooling demand, he has taken advantage of the waste heat element of ASHPs. However, he argued that ASHPs are the biggest offenders in terms of energy consumption, because they are not being controlled properly.

Ryan Kirkwood

‘We often find that buildings aren’t running as smoothly as they should. They are sometimes running at night when they shouldn’t and not ramping down enough when they should,’ said Skidmore. ‘The controls element has been as much a culprit as the plant. We often find that there has been a lack of engagement with the facilities management [FM] team regarding the controls. There have also been issues with the FM team’s expertise of optimising and running the buildings after we’ve done the work.’ 

To optimise heating systems in a supermarket, Owen said they rely on a packaged plant, which is a refrigeration integrated heating and cooling system. It takes the heat of the cold aisles and puts it back into the store, and there are a couple of heating coils in the AHU. 

It was agreed that education would help in situations where a setting has been changed after it was established to optimise heat rejection. Wyatt added that the design performance assessment will possibly shed light on this issue; however, many of his clients don’t take this assessment seriously enough. ‘We have 30-odd projects that have gone through design performance assessments and got their energy target rating,’ said Wyatt. ‘But not one will get anywhere near those targets. The assessment is a de-risking exercise with multiple future scenarios. It’s not like an energy performance certificate, where once you’ve passed it can be forgotten.’

Jeremy Owen

Brimfield then raised the importance of controls and the role artificial intelligence (AI) may have. Wyatt suggested there are two schools of thought: take the fully automated AI path, which seems to be the direction industry is taking, although its complexity and cost can be a barrier; or keep things as simple as possible.

The event concluded with a discussion on hydrogen being piped through the gas grid and the possibility of having localised gas storage. Skidmore said Aecom is focusing on the big district heating schemes and rolling out large projects with low carbon distribution, but he doesn’t predict hydrogen playing a major part.

Baxi has developed and tested 100% H2 boilers, and the tests prove they work just fine said Kirkwood. He says that when there a wide availability of H2, production will start. ‘We have hydrogen boilers installed in a variety of demonstration projects across the EU and UK proving that the technology is a viable solution,’ he added. ‘We’re doing what we believe is the right thing, but we’re not hanging our hat on that. We see a blended source of solutions, including heat pumps, heat networks, and, if required, hydrogen.’

Simon Wyatt

Jason Donoghue, head of marketing at Baxi, said the company had launched two more residential projects, and Baxi will be supplying hydrogen boilers to a new residential trial in Redcar. Kirkwood added that he would like to see a greater focus on heat networks. ‘One of the challenges we face is the medium-temperature heat networks,’ he said. ‘We have a huge number of heat networks sitting on the Grid that are not low carbon. Systems operating beyond where current heat pump trajectory is in terms of performance will be challenging. There’s a dichotomy between heat pumps and heat networks – they are not well suited, which is why we are investing in thermal storage research and development.’

Skidmore argued that it can be challenging to drive heat network improvements, and Wyatt agreed, adding: ‘District heat networks for existing high-density urban environments have a place, but in low-rise density, heat networks are not always the right solution.’ 

The post Taking the heat out of decarbonisation: insights from CIBSE’s roundtable appeared first on CIBSE Journal.

The April event in London, which focused on optimising HIUs in district heating systems, was sponsored by Ideal Heating – Commercial Products. Among the topics discussed were: high return temperatures and poor efficiencies in energy centres; lack of consistency in design teams; and the latest updates to testing criteria for HIUs.

HIUs have many benefits. They offer individual heat control, energy efficiency, and cost savings by allowing residents to adjust temperatures according to their needs. They provide flexibility by accommodating different heat sources and integrating renewable energy technologies.

They ensure a reliable supply of hot water to each dwelling and enable system monitoring for optimisation and maintenance.

Overall, HIUs can enhance comfort, minimise waste, and promote more sustainable heating systems but they have to be integrated into heat network systems properly for performance to be fully optimised.

Ben Farmer, principal design engineer at Metropolitan, highlighted the relationship between energy centre performance and commissioning of HIUs. He said that high return temperatures and poor efficiencies in some of the schemes he has worked on usually start with HIUs. ‘It’s vital we get HIUs set up correctly and performing as intended. If it’s not done properly, it can hold up a scheme and developers can’t hand over on the timescales they want.’

Farmer added that design teams are winning work when they have no history of a project, and the client’s project personnel are also changing. This means vital information is not being transferred from one project to the next. ‘It’s like swimming upstream all the time; some headway is made, but suddenly a strong current comes along and you’re almost back to where you started,’ he said.

Hugh Dugdale, associate principal at Introba, agreed, and said that it’s often because of the way contracts are broken down. ‘We are employed to design the primary plant up to the HIU and then the apartment is handed over to another consultant; those two interfaces are not working well together,’ he said.

Dugdale argued that people don’t understand the complexities of a primary system, which is very dynamic, and that knowledge isn’t carried through in the way contracts are executed. These problems stem from a lack of education and information on HIUs, added Farmer. ‘Something as fundamental as design flowrates aren’t being provided at a detailed design stage; critical information is not being passed through from design to commissioning,’ he said.

Gareth Jones, managing director at FairHeat, supported this view. ‘We’ve got a big industry issue around skills and commissioning,’ he said. ‘When we look at the original setup to make sure HIUs have been installed correctly, we often see that they have been recommissioned because there’s been a wave of poor performance across the heat network. We need better education on how these systems work.’

Jairo Jaramillo, associate mechanical engineer at HDR, has had similar experiences. ‘On larger residential schemes with bigger budgets, the commissioning consultant holds your hand throughout the whole process and it’s a very well-documented approach,’ he said.

‘Then there’s the other experience, which is completely haphazard. Most of our fee will be from stage two to four, and at stage five. It’s still our responsibility, but we have less input. We watch our carefully designed systems getting installed and commissioned in a poor manner, resulting in inefficient heat networks.’

Michael Benbow, senior engineer at Buro Happold, argued that more engineers are needed to design correctly to ensure there are fewer issues. ‘We need better education at consultant level, to design and commission HIUs,’ he said. ‘That gives installers the opportunity to get the figures, temperatures and efficiencies that were designed.’

Unlike traditional heating appliances, which require registration with a body, there isn’t a scheme or certification required for commissioning HIUs, said Charlie Mowbray, senior product manager at Ideal Heating Commercial, part of Groupe Atlantic. ‘The industry could develop training schemes and opportunities to certify people so they have a greater depth of knowledge, or develop a similar benchmark scheme to the one for boiler installation.’

Jones, who chairs the UK HIU steering group and technical committee for BESA, and is technical lead on the Heat Network Technical Assurance Scheme, said a skills gap has been flagged as a serious issue and a team is looking at this. ‘The feedback from people on the skills course is that standards need to be in place first,’ he said. ‘What we will probably see is an evolution – the standards will come first, requirements will be made, and then courses will follow.’

A technical assurance scheme minimum standard for heat networks has also been proposed, added Jones. This means all heat networks will need to be certified and this will come into force, alongside the regulations, towards the end of 2024. Designers will have to produce better designs, contractors will have to install better networks, and operators will have to improve in-use performance.

Jones outlined some of the proposed updates to the BESA HIU testing regime. There will be a move towards a modular system, whereby domestic hot water (DHW)and space heating will be tested separately. Initially, seven HIU types will be allowed, including direct and indirect, and there will be pass or fail criteria, minimum standards will be set, and the number of tests will be changed. ‘The one big change will be the temperature regimes,’ said Jones. ‘In preparation for heat pump systems, the lower temperature will shift from 70°C to 55°C, which will be a challenge on the performance of DHW, particularly relating to response time and temperature stability.’

Mowbray was enthusiastic about the updates to HIU testing. ‘To have a pass or fail criterion is like a line in the sand; there’s no grey area any more,’ he said. ‘Having a broader range of tests increases the amount of knowledge that people will have when considering HIUs and will enable better selection for the right application.’

The ambition of the minimum requirement for HIUs is for people to do better, stressed Jones – but it must be achievable. Consultants need to look at the information available that shows how HIUs perform; for example, DHW temperature stability at low flowrates should be considered. Jones added that operating data needs to be available that shows the performance of HIUs in situ.

Dugdale agreed that data based on reality is key, and said that, in his work, there has been a massive call for anonymous data that relates to the net zero carbon building standard. ‘We’ve had a very good response and are at a stage where anything meaningful is being extracted,’ he said. ‘Hopefully, a lot of the stuff in the standard will be based on that data collection.’

Dugdale doesn’t yet know how this standard will work with heat networks, but from the data studied so far, he thinks direct HIUs will potentially reduce the embodied carbon more than indirect HIUs.

The discussion turned to the opportunities of retrofitting HIU systems. According to Jones, this process can be straightforward, involving installing heat pumps pipes through the building, removing the gas boiler, and replacing it with an HIU. FairHeat had successfully put a 55°C heat network into a 50-year-old building, he said, and it has a good template for end-of-life gas boilers. When asked what the plant room implications are of changing from gas combined heat and power (CHP) systems to heat pumps for existing HIUs, Jones said operating temperature is the important consideration.

‘The good news is that the industry has been so cautious to date that almost all the systems, including radiators, are oversized and loads have been estimated to be too high – which means heat network temperatures could be dropped and it will be fine,’ he added. ‘The real challenge though is generating DHW but most of the time there is a way through this.’

Farmer echoed Jones’s comment about oversized systems. ‘They are massively oversized,’ he said. ‘We’re involved with Buro Happold in high-rise housing projects that date from 2016, where we are removing gas as a primary source of heat generation and putting in heat pumps. The challenge we had was dropping temperatures and working out what the impact would be.’ However, in most heat networks that employ electric heat pumps, gas boilers are still used as backup, added Jones.

Jaramillo suggested there shouldn’t be one size fits all and reliance on a single energy vector. ‘It’s very brave to suggest to clients that a project doesn’t have to be all-electric and that it’s acceptable to propose other solutions,’ he said.

Robert Temlett, senior design engineer at Metropolitan, questioned whether key performance indicators will be monitored as part of the proposed certification of heat networks. ‘We had a huge problem where the industry was pushing CHP and gas boilers, and the CHP just sat in the corner and did nothing. The challenge is, how do we optimise the system to be cost-effective while considering constrained issues?’

Jones said engineers must be aware that a lot of heat networks being installed are communal or semi-communal, and the developer-led networks are quite small. ‘In 20 years’ time that kit probably won’t be there,’ he said. ‘We will have a heat network coming through and will connect to it from these big urban centres.’

With new heat network regulations and the industry committed to upskilling workers, the foundations are being laid for the large-scale roll out of high performing heat networks and HIUs. Ideal Heating – Commercial Products is among companies helping to close the skills gap and increase innovation and performance in the sector. ‘We’re building a research and development facility, and we have a new training facility in Hull. There is so much more going on,’ says Richard Brown, head of specification sales at Ideal Heating – Commercial Products. ‘We had HIUs for several years. We need to get the message out there.’

The post Sponsored roundtable: optimising heat interface units appeared first on CIBSE Journal.