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 iconic landmark is Grade II* listed, which means the building had to be preserved in its redevelopment. ‘The biggest challenges in terms of MEP were in maximising the net lettable areas and ensuring compliance with the building’s Grade II* listing requirements,’ says Simon James, associate director at ChapmanBDSP.

The building services design also had to take account of the fact that the power station was built in two halves, decades apart. Designed by architect, Sir Giles Gilbert Scott, who also designed the red telephone box, Battersea A was completed and opened in 1933, with one turbine hall and two slender chimneys.

It was not until 1955, when the eastern half of the building, Battersea B, was completed that the building acquired its familiar four-chimney profile. The chimneys were needed to disperse the flue gases from the power station’s pulverised coal-fuelled boilers, which generated the steam that spun its giant turbines to supply a fifth of London’s electricity. 

The last of the building's four chimneys was completed in 1955

Post-industrial plans

Over the years, Battersea Power Station became an instantly recognisable feature of the London skyline, and starred on the cover of Pink Floyd’s 1977 album Animals, for which it was photographed with the band’s inflatable pig flying between its chimneys. 

With operating costs increasing, however, and output falling with age, Battersea A closed in 1975, and Battersea B was decommissioned in 1983. The challenge then was what to do with this giant, brick-built landmark in post-industrial Britain.

The atrium lets daylight seep onto the floorplates

A series of failed proposals for the 42-acre site followed the decommissioning of the power station. These included: Alton Towers-owner John Broome’s plans to turn the power station into a theme park; a proposal for it to become the permanent home of Canadian entertainment company Cirque du Soleil; plans to turn it into a public park; and even a proposal to turn it into a football stadium to become the new home of Chelsea FC. 

However, in 2012 a consortium of Malaysian companies bought the derelict site to turn the power station and its surrounding 42-acre site into a mixed-use development incorporating residential, retail, office and leisure.

Phasing in change

In 2013, architect WilkinsonEyre and engineers ChapmanBDSP were appointed to restore and repurpose the power station structure under Phase 2 of the site’s redevelopment. 

Phase 1, Circus West Village – designed by SimpsonHaugh and De Rijke Marsh Morgan – was completed in 2017 and is now home to more than 2,000 people. 

Phase 3, Prospect Place and Electric Boulevard, a new pedestrianised high street, is under construction, with more residential apartments, designed by Gehry Partners and Foster + Partners, as well as new retail space and a hotel, due to open shortly.

Two floors of retail space are accommodated in what was the old boiler house

It is Phase 2, the repurposing of the power station, that is key to the scheme’s success. At the heart of WilkinsonEyre’s design is the central Boiler House, which now accommodates three floors of retail and leisure. On the third floor are two cinema screens, an events space and offices for flexible working. Floors five to 10 also accommodate 46,000m² offices. 

Flanking the main power station walls, to the east and west, are the two giant turbine halls. These are now home to three floors of shops, restaurants and unique event spaces. Adjacent to the turbine halls are the meticulously restored original control rooms, and flanking each of the turbine halls are the former switch houses, which contain more residential apartments. Visitors are able to board a glass lift, Lift 109, to take them to the top of the north-west chimney to enjoy views of London, 109m above sea level.

Battersea ceased generating power in 1983

Pitch and plant

The giant double-height plantroom takes up almost the entire fourth floor of the repurposed power station. ‘It’s probably bigger than a football pitch,’ says James. 

It is sandwiched between floors in the centre of the building for sound commercial reasons; it kept the ventilation ducts to a manageable size, rather than having to deal with huge ducts dropping down from roof-top air handling units (AHUs). It also had the benefit of freeing the roof from building services plant, creating space for more housing. 

‘Putting the plantroom in the middle helped maximise the lettable area because smaller ducts go up and down from it, rather than having large ductwork dropping down the building from the roof,’ explains James.

The plantroom accommodates more than 25 AHUs. Ventilation intake louvres are located in the wall on the western side of the plant floor, while the exhaust louvres are concealed in rooftop gardens above the turbine hall, to the east of the plantroom. Ductwork and piped services are distributed via risers concealed in the rectangular wash towers that form the base of each of the four chimneys and in four new access cores constructed in the centre of the building to accommodate lifts and stairs. 

James says it was a challenge coordinating the various plant and pipework with the new supporting structure that now fills the space. Coordination was helped by the project being designed in BIM. At its peak, ChapmanBDSP had a team of 25 BIM operators working on the scheme. 

‘A major challenge with this project is that there is no repetition in terms of risers and floor plates; everything is a bespoke design to accommodate the listed structure,’ he explains. 

Down in the basement

Heating and cooling for the entire scheme is provided by a new energy centre located in the building’s basement. It was designed by Vital Energi and is currently being run by Equans.

Turbine hall A’s art deco interior with fluted pilasters and creamy tiles

The energy centre includes two 2MWe gas combined heat and power (CHP) engines, one 3.3MWe gas CHP engine and three 10MW gas-fired boilers, plus seven 60m³ thermal stores and six 4MW chillers. Flues from the boilers and CHP engines use the power station’s north-east and south-west chimneys.

James says ChapmanBDSP worked with Vital Energi to provide it with estimated energy loads for Phase 2 of the project: ‘We designed the networks that distribute the LTHW [low temperature hot water] and chilled water from it using efficient variable volume systems.’ 

Alongside the energy centre, the basement is home to the building’s 19 electrical substations. Rather than incorporate standby generators, ChapmanBDSP has saved floor space by bringing in two separate electrical supplies. The project’s 14MW load is supplied by two 7MW supplies taken from the Stewarts Road substation. 

ChapmanBDSP’s scheme also eliminates the need for heating and cooling plant to serve the two retail malls that now occupy the turbine halls, which flank the main Boiler House building. 

Luxury residential 'Sky Villas' are accessed via a glass lift at the base of one of the chimneys

Styling it out

The interiors of the two halls reflect their different ages: Turbine Hall A has an art deco interior with fluted pilasters and creamy tiles; Turbine Hall B was built after World War II and has a more utilitarian feel. Both turbine halls have the outlines of the generators that once filled the space with noise and movement picked into the floor finish.

‘We were able to thermally model the two turbine halls to demonstrate to the client that the thermal comfort aligned with CIBSE guidance, which saves on plant cost and energy use,’ says James. 

Thermal mass, a small amount of solar gain and some beneficial heat from the retail units will ensure visitors remain comfortable in winter. 

Both turbine halls incorporate smoke-extract fans at high level to pull smoke out in the event of a fire. These provide yet another example of ChapmanBDSP’s approach to delivering value on the project. 

Rather than install additional ventilation plant on the roof, ChapmanBDSP has used the smoke-extract fans to increase ventilation rates, by helping pull air in through the main doors and exhausting it through the roof. 

‘Because the Building Regulations call for fresh air to be supplied to the turbine halls, we have agreed with building control that we will use CO₂ sensors to run the smoke-extract fans at low volume in the unlikely event that there are so many people in the turbine halls that CO₂ levels rise significantly,’ says James.

Cool control

Adjacent to the turbine halls are the original control rooms, with their walls of knobs and dials gleaming like new. 

Control Room A is the most impressive, with the banks of breakers – labelled with place names such as Carnaby Street – illuminated by an ornate art deco-glazed ceiling. This is a private events space that will be open to the public on certain occasions. Control Room B, which was built later, is more industrial in design and is now an all-day bar. 

The two control rooms have been meticulously restored to be an events space and a cocktail bar

These spaces were originally naturally ventilated. However, because both control rooms are listed, the spaces are now heated and cooled using conditioned air, supplied through existing grilles at high level to the space.

Worth the wait

It may have taken almost four decades and numerous failed development proposals, but Battersea Power Station is finally open to the public, The scheme will benefit the local and wider community, Londoners, and the UK economy, while saving and celebrating the building’s original features – bringing the structure to life once again.

The post Case study: Battersea Power Station appeared first on CIBSE Journal.

It has been found that 15% of heat networks within the UK require unbudgeted remedial works within the first two years, and the majority of these are probably because of a lack of understanding of the importance of maintaining water quality ¹. If suitable procedures are introduced via additional technology, it can only improve the cost and operating efficiencies of heat networks and play a large part in decarbonising heat in the UK.

Other qualitative benefits include: removal of sampling ambiguity at the pre-commissioning phase; instantaneous identification of changes to water quality via alarms; improved visibility on system water chemistry throughout a project lifetime; and increased accountability and improvement of contractual lines and accountability.

The qualitative benefits highlighted above, however, can only be realised if the installation and operation of online monitoring equipment shows cost improvements when compared with conventional sampling and monitoring methods.

The study ¹ investigates the key parameters that are most influential in determining water quality and the ability for the system water to deteriorate system components. These have been categorised as a lead indicator (identifying when a system moves towards corrosive conditions) or lag indicator (identifying when corrosion has already occurred) across oxygenated and de-oxygenated systems, to enable targeted selection of parameters for online water-quality monitoring. 

The financial assessment of two online monitoring arrangements have been conducted across three different-sized residential heat networks over a 20-year period (Table 1). Each online monitoring regime has subsequently been compared against the recommended sampling approach stated in BSRIA BG 29 and BSRIA BG 50.

It is well documented that three key parameters can identify if conditions are favourable for corrosion to occur: pH, electrical conductivity, and oxygen content². Additionally, system pressure control and fill-water monitoring are identified within literature as of high importance to ensure the system is adequately protected from oxygen ingress and inhibitor depletion (where applicable).

Introducing high volumes of fill water into the system can also indicate if leaks are occurring, providing insight as to whether the system is watertight. To maintain control over water quality, the amount of fill water entering a system should be measured and routinely checked, regardless of the methodology – de-oxygenated or chemically dosed – used to maintain water quality.

Categorising all water-quality parameters into lead and lag indicators adds weighting to the parameters that identify when system water trends towards corrosive conditions before corrosion occurs. Therefore, monitoring lead water quality parameters continuously increases the effectiveness of the online monitoring equipment, enabling proactive maintenance works to take place before (significant levels of) corrosion takes place. 

Because of the increasing uptake of de-oxygenated systems within the UK, this study was conducted over conventional dosed and de-oxygenated systems. 

De-oxygenated systems provide a more clear-cut set of monitoring parameters because of the lack of complexity within the water chemistry. De-oxygenating a district heating system would shift the relevant guidance documents from BSRIA BG 29 and BSRIA BG 50 to the German water standard VDI 2035. 

Monitoring options 

Regardless of the system type, the monitoring parameters with the highest relative importance are consistent and in line with literature findings.

The following combinations of monitoring options have been selected for life-cycle analysis based on the key parameters highlighted above across both systems. 

Option 1 monitors all the parameters with a relative importance deemed greater than a value of 3, shown in Table 1 within a single monitoring unit. 

Option 2 provides analysis on a hybrid monitoring regime with standalone probes for all key monitoring parameters with a relative importance greater than 4.

The results from the financial assessment show there is good economic feasibility for online real-time water quality monitoring. The increased capital investment upfront is quickly recovered by the reduced requirement for sampling to BSRIA BG 29 standards during the commissioning phase before system handover. 

From an install and commissioning perspective, installation of online monitoring would be economically viable in cases where larger system sizes and longer commissioning phase durations are present, as the cost variation from sampling is improved. 

The overall net present value observed at system handover and year 20 are significantly impacted by an increase in commissioning phase duration of a project, regardless of system size. Although overall costs increase with extended handover periods, the financial benefits of having online monitoring installed are reduced compared to BSRIA sampling. This is because of the costly nature of laboratory sampling every fortnight.

There is good financial benefit for both online monitoring options over a 52-week period, regardless of system size, and it could be considered financially beneficial to install temporary monitoring during the development commissioning phase.

Post-handover maintenance of the system, with the additional maintenance costs incurred by the monitoring equipment, increases overall water quality parts per million costs by around £1,300-£3,000. However, the improved visibility and control on water quality enables cost reductions on reactive maintenance works, heat interface unit servicing time costs, and major equipment replacement costs. 

It has been found that online monitoring equipment is economically viable for medium and large systems. The relative costs recovered by improved operation of small systems does not outweigh the increased equipment maintenance costs. So, installation of online monitoring equipment on small hydraulic systems is not recommended. 

For more information
To read the full research paper, visit the FairHeat website bit.ly/CJOct22PB

About the author
PeteR Horne is a consulting engineer at FairHeat

References:
1 J Greaves, Water quality assessment in UK district heating systems, CIBSE, Sheffield, 2019
2 R Thorarinsdottir, L V Nielsen, S Richter and T Hemmingsen, Monitoring corrosion in district heating systems, The Icelandic Building Research Institute, 2004.

The post Monitoring the situation: cost effective remote water quality testing appeared first on CIBSE Journal.

To assess how the heat sector can transform in a technically, economically and environmentally appropriate way in such a short period of time, researchers at the University of Aalborg (AAU) developed the Heat Plan Denmark 2021. This document sets out how the heating sector can transform relatively quickly using technologies that are already available. See panel, ‘Heat Plan Denmark: key messages’.

The Hornsyld Project is a good example of how Hornsyld-Bråskov local council is planning to apply the Heat Plan Denmark 2021 by using heat from industrial processes – specifically from drying beans used for animal feeds –to transform the heat supply for Hornsyld’s 1,600 inhabitants, as well as schools, sports facilities and businesses.

Hornsyld is a compact town with a relatively high density of heat-consuming buildings, with a peak heat load of 5.3MW. Currently, the majority of its dwellings and businesses are heated by individual natural gas boilers.

The local council is proposing to install a new district heating system to use the large amount of heat being lost to the atmosphere by Hornsyld’s industries. The two main industries in the town are Triple A, an animal feed producer, and Hornsyld Købmandsgård, a grocer and agro-business that grows horse beans (a member of the broad bean family) for use in animal feed. The waste heat for the scheme will come from a feed dryer at Triple A.

The drying process uses air heated directly by the combustion of natural gas. This air is drawn through the feed, which evaporates approximately 6,000 litres of water an hour. Currently, the hot and humid exhaust air is discharged to the atmosphere at a temperature of approximately 60°C.

Under the council’s proposal, a scrubber will be used to wash the exhaust air with cold water to condense the vapour from the air stream. A heat pump will extract heat from the warmed condensate and then raise its temperature to the outlet temperature for the district heating supply.

The process is expected to produce between 4MW and 5MW of heat. However, only 3MW will be used for this project, consisting of 2MW supplied by the heat pump and an additional 1MW from direct exchange. The feed dryer is expected to run for a minimum of 7,500 hours per year. Heat production is calculated to give a system coefficient of performance (COP) of 6.75.

Two boilers at Hornsyld Købmandsgård will be used to supplement the reclaimed heat from Triple A. One is a 1.8MW unit fuelled by biomass – which is primarily waste material from grain products – and the heat is mainly used for process heating for Triple A. When production is under way at Triple A, only 0.9MW of capacity will be available from the biomass boiler.

The boiler is also used to produce heat for Hornsyld School, Hornsyld Købmandsgård, and a few other nearby buildings, all of which are expected to be included in the district heating system, so this element of boiler capacity will be available to the network.

The other Hornsyld Købmandsgård boiler is a 4MW oil-fired boiler. This will be converted to run on natural gas, and will  serve as a back-up to the biomass boiler. It is assumed that 3.5MW of capacity will be available for the district heating supply. The operational and maintenance costs of both boilers will be covered under the scheme.

Waste grain products will provide fuel for a 1.8MW biomass boiler

To provide a buffer between the heat demand, production at Triple A, and the operation of the boilers, the system will incorporate a 1,000m³ thermal store. The addition of a storage tank will allow greater use of the available waste heat and the biomass boiler.

There is currently no heat network in Hornsyld, so a new plantroom will be constructed. Heat will be distributed via a pre-insulated, twin-pipe system.

Planenergi, the consulting engineers responsible for the project, are continuously updating the project as certainty increases around customers numbers, and energy costs rise. SAV Systems are PlanEnergi’s design partner in
the UK.

Anchor loads

Of the 471 buildings supplied by natural gas in Hornsyld, there are 29 large heat consumers, with an annual heat demand of more than 100MWh. Together, they could amount to a heat demand of more than 9,000MWh annually, which will provide  sufficient anchor loads for the heat network. The council hopes that a high connection rate can be achieved by signing up these large consumers so that the project is less dependent on getting a high take-up from large numbers of domestic customers.

The heat network is designed to supply 100% of Hornsyld’s heat demand. However, the project has assumed a total connection rate corresponding to 60% of the heating demand, and it is expected to be converted at the rate indicated in Figure 1. A total annual heat loss of 15.2% has also been calculated for the network, corresponding to 2,942MWh/year. This gives a total heat requirement of 19,395MWh/year.

Cost savings

The project is expected to provide an annual cost saving of 6,300 Danish kroner (DKK – about £700) for a typical dwelling currently heated by natural gas, and DKK 5,400 (about £600) for one heated by an air-to-water heat pump. The savings are well above the minimum set by the Danish Project Evaluation Act, which requires a cost saving of £170 per household for a project to be approved.

An estimated socio-economic surplus of £4.1m has been identified for the project over 20 years, largely because of the reduction in natural gas consumption, which more than offsets the investment cost

The post Keen beans: The Danish village tapping into industrial waste heat appeared first on CIBSE Journal.

As part of the engineering value and technical design exercises undertaken by the GreenSCIES team, various design options have been developed, aiming to overcome the challenges presented by congested streets. These include running pipework in above-ground planters, in flying planters, and through trenches shared with other utilities.

The GreenSCIES project is led by London South Bank University (LSBU) and funded by Innovate UK, part of UK Research and Innovation, through the government’s Industrial Strategy Challenge Fund Prospering from the Energy Revolution programme.

The aim of the project is to develop a construction-ready design for a scheme that tackles fuel poverty by providing a significant reduction on consumer bills, delivers large reductions in air pollution, and improves local skills, jobs and economies.

Our GreenSCIES consortium is at the forefront of new applications where heat/coolth can be shared across ultra-low temperature networks, and these new approaches present even greater opportunities to move closer to net-zero carbon.

The GreenSCIES system will deliver low carbon heat, cooling, and power, supplying many urban residents and local businesses. It is based around a fifth-generation ambient-temperature heating and cooling network loop (5DHC), a concept that includes decentralised energy centres and heat pumps in each building. The network can share heating and cooling between buildings providing even greater carbon savings than third- and fourth-generation medium-/low-temperature networks.

The GreenSCIES ambient loop, which is designed to be as low as 15°C flow, will be using waste heat from a local data centre and borehole aquifer water to provide the heat source for water source heat pumps that can supply buildings at temperatures up to 80°C. In addition, the aquifer will be used to provide a balancing mechanism for the network and long-term thermal storage through an innovative concept called aquifer thermal energy storage.

Novel heating and cooling distribution

The traditional approach to energy network distribution in existing urban settings is to bury pipework and ductwork in below-ground trenching, typically hidden from view beneath carriageways and footways. From a technical viewpoint, for an ambient-loop network as proposed for GreenSCIES, this approach benefits from the steady environment of the ground cover, protecting pipework from disturbance, and mitigates any visual ‘intrusion’ at street level.

The four lead distribution pipework routing concepts. Credit: Cullinan Studio

However, trenching in a dense urban borough – where pavements and roads are already heavily populated with existing utilities and other unknowns – attributes a large risk to the project, particularly when proposing for construction contracts where allowances for the unknown could push costs to a prohibitively high level.

As the GreenSCIES network has been designed as an ambient loop, there are fewer technical restrictions on locating pipework – for example, less need for preventing heat losses from the pipes because of the near-ambient flows. So, the GreenSCIES team took a hypothesis of routing distribution pipework above ground and explored the technical, economic, spatial and social implications of this approach. A more detailed discussion of the approach and the results were presented at the CIBSE Technical Symposium.

The vision in GreenSCIES is to design a technically viable, smart local energy system while improving the locals’ lives by creating more liveable spaces.’

Concept proposals

GreenSCIES consortium member Cullinan Studio has been appraising several alternative approaches, some of which are related to the integration of pipework with public-realm interventions as an alternative to digging.

The options developed for appraisal took on board technical guidance from third-party product manufacturers, specialist contractors and engineering consultants.

Kristina Roszynski, of Cullinan Studio, said: ‘Cullinan Studio is committed to restoring the connection between nature and people. The 5DHC network infrastructure can provide wider benefits for the local community, such as an opportunity to improve their streets through adding bio-diverse planting as part of above-ground pipework distribution.’

The four lead distribution concepts appraised are:

1. Hard dig trenching in carriageway
2. Soft dig trenching in landscaping/verges
3. Above-ground distribution planters
4. Above-ground road-crossing or building-mounted distribution planters.

These options have been appraised against social, environmental and practical criteria, with a focus on adding value to the public realm, reducing risk and minimising disruption to public life. The Viability Matrix has been published and discussed in detail in the full Technical Symposium paper Engineering value and innovative design options for smart local energy systems.

One of the novel concepts developed involved planters that conceal raised pipework, laid parallel to the carriageway, creating a green buffer between people and vehicles (option 3). The addition of plants along roadways is proven to improve air quality for people walking alongside busy roads and can mitigate the heat island effect in cities.

Explored alongside these concepts, is the potential to integrate photovoltaic panels, e-mobility and smartphone charging hardware into planters and street furniture at strategic points along the pipework route, to address the mounting levels of ‘street clutter’.

Of course, to understand the maintenance requirements of any above-ground options, the long-term horticultural maintenance of the planters, for example, is absolutely crucial and should be considered – and planned for – at the design stage.

In conclusion, we believe that the challenge to develop smart local energy systems around 5DHC networks requires a holistic approach from an integrated technical design team, commercial investigations, and community engagement. We are committed to the co-design of the 5DHC network as part of our community engagement strategy, to ensure that no-one is left behind in the energy transition. Some of the concepts presented are an entirely different way of thinking about the problem of pipework routing and offer a new approach to implementing this form of infrastructure.

The work shows that there are considerable benefits in some of these innovative approaches that have not, generally, been considered in more traditional heat-network projects. Implementing such novel approaches with multiple economic, environmental and community benefits will be critical in future urban energy networks.

About the author

Dr Akos Revesz is a senior research fellow at London South Bank University and technical lead at GreenSCIES

The post Above and beyond: Heat network pipework design appeared first on CIBSE Journal.

The Queens Quay energy solution has two 2.65MW ammonia water source heat pumps, built by Star Refrigeration, and a 130m³ thermal store at the heart of the low carbon system. This provides around 80% of the 51,000MWh annual heat demand, with the remainder supplied by backup, gas-fired boilers. There is also scope for two heat pumps to be added as the build out progresses and the heat demand increases.

The colourfully lit chimney contains the heat pump ventilation system and includes the emergency ammonia purge system, which ensures there is adequate dispersion and no impact on locals in the event of a leak. Three boiler flues also terminate in the chimney.

A riverwater abstraction system has been installed at the Queens Quay Basin, which takes water from the river Clyde and circulates it through the heat pumps, before returning it to the river, with a stipulation that it cannot be returned more than 3K cooler than its original abstraction temperature.

The heat pump converts the latent heat from the river into low-temperature hot water, which is distributed via a 1.5km district heat network serving the 23-hectare development. It will eventually serve 1,200 homes, and the associated infrastructure needed to support them, such as health centres and commercial facilities.

Delivering a hybrid district heating system

While the heat pumps were capable of supplying heat at 80°C+, there was strong motivation to lower the low-temperature hot water (LTHW) flow temperature as much as possible, because every 1K reduction resulted in an increased heat-pump efficiency of 1.5%. This created a dilemma for the designers, who would need to keep temperatures relatively high to meet the needs of the existing buildings, but low enough to get maximum efficiency from the pump. 

Historical heating systems served by gas boilers operate on 82°C flow and 71°C return temperatures, meaning primary flow temperatures of up to 90°C are commonly used in district heating schemes to satisfy this requirement across a hydraulic break, such as a plate heat exchanger.

A detailed review of the existing systems concluded that these buildings can operate at 75°C flow and 60°C return, while new buildings have been designed to operate at 70°C and 45°C return. Weather compensation can reduce summertime temperatures for further efficiency benefits. 

The 2.65MW ammonia water source heat pumps at Queens Quay

The flow temperature has to be high enough to meet the needs of the four retrofit buildings but, as these constitute 10% of the demand, they don’t influence the overall network distribution temperature too much and we can still prioritise overall system efficiency.

If the balance of loads tended towards a higher retrofit percentage, then the reciprocal would be true. However, reduction in temperature via weather compensation is important to ensure the system can satisfy the domestic hot-water production, as well as any specialist needs, such as healthcare pasteurisation.

With this blend of new-build and retrofit, our designers achieved a coefficient of performance of 3.1, making it considerably more efficient than traditional solutions, such as gas-fired boilers or combined heat and power.

Building the data model

Initially, the development had the following anchor-load buildings: the Aurora Building, Clydebank College, Titan, a leisure centre and the Queens Quay Care Home. It will create new-build properties, such as 1,200 homes, but there is an opportunity to incorporate significant existing building stock going forward.

Predicting the energy demands of a development is difficult, but necessary because it dictates the sizing of the plant, equipment and district energy network. For new-build connections, understanding the heat demand based on building designs is relatively straightforward – by looking at U-values, for example – but occupants can use energy in a variety of ways, which affects their annual energy demand and profile.

Energy data for existing buildings is seldom available in the granularity required to build detailed energy profiles, so calculations often incorporate experience to find a solution with inherent flexibility that can deal with all possible scenarios.

Understanding peak loads to size energy-centre plant is something all district energy designers must consider. The real challenge, however, is understanding the diverse energy profiles across the network to select the most appropriate water source heat pump and thermal storage, to achieve a significant heat fraction.

This means accurately predicting the energy demands for all connected buildings, plus the diversity across the network. Without these, the water source heat pump could have been sized incorrectly: too large and it would not operate efficiently; too small and the carbon savings would not be achieved.

A flexible solution

Designing new buildings and properties to connect to a district energy system, which operates at lower temperatures, is relatively straightforward. Building Regulations have helped reduce the heat losses from buildings by improved U-values and lower infiltration rates – all of which means thermal comfort can be achieved with lower temperatures.

Existing buildings, particularly ageing ones, usually have higher heat losses and infiltration rates, so higher temperatures are required to achieve the same thermal comfort levels. 

Connecting these buildings to a network with lower operating temperatures can only be done after a full evaluation of space-heating emitters – such as radiators, fan coil units and air handling unit coils – to ensure heat losses are achieved.

While it wasn’t necessary on the Queens Quay project, improvements to building fabric, such as insulation and replacing single-glazed windows with double-glazed ones, can help with reducing heat losses and is often a sensible place to start.

Often, older LTHW systems have constant-volume pumps controlled via 3-port valves. This can lead to high return temperatures to the energy centre and to the system not performing as designed, or turning off. This, in turn, can result in increased network losses and higher contribution from gas-fired boilers.

Converting these 3-port systems to 2-port ones, employing pressure independent control valves, ensures good control and low return temperatures, although there will generally need to be a change in pump-control philosophy, from constant volume to variable volume, often requiring the introduction of inverters to all pumps.

Another consideration is domestic hot water. CIBSE/Association of Decentralised Energy Heat network code of practice (CP1) has recently reduced the temperature required within residential properties.

However, commercial and healthcare buildings have different temperature requirements and these influence the minimum network temperatures. This is particularly applicable to the summer operating condition, ie the minimum weather compensated temperature.

A heat pump-ready HIU

Many traditional heat interface units (HIUs) do not have the ability to operate efficiently at lower temperatures. While the Queens Quay development would have flow temperatures of up to 80°C, this would be a rarity, and in the warmer summer months – when there is little heating demand – it would be dropped as low as 60°C.

To deliver efficiency over these parameters, it was necessary to design a heat pump-ready HIU, with an intelligent core, that could monitor the changes in flow temperature and the domestic hot-water temperature, and compensate to ensure optimum performance.

The abstraction pumps drawing water from the river Clyde

Vital Energi spent two years developing the new technology to meet these requirements. While it was designed with the next-generation district heating systems in mind, it can perform efficiently at higher temperatures.

This, combined with its ability to react to temperature changes, means it will stay optimised as the flowrates change throughout the season, giving real-time optimisation to the project.

Ian Spencer, associate design director, says: ‘Reduced temperatures mean reduced losses – and, while losses created by an individual HIU are comparatively small, when you multiply this by 1,200 and operate them over a 20-year period, it can deliver significant savings in operating costs and carbon.’

Retrofit and new-build performance

A review of a building’s energy system is essential to understand the changes needed to make it compatible with a lower-temperature district energy system. This, combined with a survey of historical energy consumption, begins to paint a picture of what is necessary, but historical oversizing of heat emitters and antiquated controls systems can actually provide a benefit, as they reduce the need to change the secondary side heating system.

Improved standards and advances in technology mean buildings that are only years old can compare poorly in relation to current buildings. The Queens Quay development has buildings that are a few decades old, but because of their fabric construction and existing heating system design, we need to be able to deliver flow temperatures of 80°C and return temperatures of 60°C.

On the new buildings, where we can have an input on design, we can deliver 70°C flow and 45°C, resulting in lower temperatures and a higher temperature differential.

Retrofits require more consideration in the design process, but we believe Queens Quay demonstrates that heat pumps are viable for buildings of all ages. Lowering temperatures, while improving insulation, emitters and controls, can be an extremely efficient energy solution.

About the author
Lee Moran is design director, operations – North & Scotland at Vital Energi

The post A new era for heat: Queens Quay heat pump appeared first on CIBSE Journal.

• Specifying one HVAC solution or a separate cooling system
• System modelling and capital cost
• Energy efficiency
• Noise levels, user comfort and control
• Central plant space and maximising the footprint of a building
• Long-term costs
• Environmental impact and public perception.

As global temperatures continue to rise, comfort cooling is becoming increasingly popular in the UK, and this trend is evident in the growing demand for city-based apartments with effective cooling systems in place. These types of properties are commanding an additional premium on both the sales and rental markets, and so it makes sense to maximise this premium through specifying solutions that could add value to the development and maximise user comfort.

The variety of comfort cooling solutions available on the market now includes the innovative Zeroth Energy System. Designed in cooperation with leading UK developers, this solution helps to overcome the specific challenges of city based apartments.

Zeroth and the drivers of comfort cooling specification
The Zeroth Energy System by Glen Dimplex Heating and Ventilation (GDHV) is an ambient energy network of water-to-water heat pumps within each apartment connected to a central plant capable of delivering hot water, heating, and comfort cooling. The system was designed specifically to tackle the challenges around overheating and the resulting energy inefficiencies that are most visible in multi-occupancy buildings.

The growing challenge of overheating in buildings is amplified by increasing urbanisation. Properties in cities tend to suffer most from the effects of heat loss from traditional ‘high temperature’ heating systems being trapped by the highly thermally efficient building envelope. The result is overheating in corridors and communal spaces and eventually in apartments, requiring additional cooling or ventilation.

The tight confines of busy city streets can limit efforts to mitigate overheating through design. External factors such as noise or air pollution often restrict the use of windows and occupiers are naturally looking for comfort cooling measures when renting or purchasing properties to increase the air quality and their thermal comforts. Passive cooling may meet some of the cooling demand, but in many cases, it can’t reduce the internal temperature of a dwelling to comfortable levels alone.

Not addressing overheating in a building and the relevant comfort cooling requirements at the design stage may require either a complete cooling system retrofit or post-completion alterations to increase ventilation rates. Both can be costly and cause unwelcome disruption for the occupiers

Increasing the energy efficiency of an apartment

The central loop of the Zeroth Energy System is designed to run at 25°C, a significant reduction from the 80°C of a traditional high-temperature system, reducing heat loss by up to 90%. For more information on increasing the energy efficiency of your apartment building development, read our Harbour Lofts case study.

One HVAC solution or a separate cooling system
Considering the type of cooling and the overall HVAC system design is essential in the context of maximising short- and long-term financial benefits.

Successful integration of numerous separate solutions into one HVAC system may impact the overall cost and delivery time, especially if multiple suppliers and contractors are involved. This should be factored into the cost analysis.

Two-pipe systems, like the Zeroth Energy System, use the same infrastructure to deliver both heating and cooling. This means less pipework, less additional technology, fewer installers, and faster installation. The faster the project is finished, the quicker it can start returning initial investments.

System modelling and capital cost
The comfort cooling choice should support the design, function and energy strategy of a building. Detailed system modelling is a must for the accurate estimation of the cost for cooling units, the infrastructure, such as ductworks, pipes and so on, and the impact of the installation on the schedule of a project. Choosing a two-pipe solution could provide all HVAC services, and offer a relatively simpler system design and more accurate modelling.

Detailed and accurate system modelling and design are also crucial to ensure the system isn’t oversized and inefficient. Oversized systems could cause issues such as unnecessarily higher capital costs that may have an impact on the overall project cost, and they can suffer from inefficiencies – making them more expensive in the long run.

The accuracy of system design is key, as the capital cost is likely to form the largest expense of an HVAC system.

Energy efficiency
Energy efficiency is a regulatory requirement and an important commercial factor. The transition to a low carbon economy means fast-changing regulations that are likely to phase out inefficient HVAC systems and also gas-operated systems. Although perhaps cheaper to install and run today, these will require retrofit in the future. It is also important to consider that energy-efficient, low carbon technologies are growing in popularity, and inevitably in demand, as the public perception of climate change and our attitudes toward carbon emissions change.

How efficient is the Zeroth Energy System?

Installation of the Zeroth Energy System can greatly improve the energy strategy of a building. When used within SAP 2012, the Zeroth Energy System, in conjunction with an air source heat pump (ASHP), can offer efficiencies up to 300% and help reduce building carbon emissions significantly. You can read more on how the Zeroth Energy System helps complete the green living arrangement in London’s Church Road development.

Noise levels, user comfort and control
User comfort, availability of intelligent controls and low noise levels are major factors that impact occupant experience. Occupant satisfaction inevitably affects the value of dwellings, and the choice of HVAC system should reflect this.

Intelligent controls are becoming a common feature in modern households, with an emphasis on controls that integrate multiple functions such as heating, cooling and ventilation while offering wireless connection for convenience.

The Zeroth Energy System is available with a full variety of controls for user convenience and also for transparency and the control of energy expenditure.

The system has the flexibility to integrate with almost all other types of controls on the market and with building management systems (BMS). This offers freedom of specification and added value through better building level control and maintenance. It is worth exploring all control options of the chosen HVAC system from the outset, as these add value and help futureproof development.

Central plant space and maximising the usable space in a building
Specification of a cooling system may generally require an increase in the size of the plant and could command additional space for the cooling units, the infrastructure, or both. The Zeroth Energy System mitigates this issue by using the same pipes and plant, only requiring cooling emitters to provide comfort cooling.

The efficient system design of the Zeroth Energy System as an ambient network frees up both plant space and space in the building. Building footprints can be maximised with larger living areas or extra dwellings. This means larger project profit, especially in a city landscape where space is at a premium.

Long-term costs of comfort-cooling systems
Maintenance and servicing are costs that will impact a system’s lifetime cost, efficiency, and user satisfaction; criteria that make both sales and rental properties attractive to buyers and occupiers.

Single HVAC systems are generally simpler to maintain and have a longer life span, and intelligent building management systems can expedite servicing and streamline maintenance.

As a result, the overall service and maintenance costs are reduced, and end-user experience can be drastically improved.

As with any purchase, it is important to query the product and, if possible, see it installed in similar settings. The Zeroth Energy System has been installed and can be seen working on a functional rig that replicates residential settings with a variety of rooms and emitters.

The Zeroth Energy System comes with two-year warranty and maintenance, and there are options that extend this to five years. Warranty and maintenance options need to be considered when setting out the long-term costs, especially in build-to-rent settings.

Environmental impact and public perception
Although efforts are being made to electrify the grid and introduce legislation to help achieve net-zero carbon buildings by 2050, it is vital that the cooling technology specified is Part L-compliant. The commercial reality is that many air conditioning technologies will create additional building energy loads that may translate into additional costs and an increase in carbon emissions.

In comparison, cooling is a reverse cycle of all heat pump technology. This means cooling using the low carbon technology of heat pumps can be provided efficiently and through the same infrastructure as heating.

The significant shift in public perception of climate change and carbon emissions, especially in the past year, is likely to mean that properties designed around efficient low carbon technology and use of renewables will simply be the preferred choice for many occupants.

GDHV can advise with various aspects of specification, design and technical support. If you would like to find out more about the Zeroth Energy System or discuss how it can be implemented in your next project, please contact our team of experts. Our case studies offer more information on projects which have incorporated the Zeroth Energy System.

The post What are the considerations for comfort cooling in city-based apartments? appeared first on CIBSE Journal.

In 2017, with the industry set for rapid growth, the Competition and Markets Authority (CMA)recommended that the gas and electricity regulator, Ofgem, be given powers to regulate domestic heat networks. In February this year, BEIS launched a consultation for a regulatory framework that would give Ofgem oversight and enforcement powers across quality of service and pricing for domestic heat network consumers.

The consultation, Heat networks: building a market framework, proposes mandatory regulation of new heat networks and urges developers to join the Heat Trust, an independent consumer-protection scheme for heat network customers. The trust aims to ensure a minimum standard of quality and a level of protection for consumers equal to other energy customers. Scheme rules include a guaranteed performance standard for temperature, continuity of service and reporting faults. Heat interface units (HIUs) must also be maintained regularly, and suppliers signed up to the Heat Trust can be penalised if standards are not met.

‘Heat networks are maturing and becoming a central feature for the decarbonisation of heat’ says Gareth Jones, managing director at heat network specialist FairHeat. ‘This is apparent in increasing consumer protection, better technical standards – through the ADE-CIBSE Heat Networks Code of Practice – and proposed certification.’

Jones believes it is a pivotal moment for heat networks, because of the move away from gas-fired CHP energy source towards heat pumps, which has huge implications for the design of heat networks. ‘There needs to be a significant change in the way people design dwellings and systems. We need lower temperatures, which will increase the performance for heat pumps and increase the number of heat pumps that can be used,’ he says.

Regulating heat networks

The BEIS consultation looked at options for ensuring heat networks are designed, installed and operated to robust technical standards, and concluded that there should be some form of mandatory assurance schemes. ‘We know that, as the market builds, some heat networks have struggled to keep up standards in line with the rest of the sector, leading to less effective and poorer performing networks,’ says the report. ‘It is important to address this gap, both to improve the experience of consumers on poorer performing networks and to address the negative impact on the sector’s overarching reputation.’

The consultation states that assurance schemes would assess whether new heat networks had met technical standards required at design and build. It would consider whether large extensions to existing networks could be covered by the assurance scheme and whether operational requirements should be applied to existing sites.

A body such as the UK’s National Accreditation Body could have responsibility for monitoring organisations offering assurance and certification, says the CMA report, which advises organisations to join the Heat Trust to prepare themselves for future standards. 

Lowering temperatures

With the decarbonisation of electricity, heat networks are being designed with heat pumps as the energy source, rather than gas-fired CHP. For heat pumps to be truly effective, says Jones, the flow and return temperatures should be lower than for a traditional CHP district network.

Heat pumps are affected by changes in temperatures, both in terms of the efficiency of the refrigeration cycle and the system complexity required to reach high temperatures from cold sources. ‘The coefficient of performance of heat pumps drops quite dramatically at higher temperatures; 5K can make a really big difference,’ says Jones. A review of three heat pump manufacturers, for example, showed an increase in seasonal coefficient of performance of 13%-21% when generating and distributing at 60°C as opposed to 65°C.

These Telford Homes apartments near London Docklands had acceptance testing

Where heating systems serve DHW and space heating, it will be the DHW supply temperature that defines system temperatures, as the space heating can be a lower temperature. So, a 5K reduction in DHW allows a 5K reduction in generation and distribution temperatures.

One barrier to lower temperatures has recently been overcome after the HSE clarified that HIUs with instantaneous hot water generation are deemed a low legionella risk. Heating systems with hot-water storage have typically had to maintain water at a high enough temperature to prevent the growth of legionella bacteria. However, this is not necessary for low-volume systems where, for example, hot water is supplied instantaneously through a heat exchanger. The HSE says that, under HSG274, Part 2, HIUs should be able to achieve a peak temperature of 50°C to 60°C.

Jones says that network temperatures should be 55°C at the HIU, with 50°C from the HIU to the tap. Many designers have used a 55°C minimum to the tap. This requires a minimum 60°C network temperature.

Faster hot water

The new version of CP1: Heat Networks: Code of Practice for the UK will include far more performance metrics and introduces the concept of acceptance testing. Acceptance testing allows validation of whether heat networks meet specified performance requirements and, as such, is well aligned with the move toward technical certification, as proposed by BEIS. Effectively, acceptance testing will be one of the core mechanisms for any future heat network assurance scheme, says Jones.

‘Our experience is that acceptance testing has a significant positive impact on network performance, with many networks performing better than design because of rigorous commissioning’ he adds.

Telford Homes is using acceptance testing to check its heat networks before handover (see ‘Site test’, CIBSE Journal, August 2018), and now also uses FairHeat to test the design, installation and commissioning. (See panel, ‘Testing every home’.)

Jones says the experience of acceptance testing out in the field will form the basis of an assurance scheme that aims to make sure developers build low carbon heat networks that offer comfort for consumers without the expense.

The post Quality assured: regulating the heat network industry appeared first on CIBSE Journal.

A study carried out into heat network water quality in the UK gave examples of current system issues and offered guidance on avoiding high-cost failures within systems’ lifetimes. It considered design stage, pre-commission stage and ongoing management, and 185 systems were studied, with particular interest given to failures and the root cause of these.

The study found that improvements could be made to water-treatment design and implementation throughout the process: design, build, pre-commission, handover and ongoing maintenance. Improving water treatment at these stages will lead to systems running more efficiently, minimise downtime, avoid non-budgeted capital expenditure, minimise disruption for end users and extend the life of the system.

The 185 systems across the UK had their water quality monitored for bacterial contamination and chemical composition of the system waters for 24 months. System volumes varied between 10,000 litres and 1,800,000 litres.

Issues occurring within 185 systems monitored for the UK heat network water-quality study

Key findings

Design and pre-commission

• Inadequate pre-commission cleaning of horizontal pipe runs/laterals before the terminal units and not in accordance with agreed specifications
• CHP and biomass not being used/left stagnant
• Lack of good practice for storage of district heating pipework, especially when laying in trenches (for example, pipework not suitably capped), allowing ingress of debris to the system during build stage
• Systems handed over with inadequate certification and reporting
• A lack of independent audit process at handover
• Metallurgy of system not considered for water treatment
• System size not considered for water treatment
• Lack of continuity in water treatment for staggered build networks
• Inadequate flushing velocities achieved in >150mm bore pipework
• Lack of automatic water-treatment dosing systems on networks
• Lack of side-stream filtration on networks
• Lack of remote water-quality monitoring on networks.

On-going management

• System leaks leading to ingress of oxygen and dissolved solid precipitation from the mains water supply feed
• Incorrect water-treatment choices for metallurgy of system
• Lack of monitoring and maintenance of filtration equipment
• Lack of monitoring and maintenance for water treatment after practical completion
• Bacterial proliferation in stagnant areas
• Over dosing/under dosing of chemistry
• Lack of live monitoring systems to flag up issues.

Conclusions

Currently, there are gaps in the design, operation and guidance for water-treatment in the UK district energy sector. The following should be borne in mind:

Considerations at design stage

• Minimise areas of potential stagnation
• Specify suitable side-stream filtration for all district energy systems
• Specify that fill water is deaerated
• Specify that district heating systems have continuous monitoring for pH and conductivity as a minimum. The system should also be able to report remotely – either via the BMS, or email/SMS – to indicate failure of the control levels to suitable stakeholders
• Water treatment should be specified to be ‘automatic’ in nature
• Water treatment, fill water quality and method and pressurisation should be considered at design stage, based on system volumes and metallurgy. If secondary and tertiary systems are to be filled from the ‘primary’ network, consideration must be given to ensuring no conflicts between the water-treatment regimes of both systems.

Consideration for pre-commission stage

• For pipework >150mm diameter, alternate flushing methodology to BSRIA BG29:2012 should be sought – for example, ice pigging and traditional pigging
• Improve record-keeping and audit processes during precommissioning works and implement a daily log of works on site
• Have an independent audit of the works before handover
• Consider existing water treatment when connecting new systems to ‘old’ networks.

Sludge and biofilm removal from a district heating system

Ongoing considerations

• Stagnation should be avoided – any stagnant areas should have full velocity and heat flushed through for a minimum of two minutes every four days
• ‘Legacy’ equipment no longer in use should be decommissioned and disconnected from the system waters, leaving no ‘dead-legs’
• Side-stream filtration should be monitored and managed on a pro-active basis, to ensure suspended solids are removed as required
• Continuous monitoring and automatic dosing should be installed on all district heating networks to minimise the risk of corrosion and associated water treatment issues.

Improved water-quality treatment in UK heating networks will prevent non-budgeted capital expenditure, minimise disruption for end users and extend the life of the system.

Jon Greaves is national technical manager at Hydro-X Water Treatment

The post The scale of the problem – water quality issues in heat networks appeared first on CIBSE Journal.

‘Dog biscuits are cheap, they float, and if you measure the time it takes a floating biscuit to travel 10 metres – and divide that by 10 – you’ll get the river’s flow velocity in metres per second,’ he says. Knowing the river’s velocity and cross-section is fundamental to calculating how much heat is available to be captured by a water source heat pump, which is Pearson’s interest.

It is this knowledge, acquired from his geography class, that has led Pearson to the conclusion that large heat pump installations could fundamentally change the way heat is generated in the UK – and, critically, help to decarbonise the existing energy-inefficient building stock in cities.

‘Our cities are typically located on larger rivers, where gravity drains the upper reaches, delivering solar thermal energy right to where we need it most,’ he says. ‘We won’t win the decarbonisation battle with new houses. It’s the old stuff that is the challenge, and it’s too tricky to decarbonise many of these buildings on an individual basis. So the best way is to take a district heating system into the centre of a city and use that to supply buildings with low carbon heat.’

For Pearson, the obvious source of low carbon heat for cities are their rivers. ‘By our rough calculation, for example, there is about eight times as much heat in the river Clyde as you would need to heat Glasgow’s entire city centre.’

Pearson has worked at Star Refrigeration for 20 years. The business was started by his father and two colleagues in Glasgow, in 1970, to specialise in commercial and industrial refrigeration, and it is still based in the city. His father, who is nearly 88, is also still involved, but Pearson’s older brother Andy [not the author of this article] is now group managing director. Although the business is privately owned, there are more than 300 shareholders, mainly past and present staff and their families.

Independence and long-term thinking are of paramount importance, says Pearson, who graduated from university with a degree in engineering with business management and European studies. He worked for another Glasgow-based engineering business, Howden, before being asked to join Star to help design refrigeration systems for ice rinks and cold-storage projects. After a four-year spell at a spiral and tunnel freezer acquisition, Starfrost, in Lowestoft, he returned to Star’s Glasgow headquarters to work on ‘where next?’.

‘The UK is a solid market, but not growing,’ Pearson says. ‘Sustainable heating caught our eye, and high-temperature heat pumps draw the same skills as industrial refrigeration, so was an obvious match.’

One of the big schemes he subsequently worked on was proof of this – a £25m upgrade of the district heating system in Drammen, Norway. This innovative project uses a water source heat pump to take low-grade heat from the adjacent fjord and turn it into high-grade heat to supply heating for the 60,000-strong community. As well as air quality, the key driver was to move from biomass and gas.

The fact that Star’s heat pump solution uses only three systems of 780kg of ammonia as the refrigerant was one of the reasons the company was awarded the contract, says Pearson. ‘We won the job ahead of a company that had promoted a solution using up to 7,000kg of R134a, an HCFC with a global warming potential (GWP) 1,430 times that of carbon dioxide.’

He adds that it is not unreasonable to expect a large refrigerant system, such as the one at Drammen, to leak about 1% a year: ‘70kg of R134a at a GWP of 1,430 is a big number – equivalent in GWP to driving 800,000km a year. Whereas, by using ammonia, our GWP is the fat end of nothing. Ammonia is also about 25% more efficient, so consumes far less electricity, the primary operational cost.’ 

It is not the ammonia refrigerant that makes the Drammen district heating system unique. ‘As far as I’m aware, it is still the only large-scale 90°C district heat pump in the world,’ says Pearson. He admits there were some elements of the Drammen installation that were ‘a wee bit sticky’, but he points out that ‘innovating is not without its challenges’ and says Star ‘stuck with it and got it right’.

The ammonia-based heat pumps are now delivering 85% of Drammen’s near-70GWh of heat each year. Gas is only for top-up on the coldest days.

At about the same time as the Drammen heat pump was coming on line, the UK government was talking about the need to decarbonise heat as a consequence of the EU’s renewable energy sources directive. Star saw an opportunity to use its experience of Drammen to grow its business. ‘We’d decided that a big part of the business going forward would be in heating as well as cooling,’ says Pearson.

However, biomass and gas combined heat and power (CHP) – as well as a reluctance to change – left Star frustrated at the slow uptake. So, in 2013, it set up Star Renewable Energy, a new division to focus specifically on big heat pump projects for district heating systems.

‘We understand heat exchangers and compressors and thermodynamics; if there is going to be a trend for heat pumps, then we should be part of that,’ Pearson says. ‘I now lead that business unit, which is able to draw on all the refrigeration skills we already have at Star, but for a totally different application.’

Wooden building adjacent to Hillpark high-rise blocks housing Star’s air source heat pump

Pearson is passionate – fanatical even – about the potential for heat pumps to replace burning fossil fuels, such as natural gas, to provide heat. ‘Heating is about 50% of the energy consumed in the UK, so we have this challenge of how to do heating without burning gas and biomass – and that’s where large heat pump solutions come into their own,’ he says.

‘Although not originally a strategic driver, we have observed the growing emphasis on air quality. Drammen still shows us a fantastic outcome in this regard, with 85% lower nitrogen oxide (NO_x) emissions, the gases now attributed to lung, heart and brain disorders, but largely invisible. Although largely attributed to transport in cities, some studies have suggested 40% is actually from gas boilers and other gas devices, such as CHP.’

Pearson adds: ‘The problem with replacing gas boilers with heat pumps on a piecemeal basis is that gas heating systems are, generally, designed to operate at 82°C flow, 71°C return temperature. ‘If you want to replace that system with a heat pump, you cannot turn up with a domestic unit that only provides heat at 45°C,’ he says.

Star has three systems nearing completion in 2019. The Clydebank river-source scheme will provide heat at 80°C, the Hillpark air source heat pump scheme at 62°C, while the ground source heat pump serving the renovated old Post Office at Islington Square provides heat at 65°C. ‘The residents won’t be aware of the heat pumps, but they will enjoy cleaner local air with less gas being burnt.’

Twin water source heat pumps to be installed at Queens Quay

Does he see a time when cities will have both district heating and cooling? ‘If you want district cooling and heating systems, you could have four-pipes going into the buildings or a two-pipe ambient loop system and a heat pump in each building,’ he says.

‘A heat pump in each building would be tricky if aiming for close to 80°C and, if you’ve got dozens of buildings on a network, they will each require a heat pump sized for their individual max demand – whereas, if you’ve got district heating and separate cooling systems, the central heat pump will be sized for the aggregate demand, which could be 50-60% smaller. And, because they are centralised, they’ll be easy to turn off very quickly if the grid gets stressed – a very valuable technique, far preferable to running auxiliary diesel peaking plant.

‘We can also force-run and store heat, which is far more sensible than curtailment of wind farms, and turns the surplus electricity into three or more units of heat.’

Pearson has taken his fixation with heat pumps home. ‘As part of renovations to my house, I’ll probably deploy a ground source heat pump – but it’s a monstrous amount of money when a gas boiler would work fine,’ he says. ‘But gas will eventually fade and any provision of hydrogen is predicted to be three or more times the cost of gas currently.’

The late Professor Sir David MacKay, the government’s chief scientific officer, was a huge influence on Pearson’s thinking, encouraging critical thought of populist ideas in his book Sustainability without hot air.

‘He’d question where hydrogen was going to come from, how much it would cost, whether it would require additional methane imports, and how dependent it would be on as yet unproven at-scale solutions, such as carbon capture,’ says Pearson.

‘If I’ve heard anything from the upsurge in thinking from [Swedish schoolgirl] Greta Thunberg – who initiated the school “strike for climate change” movement in November 2018 – it is “act faster”, and that, to me, means deploy what we know works: don’t dream of unicorns.

‘I hope they start encouraging a move forward from what we know is the major component of the problem – “burning gas” for the rather simplistic need of heat.’

The post In the hot seat: Interview with Dave Pearson appeared first on CIBSE Journal.