District heating
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Pipework possibilities
Alexandra Leedham, technical leader – Renewable Energy at REHAU, explores the importance of pipework choice when it comes to district heating schemes
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upplying heating and hot water through a network of pre-insulated pipework from a centralised heat source, district heating eliminates individual boilers in commercial and residential buildings. Consequently, it has become a popular choice for contractors and developers as installation and maintenance of the energy centre is reduced to one location, reducing costs and construction time.
For projects looking to follow sustainability trends, particularly in the aftermath of the Government’s Ten Point Plan for a Green Industrial Revolution in November, and the publication of its December Energy Whitepaper, district heating can also offer emissions benefits. Pressure to deliver buildings with smaller carbon footprints, as well as efficient heating systems delivering reduced bills mean district heating could be a key solution for developers and contractors.
Government backed
Following the Government’s Ten Point Plan, the BEIS Energy Whitepaper and the Committee on Climate Change’s (CCC) Sixth Carbon Budget, it is clear decarbonisation of the nation’s buildings is a top priority. As pressure mounts on building professionals to deliver the targets set out in these plans, government initiatives will play a vital role in implementing low-carbon alternatives. Funding initiatives such as the Green Heat Networks Scheme (GHNS) will help in this transition, and favour residential and commercial district heating applications. Launching in 2022, GHNS will replace the existing Heat Networks Investment Project, and will similarly award grants to projects implementing sustainable, low- carbon district heating systems.
Shifting standards and regulations are also creating an environment more amenable to district heating systems using heat pumps. The proposed tenth Standard Assessment Procedure (SAP 10.1), part of the Building Regulations Approved Document
L consultation in 2019, sets standards for a new lower emissions factor for electricity, advocating heat pumps as a more sustainable solution. Compared to the SAP 2012 metric of 0.519 kgCO2/kWH, SAP 10.1 proposes a value of 0.136 kgCO2/kWH – a 75% improvement in heat pump derived electricity carbon savings from previous figures.
Making heat networks renewable
As green legislation and funding drives decarbonisation efforts, alternatives to traditional fossil fuel boilers in homes and commercial properties must be renewably powered. Most heat networks across the UK and Europe are classed as third-generation, with water circulating at 70-95ºC and often heated by a fossil fuel powered boiler. However, more fourth-generation systems with a comparatively lower 50-60ºC flow temperature are being implemented, as the reduced heat loss they can offer across the network makes them more efficient and cost-effective.
Fourth-generation systems also reap the same benefits as their predecessors because of their similarly centralised design. On top of this, they also get the same benefit of easier, more cost-effective installation and maintenance due to eliminating individual boilers. The lower flow temperatures of fourth-generation systems suit centralised heat pumps and waste heat sources, allowing for lower emissions in line with net zero goals and helping contractors and developers deliver sustainable projects. Heat sources can be changed or added over time on district heating schemes, increasing flexibility for network operators and allowing retrofitting of low-carbon alternatives.
Material choice matters
As renewable heat networks grow in popularity, pipework material choice is becoming an important part of ensuring the solution delivers heating and hot water efficiently. While steel has traditionally been the
material of choice for district heating schemes, all- polymer heat networks are growing in prominence due to the material suiting lower circulation temperature, lower heat losses and simpler installation. With reinforced polypropylene (PP-R) used as the network’s main spine, polymer-based schemes are now able to provide heat loads up to 16MW. Flexible PE-Xa pre-insulated pipework in coils can then be easily connected to this main spine, ensuring more cost-effective installation for contractors, specifiers and developers as they extend networks. This with the material’s expected 50-plus year lifespan, polymer systems are being considered a sustainable means of futureproofing a building’s heating and hot water requirements.
A PP-R pipe main spine can also help to deliver reduced pressure losses of up to 19 per cent when compared to a steel solution. For contractors and developers concerned with maintenance, minimised corrosion risks also negates risks of system failure and expensive repairs thereafter. PP-R is up to 37 per cent lighter than steel so is more easily handled onsite, lowering emissions incurred during transportation. This sustainability is improved further by PP-R being 100 per cent recyclable. While pressure on building professionals to decarbonise their operations and select low-carbon solutions grows, considerations around reducing both materials used and installation times remain front of mind. By eliminating expansion bends present in steel networks, polymer pipework reduces installation time, while using less materials and fewer joints. PP-R pipe’s lighter weight and the PE-Xa pipe’s flexibility also allows contractors a quicker and more flexible installation. The decarbonisation trend for heating and hot water solutions, combined with traditional challenges around quicker, more cost-effective installations without compromising quality, brings about challenges for all building professionals. Polymer district heating systems could be the easy-to-install, low-cost solution for these amenities.
www.heatingandventilating.net
24 February 2021
www.heatingandventilating.net
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