District heating
By luck or by design
T
he number of district heating schemes in the UK is set to grow exponentially in the coming years as a direct result of new funding initiatives. The Department for Business, Energy and Industrial Strategy (BEIS) launched a £39 million Heat Networks Investment Project in 2016, awarding £24 million for nine district heat network infrastructure projects in April this year, while public funding is predicted to generate up to £2bn in new heat network infrastructure investments across the country. It is projected that heat networks could deliver up to 18 per cent of UK heating demand by 2030, according to the Committee on Climate Change. In response to the growth in the technology’s usage here in the UK, a host of
organisations have outlined a series of guidance documents and best practices for heat networks, some of which lack the technical detail needed for effective application. In part this is due to the nature of district heating systems, for which there cannot be a one size fits all approach. Understanding how each of the parameters impact the design and implementation of a heat network system, as well as the shortfalls of some current practices is crucial. By taking into account a series of key considerations from the outset, consultants and contractors can ensure their heat networks deliver to expected levels of output and performance.
Putting end-users first
For all district heating systems, it is essential that the needs of end-users are considered from the outset. Establishing a consistent and accurate approach to billing and convenient pre-payment options is of the utmost importance if a district heating system is to operate effectively and help reduce the risk of fuel poverty. With district heating systems creating a natural monopoly by their very nature, it is also essential that opt out functions are in place. Pre-payment systems which display energy use and remaining credit ultimately ensure final customers can benefit from greater transparency. It is
When it comes to designing and installing heat networks, a fluid approach is needed where the design is continually reviewed and refined
www.heatingandventilating.net
Pete Mills, commercial technical operations manager at Bosch Commercial and Industrial
With no two heat networks ever the same, well-planned design and installation are crucial to ensuring a system performs to its potential. Pete Mills, commercial technical operations manager at Bosch Commercial and Industrial, explains the top considerations for consultants embarking on a district heating project
also important from the outset of the design to ensure that residents’ energy will be priced at least in parallel and ideally lower than other utilities. This is where the benefits of renewable energy, waste and low carbon heat sources come in to play. Low carbon energy and renewable heat sources are the only way of ensuring that customers can benefit from reduced fuel bills, but this is too often overlooked. Poor decisions at the early stages of design, which are purely focused on compliance with energy targets, can leave end-users compromised with the high energy costs we have seen reported at some poorly-performing schemes. To this end, the Heat Network Metering and Billing Regulations came into force
in 2014. Applicable to all heat networks with two or more final customer, who purchase heat, the regulations require heat suppliers to install meters for each final customers as well as building level meters. All heat networks must register with the National Measurement and Regulation Office and provide updated notification every four years. The intention is to provide as much transparency as possible for end-users.
Specification
Specifications for district heating systems can often lack the detail needed for effective implementation. This is a particular problem where clients are not sure what they want from a heat network. Collaboration between manufacturers, contractors and designers can help to tap into collective experience and avoid common pitfalls. At Bosch we have considerable experience in the development of heat networks, and particularly in combining them with renewable technologies using standard hydraulic and control arrangements, which can be adapted to specific use cases. Working closely with partners early on, it has been possible to develop solutions that ensure the best return in terms of reduced costs and lower CO2 emissions.
Energy systems and pipes
Reviewing the system design criteria is essential for any district heating project as it is integral that the system is able to deliver the required comfort levels without over-specification. The CIBSE-endorsed Danish DS 439 standard can be used to calculate flow rates for domestic hot water diversification. Working with manufacturers to obtain project-specific data for use in calculations, rather than general data from data sheets, ensures the most effective system design, refined to ensure the minimum pipe sizes are used. It’s essential that the system can adapt to usage from the dead of night to peak bathroom use in the morning, so another key consideration is the development of a strategy for differential pressure control.
Setting the temperature
It has been common practice to store domestic hot water (DHW) at 60˚C, yet the Approved Code of Practice (ACOP) L8 hot water guidance, suggests that for instantaneous water heaters, for example district heating systems using Heat
16 February 2018
www.heatingandventilating.net
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