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The use of heat networks is increasing in the UK, and many of them incorporate CHP technology. Paul Wilson, National Sales Manager for CHP at Remeha, discusses how the technology works and the role it plays in heat networks to deliver carbon and cost savings.
In heat networks, heat is supplied to individual properties from centralised plant and is delivered through a single pipework distribution arrangement. Heat interface units (HIUs) will generally be used to provide the heating, or heating with domestic hot water, to individual properties. Each HIU controls its own supply with either a room thermostat, a separate programmer or individual TRVs. HIUs also record the heat consumed for accurate energy billing.
Recognising the benefits offered by heat networks, the Government set up the Heat Networks Investment Project (HNIP) capital investment programme to provide £320m of financial support for up to 200 projects by 2021. The pilot phase of the scheme awarded £24.21m to local authorities and public sector bodies, whose projects ran from October 2016 to March of this year.
This reflects a growing trend in using heat networks for multi-occupancy high rise buildings. In these developments, centralised schemes can offer significant benefits over the more traditional solution of installing separate heating systems in each individual property. These schemes can give the landlord greater control and purchasing power over the energy supplier and, if used with CHP, can help produce much cheaper electricity for the tenants.
Using centralised plant reduces the issues associated with supplying gas to multi-dwelling, high rise buildings. It decreases the risks linked to gas distribution pipework and eliminates the need to fit numerous flue terminals and plume displacement and condensate drainage systems, hence reducing capital installation and whole life costs.
If the dwellings are to be rented rather than sold, centralised plant can reduce servicing and maintenance costs for tenants. It also removes the need for legally required landlord gas appliance checks to be carried out in each individual property (providing there are no other gas appliances in the dwellings).
With centralised plant, a number of different fuel sources can be used. If low carbon technologies such as CHP are adopted, as is the case for six out of the nine pilot projects which received funding from HNIP, energy costs and carbon emissions can be reduced even further.
CHP units generate electricity while also capturing usable heat produced during the process. CHP is approximately 30% more efficient than on traditional heating plant and electricity supplied solely from the grid, and costs three or four times less.
When specifying CHP for a heat network, a key thing to remember is that while there is no minimum operational period per annum, savings will only be achieved if the CHP unit is running. Therefore, there must be a reliable, genuine need for the heat and electricity being produced.
The key to ensuring CHP delivers savings is to keep it as small as possible. Unfortunately, in too many cases, specifiers are given poor advice, and the ‘10% for luck’ rule is applied, meaning that many buildings have larger plant than required. If the heat demand is not present, oversized CHP will not run, and the anticipated electricity will not be generated.
CHP units complement existing boilers and/or water heaters, so in a properly designed and commissioned system, the heating and hot water equipment within the building will draw on the CHP first, before demanding additional supply from the boilers. This ensures that the building gets maximum output from the CHP.
For a CHP installation to be successful, all parties must work together at the initial stages of a project. The CHP supplier should be involved in every part of the design and installation process. What’s more, ongoing monitoring is crucial to ensure the CHP is used correctly and delivers maximum efficiency savings.
CHP engines are main-tained on a running hours basis. If the CHP unit is monitored remotely, it will inform the end user and the service team before a service is due. Remeha offers a range of maintenance and monitoring solutions.
With schemes such as HNIP paving the way for more support and investment, heat networks could have a major role to play as part of the country’s long-term strategy to cut carbon emissions. By incorporating CHP into a centralised plant scheme, these systems can become even more energy efficient to reduce fuel bills and help achieve a low-carbon future for the UK.