Integrating district heating with renewable energy sources

District heating is centred on the concept of a site utilising one large heat source running very efficiently, rather than each building having separate smaller ones running less efficiently; the idea being to reduce overall CO2 emissions and save on running costs. The concept is very popular in geographical areas located off the mains gas grid and therefore making a large renewable heat source a great option. Whilst, many urban re-generation schemes are also considering district heating as a cost-effective, efficient solution. This article explores the various options for renewable heat sources and explains how they can be integrated into a district heating system. In addition to the obvious environmental benefits, using renewable sources can be great opportunity for property owners to receive Renewable Heat Incentive (RHI) payments. The scheme encourages the use of green renewable energy systems, by paying yearly incentives.

Ground source heat pumps

Ground source heat pumps operate on the basis that the ground just beneath the surface remains at a constant temperature throughout the year, which allows it to act as a heat source. A mixture of water and anti-freeze is circulated around a loop of pipe, with natural heat from the ground being absorbed into the liquid. The heated fluid then passes through a compressor that raises it to a higher temperature, which can then be used as a heat source for supplying heating water and potable hot water.

Air and water heat pumps

Air/water heat pumps are based on the fact that heat from the ambient air can be collected and boosted to a higher temperature to provide heating throughout the year (heat pumps even operate effectively in below freezing conditions). They work using a similar principle to a refrigerator except extracting heat from the outside air (whereas a fridge extracts heat from its inside). We can supply the leading German branded units made by Waterkotte.

Biogas and biomass

Biogas typically refers to a gas produced by the biological breakdown of organic materials such as manure, sewage, municipal waste and energy crops. The methane produced can be burnt as a fuel providing energy. Biomass refers to biological material that can be used as fuel, most commonly plant matter grown specially for use as biofuels, but may also include biodegradable wastes that can be burnt as fuel in an Anaerobic digester system.

Wood Chip / Pellet boilers

Burning wood fuel instead of fossil fuels is much better for the environment in terms of CO2 emissions. Wood pellets are usually compressed sawdust or wood shavings and are uniform in shape and composition. They are easy to ignite, create little ash and will flow freely through feeding mechanisms such as hoppers and augers. At Mibec we offer a range of biomass boilers from Hargassner, one of the leading European boiler manufacturers.

Integrating with District Heating

The chosen heat source can then be combined with one of our buffer tanks in a central plant room. The buffer tank retains heat for later use with the flexibility of immediate access without the heat source needing to get up to temperature; this can be very useful for maintaining a more constant output.

The central heat source will then be connected to the various buildings in the scheme via an underground pre-insulated pipe network designed to maintain the water temperature when in transit (avoiding heat losses to improve energy efficiency). We offer a wide range of pre-insulated pipes from leading pipe manufacturers like Rehau, or our own Mibec DHP pipe. Pipe options are available for both heating water and potable hot water and we have just launched Microflex Quadro which can fulfil both applications in a single pipe thanks to its 4-core design which can reduce trench requirements.

All of the above is then easily linked via Heat Interface Units (HIU’s), which enable the heat created to be distributed and metered. Sometimes referred to as Thermal Interface units, HIU’s provide a clean and easy option for distributing the energy created by a district heating system.
We offer a full free of charge specification service covering the whole of the UK, designed to support architects, specifiers or contractors, helping you to select a heating solution to fully meet your needs. Please feel free to email or call our support department on 01948 661639 where one of our highly trained advisers will be happy to help you.