HNDU

Heat Networks Delivery Unit

The Heat Networks Delivery Unit was set up by the Government in 2013 to provide grant funding and guidance to local authorities in England and Wales for heat network project development.

BEIS believes that local authorities have a key role to play in making heat networks succeed and that their involvement, particularly in the development stages, can help realise the benefits of heat networks, while also delivering jobs and growth.

The Heat Networks Delivery Unit (HNDU) was set up to address the challenges which local authorities identified as barriers to heat network deployment. Since 2013, the HNDU has run six funding rounds and awarded £14m to support studies into 200 projects across 139 local authorities.

The Government has been keen to encourage the use of CHP and district energy for many years and lamented the fact that only 2% of UK buildings benefited from district heating in 2001. Despite persistent encouragement the number of buildings in the UK heated by district heating is still only 2%. The Government allocated £320m in 2016 for consultancy fees and grants to increase the use of district heating in its Heat Networks Investment Project.

Disadvantages of District Heating based on CHP

However, there are strong reasons why CHP based district heating has not taken off in the UK and there will continue to be formidable barriers:

• the establishment of a CHP based district heating system requires substantial up front capital investment
  • it requires space for the CHP "energy centre" engine
  • it requires large diameter heavily insulated metal piping for the hot water network
  • it suffers heat losses to the ground
  • set up costs to administer and run the central "energy centre" over the whole life of the system
  • set up costs to run an accounting system to charge tenants and collect substantial fees each quarter
• the risk that potential clients may not want to sign long term heat supply contracts
• the risk that if some clients fail to meet their obligations over 25 years, others may need to contribute more
• many modern buildings need cooling as well as heating
• the heat generated in summer may go to waste
• it is not practical to flex the scale of heat supply to meet changes in demand, or expansion of the network
• most organisations want to be in control of their own costs
• combustion within cities is a major cause of air pollution and premature deaths.

Luckily there is an alternative form of district heating which neatly resolves all the limitations of CHP based district heat networks.

Alternative to CHP-based District Heating

There is an alternative means of providing district heating using a lower temperature distribution circuit: a heat sharing network linked to a communal ground array can be accessed by each building on the network. Each building uses its own heat pump to raise the temperature to the temperature it requires for its own heating and hot water requirements (or rejects heat to the network if it needs cooling).

A heat sharing circuit is much cheaper to install than a high temperature circuit because it does not require insulation to prevent heat losses to the ground. In fact, heat exchange with the ground that the pipes pass through can be beneficial: the ground adjacent to the pipes extends the contact with the ground and the pipes can draw heat from the ground.

Buildings with excess heat can reject heat to the Heat Sharing Network. This heat exchange with cold water is much more efficient than rejecting heat to hot air. It also raises the temperature of the Heat Sharing Network for the benefit of those whose heat pumps need to extract heat.

Heat Sharing based on a Heat Sharing Network can ...

• provide a reliable and low-cost green energy source for space heating and cooling
• save over 60% on carbon emissions on heating compared to emissions from gas boilers
• save over 80% on carbon emissions on cooling buildings compared to emissions (from the power stations) that power electric air conditioning and electric chillers
• provide a low-cost heat energy (or cooling) source for industrial processes
• recover low grade heat from any local source to increase the efficiency of heat pumps on the network
• provide opportunities for reducing carbon emissions by re-cycling solar energy instead of burning fossil fuels
• provide the opportunity to recover heat from buildings with high occupancy and high passive heat gains and transfer it to buildings needing heat
• attract Renewable Heat Incentive for use of ground source heat pumps
• attract Renewable Heat Incentive for use of solar thermal collectors
• improve urban air quality by avoiding combustion of fossil fuels or biomass in densely populated areas.

Groups of Buildings

A Heat Sharing Network is very well suited to providing heating and cooling to groups of buildings, particularly buildings under common ownership, including on hospital or university campuses. The cost of providing an efficient installation can be shared across a number of buildings, and the benefits increase if the district heating system includes other buildings such as schools or offices whose heating and cooling requirements may follow a different daily pattern (and different weekly pattern) from the heating demand for other buildings on the network. Where the district covers offices, or data centres, the heat recovered from cooling these buildings can be transferred to homes requiring heating (or other buildings with a heating need such as a community swimming pool).

Where the cooling demand is separated in time from the heating demand, surplus heat can be stored in ThermalBanks from the time it is available to the time it is needed. This efficient use of heat is at the heart of Interseasonal Heat Transfer and enables ICAX to provide cheaper heating and cheaper cooling than conventional methods, as well as proving heating and cooling with a very low carbon footprint.

Sharing heat between buildings

Many buildings have an overall cooling load over the year: they have a requirement to reject heat. This often applies to modern office buildings in south east England with extensive glazing and high solar gains. These buildings may be adjacent to older buildings with an overall annual heating load. ICAX has developed systems to allow for the transfer of heat between buildings: this form of heat transfer can save fuel and carbon emissions for both buildings.

Both buildings can benefit from a "heat sharing dividend" when they enjoy "joined-up heating and cooling".

Other buildings with a need to lose excess heat include underground train tunnels, data centres and supermarkets.

A comparison of the advantages of Heat Sharing Networks over traditional gas powered District Heating is shown in the Heat Sharing Table.

District Energy Management System

ICAX has developed a District Energy Management System ("EMS") to control the transfer of thermal energy from the times and places it is most cheaply available to the times and places where it is most needed. This involves control of Thermal Energy Storage to maximise the benefits, minimise costs and minimise carbon emissions.

Even in a group of similar houses there will be variations in the heating requirements between houses: some houses will be unoccupied during the working day, others with small children, or pensioners, may have higher heating loads during the day. IHT can meet these variations in demand successfully – and meter the use of heating in different buildings.

The combined benefits make Interseasonal Heat Transfer an attractive option for offices, schools and universities, hospitals, community centres, urban and suburban housing developments, industrial developments and private houses aiming for low energy use based on solar power.