Since the referendum vote in June 2016 and the decision to leave the European Union there has been considerable uncertainty around the implications of Brexit for the UK’s environmental policies. According to the Institute of Environmental Management (IEMA), 2017 will see a number of opportunities for sustainability, especially if ‘Article 50’ is triggered in March, as planned. These will include the vital role for heat networks and district heating systems with CHP.
Greg Clark, Secretary of State for Business, Energy and Industrial Strategy (BEIS) has already indicated that a carbon emissions reduction plan will be announced early in 2017. This will set out how post-2020 carbon reduction targets will be achieved through the ‘fifth carbon budget’, for which the UK government has already announced its endorsement.
In the light of this, IMEA chief policy adviser Martin Baxter has commented: “Achieving the UK’s Fifth Carbon Budget for 2028-2032 requires comprehensive action to tackle greenhouse-gas emissions from heating, transport and electricity generation. We also need to go much further and faster to significantly enhance energy efficiency.”
Much of the focus for tackling emissions from heating and electricity generation will fall on larger district heating schemes. However, there is also considerable potential for smaller schemes using centralised combined heat and power (CHP) which will be serving a vital role for heat network.
In such cases, as noted in Mr Baxter’s comments, enhancing energy efficiency is also critical. Therefore, simply installing CHP isn’t enough. Measures must be taken to ensure the CHP and the vital role the heat networks serve also performs optimally.
One of the key considerations for heat networks must be that the CHP is responsive to variable demand and retains its efficiency whilst doing so. In the past, with traditional fixed output CHP, this has been difficult to achieve and the run-times of the CHP have been greatly reduced in favour of less efficient boilers.
The answer is to deploy dynamic, load-tracking CHP (e.g. SAV’s LoadTracker) that maximises run times by modulating in line with electrical demand, while providing high grade heat at all times (ensuring compliance with CIBSE AM12/2013).
In this way, the ‘CHP % share’ is maximised, so that the energy and emissions benefits to the building operator are also maximised.
Moreover, the use of relatively small CHP units, which can be combined in modular ‘cascades’, opens the door to exploiting the benefits of heat networks in a wide range of building types.
Beyond central plant
Looking beyond the central plant, the vital role of heat network distribution systems must also support optimum efficiency and the heat interface units (HIUs) in the system play a key role.
In such systems, flow temperatures need to be constant and return temperatures need to be as low as possible. The CHP controls can ensure a constant flow temperature and to achieve low return temperatures the heat loss from the system to the heated spaces needs to be tightly controlled.
This requires the HIUs in the spaces, such as Danfoss FlatStations, to be optimised for both pressure and temperature control by incorporating differential pressure control valves (DPCVs). Not only will this guarantee precise and stable temperatures at the taps, it will also reduce system flow rates so that more heat is transferred to the space through the heat emitters resulting in lower return water temperatures.
Optimising heat networks and district heating systems in this way is the key to reducing emissions from heating and improving energy efficiency overall. Contact us to find out more about the vital role for heat networks.