HEAT NETWORKS District heating: past, present and future I
Neil Parry, global head of district energy, Armstrong Fluid Technology discusses the true benefits of district heating and how to make it work in the UK if we are to achieve carbon reduction targets
f we are to meet our carbon reduction targets and commitments, we need wholesale change. We will not achieve the scale or the required change if we rely on individual households to individually ‘do their bit’. At the individual level, it is very difficult to utilise renewable energy sources effectively, due to the huge variances of peaks and troughs associated with individual dwellings. By amalgamating multiple dwellings, while the load is increased, the delta between the peaks and troughs is reduced and a stable base load is created. This stable base load allows for better utilisation of renewable sources. Storing the energy from these sources during times of low demand/ high production (within thermal stores for example), also allows the renewable sources to meet the higher, peakier demands, by using the stores to augment the source outputs at these times. District energy does exactly that. It groups together large numbers of end users, allows large scale renewable sources to be employed, dramatically reducing the carbon emissions associated with heating, cooling and DHW production. This approach has already delivered significant improvements in other European countries. For example, Figures 1 and 2 demonstrate the carbon reductions achieved by heat networks in Sweden. While the amount of energy supplied via district heating has risen consistently since 1969 to 2014, the second graph shows the corresponding reduction in carbon emissions over the same period. So despite more energy being supplied, the carbon implication of that energy, has dramatically reduced. District energy therefore is a proven method of wholesale carbon reduction.
Planning for the future
So, if district energy reduces carbon and allows for greater integration of renewable energy sources, we need to proliferate their use in both new build and existing housing stock, creating new energy networks and expanding existing networks. Looking at the projected growth through 2030, 2040 and up to 2050, we can see that all countries within the EU are predicting significant growth in heat networks. Cooling networks are similar although the rate of expansion has a far greater variance by country. The UK has a plan to increase heat network use from its current level of 3% (of heat supplied to buildings) to 19%, by 2050. A significant increase. The global market is conservatively forecasted to hit 270Bn (USD) by 2028.
Roadmap for carbon reduction
District energy is the great facilitator. It is energy source agnostic and facilitates the use of a variety of sources, from waste heat from industrial processes for example, through various renewable sources, such as solar, biogas, geothermal etc. to hydrogen, CHP, heat pumps and natural gas boilers. Improvements and changes at the energy centre, such as replacing a gas boiler with a heat pump, for example, allows for a wholesale reduction in the associated carbon emissions for hundreds or thousands of dwellings. District heating and district cooling are two of the four ‘power grids’ that are required for sector coupling. Once a building is connected to a network, then its supply of heating and/or cooling is future proofed and taken care of, by the network. As mentioned, the amalgamation of the peaks and troughs of individual energy demand are reduced in terms of their delta and the increased baseline demand level allows for greater renewable integration. Again, these economies
18 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JANUARY 2024
of scale also allow for the easy integration of thermal storage on a large scale, further enhancing the utilisation of renewable energy and thereby minimising the use of more carbon intensive sources such as natural gas boilers. Historically, here in the UK, our heat networks have not performed well. This is due to many aspects around the knowledge, experience, design, installation, commissioning and operation. To address this the Heat Network Technical Assurance Scheme (HNTAS) is in the process of being created. The network as a whole has been split into 6 distinct areas and teams created to produce the data/documentation accordingly. It is a performance/outcome orientated scheme and is enforceable.
So how do we ensure efficiency of district
energy networks? The key is to maximise the operating delta T of the network. This holds true for all networks whether heating or cooling. Why is this? The simple formula, flow rate = the required power, divided by the heat transfer co-efficient multiplied by delta T shows that the greater the delta T, the smaller the required flow rate to supply the required power. So the more we increase the delta T, the less flow we need to send around the system. This reduced flow can result in major capex savings as the pipe- work, fittings, valves, thermal stores, pumps etc. can all be smaller. However, the benefits don’t stop there. The reduced pipe-work size gives rise to reduced heat losses from the network. The reduced losses are significant as heating and cooling networks can be km’s long. As the pump is smaller, it will use less electrical energy and should be able to pump at lower flow rates
when the system is at low demand. This reduces the bypass flow, can further reduce the network losses, and also reduces the system inertia which can have benefits in other areas, such as speeding up DHW response times. Typically, increasing the delta T means
reducing the return temperature on heat networks. Having a lower return temperature at the plant-room improves the efficiency of condensing boilers, as they can condense more. Looking at some renewable sources, such as solar thermal and heat pumps, the lower return temperature allows the renewable sources to potentially supply a greater share of the load. With CHP, the lower return temperature allows the CHP to ‘get rid’ of its heat more easily and to therefore avoid the risk of the CHP shutting down as the engine overheats regardless of whether there is a heat and/or electrical demand at that time.
Read the latest at:
www.bsee.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38
