Heat sources
technologies can ensure low heat prices because the technol- ogy getting more expensive by increasing prices can be turned down and other technologies turned up Design of new district heating networks Two main approaches can be considered when designing new networks and heat sources for new networks. If a large existing waste heat source is already available, it would be convenient to start delivery from this source the same way as the original heat source design. Focus should then be on ex- panding the heat network until the heat source design needs to be adjusted and supplemented with middle load sources. In the network expanding phase, the chosen reserve load tech- nologies should be suitable for middle load and, in the begin- ning, maybe only used for peak and reserve load purposes. In the end, the heat network demand may reach a level having a heat source design like the future design shown in figure 3. If no large existing waste heat source is available from the be- ginning, another approach may be better and recommend- able. Often it takes time to get consumers connected in new networks, and it can then be recommended to start up with the middle load technologies, also providing base load ca- pacity when the heat network is being built. This gives time to find a better high-grade waste base load technology that can take over with full capacity from finished construction a little later. This will make base load suppliers get the expected sales and revenue from the beginning. If no waste heat sources are available for base load in the new network area, this way of designing heat sources gives time to attract, for example, a new waste incineration plant to an area or to attract data cen- tres, hydrogen production plants, Power-to-X, all wanting to run constantly and deliver full load heat capacity. Especially for waste incineration plants and large, continually running waste heat suppliers, high heat delivery is essential and can trigger incentives for establishing solutions for delivering waste heat. The feasibility simply gets better when supply can be expect- ed full-time, and no heat is wasted like the blue shaded areas shown in figures 1 and 2. The middle load technologies, which were delivering all heat from the start, will now be able to deliver heat in the winter- time, deliver flexibility to the electricity system if based on elec- tricity and/or CHP, and ensure low heat prices. This is because the production can be changed according to electricity and fuel prices. If a heating system is constructed the right way, in- cluding heat storage, it will work the same as a battery, which can be very valuable for society and the electricity system sav- ing capacity and balancing costs.
Capacity MW
Peak load/ Reserve capacity
Around 2 - 5 % of production
100 %
Around 50 - 85 % of production Around 10 - 45 % of production
(Middle load capacity)
50 %
Base load capacity
Annual days
0
365
Figure 3 Base load heat source design according to capacity demand
demand in the summertime will be around 45% of the total demand, which should be the lowest designing point for base load heat sources. Often it can be beneficial to design the base load capacity a little higher, significantly if a storage system can absorb some of the extra waste heat. Figure 3 shows a situation where the base load covers 55% of peak load heat demand. When the base load capacity is 55% (MW), the share of heat delivered heat would be around 70% of demand (MWh). Po- tential heat loss if the base load source needs to run constantly is reduced to a very low level. The original heat source design will not be able to deliver all heat demand in the wintertime if the target is to use peak load source as little as possible. The heat source design then needs a low carbon “middle load” source to deliver heat in the wintertime. This can be a heat pump using air, other ambient sources, or low-grade heat waste heat from infrastructure sources - municipal wastewater treatment, water systems, Transformers, underground trains, gas compressors, mines, etc. - or allowed biofuels. The choice of middle load technology should complement the base load technology or at least not be dependent on the same fuel. If baseload technology is CHP-dependent on high electricity prices, it would be a good choice to choose a middle-load tech- nology dependent on low electricity prices, like heat pumps using ambient or low-grade waste infrastructure heat sources. The capacity of these middle-load technologies can be higher than the expected 40%, as shown in figure 3 if higher, the mid- dle load capacity can deliver peak low capacity and addition- ally be able to deliver reserve load capacity for the base load unit. This way, it can reduce fossil peak load capacity to zero. It additionally can be recommended to design these middle load source technologies in combination, maybe both having a heat source using a heat pump, a waste heat source, and/or a biomass boiler. If the power system needs power capacity, even CHP solutions could be considered. The combination of
For further information please contact: John Tang Jensen, JohnTang.Jensen@beis.gov.uk
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