HEAT SOURCE DESIGN FOR DISTRICT HEATING NETWORKS
For district heating network companies, the difficulty is to get this financed and, at the same time, avoid too high heat prices from a depreciation of investments in multiple technologies in the first 10-15 years. It must be recognised that heat networks and heat source technologies have a long lifetime—at least 30 years for heating networks. If the -producing technologies are kept warm when not running and maintained properly. Most technologies have a lifetime above 60,000 hours of the entire load operation. The lifetime in years then can variate from 15 up to 30 years. To keep the heating price low, it should be al- lowed to depreciate the heat production technologies accord- ing to actual total load hours running time instead of linear annual depreciation independent of running time. This will ensure low heating prices according to used heat sources and technologies. It is better to have many technologies with different heat price profiles designed to use heat sources optimally compared to a few heat sources with price dependency on fossil fuels and electricity. The district heating network company should own ambient in- frastructure, reserve, and peak-load heat source technologies to ensure supply security and competitive heat price if base- load waste heat sources are purchased from external sources. Base-load heat sources like heat from waste incineration and other co-production sources should be designed for 24/7 heat production to minimise capacity investments and ensure low heat prices, including capacity costs.
delivers a flexibility to the electricity system and, to some ex- tent, disconnects heat prices from varying fuel and electricity prices. Heat pumps using ambient heat as a source will have a mid- dle-load capacity in heat networks with heat from waste incin- eration, infrastructure sources, and waste heat from the indus- try as base-load. Future base-load heat sources will typically be purchased from a heat supplier. Middle- and peak-load sources will typ- ically be developed and owned by a district heating network company.
Figure 7 shows an example of a new heat production design.
The size in capacity (MW) and delivery (MWh) may vary de- pendent on accessible heat sources, available capacity, re- liability, fuels, and electricity prices. To get a low average marginal heat price from the technologies, the total sum of capacities for base- and middle-load technologies may need to include needed reserve- and peak-load capacity as well. This will increase the investments but decrease the use of often expensive fossil fuels in reserve- and peak-load tech- nologies In the end, a district heating network can end up having more capacity than needed, but this “extra investment” in capacity will be leveled out by having different options depending on the market prices the sources are operating on. The heat price can always be optimised if other options are available, and heat storage is included to absorb cheap heat produced when the market price is the best.
For further information please contact: John Tang Jensen, JohnTang.Jensen@beis.gov.uk Morten Jordt Duedahl, md@dbdh.dk
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