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It is an ever more cost-effective proposition: Using solar-thermal collectors to feed carbon-free heat into district heat networks to supplement or replace other sources. Indeed, it seems German heat providers have discovered the biggest supplier of them all: the sun.
To date, solar-thermal plants have delivered only a tiny share of the energy supplied through district heat networks in the German market. However, growth is expected to accelerate, with experts mooting the need for annual installations to increase multitudinously if government climate targets are to be met.
Thirty-four solar-thermal plants with a total collector area of 62,700 m² and an installed capacity of 44 MWth currently feed into district heating networks in Germany, with a further 19 MWth planned to start operations in 2019.
The largest facility is operated by the municipal utility Stadtwerke Senftenberg in the state of Brandenburg in the east of the country. Last year alone the 8,300 m² array generated an impressive 4,720 MWhth.
However, Stadtwerke Ludwigsburg-Kornwestheim, a municipal utility in the south-western state of Baden-Württemberg is set to take the crown shortly with a plant spanning nearly 15,000 m².
“Solar-thermal is essential to the decarbonisation of district heating,” says Helmfried Meinel, Director General at Baden-Württemberg’s Ministry of the Environment, Climate Protection and the Energy Sector. “We are happy and also a bit proud that our state has become a hotspot for large solar district heating plants. As a state, we will continue to support this dynamic development.”
Dirk Mangold, head of the research institute Solites, expects the number of plants to double and capacity to treble in the next five years: “This figure is based on ongoing projects and concrete feasibility studies with the probability of realisation factored in,” he states.
But Mangold sees this as just the start: “The German government wants to increase the share of solar-thermal in district heating massively by 2050. A 15 percent share would correspond to 12 TWh per year. That would require an installed capacity of around 21 GW or a collector area of around 30 million m². That means we need to be constructing 1 million m² per year. And that means fifty times more than the current market.”