In the Danish city of Silkeborg, 44 000 inhabitants, the wolrd’s largest solar thermal plant will be installed until the end of the year. The 12 436 large collectors will be mounted on agricultural areas in front of the city’s gate. Completed, the plant will have a total area of 156 694 m².

Solar heat in district heating complements classic gas-driven cogeneration plants. The collector field should deliver 80 000 MWh yearly and have a nominal power of 110 Megawatt. It should cover 20% of the heat demand in the district heating network of Silkeborg, and the complete summer load.The plant does not include a seasonal thermal energy storage, despite its dimensions. This leads to especially low heat costs and is enabled by the size of the city of Silkeborg, which has a high enough summer load to use all the solar heat directly when it is produced, explained Christian Stadler from collector manufacturer and general contractor Arcon/Sunmark: ‘We reach here scale effects that we do not know from previous projects. The bigger the solar plant is, the less influence the costs of the connection pipe have on the total costs. One is more flexible when looking for a suitable location.’

The solar plant in Silkeborg is more than twice the size of the until now largest solar thermal plant of the world in Vojens, DK. The 70 000 m² plant there was planned by the international engineering office Rambøll and realized by Arcon/Sunmark in 2015, just like the plant currently under construction in Silkeborg.

Beside gas and solar thermal energy, wind electricity should supply an increasing part of the heat in the district heating network of Silkeborg. Because of the fast wind energy development in Denmark, times with electricity excess and consequently negative electricity prices are becoming more frequent so that power-to-heat, transforming renewable electricity in heat, is profitable.