Yearly thermal performances of Danish solar heating plants

he number of Danish solar heating plants in district heating areas increased strongly from 16 plants in 2009 to 123 plants in 2019. Many of the plants were installed in district heating systems with natural gas boilers due to good economy. The thermal performance of most of the Danish solar heating plants have been measured for many years. The average yearly thermal performance for the solar heating plants for the period 2012-2023 is 459 kWh/m² solar collector and the yearly average utilization of the solar radiation for all the years is 40%. Solar district heating plants are based on a simple, well proven and reliable technology. They supply heat with a relatively low cost of about 0.04 euro/kWh and the used solar collectors have a lifetime longer than 30 years. The solar heating plants provide about 2% of the total heat demand in Danish district heating areas. In spite of the good experience from the plants, the Danish market for solar heating plants collapsed in 2020. Solar heating plants are produced in Europe, the plants contribute to a global reduction of CO2 emissions, even with a strong growth of installed systems. It is therefore hoped that the market for solar heating plants soon
will be reestablished.