Spring in Denmark not only means longer and brighter days but also the beginning of the first “harvest season” for a unique solar energy system. A 26 929 m2 concentrated solar power (CSP) plant currently provides the city of Brønderslev with sustainable heating, but will soon also enable power production as an add-on to a biomass-fired organic rankine cycle (ORC) system scheduled for completion in the latter half of 2017.
The CSP system, developed by Denmark-headed renewable energy specialist, Aalborg CSP A/S, has been operational since the end of 2016, but it was not until the sun appeared high on the Danish sky that it reached full capacity.
The 16.6 MWth solar energy system currently supplies heat to the district heating network, but soon it will also contribute to power production when a biomass – Organic Rankine Cycle (ORC) plant goes operational later on this year.
This combined integrated solution will be the world’s first large-scale system to demonstrate how CSP with an integrated energy system design can optimize the efficiency of ORC even in areas with less sunshine.
Spring sunlight illuminate 5-km of receiver tubes
The solar energy plant is based on the CSP parabolic trough technology consisting of 40 rows of 125 m U-shaped mirrors with an aperture area of 26 929 m2. These mirrors collect the sun rays throughout the day and reflect them onto a receiver pipe, which totals five kilometres (km) in length.
This receiver pipe is surrounded by a special glass vacuum tube and inside this runs thermal oil heated solely by sunlight to temperatures up to 330 °C. This high temperature is able to drive an electric turbine to produce electricity, but the flexibility of the system also allows production of lower temperatures for district heating purposes.
Thus the solar heating system can alternate between providing combined heat and power at peak price periods or exclusively deliver heat. On sunny days, the solar-thermal system is set to reach 16.6 MWth capacity.
Record delivery time
The achievement of the world’s first CSP system combined with a biomass-ORC plant is supported by the Danish Government’s Energy Technology Development and Demonstration Programme (EUDP). The subsidy provides substantial support for technology development thereby making the Aalborg CSP solution more competitive in export markets, such as Germany, Austria or Italy that have a well-established district heating infrastructure or an existing base of ORC plants.
While the prices of different types of fuel fluctuate, concentrated solar energy proves to be a stable and efficient renewable alternative in Europe. Aalborg CSP was awarded the contract to develop and deliver the solar energy plant to Brønderslev Forsyning district heating plant in February 2016.
Construction and installation of the system set records as it reached completion in just six months. With the beginning of the Danish solar season, the CSP plant harvests the sun for district heating purposes but soon it will also enable electricity production when the ORC plant is commissioned in the latter half of 2017.