In the town of Langkazi in the southern part of Tibet, a 15,000 m3 Pit Thermal Energy Storage (PTES) enables storing of excess solar heat covering more than 90% of the city’s annual heating needs.


Client:       Arcon-Sunmark Large-Scale
   Solar Systems Integration Co., Ltd
Owner:         Local government of the
   autonomous region of Tibet
Location:    Langkazi, Tibet
Status:    Operationel

Seasonal storage for optimal use of the sun

A 15,000 m3 Pit Thermal Energy Storage (PTES) system was installed alongside and integrated with a 22,275m2 solar field consisting of flat solar-thermal panels. The PTES stores excess solar heat from the solar field enabling optimal use of the solar resources. During summer, the amount of  heat produced exceeds the district heating demand, whereas during wintertime the district heating demand exceeds the solar heat produced. During winter, hot water from the top of the storage is therefore withdrawn and released into the city's district heating network.

PTES and solar covers 90% of heat demand

With a capacity of 17.5 MWt, the PTES is able to store 700 MWh heat. Combined, the solar plant and PTES cover more than 90% of the district heating plant’s annual heat production. A 3MW electrical boiler serves as backup energy supplier and is responsible for supplying the remaining 10%.

The project was developed and installed by Arcon-Sunmark Large-Scale Solar Systems Integration Co., Ltd, which was established as a joint-venture between Chinese Jiangsu Sunrain and Danish Arcon-Sunmark. In June 2020, Aalborg CSP acquired all know-how and intellectual properties related to the PTES technology from Arcon-Sunmark.



Andreas Zourellis
VP Sales - International
District heating / industrial solar technologies
Phone: +45 50 30 00 25