The purpose of this experimental facility is to study the use pressurized gases as working fluids in parabolic-trough collectors, which has not been done to date, evaluating their behavior under a diversity of real operating conditions.

The experimental test loop is located north of the DISS loop control building, which houses the equipment necessary for its control and data acquisition.

View of the pressurized gas test loop connected to a molten salt thermal storage system.

The facility was originally designed to work at pressures and temperatures of up to 100 bar and 400ºC, and consists of the following components:

  • Two East-West-oriented EUROtrough parabolic-trough collectors, each 50 m long with a 274.2-m2 collector surface. The collectors are connected in series.
  • An 400-kW air-cooler able to dissipate the thermal energy in the fluid delivered by the collectors. It has two 4-kW motorized fans
  • A blower driven by a 15-kW motor which supplies the gas flow necessary to cool the collectors adequately
  • A data acquisition and control system that allows the temperature, flow rate, pressure, irradiation and humidity in the loop to be completely monitored.
  • Automatic control valves that allow precise, safe variation in the collector fluid feed flow rate.
  • A secondary loop for filling the test loop with gas.

Since testing at 400ºC was successfully completed at the end of 2009, this facility was then up-graded to achieve temperatures of up to 515ºC and it was connected to a two-tank molten-salt thermal storage system to test their joint capacity for collecting and storing solar thermal energy with a view to making use of them in dispatchable high-performance thermal cycles. This increase in test loop design conditions to 100 bar and 515ºC made the implementation of different improve-ments necessary (conventional absorber tubes in Collector 2 were replaced with advanced high-temperature tubes, stainless steal pipes were installed for the high temperature zone and changes were made in the control system).

Simplified system diagram of the innovative fluieds test loop connected to a molten-salt thermal storage system

The molten salt thermal storage system which forms part of a larger experimental salt loop, basically consists of:

  • Two 39-ton salt tanks, hot and cold, able to provide about six hours of thermal storage
  • An 344-kW air cooler to cool the salt with ambient air
  • A 344-kW gas/salt exchanger providing the salt circuit with the solar energy collected in the innovate fluids test loop

The thermal storage system is also connected to a small 344-kWt thermal oil loop, with VP-1 oil, allowing the thermal storage system to be charged and discharged by using this thermal oil system, with a salt/oil heat exchanger. This oil circuit consists of: expansion tank, drainage tank, oil heater, salt/oil heat exchanger and oil cooler.