Commissioning and initial testing
During the past months, all of the Compressed Heat Energy Storage (CHEST) system components were combined and connected to the heat source and -sink and as well to the electrical power supply at the DLR laboratory in Stuttgart, Germany. The components were filled with the working fluids and the control systems were powered up.
After an overall check, the commissioning of the CHEST system was performed. This is a two-step procedure:
- First step: The Thermal Energy Storage (TES) is preconditioned until the required temperatures and conditions for startup are reached. The High Temperature Heat Pump (HTHP) is then activated and the TES is charged, with the LHTES condensing the working fluid. This process was repeated several times while the operating parameters were modified for the lab system environment until a steady-state operating point was successfully achieved for the HTHP/TES combination.
- Second step: The Latent Heat Thermal Energy Storage (LHTES) is charged by a separate steam generator to provide defined starting parameters. Then, the LHTES evaporates the working fluid and is thereby discharged, powering the Organic Rankine Cycle (ORC). Here also several test runs were conducted and also here a steady-state operating point could successfully be realised.
By completing the commissioning procedure, an important milestone as well as the proof-of-concept was achieved.
DLR laboratory with HTHP, LHTES unit and sensible heat TES tank (from left to right)
ORC and second sensible heat TES tank (from left to right)
Full cycle testing
For the start of the full cycle experimental analysis, two test campaigns were necessary:
- In the first campaign, the two cycle halves of HTHP and TESS operation and TESS and ORC operation were investigated independently. The aim was to learn about the behavior of the subsystems HTHP/TESS and TESS/ORC in the overall CHEST system and to determine the best control methods. Some of the system parameters from testing in the individual labs needed to be adapted for full-system operation in the DLR laboratory. From the results of this first campaign, test parameters were derived and initial full cycle test parameters determined.
- In the second campaign, experiments with the full CHEST system are being conducted. A first full cycle test was conducted on June 28, 2022, providing a first proof-of-concept of the full CHESTER lab prototype and the CHEST system. Operation of the HTHP with condensation in the LHTES was conducted for about 4.5°h and evaporation in the LHTES to power the ORC for about 2.75°h.
Next Steps
The data from both the first and second test campaigns is currently being analysed and the next experiments are being planned. Further results and analyses from the operation of overall CHEST system are expected after the summer.
