Session: 09-05 Energy Storage Based on CO2

Paper Number: 129211

129211 - Pilot-Scale Testing of a Transcritical CO2-Based Pumped Thermal Energy Storage (PTES) System 

As the world moves toward an electrical generation system that heavily relies upon non-dispatchable resources such as solar photovoltaic and wind power, reliable, low-cost means to store electrical energy and dispatch it as supply and demand fluctuate are vital. As the proportion of non-dispatchable generation increases, more long-duration energy storage (LDES) will be needed.

Pumped thermal energy storage (PTES) consists of a reversible heat pump / heat engine cycle, where thermal energy is transferred between two reservoirs, one at high temperature and the other at low temperature. During the charging phase of operation, thermal energy is extracted from a low temperature reservoir (LTR), increased in temperature, and then stored in a high temperature reservoir (HTR) using an electrically driven heat pump cycle. During the generating process, the stored heat in the HTR is converted back into electricity using a heat engine cycle—-essentially the heat pump operating in reverse-—and the residual low-temperature thermal energy is stored in the LTR.

Unlike direct electrically heated (DEH) storage systems, PTES can take advantage of the heat pump’s ability to transfer more heat into the HTR than the electrical energy consumed. Thus, the performance of a PTES system will be higher than a DEH system even at low HTR temperatures, permitting lower-cost materials of construction to be used.

The PTES system described here uses transcritical Rankine power and heat pump cycles with CO₂ as the working fluid, a constant temperature phase change material (water/ice) LTR, and a sensible enthalpy material HTR. A pilot-scale (c.a. 100 kW) PTES system was designed, built and tested, including multiple LTR and HTR concepts. Data from this test sequence was used to validate component and system steady-state performance and transient system models. Further, this experience has informed the conceptual design of a 100 MW, 12 hour PTES system that is planned for deployment in 2028.

Presenting Author: Timothy Held Echogen Power Systems

Presenting Author Biography: Dr. Timothy Held is the Chief Technology Officer at Echogen Power Systems in Akron, Ohio, where he is responsible for development, maturation, and transition to product of supercritical CO¬2 power cycles and energy storage systems. Prior to joining Echogen in 2008, Dr. Held was with GE Aviation for 13 years, where he held leadership positions in several combustor design and fuels technology teams. He received a BSAAE from Purdue University in 1987, and a Ph.D. in Mechanical and Aerospace Engineering from Princeton University in 1993. He has published several technical journal articles and book chapters, and holds 49 U.S. patents.

Authors:

Timothy Held Echogen Power Systems
Jason Miller Echogen Power Systems
Jason Mallinak Echogen Power Systems
Vamshi Avadhanula Echogen Power Systems
Luke Magyar Echogen Power Systems