An international team of researchers has designed a new hybrid photovoltaic-liquid energy storage system (PV-LAES). Their financial evaluation of the proposed 2 MW PV-LAES project showed that the investment payback period could be 10 years and the accumulated net profit could be up to $2.2 million from a life cycle perspective.
Designed for large-scale use, LAES systems store electricity in the form of liquid air or nitrogen at cryogenic temperatures – below -150 C. They are charged by using excess electricity to compress and liquefy air, which is then stored as a liquid. Temperatures approach -196 C. As they discharge, the liquid air heats up and turns into a pressurized gas, which uses a turbine to generate electricity.
The proposed system comprises a 2 MW local solar power plant equipped with a maximum power point tracking (MPPT) boost converter. The plant is able to produce low-carbon electricity with small fluctuations between 12.89-12.99 MWh per day
The LAES unit utilizes the surplus power of the solar power plant and compensates the power of the local load with an insufficient power level. The duration of the system’s energy storage outside of peak time is 9.13 hours, and the duration of energy release during peak time is 6.27 hours.
For the proposed PV-LAES project, the results show that the surplus renewable electricity of 6.73 MWh sent to LAES is used to produce 27.12 tons of liquid air for daytime energy backup. There, the round-trip efficiency of the LAES unit is 47.4% and it can discharge flexible power compensation to the load at night.
At the same time, the power demand of the main grid decreases significantly from 12.78 to 3.33 MWh per day. Based on this information, the annual electricity saving is estimated to be 3449.25 MWh and the corresponding carbon dioxide emission can be reduced by 2607.63 tons.
In terms of financial performance, the PV-LAES system has a dynamic payback period of 9.33 years and an accumulated lifetime net profit of $2,260,011, the researchers found.
They discussed their findings in the paper “Hybrid photovoltaic-liquid-air energy storage system for deep coal removal”. Energy science and technology.
“The proposed PV-LAES system is economically feasible from a life-cycle perspective and can potentially realize flexible energy interaction with local renewable energy sources to achieve an integrated low-carbon power generation and storage system, the researchers concluded.