On January 25th, EDP, a Portuguese based utility company, was approved to deploy a 1MWh vanadium flow battery system as part of a hybrid energy storage project at a soon to be decommissioned thermal power plant in Asturias, Spain. The liquid flow system is named REDOX2025, with a rated output power of 0.25MW, a rated capacity of 1.05MWh, and a discharge duration of 4.2 hours. EDP stated that its goal is to deploy 1GW of energy storage systems by 2026.

Liquid flow batteries are different from lithium-ion batteries in that they decouple the power and capacity of the system, allowing for independent configuration and variation. The power portion of EDP's flow battery will be installed in a 20 foot (6.1 meter) standard container, which includes 16 stacks, 8 pumps and valve pipelines, and a Battery Management System (BMS). Based on this calculation, the rated power of each fuel cell stack is 16kW, which is relatively small compared to the current power range of commercial grade fuel cells in China, which is between 30-50kW.

The energy part of this system consists of eight electrolyte tanks, which will fill a total of 58 cubic meters of vanadium electrolyte and an electrolyte heat control device. At present, the vanadium concentration in the commercial market of China is generally 1.7M, and the theoretical capacity of vanadium electrolyte per cubic meter is about 50kWh. Based on this, the theoretical capacity corresponding to 58 cubic meters of vanadium electrolyte is calculated to be 2900kWh. Considering that the flow battery system requires the same capacity of electrolyte to be configured on both positive and negative electrodes for redox reactions, the theoretical capacity of the flow system will be half of the electrolyte, which is 1450kWh. According to the nominal rated capacity of the system of 1.05MWh, the utilization rate of the electrolyte can be calculated to be 72%, which is higher than the commonly used 60% utilization rate level in the industry.

The thermal power plant was originally scheduled to retire last year, but due to the energy crisis caused by Russia's invasion of Ukraine, the plant has remained in operation. The EDP plan is to turn the power station into a renewable energy power station that combines multiple technologies, as shown in the following figure.

The construction of runoff hydropower stations and solar photovoltaic arrays is already underway. EDP states that the energy generated will mainly be stored in the form of green hydrogen, while the excess energy will be stored in a combination of lithium-ion batteries, flow battery systems, and recycled power batteries. It is still considering establishing a liquid air energy storage system. The stored green hydrogen gas can be used for decarbonization transportation and in combined cycle gas factories. Today, most people agree that the round-trip efficiency of using green hydrogen to convert electricity back is too low and currently does not have economic benefits.

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