Secondary Use Of Electric Vehicle Batteries Can Bring Benefits To The Solar Grid

- Jun 01, 2020-

With the rapid spread of electric vehicles worldwide, a wave of used batteries will soon appear, and the performance of these batteries is no longer sufficient to meet the needs of vehicles that need reliable acceleration and mileage. But a new study shows that these batteries still have the potential to provide backup storage for grid-scale solar photovoltaic power generation devices. In the next decade or so, secondary batteries can play a role in this less demanding field.


The research was published in the Journal of Applied Energy and was completed by 6 current and former MIT researchers.


As a test case, the researchers examined a solar power plant assuming a grid size. They studied the economic benefits of several options: constructing only a 2.5 MW solar power plant; constructing the same solar cell array together with the new lithium-ion battery storage system; and constructing the same solar cells using batteries reused on electric vehicles Array.


Researchers have found that new battery devices cannot provide a reasonable net return on investment, but as long as the cost of the battery is less than 60% of the original price, a system that properly manages used electric vehicle batteries may be a good profit investment.


Researchers said that this process may sound simple, and that it will occasionally be implemented in smaller projects, but it is not simple to extend it to grid scale. Ian Matthews, a postdoc at the Massachusetts Institute of Technology, said: "There are a lot of problems at the technical level. When you take the batteries out of the car, how do you screen them to make sure they are good enough to repeat use? How do you assemble the batteries of different cars together so that they can work well together? You also need to ensure that no one battery is much worse than other batteries, otherwise it will drag down the performance of the system. "


The study used a semi-empirical model of battery degradation and used measurement data for training to predict the capacity decay of these lithium-ion batteries under different operating conditions. It was found that the battery can achieve maximum life and value under relatively mild charge and discharge cycles. This discovery challenges some of the previous assumptions that running the battery at maximum capacity initially will provide the most value.


An unknown factor is how long the battery can work effectively in the second application. This study made a conservative assumption that when the rated capacity of the battery drops from the initial 80% (ie, from the moment when the electric car is decommissioned) to 70%, the battery will be backed up from their solar power plant Retired from service. However, Matthews said that it is very likely to continue to reduce the production capacity to 60% or lower may prove to be safe and worthwhile. He said that to determine this, a long-term pilot study is also needed. Many electric vehicle manufacturers have already begun such pilot studies.


According to a recent report by McKinsey Corp., a research firm, from now to 2030, the demand for backup batteries in renewable energy projects is increasing, and the secondary use of electric vehicle batteries may meet half of the demand.