MIT study reveals the ‘Reuse Potential’ of Electric Vehicle Batteries
The use of electric vehicles has been growing rapidly over the past ten years, with the global stock of electric passenger cars passing 5 million in 2018. Also, the advancement in technology including development in battery chemistry and expansion of production capacity in manufacturing plants is resulting in substantial cost cuts.
Increased awareness for environmental conservation among the masses and governments and lower greenhouse gas emissions from electric vehicles as compared to internal combustion engines are also a few of the reasons for growth in the EV (electric vehicle) industry.
But this rapid growth would also result in increased disposal of used batteries that no longer deliver value to the electric vehicles.
The Problem with Solar Installations
The number of solar energy installations is growing across the world. But there are two major problems associated with these installations:
- They can only generate electricity during the daytime. Therefore, during cloudy days or at night, these installations, in a way, become dead. Hence, there will always be a need for energy storage due to this limitation of solar installations.
- A large amount of solar energy is available during the middle of the day but peak loads are seen during the later part of the day.
Li-ion batteries are a good means of storing energy but they are quite expensive.
A new study by a team of MIT researchers shows that these used electric vehicle batteries could provide a golden opportunity for solar power plants. These batteries could be useful for backup storage for grid-scale solar photovoltaic installations.
Testing the Opportunity
Six current and former MIT researchers, including postdoc Ian Mathews and professor of mechanical engineering Tonio Buonassisi studied the economics of 3 scenarios and calculated the revenue that could be generated under each scenario:
- In the first scenario, they studied a 2.5-megawatt solar farm alone without any battery storage
- In the second scenario, same array of solar panels with a new lithium-ion battery storage system
- In the third scenario, they studied battery bank made of used EV batteries that had declined to 80 percent of their original capacity.
Assumptions during Research
The team made a few reasonable assumptions while testing the project.
- An electric vehicle owner will want better performance from their car and will likely dispose of the battery when it reaches 80% of its capacity as it would be considered too weak for continued vehicle use.
- Battery storage would be used for hours when the sun is not available.
What Team Found?
They found that used EV batteries purchased at 80 percent of their original capacity and at 60 percent of the original price will deliver better revenues for the solar plant and will prove to be a profitable investment with all other factors remaining the same.
Challenges in Arriving at the Solution
- The team explains that even though it is easy to implement the solution at a small scale, but scaling it to the grid-scale is not simple.
- There is currently no proven method to screen the batteries disposed of the car and decide whether they can be reused for solar applications.
- The third challenge involves building an all-purpose, second-life battery management system. “There’s more work that is to be done in that area,” Mathews says. “It involves collaboration between people who have the data, people who can build smart control algorithms, and the people who build the electronics around these systems.”
How long can the reused batteries last?
The study made an assumption that the batteries would be retired from their storage system in solar-farm after they had declined to 70 percent of their rated capacity, from their initial 80 percent (i.e. the point when they were retired from use in electric vehicles). But researchers expect that operating at 60 percent of capacity or even lower might be safe and worthwhile. However, long-term pilot studies will be required to determine that.
Mathew explains that the actual economics of the project with repurposed electric vehicle batteries could depend on the local regulatory structures i.e. economics of such systems will be very site-specific with some local rules allowing the cost of storage systems to be included in the overall cost of new renewable energy supply, while others not.
At the residential scale, more applications of used EV battery-based storage system will be seen in the near term, says Mathews.
Through this research, the team proved the functional viability of the system. As a next step, it is required to involve all the stakeholders in the EV ecosystem such as EV manufacturer, lithium-ion battery manufacturer, solar project developer, etc. to validate the technology and economics at the grid-scale.
Once validated at scale, multiple business models can be worked out and more profitable markets can be uncovered for commercial success. The idea can also be further taken by startups or entrepreneurs who are planning to enter in EV or renewable energy sector.
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