Do electric vehicle batteries on the grid make sense?

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By eeNews Europe

Almost everybody will agree that the power grid is undergoing radical rethinking and re-engineering. The old issues of reliability and capacity are still with us, but the new issues of renewable and sustainable generation technologies like solar and wind, the last-mile dilemma and escalating power demands coupled with significantly rising costs to the consumer are fueling the grid-level debates like never before.

Central to these debates is the role played by energy storage in the grid space. In the past I have talked about ultracapacitor energy storage on the grid or firming renewables to ease the integration of these technologies into the grid. But energy storage plays a much more important role than just stabilizing renewables’ output. It has the ability to change the way energy and power are managed on a second-by-second basis. Grid-level architects have just begun to scratch the surface of what energy storage can and will do for the power grid.


Electric vehicle battery. Source: Nissan Motor Corp.

It always comes down to economics and benefits to the ratepayer. Can a particular technology lower the costs consumers have to pay for the electrical energy that powers their homes? All the creativity that great minds can muster is being applied to address this fundamental question, not only the "if" but the "how."

One popular idea is the repurposing of batteries that are no longer fit for use to power an electric vehicle, to store and deliver energy on the grid. While it is an interesting thought experiment, the practicality of it is likely to be outside the realm of reasonable consideration. Keep in mind that these battery installations are huge, with many megawatt-hours of storage involved. This strategy has the potential to create a logistics nightmare of significant proportion. Batteries that have been exposed to the demands of EV use profiles and duty cycles are going to have a lot of mileage on them (no pun intended), and as such are going to carry a tremendous amount of overhead that will have to be managed for redeployment into the grid. Everyone knows the devil is in the details in most things, but in this case, you don’t even have to look at the details to conclude that there may be motives here other than trying to solve a grid-level challenge.

First are the considerations of logistics like battery chemistry compatibility and shipment of battery packs around the world to where they would be used. Tracking battery pack chemistry and putting like-chemistries together is one aspect of the deployment strategy that has to be managed. Further, getting high-energy packs from one place to another outside of a vehicle is a demanding pursuit subject to regulations and costs associated with those regulations, all making the concept less economically attractive.

Second is the relative use history and state of health of the car batteries going into a grid installation. One cannot just have two batteries of vastly different health characteristics work together as though they were made for each other. Complicated electronics that have yet to be developed will have to reside between them to manage the overall system performance.

Then there are the safety considerations. New batteries are subject to relatively high levels of safety concerns and used batteries multiply that concern. And what if the battery pack comes from a vehicle that had been in an accident? The pack could have sustained damage that escapes initial detection but reveals itself later in a large-scale grid episode. These are all things that put this strategy in a very precarious position relative to practicality.

Instead of promoting the flagging attractiveness of the electric vehicle movement by trying to figure out what to do with EV batteries that have reached their end of life, we should invest our efforts into finding appropriate solutions with reliable technologies such as ultracapacitors and new batteries for the grid. We should focus on optimizing solutions with real prospects for adoption and longevity, not making the electric vehicle market appear ready for prime time when we all know it will take a few more years.

Mike Everett joined Maxwell Technologies in 2002 and was appointed chief technical officer in 2005. Over a 25-year engineering career, Mike has been responsible for all levels of new product development, primarily focused on systems engineering and now the research and development of new technology.

This article first appeared on EE Times’ Planet Analog website.

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