Electric School Buses to Feed Power Grid
New York also has announced Electric School Buses to Feed Power Grid. The New York pilot program to use bus batteries to the power grid during peak demand. The vehicle-to-grid school bus movement is beginning to gaining traction in East Coast states. This as part of New York’s electric company Con Edison’s vehicle-to-grid pilot program based in the White Plains district.
The Lion Electric Co. buses are equipped with bidirectional inverters, meaning they can charge the bus, or store energy and feedback into the electrical grid, taking cues from smart software technology and chargers developed by San Diego-based Nuvve Corp.
The plan is for when the students are home with their families, the parked buses’ batteries will be put to work, feeding back into the power grid to supplement supply.
The goal is to use the energy stored in the batteries to support the grid during the hot summer months when demand is at its peak. If successful, the project could be replicated in other districts.
Lithium-ion batteries cost are the problem
Battery based electric school buses can be 2 to 3 times more expensive than regular gasoline school buses.
There isn’t any sign that batteries cost can be reduced significantly in the near future.
Lithium-ion batteries typical lifespan
A typical lifespan for Lithium-ion batteries warrantied by manufacturers is 3-5 years.
If the batteries can be used over 20 years without degrading, the average cost of batteries will be reduced by 50-75% per year.
How to improve the lifespan to 20 years
In general, according to the data from one of a leading manufacturer of Lithium-ion batteries. Depth of discharge (D.O.D) affects the cycle life. Detail calculator
| D.O.D | Cycle Life | Lifespan (1 cycle per day) |
| 100% | 1000 | ~3 years |
| 90% | 3000 | ~10 years |
| 80% | 5000 | ~14 years |
| 70% | 7000 | ~20 years |
Instead of using the battery system at 90% D.O.D., 70% D.O.D. will improve the life cycle to 7000.
Assuming 1 cycle per day, 7000 cycles mean 20 years of usage without degrading.
It just requires a battery system with a slightly larger capacity.
Conclusion
Careful design of the battery management system to make ensure the D.O.D is at a low level, the average cost of the batteries can be reduced at least 50-70%.
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