Electric school buses

[LisaC]

Hello,

I am the Head Mechanic for a school District in Upstate NY. Our state has passed a law in regards to electric vehicles and my District is currently investigating electric school buses. While I am on board with this, I would also like to save the District and tax payers as much money as possible by not getting the electricity from the grid, so I have been looking into various solar options.

The most likely candidate for the buses would be the Blue Bird Vision. It has a battery capacity of 155kWh (Li-ion NMC/G cell) with a range of 120 miles. While we would only be getting one to start, we would eventually need to replace all thirteen big buses. Does anyone have any recommendations or experience with this application?

Thank you,

Lisa

 

[DThames]

One comment, you are fairly lucky that for most of the day the buses will be parked so could charge directly from solar. Trying to store the energy just adds cost. What are your grid tie credit options? While is nice not to have to get all the power from the grid, you can put to the grid when you are not charging. For example when the buses are out for afternoon drop off and in the summer, you could be banking power with the power company, then bring it back from the grid when your solar conditions don't meet your needs for any given day.

 

[LisaC]

I am looking into solar to supplement the cost of buying power directly from the grid but I want the option of storing it in case of power outage. I really don't know much about the credit options as I haven't gotten that far into the rabbit hole. I am trying to figure out how big of an array I would need and the most efficient way to meet our power needs.

 

[DThames]

I am looking into solar to supplement the cost of buying power directly from the grid but I want the option of storing it in case of power outage. I really don't know much about the credit options as I haven't gotten that far into the rabbit hole. I am trying to figure out how big of an array I would need and the most efficient way to meet our power needs.

If the bus shed/parking is on the same property as the classroom buildings, oversize the array enough that you can cover part of the power needs of the classroom building, so you will have extra solar capacity. There are cloudy days and they have a huge impact on production. If you are grid tied, you can push back any unused for credit.

Also, compare the cost of battery storage to generators for emergency recharge. Because you are using this power only some months of the year (idle in summer), having expensive batteries just sitting there is less cost effective as batteries that actually get some use and at least try to earn their keep. Batteries are effective when their use during peak hours for the utility company will save you money but cutting peak charges. But other than that batteries are like a stone around your neck. They cost in several ways and almost never give anything back. Generators don't wear out just sitting idle. Batteries do.

 

[LisaC]

I was under the impression that batteries allow you to get more bang for your buck, allowing you to use the power your arrays produce, rather than selling the power back to the grid for less than it is worth.

 

[LisaC]

Though I really have to figure out how big of an array I need per vehicle before I can accurately crunch any numbers. I am still on the hunt for someone that actually uses these buses that can give me an accurate accounting for their power usage.

 

[DThames]

I was under the impression that batteries allow you to get more bang for your buck, allowing you to use the power your arrays produce, rather than selling the power back to the grid for less than it is worth.

My state energy regulations/law says the power company must give full credit for what I give them. I currently have more than 6 months worth of electric power credit on my account. They credit (not purchase) my excess. I can then use it at a later date, one for one in KWH. Some states have different ratios of give and take from the grid, as there is a cost with delivery, even if you previously gave some to them. We pay a monthly service access fee to cover line and connection costs. So check your laws and check with the power company.

 

[BradCagle]

I am still on the hunt for someone that actually uses these buses that can give me an accurate accounting for their power usage.

"it has a battery capacity of 155kWh (Li-ion NMC/G cell) with a range of 120 miles."

Does this ^^^^ not give you accurate accounting of the power usage?

155kwh / 120m = 1.291666666666667kw per mile

 

[DThames]

Imagine this......You need about 50k watts of solar to charge X number of buses, charging 4 hours per day. That is 4 good sun hours, 10-2.
1. Install 100k watts of solar that is grid tied. Anything you don't use, goes to the grid for credit.
2. Connect the school building so if you are making more than 50k watts, the school can use what you are not using, cutting their bill.
3. On days with less than good sun, the 100k watts might produce the 50k watts that you need.
4. If you don't make 50k watts, use from the grid to supplement.
5. Use generators if there is a power outage.

Regardless of the amount of power that you need to charge the buses, look at putting in more for reasons described above. Look at that solution compared to any solution that includes batteries.

 

[LisaC]

"it has a battery capacity of 155kWh (Li-ion NMC/G cell) with a range of 120 miles."

Does this ^^^^ not give you accurate accounting of the power usage?

155kwh / 120m = 1.291666666666667kw per mile

Sorry I didn't state it clearly. I was looking for actual numbers, not the numbers from the manufacturer. I did this math already :D