480V to 125kV for a Energy storage facility - How is this best done?

[philks01]

I'm trying to learn more about how a bi-directional 10-20MW energy storage facility might be fielded and connected to high voltage. What is the most economical way to connect many 480V devices to the transmission grid.
It appears that this would normally be done with a substation transformer (say 125kV to 13.8kV) and then with a collection of 10-20 smaller transformers (13.8kV to 480V). This kind of dedicated facility would be expensive.

Is there any way to create a dedicated facility that might be more economical? Is there a way to go directly to/from high voltage?

 

[waross]

You may want to consider 35 kV as an intermediate voltage. It may be more economical in some configurations.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

I thin k the forst thing you need to work on is the concept of "storage" of electrical energy. That is probably one of the biggest challenges of our times. The rest of it after that is just details.

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[Miguel Villarroel]

You're talking about distributed generation at transmission level ?

If there was no electricity there would be no internet. Good point, don´t you?

 

[ScottyUK]

jraef is right - the costs of providing 20MW of energy storage for anything approaching a useful time period will make the cost of the grid connection little more than a blip on the bottom line.

What storage technology are you considering?


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[philks01]

ScottyUk and jraef,
Our company has experience with 100kW flywheels for energy storage. We have been contracted to look at producing a 500kW / 125kWh flywheel module with aggressive cost goals. We are currently funded for developing a smaller prototype that will prove the concepts required for the 500kW design. We have a unique design that we believe can compete with Beacon power on the flywheel unit. We lack knowledge on the power side beyond the drive, so we are looking to get educated.

 

[dpc]

We are currently funded for developing a smaller prototype that will prove the concepts required for the 500kW design. {/quote]

Better make the most of the prototype project.

Wind farms use an intermediate voltage of 34.5 kV or something in that range.

David Castor

http://www.cvoes.com

 

[ScottyUK]

Realistically you'll have to use an intermediate voltage because you won't be able to make a direct transformation from transmission level to low voltage. Switchgear isn't available which can cope with current of that magnitude, so you'll have to use a distribution system at maybe 11kV or the equivalent in the US and make LV connections into that intermediate system via transformers. That way you can probably use cheap & cheerful distribution transformers and only one transmission transformer and breaker, which is where the real costs are.

Watch out if there's a high X/R ratio due to the stored energy devices because most distribution breakers don't like the long time to first current zero crossing, which can get a bit awkward during a fault.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[Miguel Villarroel]

Energy as such is found in abundance in nature, thanks to god, and expects for us to use it, I think we would have to check only when to use one or another source, I wonder why to storage energy we produce in form of electricity. If we lived in a place dry of energy it would be mandatory to storage production for later use

If there was no electricity there would be no internet. Good point, don´t you?