Solar power islanding

[Jake Platt]

Hello,

My company operates a 1.6MW solar power system in a net metering configuration in CA. Of course the inverter shuts the system down if the grid goes down. My question is can I somehow "island" the system using a transfer switch so I can continue to generate power if the grid goes down? In this scenario, if my pv system generates more electricity than I am using can I just send the excess electricity into a fly-wheel UPS system or even into a giant motor just to "burn" it up? What about sending the excess to ground? (fyi: I know I am crazy)

Thanks,
Jake Platt

 

[davenn]

hi Jake

you understand why the system gets shut down, don't you ?
and if so you will understand why it could lead to fatal consequences if it isn't shut down ?

Dave

 

[CWatters]

How frequently do you get power cuts in CA?

Storing excess energy from large scale solar plants (and intermittent wind turbines) is difficult. Currently I think only pumped storage is used on any significant scale. This details other approaches..

http://en.wikipedia.org/wiki/Grid_energy_storage

 

[Jake Platt]

I understand the risks, which is why I want to island the pv system from the grid. Further, I don't necessarily want to store the energy, just continue generating so some of it can be used and the excess either stored or burned off somehow.

 

[Jake Platt]

In the central valley of California, power outages are surprisingly regular during the summer.

 

[Khashishi]

It's surely possible, but there's probably a lot of caveats you won't get from an online forum. I think if you want to store hundreds of megajoules in a flywheel, you are probably looking at a flywheel weighing thousands of tons. They exist.

 

[CWatters]

I understand the risks, which is why I want to island the pv system from the grid. Further, I don't necessarily want to store the energy, just continue generating so some of it can be used and the excess either stored or burned off somehow.

I don't see why it can't be used if you have a suitable load on site. You would just need to satisfy your local grid company that there was no danger of you inadvertently supplying the grid while it was down (there are safety issue for engineers working on the lines and other issues).

I don't see any advantage in "burning it off" vs not generating it in the first place.

 

[gmax137]

I'm not sure how the PV inverters keep in sync with the grid. Someone told me recently that the inverters rely on the grid connection to provide the sync frequency. That might be another reason the system won't operate on loss of connection to the grid. Failure to re-sync when the grid comes back could be a big problem unless there's an operator or some kind of automatic system to do the sync.

 

[nsaspook]

I understand the risks, which is why I want to island the pv system from the grid. Further, I don't necessarily want to store the energy, just continue generating so some of it can be used and the excess either stored or burned off somehow.

It's very tricky to fool a grid-tie inverter with a local generator. It needs to qualify the line voltage and frequency, with a consumer quality mechanical generator that's pretty hard to do unless it's a inverter type like the Honda E series. When the inverter does start supplying power your load must at least match the Solar output to keep the voltage from rising out of range of the tie inverter or smoking your generator from the excess voltage.
http://www.metlabs.com/blog/emc/ul-...nverters-includes-anti-islanding-requirement/

For a home sized system the best method is to buy a system what will allow a small amount of the total system power to be used in an emergency if you don't want to deal with battery backed systems.

 

[russ_watters]

I understand the risks...

I don't think you do. The only responsible course of action here is to contact a licensed professional electrical engineer to discuss this (the solar integrator who set up the system probably has one on staff). We don't have one on site and will not assume any liability for property damage or injury caused by this. Thread locked.