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Is there a good technical analysis on whether microgrids are helpful in the context of a first world country with a reliable, well-run large electricity grid?

Is there a good technical analysis on whether microgrids are helpful in the context of a first world country with a reliable, well-run large electricity grid? On the face of it, larger grids seem better. I simply don't believe this claim in the NYT article: "microgrid also eases the burden on the local utility, because it can disconnect from the larger grid during a period of overload". (Either the microgrid doesn't have enough power or has too much; either way it'd be better to share its resources, no?) As a PG&E customer I'm stretching a lot to assume "a reliable, well-run grid". I've got my own picogrid here with solar and a generator because our grid is so badly run. But I'm still a technocrat optimist and think most grids can be run at very large scale well. Am I wrong?

kccqzy 3y ago
During a period of overload, which I interpret to mean the demand exceeding both traditional supply and micro grid supply, there has to be some kind of disconnection to protect the grid. When that disconnection happens, micro grids can at least still power limited number of appliances. Making the grid larger and more extensively shared power decreases the probability of overload but increases the inconvenience when such overload does happen.
bobthepanda 3y ago
Microgrids aren’t exactly new; essential campus type facilities (hospitals, universities, emergency services, military facilities, etc.) have often run their own grids. The major difference is that it is now starting to get affordable for residential. The particular problem it solves is mostly the cascade. You can disconnect to insulate from cascading failure, you can probably restart a microgrid easier since it’s less things to sync, etc. And a cascade can happen for all sorts of reasons, whether that be operator error (2003 Northeast blackout), a natural disaster that hits the wrong way (hurricane/tornado/earthquake/tsunami) or intentional human disaster (Ukraine)
- Kon-Peki 3y ago
  Here is a nice link to a university microgrid explanation [0]. They claim that it allows them to isolate the failure (external or internal) and continue to provide power to the rest of the campus in 1/10 of a second: > Prior to the installation of the microgrid, Illinois Tech experienced three or more power outages each year, at a cost of up to $500,000 annually in restoration expenses, lost productivity, and ruined experiments that often cannot be recovered. [0] https://www.iit.edu/microgrid https://www.iit.edu/microgrid
maliker 3y ago
The US grid is still pretty reliable now, but it's been getting worse and worse. E.g. see some of the recent NERC reports https://www.powermag.com/nerc-warns-of-mounting-reliability-risks-urges-preparation-for-challenging-summer/ https://www.powermag.com/nerc-warns-of-mounting-reliability-...
bluGill 3y ago
> "microgrid also eases the burden on the local utility, because it can disconnect from the larger grid during a period of overload". (Either the microgrid doesn't have enough power or has too much; either way it'd be better to share its resources, no?) Maybe, but probably not. The microgrid is often much more expensive than the regular grid, and provides noisy power that the grid doesn't want. Think diesel generators. Getting those power sources to sync up with the grid is tricky and adds much higher costs to equipment that most places don't need. Some utilities will give you a discount on your power if a few times on their busiest days you agree to disconnect from the main grid and run your backup. These are days when power is most expensive for everyone (the grid is running their more expensive power sources), so that the microgrid is also using expensive power balances out. It is generally only considered worth doing this if you already are thinking about having a microgrid that can work when the local power goes out. However if you are already thinking about installing such a system you can save a lot of money by being able to separate from the regular grid on demand - but it isn't enough to pay for the install and maintenance costs of the microgrid. Now if your microgrid is solar you provide clean power that is easy to sync up with the rest of the grid. To make solar work as a micro grid requires expensive batteries (which need to be maintained and replaced correctly). So for solar installs connecting to the grid makes sense if you can as it is cheaper. Even if you do want the microgrid for power outages, you can get by on a much cheaper system if you don't buy a system large enough to handle your worst case usage (which is a long sequence of cloudy days in winter)
adql 3y ago
Microgrids are probably too small (we want economies of scale here), but it would make a whole lot of sense to move some of the storage near the generation when more and more energy gets shifted to solar. Something like a big battery pack at every substation to handle the local loads when solar is down and help with peaks

kccqzy 3y ago

During a period of overload, which I interpret to mean the demand exceeding both traditional supply and micro grid supply, there has to be some kind of disconnection to protect the grid. When that disconnection happens, micro grids can at least still power limited number of appliances. Making the grid larger and more extensively shared power decreases the probability of overload but increases the inconvenience when such overload does happen.

bobthepanda 3y ago

Microgrids aren’t exactly new; essential campus type facilities (hospitals, universities, emergency services, military facilities, etc.) have often run their own grids. The major difference is that it is now starting to get affordable for residential. The particular problem it solves is mostly the cascade. You can disconnect to insulate from cascading failure, you can probably restart a microgrid easier since it’s less things to sync, etc. And a cascade can happen for all sorts of reasons, whether that be operator error (2003 Northeast blackout), a natural disaster that hits the wrong way (hurricane/tornado/earthquake/tsunami) or intentional human disaster (Ukraine)

Kon-Peki 3y ago
Here is a nice link to a university microgrid explanation [0]. They claim that it allows them to isolate the failure (external or internal) and continue to provide power to the rest of the campus in 1/10 of a second: > Prior to the installation of the microgrid, Illinois Tech experienced three or more power outages each year, at a cost of up to $500,000 annually in restoration expenses, lost productivity, and ruined experiments that often cannot be recovered. [0] https://www.iit.edu/microgrid https://www.iit.edu/microgrid

maliker 3y ago

The US grid is still pretty reliable now, but it's been getting worse and worse. E.g. see some of the recent NERC reports https://www.powermag.com/nerc-warns-of-mounting-reliability-risks-urges-preparation-for-challenging-summer/ https://www.powermag.com/nerc-warns-of-mounting-reliability-...

bluGill 3y ago

> "microgrid also eases the burden on the local utility, because it can disconnect from the larger grid during a period of overload". (Either the microgrid doesn't have enough power or has too much; either way it'd be better to share its resources, no?) Maybe, but probably not. The microgrid is often much more expensive than the regular grid, and provides noisy power that the grid doesn't want. Think diesel generators. Getting those power sources to sync up with the grid is tricky and adds much higher costs to equipment that most places don't need. Some utilities will give you a discount on your power if a few times on their busiest days you agree to disconnect from the main grid and run your backup. These are days when power is most expensive for everyone (the grid is running their more expensive power sources), so that the microgrid is also using expensive power balances out. It is generally only considered worth doing this if you already are thinking about having a microgrid that can work when the local power goes out. However if you are already thinking about installing such a system you can save a lot of money by being able to separate from the regular grid on demand - but it isn't enough to pay for the install and maintenance costs of the microgrid. Now if your microgrid is solar you provide clean power that is easy to sync up with the rest of the grid. To make solar work as a micro grid requires expensive batteries (which need to be maintained and replaced correctly). So for solar installs connecting to the grid makes sense if you can as it is cheaper. Even if you do want the microgrid for power outages, you can get by on a much cheaper system if you don't buy a system large enough to handle your worst case usage (which is a long sequence of cloudy days in winter)

adql 3y ago

Microgrids are probably too small (we want economies of scale here), but it would make a whole lot of sense to move some of the storage near the generation when more and more energy gets shifted to solar. Something like a big battery pack at every substation to handle the local loads when solar is down and help with peaks