4 ms·

Cloud doesn't mean solar stops working - the decrease is 30-60% depending on thickness, but there's still very meaningful generation.

mikeyouse 4y ago
Especially depending on the season - clouds in the summer also typically correspond with a big drop in AC demand, reducing the amount of electricity required. That's why OPs modeling is so interesting, "real" daily data for an entire year is great for this type of planning.
throwawayyyyyy 4y ago
the solar panel's I've used in off-grid applications put out 10% on cloudy days.
zdragnar 4y ago
We get about nine and a half hours of sun in January, assuming no clouds. That leaves around 14-15 hours of no production, assuming there isn't sufficient wind (also often the case in January). Panels operating at 30% capacity for 9 hours cannot be offset by 5 hours worth of storage. It simply isn't enough storage, even if the panels were operating at 100% capacity. Adding more storage really isn't a great solution either; I'm guessing that you would be hard pressed to get 15 hours worth of storage out of 9 hours of sunlight when the hours of darkness start at 4:30 PM, especially if everyone moves to electrical cooking, water heating and clothes drying, which some states are starting to compel. So, the two obvious solutions remain- import stored energy from out of state, or using non-renewables as a base load a few months out of the year. We'll need to pay for burying tonnes of HVDC lines (stringing them up in tornado prone areas isn't a great call, imho) or the expense of more nuclear plants (unpopular and, currently at least, uneconomical) or pulling CO2 out of the air to offset natural gas (also expensive). HVDC lines seem the cheapest, though sourcing the energy will take years of production and inter-state agreements to get to the point where the south is producing (and storing!) enough to send the excess north.
- plantain 4y ago
  You can also over-provision solar and wind to factors well above 100%, and still be more economical than burning fossil fuels.
  - coryrc 4y ago
    The US can't even provision 100% capacity because of BANANA, let alone over-provision.
eldaisfish 4y ago
it also creates another problem - solar generation drop off very quickly when the sun is obscured. going from 100% to 10% or 20% in many cases. Where doe the power come from during these swings? What generation source can ramp up and down at that speed?
- plantain 4y ago
  Synchronous condensers or smart batteries. Australia has deployed a lot of the former to deal with this problem at solar farms.
  - eldaisfish 4y ago
    Australia uses synchronous condensers and batteries for frequency regulation, not energy delivery.
- caf 4y ago
  The grid is always managed such that any single plant or transmission line can trip at any time without causing voltage or frequency collapse. Clouds going over your solar farm is like the plant tripping but not as bad.

mikeyouse 4y ago

Especially depending on the season - clouds in the summer also typically correspond with a big drop in AC demand, reducing the amount of electricity required. That's why OPs modeling is so interesting, "real" daily data for an entire year is great for this type of planning.

throwawayyyyyy 4y ago

the solar panel's I've used in off-grid applications put out 10% on cloudy days.

zdragnar 4y ago

We get about nine and a half hours of sun in January, assuming no clouds. That leaves around 14-15 hours of no production, assuming there isn't sufficient wind (also often the case in January). Panels operating at 30% capacity for 9 hours cannot be offset by 5 hours worth of storage. It simply isn't enough storage, even if the panels were operating at 100% capacity. Adding more storage really isn't a great solution either; I'm guessing that you would be hard pressed to get 15 hours worth of storage out of 9 hours of sunlight when the hours of darkness start at 4:30 PM, especially if everyone moves to electrical cooking, water heating and clothes drying, which some states are starting to compel. So, the two obvious solutions remain- import stored energy from out of state, or using non-renewables as a base load a few months out of the year. We'll need to pay for burying tonnes of HVDC lines (stringing them up in tornado prone areas isn't a great call, imho) or the expense of more nuclear plants (unpopular and, currently at least, uneconomical) or pulling CO2 out of the air to offset natural gas (also expensive). HVDC lines seem the cheapest, though sourcing the energy will take years of production and inter-state agreements to get to the point where the south is producing (and storing!) enough to send the excess north.

plantain 4y ago
You can also over-provision solar and wind to factors well above 100%, and still be more economical than burning fossil fuels.
- coryrc 4y ago
  The US can't even provision 100% capacity because of BANANA, let alone over-provision.

eldaisfish 4y ago

it also creates another problem - solar generation drop off very quickly when the sun is obscured. going from 100% to 10% or 20% in many cases. Where doe the power come from during these swings? What generation source can ramp up and down at that speed?

plantain 4y ago
Synchronous condensers or smart batteries. Australia has deployed a lot of the former to deal with this problem at solar farms.
- eldaisfish 4y ago
  Australia uses synchronous condensers and batteries for frequency regulation, not energy delivery.
caf 4y ago
The grid is always managed such that any single plant or transmission line can trip at any time without causing voltage or frequency collapse. Clouds going over your solar farm is like the plant tripping but not as bad.