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Haha lol. Even in equatorial Africa 48h is not enough. Neither for actual usage, nor for battery life (and no one ever got marketing-leaflet-aka-datasheet-stat

by lstodd 7y ago

Haha lol. Even in equatorial Africa 48h is not enough. Neither for actual usage, nor for battery life (and no one ever got marketing-leaflet-aka-datasheet-stated lifetime out of them batteries). Two years max, and hope either the project dies, or the company dies, or someone steals the batteries. Source: been there maintaning solar offgrid. And then --- geodiversity can only make it worse, never better.

generatorguy 7y ago
Don't know why you are downvoted. I used to run solar powered sites that would have 5 rainy days in a row in which only about 10% of solar generation was delivered during daylight hours. We started with only enough batteries to last overnight and ended up with 10x that. Then we added 33% more when the first set of batteries had a short life due to getting so deeply discharged.
- sunkenvicar 7y ago
  He’s downvoted because he’s bringing on-the-ground facts to a political discussion about solar and wind.
  - atq2119 7y ago
    It may have more to do with the "haha lol", which is an antipattern for rational discussion.
    - sunkenvicar 7y ago
      Humans are irrational. And it’s hard not to laugh at wind and solar. But you are right. I would downvote if I was wrong and laughed at.
- llukas 7y ago
  Is 10x overnight demand close to 48h of average demand? If yes then original post was right.
  - generatorguy 7y ago
    My average day and night load was the same so I went from 12 hours to 120 hours worth of batteries and then could get through the 5 day storm, but with batteries depleted so badly they were essentially damaged. Now we have about 150 hours worth of stored energy for our loads. we added a wind turbine as well which was great since some of the rainy stormy days had lots of wind. I don't understand my original posts parent's comment about (geo) diversity not helping.
Robotbeat 7y ago
FWIW, to arrive at my numbers, I used hourly sun data for a single site for a whole year and then optimized the amount of solar versus storage to minimize costs and prevent total depletion of the batteries while assuming a constant load for the whole year (and then iterating so that the amount of energy in the batteries at the beginning of the year is the same as that at the end). It turns out that even rainy days produce some solar power, which helps stretch the 48 hours of storage. To make it work, it's cheaper to throw away about 2/3rds of your energy than to build 150 hours worth of storage. Some amount of "curtailment" is going to be optimal, and in my case, because solar is so cheap and my starting assumptions allowed no other energy sources, a LOT of curtailment is used. Literally most of the energy is unused. If you ignore massive curtailment as a possibility, then yeah, haha, it's not going to work.

by lstodd 7y ago

generatorguy 7y ago

Don't know why you are downvoted. I used to run solar powered sites that would have 5 rainy days in a row in which only about 10% of solar generation was delivered during daylight hours. We started with only enough batteries to last overnight and ended up with 10x that. Then we added 33% more when the first set of batteries had a short life due to getting so deeply discharged.

sunkenvicar 7y ago
He’s downvoted because he’s bringing on-the-ground facts to a political discussion about solar and wind.
- atq2119 7y ago
  It may have more to do with the "haha lol", which is an antipattern for rational discussion.
  - sunkenvicar 7y ago
    Humans are irrational. And it’s hard not to laugh at wind and solar. But you are right. I would downvote if I was wrong and laughed at.
llukas 7y ago
Is 10x overnight demand close to 48h of average demand? If yes then original post was right.
- generatorguy 7y ago
  My average day and night load was the same so I went from 12 hours to 120 hours worth of batteries and then could get through the 5 day storm, but with batteries depleted so badly they were essentially damaged. Now we have about 150 hours worth of stored energy for our loads. we added a wind turbine as well which was great since some of the rainy stormy days had lots of wind. I don't understand my original posts parent's comment about (geo) diversity not helping.

Robotbeat 7y ago

FWIW, to arrive at my numbers, I used hourly sun data for a single site for a whole year and then optimized the amount of solar versus storage to minimize costs and prevent total depletion of the batteries while assuming a constant load for the whole year (and then iterating so that the amount of energy in the batteries at the beginning of the year is the same as that at the end). It turns out that even rainy days produce some solar power, which helps stretch the 48 hours of storage. To make it work, it's cheaper to throw away about 2/3rds of your energy than to build 150 hours worth of storage. Some amount of "curtailment" is going to be optimal, and in my case, because solar is so cheap and my starting assumptions allowed no other energy sources, a LOT of curtailment is used. Literally most of the energy is unused. If you ignore massive curtailment as a possibility, then yeah, haha, it's not going to work.