3 ms·

Consume less, on paper, is easy, in practice it depend. Personally I have a small f.v. (south France) with battery backup, in sunny days almost all the year I h

by kkfx 5y ago

Consume less, on paper, is easy, in practice it depend. Personally I have a small f.v. (south France) with battery backup, in sunny days almost all the year I have enough energy to waste it. In other days I need energy as anyone else. No battery can compensate. Doubling my battery capacity (witch is NOT cheat at all) just means having more energy from one sunny day to another. Survive just one day without sun means 4* the battery and I have to count the fact that does not have a reasonably good lifespan for the price. Essentially: it's unfeasible. And I'm talking about a "A-class" (BBC) house, so with very little energy needs compared to old ones.

Retric 5y ago
To go fully off grid you would need more solar and batteries rather than just more batteries alone. Panels produce some energy on cloudy days, suppose your deficit drops from -80% to -40%, now the battery which would last you 1 day lasts you 2 days, double your batteries as well and 2 days becomes 4 days. More critically many days that are moderately overcast go from a net loss to a net gain. It’s just an optimization problem based on your local climate, the cost of equipment, and your willingness to reduce remain after multiple cloudy days.
- kkfx 5y ago
  So did you think it's practical buy a soccer stadium well-exposed south space and spend the money of a supercar just to be able to munge few more W in cloudy days? Of course also counting snowy days when you still get 0 output + you eventually need to clean-up your panels? Beside the willingness and the price, who many in the world can do something similar? Especially in EU where most people live in dense city, so apartments?
  - Retric 5y ago
    Grid solar is more efficient in general and much safer to install than rooftop solar, some people simply dislike connecting to the electric grid for various reasons. Anyway, you don’t need to face south if you just want more energy on cloudy days. As to more panels, it’s a question of how much you want to be off grid and how much energy you need. Normal solar installs cover a small fraction of the roof.
    - kkfx 5y ago
      Having a east-west roof and a large south area my panels are on ground, facing south, I'm connected to the grid and have no plan not to, but my point is that in mere kWh/month in most month I can say I produce more than I consume, witch is numerically true and practically false since I produce few hours a day much more than my needs and I still have to cover the rest. My point is at national level: how can a nation imaging energy independence with f.v. and eolic. IMVHO that's simply an illusion. Some say "coupled to the nuclear", but since the network need to be always powered and nuclear better produce at a steady constant peace f.v. et al can just be local small-scale backups. Something else? Well, maybe a country like Norway can with wind+hydro satisfy it's needs, but most countries can't, or essentially: I see nothing that can really work on scale beside a hypothetical global superconductive grid, or nuclear fusion etc witch actually are more dream with something behind then tangible things. Personally I can even recharge an e.v. since I do normally not need much car usage except for holidays/weekends etc, but if I need medical assistance I do not want to accept "we have drained battery, sorry" or at the hospital "we can't make surgery due to lack of energy today" and similarly when shopping for cheese I expect to find it, not to need more tentatives to buy it until I fond etc. Such "lux" witch are actually normal life in the western world I can see how can exists with the Green New Deal, simply. I know oil&gas are finite resources, I know pollution is bad, but still fail to se a real solution that can scale behind mass genocides, middle-age revivals etc...
      - Retric 5y ago
        This gets really complicated if you want to understand solar at scale going forward. First European countries don’t operate reliable and independent electric grids, it’s always been more cost effective to average our demand across huge areas. At the same time, at an organizational and technical level it’s useful to split the grid into multiple different chunks that all connect with each other to various degrees. Even the US shares it’s electric grid with Canada while connecting to the Mexican grid. https://en.wikipedia.org/wiki/Eastern_Interconnection https://en.wikipedia.org/wiki/Eastern_Interconnection A country may hit say 99% reliably on it’s own but 99.9X% when part of a larger grid. Next reaching 99.9+% reliability requires significant redundancy no matter the scale. Normally you subsidize some percentage of generation so it’s there when you need it rather than trying to depend on second by second spot prices to handle extreme outlier events. In that context solar is really vastly more reliable with a little extra capacity and a great deal of geographic separation between generation. Many US examples have 30+% capacity factors which is ~90% of their theoretical maximums ~(1/pi), but importing power east/west time shifts generation. Similarly aiming panels east or west trades off total generation to get more power either earlier or later. All of the above doesn’t help at 2AM, but it still means your personal experience with solar doesn’t map very well to grid scale generation. California for example already sees 5% of all solar power being wasted, but because power is more valuable in the morning and evening than in the middle of the day that excess isn’t a big deal. Sure, if you can use 100% of PV output then solar costs ~2c/kWh in a good location, but that number is largely irrelevant as you notice. The question is how much excess capacity do you add. If you can only use 50% of the output your paying 4c/kWh which is roughly the cost of just the natural gas needed to operate a natural gas power plant averaged over multiple years. Put another way if you own a natural gas power plant you currently save money installing PV simply to offset the cost of natural gas though that’s likely to change as PV gets more ubiquitous. The question then becomes if you can meet say 60% of total monthly demand with solar but doing so means you have a lot of excess capacity should you then install batteries to cover some of the rest with batteries? Looking at how prices spike at some times of the day the answer seems to be yes, it’s only a niche but it’s still viable today. Which then brings the question of do you eventually build solar simply to charge batteries? We aren’t there yet, but with the way battery prices have been dropping that’s going to happen. (And when it does most other forms of generation get serious competition.) Of course solar + batteries doesn’t operate in a vacuum. Hydroelectric generation is ~7% of total electricity generation in most areas, but while it basically provides a fixed amount of Wh per month it has a great deal of flexibility when within the month to generate power. This combined with weather forecasting caps how much battery power you want to set aside for unusual days as it’s cheaper to store energy in existing dams and tap that when needed. Hydro in in many ways the inverse of PV. Similarly wind is it’s own thing and complements solar + batteries quite well. Now Nuclear seems like a good fit on the surface but costs go up as capacity factor drops. In this model it’s really competing with Hydro and at vastly higher prices because most of the time it’s output is worth very little. Japan might subsidize nuclear because it’s grid is operating individually and so has more expensive and less reliable solar power. Similarly, it might be heavily subsidized for political reasons in some counties, but in general it’s unlikely to make up a large fraction of total generation long term.
patall 5y ago
But you (and I) could have a seasonal thermal energy storage, cooling the solar array in summer and removing the need of external heating in winter. Doesn't work for power, but does for heat.
- kkfx 5y ago
  I do something far shorter: heating water in the sunny days to have it in the cloudy ones, but that's definitively far from sufficient for heating the entire house and to scale at the entire house needs well... It's cheaper run on grid electricity, even these days.
thow-58d4e8b 5y ago
This is where the narrative about personal responsibility falls apart - when it comes to electricity and energy, everything is better at scale, and it's not even close. All the meaningful action is to be done on state, corporate and industrial level, individuals are a rounding error Even with solar, where one might reasonably think the transportation costs would favor decentralized deployment - no, utility-scale deployments benefit dual axis tracking, amortization of fixed costs, integration with energy storage and economies of scale. We would all be better off as shareholders of utility solar than deploying rooftop + batteries, but that takes away the bragging rights
- zbrozek 5y ago
  My utility charges about $0.30 per KWh right now and raises rates at about 4x inflation. Putting up solar panels is a no-brainer. The array I put up pays for itself in less than 18 months. Until those economies of scale manifest as cheap electricity for consumers, the drive towards local generation is inevitable.
- pfdietz 5y ago
  I think utility scale PV is more using single axis tracking, not dual axis.
  - kkfx 5y ago
    IMVHO depend on where you are, for me no tracking at all means I still have more than enough electricity when the Sun shine, but I do consume it 24/7/365, regardless of the meteo....

by kkfx 5y ago

Retric 5y ago

To go fully off grid you would need more solar and batteries rather than just more batteries alone. Panels produce some energy on cloudy days, suppose your deficit drops from -80% to -40%, now the battery which would last you 1 day lasts you 2 days, double your batteries as well and 2 days becomes 4 days. More critically many days that are moderately overcast go from a net loss to a net gain. It’s just an optimization problem based on your local climate, the cost of equipment, and your willingness to reduce remain after multiple cloudy days.

kkfx 5y ago
So did you think it's practical buy a soccer stadium well-exposed south space and spend the money of a supercar just to be able to munge few more W in cloudy days? Of course also counting snowy days when you still get 0 output + you eventually need to clean-up your panels? Beside the willingness and the price, who many in the world can do something similar? Especially in EU where most people live in dense city, so apartments?
- Retric 5y ago
  Grid solar is more efficient in general and much safer to install than rooftop solar, some people simply dislike connecting to the electric grid for various reasons. Anyway, you don’t need to face south if you just want more energy on cloudy days. As to more panels, it’s a question of how much you want to be off grid and how much energy you need. Normal solar installs cover a small fraction of the roof.
  - kkfx 5y ago
    Having a east-west roof and a large south area my panels are on ground, facing south, I'm connected to the grid and have no plan not to, but my point is that in mere kWh/month in most month I can say I produce more than I consume, witch is numerically true and practically false since I produce few hours a day much more than my needs and I still have to cover the rest. My point is at national level: how can a nation imaging energy independence with f.v. and eolic. IMVHO that's simply an illusion. Some say "coupled to the nuclear", but since the network need to be always powered and nuclear better produce at a steady constant peace f.v. et al can just be local small-scale backups. Something else? Well, maybe a country like Norway can with wind+hydro satisfy it's needs, but most countries can't, or essentially: I see nothing that can really work on scale beside a hypothetical global superconductive grid, or nuclear fusion etc witch actually are more dream with something behind then tangible things. Personally I can even recharge an e.v. since I do normally not need much car usage except for holidays/weekends etc, but if I need medical assistance I do not want to accept "we have drained battery, sorry" or at the hospital "we can't make surgery due to lack of energy today" and similarly when shopping for cheese I expect to find it, not to need more tentatives to buy it until I fond etc. Such "lux" witch are actually normal life in the western world I can see how can exists with the Green New Deal, simply. I know oil&gas are finite resources, I know pollution is bad, but still fail to se a real solution that can scale behind mass genocides, middle-age revivals etc...
    - Retric 5y ago
      This gets really complicated if you want to understand solar at scale going forward. First European countries don’t operate reliable and independent electric grids, it’s always been more cost effective to average our demand across huge areas. At the same time, at an organizational and technical level it’s useful to split the grid into multiple different chunks that all connect with each other to various degrees. Even the US shares it’s electric grid with Canada while connecting to the Mexican grid. https://en.wikipedia.org/wiki/Eastern_Interconnection https://en.wikipedia.org/wiki/Eastern_Interconnection A country may hit say 99% reliably on it’s own but 99.9X% when part of a larger grid. Next reaching 99.9+% reliability requires significant redundancy no matter the scale. Normally you subsidize some percentage of generation so it’s there when you need it rather than trying to depend on second by second spot prices to handle extreme outlier events. In that context solar is really vastly more reliable with a little extra capacity and a great deal of geographic separation between generation. Many US examples have 30+% capacity factors which is ~90% of their theoretical maximums ~(1/pi), but importing power east/west time shifts generation. Similarly aiming panels east or west trades off total generation to get more power either earlier or later. All of the above doesn’t help at 2AM, but it still means your personal experience with solar doesn’t map very well to grid scale generation. California for example already sees 5% of all solar power being wasted, but because power is more valuable in the morning and evening than in the middle of the day that excess isn’t a big deal. Sure, if you can use 100% of PV output then solar costs ~2c/kWh in a good location, but that number is largely irrelevant as you notice. The question is how much excess capacity do you add. If you can only use 50% of the output your paying 4c/kWh which is roughly the cost of just the natural gas needed to operate a natural gas power plant averaged over multiple years. Put another way if you own a natural gas power plant you currently save money installing PV simply to offset the cost of natural gas though that’s likely to change as PV gets more ubiquitous. The question then becomes if you can meet say 60% of total monthly demand with solar but doing so means you have a lot of excess capacity should you then install batteries to cover some of the rest with batteries? Looking at how prices spike at some times of the day the answer seems to be yes, it’s only a niche but it’s still viable today. Which then brings the question of do you eventually build solar simply to charge batteries? We aren’t there yet, but with the way battery prices have been dropping that’s going to happen. (And when it does most other forms of generation get serious competition.) Of course solar + batteries doesn’t operate in a vacuum. Hydroelectric generation is ~7% of total electricity generation in most areas, but while it basically provides a fixed amount of Wh per month it has a great deal of flexibility when within the month to generate power. This combined with weather forecasting caps how much battery power you want to set aside for unusual days as it’s cheaper to store energy in existing dams and tap that when needed. Hydro in in many ways the inverse of PV. Similarly wind is it’s own thing and complements solar + batteries quite well. Now Nuclear seems like a good fit on the surface but costs go up as capacity factor drops. In this model it’s really competing with Hydro and at vastly higher prices because most of the time it’s output is worth very little. Japan might subsidize nuclear because it’s grid is operating individually and so has more expensive and less reliable solar power. Similarly, it might be heavily subsidized for political reasons in some counties, but in general it’s unlikely to make up a large fraction of total generation long term.

patall 5y ago

But you (and I) could have a seasonal thermal energy storage, cooling the solar array in summer and removing the need of external heating in winter. Doesn't work for power, but does for heat.

kkfx 5y ago
I do something far shorter: heating water in the sunny days to have it in the cloudy ones, but that's definitively far from sufficient for heating the entire house and to scale at the entire house needs well... It's cheaper run on grid electricity, even these days.

thow-58d4e8b 5y ago

This is where the narrative about personal responsibility falls apart - when it comes to electricity and energy, everything is better at scale, and it's not even close. All the meaningful action is to be done on state, corporate and industrial level, individuals are a rounding error Even with solar, where one might reasonably think the transportation costs would favor decentralized deployment - no, utility-scale deployments benefit dual axis tracking, amortization of fixed costs, integration with energy storage and economies of scale. We would all be better off as shareholders of utility solar than deploying rooftop + batteries, but that takes away the bragging rights

zbrozek 5y ago
My utility charges about $0.30 per KWh right now and raises rates at about 4x inflation. Putting up solar panels is a no-brainer. The array I put up pays for itself in less than 18 months. Until those economies of scale manifest as cheap electricity for consumers, the drive towards local generation is inevitable.
pfdietz 5y ago
I think utility scale PV is more using single axis tracking, not dual axis.
- kkfx 5y ago
  IMVHO depend on where you are, for me no tracking at all means I still have more than enough electricity when the Sun shine, but I do consume it 24/7/365, regardless of the meteo....