7 ms·

"if the government were to take over the Sahara Desert, there would be a shortage of sand in five year" -- Milton Friedman (exaggerating, somewhat) Better to p

"if the government were to take over the Sahara Desert, there would be a shortage of sand in five year" -- Milton Friedman (exaggerating, somewhat) Better to put them on home roofs, and arrange for them to be owned by the homeowners, designed so that the occupants are (literally) empowered when the grid is mismanaged, as in California. On highway medians control is more centralized, and they would require more maintenance and cleaning, which would be more disruptive in that location.

singron 6y ago
Solar panels on home roofs aren't necessarily configured to power the house without the grid. Also you would additionally need batteries and related hardware to have a usable source of power at any time, so unless your house is set up for off-grid solar, you still need the grid to be managed well.
- mysterydip 6y ago
  Found this out in the house we are renting with solar panels installed by landlord. Bright sunny day, someone hits a pole nearby, power goes out. There are two kinds of solar: one that adds to the existing signal from the mains, or one that is self-contained. The second kind is more complicated and therefore expensive. I wasn't aware of the distinction before, but I definitely am now.
  - yellow_lead 6y ago
    Aren't there setups that can do both as well? i.e charge battery first and send excess to the grid?
    - apcragg 6y ago
      Sure but they are more expensive. You need a rock solid controller with beefy and redundant electronics to make sure you're never going to be connected to the grid when you shouldn't be.
    - c22 6y ago
      Yes, but any setup that's capable of feeding power back to the grid requires costly safety interlocks to allow linemen to make repairs at the street without your house unexpectedly energizing the line. Some jurisdictions just outright disallow it.
    - qayxc 6y ago
      The setups have to be separate (e.g. different outlets for mains and solar) to protect the grid. Even a small home solar installation puts out enough power to easily kill unsuspecting maintenance personell working on the grid, for example. So the utility company has to have 100% control over he mains at all time for safety reasons (i.e. your meter must never run backwards). If they cut the power (e.g. for maintenance or repairs), no one must be able to feed power into the grid. That's why even if you have a battery, said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time.
      - nitrogen 6y ago
        Meters run backward intentionally when selling solar back to the utility. You need a switching system that will isolate immediately if the grid fails, and resync with the grid AC before reconnecting, if you want to be able to operate on and off the grid.
        qayxc 6y ago
        That depends on the country then - in my country, you need to install a secondary meter instead.
      - danans 6y ago
        > So the utility company has to have 100% control over he mains at all time for safety reasons This is controlled independently by the solar inverters's software, not the utility via any sort of signal. That software is mandated by regulation as you say for the safety of line workers. Recent batteries allow for an "islanding" mode, which allows continued backup power delivery to the house during a grid outage but cuts off the grid connection. > your meter must never run backwards ... during a grid outage. During normal operation it's fine for it to run backwards. That's what net metering quantifies. > said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time. I think this is a technical limitation, since it would require a current divider and 2 inverters, which is a level of complexity not worth it for the application.
Retric 6y ago
Rooftop photovoltaic is currently more expensive, less efficient, and surprisingly dangerous to install. Solar thermal designs actually benefit from being on rooftops. As to dust, economies of scale make a huge difference. It’s rarely worth it, but using a farm truck to spray water across miles of panels is much more efficient than tens of thousands of homeowners doing the same.
- brightball 6y ago
  First I’ve heard of solar thermal. Any good links?
  - discreteevent 6y ago
    Goes back years. Simplest form is a squiggly pipe behind a pane of glass. Water runs slowly through the pipe and heats up.
  - onionisafruit 6y ago
    Think rooftop solar water heaters.
- Nextgrid 6y ago
  What dangers are we talking about? Do solar panels add extra danger compared to just normal roof maintenance work?
  - Retric 6y ago
    To be clear their not that dangerous, but we are still talking extra deaths and accidents. Mostly from increased amount of time people spend on residential roofs. Roofing is about 30 deaths per 100,000 full time workers which is about double the average rate for construction. Currently instillation is the primary, but not only risk. You also get electrical accidents and in rare cases fires. Plus an increased tendency for people to go onto a roof to check them out and or clean them etc. And some extra roof maintenance due to leaks from improper installation etc. Personally, I don’t think it’s a major deal at the individual level. However, I thik it should be considered in terms of public policy.
danans 6y ago
> Better to put them on home roofs, and arrange for them to be owned by the homeowners, designed so that the occupants are (literally) empowered when the grid is mismanaged, as in California. It turns out that the same California that you criticize now requires solar on newly built homes, just as you recommend, and much to the chagrin of people who feel like the state government is impinging on individuals' rights to build however they please.
pwagland 6y ago
> if the government were to take over the Sahara Desert, there would be a shortage of sand in five year" -- Milton Friedman (exaggerating, somewhat) I know that this is meant to be a humorous comment, however, desert sand is not really usable for most things that we want sand for, for example, it is not suitable for concrete, since it is too fine. (https://petroleumservicecompany.com/blog/could-desert-sand-be-used-to-make-concrete/ https://petroleumservicecompany.com/blog/could-desert-sand-b...) This is why, desire being in a desert, Dubai imports its sand! (https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why https://www.bbc.com/worklife/article/20160502-even-desert-ci...)
dehrmann 6y ago
It's most efficient to put the panels in a centralized location with high amounts of sunlight on mounts that track the sun. You get significantly higher yield because of the tracking and the location, and maintenance is cheaper because it's centralized. The fact that you see far more home installations than farms means farms aren't economically viable, neither is home PV without subsidies, but people buy into the "empowerment" fantasy.
- masklinn 6y ago
  The balance of tracking mounts is not trivial. They increase efficiency a lot (up to 40% for dual-axis trackers) but they also decrease ground a lot coverage, they increase cost of installation and cost of ownership, and they decrease availability.
  - sroussey 6y ago
    It balances out to the positive. See https://heliogen.com/ https://heliogen.com/
    - masklinn 6y ago
      That's a heliostat system, not a solar panel system. Both involve the sun but they do so very differently. It's also a company which wants to sell heliostats, they're not going to tell you it sucks.
- nxc18 6y ago
  Empowerment isn’t really a fantasy if there are rolling blackouts but your own power is still on. Sadly, not a hypothetical in California. Im thinking just from a national security/redundancy/risk reduction standpoint it makes sense to move more generation closer to demand. There are lots of single points of failure in our power grid currently. Edit: this is assuming the solar setup is designed to enable use when power is out; I assume homeowners who care about empowerment would make that investment, but you know what they say about assuming.
  - 6y ago
p1mrx 6y ago
> the occupants are (literally) empowered when the grid is mismanaged, as in California. The California blackouts started around sunset, when solar dropped off the grid. Building more solar without an appropriate amount of storage just makes the problem worse.

singron 6y ago

Solar panels on home roofs aren't necessarily configured to power the house without the grid. Also you would additionally need batteries and related hardware to have a usable source of power at any time, so unless your house is set up for off-grid solar, you still need the grid to be managed well.

mysterydip 6y ago
Found this out in the house we are renting with solar panels installed by landlord. Bright sunny day, someone hits a pole nearby, power goes out. There are two kinds of solar: one that adds to the existing signal from the mains, or one that is self-contained. The second kind is more complicated and therefore expensive. I wasn't aware of the distinction before, but I definitely am now.
- yellow_lead 6y ago
  Aren't there setups that can do both as well? i.e charge battery first and send excess to the grid?
  - apcragg 6y ago
    Sure but they are more expensive. You need a rock solid controller with beefy and redundant electronics to make sure you're never going to be connected to the grid when you shouldn't be.
  - c22 6y ago
    Yes, but any setup that's capable of feeding power back to the grid requires costly safety interlocks to allow linemen to make repairs at the street without your house unexpectedly energizing the line. Some jurisdictions just outright disallow it.
  - qayxc 6y ago
    The setups have to be separate (e.g. different outlets for mains and solar) to protect the grid. Even a small home solar installation puts out enough power to easily kill unsuspecting maintenance personell working on the grid, for example. So the utility company has to have 100% control over he mains at all time for safety reasons (i.e. your meter must never run backwards). If they cut the power (e.g. for maintenance or repairs), no one must be able to feed power into the grid. That's why even if you have a battery, said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time.
    - nitrogen 6y ago
      Meters run backward intentionally when selling solar back to the utility. You need a switching system that will isolate immediately if the grid fails, and resync with the grid AC before reconnecting, if you want to be able to operate on and off the grid.
      - qayxc 6y ago
        That depends on the country then - in my country, you need to install a secondary meter instead.
    - danans 6y ago
      > So the utility company has to have 100% control over he mains at all time for safety reasons This is controlled independently by the solar inverters's software, not the utility via any sort of signal. That software is mandated by regulation as you say for the safety of line workers. Recent batteries allow for an "islanding" mode, which allows continued backup power delivery to the house during a grid outage but cuts off the grid connection. > your meter must never run backwards ... during a grid outage. During normal operation it's fine for it to run backwards. That's what net metering quantifies. > said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time. I think this is a technical limitation, since it would require a current divider and 2 inverters, which is a level of complexity not worth it for the application.

Retric 6y ago

Rooftop photovoltaic is currently more expensive, less efficient, and surprisingly dangerous to install. Solar thermal designs actually benefit from being on rooftops. As to dust, economies of scale make a huge difference. It’s rarely worth it, but using a farm truck to spray water across miles of panels is much more efficient than tens of thousands of homeowners doing the same.

brightball 6y ago
First I’ve heard of solar thermal. Any good links?
- discreteevent 6y ago
  Goes back years. Simplest form is a squiggly pipe behind a pane of glass. Water runs slowly through the pipe and heats up.
- onionisafruit 6y ago
  Think rooftop solar water heaters.
Nextgrid 6y ago
What dangers are we talking about? Do solar panels add extra danger compared to just normal roof maintenance work?
- Retric 6y ago
  To be clear their not that dangerous, but we are still talking extra deaths and accidents. Mostly from increased amount of time people spend on residential roofs. Roofing is about 30 deaths per 100,000 full time workers which is about double the average rate for construction. Currently instillation is the primary, but not only risk. You also get electrical accidents and in rare cases fires. Plus an increased tendency for people to go onto a roof to check them out and or clean them etc. And some extra roof maintenance due to leaks from improper installation etc. Personally, I don’t think it’s a major deal at the individual level. However, I thik it should be considered in terms of public policy.

danans 6y ago

> Better to put them on home roofs, and arrange for them to be owned by the homeowners, designed so that the occupants are (literally) empowered when the grid is mismanaged, as in California. It turns out that the same California that you criticize now requires solar on newly built homes, just as you recommend, and much to the chagrin of people who feel like the state government is impinging on individuals' rights to build however they please.

pwagland 6y ago

> if the government were to take over the Sahara Desert, there would be a shortage of sand in five year" -- Milton Friedman (exaggerating, somewhat) I know that this is meant to be a humorous comment, however, desert sand is not really usable for most things that we want sand for, for example, it is not suitable for concrete, since it is too fine. (https://petroleumservicecompany.com/blog/could-desert-sand-be-used-to-make-concrete/ https://petroleumservicecompany.com/blog/could-desert-sand-b...) This is why, desire being in a desert, Dubai imports its sand! (https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why https://www.bbc.com/worklife/article/20160502-even-desert-ci...)

dehrmann 6y ago

It's most efficient to put the panels in a centralized location with high amounts of sunlight on mounts that track the sun. You get significantly higher yield because of the tracking and the location, and maintenance is cheaper because it's centralized. The fact that you see far more home installations than farms means farms aren't economically viable, neither is home PV without subsidies, but people buy into the "empowerment" fantasy.

masklinn 6y ago
The balance of tracking mounts is not trivial. They increase efficiency a lot (up to 40% for dual-axis trackers) but they also decrease ground a lot coverage, they increase cost of installation and cost of ownership, and they decrease availability.
- sroussey 6y ago
  It balances out to the positive. See https://heliogen.com/ https://heliogen.com/
  - masklinn 6y ago
    That's a heliostat system, not a solar panel system. Both involve the sun but they do so very differently. It's also a company which wants to sell heliostats, they're not going to tell you it sucks.
nxc18 6y ago
Empowerment isn’t really a fantasy if there are rolling blackouts but your own power is still on. Sadly, not a hypothetical in California. Im thinking just from a national security/redundancy/risk reduction standpoint it makes sense to move more generation closer to demand. There are lots of single points of failure in our power grid currently. Edit: this is assuming the solar setup is designed to enable use when power is out; I assume homeowners who care about empowerment would make that investment, but you know what they say about assuming.
- 6y ago

p1mrx 6y ago

> the occupants are (literally) empowered when the grid is mismanaged, as in California. The California blackouts started around sunset, when solar dropped off the grid. Building more solar without an appropriate amount of storage just makes the problem worse.