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Thread: Solar panels on your roof vs Giant solar farms?

  1. #1
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    Solar panels on your roof vs Giant solar farms?

    Hi all,

    Been reading discussions here about hydrogen vehicles etc and been thinking about getting home solar panels, and switching to electric car.

    I was wondering how inefficient it is for individuals to install solar panels on our own roofs?

    Surely the cost of installation maintenance battery etc including replacement / recycling when panels superseded must be a lot cheaper if you have a commercial sized solar farm?

    Are there not massive ‘economies of scale’ to be had?

    Or do you gain efficiency with power generated close to use? Ie power loss with transmission ??

    Am i better off just paying more for “green power”??

    Thx in advance.
    Last edited by plant; 2019-Oct-30 at 07:10 AM.
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    It doesn't have to be "or".
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  3. #3
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    You really need to get an installation estimate, projected average power generation, and estimated system lifetime and compare to your local electricity prices to see which is more economical. Power generation and system size will depend on how much sun you get in your location and your individual needs.

    Most people opt for a grid tie rather than backup batteries, unless they live off grid. Batteries add significantly to cost, can require regular maintenance (depending on technology) and arenít that important on the grid unless your power goes out frequently or if your utility has a poor buy back policy. Battery lifetime also depends on battery technology. That said, cost on batteries are starting to come down so are becoming more popular for backup. PV panels last a long time, and usually donít require much maintenance.

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    OK but I wonder what would produce the cheapest/ most environmentally friendly power generation in suburbia:

    Scenario 1:
    1000 households with 'real world' outputs from their own individual solar panels on roofs... given that not all households will have ideal roof alignments.

    Scenario 2:
    A large solar farm in the suburb with 1000 x the solar panels installed at ground level (rotating with sun) supplying 1000 households. This would need to include cost of (leasing) land I assume.
    Last edited by plant; 2019-Oct-30 at 07:45 AM.
    "It's only a model....?" :-)
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    I would say that each scenario has its merits and pitfalls.

    By hosting your own generation system (no grid tie in) you are independent of external social factors and can effectively budget your energy use.
    However you would be limited by your generation capacity and be liable for all maintenance costs etc.

    By using a centralised generation facility you would have access to a larger reserve of power possibly better situated for maximally capturing sunlight.
    However, you would be subject to similar pitfalls to the conventional grid whereby a problem at the plant means you lose all power. Also, some consumers will use as much power as they can get, causing shortages for others. It would be difficult to budget your own use reliably. There may be efficiency losses over the infrastructure as the transmission lines would be longer.

    Speaking as someone who has a 4kw installation on the roof, with grid tie in but no battery, I would suggest a mixture of both scenarios. A central facility providing more efficient generation together with adequate home generation to provide consistent supply. I would personally add a battery backup to the home installation, but still allow a grid tie in to allow excess generation capacity to be used by others.

    We recently had the power go out for some grid maintenance and I was infuriated by our systems inability to supply power because of the safety interlock that is mandatory to prevent power feeding into the grid while maintenance is carried out. There are simple systems available that can isolate home generation from the grid when the grid goes down, but, I guess for political reasons (we get a subsidised generation rate) these systems were not installed.

    I can tell you from experience that living in the Northern Hemisphere, specifically in the UK, does not make for consistent year round capacity. Unless we move to a low voltage set up in the home, there is simply not enough sun during the winter to be reliable at even reduced usage.


    good-solar.png

    poor-solar.png
    Last edited by headrush; 2019-Oct-30 at 10:29 AM.

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    Additional complications:
    1) What happens when the roof of a house with solar panels needs to be re-shingled?
    2) Does hail damage solar panels? If so, a solar farm is more likely to be knocked out by a hailstorm than a widely distributed set of solar panels.

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    Quote Originally Posted by headrush View Post
    We recently had the power go out for some grid maintenance and I was infuriated by our systems inability to supply power because of the safety interlock that is mandatory to prevent power feeding into the grid while maintenance is carried out. There are simple systems available that can isolate home generation from the grid when the grid goes down, but, I guess for political reasons (we get a subsidised generation rate) these systems were not installed.
    Usually it is just cost and practicality. You would need to add a battery, typically for a few thousand dollars extra, to the system. Solar can be too variable to use it directly with home appliances.

    What you describe sounds like a standard grid tie setup.

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    Quote Originally Posted by Van Rijn View Post
    Usually it is just cost and practicality. You would need to add a battery, typically for a few thousand dollars extra, to the system. Solar can be too variable to use it directly with home appliances.

    What you describe sounds like a standard grid tie setup.
    I agree partly. My point about the subsidised rate is due to the fact that I don't get paid according to what I export, but according to what I generate. With a battery set up as standard it would be trivial to never export any power and yet still receive payment as if I did. It was the scheme set up by the government so I got what was being sold at the time. I am exploring the possibilities of adding battery backup and am quite prepared to forgo any export earnings simply to be fully in control of the situation. I would still retain the grid tie in however.

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    Nature always diversifies, there are 10's of millions of species with billions of genetic variations. Having power generation on roofs and solar farms will diversify and make the system more stable. When you see or, change it to and.
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    Quote Originally Posted by plant View Post
    Hi all,

    Been reading discussions here about hydrogen vehicles etc and been thinking about getting home solar panels, and switching to electric car.

    I was wondering how inefficient it is for individuals to install solar panels on our own roofs?

    Surely the cost of installation maintenance battery etc including replacement / recycling when panels superseded must be a lot cheaper if you have a commercial sized solar farm?

    Are there not massive ‘economies of scale’ to be had?

    Or do you gain efficiency with power generated close to use? Ie power loss with transmission ??

    Am i better off just paying more for “green power”??

    Thx in advance.
    There are pros and cos for both. Decentralized power has economy of scale, but localized power means less reliance on a poorly/unevenly maintained power grid, and you know what source your energy comes from.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  11. #11
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    When i visited family outside copenhagen i was suuprised to learn that the houses were warmed by hot water pipes that fed in from municipal heating stations. It seemed odd and inefficient to the Danes that each house here should have its own heating system!
    "It's only a model....?" :-)
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  12. #12
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    Quote Originally Posted by plant View Post
    When i visited family outside copenhagen i was suuprised to learn that the houses were warmed by hot water pipes that fed in from municipal heating stations. It seemed odd and inefficient to the Danes that each house here should have its own heating system!
    There are places in the US that get the heat for multiple buildings from steam pipes and the like, where buildings are close together.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  13. #13
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    Quote Originally Posted by plant View Post
    OK but I wonder what would produce the cheapest/ most environmentally friendly power generation in suburbia:

    Scenario 1:
    1000 households with 'real world' outputs from their own individual solar panels on roofs... given that not all households will have ideal roof alignments.

    Scenario 2:
    A large solar farm in the suburb with 1000 x the solar panels installed at ground level (rotating with sun) supplying 1000 households. This would need to include cost of (leasing) land I assume.
    Except for the cost of the land, I think clearly scenario 2 is better if you want cheaper and more environmentally friendly. A large array can better optimize efficiencies and it would require less control/distribution hardware and electronics. There is no need, of course, to put the array in a suburb; placing it out of town near existing power transmission lines would be cheaper.

  14. #14
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    Also, industries.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by plant View Post
    When i visited family outside copenhagen i was suuprised to learn that the houses were warmed by hot water pipes that fed in from municipal heating stations. It seemed odd and inefficient to the Danes that each house here should have its own heating system!
    I read a recent article that mentions such a system. Here in the UK 80% of home heating is done with natural gas which means the emissions are on a par with transportation. Unfortunately we don't have enough industry distributed around the country to make the shared heat system viable.

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    Quote Originally Posted by Noclevername View Post
    Also, industries.
    I meant, industries may require larger amounts of power than a rooftop array might provide.
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  17. #17
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    Quote Originally Posted by plant View Post
    When i visited family outside copenhagen i was suuprised to learn that the houses were warmed by hot water pipes that fed in from municipal heating stations. It seemed odd and inefficient to the Danes that each house here should have its own heating system!
    When I attended the University of Virginia 50 years ago, the buildings were heated by steam from a coal-fired heating plant. It was not centrally located, but rather was at one corner of the campus next to the railroad tracks for ease of coal delivery. My dormitory room was on the opposite side of the campus, over a mile away. That plant has since been upgraded to burn cleaner and to have flex fuel capability for using coal, oil or gas.

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    Quote Originally Posted by Hornblower View Post
    When I attended the University of Virginia 50 years ago, the buildings were heated by steam from a coal-fired heating plant. It was not centrally located, but rather was at one corner of the campus next to the railroad tracks for ease of coal delivery. My dormitory room was on the opposite side of the campus, over a mile away. That plant has since been upgraded to burn cleaner and to have flex fuel capability for using coal, oil or gas.
    My school at Stevens Point, Wisconsin was the same.
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  19. #19
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    One of the big pro's on rooftop is that there is almost no power lost during distribution.

    https://electrical-engineering-porta...ission-lines-1

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    The large solar farms can also be a problem for habitat destruction in some areas. Some of the proposed farms in Florida are to be sited in sensitive habitats - because that's all that is left in some places to build large expanses of arrays. Rooftop solar's benefit is that much of it can be put on already disturbed and developed areas.

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    Quote Originally Posted by tashirosgt View Post
    Additional complications:
    1) What happens when the roof of a house with solar panels needs to be re-shingled?
    2) Does hail damage solar panels? If so, a solar farm is more likely to be knocked out by a hailstorm than a widely distributed set of solar panels.
    1) You take the panels off.

    2) Yes, but "damage" doesn't necessarily mean "render unserviceable," and panels can be designed to have some immunity to damage from hail (or people throwing rocks, shooting at them, or hitting them with baseball bats).
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  22. #22
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    There certainly is an economy of scale to the solar farm. The farm will have more efficient conversion, better maintenance, less obstruction by trees and other buildings, better panel orientation (and possibly sun-tracking panels), etc. They're also safely isolated from your home: solar panels can't be turned off and roof mounted arrays can pose an electrical hazard.

    However, roof-mounted solar panels don't take up land that could be put to other productive uses or just left in its natural state, could be integrated into a battery backup system for individual homes (particularly useful in areas with unreliable power), can compensate for the lower overall efficiency by reducing transmission losses, etc. And of course, you can own them, and only need to pay for maintenance, with the possibility of selling excess power to pay for some or all of that. And there's options like Tesla's Solar Roof: https://www.tesla.com/solarroof

    So, there's benefits and tradeoffs for both.

  23. #23
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    Quote Originally Posted by LaurieAG View Post
    One of the big pro's on rooftop is that there is almost no power lost during distribution.

    https://electrical-engineering-porta...ission-lines-1
    That looks like a lot of reasons for power loss. Distribution looks like it is very complicated.
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