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Summary:

Utilities plan to use solar power from both the massive solar plants that are being built in the California Mojave desert, as well as large scale distributed rooftop solar projects, like the one Southern California Edison is planning. So which technology is better? Centralized solar systems […]

Utilities plan to use solar power from both the massive solar plants that are being built in the California Mojave desert, as well as large scale distributed rooftop solar projects, like the one Southern California Edison is planning. So which technology is better? Centralized solar systems that use the sun’s heat to generate electricity, or hundreds of rooftops covered in solar panels strung together to generate power?

Roy Kuga, the vice president of the Energy Supply Division at California utility PG&E, had some interesting ideas about the pros and cons of each technology at the Berkeley, Stanford CleanTech Conference Series on Wednesday. Basically, while solar thermal plants provide lower solar prices, higher efficiencies and better energy storage, distributed solar rooftop programs are quick to deploy, and less costly when it comes to transmission lines and water needs. Check out the detailed list below:

Distributed Photovoltaic Solar Rooftop Projects:

Pros:

  • These projects can get up and running fast. Around 8 months, Kuga says, noting that the solar industry is also trying to bring down this time dramatically.
  • Distributed projects are not dependent on building long transmission lines to remote locations (such as the desert).
  • Distributed projects are also not dependent on the high water needs that solar thermal plants require for cooling.


Cons:

  • Distributed systems have high costs of deployment. Because each system is a separate project, each rooftop installment requires a lot of labor, transaction and implementation costs.
  • They scale more slowly because it takes time to get all the rooftops up and running.

Solar Thermal Plants:

Pros:

  • Solar thermal plants benefit from the economies of scale that can deliver lower solar power prices.
  • Solar thermal plant efficiencies are commonly higher than rooftop systems.
  • Solar thermal systems have pretty good energy storage technologies, so they are compatible with the intermittencies of solar. Solar thermal plants can store energy for when the sun goes down better than rooftop systems.

Cons: (Also check out our 8 Offbeat Hurdles for Solar Power Plants)

  • Solar thermal plants in the middle of the desert are transmission line dependent. Transmission lines are costly and difficult to get built.
  • Solar thermal plants need a lot of water, which is costly and delays permitting.
  • Solar thermal plants need a lot of land and require extensive permitting processes to get approved.
By Katie Fehrenbacher

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  1. I’d add a couple more cons to the PV side.

    1. The distributed systems require a smarter grid, which is happening, but from what I can tell, pretty slowly.

    2. PV, to make a difference, will require individual consumer acceptance and even given all the services cropping up to make the decision easier, a basic monetary payback of more than 5 years is going to be a tough sell for many people.

    And a pro:

    1. Your PV setup will still work if the electrical grid goes down. It might be less efficient, but it’s more resilient.
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  2. Thanks Alexis, I totally agree. Anyone else want to weigh in on pros and cons? We’ll update the list in a bit.

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  3. Real energy independence will come from individual solar roofs not central systems.

    This is recognized in Germany and Japan.

    What about footprint? Why do we want to continue using up land when there are already millions of square miles of existing roofs? What about terrorist attacks on a centralized power plant? Terrorists would find it difficult to blow up millions of roofs, unless we continue to allow Iran to build nuclear weapons.

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  4. A very informative article. Thanks for sharing.

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  5. “Solar thermal plants need a lot of water”
    WTF?? The water is not consumed, just repeatedly heated & cooled. It doesn’t even have to be potable water.

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  6. George Hefferon Thursday, May 8, 2008

    Do we need to have solar panels on every roof? What about small community facilities to spread the initial investment. I also think that PPAs may emerge as the enabler of PV solar for residences and small commercial applications. I’d be interested in reactions to this latter thought.

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  7. Rob Bernier Thursday, May 8, 2008

    Given the pros and cons of each side, including the costs for the PV processing plant, and the turbine plant, how does the cost benefit analysis work out?
    Rob

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  8. Pardon me, but what’s wrong with you (E2T) people?

    First, who cares about efficiency? We are talking about harvesting a resource that is pouring down at 1000 Watts per square meter on a sunny day. Efficiency is not the issue, overall cost is.

    And that’s the second point. PVs are really expensive. Not because of the install, or the separate sites, or whatever, it’s because the panels themselves are really expensive. 5 to 6 dollars per watt. Compare with 10 cents per kilowatt hour, and you see you need
    60000 sunny hours to recoup the cost of your panel. Assuming on average 6 sunny hours per day, that works out to more than 27 YEARS to recoup the cost of the panel itself. (Yes, the state of California offers $$$ credits for the panel, but that doesn’t mean that someone isn’t paying for all of this.)

    One should add “local thermal solar” to the list. 25kW units based on Stirling engine technology, deployed at the residential or neighborhood level. Less cost than PV, less transmission problems that the big thermal plants.

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  9. [...] Pros & Cons: Distributed Rooftop Solar vs. Desert Solar Thermal: Utilities plan to use solar power from both the massive solar plants that are being built in the California Mojave desert, as well as large scale distributed rooftop solar projects. So which technology is better? [...]

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  10. [...] by Craig Rubens No Comments Posted May 12th, 2008 at 9:00 am in Energy The debate between massive solar thermal plants and distributed roof top solar projects continues to get more interesting every day. Duke Energy’s CEO Jim Rogers says the [...]

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