Climate

For Nanosolar, the Future Is Municipal Solar Power Plants

firstpanelsshipped_web.jpgTraditional photovoltaic (PV) is typically installed on rooftops and competes with retail electricity. Over 40% of the cost of a system can be in the installation, which must be customized to every rooftop. So technologies that dramatically lower PV cost end up having a less dramatic impact on total residential system cost. So it is natural that the next generation technologies, such as thin films of copper indium gallium selenide (CIGS) printed as ink on conductive substrates need to look at non-rooftop applications, where the installation of a large solar farm is fairly turnkey.

Nanosolar, a thin-film PV startup, has just announced their vision in their blog and newsletter. They see the best fit for solar being municipal solar plants of 2-10MW in size and suggest such plants can be done in 12 months, providing a significant advantage over coal or nuclear. Martin Roscheisen, Nanosolar’s CEO, writes

A 2MW municipal solar power plant requires about 10 acres of land to serve a city of 1,000 homes — that’s acreage generally easily available at the outskirts of any city of such size in even the most developed countries. Similar for a 10MW plant for a city with 5,000 homes: This would require five such lots….

In a solar power plant, solar panels are mounted onto rails above the ground so that grass and flowers can continue to flourish in between and below the rows of panels. Care is taken that sufficient amounts of rainwater can drop through between adjoining panels so that the flowers and organisms below are not starved….

While rooftops are surely a good application too for solar panels, it is a business that’s difficult to scale rapidly in a truly meaningful way. Crawling onto rooftops and mounting solar panels in compliance with building codes is fundamentally always a somewhat more expensive proposition.

Roscheisen does not explain how grass and flowers are to grow below panels without sunshine (between rows makes more sense).

Currently Nanosolar is only pursuing utility-scale solar, and is sold out for 12 months. This isn’t a technology you will be able to put on your roof any time soon.

coolearth solar balloons installedAnother company with a similar vision is coolearth, which uses a reflective balloon as a low-cost concentrator. They too are pursuing utility-scale applications, though they suggest ground-based (not rooftop) residential and commercial availability will follow. Whether there is a market for ground-based residential installation is unclear, however.

Coolearth claims that using balloons as concentrators instead of mirrors is 400— cheaper, and uses 60— less steel for the truss and rigging. The small PV inside the balloon is water cooled. In their video, they claim a cost of 18 cents per Watt.

One disadvantage of PV compared to some Concentrated Solar Power (CSP) technologies, with which it competes, is that PV does not have the possibility of nighttime generation from Thermal Energy Storage (TES) as found on some (but not all) CSP systems. However, with the daytime electricity demand often twice that of nighttime, PV can still be a useful addition to the grid.

Read Martin Roscheisen’s Municipal Power Plants for yourself.

15 Responses to For Nanosolar, the Future Is Municipal Solar Power Plants

  1. Robert says:

    CIGS uses Gallium and Indium. Are global reserves adequate for large scale deployment?

  2. Zane Selvans says:

    The crustal abundances of both Indium and Gallium are very low, and prevent CIGS from being scalable to the Terawatt level. Any energy solution we consider in the context of having a meaningful impact on our carbon emissions must be extremely scalable, and so cannot depend on any rare materials. Prof. Harry Atwater at Caltech has a decent talk on this and other important aspects of “next generation” solar power:

    http://nrg.caltech.edu/video/atwater_cable.ram (Real Media)

    There are a bunch of other energy talks at the Caltech NRG 0.1 site too:

    http://nrg.caltech.edu

    but some of them are too technical for the lay audience (Francis Arnold’s talk on biofuels is another good one).

  3. Earl Killian says:

    I don’t know the reserve situation for CIGS. I think it is appropriate to ask that again if CIGS technology actually becomes very popular. It is of course not the onl cheap solar technology

  4. Mark Shapiro says:

    “Over 40% of the cost of a system can be in the installation, which must be customized to every rooftop.”

    Doesn’t this suggest that we should work to reduce installation cost, by standardization, and, more valuable yet, building integration?

    With standardized, integrated PV panels, total installation cost could actually be lower than installation of an ordinary roof. That removes 40% of PV’s cost.

    Next step: integrate the DC output of the PV with the DC input of all electronic devices in the home, eliminating the inverter and its costs.

  5. Earl Killian says:

    Mark, I think that is a great idea, but I think companies have been trying with only limited success. There are companies that make products targeted at new roofs that integrate PV into a roofing shingle, but unfortunately they end up costing quite a bit. Of course I like the idea of a DC standard for household wiring. There are efforts to create Net Zero home standards. I wonder if such a thing might be inserted there?

  6. Orion says:

    If you incorporate solar panels in new housing developments then the installation costs go down considerably thanks to economy of scale – either the roof tiles themselves have PV incorporated in them or your PV installer crew follows right behind the roofing crew. Instead of having one rectifier panel per house you have one common station per block and all the owners are part of the electric coop. So it’s not EITHER put PV arrays on houses OR in open fields, you can combine functions. The trick is to get an ample supply of PV cells at a cost competitive with conventional power plants.

  7. Less advanced are suggestions that building codes require that all structures be “solar ready” in terms of their wiring. I’m guessing this would allow inverters and solar panels to be “plug and play” reducing installation costs substantially:

    http://www.environmentnewmexico.org/news-releases/legislative-news/legislative-news/solar-ready-roofs-bill-passes-legislature

  8. Mark Shapiro says:

    Michael –
    “Solar ready” is an excellent idea, and that’s exactly why I’m begging for a DC standard. An industry standard voltage, together with a standard plug and receptacle, (exactly analogous to the 120 VAC, 60 cycle, with the 3-pronged plug and receptacle) IS precisely solar ready.

    You eliminate the inverter (10% of PV’s cost), all the conversion losses, and all those ugly cell-phone adapters.

    Earl – solar shingles are interesting, but always seemed quirky. Can’t we make the solar modules into a roofing product? It’s not trivial, but isn’t is fairly conventional engineering?

  9. Mark Shapiro says:

    And to all –

    PV installed costs $8-10 per watt:
    $3-4 for modules, (and dropping)
    3-4 for installation,
    1-2 for inverters.

    Eliminate the installation and inverters, and PV is economical today. If Nanosolar achieves $1/Watt modules, PV wins!

    (Remember also that for all private homeowners, PV yields tax-free income.)

  10. Mark,
    Your more ambitious scheme means rewriting the entire electric code and appliance standards for solar roofs. I don’t think that this is necessarily such a good place to start given the additional expense and all the parties that need to “get on the same page”.

    Additionally you will have to have an inverter anyway to convert AC to DC if you wire the house for DC to be able to use current from the grid at night.

    So, I think a far easier place to start is to simply have homebuilders do perhaps $200 more worth of work that will save perhaps $2000 worth of work to install a solar system later on either as part of the construction process or as a future retrofit.

    Eventually, for a number of reasons not related to solar, the building industry will move to more pre-fabricated and modular construction which will make building integrated solar much easier to include.

  11. Earl Killian says:

    Mark, I think the primary issue with picking a DC standard would be the picking the voltage. Higher voltages (e.g. 72V) allow power to be transferred at lower amperage, saving copper. They are somewhat more dangerous, and increase the cost of down converting to the low voltages used by modern transistors (e.g. 1V). Off-grid houses often used 12V, 24V, or 48V for DC wiring. I am concerned that this is too low for some applications (too much amperage required). It would be nice to have a group study it. One choice might be similar to our 240V/120V AC split: have -36V, 0, and +36V. High-power devices can get 72V between the + and – supplies. Lower power devices can get 36V between 0 and + supply. There’s a solution I like even better though. I believe the power cord should not be dumb, but should allow communication between the circuit breaker and the appliance. This will be important for negotiation, e.g. the breaker telling the appliance that power must be conserved (e.g. the batteries are getting low in an off-grid house). So one thought is that the wall plug nominally puts out 12V, but a device, after being plugged in can use the negotiation protocol to request an increase in the plug voltage. The only problem here is this makes it impossible to wire outlets in parallel (everything must be a star configuration, as in ethernet). It seems worth studying though.

  12. Earl Killian says:

    Michael is correct that an inverter is typically required, even in an off-grid house (at least the ones I’ve seen thought it necessary). However, the inverter wattage is somewhat reduced by the existence of the DC option. Since the inverter is typically not as costly as installation, I think the effort needs to be in reducing installation cost. The DC stuff is fun to speculate on, but it is not the priority.

  13. Mark Shapiro says:

    Michael and Earl –

    Thanks for the thoughtful replies. I agree with just about all the comments.
    It would take a lot of study, and a lot of parties working together, and it would add a big chapter to the electrical code. Choosing the best voltage would be the critical factor.

    A DC standard would do more than encourage PV, though. It would eliminate all those wall warts. Maybe more valuable, one can imagine outlets on planes, trains, taxis, and cars for cell phones, laptops, etc. And, it would be global.

    Earl – yes, eliminating the installation cost is key. Creating a PV roofing system that installs faster than a standard roof is the goal. It means the installation cost is negative.

  14. Mark Shapiro says:

    By the way, a cheap 12V DC standard already exists: the cigarette lighter. I’m really just trying to expand on that and bring it into the house. Hence my interest in putting it in vehicles.

    Earl – my guess is that the sweet spot is 24V. And of course leave 120/240 for the big appliances.

    Another item – I just saw a company called Nextek that is trying something like this. IS it interesting? – http://www.nextekpower.com/index.html

  15. Well written blog.. Will come back again soon.