Frequently Asked Questions

... about Photovoltaics

  • Isn't the cost of Photovoltaics (PV -- solar electric) very high?
  • When you examine any energy technology, you have to consider the energy return on investment as well as the dollar return. The solar industry has been using outdated technology which requires a great deal of energy during manufacturing, compared to the amount of energy recovered over time. This is easy to understand. It takes about 8 years to recover the energy used to make panels from one-sun crystalline solar cells (the kind that are used in standard PV panels). However, several groups are now developing PV systems that have energy paybacks of 1 or 2 years by either concentrating sunlight onto special crystalline cells, or by using very thin films of silicon applied by gas deposition onto a substrate such as glass or sheet-metal. [See http://www.ecotopia.com/apollo2/pvlever.htm/] Once in mass production, both of these types of solar systems will be economical by any criteria.

  • I think that this "energy investment" is effectively reflected in the price.
  • Price, which is dictated by arcane political manipulations, totally obscures the real issues here. By chasing pure dollar solutions, the solar industry lacks real discipline. Technologists have to get their act together on the energy Return-On-Investment ("ROI") first. When they produce something that has a good energy ROI (perhaps better labeled Return-On-Energy or "ROE"), then they can talk dollars (pesos and yen...). Take another look at this: if I invest $100 in electricity alone to make something, anything whose function is to produce electricity, and then it takes 8 years just to get back my $100 (before I can recover any other expenses I’ve incurred, which is what is meant by ROE), then it’s pretty obvious that it will take just about forever to get back my other expenses (labor, equipment amortization, distribution, overhead, profit, etc.). I’m barking up the wrong tree! Even oil is subject to this basic law: If it took 100 barrels of oil to dig an oil well and then 8 years to pump out 100 barrels, nobody would dig for oil either! (Which is where the oil industry is headed, by the way -- Kaufman and Cleveland’s work back in 1981 about "Yield-Per-Effort" (in Science, Vol 211, 6 Feb 1981, p. 576-579) showed that new oil exploration will eventually yield less oil per foot of drilling than the energy (oil) it will take to do the drilling -- the "energy break-even point." If you look at the direction that the trends are heading, you will see that the critical time is not far off in the USA. There are no conceivable price distortions (i.e., tax gimmics) that will allow humanity to continue such folly for very long.

    Neither can we perpetrate PV with a low ROE upon the world. Thankfully, there is high ROE PV in the offing. Process efficiency will improve the ROE of photovoltaics in mass production, just as costs will continue to improve. Since the 1970's, the energy efficiency in many aspects of manufacturing have improved to levels which would have been considered almost miraculous in those years. So, whether you are a fan of concentrators or thin-film, I won’t argue. One or both will bear fruit in terms of monetary Return-On-Investment (ROI). It is clear when you look at the energy economics:

    • ROE (1 sun crystalline)>8 years
    • ROI (for grid power): impossible!
    • ROE (thin-flim & concentrators)<2 years
    • ROI (for grid power): possible

    One square centimeter IHCPV cell produces more than 10 watts at 500 concentration -- > One 4 inch IHCPV wafer=425 W at 500 suns.

    It’s time to take this industry seriously, and realize what we’re doing. One-sun crystalline PV is a transportation solution: Make a panel – fill it up with electricity, in effect, in the factory -- and take it up to the top of a mountain where it will, in effect, release that trapped electricity to run a microwave station, which is lots simpler than taking a load of diesel fuel up there once a week to run a failure-prone diesel generator. But this isn’t an energy solution – it’s just "trading dollars" in the energy sense – it’s a transportation solution.

    No pricing scheme or any manner of arm-waving will ever make such a gadget economical for general electricity production.

  • Regarding PV concentrators: people have been doing this for the last 15 years, and I have seen no effective progress in that time. The basic factor is still system price. If there were real progress, our utilities would be buying these concentrators. They aren't even buying enough of the product to test it adequately and groups like Entech are really not making it.
  • Entech's failure or poor performance is unfortunate, but one failure doesn’t forecast an industry. Check around. People developing both concentrators and thin-film are about to perform miracles in the marketplace. And why? Because they didn’t waste time promoting one-sun PV cells and tax credits trying to fiddle-faddle with price: they developed technology with ROE’s that work.

    Mind you, the attractive ROE for concentrators will not apply to cloudy environments. In such places, thin-film will likely be the best alternative.

  • Solar and renewables have a fatal flaw when you consider how energy is used in our society -- their availability is NOT continuous and NOT predictable! These sources, even in their highest-tech refinements, cannot overcome that flaw (without storage). Without storage, renewables aren't even part of the world energy equation. The storage options are really limited today.
  • The solution has little or nothing to do with storage at the present time (though I would agree that eventually it will matter). For the short term future, we will continue to use oil, natural gas, coal, etc. for storage, which is as we are doing right now anyway: we’re using up Planet Earth's storage banks. The solution does have to do with understanding the underlying foundation of our discipline: producing more electricity with the gadget than it takes to make the gadget.

  • Will the world turn to nuclear energy?
  • Not likely. The nuclear industry is abiding in many fictions. It is no where near as economical as PV or wind energy is destined to be. I’m also not aware of breeder reactors in common use. So, powerful though it may be, I’m not counting on that industry to save the day. I once heard someone say that using nuclear energy to make toast is like using a chain saw to cut butter.

    • It is an exhaustable resource;
    • It remains very expensive, even when not considering the cost of nuclear waste management;
    • humanity has not yet learned how to manage either the wastes or the military/terrorism consequences of universal nuclear electric power. In virtually all nations, the nuclear power industry has essentially refused to adopt the same type of employee safety discipline which has become the norm in the airline industry. Many have tried to make the equipment "foolproof," but few seem to realize that this is possible only when the "fools" are under control. Three-Mile Island and even Chernobyl were not caused by equipment failures so much as by the lack of adequate safety disciplines.

    Solar (PV and wind energy in particular) will become economical and will beat out other alternatives because fundamental energy economics will dictate the outcome. We will also put nuclear energy in its proper place -- powering spacecraft too far from the sun to use solar power (like Voyager 1 and 2, the Galileo, or the Cassini) and not messing with our planet: good planets are hard to find!

  • Do you think the United States government has been funding enough research and development in solar energy?
  • The US DoE is still focused on traditional energy sources. The research in petroleum and nuclear energy is many times greater than that for renewable energy sources. In renewable energy the DoE focus of research is on applications (which is unnecessary because this can easily be done by the private sector -- manufacturers and users). The research on energy storage -- which is necessary as renewables become a major energy source -- has been quietly stopped. In short ... the USA government strongly (but quietly) supports a petroleum and nuclear future for our country and for the world.

    However, the fact that the USA government is doing very little shouldn’t be a cause of too much concern. The USA is now competing in a global marketplace. Australia, Japan, Indonesia, India, China, and many other countries are making substantial progress in PV and other renewable energy developments. Plenty of global citizens will have resolved their own energy problems when Americans really begin to suffer. Failing to prepare for the Global Hubbert Peak (when oil production begins to decline worldwide), to be trapped in the USA when that day of reckoning comes, it may be messy!

  • In the future, can solar cells be efficient enough to power products that we use every day (ie: computers, cars, coffee machines)?
  • Solar cells are already efficient enough. The reasons that we have not switched are two-fold -- (1) low ROE, as explained above, and (2) the political forces and economic forces which have a large investment in traditional (fossil fuel) energy sources. These interests need to see a profit from renewable investments before they will change.

    There is not enough solar energy falling on the surface of a car to give the performance we have all come to expect. All-solar cars which run with energy from collectors on the car itself are unwieldy. Solar race cars have a weird shape, and this shape is due to the diffuse nature of solar energy.

    Just the same, solar powered cars are quite useful to industry. Solar car racing events have given us much technology development, and the newly developed engineering devices are being applied to practical electric vehicles (EVs). Once PV is in mass production, solar powered cars (albeit without panels on-board) will be commonplace. We will be able to use PV to charge electric cars from panels on roof-tops or over parking lots, and we will have a sustainable transportation system. [See http://www.ecotopia.com/susxptn.htm/ ] Furthermore, with so many batteries being charged, the issue of energy storage will be mitigated to some extent. (In an emergency, you will be able to plug your home into your car. How's that for a switch?!)

  • Would these products be low in price and how will this transition be made?
  • A lot of people are asking these questions. Answers are beginning to appear. The state of California has passed several laws intended to help this transition. And solar charging stations for EV's exist. Over the next five years we will see better how to do these things based on what happens in California and in major cities around the world where pollution is driving EV development.

  • What other solar energy devices or products do you see everyone using in the future (besides calculators)?
  • Of course you realize that we all depend completely on solar energy. More than just powering calculators, every 12 hours the sun delivers to Planet Earth as much energy as humanity has ever derived from petroleum. It produces all of our food (photosynthesis), nearly all of our heat, nearly all of our light (can you imagine 24 hours of darkness year around?), much of our building material (i.e., wood), indeed virtually everything that we truly depend upon. Only in the past 200 years has humanity discovered how to liberate enough of our stored fossil resources to impact the way we live.

    I use the term "commercial solar" to distinguish human artifacts which utilize the sun's energy from sunpower in general. Mechanisms which produce electricity and other commercially viable forms of energy from sunlight include hydroelectric dams (rain), sailboats (wind), ordinary windows (light), fireplaces (biomass) -- the list is nearly endless. Throughout history, until this century, people adapted their dwellings to their natural surroundings. Shelters in harsh cold climates were oriented to capture the sun's head and in hot climates, shelters provided shade and thermal mass to escape the heat -- without air conditioning!

    Today we are rediscovering cost-effective uses of solar energy. Solar heating and cooling of buildings is practical and with modern materials can perform far better than the castles of kings did 200 years ago! No breakthroughs are needed. We just need to educate the people and let them know that they can find architects or builders or real estate sales people who know how to deliver a solar heated home. We do need to learn more about ways to retrofit existing buildings for solar heating. This is being done by a handful of builders worldwide.

    Solar heating of domestic water is cost-competitive in many areas of the USA today and is nearly universal in Israel. Solar electric systems (photovoltaics) are often the cheapest alternative today in remote areas where the utility grid doesn't already reach. The cost of extending the grid for one house even just 1/2 mile is usually much more expensive than installing a solar electric system on one house, today!

  • I am desirous of installing a PV system in my utility electrified home but I don't know the first thing about the physics, economics, etc. of PV. I do know basic wiring & electrical installation - your "advanced Home Depot" type. My AC is electric; home and water heating is gas.
  • The short answer: Use PV for emergency lighting, communications (TV/CB radio) and refrigeration. Add PV to provide your full system requirements later when the prices drop a bit...

    Unless you live a long ways from a utility grid power line, photovoltaics are not usually economical for general use. Because solar electricity (by photovoltaics) cannot yet be considered as being mass-produced anywhere in the world, costs have still not reached the level of economy that can typically be obtained from the local grid.

    On the other hand, as an insurance policy, PV can be very economical. It can be quite valuable to have electricity when there are power outages, which are likely to be more common in the future. We recommend that people set up a small PV system for emergencies - for communications (a small 12 volt TV and/or radio), a small 12 volt refrigerator, and emergency lighting. In the future, as solar becomes more economical, the system can be expanded to meet all of one's requirements, even for transportation. Under normal conditions, this power can be used for ordinary ambient lighting (for visibility at night in main rooms and hallways) to be supplemented by task lighting.

    Don't use solar to run expensive, inefficient old appliances whose design was based on cheap oil. Use passive solar heating and cooling techniques for your home. Make a sketch of the floor plan of your house with a north arrow and indicate trees, shading of other buildings, etc. and look for ways to cool or heat with the sun and natural shading.

    If you are planning to incorporate solar-generated electricity with environmentally responsive building design, we recommend that you contact Solar Design Associates (SDA), a group of architects and engineers dedicated to the design of sustainable buildings and the engineering and integration of renewable energy systems that incorporate the latest in innovative technology.

    If you are considering a large scale application for solar electricity, turn to our pages on solar electric micro-utilities.

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    updated 2000 September 1