In terms of dollars per watt, using theoretical efficiency limits, what technology holds the most promise to become the primary solar energy capture technology?

My hunch is carbon-based modules, since materials are abundant and relatively easy to manufacture; however their efficiency currently is nowhere near silicon-based semiconductors. In the future, assuming that scientists will push very close to the theoretical limits, what will provide the most power for the lowest cost?

If this is relevant at all, I am trying to decide where to focus my graduate studies in physics, and I want to contribute in getting the most promising technology to its limit. If you can at least point me in the right direction to figure out the answer myself, I would greatly appreciate it.

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    $\begingroup$ I think the question is poorly posed, as the optimum physics, versus the cheapest manufacturing methods aren't likely to line up. Also the value of efficiency is largely determined by area weighted costs, versus power related costs. The later is probably dominated by mounting system costs, and the later by wiring and inverter costs. Projected manufacturing costs of $.50 per watt or less will mean that the low tech area weighted costs could end up dominating the hightech (panels plus electronics) components. $\endgroup$ Jun 28, 2011 at 21:42
  • $\begingroup$ Interesting, and thanks for commenting; can you please explain a little further the distinction between area weighted costs and power related costs? If I interpreted this correctly, you are saying that even with a power efficiency that is high per module, installation-related costs may render the dollar-per-watt measurement to exceed a cheaper and less-efficient technology with lower installation cost? I was hoping that there was a universal way to compare technologies since you can take installation cost into account, but by all means please let me know if there are other things to consider. $\endgroup$
    – induvidyul
    Jun 28, 2011 at 22:24
  • $\begingroup$ It's an interesting question, but I guess it's outside the scope for this site - there isn't a single factual answer, only speculation. $\endgroup$
    – 410 gone
    Jun 29, 2011 at 6:03
  • $\begingroup$ Having said that, I'll note that silicon is very abundant too. And it will depend where in the world you are: in Northern Europe, onshore wind turbines are the cheapest way to capture solar energy, (wind being a product of insolation). In the tropics, CSP might work out best - but outside the tropics, some flavour of PV might be best As for various flavours of PV - who knows? There's lots of interesting stuff going on in plasmonics/photonics, but will they ever become number one commercially? $\endgroup$
    – 410 gone
    Jun 29, 2011 at 6:08
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    $\begingroup$ One more thing ... it's cost per unit energy that really counts, not cost per unit max power capacity. Which would you rather have, a 1kW unit that costs \$500 and lasts one year, or a 1KW unit that costs \$1500 and lasts 20 years? Dollars per watt are only part of the story. $\endgroup$
    – 410 gone
    Jun 29, 2011 at 12:09

1 Answer 1


As an ex-physicist who now works as a quant in power markets I think it's safe to say the physics of the matter will be swamped by the economics in commodities and how power markets work. Two things to note:

  • power prices are set by markets and not by the viability of the technology (prime mover)

  • solar is hard to make money with w/o a long term Power Purchase Agreement (PPA) and those are SUPER hard to come by.

There are many viable technologies available right now that from a physics perspective look very promising but from a market perspective are dead in the water.

Consider flywheels from Beacon power:


They approached my company a year or so ago looking to put together a deal with our origination group. The technology is sound, proven, and is clearly efficient. It's a really sweet idea that has tons of promise. Did we do the deal? No. Unfotunately pricing out regulation is hard and the rules that are followed by ISOs for payouts on regulation services are unclear. The ISOs are interested in the technology but they are making up the rules as they go and companies that try to make money off the flywheels are currently going back and forth with them to create a market structure that can allow someone who owns this technology to make a reasonable return. By reasonable I mean one that beats out gas, coal, oil, etc.

My point is that the market structure (or lack of one) is killing the deals for new tech like this.. Not the efficiency. Same goes for the solar (and the wind). The prime mover that will succeed is the one that's pushed by the companies that understand how best to work the power markets. Siting and development (meaning leaning how to best construct the installation) are huge factors as well. It's a bad scene when your dev guys don't know how to properly handle the solar modules or manage a solar installation project. It is indeed true that the physics of the technology must create a low-cost solution but the final word on success for a particular tech will be more based on the market acumen of the policy groups involved and the marketing/origination function than anything else.

Storage tech like flywheels from Beacon are a huge part of this puzzle too 'cause the sun never seems to be out exactly when you need it and the wind blows best during off peak hours. :) You need a good way to store the power so you can release it during favorable times of the day.

All in all, figuring out what tech is 'most promising' is more than just making a choice based on physics. It's a good question tho. Ur best bet is to talk to someone in power-markets from a big company like Constellation, PG&E, or perhaps TVA and ask them about the hurdles those technologies face. Then marry that up with a physics assessment on efficiency and you'll get a good hint on which tech to help push forward with your studies.

  • $\begingroup$ To some extent, you can get around this with small scale projects which serve to merely reduce the net energy demand (or perhaps shift it in time) of power consumers. Solar panels can be put on residental roofs for example, without negotiating PPAs. The posted answer is more specific to utility scale plants which are intended to export power to the grid, as opposed to partially offsetting internal use. So ther do exist at least some smaller scale niches that some technology can be demonstrated in. $\endgroup$ Jul 5, 2011 at 15:49
  • $\begingroup$ Although my question was a little more centered on choosing between types of solar energy technology (since I believe the future, the far far future lies in this), thank you for the input. I ask from a physics perspective because its where I'm coming from and where I would likely land. This almost makes me think that getting an MBA and going into it from the business side is a better idea! $\endgroup$
    – induvidyul
    Jul 5, 2011 at 22:45
  • $\begingroup$ I hate to say it but I can't actually disagree with you. :) A strong coupling of physics insight and understanding with an MBA is likely to be a combo that will get you where you want to go. Good luck Sarah! $\endgroup$
    – unclejamil
    Jul 5, 2011 at 23:13

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