DailyDirt: Fuel From The Sun

from the urls-we-dig-up dept

Tue, Oct 14th 2014 5:00pm — Michael Ho

Solar energy is actually extremely abundant (obviously not at night). The problem is capturing it all without covering huge areas of land (or sea) in an economical way and then storing the energy efficiently so that we can use it when we need it (ahem, like at night). Nature has developed photosynthesis, but if we're going to rely more heavily on solar energy, we're going to need to improve on plants or come up with other ways to create and store solar energy. Here are just a few projects that rely on the sun to make fuel.

Lawrence Berkeley National Laboratory is working on an artificial photosynthesis process that could produce hydrogen as a fuel. These scientists are looking at molecules designed to absorb sunlight and create an electrical current that can break water into molecular hydrogen and oxygen. [url]
Natural photosynthesis isn't all that efficient, so maybe researchers can augment plants with nanomaterials to give photosynthesis a little boost. Adding carbon nanotubes to chloroplasts can enhance photosynthesis by a measurable amount, but scaling this augmentation up might be tricky. Also, we should probably figure out how this actually works before we introduce this grey-green goo into the environment.... [url]
The SOLAR-JET project is working on a chemical reactor that uses sunlight to power the production of syngas from just water and carbon dioxide. The syngas will be further reacted using the Fischer-Tropsch process to make a form of jet fuel (hence the name of the project). [url]

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Filed Under: biofuels, carbon dioxide, chemistry, energy, fischer-tropsch, fuel, hydrogen, lawrence berkeley national laboratory, lbnl, nanomaterials, nanotech, nanotubes, photosynthesis, solar, solar-jet, syngas

14 Comments

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Mason Wheeler (profile), 14 Oct 2014 @ 5:28pm

What's "a huge area"? With today's technology, 100 square miles of solar panels could power the entire US continuously, if you had some way to store the power so it keeps flowing at night.

That may sound like a huge area, until you realize that somewhere, someplace in the deserts of California, Nevada, Arizona, Utah and New Mexico, there has to be a 10x10 mile plot of land that's so inhospitable (and overly hot and sunny!) that no one wants it.
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Anonymous Coward, 14 Oct 2014 @ 5:42pm

Re:
Would you have a 100 square mile area where sunlight never reached because it was all solar panels? I'd wonder about what that would do to the ecosystem.
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Pete, 14 Oct 2014 @ 8:14pm

Solar is very expensive
Powering the USA by solar, with today's real technology would take a plant 210,000 sq miles and costing $65 trillion. Maintenance would be costly too.

http://wattsupwiththat.com/2014/07/31/capture-the-sun-power-america-with-solar-is-there-a-busine ss-case/

The issue is that we couldn't spend that money twice, so everyone would be significantly poorer.
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MrTroy (profile), 14 Oct 2014 @ 10:37pm

Re:
What's "a huge area"? With today's technology, 100 square miles of solar panels could power the entire US continuously, if you had some way to store the power so it keeps flowing at night.

Citation needed, because I don't think this stacks up.

Energy usage in the US in 2013 was apparently 4,686,400,000 MWh [1]. Energy density of solar panels is apparently on the order of 175 W/m2 [2]

I'm guessing that's a maximum instantaneous power generation potential, but just in case it means something else I'm going to overestimate to get easy numbers. Say the max generation output is 200 watts, there are 20 sunny hours per day and 400 sunny days per year. That gives us energy production of 1.6MWh per year per square metre of solar panel, or a requirement of nearly 3 billion square metres of solar panels, or a square area of nearly 55km (34 mi) length.

More realistic (but still optimistic) figures gives an average of 8 maximally sunny hours over 300 days, for an area requirement of 10 billion square metres, or a square nearly 100km (62 mi) to a side.

You'd need these numbers to be out by two orders of magnitude to generate enough power in a 10x10 mile plot for the entire US! But that's kind of a moot point anyway, since transmission inefficiencies would kill the scheme - much better to generate the power local to use, in small plots all over the place... Rooftop would be ideal, in low density living areas! Higher density living and commercial use will probably need energy piped in from elsewhere though, and less sunny areas would need to look at alternatives such as wind power (I'm still waiting for http://www.windpods.com to become more than a pipe dream).

[1] http://en.wikipedia.org/wiki/List_of_countries_by_electricity_consumption
[2] http://en.wikipedia.org/wiki/Solar_panel#Efficiencies - considered "on the order of" due to the disputed tag
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Lawrence D’Oliveiro, 15 Oct 2014 @ 12:38am

Photosynthesis Is Unbelievably Inefficient
Photosynthesis only captures about 0.5% of the energy falling on a green plant. Compare this to solar cells, which are at least an order of magnitude more efficient.

The key enzyme in photosynthesis is called RuBisCo, and as far as enzymes go it is, shall we say, an underachiever. It works amazingly slowly compared to typical enzymes.

Not to mention the fact that photosynthesis primarily takes energy from red light, while our Sun puts out most of its energy in yellow light. Thus, the optimum colour of chlorophyll would be, not green, but blue. Optimization mismatch, much?

If you want disproof of Intelligent Design, it would be hard to top this.
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Anonymous Coward, 15 Oct 2014 @ 7:03am

Re: Re:
If the goal is getting the most energy from the smallest area, Concentrated Solar Power(CSP) running a Stirling engine would be used instead of photovoltaic(PV). CSP-Stirling is more efficient than PV(30% compared to 15%). [1]

This doesn't make your calculations match Mason's statement, but it certainly gets closer.

[1] http://en.wikipedia.org/wiki/Solar_thermal_energy#Dish_designs
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New Mexico Mark, 15 Oct 2014 @ 8:53am

Re: Solar is very expensive
As someone who has designed and used a solar power home for several years, I agree that the initial investment is very large, with a 15-30+ year payback depending on insolation of the local area. I've kept pretty close tabs on alternative energy technologies and any "one size fits all" solution is usually the worst approach. Instead, we should be looking at the optimal blend of technology and scaling by region.

Blending solar, wind, hydroelectric, and geothermal helps with load balancing. (For instance, cloudy days are often accompanied with increased wind, and of course hydroelectric and geothermal are 24/7.)

Blending partial home collection / storage with far more economically efficient utility generation and distribution would allow utilities to have far smaller generation while providing customers greater reliability. (There are few areas where home collection could not include solar hot water as well.)

Smart home inverter/distribution panels would allow for better load distribution and allow customers to continue operation at a reduced level (maybe no major appliances, but the refrigerator and outlets would work) even during a complete outage.

We need utilities with the freedom and courage to pull a Google gigabit move with whole communities and/or cities and offer these types of solutions. There would be some huge issues to work out (for instance, ownership, control, and emergency override control of home-based collection and storage equipment), but I think the obstacles are not insurmountable.
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New Mexico Mark, 15 Oct 2014 @ 9:22am

Re: Photosynthesis Is Unbelievably Inefficient
Without even taking one side or the other, that seems like a pretty lame argument because it tries to evaluate in a vacuum one tiny part of an incredibly complex system. (To keep from going too far off track in the main discussion, it is like trying to create a scenario where the whole world only generates energy via photovoltaics.)

If plants were any more efficient, would animals even stand a chance? In fact, in a molecules-to-man scenario, why wouldn't plants evolve a high enough efficiency to prevent "higher" life forms from occurring since these are all ultimately predators of, and dependent upon, plants?

Efficiency alone doesn't necessarily reflect intelligence. In electronics, circuits are often deliberately detuned from their peak Q (optimization) in order to (for instance) be efficient over a greater bandwidth or to better match other circuits. As a negative example, crystal meth was originally an attempt to perfectly optimize humans for greatest efficiency and endurance, and while that might work for a while, that very efficiency is ultimately far more destructive than useful.

Finally, I've worked for organizations who measured everything by efficiency. In general, they actually lost in the long run when measured in the bigger picture of overall organizational success. Enron (which deliberately used an evolutionary model for its employees -- and as a disclaimer -- by whom I was never was employed) is a prime example.

Please don't think I'm ignoring any reply you make... any questions are merely intended to be thought-provoking, and I usually don't revisit old posts.
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John Fenderson (profile), 15 Oct 2014 @ 11:06am

Re: Re: Photosynthesis Is Unbelievably Inefficient
An excellent reply. I would add that this seems to touch on an aspect of evolution that people often misunderstand. There is zero reason to believe that evolution would result in plants that are optimized for solar efficiency. Evolution is the process that results in increasing optimization of the ability for a species to survive in the circumstances that it finds itself.

This may or may not be related to efficiency of energy conversion. As you point out, there are a ton of variables that affect the ability to survive, and to look at just one can be misleading. For example, it may well be that what is needed for optimize conversion efficiency has a side-effect that reduces survivability overall.
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Mason Wheeler (profile), 15 Oct 2014 @ 11:29am

Re: Solar is very expensive
Seriously? Your "source" is a climate change denialist site?
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John Fenderson (profile), 15 Oct 2014 @ 11:52am

Re: Solar is very expensive
What you say is only true if you['re talking about using the most expensive method possible for obtaining solar energy. If you're talking about the most cost-effective (in terms of price per KWh) solar technologies, then solar becomes only a bit more expensive than oil.
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Zonker, 15 Oct 2014 @ 12:47pm

Re: Photosynthesis Is Unbelievably Inefficient
Photosynthesis only captures about 0.5% of the energy falling on a green plant.
For some reason this makes me think of taking the (flawed) concept of the recent movie "Lucy" and applying it to the plant kingdom: what happens when plants achieve 100% energy capture from sunlight?

Come on Hollywood, let's make this happen.
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Mason Wheeler (profile), 15 Oct 2014 @ 1:51pm

Re: Re: Solar is very expensive
Exactly. Again, see: getting data from denialists.
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Anonymous Coward, 16 Oct 2014 @ 6:57am

Re: Re: Solar is very expensive
Not just the most expensive but also greatly inflated with the "50% safety factor".
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