Bright heat: Nicholas Melosh has developed a device for simultaneously converting the sun’s light and heat into electricity. Melosh makes and tests the device in this vacuum chamber in his lab at Stanford University.
Technology Review
Researchers have demonstrated a new mechanism for converting both sunlight and heat into electricity.
A new type of device that uses both heat and light from the sun should be more efficient than conventional solar cells, which convert only the light into electricity.
The device relies on a physical principle discovered and demonstrated by researchers at Stanford University. In their prototype, the energy in sunlight excites electrons in an electrode, and heat from the sun coaxes the excited electrons to jump across a vacuum into another electrode, generating an electrical current. The device could be designed to send waste heat to a steam engine and convert 50 percent of the energy in sunlight into electricity--a huge improvement over conventional solar cells.
The most common silicon solar cells convert about 15 percent of the energy in sunlight into electricity. More than half of the incoming solar energy is lost as heat. That's because the active materials in solar cells can interact with only a particular band of the solar spectrum; photons below a certain energy level simply heat up the cell.
One way to overcome this is to stack active materials on top of one another in a multijunction cell that can use a broader spectrum of light, turning more of it into electrical current instead of heat, for efficiencies up to about 40 percent. But such cells are complex and expensive to make.
Looking for a better way to take advantage of the sun's heat, Stanford's Nicholas Melosh was inspired by highly efficient cogeneration systems that use the expansion of burning gas to drive a turbine and the heat from the combustion to power a steam engine. But thermal energy converters don't pair well with conventional solar devices. The hotter it is, the more efficient thermal energy conversion becomes. Solar cells, by contrast, get less efficient as they heat up. At about 100 °C, a silicon cell won't work well; above 200 °C, it won't work at all.
The breakthrough came when the Stanford researchers realized that the light in solar radiation could enhance energy conversion in a different type of device, called a thermionic energy converter, that's conventionally driven solely by heat. Thermionic converters consist of two electrodes separated by a small space. When the positive electrode, or cathode, is heated, electrons in the cathode get excited and jump across to the negative electrode, or anode, driving a current through an external circuit. These devices have been used to power Russian satellites but haven't found any applications on the ground because they must get very hot, about 1,500 °C, to operate efficiently. The cathode in these devices is typically made of metals such as cesium.
Suntech CEO Zhengrong Shi made China a powerhouse in photovoltaic technology--and became a billionaire in the process. His next ambition: to make solar power as cheap as conventional electricity.
Government incentives and lower solar prices are starting to pay off.
You know you can't have any new technology unless nanotubes, nanopillars, or at least a little sprinkle of graphine. Color me disappointed. :-)
On a side note I do wonder if the electron emission couldn't be improved further by using techniques developed for SED and other electron emission displays. Thus lowering the temperature of operation further and reducing the need for exotic and expensive semi-conductors.
It was expensive going to the moon, it was expensive building the pyramids, it was expensive building the great wall of China, it was expensive conquering 3/4 of the known world, it was expensive building fleets of ships.
You can apply a fixed figure to a one-off and its huge. With mass manufacturing techniques a solar cell can have its costs reduced by mass production or subsidies or smarter techniques as the production is refined. You can only say its expensive to create 1 of them, you cant apply this to building (subsidised) quantities.
I also think applying the term expensive is disengenious to an emerging field. Every step that is taken is expensive. No point not doing it though.
It is better (for farms) to start at the very efficient designs and improve them than it is to work from a cost if cheap lets cover the planet in cells philosophy.
Every where a solar cell is deployed it kills everything underneath it. I believe the most sensible concept is for solar cells to be deployed on housing and also in highly efficient farms.
If the technology is that good and the farm is well situated it will pay for itself. The house may not need 50% efficiency but a cheap cell need only apply here.
I for one vote no for putting cheap low efficiency solar cells in farms stretching billions of sq k. Lets make those 50%+ cells and let them pay for themselves over-time.
Why not trapping all phonons in a tincan?
http://quatschtronauts.wordpress.com/2009/11/28/canned-sunshine/
Anybody who knows how to put this funny vision into practice?
With all the talk about steam engines, are they using the waste heat from the condensers? If so, could this system conceivably utilize waste heat from generating stations with the photons jumping up the electrons a little extra to make the system work at lower temperatures? (Cooling/condensing the steam, one supposes).All that hot water discharged into rivers or cooling towers could be an attractive resource.
Just drove down the Ohio river for about 100 miles opposite W.VA. My God, the savings from an extra five, ten percent efficiency in the generating process! Never conceived of so many generating plants in such a small area.
decentralised power generation
This a great development, as it creates a method to concentrate the power generating conversion elements. A concentrating mirror costs nothing compared to these elements. Even with 25% conversion in a simplified form, this principle could be promising and a cheap 4 M2 mirror made of aluminium foil and bamboo could produce 1kW peak power for TV, PC, chargers and light in sunny coutries. Now we have to wait for a handy way to store this electricity for driving a washing machine, night lamps and some kitchen apparatus. This principle would also reduce transport for a sunpower generator system as just the small light conversion elements needed to be transported to erect a power system, not those big clumbsy and vulnarable solarcell boards. Great for developping nations and for use on isolated locations! It could be the real breakthroug for the decentralised electrical power generation and grid.
I think the best way to use the sun's energy is to use it to illuminate the pages of a book on nuclear science for energy, medicine and propulsion research.
We have had 140 nuclear reactors running around the clock in the US for nearly 40 years without a radiation fatality. Yet ironically radiation paranoia had prevented us from building a single new one and taking the most obvious and only proven route out of our energy and climate problems.
Yep. I also think that the ~100,000 jobs related to coal that would be threatened by nuclear is a pretty big culprit. I think all these other alternative energy ideas are cool and should be researched, but they can never beat fossil fuels and certainly not nuclear. I wonder if the fossil fuel industry likes to promote these ideas [excluding nuclear] since they know they are basically paying an insurance fee to lock in their business for another century.
I agree with the above post. The coal industry isn't doing us any favors. You will find that more folks have died from black lung and mine accidents, than Nuclear. There is a lobby in Washinton supporting this industry, and bad mouthing Nuclear. A bad thing is that these existing old Nuclear Plants are not being replaced with the newest Nuclear technology which is more fail proof and thus safer. I predict that one of these ageing plants will eventually have an accident "God Forbid" which could have been avoided by having an agressive Nuclear strategy for energy production. It should not have to be this way! Nuclear technology is tremendously better today than it was 40 years ago! We should get smart and do the right thing and replace these old plants and build additional new ones as well. As a Nation, we need to get over the scare tactics of the Anti-Nuclear Activist and their Washinton DC lobby groups.
I live not that far from "Three Mile Island".
Have you gotten a tour of TMI? Do they give tours? It must be cool to get to see that all the time. I think the big picture is that nuclear is such a disruptive technology that it will be suppressed for a very long time. If climate hysteria were actually justified or fossil fuel supplies were really seriously threatened, opposition to nuclear would miraculously vanish. But to voluntarily give up a 100% domestic resource supplying a gazillion jobs that cannot be outsourced is just politically infeasible.
a.
By "climate hysteria" I assume you're referring to the green movement. And it is justified. If you're running out of fossil/non-renewable fuels, you sure as hell gotta have a plan for the future (i.e. when those nonrenewables run out).
b.
Fossil fuels ARE running out. Crude oil has been projected to run out in those easy-to-get-to spots (such as Gulf of Mexico, Alaska, UAE, etc.) in about 100 years.
c.
Fossil fuels are NOT a domestic resource. Most of the United State's oil come from various Middle Eastern countries, including Iraq and the UAE.
d.
Why on earth would you want to outsource jobs that could just as easily be preformed in the US? Yeah, yeah, it's cheaper. But, given the recession, keeping jobs within the borders of the US would be more helpful for the economy than outsourced jobs.
e.
It seems like most of this argument about nuclear is revolving around fission (Uranium into Plutonium). Admittedly, that is a very hazardous process and should not be used for energy use unless properly managed. This is what was lacking at the Chernobyl plant, and look where that went.
Instead of nuclear fission, nuclear power plants should utilize fuision (Hydrogen into Helium). It's safer, more efficient, and produces several hundred times more energy. Problem is, not many people seem to want to invest in it. Look up TOKOMAK on Google or Wikipedia or what have you.
One difficulty in fusion of hydrogen into helium is required super high temprature in millions of degrees, and very high pressure. To accompish that, we need to develop super condutors that operate at vey high tempeature to create plasma envelope for fusing hydrogen into helium. At Larence Livermore Lab, there was a fusion process that lasted 1.3 seconds, too short for practical use.
Initial input of energy to start fusion is very high.
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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larrykueneman
3 Comments
Solar Energy Devices
Over the past several years I have read in TR of likely 50 or 60 advances in solar cell technology. The bottom line however, is at the consumer level nothing has changed in years. Why?
Reply
john.sitler
4 Comments
Re: Solar Energy Devices
Theoretical efficiencies are the upper limits to any particular pathway. These efficiencies are further limited by the properties of available materials and by the practical (economic) constraints of building an ideal device. An example of this is mentioned here in the article, with multi-junction pv devices reaching ~40% efficiency, but being too costly to be practical.
I'm quite excited about this technique! It opens up a new pathway for solar energy designs. Perhaps it will not outstrip conventional CSP, but it represents a new possibility.
Reply
StupidPeasant
98 Comments
Re: Solar Energy Devices
How is government grant money distributed?
Reply
R Sweeney
67 Comments
Re: Solar Energy Devices
Most ideas die from hard economics.
The reality is that on Earth, insolation is only 1KW/M2, so efficiency can only get you so much payback per unit area, can only pay for a tiny amount of exotic anything.
Reply
v.hg-770
2 Comments
Re: Solar Energy Devices
SoalrWorld, First Solar, Potowatt, Shell, Evergreen, Kyocera, Solar-Fabrik, and Isofoton all build modules with 1000-1084 kWh/kW yields (annual) - modules with enough power to run an American home for nearly a month (Source: Photon Magazine, testing done in germany, which has lower insolation than many other locations, and would affect the output)
Reply
gblaze44
96 Comments
Re: Solar Energy Devices
Even if there's a technical advance, one has to take in manufacturing costs, is it a simple process or difficult? all effects the cost of manufacturing. then their is the materials themselves. Many factors go into bringing a technology to market.
Reply
Kevin Bullis
177 Comments
Re: Solar Energy Devices
It's true that most solar advances die from sheer economics. Translating from the lab to large scale production, historically, has taken decades.
But it's not true that nothing has changed for years. That was true for a while, since gov't-fueled demand helped keep prices up. But prices have dropped dramatically in the last couple of years.
See my story http://www.technologyreview.com/energy/25565/.
Costs to make the panels dropped by more than half since 2004, and after a brief period, most of that has been reflected in the price for panels. In some markets, prices to homeowners have stayed high--but that's not because of the cost to make them.
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