MIT's new nano-photo crystal cell -- better than silicon solar cells

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MIT's new nano-photo crystal cell -- better than silicon solar cells

Post by Cr6 on Sun Dec 25, 2016 11:53 pm

Looks like a revolution of sorts if more than a proof of concept. Looks like a hidden company is going public with a crystal product shortly:

====
Hot new solar cell

System converts solar heat into usable light, increasing device’s overall efficiency.

David L. Chandler | MIT News Office
May 23, 2016
Press Inquiries
https://news.mit.edu/2016/hot-new-solar-cell-0523
https://news.mit.edu/2016/new-solar-cell-more-efficient-costs-less-its-counterparts-0829
https://bgr.com/2016/05/25/solar-panels-efficiency-doubled-mit/
http://www.nature.com/articles/nenergy201668.epdf



A team of MIT researchers has for the first time demonstrated a device based on a method that enables solar cells to break through a theoretically predicted ceiling on how much sunlight they can convert into electricity.

Ever since 1961 it has been known that there is an absolute theoretical limit, called the Shockley-Queisser Limit, to how efficient traditional solar cells can be in their energy conversion. For a single-layer cell made of silicon — the type used for the vast majority of today’s solar panels — that upper limit is about 32 percent. But it has also been known that there are some possible avenues to increase that overall efficiency, such as by using multiple layers of cells, a method that is being widely studied, or by converting the sunlight first to heat before generating electrical power. It is the latter method, using devices known as solar thermophotovoltaics, or STPVs, that the team has now demonstrated.

The findings are reported this week in the journal Nature Energy, in a paper by MIT doctoral student David Bierman, professors Evelyn Wang and Marin Soljačić, and four others.

While all research in traditional photovoltaics faces the same underlying theoretical limitations, Bierman says, “with solar thermophotovoltaics you have the possibility to exceed that.” In fact, theory predicts that in principle this method, which involves pairing conventional solar cells with added layers of high-tech materials, could more than double the theoretical limit of efficiency, potentially making it possible to deliver twice as much power from a given area of panels.

“We believe that this new work is an exciting advancement in the field,” Wang says, “as we have demonstrated, for the first time, an STPV device that has a higher solar-to-electrical conversion efficiency compared to that of the underlying PV cell.” In the demonstration, the team used a relatively low-efficiency PV cell, so the overall efficiency of the system was only 6.8 percent, but it clearly showed, in direct comparisons, the improvement enabled by the STPV system.

The basic principle is simple: Instead of dissipating unusable solar energy as heat in the solar cell, all of the energy and heat is first absorbed by an intermediate component, to temperatures that would allow that component to emit thermal radiation. By tuning the materials and configuration of these added layers, it’s possible to emit that radiation in the form of just the right wavelengths of light for the solar cell to capture. This improves the efficiency and reduces the heat generated in the solar cell.

The key is using high-tech materials called nanophotonic crystals, which can be made to emit precisely determined wavelengths of light when heated. In this test, the nanophotonic crystals are integrated into a system with vertically aligned carbon nanotubes, and operate at a high temperature of 1,000 degrees Celsius. Once heated, the nanophotonic crystals continue to emit a narrow band of wavelengths of light that precisely matches the band that an adjacent photovoltaic cell can capture and convert to an electric current. “The carbon nanotubes are virtually a perfect absorber over the entire color spectrum,” Bierman says, allowing it to capture the full solar spectrum. “All of the energy of the photons gets converted to heat.” Then, that heat gets re-emitted as light but, thanks to the nanophotonic structure, is converted to just the colors that match the PV cell’s peak efficiency.

In operation, this approach would use a conventional solar-concentrating system, with lenses or mirrors that focus the sunlight, to maintain the high temperature. An additional component, an advanced optical filter, lets through all the desired wavelengths of light to the PV cell, while reflecting back any unwanted wavelengths, since even this advanced material is not perfect in limiting its emissions. The reflected wavelengths then get re-absorbed, helping to maintain the heat of the photonic crystal.

Bierman says that such a system could offer a number of advantages over conventional photovoltaics, whether based on silicon or other materials. For one thing, the fact that the photonic device is producing emissions based on heat rather than light means it would be unaffected by brief changes in the environment, such as clouds passing in front of the sun. In fact, if coupled with a thermal storage system, it could in principle provide a way to make use of solar power on an around-the-clock basis. “For me, the biggest advantage is the promise of continuous on-demand power,” he says.

In addition, because of the way the system harnesses energy that would otherwise be wasted as heat, it can reduce excessive heat generation that can damage some solar-concentrating systems.

To prove the method worked, the team ran tests using a photovoltaic cell with the STPV components, first under direct sunlight and then with the sun completely blocked so that only the secondary light emissions from the photonic crystal were illuminating the cell. The results showed that the actual performance matched the predicted improvements.

“A lot of the work thus far in this field has been proof-of-concept demonstrations,” Bierman says. “This is the first time we’ve actually put something between the sun and the PV cell to prove the efficiency” of the thermal system. Even with this relatively simple early-stage demonstration, Bierman says, “we showed that just with our own unoptimized geometry, we in fact could break the Shockley-Queisser limit.” In principle, such a system could reach efficiencies greater than that of an ideal solar cell.

The next steps include finding ways to make larger versions of the small, laboratory-scale experimental unit, and developing ways of manufacturing such systems economically.

This represents a “significant experimental advance,” says Peter Bermel, an assistant professor of electrical and computer engineering at Purdue University, who was not associated with this work. “To the best of my knowledge, this is a new record for solar TPV, using a solar simulator, selective absorber, selective filter, and photovoltaic receiver, that reasonably represents actual performance that might be achievable outdoors.” He adds, “It also shows that solar TPV can exceed PV output with a direct comparison of the same cells, for a sufficiently high input power density, lending this approach to applications using concentrated sunlight.”

The research team also included MIT alumnus Andrej Lenert PhD ’14, now a research fellow at the University of Michigan, MIT postdocs Walker Chan and Bikram Bhatia, and research scientist Ivan Celanovic. The work was supported by the Solid-State Solar Thermal Energy Conversion (S3TEC) Center, funded by the U.S. Department of Energy.

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Re: MIT's new nano-photo crystal cell -- better than silicon solar cells

Post by Cr6 on Sun Dec 25, 2016 11:56 pm

Of course, that’s an oversimplification of the process. Here’s a more detailed explanation from the team’s abstract:

Solar thermophotovoltaic devices have the potential to enhance the performance of solar energy harvesting by converting broadband sunlight to narrow-band thermal radiation tuned for a photovoltaic cell. A direct comparison of the operation of a photovoltaic with and without a spectral converter is the most critical indicator of the promise of this technology.Here, we demonstrate enhanced device performance through the suppression of 80% of unconvertible photons by pairing a one-dimensional photonic crystal selective emitter with a tandem plasma–interference optical filter. We measured a solar-to-electrical conversion rate of 6.8%, exceeding the performance of the photovoltaic cell alone. The device operates more efficiently while reducing the heat generation rates in the photovoltaic cell by a factor of two at matching output power densities. We determined the theoretical limits, and discuss the implications of surpassing the Shockley–Queisser limit.Improving the performance of an unaltered photovoltaic cell provides an important framework for the design of high-efficiency solar energy converters.

Too much? Here’s a slightly simpler explanation from MIT News:

The basic principle is simple: Instead of dissipating unusable solar energy as heat in the solar cell, all of the energy and heat is first absorbed by an intermediate component, to temperatures that would allow that component to emit thermal radiation. By tuning the materials and configuration of these added layers, it’s possible to emit that radiation in the form of just the right wavelengths of light for the solar cell to capture. This improves the efficiency and reduces the heat generated in the solar cell.



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Re: MIT's new nano-photo crystal cell -- better than silicon solar cells

Post by Cr6 on Mon Dec 26, 2016 1:01 am

Here's one company related to this work: WiTricity
http://www.witricity.com/

http://www.bloomberg.com/research/stocks/private/snapshot.asp?privcapId=39335190
WiTricity Corporation designs, develops, manufactures, and commercializes wireless power solutions based on magnetic resonance technology. Its products and solutions are used for mobile device charging, wireless batteries, retail packaging, lighting, EV and HEV wireless charging, in-vehicle mobile device charging, wireless charging for robotics and underwater vehicles, direct powering of sensors, through-the-skin charging for implantable devices, wireless charging for hearing aids, wireless recharging of warfighter battery packs, wireless charging for IED robots, in-seat charging, and more. The company also licenses and transfers its wireless power transfer technology that allows OEMs to design and develop products that incorporate its technology. It offers its products for a range of applications, which include consumer electronics, automotive, industrial, medical, and military. The company was founded in 2007 and is based in Watertown, Massachusetts.

A liste Founder, Marin Soljačić's, MIT Page:
http://www.rle.mit.edu/marin/

In addition to wireless energy transfer, Prof. Soljačić works on numerous problems on electromagnetism [9] in materials structured on the scale of the wavelength, such as micro- and nano-structured materials for infrared and visible light, including nonlinear optical devices and surface plasmons. His recent research, supported by a US$20 million grant from the U.S. Department of Energy, focuses on use of photonic crystals in solar cells.[8]

https://en.wikipedia.org/wiki/Marin_Solja%C4%8Di%C4%87

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Re: MIT's new nano-photo crystal cell -- better than silicon solar cells

Post by Cr6 on Mon Dec 26, 2016 1:07 am

http://www.rle.mit.edu/marin/ (more at link)

Technological advances of the past decade have enabled the control of the material structure at length-scales smaller than the wavelength of light. This enabled creation of new material-systems (e.g. photonic bandgap crystals, or various surface plasmon systems ), whose optical properties are dramatically different than those of any naturally occurring material. For example, nanostructured materials which display diffraction-less propagation of light , exhibit negative refraction, or support very slow propagation of light , have all been demonstrated. Our research interests are in exploring the new and exciting physical phenomena supported by such materials. Our work is roughly equally split between theoretical and experimental studies.

For some representative examples of this, please check out our work on one-way waveguides, plasmons in graphene, Dirac points in Photonic Crystals, a unique way of trapping light (2013), novel transparent displays (2014), systems for angular selectivity (2014) of light, Weyl points (2015), exceptional rings (2015), novel X-ray sources (2015), enhanced incadescent sources (2016), as well as allowing “forbidden” transitions (2016).



The unique properties of optical nano-structured materials have already enabled a wide range of very important applications (e.g. in medicine, energy , telecommunications, defense, etc.) and are expected to do even more so in the future.

We are also interested in various topics in nonlinear optical physics. Maxwell’s equations as presented in most undergraduate text books are linear. However, all materials in nature are nonlinear ( including vacuum ), and sure enough, at high light intensities, optical phenomena becomes nonlinear, displaying a wide range of rich and beautiful behavior. For example, almost every general non-linear dynamics phenomenon (e.g. solitons , pattern formation, fractals , etc.) can now be studied in optical material systems.

In addition, we are excited about the feasibility of wireless power transfer.

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Re: MIT's new nano-photo crystal cell -- better than silicon solar cells

Post by Cr6 on Tue Dec 27, 2016 8:53 am

Another related story on an "Infinite-Energy" stock. Interesting site by the way. Helps debunk "big-new-tech" stock claims:

http://www.stockgumshoe.com/reviews/micro-energy-trader/kent-moors-teases-his-infinite-energy-nano-grid-stock-for-38901-gains/

So what’s this “radical invention” that he’s hinting at as he tries to get us to sign up for his Micro Energy Trader? Here’s how he sums it up:

“… it uses liquid or semi-liquid waste from just about ANY source…

“Including used motor oil and industrial fluids, antifreeze, paint thinner, human sewage, manure and poultry litter, contaminated water, and more…

“To quickly produce large quantities of a gas that burns hotter than any other gas known to man – up to 10,500° Fahrenheit”

And the silly “secret” stuff:

“Of course, the invention I’m talking about has an official name. So does the gas it produces…

“However, I can’t reveal those names in a public forum like this without tipping off every hedge fund on Wall Street to this tiny $1-per-share company….

“for ‘camouflage’ purposes…

“In this presentation, I’m going to refer to this invention as the ‘H-Arc Generator.’

“And I’m going to call the clean, ultra-hot-burning gas it produces ‘plasmalene.'”

This is really why Stock Gumshoe started — many, many years ago, I got sick of these “secrets” and “camouflage” names and started researching them. So I guess it’s good that they still do this, it gives me a reason to jump into work each morning with renewed vigor — even if 90% of the “secrets” we uncover aren’t actually that interesting once you find out the reality, at least we’ll hopefully help some folks avoid making expensive mistakes. Subscribing to newsletters isn’t always a mistake, of course, we can learn a lot from plenty of them… but putting real capital at risk in some microcap idea because you believe the wild promises of the hype-filled ad is very often going to lead to disappointment (or worse).

http://www.stockgumshoe.com/reviews/micro-energy-trader/new-gas-molecule-that-burns-hotter-than-the-sun-dr-kent-moors-says-theres-never-been-a-moneymaking-situation-quite-like-this-in-the-entire-history-of-energy/

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Re: MIT's new nano-photo crystal cell -- better than silicon solar cells

Post by Cr6 on Tue Dec 27, 2016 11:05 pm

Link to a sales video presentation for a newsletter on non-silicone Solar. Take with a grain of salt but has a pretty good overview of this technology:

http://oilprice.com/er/video?utm_campaign=solar&utm_placement=nl1

http://video.oilprice.com/james-solar-ago16-v3.mp4

https://oilprice.com/er/transcript/179

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