## UD-Led Team Sets Solar Cell Efficiency Record of 42.8%; Joins DuPont on $100M Project ##### 28 July 2007  The lateral solar cell architecture with a specially designed concentrator contributes to the enhanced performance. Click to enlarge. Using a novel technology that adds multiple innovations to a very high-performance crystalline silicon solar cell platform, a consortium led by the University of Delaware has achieved a record-breaking combined solar cell efficiency of 42.8% from sunlight at standard terrestrial conditions. That number is a significant advance from the current record of 40.7% announced in December and demonstrates an important milestone on the path to the 50% efficiency goal set by the Defense Advanced Research Projects Agency (DARPA). In November 2005, the UD-led consortium received approximately$13 million in funding for the initial phases of the DARPA Very High Efficiency Solar Cell (VHESC) program to develop affordable portable solar cell battery chargers.

Combined with the demonstrated efficiency performance of the very high efficiency solar cells’ spectral splitting optics, which is more than 93%, these recent results put the pieces in place for a solar cell module with a net efficiency 30% greater than any previous module efficiency and twice the efficiency of state-of-the-art silicon solar cell modules.

As a result of the consortium’s technical performance, DARPA is initiating the next phase of the program by funding the newly formed DuPont-University of Delaware VHESC Consortium to transition the lab-scale work to an engineering and manufacturing prototype model. This three-year effort could be worth as much as $100 million, including industry cost-share. Allen Barnett, principal investigator and UD professor of electrical and computer engineering, and Christiana Honsberg, co-principal investigator and associate professor of electrical and computer engineering led the research. The two direct the University’s High Performance Solar Power Program and will continue working to achieve 50% efficiency, a benchmark that when reached would mean a doubling of the efficiency of terrestrial solar cells based around a silicon platform within a 50-month span. The highly efficient VHESC solar cell uses a novel lateral optical concentrating system that splits solar light into three different energy bins of high, medium and low, and directs them onto cells of various light sensitive materials to cover the solar spectrum. The system delivers variable concentrations to the different solar cell elements. The concentrator is stationary with a wide acceptance angle optical system that captures large amounts of light and eliminates the need for complicated tracking devices. Modern solar cell systems rely on the concentration of sunlight. The previous best of 40.7% efficiency was achieved with a high concentration device that requires sophisticated tracking optics and features a concentrating lens the size of a table and more than 30 centimeters, or about 1 foot, thick. The UD consortium’s devices are potentially far thinner at less than 1 centimeter. This is a major step toward our goal of 50% efficiency. The percentage is a record under any circumstance, but it’s particularly noteworthy because it’s at low concentration, approximately 20 times magnification. The low profile and lack of moving parts translates into portability, which means these devices easily could go on a laptop computer or a rooftop. —Allen Barnett Honsberg said the advance of 2 percentage points is noteworthy in a field where gains of 0.2 percent are the norm and gains of 1 percent are seen as significant breakthroughs. Many of us have been working with programs to take us to a real photovoltaic energy future. This project is already working in that future. DARPA has leapfrogged the ‘conventional,’ demonstrating that creativity and focus can significantly accelerate revolutionary research-bench concepts toward reality, demonstrating this does not have to take decades. This is a first step—but a significant one in making sure our energy future is what we know it should look like. —Lawrence L. Kazmerski, director of the US Department of Energy’s National Center for Photovoltaics at the National Renewable Energy Laboratory Barnett and Honsberg said that reaching the 42.8% mark is a significant advance in solar cell efficiency, particularly given the unique small and portable architecture being used by the consortium and the short time—21 months—in which it was developed. During the first 21 months of the VHESC program, a diverse team of academia, government lab and industrial partners, led by UD, was focused on developing the technology basis for a new extremely high efficiency solar cell. The rapid success of that effort has enabled the present transition to a focus on prototype product development. The team’s approach provides for affordability and also flexibility in the choice of materials and the integration of new technologies as they are developed. Barnett credits the early success of the program to the team approach taken to solving the problem. Partners in the initial phase included BP Solar, Blue Square Energy, Energy Focus, Emcore and SAIC. Key research contributors included the University of Delaware, National Renewable Energy Laboratory, Georgia Institute of Technology, Purdue University, University of Rochester, Massachusetts Institute of Technology, University of California Santa Barbara, Optical Research Associates and the Australian National University. The newly formed DuPont-University of Delaware VHESC consortium will be made up of industrial partners, national laboratories and universities. (A hat-tip to Marty!) Resources: ### Comments I have a similar idea (its a bit more complex), that is moving towards patent or two. I can see the attraction of completely solid-state PV for small mobile applications such as laptops and satellite phones - including those used by the military. They should also prove useful for stationary applications too remote to connect to a power grid, e.g. meteorological data collection points. For bulk electricity generation, my hunch is any system that can harness solar radiation in the IR spectrum in addition to visible light will end up being cheaper. Heliostat arrays that feed high-intensity PV panels cooled by a secondary Kalina cycle. This si very good progress. Solar energy as an augment si wonderful. But it only confirms the danger of Solar Energy for wide spread applicationsn. To provide the elctricity for the curent load of the the USA alone, requires a substantial area. When you do some simple calulations it reveasl jsut how much is needed. You would need to pave an area slightly larger than the State of Texas to generate electricity, and in doing so, kill every living thing there as well. Stan, just put PV panels on rooftop, parking lot covers, or desert areas, and nothing has to die to support our energy addiction habit. Don't insult the size of the State of Texas, Bush and Company won't like it! An area the size of a much smaller state would suffice to cover all our electrical needs, which would be about the total size of all already occupied areas. Why is this dangerous Stan? The higher the percentage of the sunlight that gets converted to electricity, the lower the percentage that gets absorbed as heat by the panel, and the less the local heat island effect. Could you please explain what is it that scares you so much, and back it up by some calculation? Hopefully, this degree of high efficiency would translate to lower cost and faster manufacturing rate per Mw power. What is holding back solar PV now is the high cost and low manufacturing rate not keeping with soaring demand, hence escalating prices. The high efficiency would also lower installation cost per kw since less area would be needed. The articles does not address any cost and availability concerns that are holding back PV panels right now. Great news--the solar revolution gets closer every day. (No sarcasm intended.) Has anyone done calculations to find out what happens if we use a LOT of solar PV, in terms of reducing atmospheric warming? I have a hunch this is one of those circumstances where even a small percentage of rooftop area covered with panels would still have a measurable effect. (Remember the studies that showed the temp. increase in the US when all flights (well, most) were grounded right after 9/11 and there were no contrails blocking the sun? How many rooftops would need solar panels before we approached the same area?) The article does in an indirect way, relate to costs. There are a number of firms that are working on better concentrators and heliostats, and all of them are planning on using the 40% efficient cells from Boeing, unless something better comes along. Concentrators can reduce the amount of PV material needed by about 1000x. The question then becomes, can these new cells tolerate the heat? This is very good news. I have Kyocera solar panels on my roof and they are only about half as efficient as these are. The sooner these get to market the better. Still the panels that I do have supply all the electricity to re charge my electric motorcycle every day. I have no need for dirty coal power or gasoline to run my Electric Vehicle. Today I test drove a new vectrix motorcycle. It cost about 3 times as much as my home built conversion, but it is really a nice bike. It is very quick off the line and gets to the top speed of 62 mph right now. It was a blast to drive. See http://www.vectrix.com for details on this bike. The more electric vehicles we can get on the road the sooner we will solve the air pollution problem of our cities and the sooner we can solve the global warming problem. Excellent Progress. Last year, it seems Solar PV had 40 % growth rate. Still the companies have not reached volume production to reduce the prices below the$ 5 / Watt range.

When it hits $4 or below, large scale usage could follow. So far, it was used for minor applications like Calculators, Accent lights, Street lights, traffic lights, etc. Only now, its moving to power the grid. Again Germany is the starter in this regard. Hope it reaches the scale with this type of efficiency. I heard a quote that an area 100 miles by 100 miles in the Nevada desert could supply ALL the U.S. energy needs. Presumably, with these higher efficiency cells, that area would be smaller. Rough calculations put the cost of such a system at about our GDP, or over$10 trillion dollars, but it could be done.

"Danger" of solar energy....give me a break! Solar is (one of) the ways to go. With PV we can shave our peak daytime loads locally and with solar thermal in desert areas, we can develop an emission-free baseline or peak power alternative to fossil fuels or nuclear. Only a "danger" if you are stuck on a non-renewable energy solution.

Thin PV panels are already $3/per watt but they take up more space because of lower efficiency. Applied Materials says they will be able to get panels down to$1 per watt.

Even at that, however, you still have the inverter, cables, and balance of system. For really large, centralized systems you would then have to add distribution costs.

In any event, solar doesn't have to provide all our electricity, so I find these debates about how much land we need to power all our "needs" a bit artificial. Shrink our "needs" by 25% with conservation and efficiency, scale up wind power, wave power, geothermal, throw in a bit of nuclear and a future low carbon world is feasible. As long, however, as we keep building more coal plants as if that should be our energy future, we will not get there.

As long, however, as we keep building more coal plants as if that should be our energy future, we will not get there.

I could not have said it better myself. In my area electricity from dirty coal power plants cost 8 cents per kWh.

Renewable clean power from wind costs 10 cents per kWh. It is only a 2 cent difference however as long as there is an incentive to be penny wise and dollar foolish, people will do that.

If we really want to breath clean air, all we have to do is tax the pollution that comes out of the smoke stack.

For example if we taxed carbon emissions at the rate of a penny per pound it would only raise the price of electricity from 8 cents to 9 cents, but it would cut the cost difference by 50 %.

If we did that today and scheduled another increase in a year of another penny per pound then coal power would cost the same as wind power and there would not be any incentive to use dirty power any longer.

The revenue from the carbon tax could be used to subsidize electric mass transit ( light rail ) and solar power and geo thermal power. Only when we get off the fossil fuel addiction will our air be clean and our future be bright.

Petroleo,

The Albedo is the percentage of incoming extraterrestrial energy that is reflected as opposed to being absorbed. Over time, the Earth has come to a near balance. Altering the Albedo alters the balance formed and that will heat or cool the Earth.

Tropospheric cloud tops being white, reflect almost 60%. The ground is a near "blackbody" radiator/absorber at around a little less than 30% on average, as an Albedo.

But the ground similar to the cloud tops, is a "passive" absorber and a pretty good insulator. So heat absorbed on the surface does not penetrate too far, and the soil temperature less than a meter down is near constant. All of what comes in, is re-radiated out at other frequencies, except for the residual remains. What remains, (after bumping around in the GHGs), establishes an equilibrium. That equilibrium is the temperature of the Earth.

A solar converter is not a "passive device" at all. It is an "active device" that tries to absorb all the incident energy it can, and convert it, sometimes to heat sometimes to electricity, and to pipe it off somewhere else.

The higher the solar cell "efficiency" the more it does not behave as a "passive device" with an Albedo of say 30%. A 40% efficient solar cell really is 40% "Blacker than Black". It has an effective Albedo closer to 18% (30% x (1-40%)) = 18% or so. That my friends is a source of genuine GLOBAL WARMING, potentially.

Unlike the passive ground re-radiating what comes in, the active Solar cell constantly acts as if it were colder and always absorbs more energy than it re-radiates, (when connected in a circuit).

The Second Law says you don't get something for nothing. The electrical energy flowed off, is not free. It is eventually manifested as Work or Heat; warming the environment; and increasing the temperature. Meanwhile the solar cell is still busy absorbing more and more incident energy, never coming into balance.

It is no big deal for small increments of solar energy, but as soon as you talk of Energy matching the quantities that we now consume, around 90 quads/annum, the areas needed to devote to Solar energy collection, become vast, quickly. That is just because the energy intensity is just not very high to draw on. The energy flux at the Earth's Ground surface is around 340 W m**-2 on average, if I recall.

The Second Law of Thermodynamics, is the conservation law that outlaws perpetual motion machines, and says everything you do has a cost that must be paid.

It is sometimes quoted irreverently as "..You can't get there from here...", or "... No matter what you want to do, can't be done easily, or sometimes at all... ".

In any case it applies here. Harnessing solar energy has a cost that must be paid, just like any other activity.

All I wanted to point out, as in 1970, is that there is no "perfectly good" non-polluting, renewable, or non-renewable, energy source. Solar energy has warts just like every other energy source does.

IPCC Cassandras would have a fit if you showed them a source of disturbing the present energy balance by several watts per square meter, on vast areas. All the anthropogenic GHGs effects might alter the energy balance by portions of but a single watt per square meter, and the whole controversy swirls on the size of that tiny portion.

Many environmental movement types have no idea of consequences, or the tenants of the Second Law of Thermodynamics.

They may even have graduated from college, bypassing the hard Science stuff, and majored in God or Law or Politics, for example. One such semi-educated scientific illiterate, runs about the country side, even now. They have been told that:

Renewables are good! Wind is perfect. Solar is perfect. Nukes are bad. Coal is bad. Oil is Bad!

The reality is just not so. ALL are NOT perfect. Some are just worse than others.

We have more experience with attempting to harness the Wind. So the inevitable warts are beginning to show with Wind, and permeate the mass consciousness. Wind farms consume lots of land, and iron, steel, cement, and other resources to build; don't produce much energy; do so only intermittently; and are ugly; and are totally un-economic without massive subsidies. (Pacem, populi.) And kill lots of avian biota.

I could speak to the actual worse consequences if Wind were widely adopted. Consider:

Harnessing wind energy interrupts the Earth's accommodation to unequal solar heating, since it is a sphere. Theoretically, this imbalance between hot spots and cold spots, when prevented of relief through winds, could get severe enough to create massive extreme weather events to relieve the imbalances. Meanwhile the hot spots and cold spots are different from what occurs now.

But Wind has been exposed, and will never constitute much of a threat, to create these extreme weather events, simply because it won't be implemented widely.

Solar still has the "perfectly good" label attached because it hasn't been used much ... or its warts exposed, as yet.

But it has Warts. They are potentially more severe than wind as the energy intensity harness-able, is even less than wind, wave, or falling water. So there are more unusable and rejected side effects; which means more deleterious side effects, per the Second Law.

Carpeting an area the size of Texas to obtain our current electrical needs, whether in one contiguous area or lots of little pieces all over, will create heat absorption areas, much more severe than that make the effect of urban areas on temperatures even now, minuscule by comparison. This would alter the climate at the very least. If done on a large enough scale enough it could create extreme weather events as the Earth tried to equalize temperature extremes.

Man and his nomadic shepherds, with their flocks have been accused of "desertification". This occurs when Man lets his flocks of animals overeat all the flora. That is a "active device" way of creating "Climate Change".

In scientific terminology the percentage of incoming energy remained the same; the percentage absorbed/reflected changed. And the Earth reached a new balance.

But un-controlled use of solar energy, by Man's munching herbivores, converting flora to fauna protein, could be said to have converted northern Africa, in prehistoric times, from a dry but green Savannah to a ... SAHARA DESERT.

All it took was ... merely reducing the Albedo.

I'd say creating a SAHARA DESERT might be construed to be a deleterious anthropogenic "Climate Change". Even Chernobyl, Nagasake or Hiroshima did not create a continental effect. Hence the need to... S.P.A.R.E. U.S. !!

(The Society for the Prevention of Albedo Reduction, in the United States.)

Stan,

What does S.P.A.R.E. U.S. have to say about vegetation?

i don't know the albedo of stans arsch, but he is arguing like a peakoiler with full of schit in his head;

"
The Second Law says you don't get something for nothing. The electrical energy flowed off, is not free. It is eventually manifested as Work or Heat; warming the environment; and increasing the temperature. Meanwhile the solar cell is still busy absorbing more and more incident energy, never coming into balance.
"

heat is dissipated at night very fast into atmosphere and then into outer space

Why is Stan Peterson still allowed to post here?

I'm curious what these cells are made of, exactly. Rare earths like indium, gallium, etc.. are in very short supply and will remain such. I've seen estimates that we have maybe ten years of indium left.

This is a great advance, but I fear the applications will be limited.

Avian biota? Funny how one can use all the smartest sounding words to communicate a dumb theory.
Please, s.p.a.r.e.u.s. (stop promulgating asininity respecting ecology upon society)

Hi stan: Outrageous again and also silly.

It would take only about 9000 sqkm of land area comvered with 50% efficient cells to generate all of our electricity, about 4000 billion kwh/year. You must have been using old data for a much smaller Texas. Add some serious conservation and efficiency (e.g. Cree's 100+ lumen/watt LED light) and we could start to replace considerable transportation fuels as well.

You would have us believe that changing the albedo of an area slightly would have more effect on warming the earth than using nuclear or fossile fuels to produce the same energy. Absurd!

Stan, a solar cell just moves energy to another location where it is converted to heat resulting in re-radiation at lower frequencies. There might be no albedo alteration at all, but even if there is a little, so what? No one in their right mind is proposing using solar cells for ALL energy needs, like space heating, for example. But then, I'm beginning to think that you just post nonsense here to see how many people you can annoy.

Lately, I have come around to seeing how pumped hydro and renewable energy could be a way to not have more coal or nuclear. At more than 70% efficient, if you had enough renewable electricity you could have enough pumped hydro to supply electricity during the night and enough distributed to take care of weather conditions. Maybe not 100% of our needs all the time, but maybe no need for more nuclear power than the 100 plants we have now and maybe no need for more coal plants. It seems like we leave it up to the private sector to find the cheapest and most profitable route for them and not the best route for the country. As if that was the only decision criteria we needed, profitability and not considering other factors.

sjc: re: "cheapest and most profitable" ... that's where a pollution/carbon tax comes in.

when can we buy such solar modules?

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