Cost-effective solar power module could also serve as an eco-friendly furnace


July 10, 2012

A dish-shaped mirror focuses sunlight onto a glass ball, which distributes it evenly onto an array of photovoltaic cells (Photo: Blake Coughenour/UA)

A dish-shaped mirror focuses sunlight onto a glass ball, which distributes it evenly onto an array of photovoltaic cells (Photo: Blake Coughenour/UA)

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Borrowing technology from sophisticated telescope mirrors as well as high-efficiency solar cells used for space exploration, a group of students and researchers at the University of Arizona is putting the final touches on a novel power plant that promises to generate renewable energy twice as efficiently as standard solar panel technology with highly competitive costs and a very small environmental impact.

Curved mirrors in solar power plants usually concentrate the sun's rays along a water pipe, heating the water into steam that is then fed to power-generating turbines. But rather than distributing the power over the area of a water pipe, researchers at the University of Arizona are working on focusing as much as possible of the sun's captured energy onto a precise point in space.

The target is a small glass ball that is only five inches in diameter. The ball contains a specially coated lens that redirects the light to an array of 36 small, high-efficiency solar cells, which were originally developed for space applications, that can absorb light over a broader spectrum than standard cells. And instead of mirrors shaped like a cylinder, the team had to develop dish-shaped mirrors that focus light onto a point.

Regents' Professor Roger Angel has pioneered a new way to make glass mirrors to concentrate sunlight to make electricity (Photo: Patrick McArdle/UAnews)

"By using mirrors to focus on small but super-efficient photovoltaic cells, we have the potential to make twice as much electricity as even the best photovoltaic panels," Prof. Roger Angel, who is coordinating the research efforts, commented.

Because the rays concentrate on a small area, the process generates very high temperatures – so high, in fact, that they could melt the solar cells in seconds. To prevent this, the team designed an effective cooling system, a simple combination of fans and radiators that keeps the solar cells within 36° F (20° C) of the ambient air temperature.

Each module features two highly reflective, curved, 10 by 10 feet (3 x 3 m) glass mirrors mounted on a steel structure. The module automatically orients itself toward the sun for maximum performance: in the morning it turns to the east, tracks the sun's path for the entire day and, after sunset, predicts where the sun will be rising and preps itself for the next day of clean, efficient power generation.

The "tracker" consists of a steel frame that ultimately will support eight mirrors, together generating enough electricity to power about four to five homes (Photo: Blake Coughenour/UA)

A prototype with only two mirrors was shown to generate 2.5 kilowatts of electricity – enough to meet the demand of two average U.S. households – but the team plans to place eight mirrors on each module.

The manufacturing process for the dish-shaped mirrors is going to be optimized for mass production to reduce costs. The materials used are relatively cheap and, because no water is required to generate power, the plant's environmental footprint would be smaller than that of a conventional solar panel-based plant.

"Our technology holds the promise of getting the price of solar energy down to where it can be used on a large scale without depending on subsidies and be competitive in the electricity market," Angel commented. He says that an array of sun trackers on an area measuring about seven by seven miles (11 x 11 km) would generate 10 GW of power during sunshine hours – as much as a big nuclear power plant – and suggests that the system could be deployed in deserts for maximum effect.

The researchers have already patented their process for manufacturing their curved, highly reflective glass mirrors, and the team is now looking to find new applications for this technology.

One promising prospect, which would require little adaptation, would be to explore the thermal properties of the modules. Because the temperatures achieved are so high, Angel's team plans to adapt their system into a novel, eco-friendly furnace that can melt glass within seconds. The researchers were recently awarded a US$1.5 million grant by the Department of Energy to investigate just such a possibility.

The video below illustrates some of the challenges the team faced in developing their system.

Source: University of Arizona

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion. All articles by Dario Borghino

Looks a lot like the stuff developed at Solar Systems in Australia nearly 20 years ago ... been installed for 15 years in the outback ..

Gordon Buchan

This is nothing new. Indeed, this concept has been around for fifty years at least.

Ross Nicholson

This is an interesting technology and may have some place in providing our energy. Still, does requiring 49 square miles (7X7) to replace a single power plant sound like a good idea? How many like that do we want built? A lot of people don't like nuclear, but it sure looks like the best option when you look at all the costs (economic, social, and environmental).

Bill Moore

Concept was around since 1939, using solar mirrors to generate steam driven power in the deserts of Egypt. Using salt based heat stores electricity can be generated over 24 hours with a solar concentrator using mirrors rather than just during daylight hours with the system mentioned. It is energy storage which is the biggest problem not the photovoltaic cells.

Also read Desertec - Energy for Everybody by Margaret Heckel. One of the best kept secrets of the energy industry is that it is actually far far cheaper to generate solar electricity in the desert and supply it to the north than by gas/coal/nuclear or photovoltaic panels. True also especially for the US which does not have security issues having plenty of its own desert areas ideal for generating electricity withing its borders.



Even the high efficiency solar cells are cost prohibitive. Run the light through a cube of fresnel lenses (external mirrors redirect the light at 90 degree angles) Use Freon misters within the cube to abosrb the amibient heat. Use the concentrated light to power a stirling engine. 40% yield at a fraction of the current cost.


2.5kw from 20sq yards at 1kw/yard solar input is only 12.5% eff.

Not much here worth much as better systems are already in place. Why would one waste the heat. Gathering and using the waste heat would increase eff several more x's.

Making a steam/Rankine engine with a small heat storage plus using waste heat could make 25% eff electric and 75% eff overall, soundly beating this.


1) solar thermal needs water and operates far more efficiently at scale than any other method.

2) concentrated pv is good ONLY because pv cells are too expensive and this is a method to make pv cheaper

3) pv can be distributed right near you house as opposed to solar thermal---electric-- which operates mostly at scales requiring large turbines to create the electricity

4) if this system is creating a lot of waste heat, they can power a small waste heat turbine to capture it , and use the runoff for heating homes. perhaps the mirrors can be foccussed to temporarily heat small amount of aluminum side panels of a house to capture and store the heat for home heating prior to focussing on the solar cells for generating electricity. extra heat could very well be used to process sewage and garbage on site by pyrolysing it. biomass could also use this heat for pyrolisis thus creating a source of biochar/fuel for other purposes/rainy days.

----it is a fact that the majority of energy we utilize winds up as waste heat rather than work.

5)----the idea of using pv cells for large central 'farms' in the dessert is decades away because it will not be economical anytime soon. SPENDING money on this , rather than on funding new designs and basic research---is a waste. thus, only private investors should risk these ventures, as opposed to government, that socializes the cost of wasteful investment.

6) technology in the are of pv's and mirrors and heat management are progressing rapidly . people are impatient but within a few decades or a hundred more years there will truly be a revolution in the economics of solar power, namely because once installed, these systems require far less labor to maintain--particularly as both inflation, and the increasing cost of maintaining the aging electricity grid starts leaking into the price of consumer electricity.


If they could make the plant small enough, it could placed as helping cell plants and also use the waste heat to run a solar water heater for buildings and nearby homes. Plenty of roof space on many of these mega box stores.


zevulon, CSP can be done eff in home sizes and where it is most eff, near where it is needed.

PV panels are only $1/wt-$1k/kw retail so hardly expensive anymore if well shopped.


Another challenge with concentrating photovoltaic systems is the need for minimal cloud cover to operate at peak efficiency. The sun no longer acts as a point source to focus onto the cells when there is cloud cover that is diffusing. Not as much an issue in southwest climates but in many areas this has to be considered in the average power the system can generate over time.

I think that the process of exploring this design space with rigor is important so it's great to see universities working to refine these products withteh full life cycle in mind.


Their reflector design is poor. They should use a mirror that reflects the light off to the side so that none of the reflecting surface is in shadow.

I would use Solar water heaters powering an absorption refrigerator and put the Sterling cycle engines to use the waste heat and cold to produce electricity.

re; zevulon 1) Solar thermal does not "need water". You could use a hydrocarbon liquid such as kerosene in a Rankine cycle engine (steam), a gas turbine that uses solar energy instead of a combustion heat source, or use Sterling cycle.

3) While Rankine cycle engines benefit greatly from economies of scale, Sterling cycle engines perform well in the kilowatt range.

5)Do you really think that the government should make intentionally bad investments simply because it would then be spread out over all the taxpayers?


Keep it simpler... Build a solar concentrator plant in the Sahara that heats up molten salts and such. Load them on a ship that has a power generator in it, and sail to every coast of Europe. Throw a cable to shore, feed electricity until heat runs down. sail back to Sahara. profit!


re; Paucus

I hope that was snark because there is not enough energy density to make that work.


Use solar to make hydrogen. Hydrogen can easily be oxidized or used in a fuel cell thus is compatible with our current infrastructure.

We should be moving towards a world powered by hydrogen, with the hydrogen produced by nuclear or renewable energy.

Our single biggest problem is that we have no real means to store electricity.


Slowburn, are you sure? How much fossil energy would it take to heat up a huge mass to 500 or something? With that heat you cannot make steam for electricity? Some other material like sand, concrete, metal, or something? Even the ship could run off that and not burn fuel. You could transfer that mass to shore instead of having the generator on the ship. You could move it by rail in other places. What density would you need? If there are generators that work off the temperature difference in top and bottom layers of the sea, surely this has a bigger differential...


The only important fact not clearly defined in all the preceding comments is that it is MUCH CHEAPER to store the waste heat as, well, heat than to try to transduce it into electricity to then store in expensive and relatively inefficient batteries. So, run the PV cells but cool them with a liquid heat transfer fluid which is then "chilled" in a large phase change salt heat storage device. Nothing at all new or significantly expensive or challenging to engineer here. When further energy is required appropriate controllers draw down the heat and transduce it into electricity for delivery to the local grid. The machinery and materials required are all well known, characterized, relatively inexpensive, and most importantly, absolutely durable & recycleable.


re; Paucus

First. The heat storage medium while liquid while hot it is solid when cold. Whether you heat the storage medium in the ship or remove the salt compound as a solid it lengthens the time the ship must be in port, increasing the overhead. Second. The heat storage medium must be shipped both ways. Purpose built oil and coal ships get much better mileage when running empty. Third. Heat is hard to store the greater the differential the faster heat travels. How long does it take for the coffee to cool off in a thermos? (vacuum bottle) Not that any of that matters, compressed to liquid CO2 is safer and can be moved by pipes and most importantly can be stored for years rather than days and weeks.


@; Paucus In your defense against Slowburn,

The Heated Salt would be stored in a vacuum flask, a cartridge similar to a standard container but floated out of the vessel approx the width and height of the hull. It would never leave port but would power a steam power generator there until exhausted. This is the sort of thing Japan may want due to the problems of laying power cables over active volcanic regions.

The ship has brought its own power from the desert, like shipping coals from Newcastle to London, burning the stuff on route is not a problem as you resupply when you return. These ships will be powered by their energy cargo.

The surface area is a square value in relation to volume, with a bigger cartridge, less internal volume is exposed to heat transfer.

Liquid CO2 is a highly dangerous and hazardous substance also CO2 also is incredibly energy intensive to store - you have had to capture, compress as well as cool it below 820 psi it also needs to be kept at around 40 F. A major undertaking to make a safe ship sized pressure vessel. A heat store is far safer - instead of endangering the ocean for miles around - perhaps as far as 100 miles inshore in a disaster through oxygen deprivation - it only endangers the ship itself.


re; L1ma

Very large vacuum flasks are hard and expensive to build.

I did not say you could not power the ship that way only that the shipping the cold storage medium would cost a lot more than moving an empty ship.

4a. Liquid CO2 can also be moved by pipeline so obviously the shipping terminal can be built well out to sea. b. The waste from the compression and storage of CO2 is heat. Isn't that a power source as well? Even in deserts there is cool earth only a few meters down. c. One of your vacuum bottles springs a leak that lets in water you could get a steam explosion sink the ship and dump a load of toxic salts to poison the water for centuries. d. Lake Nyos which triggered the sudden release of about 1.6 million tonnes of CO2 had a death range of about 16 miles and that was with the heavier than air cloud moving down hill.

Incidentally using temperatures warmer than is used in the shipping of methane you could freeze the CO2. Also if you happen to have a non compressible liquid that you wish to move the other way can transfer them simultaneously and save a lot of energy especially if the heavier fluid is moving down hill. (This also works with High pressure gasses.) There is a fair market for fresh water in the desert and they might not be apposed to treating sewage to get it. you will want to have a membrane between the two fluids.


Re; Slowburn

No go to your arguements - the only economic use of liquifaction of air products lies in their use in industry not as an energy storage medium. If we must use cryogenics it would be to freeze a ship sized capacitor using a superconductor to hold charge (i.e. Type 2 YBa3Cu4Ox 177K) which is held within a liquid Nitrogen bottle.

You are incorrect about the effects of Asphyxia and the environment around the volcano did not have the amount of released CO2 measured. This is not known, it is a guesstimate after the effect.

A release of liquid CO2 gas from a stricken ship would be explosive not gradual, CO2 is heavier than air, would initially cause a plume which would be wind and gravity driven and disperse slowly. Its effects are very simple to describe, it would flow into every depression, river channel, hole, boat and open topped car and simply stay there building concentration as it displaces the lighter gasses. You would be perfectly safe upstairs, but would collapse as you descend. It is odorless, colourless and is a killer at 40,000 ppm of atmospheric concentration. It would take considerable time to disperse without high winds. Inside the plume it would be raining pure CO2 for several minutes.

At least the Gas carrier ships have a cargo which can be detonated for public safety reasons.


Why do we need to build this ini a desert? One needs to research what environmental effects building structures in the desert will have on the animals, insects, plants, rainfall etc.

We have massive cities with highrise buildings. Why not use the rooftops ?


re; L1ma

If you are going to use superconductors build a cable and send the electricity directly.

Yes scientist who studied the lake, the kill zone, and the volcano and then made their calculations made an estimate.

Co2 may be colorless and odorless but it causes a burning sensation in the lungs at well below lethal concentrations.

The rate of leakage is dependent on the size of the hole, and again being able to be transported by pipe mean that the shipping terminal can be well out to sea.


@ Shavanator

Gizmag has some wonderfull articles with exactly that theme with actual developments, however the answer is simply costs and efficiency. Currently I am in Manchester, England where it has been raining nearly non stop all year - averaging at 140 rainy days per annum it has nearly 1/3 rd the sunny day efficiency of the Sahara desert with 365 sunny days, and the Sahara has averaged 2200 kWh/ m2, 2 times the light intensity of the UK at 1000 kWh/ m2 - i.e. the energy a kettle or small electric fire, for 12 hours a day in the area you can shape your arms into a L shape in. And that small area would be able to power your entire energy needs throughout the year with storage.

So you can put all your most expensive energy collectors on rooftops say in Holland or Kansas or the same ones in deserts on the equator and lose 3% power over 1000 miles of tranmission line but have 3 times the collection time each year and 2 times the power input from the sun. Your choice.


re; L1ma

So Dubai, Cairo, Addis Ababa, Tripoli and such aren't cities.


Re; Slowburn re; L1ma "If you are going to use superconductors build a cable and send the electricity directly." - stated in Desertec that at a 3% loss rate per 1000 miles a modern power line is capable enough.

"Co2 may be colorless and odorless but it causes a burning sensation in the lungs at well below lethal concentrations." - Its use would be against HSE regulations in Europe and the US with our current technological level there is no way of handling up to 250000 tonnes of cryogenic gas in an emergency.

"The rate of leakage is dependent on the size of the hole, and again being able to be transported by pipe mean that the shipping terminal can be well out to sea." The use of cryogenic storage means your Co2 will be under pressure - in a you wont believe it - vacuum flask storage bottle containing around 50000 tonnes of liquid co2 at 820 atmospheres.The usual loss of such a ship is due to a loss of power due to collision or mechanical failure. This usually means there is no longer power to keep a vacuum in the pressure vessel, use refrigerants or keep station meaning that liquid is now boiling off, its been known for crews to keep quiet about an emergency for a week before a tug gets to the ship.

"re; L1ma So Dubai, Cairo, Addis Ababa, Tripoli and such aren't cities. " ????????? you come out with some tosh for the sake of devilment in this mag.


re; L1ma

First paragraph. Using the superconductor cable was the response to the truly ludicrous idea of shipping electricity on a ship stored in a capacitor. At a 3% loss moving the energy as electricity beats any other method of transporting solar energy except use of superconducting cable. however that 3% loss is over what distance.

Second paragraph. A physical symptom that warns that CO2 concentrations are elevated beyond acceptable levels is a violation HSE regulations in Europe? Can you still buy non alcoholic carbonated beverages in Europe?

Third paragraph. An estimated 1,200,000 tons of CO2 released from the water of Lake Nyos had a death range of about 16 miles and that was with the heavier than air cloud moving down hill limited to 2 valleys. Therefor a release of 50,000 tonnes (55115.565 tons) less than 5% of the Lake Nyos release no larger than a 16 mile radius to make it safe to the general public.

Forth paragraph. At 820 atmospheres CO2 will be a liquid well into unreasonable temperatures so no vacuum flask. Using a vacuum flask implies either chilled to liquid or colder -70°F or -57°C at a pressure of less than 6 atmospheres or frozen solid -109°F or -78°C. Sense we are using cold we could just fill the space between the double hulls with polystyrene foam and we'll need a nice thick layer on top as well but it will be cheaper than vacuum insulation needed for the heat system. A collision that puts a major leak in a liquid CO2 tank use your last seconds to send out a warning to stay away from the area for a few hours, and make your peace with god unless you have oxygen masks and warm clothing. With chilled to dry ice your odds of survival are pretty good you might even plug the hull breaches with water ice. For mechanical failure with compressed to liquid CO2 no leak, with well insulated cold storage the venting gas will be at less than asphyxiating concentrations because the boil off will be slow.

And the last. Your answer to why the solar has to be in the desert assumed cities in northern climates and as far as it went I agree but while in full snark mode I was pointing out that you don't have to use virgin desert.

I introduced the Compressed to liquid CO2 transportation of energy to point out how bad an idea shipping a heat storage medium is. If i was producing electricity wildly in excess of need and could not put it on the grid I would either encourage high energy manufacturing or using catalysts produce liquid hydrocarbon fuel from water, air, and electricity because transportation is were the real energy loss will occur.


Re; Slowburn

Desertec - Read the book. Then you get to critizise it - however seeing as the main protongoist is a physicist Gerhard Knies you better raise your standards.


re; L1ma

Are you saying we have to put solar plants in virgin desert, we can't build it in places that the native ecosystem is already destroyed?


Re; Slowburn

"Are you saying we have to put solar plants in virgin desert, we can't build it in places that the native ecosystem is already destroyed? "

See definition of Desert

CO2 is a class 2.2/2.3 hazardous material, to refine enough to produce 250000 tonnes would require 975 ^ 10 tonnes of liquid air. Already every plan to carbon capture from fossel fuel stations has been abandoned due to costs. No'one wants the technology or the insurance costs when it is plain there is and will be no need for it. Given your cargo - the CO2 costs currently $68.75 per 100 lbs to refine and store, it would cost $37891951281.25c to send one 250000 metric tonne shipload of the deserts energy to its destination - a cargo which would have to be released into the atmosphere. At least its carbon neutral - to put this in context a new nuclear power plant can be built for around $14 billion.


re; L1ma

I have seen the definition of desert I have also seen National Geographic specials showing the plants and animals of the desert. I have seen the results of gross mismanagement. Bedouin nomads digging up the roots of the plants that their goats just ate down to the roots for firewood springs to mind. But so does overgrazing and removing windbreaks.

According to CO2 is an asphyxiant gas and not classified as toxic or harmful in accordance with Globally Harmonized System of Classification and Labelling of Chemicals standards of United Nations Economic Commission for Europe by using the OECD Guidelines for the Testing of Chemicals. In higher concentrations 1% (10,000 ppm) will make some people feel drowsy.[77] Concentrations of 7% to 10% may cause suffocation, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.[79]

When venting CO2 you have to keep the atmosphere concentration under 1% CO2 this is not a difficult engineering task especially given that in emergency you could on a short term basis (A month or less) go as high a 3% without lasting harm.

If you had read my comments in their entirety you would have seen that I don't think carbon sequestering is a good idea it is just a better idea that shipping vast quantities of toxic salts heated to over 500°C.

Using the term 'carbon footprint' in a paragraph that assumes that you will get to build a nuclear power plant is ludicrous.

Cost is negotiable with free energy (solar) and a fully automated plant, compressed to liquid CO2 could be very cheap, especially if the local currency is toilet paper and you are selling it for something hard. Make it $15billion and I build it on a ship and lay 300 miles of transmission wire to shore.


Re Slowburn;

What carbon footprint ?

What carbon sequesting ?

At what point are salts toxic to non mammal marine life, and at which point if the worst was ever to happen the now cold hard lead oxide or (Aluminium) sodium dioxide bricks would not be recovered, that is the heat storage medium, not reactive at all.

Post combustion CO2 takes 65%- 85% of the usual power output of a coal plant to render pure CO2 gas at 1 atm into liquid CO2. The solar power station in the desert would have to be 2-3 times larger than necessary compared to heat capture, and each one have cooling towers,and compression plants to capture 'pure' CO2. Since CO2 atmospheric levels are at 0.037% your concept is 97% less efficient than you believe.

Any Gas is a good potential energy storage medium - compressing it further - in the case of CO2 too 55.81 atm (820psi) means it stores 12045.8 lb-force/in2 as potential energy which is where the energy is properly stored. Storing at near dry ice temperatures as you would have done only serves as a method of CO2 transportation, it would only release CO2 gas at < 5 atm (73.45 lb-force/in2). To get the same energy transportation as a high pressure vessel you need to transport 165 times the amount of CO2. I already knew about all this long before you started, which is why I dragged in the safety aspect - to be economic it must be high pressure storage.

But if you are so fixed on extracting CO2 for some strage unfathomable reason - you missed out out the other 97% of the Atmosphere which compressed to 55.81 atm would also have stored the exact same energy without any disfavourable drawbacks. The medium by which energy is transported is less relevant than cost of plant, safety, transportation and the cost of the medium itself which with CO2 is astronomical.

I have said everything relevant - thanks peeps.


re; L1ma

MY mistake but carbon neutral, carbon footprint both outgrowths of the overrated and disproven hypothesis of AGW but the people who believe it are for some reason death on the one energy source that could be used to take coal, oil, and natural gas of the table in the next five years without massively reducing the first and second worlds standard of living. So using carbon neutral in a statement that assumes that a new nuclear power plant will be built and operated is ludicrous.

There is no evidence that leaked thermal storage medium would remain in large chunks and the toxicity affects a far larger area and are longer lasting than a catastrophic C02 release.

While collecting C02 from power plants gives you high percentages of C02 but it is hot and is still significantly contaminated with some nasty chemicals even after smoke stack scrubbing and the whole fractional distillation of liquid air method of separating gasses it out dated; molecular sieves and Pressure swing adsorption work just as well and use far less energy. You assumed with no evidence either way that the rest of the air would be just thrown away not used locally. You also forgot about the phase change. At room temperature compressed to liquid C02 contains significantly more energy than an equal volume and pressure of compressed air. This is why paintball warriors typically use C02 rather than compressed air. for a given number of shots the C02 tank is significantly lighter this also greatly affects shipping cost. The pressure required to liquify C02 varies greatly with temperature. If you heat a sealed tank of liquid C02 to over 100°F (37.7778°C) the pressure will rise to over 1400psi. But if you lower the temperature to -20°F (-28.88889°C), something that is well within the reach of a ammonia based absorption refrigerator that can be powered by solar water heater or wast heat from compressors, the pressure will be under 218psi this will improve efficiency tremendously. Just for clarity the temperature that the liquid C02 is stored and shipped does not reflect the temperature that it used at. Also look up how water is injected into boilers of steam engines.

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