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May 03, 2008



It looks like these produce a lot of heat as a consequence of the concentration of the sunlight and the big heat sinks off the back of the cells. I wonder if there is some way to pull the heat off for heating or domestic hot water. It would be like solar CHP.


The math doesn't support the statement of 175% more for a tracker. Since the area on a circle versus a sphere is .25, a horizontal surface at an "average" location will receive half as much energy as a tracking planar surface. A fixed tilted surface, which is common for many PV arrays, will do better than that 50% figure (not counting the diffuse light). So the best I can believe is that the tracker might intercept 1.75times the sunlight of a fixed planar array. They should have said 75% more not 175%. Ted: There have been announcements of new thermoelectric materials. Thermoelectrics can convert thermal gradients into electricity, and the reverse process has been used in some niche cooling applications -including consumer automobile refrigerators. I have yet to see any figures on cost, power output, or efficiency for any of these devices however. In theory at least, one could use a thermoelectric device between the PV cell, and the heat sink to further improve the overall efficiency of such a device. But again data would be needed to evaluate whether such an improvement actually makes sense.

Benjamin Cole

I hope it works.


news articles are saying that without the heat sinks, the cells would hit extremely high temps - enough to melt the cells. That's alot of heat - you would have to think that Sunrgi would be trying to make these cells twofers - you get electricity and hot water from the sun from one package.

Nigel Kee

looks almost identicle to green and gold's suncube, who would appear to be further along the manufacturing and commercialisation path. it would be fun to put these two side by side and calculate the real world c/kWhr.

Bob Wallace

I'm not sure that the overall amount of heat is all that great and would provide a significant energy source. It's just concentrated on a very small point/piece of silicon.


Bob you are right. There is only so much radiant heat per square foot of sun light. Concentrating the light increases the temperature at one point but does not increase the heat gain per unit area.

Looks a little too good to be true. I hope their cost assumptions work out.


I think these are targeted at smallish commercial/utility scale plants. The opportunity for combined heat and power is probably not that great, at least for initial implementations. Since the collectors are mounted on trackers, some sort of flexible hoses would be needed to connect to the unit. I doubt it would be worth the cost -or the risk of a leak. One advantage CPV has over concentrated solar thermal, is that it doesn't require water. Most areas that are favorable for large scale solar thermal don't have large amounts of water available. I think CPV and concentrated solar thermal could be used in a complimentary manner. The former provides instantaneous power, with sufficient thermal storage the concentrated thermal could be used for dispatchable and baseline loads.

Cyril R.


Dry cooling is commercially available technology at a small increase in cost. And there's promising new technology being developed now, as you can see here However, some water is needed for cleaning the mirrors; same for the CPV lenses. But this is a comparatively small amount.


Efficient heat engines require high temperature; PV active materials don't like that. Low temperature thermoelectrics are a different principle, but so far they are horribly inefficient, and even developments in the pipeline don't claim reasonable efficiencies, so it's likely they will be inefficient for quite some time to come.

A possible solution would be beam splitting technology, where wavelength selective 'membrames' divert the infrared part of the solar spectrum to a heat engine and the other wavelenghts towards a PV device. This allows the PV to operate close to ambient temperatures even at very high concentrations, while allowing high temperature heat for efficient heat engine operation.

power user

Why would anyone one want to develop a 5 cents/kwh power, while the idiot premier of Ontario is eager to pay 42 cents/kwh.

tom abrahams

kind of a layman's approach on my part...but i'd love your thoughts on all of the gas tax relief talk on the presidential trail:



Actually claims like this have been fairly common in the PV industry over the last 20 years. You're just noticing them less because there are now quite a number of companies making realistic claims that are actually credible. BigTom points out their claim of 175% is misstated or false. If they have a 5 cent/kWhr cost estimate without a working prototype, then it is based on vaporware. It may remain vaporware or may get converted into reality. I hope the later ends up being the case. More often you see later complaints that reality sucks. Design looks simple enough to be cost effective. Might be worth something.
175% claim and 5 c/kWhr based on design work only. Count me skeptical for now.


power user,
LMAO It's called profit margin, dummy.

Mr. Abrahams,
McCain is a Republican who doesn't believe in supply and demand helping to solve problems? Hillary will say or do anything to go with the way the wind is blowing that day! Aren't we already subsidizing oil enough with the war in Iraq? Leave oil/gas prices as they are. Subsidize HEVs, PHEVs, E-REVs, and EVs. Subsidize Nuclear, Solar (PV, CPV, & CST) , Wind, Geothermal, Wave Power, and maybe Tidal. Subsidize Conservation and LED lighting. Subsidize new battery technologies and other energy storage technologies. Subsidize cellulosic ethanol and algal biodeisel. Those are technologies to get us out of the mess we are obviously in. Lower taxes on gasoline and increase our consumption of oil? These are presidential candidates saying this? Maybe they should just share some of that bizzaro punch with the rest of us.

Increasing electric transportation (HEV -> PHEV -> E-REV -> EV)...powered by Solar, Nuclear, Wind, Wave, and Geothermal is the answer.

The time is now.

Keep oil prices from collapsing the economy while this transition gets going faster, fine. Cheap gas for the holidays is not a human right and it's counter productive, literally.


cyril: When I said CPV and CSP were complementary, I didn't mean to imply they use the same sunlight. I should have said, CPV and CSP with substantial storage for the later component, connected to the same grid are complementary. Ironically the place where (ignoring clouds) tracking versus fixed array would have as great an advantage as their figure of 175%better is at very high latitudes -this might be useful for places like the base at the south pole (it is very expensive to fly in fuel). But that clearly isn't going to be a large market.


Sorry, I must be grumpy today.

175% better might make sense if they are comparing their product to 20% efficient Si panels fixed to a flat roof.

Also, if they really can get this high concentration to work reliably it's conceivable their product could be low enough in cost. I don't know. Even if they just make 8 or 10 cents / kWhr this would still be a great product for much of the southern USA. It would be killer for Hawaii.

I wish them luck as well.


Excellent site here.

Hope you don't mind I added you to my blogroll.

Keep up the good work and I have you listed for my daily reading.



mds: The way I read it their claim of +175% was for tracking versus non tracking. The other factor of two comes from using multijunction silicon, such as those made by Spectrolab, should be noncontroversial. The whole point of CPV is to use cheap reflectors to allow the use of high efficiency, but expensive PV tech.

Jennifer Cluse

Benjamin Cole yesterday said "I hope it works."

It does, Ben, and *is* being done in Adelaide Sth Aust now by Green & Gold Energy with owner/inventor Greg Watson's development, the SunCube. Not an 'extreme' version yet, which it is only a proposal to date, but using current but leading edge technology in a tracking Concentrated Solar Voltaic (CSV) unit. See < http://www.greenandgoldenergy.com.au >, updated often.

Due to the extreme *demand* they have firewalled themselves behind their distributors, who in Oz, NZ & the Pacific are Zolar Distributors. See < www.zolardistributors.com > for tech information.

Three highly robotized factories planned in Oz, finance in hand, world wide demand.

It works!


The announcement and the report seem heavily slanted towards the rosy view of things. For example, the 175% advantage for a dual axis tracking system compared to a fixed plate collector only makes sense for Daggett, California if the fixed plate is oriented vertically
If the fixed plate was slanted south at 35 degrees the ratio would be 1.14%.


Jennifer: Does Green&Gold's Suncube have any relationship with Sungri? The SunCube has a superficial resemblance to it. Also wasn't there an similar thing called a Sunflower? The most elegant of these concepts IMO is the Solfocus device. Of course in the end it is not elegance that matters, but rather cost and reliability.

Benjamin Cole

Thanks Jennifer, for the info. I hope the Suncube works too. By this I mean a product not only works technically, but commercially, is robust and rugged, can be scaled up etc. As an amatieur, I also wonder why concentrating light (which means less light elsewhere) is effective.....I have also wondered when I see a large installation of solar panels, why they do not use mirrors to reflect more light onto the panels where practical.....


Their graph does look more like 75% more energy rather than 175% more.

* A dual axis tracking system that captures 175% more energy than a fixed system
* a system with less land area or "roof top" requirements than typical solar energy systems

I'm not permitted to put solar panels on dual-axis tracking systems on my roof, and all the photos I see of the Sungri panels don't show them on a tracker.
Is the tracker built internally inside the panels?

Maybe not. This page mentions "System simulation of multiple module arrays within a low-profile, horizontal, two-axis frame structure."
Too bad it doesn't say multiple dual-axis-tracking cell arrays within a low profile module.

Kevin b

If you expand the picture it kind of looks
like the heat dispenser from a computer processor if it was submerged in water to heat or pre heat your water heater it would probably be more efficient

Carl Hage

[I posted this yesterday, but it was flagged as "spam", presumably because I included links to all I referenced. I am reposting without links.]

The claims in the Sungri press release and web site do not make sense. The $.05/kWh cost is a theoretical number, without any substantiations on this claim.

I read over the web site, and now see what they've done and what they haven't done. Sungri is another manufacturer using the Spectrolab 1cm2 cells, originally developed for space applications. There are a number of other CPV manufacturers also using Spectrolab cells, e.g. Soliant and Solfocus

What Sungri has done is developed and tested a lens, cell mounting, and cooling plate, increasing the concentration from 500X @19W (the Spectrolab concentrator) to 1089X @28W and then 1688X @37W using the same 1cm2 cell. They use a Frenel lens, which would need to be about 42cm wide square. Supposedly the improved cooling system enables the higher concentration, so they could use half the number of 1cm2 cells as the 500X concentrators.

As far as I could tell, they have not actually built a mount and tracker, though other (competitor) companies make them. It looks like other than making a sample module, all else is a calculation (paper design).

Now for the claims. The 1cm2 modules cost $14 each with interconnect, $10 bare (at 10MW/year quantities). That's about $.40/w, not including the lens, heat sink, mount, and tracker and assembly cost. To get $1/w (Nanosolar claims to be making them at this price), then 40cm glass/plastic frenel lens, heeat sink and box, plus tracker would need to be less than $21. A plastic lens in 100 unit quantities costs about $20 alone. I wonder what the lifetime of acrylic is in sunlight-- would they need to be replaced after 5 years?

The tracker cost is a little hard to find. Current pole mounted trackers cost $2-4K holding 100-200ft2 (~20W/ft2 @37W/cell), so on the order of $1/W just for the tracker. I would imagine that some innovative mounts could be used to make a tracker much less expensive, but it still adds up. The 40cm buckets could be hung on a pivot in rows along bars connected to another pivot, mounted flat on the ground rather than using a pedestal.

I can't understand how they would get 175%. From NREL measurements, Daggett, CA gets 6.6 kWh/m2/day fixed tilt, 9.4 kWh/m2/day with 2X tracking, or 1.42X (+42%). However, that assumes you have 1 panel or a N-S line in an open field. If you put them next to each other in a grid, they shade each other in the morning or evening.

How do they get 16X area reduction? They assume 7% thin film, 15% Si, and 37% XCPV. So you get 5.29x over thin film, plus 1.42 for tracking or 7.5x, except to get 1.42 you have to space the units apart, which takes more area. Even at 175% that's only 9.3X. The energy hitting a covered field would be the same as the fixed (or adjustable) tilt case, so it's really closer to the 5X. If thin film is 11% efficient, that's only 3.36x area improvement.

In outer space, a 3X improvement in area (and weight) is a big deal. I don't think area is as significant as cost/kWh for most land use. If thin film collectors can be made really cheaply, then it's cost-effective for roofing, siding, fencing, awnings, etc. We consider farmed biomass practical for transportation energy, but "inefficient" thin-film PV requires ~200X less area than crops.

As for water heating, the efficiency goes down with increasing temperature. It would be suitable for pool heating, or warming water, but not hot water. The cost of piping can be pretty high, though.

Though I wish this company success and am happy to see lots of startup companies coming up with new ideas, I can't see how the improvements made would yield the cost reductions claimed. The calculations of +175% (or even 1.75X), 16x area reduction, and 90-100% of rated power from 7am-6pm don't make sense.

Birender Govil

Its unique in the world. I am thankful to Sungri,s product. I can sell this item/product in India in large quantity.
Manufacturer can also write comments to my bgovil@hotmail.com Birender Govil


Similar products by http://www.greenandgoldenergy.com.au and http://www.solfocus.com/product.php?pid=4 are much closer to mass production; more than calculations.

Daniel Bender

How can I invest in SUNRGI?

How can I be the first one to get these panels for my planned home installation?


Comments here are all blah blah blah...

Wait a minute folks: 5 CENTS/KWH.

BING! BING! BING! the bell we've been waiting to hear for FORTY FIVE YEARS just rang.

Oh yeah, well, back to blah, blah, blah, blah...


Comments here are all blah blah blah...

Wait a minute folks: 5 CENTS/KWH.



Bob Wallace

This site needs a moderator system.

Otherwise it's going to deteriorate into a worthless exchange of nasty posts and spam.


Another claim of 5 cent solar:


Researchers claim photovoltaic cell advance

Amir Ben-Artzi
EE Times Europe
(04/30/2008 7:59 AM EDT)


The Israeli team is set to challenge others who are using photosynthesis for photovoltaic cells, including universities such as Cambridge in the U.K., and Stanford, M.I.T, the U.S. Naval Research Laboratory, and the Universities of Tennessee and Arizona in the U.S, and several others.

The researchers suggest existing silicon based photovoltaic cells offer low average energy conversion efficiency of 12-14 percent, while their system is capable of efficiencies of about 25 percent. They based their photovoltaic device on genetically engineered dry proteins photosystem I (PS I), encapsulated in solid state substrate bottom metal and a top transparent electrode.

Stephen Boulet


Well, not exactly. That one point gets really hot, but you need to get the heat out really fast, hence the large heat sinks.

Annie Carmichael, San Francisco, CA

CSP is set to bring an impressive amount of solar to the grid. But if those projects all of the sudden become 30% more expensive to install, will they go forward? If Congress fails to renew the expiring solar investment tax credit we will likely see large-scale solar projects around the country come to a grinding halt.

I work at Vote Solar, and I urge all of you readers who want to see continued growth in solar to join us in asking Congress to extend the expiring clean energy tax credits. Failure to promptly extend renewable energy tax incentives places 116,000 jobs at risk in the wind and solar industries alone, and potentially stops $19 billion in clean energy investment in our country. Go to this link to get involved: http://salsa.democracyinaction.org/o/1179/t/4214/campaign.jsp?campaign_KEY=24443


Concentrating solar photovoltaic is a good idea but it certainly isn't an original one. Sungri's efficiency claims are clearly just rough back of the envelope calculation at best and stock scam at worst.

Judging by the announcement the only thing special about their collector is cooling for the photovoltaic cell. If I had to guess what they're clever idea was, I would say that they are using heat pipes to cool each cell.

I suspect that you would be better off helping the widow of a Nigerian finance Minister then investing in this suspicious company.

Bob Wallace

People were trying concentrated solar with PV panels back in the 1980s. There was a fairly large test in Southern CA. Fresnel lenses cooked the panels.

(My first residential system used some of the panels that were only slightly cooked. They had turned from blue to brown and put out ~90% of rated levels.)

Sungri says that they have solved the overheating problem with a compound that they are calling "goop", at least for now. This substance seems to be very effective at wicking heat away from the hot spot. It's also being studied as a way to cool computer chips.


The above quoted announcement out of Tel Aviv could be very major for the future of energy.

These people seem to have "grown" proteins that they predict will be 25% efficient (twice current PV panels) and can be made for next to nothing.

They're talking 100x to 200x less expensive than silicon PV. That would make them 10x to 20x less expensive as thin film (using Nano Solar's price estimate).

Let's see how this one tests once it gets outside the lab....


CPV is about several things. Mainly it is about exploiting some form of PV which is either very expensive per unit area (all PV a decade ago high efficiency PV today), or which doesn't work well with low intensity light (again todays multi-junction PV).
Technical problems include:
(1) tracking.
(2) Optics, cheap but of sufficient quality.
(3) Cooling.
SunGri seems to be pushing on (2) and (3), i.e. they are using high concentration factor, and need to pay special attention to cooling. Soliant, and CoolEarthSolar are trying to use cheap but relatively poor optics to achieve much lower levels of concentration. I suspect that the price of the PV component will come down, and that should favor the cheap poor optics approach.

Another design discriminant is unit size, SolFocus uses tiny concentrators to illuminate 1mm square cells, thereby simplifying the cooling task. Larger unit size, means more challenging cooling, but avoids the need to support large numbers of cells.


Some additional information on what Sungri is doing here:


A fine example of how solar will soon take over. This efficiency has been demostrated and tested by NREL at only 10 suns.

Collecting heat and electricity from the same solar system is called solar cogeneration. It has already been done by the Colorado team in the solar challenge in DC.

Non-tracking CSP will probably be the wave of the future though.


This is an example of the worst of the solar energy business. Sunrgi is making incredible claims made for efficiency (37%) and production costs (5-7 cent/kWh) without any evidence supporting the claims. The Sunrgi website has no pictures of prototypes, no graphs of experimental results, and no meaningful reports.

The efficiency claim in particular ridiculous. The 37% efficiency is what the maker of the photovoltaic cells, Spectrolab, is reporting. Sunrig would have us believe that their optical concentration system and their power electronics are 100% efficient.

The cost estimate is also unbelievable. Assuming an average of 7.5 kWh/m^2 per day of sunlight for a two axis tracking collector, 37% conversion efficiency, and 0.07 dollars/kWh, a 1 m² panel would generate $71 of power per year. Assuming a payback period of 10 year, the production cost of the panel would need to be $710 per square meter. This would have to pay for the concentrating lenses, the photovoltaic cells, the heatsink, the support structure, the tracking system, the power electronics, the land and maintenance.

Solar energy industry does not need another company claiming the impossible!


I am new to your site and really enjoyed reading your posts. Keep it up!


Easy there Mike.
SpectroLab PV cells are currently 40.7% using "metamorphic semiconductor materials". This is the first use of msm materials. Theoretical limit is supposed to be 58% and they expect to acheive 45% then 50% cells in future.
At least two other CPV companies are claiming 35% or more using the current SpectroLab cells:
1. Delta Electronics – 35% eff. CPV panels using 40.7% eff. Cells from Spectrolab
2. SolarTec’s "Sol*Con™-concentrator technology which provides efficiency rates over 35 percent"
I'm not sure about 5-7 cents. Could be hype but 37% efficiency is not an outrageous claim for CPV.

PS University of Delaware has achieved 42.8% efficiency. Don't know if their PV technology can be used with CPV. http://www.greencarcongress.com/2007/07/ud-led-team-set.html UD led team – record 42.8% efficiency – July 2007.

Note: 40.7% cell acheivement is over a year old and 42.8% cell acheivement is almost a year old.


If the concentrated heat is a simple byproduct occuring after electrical production of the cell, then it could be used thermally to heat water. As stated above, you would normally keep your collector temp as low as possible for highest efficency, but as this heat is just thermal waste, the high delta t could serve to greatly reduce the size and cost of a domestic heat exchanger. Thermal silicone fluid on one side and domestic water on the other in a simple brazed plate or quad rod could be just the ticket.
Of course, if there was enough heat of a high enough temp, a bottoming cycle utilizing a sterling engine could add another 18% output and could still leave enough heat in the waste stream the heat hot water - but now your back to cost.

Bob Wallace

I keep going back to the size of the 'front lens'. That's going to determine the amount of sun-heat that is collected.

If you want to heat water, run a Stirling, do a direct heat-electricity conversion then it makes sense to increase your collection area.

Use a lot of cheap heliostats and bombard your device with heat, don't limit it to one small frame of sunlight.

Kit P

For the more serious scholars of PV solar an interesting LCA of my favorite system, Tucson Electric Power’s (TEP) Springerville, AZ field PV plant:

Energy Pay-Back and Life Cycle CO2 Emissions of the BOS in an Optimized 3.5 MW PV Installation


Gee Jim.... only one post every 2 to 3 weeks is pretty slow. Are you okay? I am worried you are in ill health.




Sungri's website has a PowerPoint document that states that the PV cells used in its collectors are manufactured by Spectrolab and they are 37.5% efficient. Spectrolab sells terrestrial PV cells (part number C1MJ) with an average efficiency of 37.5% at 25 C. It's pretty clear that Sungri's collector design assumes the 37.5% cell and not a more advanced 40.7% cell. It's still looks to me like Sungri is playing fast and loose with the numbers.

Stephen Boulet

It might be that Sungri is running their Spectrolab collectors at a higher intensity than used in the 37.5% configuration.


Carl Hage

Yes, the Sungri is 3X the intensity of the Spectrolab concentrators-- 1688X vs 500X, and the reported efficiency was a lab measurement. They didn't say if it was the first minute after being at room temperature (maybe) but the test wasn't with the final bare-chip to heat-sink configuration.

Whether it's 40% or 30% isn't as significant as bringing down the cost of the lens and tracker. Seems hard to compete with the cost/W of thin film.

Also the 16X claimed area reduction is completely bogus, so leads me to be skeptical about other computed claims like cost/kWh.

Bob Wallace

Don't want to cheer lead for these folks. I have no idea whether they are for real or not. But on their FAQ page you can find this....

"Q5: Is there a functioning prototype of the product and has the product been tested?

A: Yes. XCPV prototypes have been built and successfully tested under both laboratory and field (outdoor) conditions."

And they continue to make the $0.05 per kWhr noise. I don't see significant waffle words surrounding that claim.

Bob Wallace

There 16x less land is based on 7% efficient non-tracking thin film against their 37.5% efficient tracking collector.

Their test site is apparently down at around 35 North where a tracker is going to add solar hours more than it would at a higher latitude.

Does that work out to 16X? Don't know.

But if this graph is correctly constructed, maybe....


It is a privately held company so that would give them some latitude in terms of truthiness. No shareholders to sue them for false promises.

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