This is a repost of a diary I wrote late last year about some of the technologies the United States is developing in the solar space.
This has been reposted for those that missed it in order to complement the diary Ministry of Truth has just written. To SHOW you that Americans do have the capacity to create great change in the world for the better.
In December of last year I wrote of a technology called concentrated photovoltaics, which if all goes well, may bring the retail cost of solar panels down from at present, $4.31 per watt, to 30c per watt.
Moore's Law for Solar - 30c watt in years to come
The technology I discussed was the concentration of the sun, using fresnel lens or mirrors like in a telescope, being able to reduce the area of active semi conductor material down to 1000th of that of Silicon to produce equivalent electricity.
Today I'd like to look at Silicon solar cells and what happens if we concentrate sunlight onto them.
I mentioned in the first diary the amount of Silicon based solar panels produced in a year at 6.37 Gigawatts.
I also mentioned that in 2006-2007 China went from 622 GW of electricity generation assets to 713 GW of generation. And from 713GW to 793GW between 2007 and 2008. In other words 90GW and 80GW of generation.
Link
So if we know that we can concentrate the sunlight onto a solar cell and increase the amount of power coming out, what would that mean for our Silicon production for solar cells if all we did was change the lens?
Well, Silicon has a limitation in that as the temperature increases, so efficiency levels reduce. That is the amount of sunlight converted to usable electricity.
Silcon PV panel rating
Module performance is generally rated under Standard Test Conditions (STC) : irradiance of 1,000 W/m², solar spectrum of AM 1.5 and module temperature at 25°C.
Temperature influence on cell output
For most crystalline silicon solar cells the reduction is about 0.50%/°C, though the rate for the highest-efficiency crystalline silicon cells is around 0.35%/°C. By way of comparison, the rate for amorphous silicon solar cells is 0.20-0.30%/°C, depending on how the cell is made.
Lets consider that for a moment - For every degree of temperature above 25ºC (77ºF) a standard Silicon PV panel can lose anything up to 0.5% of its efficiency.
Maybe no big deal for temperatures don't get much above 77ºF for much of the year even in Las Vegas which hits a peak of 106ºF in July or 41ºC resulting at worst case a 16ºC over test conditions (STC) or 0.5% x 16 = 8% drop in output. However consider again this:
Sunpower - Silicon panels 20.4%
Suntech Breaks Solar Panel Efficiency Record - Again 16.53%
CIGS at 19.9%
Flexible CdTe Thin film at 12.4%
Although these are not all Silicon, you can see that an 8% loss during the hottest times of the year when power demand for air conditioning cooling would be at its peak, starts to seriously cut into generation and the usefulness and return on investment of these types of panels.
Having said that, there are a number of companies which have designed Silicon based concentration modules which reduce the amount of active material by changing how the sun focuses on the panels.
JX Crystals has a 3 x concentrator which uses mirrors to focus on silicon to produce the power.
Stellaris has a 2 x concentrator.
Solaria has a 3 x concentrator.
Solaria’s technology platform enables the solar industry to produce two to three times the number of PV modules from the same amount of silicon material used in today’s conventional modules.
There are a number of others listed here which do something similar.
CPV, Pt. 2: Low-Concentration Photovoltaics
What does this mean?
Well with different optics by concentrating the sunlight, the value of active silicon PV material in terms of rated power output being manufactured each year increases.
In the instance of 2 x concentration we go from 6.37 GW to 12.74 Gigawatts.
Using the 3 x multiplying effect of concentration we end up with around 19 Gigawatts of generation capacity worth of Silicon cells being manufactured each year.
Starts to look a lot better when you consider the 80GW being installed by China each year.
Solar hot water
In the majority of cases this is where solar energy is used to heat water or other transfer fluid in a panel located on someone's roof. These systems are normally closed loop augmented or backed up with another system which kicks in if the water temperature falls below a certain value.
The typical 50 gallon electric water heater uses 11.1 barrels of oil a year, which translates into the same amount oil used by a typical 4 door sedan driven by the average consumer.
As you can see from the above quote, installing a solar hot water system would it seems equate to removing a car off the road in terms of carbon footprint and less oil needed to be imported.
What if silicon PV was combined with a solar water collector system? Could it keep the temperature of the silicon cell low enough that it continued producing electricity and the efficiency levels were not badly affected?
20 x concentration unit
For those that have been following my diaries, you will know that I visited the United States in August and travelled across the country stopping in at a few tourist destinations but also some out of the way places where new solar technologies were being developed.
Back in the 1990's a firm called Entech Solar were working alongside Boeing and NASA to produce solar arrays which were sent into space. These were able to reduce the weight of satellite solar wings by reducing the amount of Silicon used through the use of thin film acrylic lens manufactured by 3M.
Stretched Lens Array
Back in the early 1990's, the first refractive concentrator array was flown on the PASP Plus (Photovoltaic Array Space Power Plus Diagnostics) space mission. The array was composed of ENTECH's "mini-dome" focusing lenses over Boeing's mechanically stacked multi-junction solar cells.
The lens was able to refract the sunlight hitting it, with a high error tolerance, so that a small strip down the centre of the heat sink was the only silicon required. This was a major cost and weight saving reducing silicon by 95% for the same power output.
Entech wrote a contract report on pricing of these units to bring this technology back to Earth for terrestrial applications. Even back in 1995 with the 95% reduction in expensive silicon they were able to engineer into their panels, the cost per watt for quantities over 30MW manufacturing would have been around $1.20.
This was the module Entech produced from the technology they had designed with NASA.
Two unit configuration.
Photos taken outside the Entech building of a 2 unit array and the tilting and tracking mechanism.
Entech built a 100kW air cooled array at 3M in 1990 using the 22 x concentration technology.
This comment from an articleat Treehugger on these modules sums up why this technology is extremely important.
For example, 50 kilowatts of solar cells used in conventional flat plate solar modules generates one megawatt of electrical energy using the Entech modules.
Entech photos of projects throughout the years
Link to full report
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Back in August I met with Dr Robert Walters, Entech VP of marketing, at their Fort Worth facility located in the Alliance Gateway estate in Texas. Dr Walters with 35 years in the industry, has a long association with solar technology development being the co-founder of Entech along with having served on the Advisory committee for the DOE and on the Texas Energy Co-ordination Council boards.
He was able to show me the curved stretched lens design Entech have designed and explained its significance is in the ability to refract sunlight to its targeted area with a very high level of error tolerance.
ENTECH’s Fresnel lens concentrators possess a shape error tolerance more than 200 times higher than other reflective concentrator approaches, making mass production, installation, and long-term operation in an outdoor environment far more practical than for other comparable systems.
Some of the other concentration systems, because they concentrate sunlight up to 1,500 times, often require error tolerance of less than 0.1º.
"All these technologies require minimum pointing errors (pointing accuracy better than 0.1º) under demanding operating conditions with which energy production is guaranteed and, therefore, the profitability of the installation," said Garrido.
Many developers, including Emcore who I also visited in August, are working and succeeding improving this error tolerance through advanced optics, but it seems with what Entech have developed in their 20 x concentrator and what Dr Walters showed me in their display, they are already there.
This organisation has also shifted, like many others, to a modular, stand alone system which reduces the prospective construction costs by eliminating much of the need for heavy machinery. Their initial product has made way for a new unit which, according to Dr Walters, is currently undergoing certification.
The most significant thing about this technology aside from the massive saving in amount of Silicon required, is the fact we have a combined solar hot water system and electricity generating PV unit combined in one.
These modules below were the prototype from when Entech worked with NASA developing this lens and low weight satellite array.
Entech's new module design minimizes weight and improves installation ease through a much more manageable sized unit.
The efficiency in terms of energy capture from the sun goes up by a factor of 4 or 5 using Entech's combined heat and power unit. In fact they suggest these units will act as a hedge against high gas prices by offsetting both electrical and heating requirements.
Although we only discussed this in passing, the potential for these modules to be used in solar Air conditioning is being pursued. This is where hot fluids heated by the sun, are able to be used in a system like the one below. Where hot fluid via an absorption chiller is able to cool another fluid circulating throughout a building and cooling the air down. Many organizations use similar designs.
Solar Airconditioning
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Tubular Skylight
One of the products which Dr Walters showed me Entech have developed was a skylight. I have done a lot of industrial installation work and have seen a lot of ducting installed in ceilings for HVAC, so could instantly see the advantages of this technology. Basically with a relatively small roof mounted enclosure, Entech have designed a skylight which simplifies the installation of a skylight, particularly in commercial and industrial buildings, by reflecting the sunlight. These I could see being installed by any HVAC installer as the skill set is identical.
The skylighting in this room is from Entech's technology.
This company is located in the Alliance Gateway insdustrial park, whose tenants include LG Electronics, Nestle, Texas Instruments, Mitsubishi, Lockheed Martin, Ford Motor Company, Motorola, AT&T, General Motors, Safeway, General Mills, M&M Aerospace, Bell Helicopter. Imagine the prospect for using these products when you see what the roofs of the estate's buildings look like.
Something went awry with my imagination when I got back to the airport that afternoon because of the prospects for these technologies I could now see in so many applications. So much so I think I freaked the guy out sitting next to me when I proceeded to take a photograph of the airport false ceiling. Where the skylight and the air conditioning ducting, along with providing the power for the artificial lighting, I knew could be serviced by the products I'd just seen at Entech's facility. In other words, the hour I spent at the offices of Entech change my whole outlook on how we achieve the things we have become acclimatized to doing a particular way.
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Conclusion
These technologies have incredibly disruptive potential in our pursuit of replacing conventional means of doing the same old things. The cost of the solar skylighting, if low enough, would be ideal for installing in place of artificial light saving significant amounts on electricity cost for a commercial establishment as shown in the shots above. Not to mention the heat saving factor if electric lighting is reduced, will lower artificial air conditioning costs as the HVAC system will not need to work as hard.
The combined heat and power solar panel is what impresses me the most even now. With this company having 25 years worth of performance data in the concentrating field, they have a proven and reliable product to sell utilities which are normally risk averse.
Couple this up with the low cost to entry to build a manufacturing facility for this technology as an Entech manufacturing facility capable of producing approximately 40 MW of panel costs around $5 Million.
But it most certainly is the 20 x concentration on silicon which has me most excited. With worldwide production of silicon at around 6 GW multiplying this by a factor of 20 makes it all seem possible.
When China is installing 80 to 90 GW of new electricity generation per year, 20 x 6 GW = 120 GW of potential electricity from this one technology alone.
The United States as of 2007, had approximately 1,087 Gigawatts of electricity generating capacity.
With 120 GW of solar PV being produced each year, installing solar seems a lot more practical and achievable.
Truly disruptive. At least to the way I think.
Maybe this is not such a far fetched possibility after all - running the world on todays sunlight, not yesterdays.
See despite all your current differences I believe that not only can Americans make the difference, take the lead and show the rest of the world how working for common purpose is able to make everyones life better... even now, as polarized as things seem, I still believe you will.