[amsat-bb] Waiting for Solar Panel Efficiency (Ha!)
wouterweg at gmail.com
Fri Jan 1 13:37:44 UTC 2016
Its indeed Yield, but also the fact that there is far less GaAs fabs around
the world, and even less with their process controls good enough to make
the required (almost defect free) wafers for triple junction GaAs cells of
a substantial size. This is also why you see smaller cells being used in
space (smaller wafer size) instead of the big size wafers in Si technology.
Also, who cares about process variation in Si as long as the total panel
assembly meets the spec.
In space, that 1% extra efficiency can make the difference on your power
budget. Hopefully including your margins ;)
Most terrestrial cells have lots of defects in them that are not a problem.
On a sidenote: even the premium space cells are not completely defect free,
but for high profile missions, usually hand selected batches are combined
into panels and the "scrap" cells can be re-used on other missions or
resold as grade B. This process can be done by either the cell manufacturer
or the panel assembler, depending on the mission.
Each cell is certified by the manufacturer for performances including
Interestingly, on the Triple junction GaAs cells I have been working with,
a defect will lead to that spot in the panel acting as a LED ;)
On Wed, Dec 30, 2015 at 6:38 PM, Stephen Nelson <
steve.motorola.uranium at gmail.com> wrote:
> I think it has to do with the starting material and test specifications....
> Si is cheap, and can tolerate most VLSI manufacturing processes. GaAs is
> very brittle and has a "bad attitude" during manufacturing to put it
> My guess, the extra cost comes from Process Yield, and strict Final Test
> requirements to meet the reliability specs.
> Stephen N.
> On Wed, Dec 30, 2015 at 9:05 AM, Robert Bruninga <bruninga at usna.edu>
> > Compare the cost and efficiency of solar panels for cubesats and for your
> > house:
> > http://aprs.org/Energy/solar/efficiency-comparison-cost.png
> > The 10,000 Watt array for your house costs less than a 10 W array for a
> > cubesat satellite.
> > I get tired of the excuse, “Im waiting for higher efficiency cells” when
> > the cost of just doubling the efficiency from 15% to 30% is a factor of
> > 1000 times more expensive. You’ll be dead before the expensive ones even
> > come down by half (much less the 1000 to 1 needed to make them
> > And in fact it will never ever happen. Because a satellite builder will
> > pay a measly $10,000 to DOUBLE the power of his 4 inch satellite and so
> > market for the highest efficiency cells will always get a premium price
> > because the satellite buyers will always pay max dollars for max power
> > independent of cost.
> > And there will never be a decaying cost or learning curve, because as
> > as someone comes up with a 32% solar cell, then the 30% technology is
> > ABANDONED because the space industry will all move to the 32% cells and
> > happy to pay even more for the higher power and there is practically no
> > market for last year’s 30% cells that cost 1000 times more than existing
> > silicon cells at 15%. And without a growing market for last year’s HIGH
> > efficiency cells, there will never be a learning curve and declining
> > Meanwhile the cheap 15% cells being mass produced for the terrestrial
> > market in a MILLION times the volume at 1/1000 the cost already cost less
> > than a window of the same size! Witness the cost reduction of 10 to 1 in
> > the last 10 years and the 2 to 1 reduction in the last 3 years with
> > improvements from 15% efficiency up to around 18% not by changing the
> > technology of the 60 year old simple silicon, but just optimizing the
> > manufacturing process (by the billions)…
> > Solar is here, Now. And it won’t get any cheaper, because as the market
> > expands exponentially the demand for bazillions of watts of solar will
> > up every panel produced and homeowners are then competing with massive
> > utility scale purchases of millions of panels. Solar panels now cost
> > than just a window of the same size. It is no longer the cost of the
> > panels, it is simply the cost of labor that drives the majority of cost
> > now. You can buy solar panels for under $0.70 a watt but to have a
> > contractor installed system is hovering around $3.50 per watt and not
> > down much at all.
> > Lastly, if you have sun, you KNOW eventually you will be going solar. So
> > once you realize that, you should also realize that every electric bill
> > pay from now on is just throwing money away which would have been better
> > invested in free electricity and 10% annual return for life on your roof
> > in your yard.
> > Waiting gains nothing. Even the solar panels I bought 4 years ago at
> > the price have already paid for themselves. Waiting would have gained
> > nothing except 4 years of more wasted money to the utility and so many
> > of burned coal wasted into the air. Here are some more thoughts…
> > http://aprs.org/solar-now.html
> > Summary, Solar and Satellites… the same but 1000 times cheaper on Earth.
> > Bob, Wb4APR
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> Stephen Nelson
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