I disagree with only one piece of Bob's analysis and that is the rise a complicating factor.

Just like on earth, every spacecraft developer is faced with the complication of permanent destruction of demand. The complication is most apparent in small spacecraft and/or in LEO.

In GEO, the energy demand is dominated by the need to produce higher power for transmitters so all the power you can generate is better if you decrease the size of solar panels unless you want INCREASE power demand by increasing capacity (add more channels with the same energy consumption per channel as before).

The issue with LEO space craft with smaller antenna and power limitations etc is that the computational requirements might stay the same BUT THE POWER CONSUMED to do the computations is steadily decreasing and is resulting in permanent destruction of demand and the pressure to increase efficiency is offset by decreased power requirements in electronics.

It should be clear that this is a complicated thing to model. I haven't done it and, like Bob says, I just don't care, I just buy what I need for spacecraft.

On house panels, people are not paying attention. All the solar panels you see hanging on telephone poles, charging batteries, to power street lights, etc I never ever looked once at the efficiency of the solar panels I purchased surplus from the bazillion produced for these telephone pole installation. I bought enough panels to produce the power I wanted to produce and with slowly getting enough panels to produce enough at winter solstice and the rest is surplus to my needs but my MPPT deals with that charging my batteries.

The other factor for houses is that permanent destruction of demand is happening there in case you want to set a maximize capacity for your panels and forget it. Permanent destruction of demand is happening in LED light bulbs, LED TV's, tinier power required by computers, more efficient cooling in refrigerators and other appliances. Many power companies and coal producers have become extremely concerned. In Virginia they set a fee on those wishing to tie their solar power to the grid. This is BS since they claim they must charge you to transport your surplus power. It's crap because almost NO ONE produces more power than they consume unless they live in Southern California for example.

The power and coal companies have lobbied for and received a fee to slow down the deployment of home and building owners from decreasing the demand on their grid system being fed by coal power plants.

I despise mostly stupid but sometimes corrupt politicians...

Thank you for your interesting discussion Bob,

Bob N4HY

On Wednesday, December 30, 2015, Robert Bruninga bruninga@usna.edu wrote:

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 practical).

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 the 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 soon 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 be 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 cost.

Meanwhile the cheap 15% cells being mass produced for the terrestrial solar 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 soak up every panel produced and homeowners are then competing with massive utility scale purchases of millions of panels. Solar panels now cost less 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 going 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 you 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 or in your yard.

Waiting gains nothing. Even the solar panels I bought 4 years ago at twice 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 tons 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 _______________________________________________ Sent via AMSAT-BB@amsat.org javascript:;. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb