The Solar Power Nitwits
by Robert Frenz, 2 June 2001
The waitress, Barbara, leaned over the table, displaying two of her nicer features, and said, "Look at my solar powered watch. Soon we'll have solar powered cars and we can travel without polluting the environment or depending on evil fossil fuel."
After raising my eyes, I replied, "As kids we'd watch the fireflies after dark while they moved hither and yon with their little glows glowing. My brother wondered how many of them we would need to make a lamp suitable for reading by." My brother and I had laughed together knowing, even at this early age, that illumination was an entirely different thing than mere seeing. We can see the stars at night but we sure as heck cannot read very well by starlight. The LCD (liquid crystal display) of the watch was visible but other than that, it was useless for any other thing.
Barbara let me know what time she'd be off shift and so I left to ponder the universe by asking myself such profound questions as, "Who am I? Who are you? Why was I born? Is the local Taco Bell going to shut down? Am I the real me? If I am not me, then I must be somebody else. Who is that someone else? Maybe he is someone else too." Heavy stuff, to be sure.
My thoughts drifted and I began to question some of the technical aspects of 'solar power', since I never believed that it would amount to more than flatus in a whirlwind.
The main thing most concern themselves with, when it comes to power, is their pimpmobile. The average person's automobile consumes about 500 gallons per year, considering 12,000 miles at 24 miles per gallon. One gallon of gasoline weighs 6.2 pounds and each pound is equivalent to 20,750 BTU (British Thermal Units). That means 128,650 BTU per gallon and when multiplied by 500 will give us about 64,000,000 BTU of energy needed per year to move us hither and thither.
The sun blasts our planet with 2 calories per minute per square centimeter. About 1/2 of this never gets through the atmosphere to titillate our wondrous modern-day solar cell/panels. Due to the earth's rotation, only about 8 hours per day is usable for solar useful power collection. Moreover, the limitations of solar cell construction, electron flow and all that jazz, dictate the efficiency which will probably never get beyond 50 percent for any practical purpose. During the day, the direct rays of the sun cannot ever meet the panel at 90 degrees all of the time. Thus, we need another finagle factor, let's say 60 percent following from the sine function. (Movable solar panels require energy to move them. I hope you didn't let that one slip by.) Ah, but we reside in a temperate zone where we don't get blasted as do those living in Brazil. That's another depreciation. And the full solar shot is absent during the winter, otherwise it wouldn't be winter. Oh my! All of these things shouldn't be, since they interfere with my dream of a Brave New Solar-powered World. (Actually, it already is and has been for a very long time.) When this is all multiplied together (252 calories per BTU), we arrive at an average figure of 150 BTU per square centimeter. This then, means that a solar panel area of 64,000,000/150 = 426,666 square centimeters will be needed for the family auto. It all boils down to a panel about the size of the floor in a large garage. "I can live with that," you say. Before we continue, one might ask who shovels the snow from this panel during the winter. Dirt, dust and pigeon droppings will also have to be daily cleaned off otherwise we won't be getting a full head of solar juice. Then there are all of those cloudy and rainy days to consider. Hey man! Our solar energy dream seems to be slipping all over the place. Let's continue, faithfully believing that God will never turn the sun off.
A solar cell generates electron flow. A whole wad of loose electrons is useless unless there is available some potential (volts) to drive them through your electric motor, which I assume will be powering the family play room on wheels. One can parallel connect a million flash light batteries capable of delivering thousands of watts, but you could still put your fingers across the terminals without getting fried. One and 1/2 volts just doesn't make it in the push department because flowing electrons must overcome resistance to their flow and one's body offers considerable resistance.
Years ago, I was part of a developing team involved in the construction of a prototype of a small 6-man amphibious vehicle for the U.S. Army. All knew that the best utilization of electricity depended upon a high voltage. As automobile engines grew in size, so did the need for more powerful starters. Car batteries went from 6 volts to 12 volts during the early period of my life. This also allowed for smaller diameter wiring. Cross country power lines are 75,000 volts and as Tesla proved, AC (alternating current) is superior to DC (direct current) for power transmission. Solar cells provide DC. Many forget that Edison used to publicly electrocute elephants to "prove" that Tesla's AC was dangerous. What many have discovered is that an electric motor, used to drive something weighing a ton (a very small family car), needs, as a practical minimum, 24 volts.
One characteristic of the solar cell is that when its voltage is doubled, its power only increases by 40 percent which means that they are the most efficient at low voltages. A good solar cell will produce about 4 watts per square foot. This is .23 BTU. Thus one gallon of burning gasoline is equivalent to a solar panel occupying 13 acres. That's quite a waste of a good corn field. A gingerly driven small pimpmobile steadily moving at 40 MPH would need 2 acres of solar panels just to keep it moving – no head wind, no hill and no acceleration.
If the voltage goes up, the available current (amperes) goes down, if we wish the power to remain constant. Our required solar panel now has to increase in size at least by a factor of 25. The net outcome is that we now require a panel at least as large as the lot upon which our house stands. (More than likely it will need to be greater.) If all the citizens in nearby Syracuse NY were so blessed with these miraculous fossil fuel alternatives, they'd need a 'solar power' lot the same size as their city! (Yes, they have nifty winters there and I can imagine the city planners adding another 100 snowplows to their stable just to keep the panels cleaned of those 6 foot deep drifts.) Think about what this means. Each square foot that you tar paper with your buildings, roads, and such is one square foot where plants cannot grow. Plants, other than being food, clean carbon dioxide out of the air and give back oxygen.
For our collected solar power to be available year round, we'll need capacitor or battery storage. An average auto battery ranks on the order of 1200 BTU. If we assume that we will need 1/2 of our requirements stored at any particular time, this amounts to about 50,000 auto batteries. I suppose you could have them buried and then build a house on top to conserve space.
If your car has a standard transmission, you could probably electric drive it, with the starter motor, about 1/2 of a mile, at less than a walking pace.
This battery thing is the reason battery powered cars are not zipping all over the countryside and never will, if we insist upon using anything larger than a one-man balsa wood vehicle. Battery operated cars were built in 1900. They flopped and they still will.
I have been somewhat loose with numbers and definitions but my purpose was not to write some technical paper. I only wished to announce a point before I left to visit the filling station.
Barnum told us something about suckers and where there is a sucker, there will be at least 6 snake oil salesmen at the ready to separate him from his money.