Why not install photovoltaic solar panels and get the energy monkey off your back?

Question

In CA. a 40% purchase rebate offsets the initial cost. Also, you can finance into your mortage and defer the rest into no power bill for 25 years (the warrented life of the panels), and write off the loan interest. Anyone?

Answer 1

i am installing PV panels, plus i am making some of my own design. the biggest rub is the cost of the PV cells. they are coming down a bit but not fast enough for mainstream users.

Answer 2

A "typical home" in America can use either electricity or gas to provide heat -- heat for the house, the hot water, the clothes dryer and the stove/oven. If you were to power a house with solar electricity, you would certainly use gas appliances because solar electricity is so expensive. This means that what you would be powering with solar electricity are things like the refrigerator, the lights, the computer, the TV, stereo equipment, motors in things like furnace fans and the washer, etc. Let's say that all of those things average out to 600 watts on average. Over the course of 24 hours, you need 600 watts * 24 hours = 14,400 watt-hours per day.

From our calculations and assumptions above, we know that a solar panel can generate 70 milliwatts per square inch * 5 hours = 350 milliwatt hours per day. Therefore you need about 41,000 square inches of solar panel for the house. That's a solar panel that measures about 285 square feet (about 26 square meters). That would cost around $16,000 right now. Then, because the sun only shines part of the time, you would need to purchase a battery bank, an inverter, etc., and that often doubles the cost of the installation.

If you want to have a small room air conditioner in your bedroom, double everything.

Because solar electricity is so expensive, you would normally go to great lengths to reduce your electricity consumption. Instead of a desktop computer and a monitor you would use a laptop computer. You would use fluorescent lights instead of incandescent. You would use a small B&W TV instead of a large color set. You would get a small, extremely efficient refrigerator. By doing these things you might be able to reduce your average power consumption to 100 watts. This would cut the size of your solar panel and its cost by a factor of 6, and this might bring it into the realm of possibility.

The thing to remember, however, is that 100 watts per hour purchased from the power grid would only cost about 24 cents a day right now, or $91 a year. That's why you don't see many solar houses unless they are in very remote locations. When it only costs about $100 a year to purchase power from the grid, it is hard to justify spending thousands of dollars on a solar system.

Answer 3

Photovoltaics will never be the complete answer to our energy problems, cue to the inherent inefficiencies of the process which converts light to electricity. IIRC, the theoretical limit for the efficiency of photovoltaics is only about 40%.

Photovoltaics might work adequately for a single family dwelling (especially if you eliminate the use of power-sucking appliances such as hair dryers, clothes dryers, etc., and convert everything else to DC power).

But to supply enough power for all the earth's needs, you'd have to cover the entire planet with photovoltaic panels. And on a cloudy/rainy day, you'd be really screwed -- batteries can only hold just so much energy, and if you're using it to run your house, you can't use it to recharge batteries.

And that doesn't even begin to account for the fact that, by covering the entire planet to make electricity, we'd block out the sunlight for all our croplands, so we'd all starve to death.

Answer 4

Solar power is very expensive. On a $250, 000 house you could expect to pay around $100, 000 to have sufficient solar power for basic use. That is a hell of a cost and makes solar power far, far more expensive than mains electricity.

And that will only ever serve basic needs. That would not enable the use of air conditioners or other devices that have large power drains. So all houses will still need to be connected to the power grid.

Then you need to factor in the battery shed. Solar only generates power for during sunny days. No power at night, no power when it rains. To overcome that a house need to have a huge battery supply to maintain power. That requires a minimum of a shed 1.5m x 3m x 3m. Obviously that is impossible in apartments but even in suburban houses it represents a lot of lost space and it is ugly. As a result solar power devalues a house. So in addition to the $100, 000 it costs to fit a house with solar you need to factor in an extra $20, 000 in lost property values. You are now looking at solar power costing half as much as the house itself.

The third big strike against solar power is maintenance. Solar panels need to be kept clean to function. That means that in most cities and many rural areas you need to climb on the roof and clean them at least once a month. That makes them impractical for the elderly, the ill, rental houses and so forth.

As for the environmental benefits, they are dubious.

Solar panels need a LOT of energy to manufacture. It's hard to calculate exactly but at the moment solar panels probably only save around 20% more fossil fuel than coal electricity. That isn't a huge advantage for something so expensive.

Added to that solar panels are produced by mining mineral sands. Sand mining is one of the more environmentally destructive mining processes because of the habitats it occurs in.

The third environmental strike is that solar panels contain toxic materials. They pose a real disposal problem because they can't simply be thrown out at a landfill, they need to be processed to remove the toxic chemicals and metals they contain.

And that is why few people use solar. It has no economic benefit and any environmental benefits are dubious at best. Solar technology will doubtless continue to improve over time and with increasing use, but right now they are a poor second choice to mains power.

Answer 5

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