How much Energy (BTU) you need to build one Solar Cell, and How much (BTU) can that Cell generate ?
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Answer:
Trying to figure the BTU produced by a solar cell is tough since a photovoltaic solar cell produces direct current or DC measured in Watts.
Additionally, solar power can be used for more than just generating an electric current, further frustrating the problem.
Passive solar can be super simple and really cheap, yet provide hot water for your home on a daily basis, even when it is cloudy. The rays that heat water in a passive solar system are the rays that still get through light cloud cover. Passive solar systems can be a DIY project or can be a commercial installation. My parents live in the mountains and have used passive solar ( a 10 X 6 panel) to heat all of their water for the last 10 years.
Photovoltaic Solar Cell are not the total answer for Energy generation, but are part of the total solution. A combination of Solar cell fields, Wind turbine generators and Hydroelectric power supplemented by Natural Gas provides a sustainable energy supply that is mostly non-polluting.
One last comment - the in-effiency of Solar Cells is used as a reason not to go solar. You will hear that Solar Cells only convert 15 - 20 % of the sun's rays that hit the cell and so it is inefficient. Solar cell reasearch is trying to up the conversion rate, but the real response to this complaint is:
(the rebates mentioned below are in the US and only in a couple of states)
BEFORE the solar cell was in place, you got 0% conversion and paid 100% of your fossil fuel energy bill.
AFTER the solar cell was in place, you got a rebate on the installation, you'll get a yearly tax credit, the resale value of your home increased AND you are paying 0% - 15% of your former fossil fuel energy bill and MAYBE you are getting a check from the fossil fuel provider.
That 15% - 20% starts sounding pretty good.
Especially when not paying for increased costs for fuel over the next 20 years.
I have no idea how much energy it takes to build a PV cell. I do know that the cell can generate unlimited energy over time, barring being broken. It doesn't get "burned up" and it doesn't produce green house gasses.
Been listening to the Hummer manufacturers a bit too much?
Natural gas faces the same problems as any other hydrocarbon fuel. However, we now waste a lot of the energy by flaring it off at well-heads worldwide, and not allowing it to be liquified and shipped where energy is needed. Politics, and many environmentalists have been at the forefront to perpetuate this waste.
The solar cell generates electricity proportional to the light on it, with a life of 10-20 years or more. No limits to the total BTUs generated over its life except by its size and efficiency and the amount of light you can get on it.
At present efficiencies at the earth's surface, it takes a very large area to get a lot of power. A friend has an array about 10' by 10', and it generates enough energy to power his telephone and radio and a couple low-wattage bulbs OR a small fan for cooling for a night, from a good shiny day. If it is cloudy, he has to economize. he does have a shed full of batteries to charge up for peak power needs, like vacuuming the house!!.
Solar power is very expensive still at the consumer level, and the manufacture involves many very toxic chemicals. But so far, no reports of major poisonings from them. If a terrorist released the chemicals, though, many people could die.
IF you have the money to shingle your roof with solar cells, and pay for the batteries and the AC/DC converters, you cn cut the OPERATING costs, and perhaps if you economize (No air conditioning, no area lights at night, etc...you could break even in quite a few years. Solar cell technology is improving, but not really there yet for commonplace applications.
I suggest you look up the conversion from BTUs to watts!! And realize, that the conversion from electricity (watts) to heat (BTU) is not totally efficient.
My friend still burns gasoline in his truck to get to town, and LP gas for winter heating. Solar cells that are affordable cannot supply anywhere near enough energy for a vehicle to go up and down the mountain and into town. or for winter heating.
Maybe years from now!! He would have to cut his forest down now to have enough room for solar cells and batteries to get away from gas heat, and have an electric car that would make it to town and back. Not to mention many 10's of thousands of dollar into cells and wiring and batteries and AC/DC converters and solar cars, etc. Not on Social Security pittance.
You are essentially asking about "EROEI" (Energy Returned on Energy Invested), which is how much net energy can you get from photovoltaics. If it takes less energy to manufacture and deliver a PV cell than that cell will produce over its lifetime, then PV is a promising energy source.
The good news is that photovoltaics have a relatively high EROEI, with paybacks in the one to four year range (search for EROEI and photovoltaics to find more info.) Wind Power also has a high EROEI.
Interestingly, nuclear power has a low EROEI. It takes so much energy to build, maintain, and decommission a nuclear power plant and to mine the uranium that the plants don't generate much net energy.
Natural Gas, unfortunately, is a non-renewable resource that will be going into decline along with oil. It won't be a solution for our energy needs.
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