PV Gap

Emily Said:

Would you please comment on this article I saw today on the internet. Especially with all the talk of 2012.?

We Answered:

Certain scientific communities have known about this for years. I wish more people were aware of this. It doesn't take much energy to disable solid state equipment (integrated circuits), and with dependence on phones, gps, cars (they have electronic brains that can be disabled too), and etc., technically advanced societies could be crippled during a severe solar storm. But don't worry, we'll probably be hit by an asteroid before a solar storm destroys the earth.

Andrew Said:

Solar powered car idea worthwhile?

We Answered:

Most of the answers supplied are pretty far off from accurate. The short answer here is solar power costs more than power from the power company at present. So installed LOTS of panels to recharge the cars would not be finacially attractive. (Unless you got a govt grant to pay for the solar, and someone still paid too much for that use compared to grid power). A car roof does not have enough space to supply more than a few miles per day driving with a very efficient car and the whole roof covered in a place with reasonable sun per day. Solar power on a clear day at noon supplies about 100 watts per square foot, when pointed right at the sun. The solar power on my home's roof is ~15% efficient solar cells. Some are currently being made and being tested that they claim are ~50% efficient. At that rating, you could harvest about 50 watts per square foot. 1 horsepower is about 746 watts (a little more really due to losses). Hybrids have what, 30 horsepower or sol electriv motors. So you would need 60 square feet of solar power at noon (pointed right at the sun) to run that, about 8 by 8 feet and that is with cells at 50% efficiency that are not even being sold yet. Current costs are $3 to $5/watt minimum to buy (capacity wise). I hear the price will come down as much as 80% over time. How much time, who knows? I am all for plug-in hybrids, GM may put one out next year. Expect a lot of progress in solar, hybrids and batteries over the next few years. But if everyone waits until they get better, no one buys what is sold now. And if no-one buys what is sold now, no one is going to spend the (BIG) money to improve on what they are selling now. Makes the problem somewhat tough, you know?

Gene Said:

living off the grid question?

We Answered:

You might expect something close to 2 hours at your rated maximum panel output /day in winter.
http://www.solarcraft.net/sun-hours-map.…
Now every panel you buy is rated to have a maximum output, and you go from there.

You might get 3 hours a day on a year round basis.

You have to know how many kWh you would need to use during a winter day. and assume that for every kWh you need to use at night your solar panel will need to produce about 1.6 kWh to take care of your losses in storage.

You can likely cut your power usage a lot from what you use on grid if you go as far as using LED lights, putting the fridge in a cool basement, a small fridge, using only a small laptop, pumping your water by hand.

If just as an example you decide you can live with 20 kWh per day after allowing for storage, you will need something like 10 KW of maximum panel capacity.
That will provide more power in all other parts of the year.
Remember you need more lighting in winter, so allow for that.