PV Gap

Juanita Said:

How much solar energy(in kilocalories) would be stored in a 500L tank whose temp was raised from 30 to 70 degC?

We Answered:

500 Liters weighs 500 kg. One kilocalorie is the energy to heat a kg of water by one degree and you are heating it 40°C so number of kcal = 500*40 = 20000.

Daisy Said:

Is solar energy practical for everyday use?

We Answered:

>So is it practical for everyday use<

It depends a lot on your location and the Federal, State, Local, and utility incentives applicable to your area. They are different all over so there is no way anyone can make a blanket statement on solar's practicality.

To illustrate what I mean, here is a price list for solar in my local area.
http://www.americanpv.com/pdf/res_on/pri…

A 6.45 kW system lists for $35,800.

For that size system, the feds give you a $10,740 tax credit.
The state I live in provides a $1,000 tax credit.

That still leaves over $24,000 to pay.

HOWEVER, my local utility pays $3 per watt or $18,150, thus leaving me to pay only $6410, which makes my payback period 4 years (or less), thus making an investment like this very affordable.

However, the key here is the local utility (APS) rebate. $3 per watt is considerably higher than other utilities. if that rebate were, for example, 1/2 of what it currently is, my price would go up from $6000 to more than $12,000, thus making the payback period long enough (over 10 years) that it would no longer be as practical to do.

So is it practical? For some people it is while for other people in other locations, it is not.

Gerald Said:

Can solar energy be stored and if so how long?

We Answered:

batteries are only bad for the envirinment if they are not recycled, and actually batteries are close to 100% recycled, they are a very good storage medium.

others include flywheels. a big heavy flywheel spinning at 80000 rpm will spin for years with almost no resistance, it's another good energy storage device that can store energy from almost any scource.

You can use solar energy to lift heavy weights high into the air, and as they fall use them to regenerate electricity, or spin a shaft.

You can use solar energy to seperate hydrogen from water by electralisis, and then use that as a fuel source in a fuel cell.

solar energy is not the only energy that can be stored in those ways, there is also wind, rivers, ocean waves and geothurmal (heat from the earth). all of which are clean and everpresent (the wind doesn't blow all the time, but it always blows at least 40% of the time).