PV Gap

Sarah Said:

How do I determine the size a solar hot water tank?

We Answered:

Ed is wrong. Solar thermal is 95% efficient compared to pv's 15%. Not to mention the $30,000 install difference. Its easy to size a system. acting like its hit or miss is absurd.

The way you size a solar thermal system is to determine how many people live in the house. Will you be installing a solar heat exchanger at your air handler for hot air? is it just for domestic hot water? usually a 4 person home with just domestic hot water is 80 gallon tank with 2 panels. I know, my job is to size thermal and pv jobs.

Beverly Said:

could a hot-water Solar Panel be damaged by large hailstones?

We Answered:

Yes, but one way to avoid breaking the glass would be to attach a motor that would tilt the panel to a 90 degree angle. you would have to use flexible piping but the foresight if you are in an area where hail is common, the extra cost of replacing the glass panel would be negated.

Nicole Said:

do the back of solar panels get hot if so how hot do they get?

We Answered:

It actually improves the efficiency of the photovoltaic cells as it limits the temperature to under the boiling point of water. Photovoltaic cells become less efficient at higher temperatures.

Problem is that the photovoltaic cells actually like it much cooler than the boiling point of water so you wind up pumping so much water volume that all you get is warm water.

Ross Said:

What is the temperature of the water after 2 hours?

We Answered:

Let UNITs guide you; always USE THEM in your calculation to prevent errors

Firstly, the eqn: warm water + heat = hot water

heat absorbed over 2 hours = (725 J/min * 2h * 60min/h) = ??

heat absorbed = (4.18 E3J/kgC * 8.0E1 kg) * (T-30)C

Plug and SOLVE for T

Basic mathematics is a prerequisite to chemistry – I just try to help you with the methodology of solving the problem.