Solar Panels and Payback Time

Task 1

Remind the person next to you:

• Which is better - a high U-value or a low U-value?

• The scientific definition of a U-value.

• How much energy would be lost each second through a window of measuring 1m by 2m, with a U-value of 2.9, if the temperature difference between the inside and the outside was 10˚C.

Task 2

Solar panels capture energy from the sun which can be used to raise the temperature of water flowing through them.

This means less energy is required to heat the water to the desired temperature for use in the home.

The pictures above show solar panels on a rooftop in the UK and on a rooftop in Israel.  Stick the images in your exercise book and explain:

1.) How are the solar panels designed to be effective at capturing energy and heating water?

2.) Why do the solar panels in the second picture not require a pump to circulate the water between the panel and the storage tank?

3.) What would be the best direction for a solar panel to face in the UK, in order to receive the maximum possible amount of solar energy each day?

Task 3

Like fitting insulation, solar panels cost money to purchase but will save money by reducing your energy usage.  To find out how cost effective they are, we must consider the payback time.  The payback time for fitting insulation, or another home improvement is defined as the time taken for the savings to equal the initial cost of purchase.

Look at this powerpoint presentation explains how to calculate payback times, and shows you some example calculations.  When you are happy you understand, write the formula below in your exercise book.

Now try these payback calculations.  Show full working in each case, and remember to give units with all numerical answers.

Task 4

You have seen how solar energy can be harnessed to heat water in our homes, and you have probably seen photovoltaic panels used to convert sunlight into electrical energy before.  Watch this video clip, which explains how the PS10 "Solar Power Tower" in Seville is doing both.

Discuss with the person next to you the advantages of this method of generating electricity over using conventional photovoltaic panels?