Why is it renewable? Well, the sun will always be there for us, and we can use as much of the sun s energy as we want and it will never run out.

Transcription

1 6. Solar Energy So far we have been looking at how to reduce CO 2 emissions by cutting down on our use of fossil fuels. Now let s look at getting renewable energy from the sun. Why is it renewable? Well, the sun will always be there for us, and we can use as much of the sun s energy as we want and it will never run out. Did you know that the Earth gets enough energy from the sun in half an hour to provide us with all the energy we need throughout the whole world for a whole year? And that is without using any power stations that use CO 2 emitting fossil fuels! How do we capture the sun s energy? The most common way is by using solar panels. When we talk about solar panels we mean either Solar Photovoltaic panels for generating electricity or Solar Thermal panels for heating water. There are no C0 2 or any other greenhouse gas - emissions from solar energy (although there are emissions when the solar panels are manufactured, because it takes a lot of energy to produce them). Solar panels can look like roof windows. 6: Insulation 1

2 First, a quick lesson on atoms: everything is made up of atoms. They are so tiny that they would have to be many millions of times bigger before we could see them! The inside the atom is called the nucleus. Outside the atoms are electrons, which are light, negatively charged particles. An electrical circuit is formed when electrons flow in a certain direction. But they won t do that while they are still attached to their atom. Once the atom has lost its electron, it is positively charged. I ve lost my electron ELECTRON Are you sure? Yes, I m positive! ATOM 1 ATOM 2 Solar photovoltaic (PV) panels convert light, such as from the sun into electrical energy. This is how a PV panel works: The solar cells in the panel contain a special kind of crystal. When light energy such as from the sun - strikes the solar cell, electrons are knocked loose from the atoms. The electrons can be captured and made to move from one side of the cells to the other. This creates an electrical circuit and we can use this electricity! 6: Insulation 2

3 Solar thermal panels use the heat from the sun to heat water. 6: Insulation 3

4 Even on fairly cool days, the panels can extract some of the heat from the sun and heat the water. The water is stored in cylinders until it is needed, so we can have hot water even at night. In the UK, even in Scotland, a south-facing solar panel can provide around 70% of the hot water needed for a family home. Solar panels work best if they are faced to catch the most sunlight. So, in countries like Scotland that are north of the equator, the panels should face due south if possible. The UK receives only 55% - 60% of the solar energy that the equator receives, but that is still ample to operate south-facing solar thermal or solar PV panels. Solar panels PV and thermal can cost thousands of pounds to buy and install, but because they provide free heat and electricity, our gas or electricity bills will be less. This means they will eventually pay back the cost. What is pay back? Say a solar thermal panel costs 4,000 to buy, install and maintain (look after), but saves 400 per year on gas or electricity bills. After 10 years the panel has paid for itself in savings, and from then on all the hot water it produces is free! Solar Paint: Scientists are currently working on a new invention - solar paint! One day, in the not-too-distant future, we may be able to paint the roofs and walls of our buildings with a special paint that will produce electricity. New buildings could then be built with specially-designed panels for the south-facing walls, coated in solar paint. That might work out easier and cheaper than installing solar panels. Passive Solar: There is an easier way of making use of the sun s energy. During the day, when the sun is shining into a room, the room heats up. This is called passive solar. When the sun goes down, the heat can escape back through the windows, so close your curtains to help keep some of the heat in! Sometimes the room - or classroom can get too hot, so we have to pull down the blinds to stop the sun s rays shining in. Passive solar can be very useful in hot countries. For example, it can be used to heat up community ovens, by focussing the heat from the sun using mirrors. This means that people do not have to cut down trees for fuel. 6: Insulation 4

5 Do you know what a solar eclipse is? This happens when the moon passes between the Earth and the sun. Sometimes it completely blocks out the light from the sun. Almost immediately, the temperature drops dramatically, and it becomes very cold. After the eclipse is over, the Earth begins to warm up again. Source: NASA TV Getting planning permission Planning permission is something you need to get from the local council if you want to make changes to a house or building that you own. Nowadays it is usually not necessary to get planning permission from the local council before installing solar panels on the roof of a building. In most parts of the UK, including Scotland, you need planning permission only if the building is listed (especially important) or in a Conservation Area. Why not keep a lookout for solar panels on houses and other buildings when you are out and about? And if you know someone with a solar panel either PV or thermal ask about it! 6: Insulation 5

6 Concrete2Cookers quiz Solar Energy Level 1 1. We can produce electricity from: a. Just sunshine b. The sun and solar thermal panels c. The sun and solar PV panels 2. PV stands for: a. Positive Voltage b. Photovoltaic c. Paratonic Valve 3. Which statement is NOT true? a. If we use too much of the sun s energy, there won t be enough to go around b. The sun s energy can be used to heat water c. We can convert the sun s energy into electricity d. The sun s energy is essential for all life on Earth 4. In the UK, it is best if solar panels are facing: a. North b. South c. East d. West Level 2 1. You buy a solar panel to give you hot water. The total cost, including interest, works out at 3,000 and you find that it saves you on average 250 a year on your gas bill. What is the payback? a years b years c years 2. Which of the following conditions will give the best results for your solar thermal panel? a. A very cold but bright & sunny day b. A warm but foggy day c. Twilight 3. A solar panel will work in very cold countries like Finland and Greenland a. True b. False 4. Which of the following can a solar thermal panel NOT do? a. Heat a swimming pool b. Be used with an underfloor heating system c. Produce electricity Answers: Answers, level 1: 1.c 2.b 3.a; 4.b Level 2: 1.b; 2.a; 3.a; 4.c 6: Insulation 6