Solar Energy

How do we capture or harness solar energy?

• Solar energy is most abundant form of renewable energy

• Annual sunshine hours in New Zealand range from about 1600 in Invercargill to over 2400 in Blenheim and the main centres receive about 2000 hours

Solar heaters

• Solar water-heaters trap the energy in a collector panel (either a flat sheet or envelope of darkened metal or an evacuated (vacuum) tube which all absorb the heat.

• Heat is transferred to water flowing through the panel/tubes attached to the panel.

• Heated water then flows into a storage cylinder.

Sunlight to electricity

• To convert solar energy to electricity/ photovoltaic (PV) cells are used - known as solar cells

• Usually made of silicon

• They are designed to generate an electric current when exposed to sunlight

• New Zealand could produce about 4 kilowatt-hours a day per square metre, using PV cells.

• PV electricity is well established at certain remote sites.

• New Zealand's coastline has several solar-powered lighthouse

• We also kilometres of electric fences on farmland and nature reserves fed by PV-powered solar panels

Using solar power around the house

• Used to heat water - lowers energy bills

• Good for the environment - we rely less on other renewable energy

• Used to produce electricity

How does the heat/light travel from the sun?

• The sun radiates heat and light in the form of electromagnetic radiation

• Electromagnetic radiation is a name given to various types of radiation

• As the energy radiates from the sun it spreads out

• Various types of e.m.r include light (visible spectrum) radio waves, microwaves, infrared, ultra violet/ x-rays and gamma rays

• E.m.r travels at the speed of light

What is a solar panel?

There are two types of solar panels:

Solar photovoltaic modules use solar cells to convert light from the sun into electricity.
Solar thermal collectors use the sun's energy to heat water or another fluid such as oil or antifreeze.

Solar panels, also known as photovoltaic cells (PV) are made of special materials called semiconductors – silicon.

· Silicon is similar to what sand is made of

· They are expensive to make

· There is more silicon on the planet than anything else.

Solar collectors

· Is usually mounted on the roof

· It faces the sun

· As the sunlight passes through the collector's plastic or glass "glazing," it strikes a metal or rubber absorbing material.

· The material converts the sunlight into long wave heat, and the glazing prevents the heat from escaping like a greenhouse.

· It is like leaving a car parked in the sun with its windows rolled up.

· The collector box has a transparent plastic or glass "window" covering a flat black plate. The black plate is attached to a series of parallel tubes or one long tube through which water, or other heat transfer fluids pass.

· Heat energy is transferred from the collector to the water storage tank.

· In some water heaters, hot fluid is pumped from the collector to the storage tank.

· The pump is powered by electricity that either comes from an electrical wall outlet or a small photovoltaic module located beside the collector.

How does a solar panel work?

· When light strikes the cell, it makes the electrons move around within the semiconductor material. · This means that the energy of the absorbed light is transferred to the semiconductor.

· PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction.

· This flow of electrons is a current, and by placing metal wires on the top and bottom of the PV cell, we can draw that current off to use or we can collect the electricity in a rechargeable battery.

· We can use the electricity later on.

Can we use solar panels at night?

· When the sun stops shining the electrons stop moving and electricity stops flowing

· A battery is then used

· If the solar panel has a battery connected electricity from a solar panel flows into attached batteries while the sun shines

· The stored electricity in the batteries can be used at night, or when the sun is behind the clouds.

What impact do solar panels have on our environment?

a) Disadvantages of solar panels:

When solar panels are produced they have leftover dangerous materials
When solar panels are made, energy they use pollutes the air
Can't use solar energy during the night or on cloudy/foggy days
Large areas of land are needed to produce large quantities of electricity

b) Advantages of solar panels:

Solar panels don't pollute the air
Solar panels don't release carbon dioxide, nitrogen oxide, sulphur dioxide, or mercury into the atmosphere
Solar panels operate silently, have no moving parts, and don't release offensive smells
Do not contribute to acid rain

Activities

Solar Oven

Websites

http://www.energyarchive.ca.gov/energyquest/story/chapter15.html

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