Energy Resources: Solar power

Solar Power is energy from the Sun

Introduction How it works More details Advantages Disadvantages Is it renewable?

Introduction

We've used the Sun for drying clothes and food for thousands of years, but only recently have we been able to use it for generating power.

The Sun is 150 million kilometres away, and amazingly powerful.

Just the tiny fraction of the Sun's energy that hits the Earth (around a hundredth of a millionth of a percent) is enough to meet all our power needs many times over.

In fact, every minute, enough energy arrives at the Earth to meet our demands for a whole year - if only we could harness it properly.

Image taken by SOHO Jan 19 2005, supplied by ESA

How it works

There are three main ways that we use the Sun's energy:-

Solar Cells (really called "photovoltaic" or "photoelectric" cells) that convert light directly into electricity.

In a sunny climate, you can get enough power to run a 100W light bulb from just one square metre of solar panel.

Solar cells make electricity from sunlight

solar powered calculator

This was originally developed in order to provide electricity for satellites, but these days many of us own calculators powered by solar cells.

Solar water heating, where heat from the Sun is used to heat water in glass panels on your roof.

This means you don't need to use so much gas or electricity to heat your water at home.

Water is pumped through pipes in the panel.
The pipes are painted black, so they get hot when the Sun shines on them.

This helps out your central heating system, and cuts your fuel bills. However, in the UK you must remember to drain the water out to stop the panels freezing in the winter.

Solar heating is worthwhile in places like California and Australia, where you get lots of sunshine.

Mind you, as technology improves it'll become worthwhile in the UK - see www.zeneagasolar.co.uk who claim their system can handle all your domestic water heating in the summer.
Their site has a good animation of their 'drain-back' system which avoids problems with freezing in cold conditions.

Solar Furnaces use a huge array of mirrors to concentrate the Sun's energy into a small space and produce very high temperatures.

There's one at Odellio, in France, used for scientific experiments.
It can achieve temperatures up to 33,000 degrees Celsius.

More details

Solar cells provide the energy to run satellites that oribt the Earth. These give us satellite TV, telephones, navigation, weather forecasting, the internet and all manner of other facilities

In California, the Solar One power station uses the Sun's heat to make steam, and drive a generator to make electricity. The station looks a little like the Odellio solar furnace , except that the mirrors are arranged in -circles around the "power tower".

'Solar One' power station, California. Click to enlarge

As the Sun moves across the sky, the mirrors turn to keep the rays focussed on the tower, where oil is heated to 3,000 degress Celsius, The heat from the oil is used to generate steam, which then drives a turbine, which in turn drives a generator capable of providing 10kW of electrical power.

Solar One was very expensive to build, but as fossil fuels run out and become more expensive, solar power stations may become a better option.

Energex (Australian power company): Animation of how a solar cell works at
www.energex.com.au/switched_on/activities/photovolatic/photovoltaic.html

One idea that is being considered is to build solar towers.

The idea is very simple - you build a big greenhouse, which is warmed by the Sun. In the middle of the greenhouse you put a very tall tower. The hot air from the greenhouse will rise up this tower, fast - and can drive turbines along the way. This could generate significant amounts of power, especially in countries where there is a lot of sunshine and a lot of room, such as Australia.
See a video of this at http://www.enviromission.com.au/project/video/video.htm

Advantages

Solar energy is free - it needs no fuel and produces no waste or pollution.
In sunny countries, solar power can be used where there is no easy way to get electricity to a remote place.
Handy for low-power uses such as solar powered garden lights and battery chargers

Disadvantages

Doesn't work at night.
Very expensive to build solar power stations.
Solar cells cost a great deal compared to the amount of electricity they'll produce in their lifetime.
Can be unreliable unless you're in a very sunny climate. In the United Kingdom, solar power isn't much use except for low-power applications, as you need a very large area of solar panels to get a decent amount of power.

Is it renewable?

Solar power is renewable. The Sun will keep on shining anyway, so it makes sense to use it.

	www.sunshinesolar.co.uk solar panels and supplies
	www.indigoshop.co.uk for all sorts of fasteners - apparently velcro is often used to fix solar panels