The sun has been providing energy to our planet Earth since the solar system formed, over four and a half billion years ago. It seems pretty obvious that all the light we get during the day comes from the sun, but there’s a lot more energy than that coming our way from the centre of the solar system and we are getting better at capturing it and using its power.
The sun is a pretty amazing energy source, and more energy hits the earth in an hour from the sun than all the people in the world use in a whole year! But don’t take our word for it, listen to Bill Nye (the science guy) explain it in this video.
Science has invented ways to harness that energy from the sun, and we can use that to do everything from heat up water to generating electricity, and even making new kinds of clean fuel for cars and even rockets!
How do we catch energy from the sun and make it work for us?
There are two kinds of energy we can use from the sun, heat energy and light energy, as explained here.
Thermal solar energy
The heat from the sun can be used directly to heat up things, like water. Many houses have installed solar water heaters so they use less power to heat water for using inside the house. Some swimming pools are also heated this way so they can be used for more of the year and not just in summer.
Solar collector arrays
In solar collector arrays, big rows of mirrors are used to reflect the light of the sun on to a very small area which heats up to a very high temperature. The heat is so great it can turn water into steam, and that steam can be used to drive turbines for generating electricity. This type of solar thermal energy can be used in places where the sun shines almost all the time, such as in deserts, and there are a number of these systems already in operation around the world.
The video below details a solar array power station in Southern Spain that stores a molten salt solution so electricity can be generated 24 hours a day.
Scientists figured out over 100 years ago that light energy could be used to kick start an electrical current, and more recently that we could store that electricity in batteries or use it to power electrical appliances. This is what is going on in solar panels, also called photovoltaic cells (photo means light, and voltaic relates to electricity) as you can see on this page.
Additionally, this video from GreenLiving Solar gives a good overview of the process.
Solar energy and your home
The efficiency of solar panels has been increasing since the 1950s, and battery technology is also improving. It’s now possible to run a household of energy efficient appliances purely from solar generated electricity, though it’s still a bit more expensive than buying electricity from other sources. The solar power can be used directly if the sun is out, or stored to use at night or when the sun doesn’t shine.
There are plenty of solar powered gadgets around now, like garden lights, security lights and torches. Most of these gadgets have their own inbuilt solar panel and battery, and most will pick up enough sunlight on a sunny day to light up for a couple of hours, or maybe even more in the long days of summer. However, to power a whole home needs a lot more electricity, while a small torch might use only a few watts of electricity, a house uses thousands of watts, or kilowatts (kilo means a thousand). This means up to a dozen or more solar panels, as well as battery storage for those times the sun doesn’t shine. You can see some sample calculations for different sized houses on this page.
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A whole town might use a different type of system, such as the solar thermal arrays mentioned earlier, which could potentially provide electricity for a town of 10-20,000 homes. Alternatively every home could have its own solar panels.
However solar energy is harnessed, it’s a useful way to reduce reliance on the limited resources of coal, oil and gas left in the world. Any use of renewable power also lessens greenhouse gas emissions so will help the environment in the long term too.