Solar energy: energy from sunlight

Some street lights are solar powered.  Getty

Some street lights are solar powered.  Getty

Solar energy means using the energy of sunlight to provide electricity, to heat water, and to heat or cool our homes.

Sunlight is a clean, renewable source of energy. It is a sustainable resource, meaning it doesn't run out, but can be maintained. (Coal and gas are not sustainable or renewable: once they are gone, there is none left) More and more people are wanting to use clean, renewable energy such as solar, wind, geothermal steam and others. It is called 'Green Power'.  

An array of PV panels at a solar farm. Getty Images

An array of PV panels at a solar farm. Getty Images

Photovoltaic (PV) solar cells directly convert sunlight into electricity.

The simplest cells are used to operate wrist watches and calculators, and more complicated systems are used to light houses. PV cells are combined into modules called arrays, and the number of arrays used determines the amount of electricity produced. For example, a large number of arrays would be needed to generate electricity for a power plant. A power plant can also use a concentrating solar power system where sunlight is focused with mirrors to create a high-intensity heat source to produce steam or mechanical power to run a generator that creates electricity.

Solar panels mounted on the roof heat water. Windows and glass doors let in light and the sun's heat. Getty Images.

Solar panels mounted on the roof heat water. Windows and glass doors let in light and the sun's heat. Getty Images.

Solar water heating systems have two main parts: a solar collector and a storage tank. Generally, the collector is a thin, flat, rectangular box with a transparent cover mounted on the roof, facing the sun. The sun heats an absorber plate in the collector, and this heats the water running through tubes inside the collector. The heated water is pumped or moved by gravity into the storage tank. Solar water heaters can use about two thirds less energy than those of other methods. Heat from a solar collector can power heating and cooling systems in buildings.

Battery storage for solar energy

One of the problems with solar power is that when the sun doesn't shine there is no power. Since 2016 there have been developed, batteries that can store the energy, so that it can be used when there is no sun. The technology is being improved all the time and now people with solar panels can have a storage battery so that they can use solar energy in both day and night.

You can read about storing solar energy here

Passive solar heating

Some buildings are designed for passive solar heating, and do not need a solar collector. Passive solar heating is when opportunities are made for the sun to shine into the building to warm it up. The walls and floors are made with materials that absorb and store the sun's heat, and they heat up during the day and release the heat at night. This is called direct gain.

In cold places in the northern hemisphere big windows are put in the south side of the building, letting in much sunlight. The inside of the buildings are therefore well lit, further reducing use of electricity. Heating bills can be half the size of those for a building requiring electrical or other heating. Building designs make sure that the longest walls run east to west, to allow more sunlight to enter in winter than in summer, with shades and overhangs to reduce summer heat.

Solar Cookers

Solar cookers can cook just about any food that a conventional oven can. A basic cooker is an insulated box with a glass top. Heat from concentrated sunlight gets trapped in the box and can be used to heat food placed in the box.



Read about how solar panels work:

Read about how to make a simple solar cooker...make sure a grown up helps you:

Watch a video about solar energy :

Watch a video:  How does Sunlight turn into Electricity?