1.6 Overview of renewable energy sources
All the renewable energy sources will be covered in more detail over the coming weeks of the course, but here’s a short introduction to the main types, starting with solar derived forms.
Direct solar forms
Solar radiation can be converted into useful energy directly, using various technologies. Absorbed in solar ‘collectors’, it can provide hot water for washing or space heating. Buildings can also be designed with ‘passive solar’ features that enhance the sun’s contribution to their space heating and lighting requirements.
The sun’s rays can also be concentrated by mirrors to provide high-temperature steam that can be used to power electricity generators.
Solar radiation can also be converted directly into electricity using photovoltaic (PV) panels, normally mounted on the roofs or facades of buildings or as arrays in fields.
Indirect solar energy
Solar radiation can be converted to useful energy indirectly, via the other energy forms it causes.
Bioenergy, powered by solar-powered photosynthesis in plants, is an indirect manifestation of solar energy.
Solar radiation warms the oceans, adding water vapour to the air. This condenses as rain to feed rivers, into which dams and turbines can be located to extract hydropower from the flowing water.
Sunlight heats the tropics to a greater degree than the polar regions, resulting in massive heat flows towards the poles, carried by currents in the oceans and the atmosphere. The energy in such currents can be harnessed by wind turbines.
Where winds blow over long stretches of ocean they create waves, and wave power devices are being developed to extract their energy.
However there are also non-solar forms of renewable energy.