We need alternative energy because eventually we will loose our fossil fuels.
The sun shines on the solar panel and the solar panel absorbs the sun`s light and then the panels transfer the light into energy.
The wind turbines are blown by the wind and when they turn it makes energy.
Biomass is when you burn plants and harness the energy then use it.
Hydroelectric energy is a lot like wind energy but the turbines are turned by water and the turbines are usually inside the inside of a dam and also like wind energy by the way that it is turned by a force causing the turbine to turn making hydroelectric energy that can be used.
Geothermal energy is energy that is heat coming from the core. Example heat forcing water or magma out of the ground and if it were water coming out of the ground it would be very hot.