Solar energy.

Today one of the most popular and well known alternative forms of energy is solar power. There are two types of solar energy, Passive Solar - which uses natural processes without mechanical equipment, and additional electrical or gas energy to operate, and Active Solar - which uses nature's resources with the inclusion of mechanical equipment and hardware driven by electricity and gas. Solar energy has many advantages. It is an easy, quiet, reliable source of …

…to use fresh-air ventilation. Solar energy is the best form of energy because it is not depleting any of our natural resources in the process, but instead uses one of our most powerful resources to benefit us and help us to live in a comfortable environment. "Passive solar buildings are environmentally responsive and use nature's elements in providing shelter and comfort to people in a manner that is healthy and minimally destructive of the environment."