What is the Earth's primary source of energy?

The primary source of energy for nearly Earth's entire Ecosystem is the sun. The sunlight has a direct effect on all ecosystems. This is especially true for the growth of plants using photosynthesis.

It is an important source of renewable energy and its technologies are broadly characterized as either passive solar or active solar depending on how they capture and distribute solar energy or convert it into solar power. Active solar techniques include the use of photovoltaic systems, concentrated solar power and solar water heating to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light-dispersing properties, and designing spaces that naturally circulate air.