About 30% of this energy is returned to space from the atmosphere. Since clouds, atmosphere and night are absent in space, space-based solar power would be able to capture solar energy from space and transfer it to earth. The idea is to build giant solar farms in space that will harvest energy from sunlight in space and transmit it wirelessly to Earth with a laser or microwave beam. The lifespan of the sun is estimated to be 4–5 billion years, making space solar power a long-term energy solution (U.S. Department of Energy, 2014). 2. Human PowerHuman power is the power produced by the human body, from human steps to button presses, humans constantly consume energy, and since energy can be converted from one form to another, researchers are working to convert these movements in electrical energy. Scientists are working to increase the energy efficiency of the human body and increase it, so perhaps in the near future humans will be able to charge the batteries of their phones simply by moving their body in their pocket or with a few taps of their fingers when pressing on the screen (Umair Irfan, 2012). 3. Solar