Green energy includes natural energetic processes that can be harnessed with minimal pollution. Anaerobic digestion, geothermal power, wind power, small-scale hydropower, solar energy, biomass power, tidal power, and wave power fall under such a category.
Some definitions also include nuclear power as green energy. Others disagree, claiming that the problems associated with radioactive waste pose an unacceptable risk to the environment. No power source is entirely impact-free; all energy sources require energy and give rise to some degree of pollution from manufacture of the technology.
In the United States, one of the main problems to the advancement of green energy is the centralized supply infrastructure. Renewable resources, due to the amount of space they require, are often located in remote areas where there is a lower energy demand. The current infrastructure would make transporting this energy to high demand areas, such as urban centers, highly inefficient. In addition, despite the amount of renewable energy produced or the economic viability of such technologies only about 20 percent will be able to be incorporated into the grid.
A decentralized grid would increase efficiency by reducing the energy lost in transmission and would reduce the need for power lines. Merging heat and power in this system would increase efficiency by up to 80-90%. Another concept for remodeling the electrical grid would be to beam microwaves to processing plants from extraterrestrial sites. So clearly, this exciting new application of physics involves field work, research and development, and electrical engineering.