Sustainable energy or clean energy is the practice of using energy in a way that "meets the needs of the present without compromising the ability of future generations to meet their own needs."[1][2]
Meeting the world's needs for energy in a sustainable way is widely considered to be one of the greatest challenges facing humanity in the 21st century. Worldwide, nearly a billion people lack access to electricity, and around 3 billion people rely on dirty fuels such as wood and animal dung for cooking. Production and consumption of energy cause around 72% of human-caused greenhouse gas emissions and are a major contributor to air pollution, which causes an estimated 7 million deaths per year. Proposed pathways for limiting global warming to 1.5 °C describe rapid implementation of low-emission methods of producing electricity, a shift towards more use of electricity in sectors such as transport, and measures to reduce energy consumption. Achieving this goal will require government policies including carbon pricing and energy-specific policies.
When referring to methods of producing energy, the term "sustainable energy" is often used interchangeably with the term "renewable energy". In general, renewable energy sources such as solar, wind, and hydroelectric energy are widely considered to be sustainable. However, particular renewable energy projects, such as the clearing of forests for production of biofuels, can lead to similar or even worse environmental damage when compared to using fossil fuel energy. There is considerable controversy over whether nuclear energy can be considered sustainable.
Wind and solar energy produced approximately 4.5% of worldwide electricity in 2015. This proportion has grown rapidly and costs are projected to continue falling, but the intermittency of these energy sources presents significant challenges.