Energy storage

Energy storage is the capture of energy produced at one time for use at a later time. A device that stores energy is sometimes called an accumulator. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms.

Some technologies provide short-term energy storage, while others can endure for much longer.

A wind-up clock stores potential energy (in this case mechanical, in the spring tension), a rechargeable battery stores readily convertible chemical energy to operate a mobile phone, and a hydroelectric dam stores energy in a reservoir as gravitational potential energy. Fossil fuels such as coal and gasoline store ancient energy derived from sunlight by organisms that later died, became buried and over time were then converted into these fuels. Food (which is made by the same process as fossil fuels) is a form of energy stored in chemical form.

Renewable energy

Renewable energy is generally defined as energy that is collected from resources which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation, and rural (off-grid) energy services.

Based on REN21's 2014 report, renewables contributed 19 percent to humans' global energy consumption and 22 percent to their generation of electricity in 2012 and 2013, respectively. This energy consumption is divided as 9% coming from traditional biomass, 4.2% as heat energy (non-biomass), 3.8% hydro electricity and 2% is electricity from wind, solar, geothermal, and biomass. Worldwide investments in renewable technologies amounted to more than US$214 billion in 2013, with countries like China and the United States heavily investing in wind, hydro, solar and biofuels.

100% renewable energy

The incentive to use 100% renewable energy for electricity, heating and cooling and transport is motivated by global warming, pollution and other ecological as well as economic and energy security concerns. Shifting the total global primary energy supply to renewable sources requires a transition of the energy system. In 2013 the Intergovernmental Panel on Climate Change has said that there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. Renewable energy use has grown much faster than even advocates anticipated.

In 2014 renewables such as wind, geothermal, solar, biomass and burnt waste provided 19% of the total world final energy consumption, roughly half of it traditional use of biomass. The most important sector electricity with a renewable share of 22.8%, most of it coming from water power with a share of 16.6%, followed by wind with 3.1%. Several places run their grids almost exclusively on renewable energy. At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. Also, Professors S. Pacala and Robert H. Socolow have developed a series of “Climate stabilization wedges” that can allow us to maintain our quality of life while avoiding catastrophic climate change, and "renewable energy sources," in aggregate, constitute the largest number of their "wedges."

Renewable Energy (journal)

Renewable Energy is a monthly peer-reviewed scientific journal covering research on renewable energy, sustainable energy and the energy transition. It is published by Elsevier and the editor-in-chief is S.A. Kalogirou (Cyprus University of Technology). According to the Journal Citation Reports, the journal has a 2013 impact factor of 3.361.

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