Energy & Green Tech

Inertia and the power grid: A guide without the spin

The power grid is evolving to include ever-higher levels of wind and solar generation—which do not provide inertia, historically a key source of grid reliability. Should system planners and operators panic? A new video ...

Energy & Green Tech

Hydropower plants to support solar and wind energy in West Africa

Hydropower plants can support solar and wind power, rather unpredictable by nature, in a climate-friendly manner. A new study in the scientific journal Nature Sustainability has now mapped the potential for such "solar-wind-water" ...

Energy & Green Tech

Smarter energy use is key to a greener future

LED lightbulbs, programmable thermostats, high-density insulation and electric vehicles—despite these innovations, about two-thirds of the energy produced in the U.S. is lost to inefficiencies, according to national studies.

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Energy

In physics, energy (from the Greek ἐνέργεια - energeia, "activity, operation", from ἐνεργός - energos, "active, working") is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law. Different forms of energy include kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. The forms of energy are often named after a related force.

Any form of energy can be transformed into another form, but the total energy always remains the same. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.

Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy relative to the Earth.

This text uses material from Wikipedia, licensed under CC BY-SA