Energy & Green Tech

Improving solar cell efficiency with a bucket of water

Looking at your cell phone, you realize the battery is low, which means you have to make another long walk into town to pay money to charge the device. By the time you get home, it's getting dark. You light the kerosene lamp ...

Energy & Green Tech

'Sun in a box' would store renewable energy for the grid

MIT engineers have come up with a conceptual design for a system to store renewable energy, such as solar and wind power, and deliver that energy back into an electric grid on demand. The system may be designed to power a ...

Energy & Green Tech

Carbon fiber can store energy in the body of a vehicle

A study led by Chalmers University of Technology, Sweden, has shown that carbon fibres can work as battery electrodes, storing energy directly. This opens up new opportunities for structural batteries, where the carbon fibre ...

Energy & Green Tech

Experiments show dramatic increase in solar cell output

In any conventional silicon-based solar cell, there is an absolute limit on overall efficiency, based partly on the fact that each photon of light can only knock loose a single electron, even if that photon carried twice ...

Engineering

AI-designed heat pumps consume less energy

In Switzerland, 50 to 60 percent of new homes are equipped with heat pumps. These systems draw in thermal energy from the surrounding environment—such as from the ground, air, or a nearby lake or river—and turn it into ...

Energy & Green Tech

Explaining the plummeting cost of solar power

The dramatic drop in the cost of solar photovoltaic (PV) modules, which has fallen by 99 percent over the last four decades, is often touted as a major success story for renewable energy technology. But one question has never ...

Energy & Green Tech

Scientists pioneer a new way to turn sunlight into fuel

The quest to find new ways to harness solar power has taken a step forward after researchers successfully split water into hydrogen and oxygen by altering the photosynthetic machinery in plants.

Energy & Green Tech

New rechargeable aqueous battery challenges lithium-ion dominance

A new rechargeable high voltage manganese dioxide zinc battery, exceeding the 2 V barrier in aqueous zinc chemistry, is the latest invention by City College of New York researchers. With a voltage of 2.45-2.8V, the alkaline ...

page 1 from 23

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