Energy & Green Tech

Green roofs are worth the cost for urban residents

Plant-covered roofs have become a regular sight in Portland, Oregon. The city is a leader in incorporating green infrastructure for stormwater management, including free street trees, rebates for small residential housing ...

Energy & Green Tech

These solar panels pull in water vapor to grow crops in the desert

Using a unique hydrogel, scientists in Saudi Arabia created a solar-driven system that successfully grows spinach by using water drawn from the air while producing electricity. The proof-of-concept design, described March ...

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 ...


Clever coating turns lampshades into indoor air purifiers

Indoor air pollution may have met its match. Today, scientists will report that they have designed catalyst-coated lampshades that transform indoor air pollutants into harmless compounds. The lampshades work with halogen ...


New engine capability accelerates advanced vehicle research

In the quest for advanced vehicles with higher energy efficiency and ultra-low emissions, Oak Ridge National Laboratory researchers are accelerating a research engine that gives scientists and engineers an unprecedented view ...


Next-gen heat pump could cut energy bills and carbon emissions

Researchers from the University of Glasgow have developed a new type of heat pump, a flexible heat pump technology, which could help households save on their energy bills and contribute towards net-zero emissions goals.

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In physics and thermodynamics, heat is the process of energy transfer from one body or system to another due to a difference in temperature. In thermodynamics, the quantity TdS is used as a representative measure of the (inexact) heat differential δQ, which is the absolute temperature of an object multiplied by the differential quantity of a system's entropy measured at the boundary of the object.

A related term is thermal energy, loosely defined as the energy of a body that increases with its temperature. Heat is also loosely referred to as thermal energy, although many definitions require this thermal energy to actually be in the process of movement between one body and another to be technically called heat (otherwise, many sources prefer to continue to refer to the static quantity as "thermal energy"). Heat is also known as "Energy".

Energy transfer by heat can occur between objects by radiation, conduction and convection. Temperature is used as a measure of the internal energy or enthalpy, that is the level of elementary motion giving rise to heat transfer. Energy can only be transferred by heat between objects - or areas within an object - with different temperatures (as given by the zeroth law of thermodynamics). This transfer happens spontaneously only in the direction of the colder body (as per the second law of thermodynamics). The transfer of energy by heat from one object to another object with an equal or higher temperature can happen only with the aid of a heat pump, which does work.

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