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Energy recovery includes any technique or method of minimizing the input ofenergy to an overallsystem by theexchange of energy from one sub-system of the overall system with another. The energy can be in any form in either subsystem, but most energy recovery systems exchangethermal energy in eithersensible orlatent form.
In some circumstances the use of an enabling technology, either dailythermal energy storage orseasonal thermal energy storage (STES, which allows heat or cold storage between opposing seasons), is necessary to make energy recovery practicable. One example iswaste heat fromair conditioning machinery stored in a buffer tank to aid in night timeheating.
A common application of this principle is in systems which have anexhaust stream orwaste stream which is transferred from the system to its surroundings. Some of the energy in that flow of material (oftengaseous orliquid) may be transferred to themake-up orinput material flow. Thisinputmass flow often comes from the system's surroundings, which, being at ambient conditions, are at a lower temperature than thewaste stream. This temperature differential allowsheat transfer and thus energy transfer, or in this case, recovery. Thermal energy is often recovered from liquid or gaseous waste streams tofreshmake-upair andwater intakes inbuildings, such as for theHVAC systems, or process systems.
Energy consumption is a key part of most human activities. This consumption involvesconverting one energy system to another, for example: The conversion of mechanical energy to electrical energy, which can then power computers, light, motors etc. The input energy propels the work and is mostly converted to heat or follows the product in the process as output energy. Energy recovery systems harvest the output power and provide this as input power to the same or another process.
An energy recovery system will close thisenergy cycle to prevent the input power from being released back to nature and rather be used in other forms of desired work.
Electric Turbo Compounding (ETC) is a technology solution to the challenge of improving thefuel efficiency of gas and diesel engines by recovering waste energy from the exhaust gases.
There is a large potential for energy recovery in compact systems like large industries and utilities. Together withenergy conservation, it should be possible to dramatically reduceworld energy consumption. The effect of this will then be:
In 2008Tom Casten, chairman ofRecycled Energy Development, said that "We think we could make about 19 to 20 percent of U.S. electricity with heat that is currently thrown away by industry."[7]
A 2007 Department of Energy study found the potential for 135,000 megawatts ofcombined heat and power (which uses energy recovery) in the U.S.,[8] and a Lawrence Berkley National Laboratory study identified about 64,000 megawatts that could be obtained from industrial waste energy, not counting CHP.[9] These studies suggest that about 200,000 megawatts, or 20%, of total power capacity could come fromenergy recycling in the U.S. Widespread use of energy recycling could therefore reduce global warming emissions by an estimated 20 percent.[10] Indeed, as of 2005, about 42% of U.S. greenhouse gas pollution came from the production of electricity and 27% from the production of heat.[11][12]
It is difficult to quantify the environmental impact of a global energy recovery implementation in some sectors. The main impediments are:[citation needed]
