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Energy recovery includes any technique or method of minimizing the input of
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
to an overall
system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment (systems), environment, is described by its boundaries, ...
by the exchange 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 exchange thermal energy in either sensible or latent form. In some circumstances the use of an enabling technology, either daily thermal energy storage or seasonal thermal energy storage (STES, which allows heat or cold storage between opposing seasons), is necessary to make energy recovery practicable. One example is
waste heat Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...
from
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
machinery stored in a buffer tank to aid in night time heating.


Principle

A common application of this principle is in systems which have an ''exhaust stream'' or ''waste stream'' which is transferred from the system to its surroundings. Some of the energy in that flow of material (often
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
eous or
liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
) may be transferred to the ''make-up'' or ''input'' material flow. This ''input''
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
flow often comes from the system's surroundings, which, being at ambient conditions, are at a lower temperature than the ''waste stream''. This temperature differential allows
heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
and thus energy transfer, or in this case, recovery. Thermal energy is often recovered from liquid or gaseous waste streams to ''fresh'' ''make-up'' air and
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
intakes in
buildings A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and funct ...
, such as for the
HVAC Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HV ...
systems, or process systems.


System approach

Energy consumption Energy consumption is the amount of energy used. Biology In the body, energy consumption is part of energy homeostasis. It derived from food energy. Energy consumption in the body is a product of the basal metabolic rate and the physical activity ...
is a key part of most human activities. This consumption involves converting 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 this energy cycle to prevent the input power from being released back to nature and rather be used in other forms of desired work.


Examples

* Heat recovery is implemented in heat sources like e.g. a
steel mill A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-finish ...
. Heated
cooling water Cooling tower and water discharge of a nuclear power plant Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and non ...
from the process is sold for heating of homes, shops and offices in the surrounding area. * Regenerative braking is used in electric cars, trains, heavy cranes etc. where the energy consumed when elevating the potential is returned to the electric supplier when released. * Active pressure reduction systems where the differential pressure in a pressurized fluid flow is recovered rather than converted to heat in a pressure reduction valve and released. *
Energy recovery ventilation Energy recovery ventilation (ERV) is the energy recovery process in residential and commercial HVAC systems that exchanges the energy contained in normally exhausted air of a building or conditioned space, using it to treat (precondition) the inc ...
* Energy recycling *
Water heat recycling Water heat recycling (also known as drain water heat recovery, waste water heat recovery, greywater heat recovery, or sometimes shower water heat recovery) is the use of a heat exchanger to recover energy and reuse heat from drain water from vario ...
*
Heat recovery ventilation Heat recovery ventilation (HRV), also known as mechanical ventilation heat recovery (MVHR), is an energy recovery ventilation system which works between two air sources at different temperatures. Heat recovery is a method which is used to reduce ...
* Heat recovery steam generator * Cyclone Waste Heat Engine *
Hydrogen turboexpander-generator A hydrogen turboexpander-generator or generator loaded expander for hydrogen gas is an axial flow turbine or radial expander for energy recovery through which a high pressure hydrogen gas is expanded to produce work that is used to drive an electri ...
*
Thermal diode The term "thermal diode" is sometimes used for a (possibly non-electrical) device which allows heat to flow preferentially in one direction. Or, the term may be used to describe an electrical (semiconductor) diode in reference to a thermal effect o ...
*
Thermal oxidizer A thermal oxidizer (also known as thermal oxidiser, or thermal incinerator) is a process unit for air pollution control in many chemical plants that decomposes hazardous gases at a high temperature and releases them into the atmosphere. Principl ...
*
Thermoelectric Modules A thermoelectric generator (TEG), also called a Seebeck generator, is a solid state device that converts heat flux (temperature differences) directly into electrical energy through a phenomenon called the ''Seebeck effect'' (a form of thermoelec ...
*
Waste heat recovery unit A waste heat recovery unit (WHRU) is an energy recovery heat exchanger that transfers heat from process outputs at high temperature to another part of the process for some purpose, usually increased efficiency. The WHRU is a tool involved in cogen ...
s


Electric Turbo Compound (ETC)

Electric Turbo Compounding (ETC) is a technology solution to the challenge of improving the
fuel efficiency Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
of gas and diesel engines by recovering waste energy from the exhaust gases.


STES

* At a foundry in Sweden waste heat is recovered and stored in a large mass of native bedrock which is penetrated by a cluster of 140 heat exchanger equipped boreholes (155mm diameter) that are 150m deep. This store is used for heating an adjacent factory as needed, even months later. * The
Drake Landing Solar Community The Drake Landing Solar Community (DLSC) is a planned community in Okotoks, Alberta, Canada, equipped with a central solar heating system and other energy efficient technologies. This heating system is the first of its kind in North America, altho ...
in
Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
, Canada uses STES to recover and utilize natural heat that otherwise would be wasted. The community uses a cluster of boreholes in bedrock for interseasonal heat storage, and this enables obtaining 97 percent of the year-round space heating from
solar thermal collector A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and sola ...
s on the garage roofs. * Cold winter temperatures can be recovered by circulating water through a dry cooling tower and using that to chill a deep aquifer or borehole cluster. The chill is later recovered from the storage for summer air conditioning. With a
coefficient of performance The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. Higher COPs equate to higher efficiency, lower energy ( ...
(COP) of 20 to 40, this method of cooling can be ten times more efficient than conventional air conditioning.


Environmental impact

There is a large potential for energy recovery in compact systems like large industries and utilities. Together with
energy conservation Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less energy for continuous service) or changing one's behavior to use less service (f ...
, it should be possible to dramatically reduce world energy consumption. The effect of this will then be: * Reduced number of
coal-fired power plants Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...
* Reduced airborne particles, and – improved air quality * Slowing or reducing
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
* Lower fuel bills on transport * Longer availability of
crude oil Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...
* Change of industries and economies not fully researched In 2008
Tom Casten Thomas R. Casten is an American businessman, author, and activist known for his work on industrial energy recycling. Since 1977, Casten has founded and managed numerous companies and organizations associated with combined heat and power (also ca ...
, chairman of
Recycled Energy Development Recycled Energy Development, LLC (RED) aims to profitably reduce greenhouse gas emissions by capturing and recycling waste energy, especially through cogeneration and waste heat recovery. Overview RED develops, owns, and manages energy recycling ...
, 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.''"'Recycling' Energy Seen Saving Companies Money
By David Schaper. May 22, 2008.
Morning Edition ''Morning Edition'' is an American radio news program produced and distributed by NPR. It airs weekday mornings (Monday through Friday) and runs for two hours, and many stations repeat one or both hours. The show feeds live from 5:00 to 9:00 AM ...
.
National Public Radio National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other n ...
.
A 2007 Department of Energy study found the potential for 135,000 megawatts of
combined heat and power Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time. Cogeneration is a more efficient use of fuel or heat, because otherwise- wasted heat from elect ...
(which uses energy recovery) in the U.S., and a Lawrence Berkley National Laboratory study identified about 64,000 megawatts that could be obtained from industrial waste energy, not counting CHP. These studies suggest that about 200,000 megawatts, or 20%, of total power capacity could come from energy recycling in the U.S. Widespread use of energy recycling could therefore reduce global warming emissions by an estimated 20 percent. 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. It is difficult to quantify the environmental impact of a global energy recovery implementation in some sectors. The main impediments are: * Lack of efficient technologies for private homes. Heat recovery systems in private homes can have an efficiency as low as 30% or less. It may be more realistic to use energy conservation like
thermal insulation Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with s ...
or improved buildings. Many areas are more dependent on forced cooling and a system for extracting heat from dwellings to be used for other uses are not widely available. * Ineffective infrastructure. Heat recovery in particular need a short distance from producer to consumer to be viable. A solution may be to move a large consumer to the vicinity of the producer. This may have other complications. * Transport sector is not ready. With the transport sector using about 20% of the energy supply, most of the energy is spent on overcoming gravity and friction.
Electric car An electric car, battery electric car, or all-electric car is an automobile that is propelled by one or more electric motors, using only energy stored in batteries. Compared to internal combustion engine (ICE) vehicles, electric cars are quie ...
s with regenerative braking seem to be the best candidate for energy recovery. Wind systems on ships are under development. Very little work on the
airline industry An airline is a company that provides air transport services for traveling passengers and freight. Airlines use aircraft to supply these services and may form partnerships or alliances with other airlines for codeshare agreements, in which ...
is known in this field.


See also

*
Efficient energy use Efficient energy use, sometimes simply called energy efficiency, is the process of reducing the amount of energy required to provide products and services. For example, insulating a building allows it to use less heating and cooling energy to ...
*
Energy conservation Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less energy for continuous service) or changing one's behavior to use less service (f ...
* DWEER *
List of energy storage projects This is a list of energy storage power plants worldwide, other than pumped hydro storage. Many individual energy storage plants augment electrical grids by capturing excess electrical energy during periods of low demand and storing it in oth ...
* Mechanical vapor recompression *
Pinch analysis Pinch analysis is a methodology for minimising energy consumption of process (engineering), chemical processes by calculating thermodynamically feasible ''energy targets'' (or minimum energy consumption) and achieving them by optimising heat reco ...


References


External links


Energy Recovery from the Combustion of Municipal Solid Waste -EPA

26 Projects Funded: Energy Recovery Methods Studied with ASHRAE Undergraduate Grants

Heat Recovery in Industry
{{Environmental technology Energy policy