Energy recycling

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Energy recycling is the energy recovery process of using energy that would normally be wasted, usually by converting it into electricity or thermal energy. Undertaken at manufacturing facilities, power plants, and large institutions such as hospitals and universities, it significantly increases efficiency, thereby reducing energy costs and greenhouse gas pollution simultaneously. The process is noted for its potential to mitigate global warming profitably. [1] [2] This work is usually done in the form of combined heat and power (also called cogeneration) or waste heat recovery.

Contents

Forms of energy recycling

Waste heat recovery

Waste heat recovery is a process that captures excess heat that would normally be discharged at manufacturing facilities and converts it into electricity and steam, or returns energy to the manufacturing process in the form of heated air, water, glycol, or oil. A "waste heat recovery boiler" contains a series of water-filled tubes placed throughout the area where heat is released. When high-temperature heat meets the boiler, steam is produced, which in turn powers a turbine that creates electricity. This process is similar to that of other fired boilers, but in this case, waste heat replaces a traditional flame. No fossil fuels are used in this process. Metals, glass, pulp and paper, silicon and other production plants are typical locations where waste heat recovery can be effective. [1]

Combined heat and power (CHP)

Combined heat and power (CHP), also called cogeneration, is, according to the U.S. Environmental Protection Agency, “an efficient, clean, and reliable approach to generating electricity and heat energy from a single fuel source. By installing a CHP system designed to meet the thermal and electrical base loads of a facility, CHP can greatly increase the facility's operational efficiency and decrease energy costs. At the same time, CHP reduces the emission of greenhouse gases, which contribute to global climate change.” When electricity is produced on-site with a CHP plant, excess heat is recycled to produce both processed heat and additional power. [3] [4]

Waste heat recovery from air conditioning

Waste heat recovery from air conditioning is also used as an alternative to wasting heat to the atmosphere from chiller plants. Heat recovered in summer from chiller plants is stored in Thermalbanks [5] in the ground and recycled back to the same building in winter via a heat pump to provide heating without burning fossil fuels. This elegant approach saves energy - and carbon - in both seasons by recycling summer heat for winter use.

Some companies offer products to install on the HVAC Condenser Unit, to collect waste heat that the condenser is supposed to evacuate in the air, to heat up heat-producing devices like water heaters. Those devices are called heat recovery units (HRU). For residential applications, some units available are : HotSpot Energy Heat Recovery Unit [6] or LG Heat Recovery Units [7]

For industrial applications, these units are usually called waste heat recovery unit (WHRU).

Heat pumps

Heat pumps and thermal energy storage are classes of technologies that can enable the recycling of energy that would otherwise be inaccessible due to a temperature that is too low for use or a time lag between when the energy is available and when it is needed. While enhancing the temperature of available renewable thermal energy, heat pumps have the additional property of leveraging electrical power (or in some cases mechanical or thermal power) by using it to extract additional energy from a low quality source (such as seawater, lake water, the ground, the air, or waste heat from a process). Innovation efforts are underway now for full electrification of industry, including with Industry Heat Pumps [8] at levels of efficiency between COP 5 & 9 using multi-stage thermal recycling via refrigerant tuned Heat Pump Modules.

Thermal storage

Thermal storage technologies allow heat or cold to be stored for periods of time ranging from hours or overnight to interseasonal, and can involve storage of sensible energy (i.e. by changing the temperature of a medium) or latent energy (i.e. through phase changes of a medium, such between water and slush or ice). Short-term thermal storages can be used for peak-shaving in district heating or electrical distribution systems. Kinds of renewable or alternative energy sources that can be enabled include natural energy (e.g. collected via solar-thermal collectors, or dry cooling towers used to collect winter's cold), waste energy (e.g. from HVAC equipment, industrial processes or power plants), or surplus energy (e.g. as seasonally from hydropower projects or intermittently from wind farms). The Drake Landing Solar Community (Alberta, Canada) is illustrative. Borehole thermal energy storage allows the community to get 97% of its year-round heat from solar collectors on the garage roofs, with most of the heat collected in summer. [9] [10] Types of storages for sensible energy include insulated tanks, borehole clusters in substrates ranging from gravel to bedrock, deep aquifers, or shallow lined pits that are insulated on top. Some types of storage are capable of storing heat or cold between opposing seasons (particularly if very large), and some storage applications require inclusion of a heat pump. Latent heat is typically stored in ice tanks or what are called phase-change materials (PCMs).

Current system

Both waste heat recovery and CHP constitute "decentralized" energy production, which is in contrast to traditional "centralized" power generated at large power plants run by regional utilities. [4] The “centralized” system has an average efficiency of 34 percent, requiring about three units of fuel to produce one unit of power. [11] By capturing both heat and power, CHP and waste heat recovery projects have higher efficiencies.

A 2007 Department of Energy study found the potential for 135,000 megawatts of CHP in the U.S., [12] and a Lawrence Berkley National Laboratory study identified about 64,000 megawatts that could be obtained from industrial waste energy, not counting CHP. [13] These studies suggest about 200,000 megawatts—or 20% -- of total power capacity that 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. [14] Indeed, as of 2005, about 42 percent of U.S. greenhouse gas pollution came from the production of electricity and 27 percent from the production of heat. [15] [16]

Advocates contend that recycled energy costs less and has lower emissions than most other energy options in current use. [17]

Currently RecyclingEnergy Int. Corp. takes advantage of recycling energy in heat recovery ventilation and latent heat pump and CHCP. [18]

History

Perhaps the first modern use of energy recycling was done by Thomas Edison. His 1882 Pearl Street Station, the world's first commercial power plant, was a CHP plant, producing both electricity and thermal energy while using waste heat to warm neighboring buildings. [19] Recycling allowed Edison's plant to achieve approximately 50 percent efficiency.

By the early 1900s, regulations emerged to promote rural electrification through the construction of centralized plants managed by regional utilities. These regulations not only promoted electrification throughout the countryside, but they also discouraged decentralized power generation, such as CHP. They even went so far as to make it illegal for non-utilities to sell power. [20]

By 1978, Congress recognized that efficiency at central power plants had stagnated and sought to encourage improved efficiency with the Public Utility Regulatory Policies Act (PURPA), which encouraged utilities to buy power from other energy producers. CHP plants proliferated, soon producing about 8 percent of all energy in the U.S. [21] However, the bill left implementation and enforcement up to individual states, resulting in little or nothing being done in many parts of the country.

In 2008 Tom Casten, chairman of Recycled 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." [22]

Outside the U.S., energy recycling is more common. Denmark is probably the most active energy recycler, obtaining about 55% of its energy from CHP and waste heat recovery. Other large countries, including Germany, Russia, and India, also obtain a much higher share of their energy from decentralized sources. [21] [22]

See also

Related Research Articles

<span class="mw-page-title-main">Power station</span> Facility generating electric power

A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.

<span class="mw-page-title-main">Distributed generation</span> Decentralised electricity generation

Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices referred to as distributed energy resources (DER).

<span class="mw-page-title-main">Combined cycle power plant</span> Assembly of heat engines that work in tandem from the same source of heat

A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turbine (CCGT) plant, which is a kind of gas-fired power plant. The same principle is also used for marine propulsion, where it is called a combined gas and steam (COGAS) plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs.

<span class="mw-page-title-main">Cogeneration</span> Simultaneous generation of electricity and useful heat

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.

<span class="mw-page-title-main">Sustainable energy</span> Energy that responsibly meets social, economic, and environmental needs

Energy is sustainable if it "meets the needs of the present without compromising the ability of future generations to meet their own needs." Definitions of sustainable energy usually look at its effects on the environment, the economy, and society. These impacts range from greenhouse gas emissions and air pollution to energy poverty and toxic waste. Renewable energy sources such as wind, hydro, solar, and geothermal energy can cause environmental damage but are generally far more sustainable than fossil fuel sources.

<span class="mw-page-title-main">Fossil fuel power station</span> Facility that burns fossil fuels to produce electricity

A fossil fuel power station is a thermal power station which burns a fossil fuel, such as coal, oil, or natural gas, to produce electricity. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating gas engine. All plants use the energy extracted from the expansion of a hot gas, either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have their efficiency limited by the Carnot efficiency and therefore produce waste heat.

<span class="mw-page-title-main">District heating</span> Centralized heat distribution system

District heating is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from factories and nuclear power electricity generation. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, district heating with combined heat and power (CHPDH) is the cheapest method of cutting carbon emissions, and has one of the lowest carbon footprints of all fossil generation plants.

Micro combined heat and power, micro-CHP, μCHP or mCHP is an extension of the idea of cogeneration to the single/multi family home or small office building in the range of up to 50 kW. Usual technologies for the production of heat and power in one common process are e.g. internal combustion engines, micro gas turbines, stirling engines or fuel cells.

<span class="mw-page-title-main">Thermal power station</span> Power plant that generates electricity from heat energy

A thermal power station, also known as a thermal power plant, is a type of power station in which the heat energy generated from various fuel sources is converted to electrical energy. The heat from the source is converted into mechanical energy using a thermodynamic power cycle. The most common cycle involves a working fluid heated and boiled under high pressure in a pressure vessel to produce high-pressure steam. This high pressure-steam is then directed to a turbine, where it rotates the turbine's blades. The rotating turbine is mechanically connected to an electric generator which converts rotary motion into electricity. Fuels such as natural gas or oil can also be burnt directly in gas turbines, skipping the steam generation step. These plants can be of the open cycle or the more efficient combined cycle type.

Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat technologies include renewable biofuels, solar heating, geothermal heating, heat pumps and heat exchangers. Insulation is almost always an important factor in how renewable heating is implemented.

<span class="mw-page-title-main">Waste-to-energy</span> Process of generating energy from the primary treatment of waste

Waste-to-energy (WtE) or energy-from-waste (EfW) refers to a series of processes designed to convert waste materials into usable forms of energy, typically electricity or heat. As a form of energy recovery, WtE plays a crucial role in both waste management and sustainable energy production by reducing the volume of waste in landfills and providing an alternative energy source.

<span class="mw-page-title-main">Waste heat</span> Heat that is produced by a machine that uses energy, as a byproduct of doing work

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 than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms, for example, incandescent light bulbs get hot, a refrigerator warms the room air, a building gets hot during peak hours, an internal combustion engine generates high-temperature exhaust gases, and electronic components get warm when in operation.

<span class="mw-page-title-main">Energy recovery</span>

Energy recovery includes any technique or method of minimizing the input of energy to an overall system 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.

<span class="mw-page-title-main">Organic Rankine cycle</span> Variation on the Rankine thermodynamic cycle

In thermal engineering, the organic Rankine cycle (ORC) is a type of thermodynamic cycle. It is a variation of the Rankine cycle named for its use of an organic, high-molecular-mass fluid whose vaporization temperature is lower than that of water. The fluid allows heat recovery from lower-temperature sources such as biomass combustion, industrial waste heat, geothermal heat, solar ponds etc. The low-temperature heat is converted into useful work, that can itself be converted into electricity.

<span class="mw-page-title-main">Waste heat recovery unit</span> Energy recovery heat exchanger

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 cogeneration. Waste heat may be extracted from sources such as hot flue gases from a diesel generator, steam from cooling towers, or even waste water from cooling processes such as in steel cooling.

<span class="mw-page-title-main">Photovoltaic thermal hybrid solar collector</span>

Photovoltaic thermal collectors, typically abbreviated as PVT collectors and also known as hybrid solar collectors, photovoltaic thermal solar collectors, PV/T collectors or solar cogeneration systems, are power generation technologies that convert solar radiation into usable thermal and electrical energy. PVT collectors combine photovoltaic solar cells, which convert sunlight into electricity, with a solar thermal collector, which transfers the otherwise unused waste heat from the PV module to a heat transfer fluid. By combining electricity and heat generation within the same component, these technologies can reach a higher overall efficiency than solar photovoltaic (PV) or solar thermal (T) alone.

The Business Energy Investment Tax Credit (ITC) is a U.S. federal corporate tax credit that is applicable to commercial, industrial, utility, and agricultural sectors. Eligible technologies for the ITC are solar water heat, solar space heat, solar thermal electric, solar thermal process heat, photovoltaics, wind, biomass, geothermal electric, fuel cells, geothermal heat pumps, CHP/cogeneration, solar hybrid lighting, microturbines, and geothermal direct-use.

Renewable thermal energy is the technology of gathering thermal energy from a renewable energy source for immediate use or for storage in a thermal battery for later use.

Denmark is a leading country in renewable energy production and usage. Renewable energy sources collectively produced 81% of Denmark's electricity generation in 2022, and are expected to provide 100% of national electric power production from 2030. Including energy use in the heating/cooling and transport sectors, Denmark is expected to reach 100% renewable energy in 2050, up from the 34% recorded in 2021.

<span class="mw-page-title-main">Solar augmented geothermal energy</span> Solar-heated artificial underground lake

Solar augmented geothermal energy (SAGE) is an advanced method of geothermal energy that creates a synthetic geothermal storage resource by heating a natural brine with solar energy and adding enough heat when the sun shines to generate power 24 hours a day. The earth is given enough energy in one hour to provide all electrical needs for a year. Available energy is not the issue, but energy storage is the problem and SAGE creates effective storage and electrical power delivery on demand. This technology is especially effective for geothermal wells that have demonstrated inconsistent heat or idle oil or gas fields that have demonstrated the proper geology and have an abundance of solar.

References

  1. 1 2 "The Unsung Solution: What rhymes with waste heat recovery?". Orion Magazine, November/December 2007 . Archived from the original on 2014-03-23. Retrieved 2008-02-02.
  2. ↑ "Solar Panel Recycling Solution".
  3. ↑ "Combined Heat and Power Partnership". U.S. Environmental Protection Agency . 11 June 2015.
  4. 1 2 "Clean Heat and Power Association". Archived from the original on 2007-07-01.
  5. ↑ 'Thermalbanks'
  6. ↑ "Residential Heat Recovery Water Heaters | Free Hot Water | HotSpot Energy LLC".
  7. ↑ "Heat Recovery Units (HRU)".
  8. ↑ "High Temperature Industry Heat Pumps examples".
  9. ↑ Wong, Bill (June 28, 2011), "Drake Landing Solar Community" Archived 2016-03-04 at the Wayback Machine , IDEA/CDEA District Energy/CHP 2011 Conference, Toronto, pp. 1–30, retrieved 21 April 2013
  10. ↑ Wong B., Thornton J. (2013). Integrating Solar & Heat Pumps. Archived 2013-10-15 at the Wayback Machine Renewable Heat Workshop.
  11. ↑ "Electricity". U.S. Department of Energy.
  12. ↑ Bruce Hedman, Energy and Environmental Analysis/USCHPA, "Combined Heat and Power and Heat Recovery as Energy Efficiency Options", Briefing to Senate Renewable Energy Caucus, September 10, 2007, Washington DC.
  13. ↑ Bailey, Owen; Worrell, Ernst (2005). "Clean Energy Technologies: a Preliminary Inventory of the Potential for Electricity Generation, Lawrence Berkley National Laboratory, 4/05" (PDF). doi:10.2172/843010.{{cite journal}}: Cite journal requires |journal= (help)
  14. ↑ "The Energy Information Administration, Existing Capacity by Energy Source, 2006".
  15. ↑ "Inventory of U.S. Greenhouse Gas Emissions and Sinks". U.S. Environmental Protection Agency . Archived from the original on 2011-12-18.
  16. ↑ "Emissions of Greenhouse Gases in the United States 2005". U.S. Energy Information Administration .
  17. ↑ "Recycled Energy Development, "What RED Does"". Archived from the original on 2009-09-13. Retrieved 2009-09-21.
  18. ↑ RecyclingEnergy
  19. ↑ "World's First Commercial Power Plant Was a Cogeneration Plant". Cogeneration Technologies . Archived from the original on 2008-04-25. Retrieved 2008-02-02.
  20. ↑ "Testimony of Sean Casten before Senate subcommittee on Energy, Natural Resources, and Infrastructure, 5/27/07" (PDF).
  21. 1 2 "World Survey of Decentralized Energy, 5/06".
  22. 1 2 'Recycling' Energy Seen Saving Companies Money. By David Schaper. May 22, 2008. Morning Edition. National Public Radio.
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