Distributed Energy Resources
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Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical
generation A generation refers to all of the people born and living at about the same time, regarded collectively. It can also be described as, "the average period, generally considered to be about 20–⁠30 years, during which children are born and gr ...
and storage performed by a variety of small,
grid Grid, The Grid, or GRID may refer to: Common usage * Cattle grid or stock grid, a type of obstacle is used to prevent livestock from crossing the road * Grid reference, used to define a location on a map Arts, entertainment, and media * News ...
-connected or distribution system-connected devices referred to as distributed energy resources (DER). Conventional
power station 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. Many ...
s, such as
coal 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 ...
-fired,
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 ...
, and
nuclear power Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced ...
ed plants, as well as hydroelectric dams and large-scale solar power stations, are centralized and often require electric energy to be transmitted over long distances. By contrast, DER systems are decentralized, modular, and more flexible technologies that are located close to the load they serve, albeit having capacities of only 10
megawatt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
s (MW) or less. These systems can comprise multiple generation and storage components; in this instance, they are referred to as
hybrid power Hybrid power are combinations between different technologies to produce power. In power engineering, the term 'hybrid' describes a combined power and energy storage system. Examples of power producers used in hybrid power are photovoltaics, ...
systems. DER systems typically use renewable energy sources, including
small hydro Small hydro is the development of hydroelectric power on a scale suitable for local community and industry, or to contribute to distributed generation in a regional electricity grid. Exact definitions vary, but a "small hydro" project is less ...
, biomass,
biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
,
solar power Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovolta ...
,
wind power Wind power or wind energy is mostly the use of wind turbines to generate electricity. Wind power is a popular, sustainable, renewable energy source that has a much smaller impact on the environment than burning fossil fuels. Historically ...
, and geothermal power, and increasingly play an important role for the
electric power distribution Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmissi ...
system. A grid-connected device for
electricity storage Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an Accumulator (energy), accumulator or Batte ...
can also be classified as a DER system and is often called a distributed energy storage system (DESS). By means of an interface, DER systems can be managed and coordinated within a smart grid. Distributed generation and storage enables the collection of energy from many sources and may lower environmental impacts and improve the security of supply. One of the major issues with the integration of the DER such as solar power, wind power, etc. is the uncertain nature of such electricity resources. This uncertainty can cause a few problems in the distribution system: (i) it makes the supply-demand relationships extremely complex, and requires complicated optimization tools to balance the network, and (ii) it puts higher pressure on the transmission network, and (iii) it may cause reverse power flow from the distribution system to transmission system.
Microgrid A microgrid is a local electrical grid with defined electrical boundaries, acting as a single and controllable entity. It is able to operate in grid-connected and in island mode.
s are modern, localized, small-scale grids, contrary to the traditional, centralized
electricity grid An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
(macrogrid). Microgrids can disconnect from the centralized grid and operate autonomously, strengthen grid resilience, and help mitigate grid disturbances. They are typically low-voltage AC grids, often use
diesel generator A diesel generator (DG) (also known as a diesel Genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression-ig ...
s, and are installed by the community they serve. Microgrids increasingly employ a mixture of different distributed energy resources, such as
solar hybrid power systems Hybrid power are combinations between different technologies to produce power. In power engineering, the term 'hybrid' describes a combined power and energy storage system. Examples of power producers used in hybrid power are photovoltaics, ...
, which significantly reduce the amount of carbon emitted.


Overview

Historically, central plants have been an integral part of the electric grid, in which large generating facilities are specifically located either close to resources or otherwise located far from populated load centers. These, in turn, supply the traditional transmission and distribution (T&D) grid that distributes bulk power to load centers and from there to consumers. These were developed when the costs of transporting fuel and integrating generating technologies into populated areas far exceeded the cost of developing T&D facilities and tariffs. Central plants are usually designed to take advantage of available economies of scale in a site-specific manner, and are built as "one-off," custom projects. These
economies of scale In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...
began to fail in the late 1960s and, by the start of the 21st century, Central Plants could arguably no longer deliver competitively cheap and reliable electricity to more remote customers through the grid, because the plants had come to cost less than the grid and had become so reliable that nearly all power failures originated in the grid. Thus, the grid had become the main driver of remote customers’ power costs and power quality problems, which became more acute as digital equipment required extremely reliable electricity.DOE; The Potential Benefits of Distributed Generation and Rate-Related Issues that May Impede Their Expansion; 2007. Efficiency gains no longer come from increasing generating capacity, but from smaller units located closer to sites of demand. For example, coal power plants are built away from cities to prevent their heavy air pollution from affecting the populace. In addition, such plants are often built near
collieries Coal mining is the process of resource extraction, extracting coal from the ground. Coal is valued for its Energy value of coal, energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use c ...
to minimize the cost of transporting coal. Hydroelectric plants are by their nature limited to operating at sites with sufficient water flow. Low pollution is a crucial advantage of combined cycle plants that burn
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
. The low pollution permits the plants to be near enough to a city to provide
district heating District heating (also known as heat networks or teleheating) 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 a ...
and cooling. Distributed energy resources are mass-produced, small, and less site-specific. Their development arose out of: # concerns over perceived externalized costs of central plant generation, particularly environmental concerns; # the increasing age, deterioration, and capacity constraints upon T&D for bulk power; # the increasing relative economy of mass production of smaller appliances over heavy manufacturing of larger units and on-site construction; # Along with higher relative prices for energy, higher overall complexity and total costs for regulatory oversight, tariff administration, and metering and billing. Capital markets have come to realize that right-sized resources, for individual customers, distribution substations, or microgrids, are able to offer important but little-known economic advantages over central plants. Smaller units offered greater economies from mass-production than big ones could gain through unit size. These increased value—due to improvements in financial risk, engineering flexibility, security, and environmental quality—of these resources can often more than offset their apparent cost disadvantages. Distributed generation (DG), vis-à-vis central plants, must be justified on a life-cycle basis. Unfortunately, many of the direct, and virtually all of the indirect, benefits of DG are not captured within traditional utility
cash-flow A cash flow is a real or virtual movement of money: *a cash flow in its narrow sense is a payment (in a currency), especially from one central bank account to another; the term 'cash flow' is mostly used to describe payments that are expected ...
accounting. While the levelized cost of DG is typically more expensive than conventional, centralized sources on a kilowatt-hour basis, this does not consider negative aspects of conventional fuels. The additional premium for DG is rapidly declining as demand increases and technology progresses, and sufficient and reliable demand may bring economies of scale, innovation, competition, and more flexible financing, that could make DG clean energy part of a more diversified future. DG reduces the amount of energy lost in transmitting electricity because the electricity is generated very near where it is used, perhaps even in the same building. This also reduces the size and number of power lines that must be constructed. Typical DER systems in a
feed-in tariff A feed-in tariff (FIT, FiT, standard offer contract,Couture, T., Cory, K., Kreycik, C., Williams, E., (2010)Policymaker's Guide to Feed-in Tariff Policy Design National Renewable Energy Laboratory, U.S. Dept. of Energy advanced renewable tariff, ...
(FIT) scheme have low maintenance, low pollution and high efficiencies. In the past, these traits required dedicated operating engineers and large complex plants to reduce pollution. However, modern
embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...
s can provide these traits with automated operation and renewable energy, such as solar,
wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...
and geothermal. This reduces the size of power plant that can show a profit.


Grid parity

Grid parity Grid parity (or socket parity) occurs when an alternative energy source can generate power at a levelized cost of electricity (LCOE) that is less than or equal to the price of power from the electricity grid. The term is most commonly used wh ...
occurs when an alternative energy source can generate electricity at a levelized cost (
LCOE The levelized cost of electricity (LCOE), or levelized cost of energy, is a measure of the average net present cost of electricity generation for a generator over its lifetime. It is used for investment planning and to compare different methods ...
) that is less than or equal to the end consumer's retail price. Reaching grid parity is considered to be the point at which an energy source becomes a contender for widespread development without
subsidies A subsidy or government incentive is a form of financial aid or support extended to an economic sector (business, or individual) generally with the aim of promoting economic and social policy. Although commonly extended from the government, the ter ...
or government support. Since the 2010s, grid parity for solar and wind has become a reality in a growing number of markets, including Australia, several European countries, and some states in the U.S.


Technologies

Distributed energy resource (DER) systems are small-scale power generation or storage technologies (typically in the range of 1 kW to 10,000 kW) used to provide an alternative to or an enhancement of the traditional electric power system. DER systems typically are characterized by high initial
capital costs Capital costs are fixed, one-time expenses incurred on the purchase of land, buildings, construction, and equipment used in the production of goods or in the rendering of services. In other words, it is the total cost needed to bring a project to a ...
per kilowatt. DER systems also serve as storage device and are often called ''Distributed energy storage systems'' (DESS). DER systems may include the following devices/technologies: *
Combined heat 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 ...
(CHP), also known as ''cogeneration'' or ''trigeneration'' * Fuel cells * Hybrid power systems ( solar hybrid and wind hybrid systems) *
Micro combined heat and power 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 ...
(MicroCHP) * Microturbines * Photovoltaic systems (typically
rooftop solar PV A rooftop solar power system, or rooftop PV system, is a photovoltaic system, photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various compon ...
) *
Reciprocating engines A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
* Small wind power systems *
Stirling engine A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas (the ''working fluid'') between different temperatures, resulting in a net conversion of heat energy to mechanical work. More specif ...
s * or a combination of the above. For example, hybrid photovoltaic, CHP and
battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...
systems can provide full electric power for single family residences without extreme storage expenses.


Cogeneration

Distributed
cogeneration 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 elec ...
sources use steam turbines, natural gas-fired fuel cells,
microturbine A microturbine (MT) is a small Gas Turbine with similar cycles and components to a heavy gas turbine. The MT power-to-weight ratio is better than a heavy gas turbine because the reduction of turbine diameters causes an increase in shaft rotational ...
s or
reciprocating engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common fea ...
s to turn generators. The hot exhaust is then used for space or water heating, or to drive an absorptive chiller for cooling such as air-conditioning. In addition to natural gas-based schemes, distributed energy projects can also include other renewable or low carbon fuels including biofuels,
biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
,
landfill gas Landfill gas is a mix of different gases created by the action of microorganisms within a landfill as they decompose organic waste, including for example, food waste and paper waste. Landfill gas is approximately forty to sixty percent methane ...
, sewage gas,
coal bed methane Coalbed methane (CBM or coal-bed methane), coalbed gas, coal seam gas (CSG), or coal-mine methane (CMM) is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy in United States, Canada, Au ...
, syngas and
associated petroleum gas Associated petroleum gas (APG), or associated gas, is a form of natural gas which is found with deposits of petroleum, either dissolved in the oil or as a free "gas cap" above the oil in the reservoir. The gas can be utilized in a number of ways ...
. Delta-ee consultants stated in 2013 that with 64% of global sales, the fuel cell
micro combined heat and power 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 ...
passed the conventional systems in sales in 2012. 20.000 units were sold in Japan in 2012 overall within the Ene Farm project. With a Lifetime of around 60,000 hours for PEM fuel cell units, which shut down at night, this equates to an estimated lifetime of between ten and fifteen years. For a price of $22,600 before installation. For 2013 a state subsidy for 50,000 units is in place. In addition,
molten carbonate fuel cell Molten-carbonate fuel cells (MCFCs) are high-temperature fuel cells that operate at temperatures of 600 °C and above. Molten carbonate fuel cells (MCFCs) were developed for natural gas, biogas (produced as a result of anaerobic digestion or ...
and
solid oxide fuel cell A solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte. A ...
s using natural gas, such as the ones from
FuelCell Energy FuelCell Energy, Inc. is a publicly traded fuel cell company, headquartered in Danbury, Connecticut. It designs, manufactures, operates and services Direct Fuel Cell power plants (a type of molten carbonate fuel cell). As one of the biggest ...
and the
Bloom energy server The Bloom Energy Server or Bloom Box is a solid oxide fuel cell (SOFC) power generator made by Bloom Energy, of Sunnyvale, California, that takes a variety of input fuels, including liquid or gaseous hydrocarbons produced from biological source ...
, or waste-to-energy processes such as the Gate 5 Energy System are used as a distributed energy resource.


Solar power

Photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...
, by far the most important solar technology for distributed generation of
solar power Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovolta ...
, uses
solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
s assembled into solar panels to convert sunlight into electricity. It is a fast-growing technology doubling its worldwide installed capacity every couple of years.
PV system PV may refer to: Places * Paceville, Malta * Puerto Vallarta, Mexico * Postal village, a settlement that has a post office United States * Palos Verdes Peninsula, California * Prescott Valley, Arizona * Prairie Village, Kansas Politics * P ...
s range from distributed, residential, and commercial
rooftop A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temper ...
or building integrated installations, to large, centralized utility-scale photovoltaic power stations. The predominant PV technology is
crystalline silicon Crystalline silicon or (c-Si) Is the crystalline forms of silicon, either polycrystalline silicon (poly-Si, consisting of small crystals), or monocrystalline silicon (mono-Si, a continuous crystal). Crystalline silicon is the dominant semiconduc ...
, while
thin-film solar cell A thin-film solar cell is a second generation solar cell that is made by depositing one or more thin layers, or thin film (TF) of photovoltaic material on a substrate, such as glass, plastic or metal. Thin-film solar cells are commercially use ...
technology accounts for about 10 percent of global photovoltaic deployment. In recent years, PV technology has improved its sunlight to electricity
conversion efficiency Energy conversion efficiency (''η'') is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radi ...
, reduced the installation cost per watt as well as its energy payback time (EPBT) and
levelised cost of electricity The levelized cost of electricity (LCOE), or levelized cost of energy, is a measure of the average net present cost of electricity generation for a generator over its lifetime. It is used for investment planning and to compare different methods ...
(LCOE), and has reached
grid parity Grid parity (or socket parity) occurs when an alternative energy source can generate power at a levelized cost of electricity (LCOE) that is less than or equal to the price of power from the electricity grid. The term is most commonly used wh ...
in at least 19 different markets in 2014. As most renewable energy sources and unlike coal and nuclear, solar PV is variable and non- dispatchable, but has no fuel costs, operating pollution, as well as greatly reduced mining-safety and operating-safety issues. It produces peak power around local noon each day and its
capacity factor The net capacity factor is the unitless ratio of actual electrical energy output over a given period of time to the theoretical maximum electrical energy output over that period. The theoretical maximum energy output of a given installation is def ...
is around 20 percent.


Wind power

Wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each yea ...
s can be distributed energy resources or they can be built at utility scale. These have low maintenance and low pollution, but distributed wind unlike utility-scale wind has much higher costs than other sources of energy. As with solar, wind energy is variable and non-dispatchable. Wind towers and generators have substantial insurable liabilities caused by high winds, but good operating safety. Distributed generation from
wind hybrid power systems Hybrid power are combinations between different technologies to produce power. In power engineering, the term 'hybrid' describes a combined power and energy storage system. Examples of power producers used in hybrid power are photovoltaics, ...
combines wind power with other DER systems. One such example is the integration of wind turbines into
solar hybrid power systems Hybrid power are combinations between different technologies to produce power. In power engineering, the term 'hybrid' describes a combined power and energy storage system. Examples of power producers used in hybrid power are photovoltaics, ...
, as wind tends to complement solar because the peak operating times for each system occur at different times of the day and year.


Hydro power

Hydroelectricity is the most widely used form of renewable energy and its potential has already been explored to a large extent or is compromised due to issues such as environmental impacts on fisheries, and increased demand for recreational access. However, using modern 21st century technology, such as
wave power Wave power is the capture of energy of wind waves to do useful work – for example, electricity generation, water desalination, or pumping water. A machine that exploits wave power is a wave energy converter (WEC). Waves are generated by win ...
, can make large amounts of new hydropower capacity available, with minor environmental impact. Modular and scalable ''Next generation kinetic energy turbines'' can be deployed in arrays to serve the needs on a residential, commercial, industrial, municipal or even regional scale. ''Microhydro kinetic generators'' neither require dams nor impoundments, as they utilize the kinetic energy of water motion, either waves or flow. No construction is needed on the shoreline or sea bed, which minimizes environmental impacts to habitats and simplifies the permitting process. Such power generation also has minimal environmental impact and non-traditional microhydro applications can be tethered to existing construction such as docks, piers, bridge abutments, or similar structures.


Waste-to-energy

Municipal solid waste (MSW) and natural waste, such as sewage sludge,
food waste Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...
and animal manure will decompose and discharge methane-containing gas that can be collected and used as fuel in gas turbines or micro turbines to produce electricity as a distributed energy resource. Additionally, a California-based company, Gate 5 Energy Partners, Inc. has developed a process that transforms natural waste materials, such as sewage sludge, into biofuel that can be combusted to power a steam turbine that produces power. This power can be used in lieu of grid-power at the waste source (such as a treatment plant, farm or dairy).


Energy storage

A distributed energy resource is not limited to the generation of electricity but may also include a device to store distributed energy (DE).http://www.smartgrid.go
Lexicon Distributed Energy Resource
Distributed energy storage systems (DESS) applications include several types of battery,
pumped hydro Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...
, compressed air, and
thermal energy storage Thermal energy storage (TES) is achieved with widely different technologies. Depending on the specific technology, it allows excess thermal energy to be stored and used hours, days, months later, at scales ranging from the individual process, ...
. Access to energy storage for commercial applications is easily accessible through programs such as energy storage as a service (ESaaS).


PV storage

: Common rechargeable battery technologies used in today's PV systems include, the
valve regulated lead-acid battery A valve regulated lead–acid (VRLA) battery, commonly known as a sealed lead–acid (SLA) battery, is a type of lead–acid battery characterized by a limited amount of electrolyte ("starved" electrolyte) absorbed in a plate separator or formed ...
(
lead–acid battery The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, lead–acid batteries have ...
), nickel–cadmium and lithium-ion batteries. Compared to the other types, lead-acid batteries have a shorter lifetime and lower energy density. However, due to their high reliability, low
self-discharge Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes or any external circuit. Self-discharge decreases the shelf life Shelf life ...
(4–6% per year) as well as low investment and maintenance costs, they are currently the predominant technology used in small-scale, residential PV systems, as lithium-ion batteries are still being developed and about 3.5 times as expensive as lead-acid batteries. Furthermore, as storage devices for PV systems are stationary, the lower energy and power density and therefore higher weight of lead-acid batteries are not as critical as for electric vehicles. : However, lithium-ion batteries, such as the
Tesla Powerwall The Tesla Powerwall is a rechargeable lithium-ion battery stationary home energy storage product manufactured by Tesla Energy. The Powerwall stores electricity for solar self-consumption, time of use load shifting, and backup power. The Power ...
, have the potential to replace lead-acid batteries in the near future, as they are being intensively developed and lower prices are expected due to economies of scale provided by large production facilities such as the
Gigafactory 1 Gigafactory Nevada (also known as Giga Nevada or Gigafactory 1) is a lithium-ion battery and electric vehicle component factory in Storey County, Nevada, US. The facility, located east of Reno, is owned and operated by Tesla, Inc., and suppl ...
. In addition, the Li-ion batteries of plug-in electric cars may serve as future storage devices, since most vehicles are parked an average of 95 percent of the time, their batteries could be used to let electricity flow from the car to the power lines and back. Other rechargeable batteries that are considered for distributed PV systems include, sodium–sulfur and vanadium redox batteries, two prominent types of a
molten salt Molten salt is salt which is solid at standard temperature and pressure but enters the liquid phase due to elevated temperature. Regular table salt has a melting point of 801 °C (1474°F) and a heat of fusion of 520 J/g.Journal of Chemical T ...
and a flow battery, respectively.


Vehicle-to-grid

: Future generations of electric vehicles may have the ability to deliver power from the battery in a
vehicle-to-grid Vehicle-to-grid (V2G), also known as Vehicle-to-home (V2H) or Vehicle-to-load (V2L) describes a system in which plug-in electric vehicles (PEV) sell demand response services to the grid. Demand services are either delivering electricity or by red ...
into the grid when needed. An
electric vehicle network An electric vehicle charging network is an infrastructure system of charging stations to recharge electric vehicles. Many government, car manufacturers, and charging infrastructure providers sought to create networks. the largest fast-chargi ...
has the potential to serve as a DESS.http://www.NREL.go
- The Role of Energy Storage with Renewable Electricity Generation
/ref>


Flywheels

: An advanced
flywheel energy storage Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. When energy is extracted from the system, the flywheel's rotational speed is reduced as a c ...
(FES) stores the electricity generated from distributed resources in the form of angular
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acc ...
by accelerating a rotor (
flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...
) to a very high speed of about 20,000 to over 50,000 rpm in a vacuum enclosure. Flywheels can respond quickly as they store and feed back electricity into the grid in a matter of seconds.


Integration with the grid

For reasons of reliability, distributed generation resources would be interconnected to the same transmission grid as central stations. Various technical and economic issues occur in the integration of these resources into a grid. Technical problems arise in the areas of power quality, voltage stability, harmonics, reliability, protection, and control. Behavior of protective devices on the grid must be examined for all combinations of distributed and central station generation. A large scale deployment of distributed generation may affect grid-wide functions such as frequency control and allocation of reserves. As a result, smart grid functions,
virtual power plant A virtual power plant (VPP) is a Cloud computing, cloud-based distributed power plant that aggregates the capacities of heterogeneous distributed energy resources (DER) for the purposes of enhancing power generation, trading or selling power on the ...
s and grid energy storage such as
power to gas Power-to-gas (often abbreviated P2G) is a technology that uses electric power to produce a gaseous fuel. When using surplus power from wind generation, the concept is sometimes called windgas. Most P2G systems use electrolysis to produce hydrogen ...
stations are added to the grid. Conflicts occur between utilities and resource managing organizations. Each distributed generation resource has its own integration issues. Solar PV and wind power both have intermittent and unpredictable generation, so they create many stability issues for voltage and frequency. These voltage issues affect mechanical grid equipment, such as load tap changers, which respond too often and wear out much more quickly than utilities anticipated. Also, without any form of energy storage during times of high solar generation, companies must rapidly increase generation around the time of sunset to compensate for the loss of solar generation. This high ramp rate produces what the industry terms the ''
duck curve The duck curve is a graph of power production over the course of a day that shows the timing imbalance between peak demand and renewable energy production. Used in utility-scale electricity generation, the term was coined in 2012 by the Cali ...
'' that is a major concern for grid operators in the future. Storage can fix these issues if it can be implemented. Flywheels have shown to provide excellent frequency regulation. Also, flywheels are highly cyclable compared to batteries, meaning they maintain the same energy and power after a significant amount of cycles( on the order of 10,000 cycles). Short term use batteries, at a large enough scale of use, can help to flatten the duck curve and prevent generator use fluctuation and can help to maintain voltage profile. However, cost is a major limiting factor for energy storage as each technique is prohibitively expensive to produce at scale and comparatively not energy dense compared to liquid fossil fuels. Finally, another necessary method of aiding in integration of photovoltaics for proper distributed generation is in the use of
intelligent hybrid inverter A solar inverter or photovoltaic (PV) inverter is a type of power inverter which converts the variable direct current (DC) output of a photovoltaic solar panel into a utility frequency alternating current (AC) that can be fed into a commercial ...
s. Intelligent hybrid inverters store energy when there is more energy production than consumption. When consumption is high, these inverters provide power relieving the distribution system. Another approach does not demand grid integration: stand alone hybrid systems.


Mitigating Voltage and Frequency Issues of DG integration

There have been some efforts to mitigate voltage and frequency issues due to increased implementation of DG. Most notably, IEEE 1547 sets the standard for interconnection and interoperability of distributed energy resources. IEEE 1547 sets specific curves signaling when to clear a fault as a function of the time after the disturbance and the magnitude of the voltage irregularity or frequency irregularity. Voltage issues also give legacy equipment the opportunity to perform new operations. Notably, inverters can regulate the voltage output of DGs. Changing inverter impedances can change voltage fluctuations of DG, meaning inverters have the ability to control DG voltage output. To reduce the effect of DG integration on mechanical grid equipment, transformers and load tap changers have the potential to implement specific tap operation vs. voltage operation curves mitigating the effect of voltage irregularities due to DG. That is, load tap changers respond to voltage fluctuations that last for a longer period than voltage fluctuations created from DG equipment.


Stand alone hybrid systems

It is now possible to combine technologies such as
photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...
, batteries and cogen to make stand alone distributed generation systems. Recent work has shown that such systems have a low
levelized cost of electricity The levelized cost of electricity (LCOE), or levelized cost of energy, is a measure of the average net present cost of electricity generation for a generator over its lifetime. It is used for investment planning and to compare different methods ...
. Many authors now think that these technologies may enable a mass-scale
grid defection An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
because consumers can produce electricity using
off grid Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical g ...
systems primarily made up of
solar photovoltaic A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and c ...
technology. For example, the Rocky Mountain Institute has proposed that there may wide scale
grid defection An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
. This is backed up by studies in the Midwest.


Cost factors

Cogenerators are also more expensive per watt than central generators. They find favor because most buildings already burn fuels, and the cogeneration can extract more value from the fuel . Local production has no electricity transmission losses on long distance
power line An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...
s or energy losses from the
Joule effect Joule effect and Joule's law are any of several different physical effects discovered or characterized by English physicist James Prescott Joule. These physical effects are not the same, but all are frequently or occasionally referred to in the lit ...
in transformers where in general 8-15% of the energy is lost (see also
cost of electricity by source Different methods of electricity generation can incur a variety of different costs, which can be divided into three general categories: 1) wholesale costs, or all costs paid by utilities associated with acquiring and distributing electricity to ...
). Some larger installations utilize combined cycle generation. Usually this consists of a
gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
whose exhaust boils
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
for a steam turbine in a
Rankine cycle The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...
. The condenser of the steam cycle provides the heat for space heating or an absorptive
chiller A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another p ...
. Combined cycle plants with cogeneration have the highest known thermal efficiencies, often exceeding 85%. In countries with high pressure gas distribution, small turbines can be used to bring the gas pressure to domestic levels whilst extracting useful energy. If the UK were to implement this countrywide an additional 2-4 GWe would become available. (Note that the energy is already being generated elsewhere to provide the high initial gas pressure - this method simply distributes the energy via a different route.)


Microgrid

A ''microgrid'' is a localized grouping of electricity generation, energy storage, and loads that normally operates connected to a traditional centralized grid ( macrogrid). This single point of common coupling with the macrogrid can be disconnected. The microgrid can then function autonomously. Generation and loads in a microgrid are usually interconnected at low voltage and it can operate in DC, AC, or the combination of both. From the point of view of the grid operator, a connected microgrid can be controlled as if it were one entity. Microgrid generation resources can include stationary batteries, fuel cells, solar, wind, or other energy sources. The multiple dispersed generation sources and ability to isolate the microgrid from a larger network would provide highly reliable electric power. Produced heat from generation sources such as microturbines could be used for local process heating or space heating, allowing flexible trade off between the needs for heat and electric power. Micro-grids were proposed in the wake of the
July 2012 India blackout Two severe power blackouts affected most of northern and eastern India on 30 and 31 July 2012. The 30 July 2012 blackout affected over 400 million people and was briefly the largest power outage in history by number of people affected, beating ...
: * Small micro-grids covering 30–50 km radius * Small power stations of 5–10 MW to serve the micro-grids * Generate power locally to reduce dependence on long distance transmission lines and cut transmission losses. Micro-grids have seen implementation in a number of communities over the world. For example, Tesla has implemented a solar micro-grid in the Samoan island of Ta'u, powering the entire island with solar energy. This localized production system has helped save over of diesel fuel. It is also able to sustain the island for three whole days if the sun were not to shine at all during that period. This is a great example of how micro-grid systems can be implemented in communities to encourage renewable resource usage and localized production. To plan and install Microgrids correctly, engineering modelling is needed. Multiple simulation tools and optimization tools exist to model the economic and electric effects of Microgrids. A widely used economic optimization tool is the Distributed Energy Resources Customer Adoption Model (DER-CAM) from Lawrence Berkeley National Laboratory. Another frequently used commercial economic modelling tool i
Homer Energy
originally designed by the National Renewable Laboratory. There are also some power flow and electrical design tools guiding the Microgrid developers. The Pacific Northwest National Laboratory designed the public available GridLAB-D tool and the Electric Power Research Institute (EPRI) designed OpenDSS to simulate the distribution system (for Microgrids). A professional integrated DER-CAM and OpenDSS version is available vi
BankableEnergy
A European tool that can be used for electrical, cooling, heating, and process heat demand simulation is EnergyPLAN from the Aalborg University, Denmark.


Communication in DER systems

*
IEC 61850 IEC 61850 is an international standard defining communication protocols for intelligent electronic devices at electrical substations. It is a part of the International Electrotechnical Commission's (IEC) Technical Committee 57 reference archit ...
-7-420 is published by IEC TC 57: Power systems management and associated information exchange. It is one of the IEC 61850 standards, some of which are core Standards required for implementing smart grids. It uses communication services mapped to
MMS MMS may refer to: Science and technology Network communication protocols * Multimedia Messaging Service for mobile phones * Microsoft Media Server, a content-streaming protocol (mms://) * Manufacturing Message Specification for real time proces ...
as per IEC 61850-8-1 standard. * OPC is also used for the communication between different entities of DER system. * Institute of Electrical and Electronics Engineers IEEE 2030.7 microgrid controller standard. That concept relies on 4 blocks: a) Device Level control (e.g. Voltage and Frequency Control), b) Local Area Control (e.g. data communication), c) Supervisory (software) controller (e.g. forward looking dispatch optimization of generation and load resources), and d) Grid Layer (e.g. communication with utility). *A wide variety of complex control algorithms exist, making it difficult for small and residential Distributed Energy Resource (DER) users to implement energy management and control systems. Especially, communication upgrades and data information systems can make it expensive. Thus, some projects try to simplify the control of DER via off-the shelf products and make it usable for the mainstream (e.g. using a Raspberry Pi).


Legal requirements for distributed generation

In 2010 Colorado enacted a law requiring that by 2020 that 3% of the power generated in Colorado utilize distributed generation of some sort. On 11 October 2017, California Governor Jerry Brown signed into law a bill, SB 338, that makes utility companies plan "carbon-free alternatives to gas generation" in order to meet peak demand. The law requires utilities to evaluate issues such as energy storage, efficiency, and distributed energy resources.


See also

*
Autonomous building An autonomous building is a building designed to be operated independently from infrastructural support services such as the electric power grid, gas grid, municipal water systems, sewage treatment systems, storm drains, communication services, ...
* Demand response *
Energy harvesting Energy harvesting (EH, also known as power harvesting or energy scavenging or ambient power) is the process by which energy is derived from external sources (e.g., solar power, thermal energy, wind energy, salinity gradients, and kinetic ener ...
* Energy storage as a service (ESaaS) *
Electranet Electranet is a proposed smart electric grid which would allow people to sell electricity into the grid without any artificial caps. It was proposed in an op-ed article Al Gore wrote in a "My Turn" column for ''Newsweek'' in 2006. Like the inter ...
* Electric power transmission *
Electricity generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its s ...
*
Electricity market In a broad sense, an electricity market is a system that facilitates the exchange of electricity-related goods and services. During more than a century of evolution of the electric power industry, the economics of the electricity markets had un ...
*
Electricity retailing Electricity retailing is the final sale of electricity from generation to the end-use consumer. This is the fourth major step in the electricity delivery process, which also includes generation, transmission and distribution. Beginnings Electric ...
*
Energy demand management Energy demand management, also known as demand-side management (DSM) or demand-side response (DSR), is the modification of consumer demand for energy through various methods such as financial incentives and behavioral change through education. Us ...
*
Energy efficiency Energy efficiency may refer to: * Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process ** Electrical efficiency, useful power output per electrical power consumed ** Mechanical efficiency, a ra ...
* Energy storage *
Flywheel energy storage Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. When energy is extracted from the system, the flywheel's rotational speed is reduced as a c ...
*
Future energy development Energy development is the field of activities focused on obtaining sources of energy from natural resources. These activities include production of renewable, nuclear, and fossil fuel derived sources of energy, and for the recovery and reuse ...
*
Green power superhighway A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curren ...
*
Grid-tied electrical system A grid-tied electrical system, also called ''tied to grid'' or ''grid tie system'', is a semi-autonomous electrical generation or grid energy storage system which links to the mains to feed excess capacity back to the local mains electrical grid. ...
*
Hydrogen station A hydrogen station is a storage or filling station for Hydrogen. The hydrogen is dispensed by weight. There are two filling pressures in common use. H70 or 700 bar, and the older standard H35 or 350 bar. As of 2021 around 550 filling stations were ...
*
IEEE 1547 IEEE 1547 (''Standard for Interconnecting Distributed Resources with Electric Power Systems'') is a standard of the Institute of Electrical and Electronics Engineers meant to provide a set of criteria and requirements for the interconnection of dis ...
(''Standard for Interconnecting Distributed
Resources with Electric Power Systems)'' *
Islanding Islanding is the condition in which a distributed generator (DG) continues to power a location even though external electrical grid power is no longer present. Islanding can be dangerous to utility workers, who may not realize that a circuit is st ...
* Local flexibility markets *
Microgeneration Microgeneration is the small-scale production of heat or electric power from a "low carbon source," as an alternative or supplement to traditional centralized grid-connected power. Microgeneration technologies include small-scale wind turbin ...
* Net metering *
Peak shaving Load management, also known as demand-side management (DSM), is the process of balancing the supply of electricity on the network with the electrical load by adjusting or controlling the load rather than the power station output. This can be ach ...
*
Relative cost of electricity generated by different sources Different methods of electricity generation can incur a variety of different costs, which can be divided into three general categories: 1) wholesale costs, or all costs paid by utilities associated with acquiring and distributing electricity to ...
* Renewable energy development * Smart meter *
Smart power grid A smart grid is an electrical grid which includes a variety of operation and energy measures including: *Advanced metering infrastructure (of which smart meters are a generic name for any utility side device even if it is more capable e.g. a f ...
* Solar Guerrilla * Stand-alone power system *
Sustainable community energy system A sustainable community energy system is an integrated approach to supplying a local community with its energy requirements from renewable energy or high-efficiency co-generation energy sources. The approach can be seen as a development of the dist ...
*
Trigeneration 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 ...
*
World Alliance for Decentralized Energy The World Alliance for Decentralized Energy (WADE) was founded in 1997 with the original name of the ''International Cogeneration Alliance''. It was originally formed in response to the UNFCCC meetings in Kyoto to raise the profile of cogeneration o ...


References


Further reading

* * Gies, Erica
Making the Consumer an Active Participant in the Grid
''
The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid d ...
'', 29 November 2010. Discusses distributed generation and the U.S. Federal Energy Regulatory Commission. *


External links


MIGRIDS -Worldwide Business and Marketing Microgrid Directory

The UK District Energy Association - advocating the construction of locally distributed energy networks




* ttp://www.localpower.org World Alliance for Decentralized Energy
The iDEaS project by University of Southampton on Decentralised Energy



Microgrids projects and DER Optimization Model at Berkeley Lab

DERlab

Center for Energy and innovative Technologies

Decentralized Power System (DPS) in Pakistan



What are distributed energy resources (DER) and how do they work?
Australian Renewable Energy Agency The Australian Renewable Energy Agency (ARENA) is an independent agency of the Australian federal government, established in 2012 to manage Australia's renewable energy programs, with the objective of increasing supply and competitiveness of A ...
(
ARENA An arena is a large enclosed platform, often circular or oval-shaped, designed to showcase theatre, musical performances, or sporting events. It is composed of a large open space surrounded on most or all sides by tiered seating for spectators ...
). {{DEFAULTSORT:Distributed Generation Power station technology Electric power generation Renewable energy