MicroCHP
Encyclopedia
Micro combined heat and power or micro-CHP is an extension of the now well established idea of cogeneration
to the single/multi family home or small office building.
, mechanical energy
and electric power
. Often, these additional forms of energy are produced by a heat engine
, running on a source of high-temperature heat. A heat engine can never have perfect efficiency, according to the second law of thermodynamics
, therefore a heat engine will always produce a surplus of low-temperature heat. This is commonly referred to as waste heat
or "secondary heat", or "low-grade heat". This heat is useful for the majority of heating applications, however, it is sometimes not practical to transport heat energy over long distances, unlike electricity
or fuel
energy. By transporting fuel, however, the "waste heat" is essentially being transported along with the fuel, before the waste heat is actually produced.
To make efficient use of energy, the "waste heat" must be used purposefully. Since it is practical to transport electricity, but not always practical to transport waste heat, an energy efficient system must generate electricity near locations where the waste heat can be put to good use. This is known as a combined heat and power
(CHP
) system, or "cogeneration
".
In a central power plant, the supply of "waste heat" may exceed the local heat demand. In such cases, if it is not desirable to reduce the power production, the excess waste heat must be disposed in e.g. cooling tower
s or sea cooling without being used. A way to avoid excess waste heat is to reduce the fuel input to the CHP plant, reducing both the heat and power output to balance the heat demand. In doing this, the power production is limited by the heat demand.
CHP systems are able to increase the total energy utilization of primary energy sources, such as fuel and concentrated solar thermal energy. Thus CHP has been steadily gaining popularity in all sectors of the energy economy, due to the increased costs of fuels, particularly oil-based fuels, and due to environmental concerns, particularly climate change
.
In a traditional power plant delivering electricity to consumers, about 30% of the heat content of the primary heat energy source, such as biomass
, coal
, solar thermal, natural gas
, petroleum
or uranium
, reaches the consumer, although the efficiency can be 20% for very old plants and 45% for newer gas plants. In contrast, a CHP system converts 15%–42% of the primary heat to electricity, and most of the remaining heat is captured for hot water
or space heating
. In total, as much as 90% of the heat from the primary energy source goes to useful purposes when heat production does not exceed the demand.
CHP systems have benefited the industrial sector since the beginning of the industrial revolution. For three decades, these larger CHP systems were more economically justifiable than micro-CHP, due to the economy of scale. After the year 2000, micro-CHP has become cost effective in many markets around the world, due to rising energy costs. The development of micro-CHP systems has also been facilitated by recent technological developments of small heat engines. This includes improved performance and/or cost-effectiveness of fuel cell
s, Stirling engine
s, steam engines, gas turbines, diesel engine
s and Otto engine
s.
and heat is a by-product; micro-CHP systems in homes or small commercial buildings are controlled by heat-demand, delivering electricity
as the by-product. When used primarily for heat in circumstances of fluctuating electrical demand, micro-CHP systems will often generate more electricity than is instantly being demanded.
To date, micro-CHP systems achieve much of their savings, and thus attractiveness to consumers, through a "generate-and-resell" or net metering
model wherein home-generated power exceeding the instantaneous in-home needs is sold back to the electrical utility. This system is efficient because the energy used is distributed and used instantaneously over the electrical grid. The main losses are in the transmission from the source to the consumer which will typically be less than losses incurred by storing energy locally or generating power at less than the peak efficiency of the micro-CHP system. So, from a purely technical standpoint dynamic demand management
and net-metering are very efficient.
Another positive to net-metering is the fact that it is fairly easy to configure. The user's electrical meter is simply able to record electrical power exiting as well as entering the home or business. As such, it records the net amount of power entering the home. For a grid with relatively few micro-CHP users, no design changes to the electrical grid need be made. Additionally, in the United States
, federal and now many state regulations require utility operators to compensate anyone adding power to the grid. From the standpoint of grid operator, these points present operational and technical as well as administrative burdens. As a consequence, most grid operators compensate non-utility
power-contributors at less than or equal to the rate they charge their customers. While this compensation scheme may seem almost fair at first glance, it only represents the consumer’s cost-savings of not purchasing utility power versus the true cost of generation and operation to the micro-CHP operator. Thus from the standpoint of micro-CHP operators, net-metering is not ideal.
While net-metering is a very efficient mechanism for using excess energy generated by a micro-CHP system, it is not without its detractors. Of the detractors' main points, the first to consider is that while the main generating source on the electrical grid is a large commercial generator, net-metering generators "spill" power to the smart grid in a haphazard and unpredictable fashion. However, the effect is negligible if there are only a small percentage of customers generating electricity and each of them generates a relatively small amount of electricity. When turning on an oven or space heater, about the same amount of electricity is drawn from the grid as a home generator puts out. If the percentage of homes with generating systems becomes large, then the effect on the grid may become significant. Coordination among the generating systems in homes and the rest of the grid may be necessary for reliable operation and to prevent damage to the grid.
In an evaluation from 2008 by Claverton Energy Group, Stirling engined micro CHP was deemed the most cost effective of the various microgeneration technologies in abating carbon in the UK.
s, such as Otto engine
and gas turbine
systems. Gas turbines are used in many small systems due to their high efficiency, small size, clean combustion, durability and low maintenance requirements. Gas turbines designed with foil bearing
s and air-cooling, operate without lubricating oil or coolants. The waste heat of gas turbines is mostly in the exhaust, whereas the waste heat of reciprocating internal combustion engine
s, is split between the exhaust and cooling system.
The future of combined heat and power, particularly for homes and small businesses, will continue to be affected by the price of fuel, including natural gas. As fuel prices continue to climb, this will make the economics more favorable for energy conservation measures, and more efficient energy use
, including CHP and micro-CHP.
, LPG, vegetable oil (such as rapeseed
oil), woodgas, solar thermal
, and natural gas
, as well as multi-fuel systems. (Nuclear power is hazardous at small scales, due to radiation risks, so it is generally not viable for micro-CHP.) The energy sources with the lowest emissions of particulates and net-carbon dioxide, include solar power, biomass (with two-stage gasification into biogas
), and natural gas.
and the steam engine
. Both range from 10%-20% efficiency, and as of 2008, small quantities are in production for micro-CHP products. Other possible heat cycles include the Organic Rankine Cycle
(lower heat), Ericsson cycle
, and Stoddard cycle.
As an example, a PEMFC fuel cell
based micro-CHP has an electrical efficiency of 37% LHV and 33% HHV and a heat recovery efficiency of 52% LHV and 47% HHV with a service life
of 40,000 hours or 4000 start/stop cycles which is equal to 10 year use.
United States Department of Energy (DOE)
Technical Targets: 1–10 kW residential combined heat and power fuel cells operating on natural gas
.
1Standard utility natural gas delivered at typical residential distribution line pressures.
2Regulated AC net/lower heating value of fuel.
3Only heat available at 80 °C or higher is included in CHP energy efficiency calculation.
4Cost includes materials and labor costs to produce stack, plus any balance of plant necessary for stack operation. Cost defined at 50,000 unit/year production (250 MW in 5 kW modules).
5Based on operating cycle to be released in 2010.
6Time until >20% net power degradation.
, another option is Concentrated photovoltaics and thermal (CPVT), also sometimes called combined heat and power solar (CHAPS), is a cogeneration
technology used in concentrated photovoltaics that produce both electricity and heat in the same module. The heat may be employed in district heating
, water heating
and air conditioning, desalination
or process heat.
CPVT systems are currently in production in Europe, with Zenith Solar
developing CPVT systems with a claimed efficiency of 72%.
Sopogy
produces a micro Concentrated solar system
(microCSP) system based on parabolic trough
which can be installed above building or homes, the heat can be used for water heating or solar air conditioning
, a steam turbine
can also be installed to produce electricity.
systems has provided the opportunity for in-house power backup of residential-scale photovoltaic (PV) arrays. The results of a recent study show that a PV+CHP hybrid system not only has the potential to radically reduce energy waste in the status quo electrical and heating systems, but it also enables the share of solar PV to be expanded by about a factor of five. In some regions, in order to reduce waste from excess heat, an absorption chiller has been proposed to utilize the CHP-produced thermal energy for cooling of PV-CHP system. These trigen
+PV systems have the potential to save even more energy.
It is estimated that about 1,000 micro-CHP systems were in operation in the UK as of 2002. These are primarily "Whispergen" Stirling engine
s, and Senertec Dachs reciprocating engine
s. The market is supported by the government through regulatory work, and some government research money expended through the Energy Saving Trust and Carbon Trust
, which are public bodies supporting energy efficiency in the UK. Effective as of 7 April 2005, the UK government has cut the VAT from 17.5% to 5% for micro-CHP systems, in order to support demand for this emerging technology at the expense of existing, less environmentally friendly technology. The reduction in VAT is effectively a 10.63% subsidy
for micro-CHP units over conventional systems, which will help micro-CHP units become more cost competitive, and ultimately drive micro-CHP sales in the UK. Of the 24 million households in the UK, as many as 14 to 18 million are thought to be suitable for micro-CHP units. A factory in Horsham
UK for the production of SOFC based micro-CHP units is expected to start low-volume production in the second half of 2009
In Germany, 3,000 ecopower micro-CHP units have been installed, using the U.S. based Marathon Engine Systems long-life engine. The engine runs on natural gas and propane. The ecopower micro-CHP is also available in the United States. A factory in Heinsberg
, Germany for the production of SOFC based micro-CHP units started in June 2009 to produce 10,000 two-kilowatt units per year. The German government is offering large CHP incentives, including feed-in tariff
s and bonus payments for use of micro-CHP generated electricity. The United States federal government is offering a 10% tax credit for smaller CHP and micro-CHP commercial applications.
In South Korea subsidies will start at 80 percent of the cost of a domestic fuel cell.
The system is priced at about $14k, with the furnace being worth about $5k.
The engine generator has been demonstrated to run about 4000 hours per year (nearly 50% duty), and produce up to 5000 kWh of electricity per year, worth about $1k at the residential level. The system is internet connected and after about 4000 hours, it automatically sends an email requesting service. The main purpose of regular service is for an engine oil change.
It has been demonstrated in dozens of homes that Freewatt will produce about 50% of the electric power needs of a typical US home from the fuel now used to heat the home (which must be natural gas or propane), thereby doubling the value of the heating fuel purchased by the homeowner and significantly reducing the carbon footprint of the home by reducing electricity demand and emissions from large centralized power plants.
The product has already received numerous awards, including breakthrough product of the year from Popular Mechanics Magazine, and is expected by some to be widely available throughout the United States in 2008 or 2009. Estimates are that this product could be used in about 50 million homes in the United States. The Freewatt product is being brought to the national US and Canadian market by ECR International http://www.ecrinternational.com, the leading business partner of Climate Energy. ECR International is an 80 year old company with extensive line of heating and cooling products for the home.
Through a pilot program scheduled for mid-2009 in Southern Ontario, the Freewatt system is being offered exclusively by Eden Oak and offers homeowners a new option for controlling their energy costs and reducing their environmental footprint. The initiative, which reflects the collaborative efforts of the Government of Canada, Eden Oak, ECR International, Enbridge Gas Distribution and National Grid, will involve the sale and installation of the Freewatt systems in new Eden Oak communities in the Toronto area.
Trenergi Corp., Hopkinton, Massachusetts, an early stage company, in June 2010, announced its Trion residential, high-temperature (300 F) micro-CHP, in proof-of-concept stage, that operates on both gas and oil, demonstrating combined heat and electrical power efficiencies of up to 90%. Their first products will be 1, 3, and 5 kW units.
Also look at www.vegawatt.com.
There are definite pollution-reduction advantages if the unit is replacing an electric heating system powered by a coal power plant.
Also, like other distributed power systems, the end user can configure the unit as an emergency power source in the event of a power outage.
A big picture advantage of this approach is the ability to distribute power generation, locally, at the end-user rather than a remote power plant. If deployed on a large scale, this can reduce the need for new power plant installations and free-up transmission line capacity for other uses (e.g. solar energy or wind turbine farms). There is also the reduced long-range transmission losses. Avoiding transmission line losses and power plant construction reduces costs, energy consumption and pollution for everyone. In a fully realized distributed power generation scenario, micro-CHP may be used to supplement the less predictable generation provided by solar, wind and other energy sources, and therefore increase grid reliability.
, the Netherlands for a three year field testing until 2010 of HCNG
were 20% hydrogen is added to the local CNG
distribution net, the appliances involved are kitchen stove
s condensing boiler
s and micro-CHP boilers.
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....
to the single/multi family home or small office building.
Overview
Micro-chp is defined by the EC as being of less than 50 kW electrical power output. In the majority of energy applications, energy is required in multiple forms. These energy forms typically include some combination of: heating, ventilation, and air conditioningHVAC
HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
, mechanical energy
Mechanical energy
In physics, mechanical energy is the sum of potential energy and kinetic energy present in the components of a mechanical system. It is the energy associated with the motion and position of an object. The law of conservation of energy states that in an isolated system that is only subject to...
and electric power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
. Often, these additional forms of energy are produced by a heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
, running on a source of high-temperature heat. A heat engine can never have perfect efficiency, according to the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...
, therefore a heat engine will always produce a surplus of low-temperature heat. This is commonly referred to as waste heat
Waste heat
Waste heat sometimes called Secondary heat or Low-grade heat refers to heat produced by machines, electrical equipment and industrial processes for which no useful application is found. Energy is often produced by a heat engine, running on a source of high-temperature heat...
or "secondary heat", or "low-grade heat". This heat is useful for the majority of heating applications, however, it is sometimes not practical to transport heat energy over long distances, unlike electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
or fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
energy. By transporting fuel, however, the "waste heat" is essentially being transported along with the fuel, before the waste heat is actually produced.
To make efficient use of energy, the "waste heat" must be used purposefully. Since it is practical to transport electricity, but not always practical to transport waste heat, an energy efficient system must generate electricity near locations where the waste heat can be put to good use. This is known as a combined heat and power
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....
(CHP
CHP
-Healthcare:* Oporto Hospital Centre* Children's Hospital of Pittsburgh* Community Health Partnerships* Certified Health Physicist-Politics:* Christian Heritage Party * Christian Historical Party...
) system, or "cogeneration
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....
".
In a central power plant, the supply of "waste heat" may exceed the local heat demand. In such cases, if it is not desirable to reduce the power production, the excess waste heat must be disposed in e.g. cooling tower
Cooling tower
Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or in the case of closed circuit dry cooling towers rely...
s or sea cooling without being used. A way to avoid excess waste heat is to reduce the fuel input to the CHP plant, reducing both the heat and power output to balance the heat demand. In doing this, the power production is limited by the heat demand.
CHP systems are able to increase the total energy utilization of primary energy sources, such as fuel and concentrated solar thermal energy. Thus CHP has been steadily gaining popularity in all sectors of the energy economy, due to the increased costs of fuels, particularly oil-based fuels, and due to environmental concerns, particularly climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
.
In a traditional power plant delivering electricity to consumers, about 30% of the heat content of the primary heat energy source, such as biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
, coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
, solar thermal, natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
, petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
or uranium
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
, reaches the consumer, although the efficiency can be 20% for very old plants and 45% for newer gas plants. In contrast, a CHP system converts 15%–42% of the primary heat to electricity, and most of the remaining heat is captured for hot water
Water heating
Water heating is a thermodynamic process using an energy source to heat water above its initial temperature. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating...
or space heating
Space heating
A space heater is a self-contained device for heating an enclosed area. Space heating is generally employed to warm a small space, and is usually held in contrast with central heating, which warms many connected spaces at once...
. In total, as much as 90% of the heat from the primary energy source goes to useful purposes when heat production does not exceed the demand.
CHP systems have benefited the industrial sector since the beginning of the industrial revolution. For three decades, these larger CHP systems were more economically justifiable than micro-CHP, due to the economy of scale. After the year 2000, micro-CHP has become cost effective in many markets around the world, due to rising energy costs. The development of micro-CHP systems has also been facilitated by recent technological developments of small heat engines. This includes improved performance and/or cost-effectiveness of fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
s, Stirling engine
Stirling engine
A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....
s, steam engines, gas turbines, diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
s and Otto engine
Otto engine
-Otto Engine Types:There are three types of internal combustion engines designed by German inventors Nikolaus August Otto and his partner Eugen Langen. They are the 1862 compression engine, which failed, the 1864 atmospheric engine, and the engine known today as the "Gasoline Engine", the Otto...
s.
Micro-CHP systems
In many cases industrial CHP systems primarily generate electricityElectricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...
and heat is a by-product; micro-CHP systems in homes or small commercial buildings are controlled by heat-demand, delivering electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
as the by-product. When used primarily for heat in circumstances of fluctuating electrical demand, micro-CHP systems will often generate more electricity than is instantly being demanded.
To date, micro-CHP systems achieve much of their savings, and thus attractiveness to consumers, through a "generate-and-resell" or net metering
Net metering
Net metering is an electricity policy for consumers who own renewable energy facilities or V2G electric vehicles. "Net", in this context, is used in the sense of meaning "what remains after deductions" — in this case, the deduction of any energy outflows from metered energy inflows...
model wherein home-generated power exceeding the instantaneous in-home needs is sold back to the electrical utility. This system is efficient because the energy used is distributed and used instantaneously over the electrical grid. The main losses are in the transmission from the source to the consumer which will typically be less than losses incurred by storing energy locally or generating power at less than the peak efficiency of the micro-CHP system. So, from a purely technical standpoint dynamic demand management
Dynamic demand (electric power)
Dynamic Demand is the name of a semi-passive technology for adjusting load demands on an electrical power grid. The concept is that by monitoring the frequency of the power grid, as well as their own...
and net-metering are very efficient.
Another positive to net-metering is the fact that it is fairly easy to configure. The user's electrical meter is simply able to record electrical power exiting as well as entering the home or business. As such, it records the net amount of power entering the home. For a grid with relatively few micro-CHP users, no design changes to the electrical grid need be made. Additionally, in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, federal and now many state regulations require utility operators to compensate anyone adding power to the grid. From the standpoint of grid operator, these points present operational and technical as well as administrative burdens. As a consequence, most grid operators compensate non-utility
Utility
In economics, utility is a measure of customer satisfaction, referring to the total satisfaction received by a consumer from consuming a good or service....
power-contributors at less than or equal to the rate they charge their customers. While this compensation scheme may seem almost fair at first glance, it only represents the consumer’s cost-savings of not purchasing utility power versus the true cost of generation and operation to the micro-CHP operator. Thus from the standpoint of micro-CHP operators, net-metering is not ideal.
While net-metering is a very efficient mechanism for using excess energy generated by a micro-CHP system, it is not without its detractors. Of the detractors' main points, the first to consider is that while the main generating source on the electrical grid is a large commercial generator, net-metering generators "spill" power to the smart grid in a haphazard and unpredictable fashion. However, the effect is negligible if there are only a small percentage of customers generating electricity and each of them generates a relatively small amount of electricity. When turning on an oven or space heater, about the same amount of electricity is drawn from the grid as a home generator puts out. If the percentage of homes with generating systems becomes large, then the effect on the grid may become significant. Coordination among the generating systems in homes and the rest of the grid may be necessary for reliable operation and to prevent damage to the grid.
In an evaluation from 2008 by Claverton Energy Group, Stirling engined micro CHP was deemed the most cost effective of the various microgeneration technologies in abating carbon in the UK.
Engine types and technologies
Micro-CHP engine systems are currently based on several different technologies:- Internal combustion engineInternal combustion engineThe internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s - Stirling engineStirling engineA Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....
s - Steam engineSteam engineA steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
s - Microturbines
Fuels and engine types
The majority of cogeneration systems use natural gas for fuel, because natural gas burns easily and cleanly, it can be inexpensive, it is available in most areas and is easily transported through pipelines, which already exist for many homes. Natural gas is suitable for internal combustion engineInternal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s, such as Otto engine
Otto engine
-Otto Engine Types:There are three types of internal combustion engines designed by German inventors Nikolaus August Otto and his partner Eugen Langen. They are the 1862 compression engine, which failed, the 1864 atmospheric engine, and the engine known today as the "Gasoline Engine", the Otto...
and gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
systems. Gas turbines are used in many small systems due to their high efficiency, small size, clean combustion, durability and low maintenance requirements. Gas turbines designed with foil bearing
Foil bearing
Foil bearings, also known as foil-air bearings, are a type of air bearing. A shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning quickly enough, the working fluid pushes the foil away from the shaft so that there is no more contact...
s and air-cooling, operate without lubricating oil or coolants. The waste heat of gas turbines is mostly in the exhaust, whereas the waste heat of reciprocating internal combustion engine
Reciprocating engine
A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...
s, is split between the exhaust and cooling system.
The future of combined heat and power, particularly for homes and small businesses, will continue to be affected by the price of fuel, including natural gas. As fuel prices continue to climb, this will make the economics more favorable for energy conservation measures, and more efficient energy use
Efficient energy use
Efficient energy use, sometimes simply called energy efficiency, is the goal of efforts to reduce the amount of energy required to provide products and services. For example, insulating a home allows a building to use less heating and cooling energy to achieve and maintain a comfortable temperature...
, including CHP and micro-CHP.
Fuels
There are many types of fuels and sources of heat that may be considered for micro-CHP. The properties of these sources vary in terms of system cost, heat cost, environmental effects, convenience, ease of transportation and storage, system maintenance, and system life. Some of the heat sources and fuels that are being considered for use with micro-CHP include: biomassBiomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
, LPG, vegetable oil (such as rapeseed
Rapeseed
Rapeseed , also known as rape, oilseed rape, rapa, rappi, rapaseed is a bright yellow flowering member of the family Brassicaceae...
oil), woodgas, solar thermal
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
, and natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
, as well as multi-fuel systems. (Nuclear power is hazardous at small scales, due to radiation risks, so it is generally not viable for micro-CHP.) The energy sources with the lowest emissions of particulates and net-carbon dioxide, include solar power, biomass (with two-stage gasification into biogas
Biogas
Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal dung, and kitchen waste can be converted into a gaseous fuel called biogas...
), and natural gas.
Engines
External combustion engines can run on any high-temperature heat source. These engines include the Stirling engineStirling engine
A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....
and the steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
. Both range from 10%-20% efficiency, and as of 2008, small quantities are in production for micro-CHP products. Other possible heat cycles include the Organic Rankine Cycle
Organic Rankine Cycle
The Organic Rankine cycle is named for its use of an organic, high molecular mass fluid with a liquid-vapor phase change, or boiling point, occurring at a lower temperature than the water-steam phase change. The fluid allows Rankine cycle heat recovery from lower temperature sources such as...
(lower heat), Ericsson cycle
Ericsson cycle
The Ericsson cycle is named after inventor John Ericsson, who designed and built many unique heat engines based on various thermodynamic cycles. He is credited with inventing two unique heat engine cycles and developing practical engines based on these cycles...
, and Stoddard cycle.
Fuel cell micro-CHP
Fuel cells generate electricity and heat as a by product. The advantages over stirling CHP are no moving parts, less maintenance, and quieter operation. The surplus electricity can be delivered back to the grid.As an example, a PEMFC fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
based micro-CHP has an electrical efficiency of 37% LHV and 33% HHV and a heat recovery efficiency of 52% LHV and 47% HHV with a service life
Service life
A product's service life is its expected lifetime, or the acceptable period of use in service. It is the time that any manufactured item can be expected to be 'serviceable' or supported by its manufacturer....
of 40,000 hours or 4000 start/stop cycles which is equal to 10 year use.
United States Department of Energy (DOE)
United States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
Technical Targets: 1–10 kW residential combined heat and power fuel cells operating on natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
.
| Type | 2008 Status | 2012 | 2015 | 2020 |
|---|---|---|---|---|
| Electrical efficiency at rated power2 | 34% | 40% | 42.5% | 45% |
| CHP energy efficiency3 | 80% | 85% | 87.5% | 90% |
| Factory cost4 | $750/kW | $650/kW | $550/kW | $450/kW |
| Transient response (10%–90% rated power) | 5 min | 4 min | 3 min | 2 min |
| Start-up time from 20 °C ambient temperature | 60 min | 45 min | 30 min | 20 min |
| Degradation with cycling5 | < 2%/1000 h | 0.7%/1000 h | 0.5%/1000 h | 0.3%/1000 h |
| Operating lifetime6 | 6,000 h | 30,000 h | 40,000 h | 60,000 h |
| System availability | 97% | 97.5% | 98% | 99% |
1Standard utility natural gas delivered at typical residential distribution line pressures.
2Regulated AC net/lower heating value of fuel.
3Only heat available at 80 °C or higher is included in CHP energy efficiency calculation.
4Cost includes materials and labor costs to produce stack, plus any balance of plant necessary for stack operation. Cost defined at 50,000 unit/year production (250 MW in 5 kW modules).
5Based on operating cycle to be released in 2010.
6Time until >20% net power degradation.
CPVT
This can be achieved by Photovoltaic thermal hybrid solar collectorPhotovoltaic thermal hybrid solar collector
Photovoltaic thermal hybrid solar collectors, sometimes known as hybrid PV/T systems or PVT, are systems that convert solar radiation into thermal and electrical energy...
, another option is Concentrated photovoltaics and thermal (CPVT), also sometimes called combined heat and power solar (CHAPS), is a cogeneration
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....
technology used in concentrated photovoltaics that produce both electricity and heat in the same module. The heat may be employed in district heating
District heating
District heating is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating...
, water heating
Water heating
Water heating is a thermodynamic process using an energy source to heat water above its initial temperature. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating...
and air conditioning, desalination
Desalination
Desalination, desalinization, or desalinisation refers to any of several processes that remove some amount of salt and other minerals from saline water...
or process heat.
CPVT systems are currently in production in Europe, with Zenith Solar
Zenith Solar
Zenith Solar is an Israeli solar energy company based in Ness Ziona. It was founded in 2006 by Roy Segev and Bob Whelen, who is also its chief executive....
developing CPVT systems with a claimed efficiency of 72%.
Sopogy
Sopogy
Sopogy a solar thermal technology supplier was founded in 2002 at the Honolulu, Hawaii based clean technology incubator known as . The company began its research on concentrating solar thermal energy to produce steam and thermal heat for absorption chiller. The company has also developed...
produces a micro Concentrated solar system
CSP
-General:* CSP * Caledonian Steam Packet Company* California Society of Printmakers* California State Parks* Carol Shea-Porter* Center for Security Policy* Civil Services of Pakistan* Certified Safety Professional...
(microCSP) system based on parabolic trough
Parabolic trough
A parabolic trough is a type of solar thermal energy collector. It is constructed as a long parabolic mirror with a Dewar tube running its length at the focal point. Sunlight is reflected by the mirror and concentrated on the Dewar tube...
which can be installed above building or homes, the heat can be used for water heating or solar air conditioning
Solar air conditioning
Solar air conditioning refers to any air conditioning system that uses solar power.This can be done through passive solar, solar thermal energy conversion and photovoltaic conversion . The U.S...
, a steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....
can also be installed to produce electricity.
CHP+PV
The recent development of small scale CHPCHP
-Healthcare:* Oporto Hospital Centre* Children's Hospital of Pittsburgh* Community Health Partnerships* Certified Health Physicist-Politics:* Christian Heritage Party * Christian Historical Party...
systems has provided the opportunity for in-house power backup of residential-scale photovoltaic (PV) arrays. The results of a recent study show that a PV+CHP hybrid system not only has the potential to radically reduce energy waste in the status quo electrical and heating systems, but it also enables the share of solar PV to be expanded by about a factor of five. In some regions, in order to reduce waste from excess heat, an absorption chiller has been proposed to utilize the CHP-produced thermal energy for cooling of PV-CHP system. These trigen
Trigen
Trigen can refer to:*Trigeneration, a variant of cogeneration where the same fuel is used for power generation, heating and cooling.* Trigen Energy Corp., a U.S. district energy and CHP company operating as Veolia Energy North America since February 2011....
+PV systems have the potential to save even more energy.
Market status and government policy
The largest deployment of micro-CHP is in Japan at this time (2009), where over 90,000 units are in place, with the vast majority being of the "ECO-WILL" type. Six Japanese energy companies launched the 300 W–1 kW PEMFC ENE FARM product in 2009, with 3,000 installed units in 2008, a production target of 150,000 units for 2009–2010 and a target of 2,500,000 units in 2030.It is estimated that about 1,000 micro-CHP systems were in operation in the UK as of 2002. These are primarily "Whispergen" Stirling engine
Stirling engine
A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....
s, and Senertec Dachs reciprocating engine
Reciprocating engine
A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...
s. The market is supported by the government through regulatory work, and some government research money expended through the Energy Saving Trust and Carbon Trust
The Carbon Trust
The Carbon Trust is a not for dividend company limited by guarantee created by the UK government to help businesses and public organisations to reduce their emissions of carbon dioxide into the atmosphere, through improved energy efficiency and developing commercial low carbon technology...
, which are public bodies supporting energy efficiency in the UK. Effective as of 7 April 2005, the UK government has cut the VAT from 17.5% to 5% for micro-CHP systems, in order to support demand for this emerging technology at the expense of existing, less environmentally friendly technology. The reduction in VAT is effectively a 10.63% subsidy
Subsidy
A subsidy is an assistance paid to a business or economic sector. Most subsidies are made by the government to producers or distributors in an industry to prevent the decline of that industry or an increase in the prices of its products or simply to encourage it to hire more labor A subsidy (also...
for micro-CHP units over conventional systems, which will help micro-CHP units become more cost competitive, and ultimately drive micro-CHP sales in the UK. Of the 24 million households in the UK, as many as 14 to 18 million are thought to be suitable for micro-CHP units. A factory in Horsham
Horsham
Horsham is a market town with a population of 55,657 on the upper reaches of the River Arun in the centre of the Weald, West Sussex, in the historic County of Sussex, England. The town is south south-west of London, north-west of Brighton and north-east of the county town of Chichester...
UK for the production of SOFC based micro-CHP units is expected to start low-volume production in the second half of 2009
In Germany, 3,000 ecopower micro-CHP units have been installed, using the U.S. based Marathon Engine Systems long-life engine. The engine runs on natural gas and propane. The ecopower micro-CHP is also available in the United States. A factory in Heinsberg
Heinsberg
Heinsberg is the capital of the district Heinsberg in North Rhine-Westphalia, Germany. It is situated near the border with the Netherlands, on the river Wurm, approx...
, Germany for the production of SOFC based micro-CHP units started in June 2009 to produce 10,000 two-kilowatt units per year. The German government is offering large CHP incentives, including feed-in tariff
Feed-in Tariff
A feed-in tariff is a policy mechanism designed to accelerate investment in renewable energy technologies. It achieves this by offering long-term contracts to renewable energy producers, typically based on the cost of generation of each technology...
s and bonus payments for use of micro-CHP generated electricity. The United States federal government is offering a 10% tax credit for smaller CHP and micro-CHP commercial applications.
In South Korea subsidies will start at 80 percent of the cost of a domestic fuel cell.
Products and distributors
In 2007, the United States company "Climate Energy" of Massachusetts has introduced its flagship product named "Freewatt"http://www.freewatt.com, a micro-CHP system for sale in the Northeast US domestic and small business market. The Freewatt system uses a Honda MCHP engine bundled with a high-efficiency gas furnace (for warm air systems) or boiler (for hydronic or forced hot water heating systems). The generator alone is not available for purchase separate from the furnace. The engine generates up to 1.2 kW of electricity at 20% efficiency. Most of the waste heat is captured for space heating, resulting in 85% efficiency overall. The system generates electricity opportunistically, only when space heating is needed during cold weather.The system is priced at about $14k, with the furnace being worth about $5k.
The engine generator has been demonstrated to run about 4000 hours per year (nearly 50% duty), and produce up to 5000 kWh of electricity per year, worth about $1k at the residential level. The system is internet connected and after about 4000 hours, it automatically sends an email requesting service. The main purpose of regular service is for an engine oil change.
It has been demonstrated in dozens of homes that Freewatt will produce about 50% of the electric power needs of a typical US home from the fuel now used to heat the home (which must be natural gas or propane), thereby doubling the value of the heating fuel purchased by the homeowner and significantly reducing the carbon footprint of the home by reducing electricity demand and emissions from large centralized power plants.
The product has already received numerous awards, including breakthrough product of the year from Popular Mechanics Magazine, and is expected by some to be widely available throughout the United States in 2008 or 2009. Estimates are that this product could be used in about 50 million homes in the United States. The Freewatt product is being brought to the national US and Canadian market by ECR International http://www.ecrinternational.com, the leading business partner of Climate Energy. ECR International is an 80 year old company with extensive line of heating and cooling products for the home.
Through a pilot program scheduled for mid-2009 in Southern Ontario, the Freewatt system is being offered exclusively by Eden Oak and offers homeowners a new option for controlling their energy costs and reducing their environmental footprint. The initiative, which reflects the collaborative efforts of the Government of Canada, Eden Oak, ECR International, Enbridge Gas Distribution and National Grid, will involve the sale and installation of the Freewatt systems in new Eden Oak communities in the Toronto area.
Trenergi Corp., Hopkinton, Massachusetts, an early stage company, in June 2010, announced its Trion residential, high-temperature (300 F) micro-CHP, in proof-of-concept stage, that operates on both gas and oil, demonstrating combined heat and electrical power efficiencies of up to 90%. Their first products will be 1, 3, and 5 kW units.
Also look at www.vegawatt.com.
Advantages
The advantage of having some "ownership" of one's electrical power was discussed above. Actual utility bill savings are probably minimal when looking at life-cycle cost of this approach as compared to a simple natural gas furnace.There are definite pollution-reduction advantages if the unit is replacing an electric heating system powered by a coal power plant.
Also, like other distributed power systems, the end user can configure the unit as an emergency power source in the event of a power outage.
A big picture advantage of this approach is the ability to distribute power generation, locally, at the end-user rather than a remote power plant. If deployed on a large scale, this can reduce the need for new power plant installations and free-up transmission line capacity for other uses (e.g. solar energy or wind turbine farms). There is also the reduced long-range transmission losses. Avoiding transmission line losses and power plant construction reduces costs, energy consumption and pollution for everyone. In a fully realized distributed power generation scenario, micro-CHP may be used to supplement the less predictable generation provided by solar, wind and other energy sources, and therefore increase grid reliability.
Research
Testing is underway in AmelandAmeland
Ameland is a municipality and one of the West Frisian Islands off the north coast of the Netherlands. It consists mostly of sand dunes. It is the third major island of the West Frisians. It neighbours islands Terschelling to the West and Schiermonnikoog to the East...
, the Netherlands for a three year field testing until 2010 of HCNG
HCNG
HCNG is a mixture of compressed natural gas and 4–9 percent hydrogen by energy. It may be used as a fuel gas for internal combustion engines and home appliances...
were 20% hydrogen is added to the local CNG
Compressed natural gas
Compressed natural gas is a fossil fuel substitute for gasoline , diesel, or propane/LPG. Although its combustion does produce greenhouse gases, it is a more environmentally clean alternative to those fuels, and it is much safer than other fuels in the event of a spill...
distribution net, the appliances involved are kitchen stove
Kitchen stove
A kitchen stove, cooking stove, cookstove, or cooker is a kitchen appliance designed for the purpose of cooking food. Kitchen stoves rely on the application of direct heat for the cooking process and may also contain an oven, used for baking.In the industrialized world, as stoves replaced open...
s condensing boiler
Condensing boiler
A condensing boiler utilizes the latent heat of water produced from the burning of fuel, in addition to the standard sensible heat, to increase its efficiency.-Principles of work:...
s and micro-CHP boilers.
See also
- Distributed generationDistributed generationDistributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized energy or distributed energy, generates electricity from many small energy sources....
- District heatingDistrict heatingDistrict heating is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating...
- Geothermal power in IcelandGeothermal power in IcelandDue to the special geological location of Iceland, the high concentration of volcanoes in the area is often an advantage in the generation of geothermal energy, the heating and production of electricity...
- Grid-tied electrical systemGrid-tied electrical systemA 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...
- Home fuel cellHome fuel cellA home fuel cell, also called micro combined heat and power and microgeneration, is a residential-scaled clean energy system. A home fuel cell is an alternative energy technology that increases efficiency by simultaneously generating power and heat from one unit, on-site within a home...
- Pinch analysisPinch analysisPinch analysis is a methodology for minimising energy consumption of chemical processes by calculating thermodynamically feasible energy targets and achieving them by optimising heat recovery systems, energy supply methods and process operating conditions...
- Relative cost of electricity generated by different sources
- Stationary fuel cell applications
- TrigenerationTrigenerationTrigeneration, also called CCHP , refers to the simultaneous generation of electricity, useful heating and useful cooling from the same original heat source such as fuel or solar energy...
- Virtual power plantVirtual power plantA virtual power plant is a cluster of distributed generation installations which are collectively run by a central control entity....
Codes and standards
- Fuel cell gas appliances up to 70 kW
- Installation permitting guidance for hydrogen and fuel cells stationary applications
- Standard for the installation of stationary fuel cell power systems
External links
- DOE fuel cells used in combined heat and power
- EU-HEGEL a reciprocating engine CHP
- Information about the Warm Air Freewatt Cogeneration System
- Mini and micro CHP – Market Assessment and Development Plan
- Micro CHP project in the Netherlands
- Accelerating the Development of Micro and Mini Cogeneration
- CSMonitor: It heats. It powers. Is it the future of home energy?
- Micro CHP information, products, economics, publications
- the World Alliance for Decentralized Energy
- Information about the Disenco HomePowerPlant