Micro combined heat and power or micro-CHP is
an extension of the idea of cogeneration to the single/multi family home or small
office building.
A micro-CHP system is a small heat engine
(power plant) which provides all the power for an individual building; heating, ventilation, and
air conditioning, mechanical energy and electric
power. It is a smaller-scale version of cogeneration
schemes which have been used with large scale electric power plants. The
purpose is to utilize more of the energy in the fuel. The reason for using such
systems is that heat engines, such as steam
power plants which generate the electric power needed for modern life by
burning fuel, are not very efficient. Due to Carnot's theorem, a heat engine
cannot be 100% efficient; it cannot convert anywhere near all the heat in the
fuel it burns into useful forms such as electricity. So heat engines always
produce a surplus of low-temperature waste heat,
called "secondary heat" or "low-grade heat". Modern plants
are limited to efficiencies of about 33 - 60% at most, so 40 - 67% of the
energy is exhausted as waste heat. In the past this energy was usually wasted
to the environment. Cogeneration systems, built in recent years in
cold-climate countries, utilize the waste heat produced by large power plants
for heating, piping hot water from the plant into buildings in the surrounding
community.
However, it is not practical to transport heat long
distances, due to heat loss from the pipes. Since electricity can be
transported practically, it is more efficient to generate the electricity near
where the waste heat can be used. So in a "micro-combined heat and power
system" (micro-CHP), small power plants are instead located where the
secondary heat can be used, in individual buildings. Micro-CHP are defined by
the EC as being of less than 50 kW electrical power output.
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 towers 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
cost-effectiveness of fuel cells, Stirling
engines, steam engines, gas
turbines, diesel engines and Otto
engines.
Delta-ee consultants stated in 2013 that with 64% of global
sales the fuel cell micro-combined heat and power passed the conventional
systems in sales in 2012.
PEMFC
fuel cell mCHP operates at low temperature (50 to 100 °C) and needs high purity
hydrogen, its prone to contamination, changes are made to operate at higher
temperatures and improvements on the fuel reformer. SOFC fuel cell mCHP
operates at a high temperature (500 to 1,000 °CP) and can handle different
energy sources well but the high temperature requires expensive materials to
handle the temperature, changes are made to operate at a lower temperature.
Because of the higher temperature SOFC in general has a longer start-up time.
CHP systems linked to absorption chillers can use waste heat for refrigeration.
Micro-CHP systems
In many cases industrial CHP systems primarily generate electricity 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 does have 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
A 2013 UK report from Ecuity Consulting stated that MCHP is
the most cost-effective method of utilising gas to generate energy at the
domestic level.
Engine types and technologies
Micro-CHP engine systems are currently based on several
different technologies:
- Internal combustion engines
- Stirling engines
- Steam engines (using either the traditional water or organic chemicals such as refrigerants)
- 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 engines, 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
bearings 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 engines, 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.
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: biomass,
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.
Engines
External combustion engines can run on
any high-temperature heat source. These engines include the Stirling
engine, hot "gas" turbocharger, steam
engine. Both range from 10%-20% efficiency, and as of 2008, small
quantities are in production for micro-CHP products.
Other possibilities include the Organic Rankine cycle, which operates at
lower temperatures and pressures using low-grade heat sources. The primary
advantage to this is that the equipment is essentially an air-conditioning or
refrigeration unit operating as an engine, whereby the piping and other
components need not be designed for extreme temperatures and pressures,
reducing cost and complexity. Electrical efficiency suffers, but it is presumed
that such a system would be utilizing waste heat or a heat source such as a
wood stove or gas boiler that would exist anyway for purposes of space heating.
Fuel cell micro-CHP
Fuel cells generate electricity and heat as a by product.
The advantages for a stationary fuel cell application
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 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.
In 2013 Lifetime is 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.
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.
Thermoelectrics
Thermoelectric generators operating on the Seebeck
Effect show promise due to their total absence of moving parts. Efficiency,
however, is the major concern as most thermoelectric devices fail to achieve 5%
efficiency even with high temperature differences.
Solar micro-CHP
CPVT
This can be achieved by Photovoltaic thermal hybrid
solar collector, 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.
CHP+PV
The recent development of small scale CHP 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.
Market status and government policy
Japan
The largest deployment of micro-CHP is in Japan in 2009 where
over 90,000 units in place, with the vast majority being of Hondas
"ECO-WILL" type. Six Japanese energy companies launched
the 300 W–1 kW PEMFC/SOFC
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. Per December 2012 Panasonic and
Tokyo Gas Co., Ltd. sold about 21,000 PEM Ene-Farm units in Japan for a price
of $22,600 before installation. Toshiba and Osaka Gas Co Ltd / Nichigas
installed 6,500 PEM ENE FARM units (manufactured by Chofu Seisakusho Co Ltd)
per nov 2011. In the middle of 2012 JX Nippon Oil Co.&Sanyo and Seibu Gas
Energy Co sold around 4000 Ene Farm units. Aisin Seiki
in combination with Osaka Gas, Kyocera, Chofu Seisakusho and Toyota started in April 2012
with the sales of the SOFC ENE-FARM Type S for around $33,500 before
installation. 20.000 units where sold in 2012 overall within the Ene Farm
project. For 2013 a state subsidy for 50,000 units is in place.
South Korea
In South Korea subsidies will start at 80 percent of the
cost of a domestic fuel cell.,. The Renewable portfolio standard program
with renewable energy
certificates runs from 2012 to 2022. Quota systems favor large, vertically
integrated generators and multinational electric utilities, if only because
certificates are generally denominated in units of one megawatt-hour. They are
also more difficult to design and implement than an a Feed-in
tariff. Around 350 residential mCHP units where installed in 2012.
PEMFC by GS FuelCell, FuelCell Power (now Doosan), Hyundai
Hysco, IHI and Hyosung, SOFC by KEPRI, LS Industrial
Systems (from ClearEdge Power), Samsung Everland (ClearEdge
Power), MCFC by POSCO
Energy (FuelCell Energy)
and Doosan.
Europe
The European public–private partnership Fuel Cells and
Hydrogen Joint Undertaking Seventh
Framework Programme project ene.field deploys in 2017 up 1,000 residential
fuel cell Combined Heat and Power (micro-CHP) installations in 12 states. Per
2012 the first 2 installations have taken place.
Germany
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 tariffs and bonus payments for use of micro-CHP
generated electricity. Ceramic Fuel Cells installs until 2014 up to 100
SOFC units under the SOFT-PACT project with E.ON in Germany and the UK. The
German testing project Callux (BDR Thermea/BAXI (Toshiba), HEXIS, Vaillant
(Sunfire SOFC), Elcore, Viessmann
(Panasonic), Bosch Thermotechnik (Aisin Seiki)) has 350 Mchp installations per
nov 2013. North-Rhine Westphalia launched a 250
million subsidy program for up to 50 kilowatts lasting until 2017. New in the
market are Tropical
and Elcore where the latter produces a 300W addon to an existing boiler.
The Netherlands
The micro-CHP subsidy was ended in 2012. To test the effects
of mCHP on a smart grid, 45 natural gas
SOFC units (each 1,5
kWh) from Republiq Power (Ceramic Fuel Cells) will be placed on Ameland in 2013
to function as a virtual power plant.
UK
It is estimated that about 1,000 micro-CHP systems were in
operation in the UK as of 2002. These are primarily "Whispergen" Stirling
engines, and Senertec Dachs reciprocating engines. 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 early 2012 less than 1000 1 kWe BAXI PEM micro-CHP units from BDR Thermea
where installed
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 20% 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. Two fuel cell varieties of mCHP
co-generation units are almost ready for mainstream production and are planned
for release to commercial markets in early in 2014. With the UK Government's
Feed-In-Tariff available for a 10 year period, a wide uptake of the technology
is anticipated.
United States
The federal government is offering a 10% tax credit for
smaller CHP and micro-CHP commercial applications.
In 2007, the United States company "Climate
Energy" of Massachusetts introduced the "Freewatt, a micro-CHP system
based on a Honda MCHP engine bundled with a gas furnace (for warm air systems)
or boiler (for hydronic or forced hot water heating systems). Through a pilot
program scheduled for mid-2009 in Southern Ontario, the Freewatt system is
being offered by Eden Oak with support from ECR International, Enbridge Gas
Distribution and National Grid.
Trenergi Corp, Massachusetts, an early stage company, in
June 2010, announced its Trion residential, high-temperature (300 F) micro-CHP
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.
Research
Testing is underway in Ameland, 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 stoves condensing
boilers and micro-CHP boilers.
Micro-CHP Accelerator, a field trial performed between 2005
and 2008, studied the performance of 87 Stirling
engine and internal combustion engine devices in
residential houses in the UK. This study found that the devices resulted in
average carbon savings of 9% for houses with heat demand over 54 GJ/year.
An ASME (American Society of Mechanical Engineers) paper
fully describes the performance and operating experience with two residential
sized Combined Heat and Power units which were in operation from 1979 through
1995. The first unit was an automatic coal fired steam electric Combined Heat
and Power system, based on the Rankine Steam Cycle. The unit was initially
fired in 1979, operating with a steam turbine-generator for two years, and was
modified with a reciprocating uniflow expander for an additional two years
operation. The unit functioned reliably, with only four forced outages during
the four years of operation. The second system was diesel engine-generator
based, again a Combined Heat and Power System, which was started in 1987 and
operated for seven seasons into 1995. The system efficiency averaged 90% during
the heating season, and showed remarkably low machinery wear and minimal
maintenance during the eight year run.
SUBSCRIBERS - ( LINKS) :FOLLOW / REF / 2 /
findleverage.blogspot.com
Krkz77@yahoo.com
+234-81-83195664
For affiliation:
No comments:
Post a Comment