Without
warning, the August 14, 2003, power blackout removed electricity
for millions of people in the United States and Canada. The next
day manufacturers still had no power, contributing to an estimated
cost to the U.S. economy of $6 billion.
Power outage headlines appear in newspapers across the nation.
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Meanwhile, in Ontario,
New York, Harbec Plastics, which machines complicated plastics
parts, operated during the blackout without interruption, owing
to an array of 25 Capstone microturbines. Fired by natural gas,
each microturbine produces 30 kilowatts (kW) of electricity and
virtually no pollutants. The array's waste heat is recovered
and used both to heat water and air (in winter) and cool the building
space in summer.
Typically,
about two-thirds of the fuel energy used to generate electricity
in central power stations is discarded as waste heat and then as losses
incurred in power transmission and distribution. By the time the
power reaches the point of use, total efficiency can drop to 30%. However,
efficiency can be raised to more than 70% by locating each power
source close to the customer and productively using the source's
waste heat for heating, cooling, and controlling humidity in each appropriately
sized commercial or institutional building. Since the 1990s the Department
of Energy and the private sector have worked together to develop such
distributed energy (DE) technologies, also called cooling, heating,
and power (CHP) units and, more recently, integrated energy systems
(IES).
DOE is seeking
to demonstrate that IES units in operation throughout the United
States can increase the nation's energy efficiency,
reliability, and security, reduce
dependence on imported oil, and simultaneously lower emissions of pollutants
that threaten health and a stable climate. DOE's goals are to
develop the next generation of clean, efficient, reliable, and affordable
DE technologies, integrate these technologies into appropriately sized
end-use sites, and capture waste heat, or thermal energy, to more than
double energy efficiency for heating and cooling of buildings.
Ready
for Prime Time
DOE asked
ORNL to focus on three types of energy sources, or "prime
movers,"
for IES units: industrial gas turbines, reciprocating engines, and
microturbines. All of these sources can burn natural gas and produce
two types of energy: electricity and waste heat. These sources would
be integrated
with a "thermally activated" technology,
such as an absorption chiller for cooling, a desiccant wheel for
dehumidification, or a steam generator or heat exchanger for heating
water or air.
ORNL supported
the development by UTC Power, a United Technologies Company, of
the UTC PureComfort™ system,
a reliable IES with ultra-low emissions that features a 112-ton
absorption chiller powered by waste heat from four to six 60-kW
microturbines.
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This microturbine in the ORNL Recuperator Testing Facility is used to test metal specimens to determine their suitability for high-temperature recuperators.
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The double-effect chiller provides cooling and
heating from the same unit, conserving space and simplifying
design. In summer the chiller uses waste heat from the microturbine
as the source of energy for driving the fluid that extracts
heat from water to chill and provide air conditioning. The
CHP technology has an efficiency of up to 80%.
ORNL researchers
have teamed with industrial partners to figure out how to capture
heat from each turbine or engine and transfer the heat to a thermally
activated system to provide cooling, dehumidification, or heating.
ORNL's Jim Sand has promoted
the use of waste heat for dehumidification in schools and other buildings
to improve air quality and prevent the growth of mold and other allergens.
Waste heat from engines and turbines can be combined with a desiccant
system to create a more comfortable environment where temperature and
humidity
are controlled independently.
Air can be passed through a desiccant wheel, which absorbs the moisture
and sends the resulting dry air into the building. The waste heat dries
the desiccant wheel so that it can again pick up moisture from indoor
air.
In 2001 DOE asked ORNL to solicit proposals from companies that
manufacture engines, turbines, and heat exchangers, as well as
from end users that can benefit from IES units. ORNL personnel served
as technical project managers in cost-shared contracts between DOE
and industry, which bore 43% of the cost. The ORNL project managers
provided technical expertise to the industrial partners and helped
identify the best ways to capture
waste heat for making what the end user wanted, such as chilled
water for air conditioning or heat for steam. By 2004 several partners
had met the DOE goal of combining individually
optimized products on-site.
One project
at a hospital and strategic command center at Fort Bragg Army Base
in North Carolina included a gas turbine, absorption chiller, steam
generator, and Honeywell control system that constantly provides
power, heating, and cooling. A second project was a gas turbine
that provides both electricity and chilled water for air conditioning
to the tenants of an Austin, Texas, industrial park. A third was
a project in New York where a skid-mounted UTC PureComfort 240
system was installed on the roof of an A&P Supermarket. The
system
supplies electricity and chilled water year-round for the supermarket's
refrigeration cases. Waste heat is also used to heat the supermarket
in the winter months.
The DOE goal for 2010 is that each manufacturer
would produce a single optimized IES package because each
integrated or modular IES package will be more cost effective, require
little on-site engineering, and offer a higher overall energy efficiency.
By 2010 DOE hopes to show that single optimized IES packages
can meet targets of a 32% reduction in energy usage and a 46% reduction
in carbon dioxide emissions. ORNL is contributing to this effort by
helping with integration, size reduction, and packaging of CHP technologies
to improve energy efficiency.
ORNL researchers
are also working with industrial partners to oversee the design,
development, installation, and operation of IES units in larger
market sectors such as hotels, supermarkets, hospitals and medical
centers, movie theaters, and high schools and colleges. In 2004 the
ORNL researchers—Randy Hudson, Jan Berry, Jim Sand, and Therese
Stovall—began monitoring and collecting data on the operation
of the newly installed
IES units throughout the country.
Research Payoffs
Patti Garland,
an ORNL engineer and CHP program manager, has been a principal
investigator for experiments at DOE's Integrated Energy
Systems Test Center at the University of Maryland. "We
integrated off-the-shelf equipment into an IES unit at the university's
Chesapeake Building," she says. "This building, which is occupied by more than 150 people,
has four miles of cables and more than 190 data points from which we
measure real-time operating performance of the test equipment. We conducted
performance testing on the IES there, collected data, made some mistakes,
and, based on the lessons we learned, provided
recommendations to industry on how to improve designs of IES equipment.
A city's night-time energy use.
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A valuable recommendation was to install an airtight damper to isolate
the microturbine exhaust from the absorption chiller when the chiller
is not operating."
According to Bob DeVault, the highly instrumented CHP laboratory at
ORNL where he works was the first lab to test both a microturbine and
heat exchanger simultaneously and as a system over the whole range
of thermal conditions. Neither the microturbine vendor nor the heat
exchanger manufacturer is set up to conduct the types of tests that
ORNL can do.
The ORNL
research should help industry and DOE meet two goals by 2010. The
first goal is to double the amount of CHP capacity in the United
States, bringing it to 92 gigawatts of installed capacity. The
second goal is to build and install packaged systems with an energy
efficiency of at least 70% and a payback of 4 years or less—that
is, the amount of money saved by reduced demand for energy would cover
each system's additional capital cost in no more than 4 years.
According
to Dave Stinton, a manager of ORNL's Distributed
Energy Program, ORNL researchers have been developing advanced
materials to increase the efficiency of engines and turbines. They
have been evaluating the longevity of continuous fiber-reinforced
ceramic composites used in combustor liners and the oxide coatings
that protect these liners against oxidation
in industrial gas turbines built by Solar Turbines, Inc.
"We also conduct research on natural-gas-burning reciprocating
engines in collaboration with Caterpillar, Cummins, and Waukesha," Stinton
says. "Reciprocating engines are more efficient than gas turbines
and microturbines but have higher emissions of nitrogen oxides (NOx).
Our challenge has been to reduce emissions from the engine by an order
of magnitude and increase the efficiency to 50%."
"We have
developed a NOx trap that reduces the NOx emissions from lean-burn
engines to 0.1 g/hp/hr, meeting the goal of the program for 2010, " says
Tim Theiss, manager of ORNL's Advanced Reciprocating Engine
Systems Program.
ORNL researchers
are working in partnership with industry to extend
the life of spark plugs for natural gas-fired reciprocating
engines to 8000 hours, delaying the need for maintenance from
several months to one year. Laboratory staff who collaborate
with Federal Mogul, makers of Champion spark plugs, believe
that use of alternative materials will result in a cheaper,
more durable, corrosion-resistant spark plug.
ORNL is
now working with Capstone, UTC, and General Electric with a goal
of raising the efficiency of microturbines from 27% to 40%. "The ability to operate a microturbine at higher and higher
temperatures will lead to higher efficiencies,
but this operating level will be possible only with the right materials," says
ORNL's Edgar Lara-Curzio. "We have been screening and evaluating
materials for a microturbine component that is responsible for one
half of the microturbine's efficiency. We selected an innovative approach for screening
and evaluating candidate materials that should enable us to
identify the right materials for the hot section and recuperator
of an advanced microturbine."
"What
we are trying to do in the short term is use better metals to get the
hot section up to an intermediate temperature
range," Stinton says.
ORNL researchers will evaluate integrated energy system projects at
Wal-Mart stores.
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"Capstone's beta version
of a metal microturbine demonstrates 34% efficiency.
"We are looking
at silicon nitride for a microturbine's rotor, the hottest part
of this machine. Use of a ceramic rotor would raise the turbine inlet
temperature by several hundred degrees Celsius, boosting the microturbine's
efficiency to nearly 40%."
As a result
of the latest solicitation, ORNL is involved in IES projects not
only with hotel and supermarket chains but also with Wal-Mart stores
and McDonald's restaurants.
These projects offer potential for reliable, as well as efficient,
energy sources. In 2003 a new IES protected the critical circuits of
the Hilton Garden Inn in Chesterton, Indiana, when a violent thunderstorm
caused a four-hour electrical outage in the area. The hotel's
guests enjoyed normal operations including a hot lunch during
the outage.
"These
partnerships are exciting because they should enable a new technology
to be replicated nationwide," Stinton says. "IES units
already are cost effective in many parts of the United States. We are
very enthusiastic about the potential of this technology as one solution
to America's energy challenge."
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