Making the Most of Waste
Energy
Environment and Resource
Management
Originating Technology/
NASA Contribution
The Thermo-Mechanical Systems Branch at NASA’s
Glenn Research Center is responsible for planning
and conducting research efforts to advance thermal
systems for space, aerospace, and non-aerospace
applications. Technological areas pertain to solar
and thermal energy conversion. For example, thermo-mechanical
systems researchers work with gas (Stirling) and
liquid/vapor (Rankine) systems that convert thermal
energy to electrical power, as well as solar dynamic
power systems that concentrate sunlight to electrical
power.
The branch’s development of new solar and thermal
energy technologies is propelling NASA’s missions
deep into unfamiliar territories of space. Solar
dynamic power systems are actively improving the
health of orbiting satellites, giving them longer
life and a stronger radiation tolerance, thus,
creating less need for on-orbit maintenance. For
future missions, NASA may probe even deeper into
the mysterious cosmos, with the adoption of highly
efficient thermal energy converters that have the
potential to serve as the source of onboard electrical
power for satellites and spacecraft. Research indicates
that these thermal converters can deliver up to
5 times as much power as radioisotope thermoelectric
generators in use today, for the same amount of
radioisotope.
On Earth, energy-converting technologies associated
with NASA’s Thermo-Mechanical Systems Branch are
being used to recover and transform low-temperature
waste heat into usable electric power, with a helping
hand from NASA.
Partnership
In 2003, Mount Prospect, Illinois-based Unitel
Technologies, Inc., approached NASA with an idea
for an advanced energy recovery cycle that it believed
could cost-efficiently convert low-level thermal
energy sources from previously untapped resources—such
as hot gas exhausted from power plants—into usable
electric power.
According to Unitel Technologies, each and every
day, all around the world, an incalculable amount
of energy is wasted and literally blown into the
atmosphere through power plant smokestacks and
industrial and commercial heating systems. Billions
of energy units are additionally carried away by
the cooling water and air that are used in many
of the related processes, the company added.
![Artist’s depiction of space flight using solar thermal propulsion](Images/Page_080_Image_0001.jpg) |
Harnessing
the Sun’s energy through solar thermal propulsion
could propel vehicles through space by significantly
reducing weight, complexity, and cost while boosting
performance over current conventional upper stages.
Pictured is an artist’s conception of space flight
using solar thermal propulsion. |
“Power plants, be they stationary or vehicle, are
typically not very good at squeezing the last few
BTUs (British thermal units—used to measure heat
created by the burning of any material) out of
their fuel source,” noted Serge Randhava, president
of Unitel Technologies. “Much of this lost potential
is simply blown up the stack or out of exhaust
pipes, in the form of low-level waste heat. The
volumes of this thermal energy are unfathomably
large, but the temperatures are low, and conversion
of low-level heat sources into usable electric
power can be difficult,” he added.
The company’s proposal to NASA aimed to address
this issue. As it turned out, however, the Space
Agency already possessed some expertise in this
area. Researchers from Glenn’s Thermo-Mechanical
Systems Branch developed thermodynamic-analysis
software to aid in the recovery of the exhaust
heat, or waste heat, from the Rankine-cycle engines
of M1 Abrams military battle tanks. The two parties
agreed to enter into a partnership in which their
knowledge would be shared to advance thermal energy
recovery efforts throughout industry.
Unitel Technologies received a NASA grant to design
a prototype waste heat recovery system called NEOGEN.
The goal was to achieve a nominal energy-savings
gain of approximately 20 percent over the recuperated
binary Rankine cycle. The work was carried out
with assistance from the Glenn researchers and
engineers from Creare, Inc., who aided in the development
of the thermodynamic-analysis software. Moreover,
an award from the NASA Illinois Commercialization
Center supported NASA’s thermodynamic-efficiency
analyses
of NEOGEN.
With regard to the prototype’s design, the idea
was to create a system that could use a unique
absorption cycle to tap into waste heat streams
of 125 °C (257 °F) to
400 °C (752 °F). Using the thermodynamic-analysis
software, Glenn researchers modeled the cycle efficiencies,
optimized the heat exchanger design, and provided
operating cost data. In addition, NEOGEN performance
was benchmarked against related systems that NASA
worked with in the past.
The results of this cooperative research effort
were successful. The three parties took a concept
for a new heat recovery cycle, with a unique and
flexible working solution, all the way to demonstration-ready
design.
“Working with NASA let us dramatically short-circuit
our development program,” said Randhava. “We were
able to go directly from concept to prototype design
phase without the need for endless bench and pilot
scale experiments.”
On top of the time savings, the partnership with
Glenn saved Unitel Technologies over $250,000 in
developmental costs.
Product Outcome
While a heat recovery system able to operate in
the lower spectrum of waste temperatures opens
up an enormous number of applications for exploitation,
Unitel, with continued guidance and resource-support
from NASA, decided to tiptoe into commercialization
with a single focus on marine power plants, where
everyday, just one single large ship can generate
billions of BTUs in the form of low-level waste
heat.
![Heat recovery system schematic](Images/Page_081_Image_0001.jpg) |
This
system schematic was developed by Unitel Technologies,
Inc., Creare, Inc., and Glenn Research Center.
The ensuing waste heat recovery unit features
a twin-turbo generator and a twin-recuperator
configuration that give it great flexibility
in heat-source harvesting. |
According to the company, marine power plants have
a few unique characteristics that make them well-suited
for waste heat recovery, and a few which make them
a challenge. One advantage is that there are vast,
cold sinks sloshing beneath every marine power
plant outside of dry dock. Unitel, NASA, and Creare
designed the NEOGEN system based on a 27 °C (81
°F) cold sink—equivalent to oceanic temperatures.
On the challenging side, there is limited space
for a recovery unit to operate within the power
plant of a marine vessel, plus, there are many
safety considerations that come with operating
such machinery on
a ship.
“If the NEOGEN system can help us harvest even
a modest fraction of this energy stream, we can
save a lot
of fuel and help our environment at the same time,”
claimed Randhava.
Beyond the initial marine power plant applications,
the company plans to use its system to recover
energy from other industrial plants, as well as
commercial plants, electric utility facilities,
diesel engines, and gas turbines. The company is
looking to gain a foothold in these areas that
it said were largely disregarded until about 4
years ago, when the price of crude oil started
its upward climb.
“Most of the waste heat recovery strategies in
use today are directed at high-temperature streams,
usually over 400 °C (752 °F). The low-temperature
spectrum has been ignored because the driving economic
pressures were simply not there,” said Randhava.
“The decision has now become highly significant,
given the fact that the price of crude oil is more
than $60 per barrel. Every BTU of energy that can
be saved means money in the bank, more so now than
ever.”
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