Raytheon Technology Today 2011 Issue 1

Feature
Continued from page 19
design to fully meet the objective of maintaining
the PV cell array less than 50 degrees
Celsius during full sun concentration.
Next Steps
The next steps in the team’s development
effort are:
1. Demonstrate that by reducing the resistivity
of the electrical grid fingers on the
surface of the PV cells (by increasing their
number by approximately 40 percent),
system efficiency can be increased by an
additional few percent absolute (even
though photon reflections from the surface
of the PV cells will be increased),
which is achievable with this design,
given the unique ability to recycle reflected
photons.
2. Develop a full-size, 40-kilowatt prototype
design that meets the DTUPC goal of less
than $2 per watt installed with an LCOE
of less than 6 cents per kilowatt hour.
3. Develop a smaller scale, mobile PCU that
could be used for U.S. Dept. of Defense
Forward Operating Base Field applications.
As more advanced multi-junction PV cells are
developed — progressing from today’s 39
percent efficient triple junction cells to a target
of 58 percent efficient six junction cells
— system efficiencies using our photon recycling
concept should increase from 33 to 40
percent, with the successful development of
45 percent efficient four- and five-junction
cells. The ultimate goal is 50 percent system
efficiency using six-junction PV cells, as
they become commercially available. These
Figure 4. Demo PCU with 21 mirror segments
20 2011 ISSUE 1 RAYTHEON TECHNOLOGY TODAY
Solar Power
advanced PV cells can easily be integrated
into Raytheon’s PVCC, enabling achievement
of these increased system efficiencies.
But even with these breakthroughs, over
50 percent of the energy will be lost, mainly
through dissipated heat. To convert more
of the available solar energy to electricity,
Raytheon is investigating the use of thermoelectric
devices to complement the PVCC
PCU concept. In addition, the University of
Arizona is developing concepts that can use
the low-energy content, warm water (possibly
in the range of 50 degrees Celsius) from
our closed-loop cooling system to purify
brackish water and even desalinize sea water
into drinking water, which would further
increase the cost effectiveness of this solar
energy concept.
The major benefits of this unique solar energy
power conversion system are that it:
• Results in higher overall system conversion
efficiency, compared with non-photon
recycling HCPV systems.
• Eliminates the use of boilers to generate
steam and large turbines to generate electricity,
resulting in far fewer moving parts
than solar thermal systems, significantly
reducing maintenance costs and increasing
system reliability.
• Dramatically reduces the use of water for
cooling and cleaning of mirrors, which is
critical when operating in the arid desert
Southwest.
• Eliminates emissions of carbon dioxide
from the power generation process.
Solar energy is rapidly becoming costcompetitive
with fossil fuel power plants, in
particular coal-burning plants. In 1990, solar
energy power generation costs were in the
55 to 65 cents per kilowatt hour range, and
today the cost has dropped below 11 to 13
cents per kilowatt hour — the price range
for many of today’s typical utility power
purchase agreement contracts. An HCPV
solar electric power plant of 240 megawatts
(typical power plant size) would consist of
approximately 6,000 solar electric PCUs
of 40 kilowatts each. Today such a power
plant could support a minimum of 60,000
homes. At rate production and a price of $2
per watt installed, a contract to supply and
install the PCUs for a 240-megawatt plant
would be about $500 million. •
John P. Waszczak, Steven L. Allen
ENGINEERING PROFILE
Kevin P.
Bowen
Engineering
Fellow, IDS
Kevin Bowen
has 35 years
of experience
in systems
engineering
development
on manned
and unmanned
maritime surface and undersea vehicles, including
15 years as a field engineer. He is currently
applying that experience to develop a high
energy, high power, low cost, environmentally
friendly undersea power and propulsion system
in order to extend endurance, increase speed
and lower the cost of undersea vehicle systems.
He is also a key contributor to the Power Cell
Enterprise Campaign. For the past two years,
he has been investigating fuel cell, battery and
external combustion technology.
With all of his work, he aims to apply his extensive
knowledge to assuring mission success
— now and in the future. “An affordable longendurance
energy system will enable a host of
new undersea missions,” he said.
Since starting at Raytheon, Bowen has been
program manager for unmanned surface
vehicle (USV) technology development and
diver detection/intervention for port security;
chief engineer for unmanned underwater vehicle
(UUV) Propulsion Systems and riverine craft
combat system architectures; technical lead for
UUVs; and lead systems engineer on the MK 30
ASW training target system.
Bowen enjoys the variety of challenges he
encounters in his job, and thoroughly immerses
himself in all of his projects. Bowen advises others
to be creative and work hard. When others
ask him how he gets the fun jobs, he responds,
“I don’t get jobs; I make them up.”
Bowen is a member of the Association for
Unmanned Vehicle Systems International, the
National Defense Industrial Association, and the
ASTM Maritime Vehicle Standards Committee,
for which he has served as vice chairman, USV
maritime regulations.