Home
Concentrating
photovoltaic (CPV) technology is a hybrid of 2 familiar solar energy
concepts. The most widely recognized and developed concentrating solar
energy technologies use mirrors to concentrate the sun’s heat, on a
solar power plant (SPP) scale. The familiar rooftop solar systems use
solar photovoltaic (PV) panels to transform the sun’s light into
electricity.
The hybrid concentrating PV concept uses a small,
highly efficient mirror-lens system to concentrate the sun’s light on a
small, highly efficient PV panel and transform the sun’s light into
electricity with a very high degree of efficiency.
CPV is a new
variation that could improve the cost-effectiveness of solar power
plants but has yet to prove itself. A few companies, including
SolFocus, are working to perfect and demonstrate it.
click to enlarge
The SolFocus
CPV system directs sunlight onto an optical rod with a 2-mirrored
system. The rod acts as a lens to concentrate and focus the light "of
500 suns" on a tiny, 1-square centimeter PV cell. A panel consists of
several of these units. A row of panels is mounted on a tracking rack
that rotates with the sun across the sky, maximizing the light hitting
the panels.
Emcore Corp.
uses powerful lenses that focus a 500-sun concentration of light onto a
highly efficient multi-junction (thin film) solar cell. The
“multi-junction” architecture makes the cell capable of capturing more
of the light concentrated on it.
Semprius Solar
is using a similar concept but concentrates "1,000 suns" and is working
to make the its micro-transfer thin film manufacturing technology that
simulates a printing process less expensive so the price of the CPV
panels will be more affordable and, therefore, cost effective.
click to enlarge
Cost
remains CPV’s obstacle. It is still more expensive than rooftop silicon
solar panels or thin film solar panels, though SolFocus says it is on
track to match the other panel materials by 2010 and be cheaper by
2011. A recent report from Spain estimated CPV will reach grid parity,
the cost for electricity production that matches the cost of
traditional generation sources, between 2011 and 2015. That is the same
time frame in which the other solar panel materials manufacturers
anticipate reaching grid parity.
To bring its costs down, CPV
will have to get a bigger part of the market. And, of course, to get a
bigger part of the market it will have to bring its costs down.
Estimates put present CPV investment at ~$1 billion worldwide, which
represents a few small-scale projects, mostly in Europe.
SolFocus
has done a half-megawatt installation in Spain and is doing a
10-meagawatt installation in Greece but only has ~10 kilowatts
installed domestically. Emcore has installed a megawatt of CPV in Spain
but less than 500 kilowatts in the U.S.
SolFocus panels. (click to enlarge)
Advocacy
group CPV Consortium wants federal buy-in. Federal labs and grants have
pushed CPV R&D. Now the CPV industry wants the government to
provide loan guarantees or installation money for demonstration
projects on federal lands.
As many as a dozen companies, from
start-ups to a 50-year veteran solar panel manufacturer Sharp Corp, are
experimenting with a variety of mirrors, lenses, dishes, troughs and
carousels to maximize reliability, increase the delivery of sunlight to
ever-smaller, ever more efficient PV cells or cut production costs.
Semprius panels. (click to enlarge)
COMMENTARY
Because
CPV panels use less silicon, they are – like solar thin film – less
expensive. Also like thin film, CPV is better suited for use in larger,
solar power plant (SPP) arrays than for small, rooftop systems where
silicon panels remain the standard because of their durability and lack
of need for maintenance.
The competition will be between CPV,
which uses the sun’s light, and SPP technologies that use large flat
mirrors to concentrate the sun’s heat on a solar power tower or
parabolic trough mirrors to concentrate the sun’s heat on flowing
liquid.
click to enlarge
Because
solar power plants are built in intensely hot desert areas, CPV’s most
immediate advantage over SPP mirror technologies is that it uses
significantly less water. The SolFocus technology uses 4 gallons of
water per megawatt-hour of electricity produced, mostly to keep the
panels clean of dust. The widely-used solar power plan technologies
reportedly use 850 gallons of water per megawatt-hour.
CPV
systems are also largely made of aluminum and glass and are, therefore,
97% recyclable. The energy payback for all materials in a CPV system
may be as little as 6 months.
click to enlarge
Finally,
the modular configuration of CPV allows installations to be set up to
accommodate the space rather than dominating the space the way the
larger plants do. SolFocus says its panels can even be set up to allow
the growing of crops or grazing of animals in between.
Because
CPV is modular, it lends itself to SPP installations of any size
whereas the economics of the big-mirror SPP technologies make them more
cost-effective at larger sizes. Perhaps, for the time being, CPV might
work better as 1-to-10 megawatt supplementary installations, such as
those currently being tried at natural gas plants, while the
50-megawatt and up solar power tower and parabolic trough mirror
systems would be the cost-effective choice for stand-alone power plants.
click to enlarge
QUOTES
-
Nancy Hartsoch, vice president of marketing, SolFocus and director, CPV
Consortium trade group: "In a lot of ways, it's merging the advantages
of photovoltaic technology with the efficiency and ability to capture
more sunlight that you get with concentrated…You're basically focusing
650 suns onto that cell, so you're able to use a very, very small
amount of photovoltaic material to capture a tremendous amount of
sunlight and then convert it at very high efficiency."
- Brad
Collins, director, American Solar Energy Society (ASES): "I think
there's a huge space [for CPV technology]…Solar deployment on a utility
scale will explode in the next five years…It doesn't compete with
traditional PV. The applications are different…One's going to be a
power plant, and one is a distributed resource. It's not comparing
apples to apples."
- Hartsoch, SolFocus and CPV Consortium: "There
are the big concentrating solar power plants -- the solar thermal stuff
that's been around a long time -- and they use mirrors as we do in a
different way…I guess you could say [CPV’s water use is] a drop in the
bucket [compared to that]…"
click to enlarge
-
Sarah Kurtz, CPV researcher, National Renewable Energy Laboratory
(NREL) of the U.S. Department of Energy (DOE): "When compared with
solar thermal approaches, CPV provides a qualitatively different
approach, typically with lower water usage, greater flexibility in size
of installation and the ability to respond more quickly when the sun
returns on a cloudy day…"
- Hartsoch, SolFocus and CPV Consortium:
"The battle for a new technology like this, the challenge it faces, is
the reason it's good…What it brings is high efficiency, low carbon
footprint, all those things. What comes with it is the risk of new
technology…You're now talking about small grants ... to develop new
technologies and some showcasing, but if you want to take this
big-scale, there's one more hurdle…What can you do to help us assure
that it's safe to deploy?"
- Anita Balachandra, senior vice
president, TechVision21: "So many of these technologies have originated
in the United States, but where they've really flourished and been
taken to scale has been outside of the United States…They've drawn
them, and long term, we lose competitive advantage."
click to enlarge
-
Brian Gibson, director of business development, Emcore: "We are
pursuing larger projects at this point in time, but as with any newer
technology, there's going to be reluctance of the financial institution
to take risk…It's difficult to get anything sizable financed. We are
looking at some 10- and 20-megawatt projects, but from a practical
standpoint, you've got to do some 1- to 3-megawatt projects before
anyone will finance you."
- Kurtz, NREL: "In the last 10 years, the
solar industry has mushroomed, and the CPV industry is now growing
rapidly…With the overall PV market growing in the gigawatt range, CPV
has an opportunity to enter the market with production of tens or
hundreds of megawatts per year... This is significant because CPV is
unlikely to achieve low costs when manufacturing at less than tens of
megawatts per year."
Solar Companies Merge Technologies in Bid for Utility-Scale Production
Katie Howell, July 7, 2009 (NY Times)
posted by Herman K. Trabish
