http://sustainableskies.org/sas-2019-larry-cooke-novasolix/
SAS 2019: Larry Cooke and
NovaSolix
DEAN SIGLER
Laurence H. (Larry)
Cooke, Chief Technology Officer for NovaSolix, a California-based
solar panel manufacturer, discussed a way to make what are
essentially radio waves into efficient, inexpensive solar power. His
biography includes this indicator of a productive life. “Larry “Cooke has
written one book, multiple papers and have over 100 granted US patents. Cooke
is currently CTO and Chairman of NovaSolix, a revolutionary Carbon Nanotube
Rectenna array based solar cell start-up.”
NovaSolix separates
its approach to capturing solar energy from the “traditional” solar cell, solar
panel method.
“The Old Way”
Thoughtco.com says, “Any
device that directly converts the energy in light into electrical energy
through the process of photovoltaics is a solar cell.” Such devices have
a longer history than your editor anticipated. Antoine-Cesar Becquerel
noted a voltage drop when light fell on a solid electrode in an electrolyte
solution. It took until 1839 for Charles Fritt to develop the first
genuine solar cell, by coating semiconducting selenium with an extremely thin
layer of gold.
In 1941, Russel Ohl
created the silicon solar cell, the predecessor of today’s rooftop
panels. His cell achieved less than one percent efficiency, though.
According to Thoughtco.com, “In 1954, three American researchers,
Gerald Pearson, Calvin Fuller, and Daryl Chapin, designed a silicon solar cell
capable of a six percent energy conversion efficiency with direct
sunlight.” Bell Laboratories followed with early mass production of such
cells, installing a Bell Solar Battery in a telephone carrier system on October
4, 1955.
current solar cell
efficiency. National Renewable Energy Laboratory
Most panels on
rooftops today are still only about 15 to 20-percent efficient and even those
on Solar Impulse were rated at around 22.7-percent.
Novasolix explains
this lack of efficiency. “Today’s common solar technology is based upon
the photovoltaic effect that was first shown in 1839. Photovoltaic solar cells
operate at the quantum level. A photon approaches an electron. If the photon
has the required minimum energy, it can be absorbed by the electron that
excites the electron (moving it to a higher energy state). Capturing the
resulting diffused electrons creates an electric current.
“The key with PV
technology is that not just any photon can excite an electron. The photon needs
a minimum amount of energy . That means that lower energy infrared light (about
40% of all solar energy to hit the surface of the Earth) will not generate
electricity. Furthermore, only certain frequencies of light (specific colors)
correspond to the energy states required to knock an electron free. And, of
course, a weak light cannot excite an electron to the next higher energy state,
so dim lights produce zero power in PV cells.”
The NovaSolix Way
Larry’s description of
NovaSolix’s technology shows a very different approach. “We are
developing rectifying antenna based solar devices used to capture solar energy
with an initial target of twice the efficiency at 20% of the cost and 20% of
the weight per watt of current single junction solar cells. We are using
multi-wall carbon nanotubes (CNTs) grown in arrays of tiny antennas that are
suspended between Aluminum ground/contact lines.”
All solar energy up to
this point requires that photons push electrons to a higher energy state.
Novalsolix uses microscopic antennas to capture the light energy “as very high
frequency alternating current and then use a diode to convert the alternating
current into usable direct current. Each carbon nanotube antenna is about
one micron (1/10,000,000th of a meter) long with a diode on one
end that operates at frequencies approaching 1 PHz or one quadrillion cycles
per second. Compare that to AM radio, which operates at around one
million cycles per second. AM antennas are about a meter long.
Using LCD (liquid
crystal display) flat-panel TV processing equipment, NovaSolix can mass produce
rectenna solar cells at low cost
Because NovaSolix collectors
place “roughly one million tiny radio receivers per square inch, they are able
to retrieve frequencies “from low infrared through visible light and up into
the ultraviolet.” Gathering the full spectrum enables conversion of weak
light to small amounts of power. A currently real 40-percent efficiency
with a theoretical limit of 90 percent enables smaller, lighter panels to
generate 400 Watts per square meter to 900 Watts per square meter.
The blue represents
modern solar modules conversion ranges, the light green represents a working
prototype by NovaSolix, and the dark green (plus areas under) is the goal.
Yellow and grey represent potential at sea level and in space. Source: PV magazine
Revised manufacturing
techniques using existing tooling will produce cells at very low cost and which
weigh less while bringing flexibility that will allow their use on curved
aircraft surfaces.
The NovaSolix approach
places roughly one trillion tiny radio receivers (rectennas) per square inch.
Unlike PV cells, the NS cells are compatible with a wide range of
frequencies from low infrared through visible light and up into the
ultraviolet. Furthermore, the NS cells are able to convert weak light to small
amounts of power. The theoretical limit on efficiency of NS cells is roughly
90% or three times the energy of a PV cell. Initial NS cells will be roughly
40% efficient, producing roughly 400 watts/square meter. Finally, due to the
different underlying manufacturing process, NS cells are cheaper and lighter
weight than PV cells while also being flexible.
Solar Transportation
Cooke suggested a
Tesla with NovaSolix cells covering its surfaces could recharge the equivalent
of an additional 16 miles of range per hour. The firm’s web site claims
that would be sufficient to recharge the batteris of 68-percent of all
commuters in the U. S., with one hour’s car-top recharging enough for a one-way
commute. 88 percent of all commuters would not need to recharge their
cars with four hours of sunlight.
Four hours driving at
60 mph would take the car 240 miles and add 64 miles of solar charging.
One tricky calculation adds 16 miles for the hour saved by not having to stop
to recharge. Even the half-hour spent at a Tesla Supercharger would add
eight miles of capacity.
Sono Motors is a separate company that
makes an electric car with built-in solar power supplemental charging. A sunny
day can provide 18 miles of driving range on a 24% efficient solar cell. If
NovaSolix increased solar cell efficiency to 90% then one day of sunlight
driving would be 67 miles.
NovaSolix suggest, “A
similar analysis shows that by covering a railroad boxcar with NS cells, the
sun would be capable of powering the refrigeration system and still have power
left over for propulsion.” Even better, perhaps, a Tesla or Freighliner
eCascadia with a semi-trailer covered with NS cells might be literally
unstoppable in range.
Aerospace
NovaSolix’s initial
application seems to be aimed at satellites and drone aircraft. The
company notes, “Modern communications satellites are power constrained. Even
with huge banks of PV cells, few modern satellites have more than 4000 or 5000
watt power envelopes. Using NS cells, the same weight of cells could result in
a tenfold increase in power budget. Furthermore, since NS cells can convert
infrared radiation (normally seen as heat) into power, the satellites will have
less difficulty staying cool in direct sunlight.”
The technology would
be applicable to high-altitude, long-endurance craft such as those used for
surveillance missions. Again, the light weight and high power output
would enable essentially endless missions.
We can wish Larry
Cooke and NovaSolix the best of fortunes. Their success be a game changer
in electric aircraft.
Self-Assembled
Carbon Nanotube Antennas for Solar Power Revolution
NovaSolix has invented a self-assembling antenna array solar
cell which will be 2-4
times more efficient at a less than one-tenth the cost per watt of existing
solar.
NovaSolix claims to have demonstrated a proof of concept to
third parties that has touched 43% efficiency. That’d suggest a 72 cell solar
module near 860 watts, with a 90% solar cell pushing 1700 watts.
They could buy used manufacturing hardware and retrofit them in
the early stages of growth. The first manufacturing lines could cost $4.1
million, and would initially produce ~45% efficient modules, at a clip of
20MW/year with a proposed price of 10¢/W. At full efficiency, costs are cut in
half and volumes per year doubled.
Sono
Motors is a separate company that makes an electric car with built-in solar
power supplemental charging. A sunny day can provide 18 miles of
driving range on a 24% efficient solar cell. If NovaSolix increased
solar cell efficiency to 90% then one day of sunlight driving would be
67 miles.
https://www.eejournal.com/article/sunshine-changing-the-world/
Sunshine Changing the World
May 31, 2017
by Kevin Morris
As an electronics
editor, I am constantly being briefed on new technologies. Often, the presenter
struggles to establish a framework for the innovation being described, trying
to make a case for the big-picture importance of what they’re doing. Seldom am
I left with a feeling that I am learning about an engineering development that
could truly change the world.
This, however, was one
of those rare times.
Before we descend into
the fascinating world of nanotubes, light-wavelength antennas, nano-scale
rectifiers, and commodity manufacturing processes, let’s get the punchline out
of the way. NovaSolix is developing a technology that has the potential to
quadruple the output of solar energy panels, while significantly reducing their
cost and weight. Let that sink in for a bit…
Silicon photovoltaic
(PV) cells are already far into the commodity column. Massive factories are
turning out panels by the gazillions, and the world is busily taking advantage
of the low-cost energy source by plastering them across virtually any surface
we can find that points toward the sun. The percentage of the world’s energy
supplied by solar power is ramping up at a steady pace.
Current solar
technology has its weaknesses, however. While the energy production itself is
environmentally friendly, the creation of the panels generally is not. And the
efficiency of today’s panels is fairly low – with generally less than 30% of
the available solar energy being converted into usable power. The majority of
the energy is either reflected or converted into waste heat. That low
efficiency means that solar power is impractical for many applications where
the exposed area is limited. Solar vehicles, for example, are generally not
feasible because there just isn’t enough radiated energy striking the exposed
surfaces to provide the power required for operation, particularly given the
relatively low efficiency of solar conversion.
As all of us working
in electronics know, light accounts for only a small part of the
electromagnetic spectrum. SEM Power says those
who have worked with solar energy also understand that only a small portion of
the light spectrum can be converted to energy by silicon PV cells. The
remaining spectrum is either reflected, or absorbed and converted into waste
heat. This accounts for the low efficiency of today’s solar panels.
Now, let’s take a
little trip down memory lane – back to what was possibly the first electronic
project many of us ever did. Yep, a crystal radio. The crystal radio is a
shockingly simple contraption consisting of an antenna and a crystal (often a
germanium diode) that acts as a bandpass filter and rectifier. The circuit is
tuned to the desired frequency, and the RF energy is captured and does the
useful work of driving a speaker or earphone coil – producing sound. Crystal
radios gather their power directly from the radiated energy of the radio
transmission – they require no external power to operate.
If we could have an
antenna/rectifier setup tuned to the frequencies of solar radiation, we could
use the same idea to harvest energy from light. Unfortunately, due to the very
short wavelengths involved, we’d need some unusually tiny antennas – about a
micron long, in fact – and that means that we’re talking nanoscale. Picture a
trillion antennas in a square inch.
This is what NovaSolix
is up to.
NovaSolix is a silicon
valley startup developing a process to manufacture solar panels that use carbon
nanotubes as antennas – combined with nanoscale rectifiers – to generate power
from a much broader swath of the solar energy spectrum than conventional PV cells.
The company claims that 80-90% efficiency may be possible. They are also
working to develop a process to manufacture the panels on a substrate of glass,
thus dramatically reducing the cost compared with silicon-based PV technology.
If the company is
successful in hitting their efficiency and cost targets, they could quite
literally change the world. The economics and practicality of solar versus
other forms of energy is already at a tipping point, so tiny changes in the
cost-per-watt of deploying solar can have massive effects on the economics of
energy. Changes of the magnitude NovaSolix envisions could slam a brick on that
balance scale, completely transforming the energy landscape (and wiping out
entire major industries in the process).
In order to harness
the full spectrum of visible and infrared light, we need antennas of varying
lengths. NovaSolix is working to create just the right mix of manufacturing
variation in their carbon nanotubes to give the optimal distribution of antenna
lengths. The carbon nanotube antennas are “grown” between electrical contacts,
and they create diodes at the interface point. Each successful nanotube pair
creates an antenna and a full-wave rectifier. NovaSolix has now successfully
created demo wafers, and the IV curve of the resulting devices is interesting.
Conventional PV cells have a fairly flat IV curve, with current remaining
relatively constant and voltage increasing proportional to output. The nanotube
antennas, however, produce a more linear IV curve, which should allow for a
simpler controller than conventional PV cells, as well as greater immunity to
partial shading effects.
NovaSolix is currently
doing wafer fabrication in the Stanford Nanofabrication Facility and growing
carbon nanotubes in their own labs. Their plan is to work toward a small-volume
production capability with a “boutique” version of the technology aimed at
specialty markets where power-per-area is the critical factor. This includes
portable applications such as solar aircraft, wearables, and satellites. This
production will be done using primarily older-generation semi-automated IC
fabrication equipment. NovaSolix can see bringing the cost per watt down from
$10 to around $1 with this approach.
The exciting part
begins with their plans for higher-volume roll-to-roll manufacturing, however.
NovaSolix intends to move to a rolled-glass base and to replace the masking
steps with drum presses and etching. Using these materials and process changes,
the company thinks they can get material costs down to under 1 cent per watt,
significantly reduce manufacturing costs, and increase production volumes. The
finished panel cost could drop to as low as 3 cents per watt – resulting in a
panel that’s 2x the power at 1/5 the cost of a silicon PV cell, a net 90%
reduction in cost-per-watt from today’s ~32 cents for silicon PV.
There are a number of
obstacles between NovaSolix and this vision. Like any startup, they face
funding challenges in ramping up their business. Their technology remains
unproven, and numerous unforeseen technical and manufacturing obstacles almost
certainly lie in their path. Getting nanotubes to grow reliably with the right
distribution of lengths and with acceptable yields is still foo-foo magic
stuff. While the ideas behind the march to low-cost, high-volume production are
all well established, using them in the particular combination NovaSolix plans
is largely uncharted territory. If the company can get past these barriers,
however, nanoscale solar antenna arrays could be one of those
once-in-a-lifetime breakthroughs that cause massively disruptive change. It
will be interesting to watch.
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