By Tuan Nguyen
Posting in Design
Aidan Dwyer's tree-inspired array for solar panels had the web buzzing, but not everyone believes it's more efficient.
Ahhh the internet. One minute you're the latest media sensation with a groundbreaking idea. The next minute you're the latest over-hyped media sensation with the not-so-groundbreaking idea. This is the circumstance that Aidan Dwyer, a 13-year-old boy, may have unwillingly found himself in.
Last week, the web was abuzz with news that the 7th grader from New York had developed a new design layout for solar cells. After completing an experiment, he concluded that his oak tree-inspired model may improve efficiency by an unheard of 50 percent over conventional arrays. He came up with the idea during a winter hiking trip in the Catskill Mountains, where he noticed that the tree branches grew in a spiral pattern resembling the Fibonacci numbers, a mathematical sequence often found in the structure of plants.
It was the kind of story that fans of science can't help but be enthralled with. A precocious youngster has a nature-inspired "eureka!" moment, which may lead to a breakthrough that turns an entire multi-billion dollar industry on its head. If not quite made-for-Hollywood, it's definitely feel-good enough to garner him a Young Naturalist Award from the Museum of Natural History and for front page play on several popular news sites and blogs that obviously didn't hesitate to jump all over it.
But no sooner as word spread did a natural peer-review process started to kick in as some readers started poking holes in Dwyer's research. One blogger, however, took the scrutiny one step further, posting an entire explanation complete with rigorous scientific data and charts debunking his findings.
Writing on the capacity factor, an energy blog, the person wrote:
This is, I'm sad to say, clear nonsense. I'll take this in two parts: one, why his experiment is, unfortunately, completely broken (sorry again). Two, why the imagined result is impossible nonsense.
Most importantly, by mistake he did not measure power outputs from the solar cells. Instead he measured voltage, without a load attached ("open circuit"). They are barely related -- in solar cells, voltage is actually almost a constant, independent of power.
The actual power delivered by a solar cell is not linearly related to the open-circuit voltage; actually, as a semiconductor, it has a horribly nonlinear relationship.
Now I'm not a solar energy expert myself, but I found the writer's assessment of the theory to be quite convincing. So to get to the bottom of this brewing controversy, I got a hold of someone who has made it his life's work to make solar arrays more efficient and cost effective.
I spoke to Jan Kleissl, professor of environmental engineering at the University of California in San Diego, who, first and foremost, praised the youngster for doing a "amazing job" carrying out the experiment. Kleissl did, however, agree that the flaws pointed out by the blogger were on point because a measurement of the actual current would have shown it to be much lower.
"Using just the voltage to say a panel is more efficient at producing energy is similar to saying I have a fast car because I can drive from San Diego to Seattle," Kleissl said in a phone interview. "They can't be correlated like that."
While he conceded that Dwyer's arrangement offers a slight advantage over standard panel arrangements in the morning hours -- when a few of the panels would be in position to catch more sunlight -- he was quick to point out that a standard solar array would produce a lot more energy around noon and overall because the panels will be facing the sun more directly.
"People have this tendency to believe that nature is head of us and that if we replicate it, all of our problems will be solved," he says. "But we are really way ahead of nature."
To drive that point home, he says, for instance, that plants are only one percent efficient at converting sunlight into usable energy (sugar), while solar panel designs are now 20 percent efficient. He also added that since determining the best panel arrangement can be done simply by running various designs through a simulation, a much bigger help to the industry would be to fix other non-technical issues like simplifying the permitting process.
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And in case you're wondering what the most optimal way to position solar panels, his answer is "it depends."
For instance, placing them at a 180 degree angle works well in most parts of the world, but in regions like California the best angle is 10 degrees west of south due to the fact that morning clouds block much of sunshine until the afternoon hours. To help California residents predict how much solar energy can be generated from their own systems, Kleissl's research team has created a free solar density map that can be downloaded at http://solar.ucsd.edu/.
Rajiv Varma of Western Ontario University, who develops experimental solar power systems seconds Kleissl's assessment that Dwyer's solar array project won't improve the energy output of solar cells, though he sees a lot of promise in the young student's work.
"What I would really like is that this young man should not be discouraged by telling him that what he has proposed is wrong," Varma wrote in an email. "But instead help him getting in touch with researchers or academicians working in this area so that a bright mind is nurtured in this area."
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Aug 21, 2011
Many years ago a friend of mine came up with a similar new way of arranging solar panels to produce more power. He connected each solar cell individually to a rechargeable single rechargeable battery cell matching the voltage output of the solar cell, incorporating diode to prevent reverse voltage discharging into the cell during darkness or cloud cover. Each of these batteries was connected as solar cells would have been into a series circuit via a blocking reverse current diode to output the power into the load. The orientation of the panels was standard 180 degrees as this was in uk. The system was checked by a professor of electrical engineering from a uk university in secrecy as a full world patent was to be applied for should the system have greater efficiency than those in use at the time. the calculations under laboratory conditions proved that it was not, so project dropped. So now 25-30 years later with improved cell technology and battery types it might again prove to be feasible. So big companies out there the race is on to check it out, no patent problem as more than 16/25 years ago. Remember WHERE you read this and WHO pointed you in the right direction, but did not invent the idea. Hope the person who did is reading this. I will be able to prove you are/not if you say you are with more information that I have. I want the right person to get credit for the idea which is more important than the money in these cases if it works.
Why don't we make solar panels, the ones used to collect energy for a power grid, not a home, follow the sun. Or, do we already do that and I'm just uninformed, which is more likely the case. :) The boys experiment with branching the panels kinda shows a need for the panels to follow the sun, especially in a commercial array. If astronomical observatories can follow a point in the sky, solar panels should be able to use a portion of their collected energy to follow the sun.
Without further experimentation, it's hard to really say if what he came up with is actually viable and overall more stable. I would advise the family, and others, to make note of what the kid came up with, and watch out for ideas that seem to be the same, but with more research behind them to "prove" it, without a single nod in his direction. Jealousy can play dirty in the hands of "experts." Good job, I say again, to the kid, as science also has a habit of thinking inside the box only, until someone else thinks outside it, and has enough evidence to beat the rest over the head (and time for the rest to accept they were wrong, or lied.) I leave with a fictional anecdote that some may recognize as the work of the late Douglass Adams. Scientists were beating themselves over the head on trying to develop an infinite improbability drive, after they managed to design a finite improbability drive. Then someone came along (and was labeled a smart-*** for doing this) and decided to feed the improbability of an infinite improbability drive to the existing finite improbability drive... and voile, the infinite improbability drive was created. My point: Try everything, don't overlook the obvious, or possible solutions outside of the box that science dictates... You never know what you'll learn.
and you will see that while a FEW of the panels will always be in "optimum" orientation, NONE of the others will be so. They will be out by a few degrees, to as much as 180 degrees (assuming that the tree does NOT aim any panels to the unsunny side of the sky -- north). In other words, the situation is the same as if it they were mounted on a cone, with a surface following the "normal" (perpendicular) of the sun's track. It should be evident, that MORE cells will be MORE out of the normal at any moment, than would be with a rigid mounted, average-orientation mount. Indeed, many of the cells will be out of the sunlight completely. That said, I still give kudos to the young visionary. MOST successful scientists started out with similar innocently half-complete ideas. What a scientific education does, is fill in the holes, so you won't make so many mistakes going forward. And what an exposure to internet trolls does, is inform you that not everyone can see the genius involved even in good ideas that don't meet the eventual muster of reality. So ... GOOD JOB kid -- seriously. Keep it up, and no one will be able to hold you back! BTW, there are other ways to drive a mobile array, than using the panels' power to do so. For instance, if panels are expensive (which is current reality) then an aimed and selectively shielded array that heats a series of balanced, sealed water-flow bottles could change the balance of the whole setup, causing "energyless" rotation.
from article "To drive that point home, he says, for instance, that plants are only one percent efficient at converting sunlight into sugar, while solar panel designs are now 20 percent efficient." I'm green with envy, my solar panel is only 5% efficient at converting sunlight into sugar. :)
What's really a shame is that all the adults who saw this kid's development, were quick to jump on the bandwagon of praise and offerings of fame and fortune! It took a lone voice of reason...common sense really, to stand up and point out that the emperor was indeed not wearing any clothes. That's what's sad. Nobody took it upon themselves to study the design in detail and actually review what this kid did. Instead they all just nodded their heads in blank unison, agreeing with each other over their brilliance in recognizing this kid's brilliance! The same thing happened with cold fusion! Come on people..think a little, won't you?
The blogger who goes by the assumed name of uvdiv at Capacity Factor may have some valid points. I won't venture into the merits here, but I would like to plead for greater civility. I wouldn't be surprised if this young genius decides he would rather not hang around with spiteful people who take evident pleasure in proving how superior they are to a 12-year-old. OK, so the open circuit voltage is irrelevant, but Aidan Dwyer might be onto something with his self-similar current collection design, which emulates the fractal flow of tree sap. Fractal flow is nature's way of minimizing pressure drop. For more on area-preserving fractal networks, see http://hep.ucsb.edu/courses/ph6b_99/0111299sci-scaling.html
But I do know that Power comes from Voltage and Current. P = I x E. Now, the fact that he is able to get voltage (E) throughout the day rather than only during the afternoon when the sun is shining more directly on the cells, he is able to get more overall efficiency, though efficiency at any one part of the day will be lower than that 'afternoon sun' positioning. When you look at smaller plants like spouts, vines and flowers, quite often they rotate to follow the sun through the day in order to get the most light on a limited number of leaves. Big trees, like oaks, maples, etc. can't rotate like that, so they grow bigger and produce a lot more smaller elements to absorb any light that hits them, no matter the time of day. As a result, I can well see this 13-year-old's concept working on a large scale. After all, if you have to always re-aim your panels, you're using (wasting) some of that energy that you're capturing. On the other hand, if you don't rotate them, you're not capturing all the energy you could. Quite honestly, a fixed array is the most inefficient way to collect solar energy--merely the easiest. Now, by emulating a tree's leaf/branch pattern, you have a minimum of two panels working at maximum efficiency at any one time during the day. The total output power remains constant which completely stabilizes the power curve fed to the grid/batteries throughout the day. If you ask me, the kid's got the right of it and unless you can prove beyond a shadow of a doubt that a fixed, aimed array is more efficient on a day-long basis, maybe you should go back to school. If you look at the photo of the fixed array included with the article, you can see that not one panel is directly facing the sun and as such is not producing the maximum amount of power it could. Yes, as the sun moves westward the array will develop more power, but you end up with a sine curve that only produces peak power for a couple hours of the day where a parabolic array could produce roughly 70% of that peak power throughout the day. Yes, I do know something about electricity and electronics; it's been my career and the way I've earned my money for almost 40 years.
A hemispherical lens on top of a photo-voltaic cell would allow for all light in 180x180 degrees to be aimed directly at the cell. Do this for an entire array, and you boost efficiency by quite a bit.
Instead of mimicking trees, scale up shape-memory alloys that are attached to panels and act as low-power actuators to move the angle of panels based on the sun's position. You're now mimicking sunflowers and other plants that follow the sun.
I swear all you people suck, what we have here is a kid who has seen something in nature and done a fantastic job of connecting the dots that could eventually lead to a new research path or an OUT OF THE BOX idea, but NOOOOOOOO, because he didn't find a way to prove he could recreate the power of thew sun before breakfast and first period of school everybody here is bashing what he came up with. What are all 12 yr olds suppose to be Einstein and create the theory of relativity before you can just say hey, good job, this could help me come up with some new ideas of my own?, or give him a place to start his own line of research. Wow how cynical we have become. We can't even see when someone might have something worth investigating, cause we all know none of us adults have ever gotten it wrong. So I would like to close this rant up by saying to Aidan Dwyer, you have discovered something very important here, that is the spirit of research, look at a problem and try to find solutions, and I must say to that, GREAT JOB. Don't let these hack adults keep you from looking at the world with open eyes cause one day you may just find something that they cant see.
This is a matter of quantum electrodynamics. If one studies the propensity for refraction of photons (light) as the photons intersect a junction, it will be shown that more protons are refracted as the angle of intersection is increased. In this case there are at least two major junctions that need be included in any calculations. The first is the junction of outer space and the earth???s atmosphere. Second is the junction of the air at the solar panel location and the glass surface of the solar panel. If you consider the outer space and atmosphere junction it is easy to understand the refraction effects if you look at the difference in normal temperatures between the earths???s Polar Regions and the equator. Obviously, the sun illuminates the equator more directly than it does either the north or South Pole and the difference in refraction between the equator and the poles results in a substantial difference in absorbed energy (heat.) This same effect occurs in the morning and in the evening when the sun is rising or setting on a given area. So, the greatest amount of energy is available at the time of day that the sun is most directly impacting a given area at any geographic location. There is a similar effect for the air and glass junction of the solar panel itself. Suffice it to say that the most energy will be absorbed by the panel if the directions of the photons are exactly perpendicular to the collecting surface of the solar panel. Due to the cost of each panel it is preferred to have each panel generate the most amount of power possible each day so as to reduce the amount of time required to pay back the cost of purchase with energy savings due to power generated. Unless a movable and aimed solar panel is adjusted throughout the day to keep the sun oriented perpendicular to the collecting surface of the solar panel then the most efficient position is to have a fixed panel aimed so that it is perpendicular to the point of apogee for the sun at that geographic location. This is one of the reasons that solar power is not the only power solution we will ever need. Until such time that we have a power storage system that can store power during the sinusoidal peaks so that it can be release to the grid during the troughs we will need other energy sources to make up the difference. The phenomenon that Aidan identified is a way to ease the sinusoidal shape of the power generation cycle and make the power generated more consistent throughout the day. The only problem I see is that it would make the output of each panel not oriented perpendicularly to the daily solar apogee produce less energy than an optimally aligned solar panel. This alone will be cost prohibitive until the costs of solar panels are far below current prices.
I suspect that a fixed panel has an optimum direction for collecting energy and a panel oriented any other way will collect less. If you accept this, you can see that mounting any panel in any other orientation will produce less power than one which is set to the optimum. Having panels facing different directions will mean that they peak at different times and that will mean that you'll spend more of the day with a panel at (or close to) the optimum orientation *for that time of day* - this will make your power supply more even across the day (but not completely even, as you seem to claim), but the overall energy you collect will be less. As you say, power = voltage * current; the kid's measurements were "open circuit" so current was almost zero and so the power he developed was also almost nothing. As for the power "wasted" moving the rotating panels (or mirrors); I suspect that the companies involved have done their sums, so the energy taken to move the panels is significantly less than the extra energy collected.
Surely that depends on the efficiency of shape-memory alloy actuators though, and how much power they consume compared to the solar power generated?
I'm all for creative kids, I was one (and still am to some degree), but he and the adult pushers/followers need to understand the importance of doing thorough research before publishing your findings or THIS will happen. Time waster for all of us except for a "fun" experiment with little practical applications. Just because you can make a tree-shaped solar array, doesn't mean you should. He should never stop trying!
Anything off of dead-center facing the sun reduces the amount of energy that panel can absorb. Admittedly, the amount of reduction doesn't become significant until the sun is maybe 30?? off-center, but that means that during the day, even if you set up in the middle of the desert and point your panels due south, you will have almost zero power absorbed until maybe 10 or 11am local and again by 4 or 5 pm local The farther north you travel, the more extreme the swing of the sun appears and the less sun you get to use. The idea that this boy has and which you even deduce correctly is that the different cells will peak at different times of the day, but they will all peak and the effective output is relatively stable throughout the day. Yes, I do agree that the maximum output would be lower, but think of it like using a series of D-cell batteries powering a flashlight compared to a capacitor. The capacitor charges up to maximum power fairly quickly and fades away almost as quickly while the D-cell batteries, individually of limited life, could keep the light burning for days. Now, the problem with your last statement is false to the greater part because almost no solar farms move their panels to follow the sun. I'll grant a few do, and those are the most efficient of the bunch. But you're not going to see that on a rooftop array very often.
The actuator would consume no power in operation. Their movement is in response to their being heated by the sun. Some very complicated movement can be accomplished with these alloys when heated. A good start of your research should begin with a search of Nitinol.
- an array is just multiple solar cells - to maximise the total power generated from the array over any 24hr period, you simply have to maximise the total power generated from each individual cell - there will be a single optimum orientation and inclination for a cell that generates the most power over any 24hr period - this optimum orientation will be approx. due south (varying slightly due to regional climate) - so placing all the cells in the array facing due south will maximise total output - cells facing west/east will generate more in the evening/morning but less overall than cells facing south - the above assumes the positions of the cells are fixed - if consistency of output is more of a concern, a parabolic array will sacrifice total output to maintain a more constant output - modern arrays generally use some sort of parabolic focusing lenses that remove the need to consider orientation - isn't it strange how a 13 year olds science project can make national news in america? seems the move towards citizen reporting has left fact-checking out in the cold
On the other hand, with the effect of having an array with a consistent three to five elements running at or near their peak power throughout the day, logic of cause and effect would say that overall power produced would be equal to or greater than a fixed array with the same number of total elements even though the the peak overall power would be higher on the fixed array for an estimated 30% of the time. Just as an AC signal's peak might be +/-160V (320V Europe and elsewhere) the RMS is more like 120V (240V) per cycle. If the curved array can produce the 120V as a DC equivalent, the overall effect is a stable and constant power throughout the day. Yes, it is possible that a fixed array may reach a balance point on cost of assembly for the power produced, but if this boy's concept is confirmed, then it's possible a less expensive array configuration may result.
...was not that the peak power would be lower. My point was that the overall energy collected over each 24 hours would be lower. The points I made about the evenness of supply and also about movable arrays were simply to address the times you'd mentioned these factors.