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Drones will fly for days with new photovoltaic engine
- EGreg 7y agoSo what does this mean, we will be able to have drones flying continuously and getting energy from the sun?
- shakna 7y agoThere's been an efficiency break through for solar cells. > ... an achievement that could lead to an ultralight engine that can power drones for days. No such thing exists yet, but that's one of the hype ideas being thrown out there to try and get lay people excited about the breakthrough.
- dvh 7y agoDJI Phantom 3 is 0.3m wide and needs 120W to fly. Solar radiation at surface is 1000W/m2. 0.3m0.3m1000 = 90W at 100% efficiency. They claim 29% eficiency* (compared to regular 23%) which is only 26W out of 120W in ideal circumstances, realistically it would be maybe 1/3 of it. It will not fly. You can safely ignore ALL articles about breakthroughs in solar cell efficiency and look only at what is sold in shops because that's the only thing that matters. For years this has been 21-23% despite 5 or more articles about solar panel efficiency breakthrough every month for the last 20 years.
- Causality1 7y agoIt's the same as the "OMG this new battery will power your phone for years!!!" bullshit articles that come around every six months.
- walrus01 7y agoI essentially second everything that the person above is saying. There are an endless number of press releases and public relations bullshit articles put out by people who have some new "breakthrough" in photovoltaics. Whether it's special weird cells, or flower shaped ground mount things, or whatever. What I believe in, is what I can pull out my visa card and buy right now. And at the moment, here's what that looks like: One pallet load (22 panels), of high quality 156mm monocrystalline silicon cells, assembled into a 1.99 x 0.99 meter sized panel. Rated at 370W STC (standard test conditions) per panel. Under $0.60/watt. STC: https://www.altestore.com/blog/2016/04/how-do-i-read-specifications-of-my-solar-panel/ https://www.altestore.com/blog/2016/04/how-do-i-read-specifi... Everything else is either so high priced that you have to contact a sales person to buy it (weird fresnel lens concentrator and triple junction GaAs cells intended for use on spacecraft), or is not manufactured in sufficient quantity to gain even 1% of market share, and therefore is not stocked by major photovoltaic equipment dealers.
- IanCal 7y agoThe article is not about solar cells though. It's about thermophotovoltalics, where you'd use a high temperature heat source.
- lgats 7y agoQuadcopter "drones" are much less efficient than winged plane "drones". Additionally, they have the large surface area of the wings to collect more solar energy. Though the image does show a consumer quadcopter device...
- Gravityloss 7y agoYeah the Airbus Zephyr solar powered drone was up for 25 days.
- IanCal 7y agoNo, the article is about efficiently converting heat to electricity, it's not about solar panels.
- ajuc 7y agoWe already have drones with wings that are capable of that, or close to it. This would make them more efficient. https://www.youtube.com/watch?v=8m4_NpTQn0E https://www.youtube.com/watch?v=8m4_NpTQn0E For quadcopters and similar I doubt it will be enough.
- amirhirsch 7y agoI’ve seen reports of thin film organic solar cells that produce >1 watts per gram of material. A quadcopter motor can generate multiple grams per watt of power. You can today go and buy 100W from a 3.3lb panel, which is like half way there and not even trying. I’m guessing it’s probably possible to make a quadcopter that can hover indefinitely in the sun.
- walrus01 7y agoNo, not really. The math for watts consumed in total just to hover, for a very large quad, hex or octocopter (with 24 to 28 inch size props, so optimal grams/watt thrust efficiency for something you can fit in a van), doesn't work out. The weight and size of a 400W solar panel made from the very best cells you can buy commercially today is considerably more than the wattage you would need to hover a 10+ kilogram coaxial octocopter capable of carrying such a large panel on top of it. For a large octo, a single Tmotor U8 motor with a 28 inch prop requires anywhere from 310W to 850W while in flight, and there's eight motors + eight props on a coaxial medium/heavy lift octo. I showed this article to a few people in the professional arducopter/ardupilot/arduplane community and it has been quite thoroughly chuckled at. For reference, here's the datasheet for a prototypical motor, a tmotor u8 170kv with 28 inch prop. You'll see the table for watts consumed and grams/watt efficiency with motor+prop mounted on a thrust stand. http://store-en.tmotor.com/goods.php?id=324 http://store-en.tmotor.com/goods.php?id=324 If you wanted to put photovoltaics on a quad/hex/octocopter, you have multiple issues with not enough top deck surface area, not being able to introduce a lot of "sail area" (something big and light that will be grabbed by the wind) sticking out of the top, and the weight of the pv itself. There is no PV solution anywhere near small enough to fit on the top deck of a really big commercial coaxial octo that is also capable of producing 2000W. Not even 100W in sunlight. Somewhere from 18 to 30 times less watts than is required just to hover in one place.
- zaarn 7y agoIt reads a bit overhyped, considering they claim to power a house with a generator the size of an envelope; that's a hard no since there is a limit on how much energy hits every square meter and it's not THAT much.
- asteli 7y agoTo elaborate, solar energy hitting the Earth’s surface is about a kilowatt/m^2 if conditions are perfect. If you were able to convert solar power at the maximum theoretical PV efficiency (the Shockley-Queisser limit, 33.7%), you’d need about 3 square meters to just to make toast.
- sbierwagen 7y agoFor those confused by that oddly low theoretical limit: it applies to single junction cells. Panels that achieve higher efficiencies do it by stacking multiple cells.
- wyattpeak 7y agoYour broad point is right, but the SQ limit only applies to conventional PV cells, it's not a theoretical limit on PV efficiency and in fact has been exceeded by other cell architectures.
- numlock86 7y agoIs this supposed to sound bad or good? Well, 3m² to make toast intuitively sounds bad I guess. Well, consider this: It's enough to run 2 small office PCs with all peripherals. Considering that it sounds much more positive. Really just anything producing heat would sound bad because of power dissipation. A toaster is probably one of the most extreme ... (Imagine putting 1kW into a slice of bread without power dissipation!)
- asteli 7y agoSomeone else wrote the comment I meant to, essentially doing the math to show that one would need an awkwardly large solar panel to power something like a quadrotor drone.
- deleted 7y ago[deleted]
- bwang008 7y agoJust increasing the efficiency to 30pct is a pretty big deal. If these could be mass produced cheaply to market, that would be incredible.
- agumonkey 7y agoSurprisingly never heard of Thermophotovoltaics. Here's a simple diagram https://proxy.duckduckgo.com/iu/?u=http%3A%2F%2Fanilyuksel.files.wordpress.com%2F2013%2F03%2Ffig1.jpg&f=1 https://proxy.duckduckgo.com/iu/?u=http%3A%2F%2Fanilyuksel.f... It seems like 'impedance matched' photovoltaics.. very interesting.
- PakG1 7y agoHah, now I have a vision of one of these things hooked up to every air conditioner in the world to claw back some of the electricity that the air conditioner uses. I imagine the heat would need to be a bit more than what an air conditioner generates though, but I know nothing about the topic, so who knows.
- IanCal 7y agoPeople seem to be misinterpreting this a lot. This is not about solar cells. This is about thermophotovoltalics, and the application here is using a burning fuel source to generate electricity. The "drone" the paper talks about seems to be a reference to another paper on unmanned sea vehicles though. Edit - to be fair the flying drone part is from the corresponding author.
- clouddrover 7y ago> This is not about solar cells. There's wasted thermal energy when using solar cells. If you can capture some of it you'd be able to increase the efficiency of the cell.
- pjc50 7y agoExactly. The paper is here: https://www.pnas.org/content/early/2019/07/15/1903001116 https://www.pnas.org/content/early/2019/07/15/1903001116 The context of thermophotovoltalics is very interesting - conventional heat-to-electricity engines are limited by Carnot efficiency, which relies on a "cold side" and generally has low theoretical maximum efficiencies. This approach takes any hot emitter heated by any process - fuel burning, solar concentration, nuclear - and extracts electricity directly from the mostly IR photons it emits. > Here, we present experimental results on a thermophotovoltaic cell with 29.1 ± 0.4% power conversion efficiency at an emitter temperature of 1,207 °C. This is a record for thermophotovoltaic efficiency.
- jacobush 7y agoI sense a new kind of nuclear power plant?!
- StreamBright 7y agoThat would be amazing to get rid of the traditional boiling water part of nuclear power plants. Is this what you are thinking about?
- 7y ago
- clouddrover 7y agoResearchers from Rice University have an approach they think can get to 80% efficiency using a carbon nanotube film: https://news.rice.edu/2019/07/12/rice-device-channels-heat-into-light/ https://news.rice.edu/2019/07/12/rice-device-channels-heat-i...
- shyam-geek 7y ago"Fly for Days", Wondering what are the trade-offs here? Can those drones carry a load or cover certain distances to be of any functional use.
- emiliobumachar 7y agoSurveillance, spying, communications. Such drones could encroach a lot into roles currently assigned to satellites.
- amelius 7y agoSo did they show an actual drone flying for days?
- kgantchev 7y agoNo, but they could... someday... in the future!
- acje 7y agoI wonder if it is feasible to make PV panels that concentrate the IR part of the light spectrum and guide it to a TVP unit through fiber optics.
- gnode 7y agoI don't see why you'd need fibre optics for that. Mirrors would work just fine, as in a concentrated solar plant.
- pjc50 7y agoI'm having trouble envisaging how this would work? What might work though is what I'm going to call Pink Floyd Concentrated Solar: collimate light from the sun over a large area into a beam, then run that beam through a prism. That would allow the use of solar cells with different efficiency bands. (I doubt this would make overall sense given the cost and size of optics, but it's fun to think about)
- IshKebab 7y agoTerrible article. "Scientists have invented a new thing which could (i.e. doesn't yet) power drones, and houses and space ships and cars, and computers and ..... (10 paragraphs later). Oh btw it works by adding a mirror or something. The end."
- dwighttk 7y ago"For the past 15 years, the efficiency of converting heat into electricity with thermovoltaics has been stalled at 23 percent. But a groundbreaking physical insight has allowed researchers to raise this efficiency to 29 percent. Using a novel design, the researchers are now aiming to reach 50 percent efficiency in the near future by applying well-established scientific concepts." ^interesting part, the drone stuff is just click-bait
- Tade0 7y agoI wonder if this would be enough to create the ultimate flex-fuel vehicle?
- blamestross 7y agoDoes this mean we can make lighter/smaller RTGs?
- deleted 7y ago[deleted]
- flanbiscuit 7y agoleft out the actual science part of this interesting part: > According to Yablonovitch, this finding builds on work that he and students published in 2011, which found that the key to boosting solar cell efficiency was not by absorbing more photons (light) but emitting them. By adding a highly reflective mirror on the back of a photovoltaic cell, they broke efficiency records at the time and have continued to do so with subsequent research.
- mac01021 7y agoPerhaps a stupid question: Is this simply a matter of getting a second chance to capture the photon (by the same mechanism) as it makes a second pass through the cell after reflection?
- bufferoverflow 7y agoWe have multijunction cells with 47.1% efficiency (as of June 20th). Other than the price, what's the significance of single-junction 50% efficiency? https://en.wikipedia.org/wiki/File:CellPVeff(rev190702).pdf https://en.wikipedia.org/wiki/File:CellPVeff(rev190702).pdf
- duckqlz 7y agoI was unclear how this differed from what I would traditionally consider as solar power (photovoltaic power) as I had never heard of thermophotovoltaic power. After a quick search I found the following helpful: “The basic principle [of thermophotovoltaics] is similar to that of traditional photovoltaics (PV) where a p-n junction is used to absorb optical energy, generate and separate electron/hole pairs, and in doing so convert that energy into electricity. The difference is that the optical energy is not directly generated by the Sun, but instead by a material at high temperature (termed the emitter), that causes it to emit light. In this way thermal energy is converted to electrical energy.” [1] [1] https://en.m.wikipedia.org/wiki/Thermophotovoltaic https://en.m.wikipedia.org/wiki/Thermophotovoltaic
- lightedman 7y agoBasically a highly-inefficient method of converting energy. I've looked at the article and the pictures, and what I see is basically slapping a solar cell with a gold mirror backing right near a hot ribbon of graphite - eg we're trying to use highly inefficient incandescence to generate light. Want to know what works better? Just the simple mix of gold into the p-n junction matrix and finger lines. Takes a silicon solar cell up to about 35% efficiency when properly doped into the junction material. This technology? Well, given incandescence isn't going to break ~30% efficiency (excepting in the IR-glass-sandwiched tungsten filament) you're literally just wasting energy. Best we've seen in general incan is ~12% efficiency, so enjoy your 30-ish percent of that (4%). You're better off with other technologies. This is neat, but you're looking at pretty much over-simulating the conditions of a solar cell welding line, which means that solar cell is going to likely bust over time under the heat stress. I foresee tons of problems with this tech, from the incan ribbon breaking to the cell harvesting energy breaking from the heat/cool cycling.
- mattsears18 7y agoIn 6th grade I connected a 9V battery to my mechanical pencil lead and lit my science folder on fire. Basically the same thing...
- Intermernet 7y agoNot really, as it didn't use any energy not present in the 9v battery. This is about using solar energy in a more efficient arrangement, through reflection of waste solar energy to heat a medium and create a higher efficiency thermo-voltaic cell based on a photo-voltaic cell (I'm probably very wrong with my terminology in the last sentence, but, either way, it ain't no burning graphite connected to a battery.)
- kmacdough 7y agoFor the record, to sustain a modern small drone at 50% conversion, you still need at least a 50cm x 50cm panel with optimistic estimates. This is completely ignoring the fact that such panels would need to be mounted without destroying the aerodynamics of the propellers
- crusso 7y agoI really dislike headlines like this on HN that imply that lab research mixed with theory are somehow practical. It would be great if there were a "Theoretically" in there along with removing the hype-included "drone" reference.
- baking 7y agoEli Yablonovitch's company, Alta Devices, manufactures a thin film high efficiency PV cell but they can't compete right now against cheap Chinese silicon wafer cells in the solar panel market, so they are focusing on niche markets, primarily drones at first. His 2017 talk to the MIT Energy Initiative (https://www.youtube.com/watch?v=u_K1URyarE0 https://www.youtube.com/watch?v=u_K1URyarE0) goes into the economics of solar and why his company is using this strategy. Basically, they need to find niche markets until they can work their way down the learning curve and achieve economies of scale. He also discusses thermophotovoltaics. Very efficient light-weight PV allows for longer drone flights but night is an obstacle to multi-day flights. Given the choice between batteries and fuel to keep aloft until dawn this does seem like a possible breakthrough, deserving of the article's title, although the text could be a lot more clear.
- baking 7y agohttps://www.youtube.com/watch?v=lDxJsa8miNQ https://www.youtube.com/watch?v=lDxJsa8miNQ has a lot more information on thermophotovoltaics, including drone applications, and some more info on solar panel economics.
- rodolphoarruda 7y agoI've got an immediate idea reference from the movie Interstellar, which shows a drone that supposed to be flying non stop around the globe for X number of years until it had its navigation system hacked by people and then landed.
- lowdose 7y agoI heard the raw cocaine price of a kg dropped by 20k last 10 years. I bet they are already flying.