"Optical/3D Rectennas"

[Northstar1989]

Take a look at this link:

https://genesisnanotech.wordpress.com/2016/04/07/solar-cells-will-be-made-obsolete-by-3d-rectennas-aiming-at-40-to-90-efficiency/

 

These seem like cool stuff, and sound like they could have major applications for spacecraft if they really can exceed the efficiency of solar panels by so much (in reducing payload-mass needed for electricity generation).  They also sound like they could lead to more widespread use of rectennas in general (which would be a good thing for eventual applications of Microwave Beamed Power to beam electricity to power-hungry spacecraft in Low Earth Orbit, such as Propulsive Fluid Accumulators or large ion-propelled probes).  However I'm not sufficiently familiar with nanotechnology to accurately evaluate the potential of this technology.  What do you guys think?

 

Regards,

Northstar

Edited April 12, 2016 by Northstar1989

[Camacha]

The graphics of that website makes me suspicious about its quality.

Edited April 9, 2016 by Camacha

[Northstar1989]

Try to remain on-topic.  Talk about the technology, not what you think of the website (which is just a website with news about nanotechnology), please.

Edited April 9, 2016 by Northstar1989

[RainDreamer]

Other link about the things :

http://www.eetimes.com/document.asp?doc_id=1327819

 

[Camacha]

20 hours ago, Northstar1989 said:

Try to remain on-topic.  Talk about the technology, not what you think of the website (which is just a website with news about nanotechnology), please.

Discussing the source is on-topic. A discussion about science has zero value without reliable sources.

[YumonStudios]

21 hours ago, Northstar1989 said:

Take a look at this link:

https://genesisnanotech.wordpress.com/2016/04/07/solar-cells-will-be-made-obsolete-by-3d-rectennas-aiming-at-40-to-90-efficiency/

 

These seem like cool stuff, and sound like they could have major applications for spacecraft if they really can exceed the efficiency of solar panels by so much (in reducing payload-mass needed for electricity generation).  They also sound like they could lead to more widespread use of rectennas in general (which would be a good thing for eventual applications of Microwave Beamed Power to beam electricity to power-hungry spacecraft in Low Earth Orbit, such as Propulsive Fluid Accumulators or large ion-propelled probes).  However I'm not sufficiently familiar with nanotechnology to accurately evaluate the potential of this technology.  What do you guys think?

 

Regards,

Northstar

It's not going commercial any time soon, it relies on Carbon Nanotubes, which have proven to be a royal pain to create in large quantities (along with graphene sheets in general).

We're likely to see 60-70% efficiency multi-junction cells, and UV and Infrared cells become widespread before this thing, if Graphene mass-reproducibility improves at the rate we're seeing.

Edited April 10, 2016 by YumonStudios

[Northstar1989]

On 4/9/2016 at 6:35 PM, Camacha said:

Discussing the source is on-topic. A discussion about science has zero value without reliable sources.

You're taking the Peripheral Route to analyzing the issue- looking at the superficial aspect of the website rather than the scientific merits of the idea...

Regardless, here are some more reliable articles on the topic:

http://www.sciencealert.com/world-s-first-optical-rectenna-converts-light-directly-into-a-dc-current

http://spectrum.ieee.org/nanoclast/semiconductors/materials/optical-rectenna-could-doube-solar-cell-efficiency

 

 

On 4/10/2016 at 7:11 PM, YumonStudios said:

It's not going commercial any time soon, it relies on Carbon Nanotubes, which have proven to be a royal pain to create in large quantities (along with graphene sheets in general).

We're likely to see 60-70% efficiency multi-junction cells, and UV and Infrared cells become widespread before this thing, if Graphene mass-reproducibility improves at the rate we're seeing.

No, Carbon Nanotubes have only proven to be a pain to create large/long continuous tubes of.  There's no problem with creating forests of lots of microscopically-short tubes, which is all these Optical Rectennas require...

60-70% is far beyond the theoretical efficiency limits of multi-junction PV cells, so where do you get that idea?  This technology would be capable of 40% efficiency, and that's already a huge step above the 20% efficiency that the very best commercial photovoltaic cells are capable of today, and on par with (but much cheaper than) the 40% efficiency that the very best prototype units are capable of today (and which are close to the theoretical maximum performance for the technology, at least with current understanding/materials...)

 

Regards,

Northstar

Edited April 12, 2016 by Northstar1989

[YNM]

Seems to be legit, although only someone with a proper knowledge of quantum-thingy will be able to determine is it real or not. Called nantenna by wiki.

[Camacha]

1 hour ago, Northstar1989 said:

You're taking the Peripheral Route to analyzing the issue- looking at the superficial aspect of the website rather than the scientific merits of the idea...

The thing is, the internet is full of fanciful stories. Before spending time and effort looking into something, it needs to pass at least a cursory inpection. There is too much junk out there to merit a comprehensive analysis of any source.

So while I do inderstand your sentiment, being sceptic towards unknown or unverified sources is healthy Any source first has to pass before being debated. At the very least it will save you from free energy, flat Earth and similar hocus pocus.

[Nuke]

rf tech is voodoo. but its very scientifically accurate voodoo. its very hard to get your head around these things, but they work.

the idea is if you can use an antennea of a certain size to pick up a radio wave of a certain wavelength, and if light is just a wave of a shorter wavelength, then an antennea of a certain size should pick that up too. with lessons learned in semiconductor manufacture (at least when they add nanotubes to their bag of tricks) it is now possible to build antenneas that can pick up visible spectrum light waves. so this technology is very feasable. higher frequencies have shorter wavelength and require smaller antennas. thats why your cell phone uses a chip antennea where an old tv requires a big areal antennea. its basic radio 101. the problem is basically a manufacturing one.

Edited April 12, 2016 by Nuke

[wumpus]

Generally speaking, high efficiency solar power is pretty pointless groundside and absolutely critical in space.  If they can make the rectennas cheaper than traditional semi-conductor solar cells, they might have something, but pretty much any kind of complicated structure will have a hard time beating traditional solar (which as far as I know, is pretty much the simplest "chip" you can imagine).

Also note the 40-90 percent weaseling.  I'm pretty sure space applications can get 40% efficiency solar cells.   The upper bound would require some sort of magic to do with semiconductors, but other RF voodoo might not be so unlikely (and yes, RF is weird stuff).

[Nuke]

with the way semiconductor manufacturing works, i can imagine these things being very expensive. were starting to look at ways to use nanotubes to transfer heat in more 3d processor and memory designs to provide the heat of the bottom layers a path out of the die. the fabs know how to build these kinds of things. these recentness are really just a nanotube antenna and a diode, each one being a very small dc power source. if you need a square meters worth of rectenneas, several silicon wafers worth of parts, and thats going to cost you.

[Northstar1989]

On 4/13/2016 at 8:22 PM, wumpus said:

Generally speaking, high efficiency solar power is pretty pointless groundside and absolutely critical in space.  If they can make the rectennas cheaper than traditional semi-conductor solar cells, they might have something, but pretty much any kind of complicated structure will have a hard time beating traditional solar (which as far as I know, is pretty much the simplest "chip" you can imagine).

Also note the 40-90 percent weaseling.  I'm pretty sure space applications can get 40% efficiency solar cells.   The upper bound would require some sort of magic to do with semiconductors, but other RF voodoo might not be so unlikely (and yes, RF is weird stuff).

Did you miss the part of the articles where they say these can be manufactured at a *fraction* of the cost of traditional solar panels? (or, sadly, like most people who post on articles in a forum did you simply not bother reading the article?)

Yes, the best PROTOTYPE units can get 40%- those are the types of bleeding-edge ultra-expensive technology they send up on spacecraft when they can get them.  The best units you can buy to, say, put on your house or factory rooftop, however, only can achieve around 20%...

These optical rectennas should be able to regularly achieve 40% efficiency at a fraction of the cost of even medium-efficiency traditional photovoltaics once the technology is mature, at least according to the inventors (who also claim the technology could mature very quickly- MUCH faster than the PV cell development curve).  So, perhaps a wise technology for the government to invest heavily in, if their claims turn out to be true.

The higher efficiency is nice (and has practical benefits in particular for things like solar panels used to power electric ships and planes- though theses are still more a novelty than anything else, especially since we already possess the technical know-how to "manufacture" synthetic fossil fuels to continue to power our boats and planes once our "natural" supply runs out) but the COST advantage is game-changing...

 

On 4/13/2016 at 4:26 PM, Nuke said:

with the way semiconductor manufacturing works, i can imagine these things being very expensive.

What planet are you living on?  Haven't you ever heard of Moore's Law?  Manufacturing semiconductors is an EXTREMELY cheap process when done in bulk nowadays, and that is *precisely* what we'd be doing for a device meant to replace traditional solar panel's role completely...

 

Regards,

Northstar

Edited April 20, 2016 by Northstar1989

[wumpus]

6 hours ago, Northstar1989 said:

Did you miss the part of the articles where they say these can be manufactured at a *fraction* of the cost of traditional solar panels? (or, sadly, like most people who post on articles in a forum did you simply not bother reading the article?)

 

What planet are you living on?  Haven't you ever heard of Moore's Law?  Manufacturing semiconductors is an EXTREMELY cheap process when done in bulk nowadays, and that is *precisely* what we'd be doing for a device meant to replace traditional solar panel's role completely...

Regards,

Northstar

A: The article makes a lot of assumptions assuming the existence of mass produced carbon nanotubes.  If and only if carbon nanotube production gets to the point of silicon wafers can you expect the best case scenario described in the article.  It might happen, but it sounds like decades in advance (although a better bet than fusion).

B: Moore's law is all about making things smaller (twice the number of transistors on a chip every x years).  Solar power is all about needing larger and larger surfaces.  Moore's law tells us nothing about solar panels.

[Nuke]

yep. moors law is meaningless when you are talking 2 square meters of solar area. how many wafers do you need to cover that? a dozen at least? should cost as much as a case of xeons.

[todofwar]

On 4/9/2016 at 10:41 PM, Camacha said:

The graphics of that website makes me suspicious about its quality.

That picture is fine art by scientist standards. They cite Georgia Tech, so it was probably made by a grad student that got roped into being the designated lab graphic designer despite having zero design experience.

[Northstar1989]

On Friday, April 22, 2016 at 10:03 AM, todofwar said:

That picture is fine art by scientist standards. They cite Georgia Tech, so it was probably made by a grad student that got roped into being the designated lab graphic designer despite having zero design experience.

Lol.

 

So anyone with thoughts about the science itself?

 

Regards,

Northstar

[K^2]

Science is solid. It's honestly a question of how long it will take them to get this to visible light wavelengths and into production and whether something better will come along before that happens. But in either case, this spells doom to fossil fuels. Between advances in photovoltaics and batteries, about the only market for fossil fuels that won't be rapidly collapsing in the next decade is Jet-A. And even airliners might start to transition to LH2 if energy prices drop as much as rectennas can bring it down.

[shynung]

6 hours ago, K^2 said:

And even airliners might start to transition to LH2 if energy prices drop as much as rectennas can bring it down

LH2? That thing needs really big fuel tanks, it has terrible density. Air travel still has to bother with aerodynamic resistance, so unless the planes start to look like Skylon (basically around 4/5 of the fuselage are propellant tanks), I don't think we'll see LH2 jumbo jets.

Lighter hydrocarbon (C1-C4) fuels, I believe is still feasible.

[Northstar1989]

2 hours ago, shynung said:

LH2? That thing needs really big fuel tanks, it has terrible density. Air travel still has to bother with aerodynamic resistance, so unless the planes start to look like Skylon (basically around 4/5 of the fuselage are propellant tanks), I don't think we'll see LH2 jumbo jets.

Lighter hydrocarbon (C1-C4) fuels, I believe is still feasible.

LH2 is also dangerous and difficult to handle, and has enbrittlement problems.  You'll see passenger jets flying on thermal turbojets powered by cheap/portable fusion reactors or microwave beamed power relayed from orbiting satellites (the latter of these two we could already do with today's technology- but not economically with current launch-costs or the price of microwave transmitters...) long before you see them powered by LH2 combustion...

 

Regards,

Northstar

Edited August 6, 2016 by Northstar1989

[Nuke]

6 hours ago, shynung said:

LH2? That thing needs really big fuel tanks, it has terrible density. Air travel still has to bother with aerodynamic resistance, so unless the planes start to look like Skylon (basically around 4/5 of the fuselage are propellant tanks), I don't think we'll see LH2 jumbo jets.

Lighter hydrocarbon (C1-C4) fuels, I believe is still feasible.

there was the lapcat derivative of the skylon. pretty much an atmospheric only engine. it would use scimitar engines, which is a sabre minus the rocket mode. it would still have a precooler, and look more like a rocket than a turbine, but no lox injection systems. and like the skylon, it would be a flying fuel tank.

Edited August 6, 2016 by Nuke

[shynung]

2 hours ago, Nuke said:

there was the lapcat derivative of the skylon. pretty much an atmospheric only engine. it would use scimitar engines, which is a sabre minus the rocket mode. it would still have a precooler, and look more like a rocket than a turbine, but no lox injection systems. and like the skylon, it would be a flying fuel tank.

That's the plane I meant. Reaction Engines called that plane the A2. Like you said, it's basically Skylon, minus the rocket mode.

You'll see passenger jets flying on thermal turbojets powered by cheap/portable fusion reactors or microwave beamed power relayed from orbiting satellites (the latter of these two we could already do with today's technology- but not economically with current launch-costs or the price of microwave transmitters...) long before you see them powered by LH2 combustion...

I don't think so. An older thread in this forum discussed about the feasibility of capturing CO2 from the air to create hydrocarbon-based fuels. The process itself is energy-hungry for sure, not least because of the generally low concentration of atmospheric CO2 compared to O2, but it could produce hydrocarbons. If the OP there considered using more concentrated forms of carbon, like coal or biomass, and avoiding burning some of the carbon feedstock for energy, we can improve the efficiency of the process.

In the end, if cheap fusion power became a reality, I'd imagine these would fuel future jet airliners. LH2 would still be somewhat silly (flying fuel tanks), but microwave thermal jets? We don't even have a working prototype right now.

 

Edited August 6, 2016 by shynung

[K^2]

14 hours ago, shynung said:

LH2? That thing needs really big fuel tanks, it has terrible density. Air travel still has to bother with aerodynamic resistance, so unless the planes start to look like Skylon (basically around 4/5 of the fuselage are propellant tanks), I don't think we'll see LH2 jumbo jets.

Lighter hydrocarbon (C1-C4) fuels, I believe is still feasible.

If LH2 drops to 1/5th the cost of Jet-A by weight, which is where things are heading with rectennas, it will be economical to build jumbo planes with humongous LH2 tanks to fly long range. Such an airplane will fly at a significantly higher cruise altitude offsetting much of the drag losses. It will still be energetically disadvantageous, but economically advantageous even with higher construction and maintenance costs, simply because how much of plane's operation is fuel costs.

In contrast, short hop regional planes might start getting replaced with electrics. We're looking at flights that are currently serviced by turboprops first and foremost, but small regional jets are likely to start being replaced as well. Where Jet-A is likely to remain dominant fuel the longest is mid-range flights. I don't see planes in A320, B737, B757 range being replaced with alternative fuel planes with foreseeable technology. On the other hand, if Hyperloop takes off, we might not need to.

[magnemoe]

13 hours ago, Northstar1989 said:

LH2 is also dangerous and difficult to handle, and has enbrittlement problems.  You'll see passenger jets flying on thermal turbojets powered by cheap/portable fusion reactors or microwave beamed power relayed from orbiting satellites (the latter of these two we could already do with today's technology- but not economically with current launch-costs or the price of microwave transmitters...) long before you see them powered by LH2 combustion...

Regards,

Northstar

Hydrogen makes sense for upper stages on rockets, hypersonic planes and lifting gas. it has very good ISP, it react fast and is cold something who is nice for skylon precoolers and scramjets, 

[shynung]

7 hours ago, K^2 said:

If LH2 drops to 1/5th the cost of Jet-A by weight, which is where things are heading with rectennas, it will be economical to build jumbo planes with humongous LH2 tanks to fly long range. Such an airplane will fly at a significantly higher cruise altitude offsetting much of the drag losses. It will still be energetically disadvantageous, but economically advantageous even with higher construction and maintenance costs, simply because how much of plane's operation is fuel costs.

In contrast, short hop regional planes might start getting replaced with electrics. We're looking at flights that are currently serviced by turboprops first and foremost, but small regional jets are likely to start being replaced as well. Where Jet-A is likely to remain dominant fuel the longest is mid-range flights. I don't see planes in A320, B737, B757 range being replaced with alternative fuel planes with foreseeable technology. On the other hand, if Hyperloop takes off, we might not need to.

There are other concerns with the LH2 plane approach. As they're practically flying fuel tanks, an airplane fuel by LH2 with the capacity of a B777 or A340 would be humongous. They might be large enough to necessitate new infrastructure - wider/longer runways, larger aprons, larger hangars - which means these LH2 airplanes are limited to airports which can handle their size.

Also, abandoning fossil fuels doesn't necessarily means abandoning Jet-A. We have ways to create synthetic equivalents of crude oil from solid carbon sources, such as coal or biomass.

Edited August 7, 2016 by shynung