Efficiency will leap from ~40% to ~600%. Wow....
A team of European researchers has discovered that a single nanowire can concentrate the amount of solar energy delivered to a photovoltaic cell by a factor of up to 15, a breakthrough that could improve the efficiency of electricity-producing solar cells. "Due to some unique physical light absorption properties of nanowires, …
Apart from the comparison of a percentage rather than, say, a real number:
The maximum amount of solar energy for a given area is limited to the energy given by the sun to that area of ground. The theoretical limit of which is about 1KW / sq. metre in full daylight on a cloudless day. Unfortunately, huge portions of that are in ultraviolet, infrared and other frequencies spread throughout the spectrum. So it doesn't matter how clever the physics are (and this certainly sounds like snakeoil to me, but I can't be bothered to research it precisely because of that), you can't get more than a few instantaneous KW out of your entire house + garden unless you live somewhere really large. By the time you sort out storage, transport, other losses etc. then it really comes down to basically what we are managing now with the "new technology" solar panels so expensive that they never pay themselves back.
So for every house you need to serve, you find yourself blanketing an equivalent area in solar panels (and/or killing wildlife / stealing energy from that area for the life of the system). It doesn't matter what tricks, "concentrators" or materials you use, that's just how much energy you can ever find in the covered area. Which kind of makes you wonder what that will do to the pressure for new housing, unspoiled areas of ocean, etc. Every housing estate you build, you allocate the same area somewhere else to power it (if you're lucky, more it's a long way away, off-shore, etc.).
Solar just isn't practical, even with 100% efficient devices (that don't exist). What you gain in "free" energy, you make up for in rare earths, areas of land required, etc.
I like the way you point out a few valid points in general terms and then conclude in hand-waving generalisations that logically this means you must "find yourself blanketing an equivalent area in solar panels".
What about the billions of people who live in sunnier climates? We'll just kill the research because it might not be viable at all latitudes?
And even then we'd need proper figures. You say 1KW/m^2 is maximal (where - UK, equator, 1 mile above sea level?) but even at 10% of that with lousy weather, well doesn't the average house have 50-100m^2 of roof? If you could consistently generate only 100W, that negates a LOT of the stuff you leave turned on all day.
"So it doesn't matter how clever the physics are (and this certainly sounds like snakeoil to me, but I can't be bothered to research it precisely because of that)"
Cool - just for a moment I had thought you hadn't researched it because you haven't got a clue what they're on about.
"Solar just isn't practical, even with 100% efficient devices (that don't exist). What you gain in "free" energy, you make up for in rare earths, areas of land required, etc."
Even better news - I stupidly thought for a moment that it might be useful in some parts of the world as part of a total energy generation scheme involving other fuels. Just as well you let 'em know it "isn't practical".
The best you can currently hope for from a solar panel is around 175W/m2 (with a solar irradiation of 1000W/m2) which means your 5m x 5m array will only be producing a theoretical peak of 4.375kW. Using this http://www.efficientenergysaving.co.uk/solar-irradiance-calculator.html calculator reveals that you can generate 7.5kWh on a good sunny March day. The average UK household uses 9kWh which leaves you with a shortfall of 1.5kWh. If your array is covered in snow it wont be generating anything and any dirt on it will also reduce the efficiency.
With a peak of 4.375kW your array is unlikely to provide enough spot power for a 3kW kettle especially in the UK which is a considerable distance for any point in the world where solar irradiance reaches 1000W/m2
> array is unlikely to provide enough spot power
Boil the kettle too many times and what are you going to use for evening/night-time and morning?
The 7.5kWh is on a perfect sunny day with a clean solar array. Storing and discharging the energy in short bursts introduces large inefficiencies. You would have to use lead-acid batteries as these are capable of producing high surge currents (you need to boil that kettle). With lead-acid you can get a charge/discharge efficiency of 90% but only if you start from fully discharged battery and then fully charge and discharge it. If the usage profile of your batteries is to discharge up to half the charge and then to recharge them you will only get as little as 55% efficiency in the charge/discharge cycle.
So yes you can boil that kettle by using stored energy rather than spot energy but the 7.5kWh available for your home is going to significantly reduce due to the storage inefficiencies.
I am not necessarily saying solar-only is a viable option for the UK. But if solar panels and a couple of lorry batteries could reduce your usage 30%, that's pretty significant and potentially worth doing. Or if you could go solar-only in a few months a year, normal power stations can adapt to that... they can't ramp up on a daily basis but can over weeks/months (I'm sure they already do in the winter).
With a peak of 4.375kW your array is unlikely to provide enough spot power for a 3kW kettle
There are these things called "accumulators", otherwise known as "rechargeable batteries". They allow storage of energy, so that you can use the energy generated but not used at that instant, at a later time. For instance at night, at which time there's no actual photovoltaic generation to speak of.
Can you explain to me how making the claim that the "array is unlikely to provide enough spot power for a 3kW kettle especially in the UK" has anything to do with storing power? Spot power is the power generated at that moment in time, not the power generated yesterday and stored in a battery.
Aside from using stored energy to make the cup of tea you could also draw power from the grid or use a backup diesel generator or, if its windy enough, a wind turbine. There are any number of ways you can make up for the lack of spot power from the array. None of them are relevant.
Not just accumulators, but judicious use of supercaps will help smooth out things and deal with the inefficiencies inherent in speeding up chemical reactions. It's not as if you have a limited amount of space to stuff 'em in, unlike EVs where they're extremely useful for conserving energy during regenerative braking/hard acceleration pulses.
Cleaning isn't much of an issue either. Hydrophobic glass technology results in them being mostly self-cleaning so remaining issues mainly revolve around things like birdshit and leaves.
"The light-concentrating effect occurs because the wavelength of the light traversing the nanowaires is smaller than the nanowires themselves, thus causing resonance of the light in and around the nanowires."
The wavelength of light is smaller than many structures you could mention, so this can't be the 'because', surely?
Is it because the wavelength is comparable to the thickness of the nanowires?
If the nanowire is comparable in size to the wavelength of the light, then it could be acting as a monopole antenna, thus delivering electrical energy to the substrate. In which case, the photovoltaic effect is being supplemented by a traditional/classic electromagnetic antenna, on a very small scale. So, the theoretical limit of photovoltaic efficiency would stand but the device would be a dual mode energy converter.
@JeffyPooh - Yes, those numbers need looking at and thinking about.
It looks like it's lensing the light in free air/vacuum onto the junction. That would give a small improvement over traditional lensing with glass or mirrors. The big gain would be concentrating light directly onto the junction from the sides without needing to penetrate layers of semiconductor.
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Oops! Thankyou Pookietoo, I wasn't paying attention.
Note to self:
Nano wires: generic, wires of any material on the scale of 10−9 meters
Nano tubes: tubes of carbon, similar to a buckyball but a tube. Tricky to manufacture in long lengths, though we keep hearing of incremental advances.
I think part of my brain incorrectly read it as nano-tubes, due to a previous solar-panel concept in which a 'forest' of short, irregular nano-tubes is deposited/grown on a substrate (much easier than making a long nanotube, I'm lead to belive), making the solar panel very black indeed.
Like I said, people will sell you nanowires, but only in small quantities. And if the seller is an actual business, they are not keeping the lights on based on selling nanowires. Their nanowire business is either a tiny side business or they are basically a contract house that lives off government grants. I hope nanowires turn out to have a future, but so far, not.
None. While CNT's and Bukcyballs have been of academic interest, they so far have failed to be of any commercial value. A number of startups based on them have failed, and none have become economically viable. That does not mean there are no companies that will sell you some CNT's, but they are all companies either really living off VC funding or government grants.
As the bastrac goes, yes, you can get maybe 200-300% efficiency.
BUT (big one) you get 300% of the directed energy, but you need space around the nanowire... because you are getting the energy from the surface AND around it... so maybe you get 40% total surface (including non occupied space).
BTW, solar energy is cost-effective today in spain, for example (and without tax subsidies). We are paying 0.18€ Kw/h and PV cost is 0.06€ to 0.12€, all costs included (varies wildly).
Yes, people are negative about PV, but seems obvious that regardless of any significant break-through like nanowires (and there has been a stream of similar stories about breakthroughs that later fail to scale up to bulk manufacturing and distribution stages), that slow and gradual improvements in cost and/or efficiency offset against rising electricity prices means that PV will increasingly become cost-effective to supplement other forms of generation.
Just read this Australian story moments before reading the Reg article on the nano-wires:
"Since the last hot summer in 2010, our electricity system has seen a lot of changes. For one thing, almost 2 gigawatts of distributed generation has been added in the form of domestic solar PV. To put that in context, 2GW represents a touch under 10 per cent of average summer demand"
At the moment, the thing that deters me from installing PV at home, is the cost and complexity around inverters and metering more than the cost and effort around the panels themselves.
"At the moment, the thing that deters me from installing PV at home, is the cost and complexity around inverters and metering more than the cost and effort around the panels themselves."
So management costs, not technology costs.
BTW you might like to look at these hybrid PV/water heating panels as PV efficiency falls about 1% for every 4c rise in temperature
WTF just isn't enough when you get stupid responses like this.
Those 'hours of darkness' cover the off-peak period of 23:00 to 07:00, (when I get reduced rates) as that is when lowest usage occurs. Not much solar needed then.
This might of course change if we get more electric cars plugging in over night, but for now appliances and lighting (LED/Compact Fluoro ) used at night are becoming more efficient, and less people are using electric ovens to cook meals at home. Looking at overall demand (not just residential), business peaks tend to be during the day with the cost of refrigeration and air-con.
The study I linked to in an earlier post, shows that in Australia and in other areas like the southern US, air-con is the biggest draw during the day. By the time dusk comes and PV energy drops to nothing, transition should be smooth to baseline hydro/geothermal etc + gas plants which can spin up quickly and meet any shortfalls, but the gas plants you want to run them for as few hours as possible - and mass, distributed PV helps that, as well as reducing peak air-con load in summer.
Like It's always good to have some kind of upper or lower limit for an algorithm so you can stop wasting time looking for better (because there isn't one) but it's good to revisit those boundaries to confirm they really are boundaries.
And in this case they are not.
Note this limit applies to single layer PV cells. If you stack 2 or more different sets of semiconductors you can (so far) hit 43% total. But they are hellishly expensive (built for comm sat use).
How practical this research is remains doubtful. Upside is you push the maximum limit on a single layer PV. Down side is you add tricky nanowire fabrication (UHV chamber needed?) and I'm not clear if the spacing between the wires writes off that area of the cell for light collection. Incidentally resonance
implies an object with electrical dimensions close to the exciting photon, which suggests this is a narrow band improvement. Of course if that narrow band is at the peak solar wavelength (around 500nm, unfortunately Silicons band gap is around 1100nm) that could be quite a useful difference.
" If you stack 2 or more different sets of semiconductors you can (so far) hit 43% total. But they are hellishly expensive (built for comm sat use)."
That's going to change. Not because I know anything at all about electronics but because I do know something about metals and fabrication. There's no particular reason why multilayer semis should be hellishly expensive. It's just that we don't know how to make them cheap. Which is where silicon PV was, say 10, 15 years ago.
Price of silicon ingot has gone from $450 a kg to $17 a kg since then.
As an analogy....solid oxide fuel cells. They really are the bee's knees. But hellishly expensive as yet. The largest manufacturer currently (OK, well, two years ago still did) hand paints the cathodes onto the plates. The material they're painting on has a raw materials cost of $3,000 a kg.
It'll take a little time, expansion of the market, mass manufacturing etc. But moving from hand painting to thin film or vapour deposition is going to bring those costs per unit tumbling down, isn't it?
This is what will indeed happen to multilayer solar.
It isn't today, and it may not be by next Thursday even, but, living in a place where the sun shines 350 days a year, I am waiting for solar electricity to become really economical. Every advance, however small, will help.
For now, Maybe I just have one more reason to dream of Copper Nano Tubes?
I live in the here and now. A new 120 kwp facility nearby, which should deliver 329 kwh/day over the year - 138 kwh/d during winter - produced all of 52 kwh/d 71 winter days long. Around the river Aare, the biggest in Switzerland, it happens to be foggy in wintertime, most of the time actually, but the heroic promoters, builders, political overlords and supporting media artillerists bravely stood up against nature. The bravery is partly grounded on the assuredness that the electricity consumer has to pay the "solar" surcharge anyway - or else.
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