New Solar Power Material Converts 90 Percent of Captured Light into Heat
jacobsschool.ucsd.edu
jacobsschool.ucsd.edu
I believe the following articles are the ones on which this story is based: http://dx.doi.org/10.1016/j.nanoen.2014.06.016 http://dx.doi.org/10.1016/j.nanoen.2014.10.018 (behind a pay-wall unfortunately)
http://circuit.ucsd.edu/~zhaowei/Journals/Nano_Energy_Dylan_...
http://en.wikipedia.org/wiki/File:Albedo-e_hg.svg
The advance is not that they "reached 90%", that's absolutely trivial, and nothing to do with a "Solar Power Material". They seem to be claiming that their advance is a black material they can paint onto thermal pipes that is durable at 1000K for an extended period of time in Earth's atmosphere, made out of blends of nanoparticles.
"High temperature black paint created that lasts 5-10 years instead of 1 year, reducing maintenance needs for concentrating solar thermal" would be a more honest title.
That number is for photovoltaic cells converting light to electricity; the 90% in the article is for converting light to heat.
there are a number of 'spectrally selective coatings' already in existence with this unusual combination of emissivities, but they are all very expensive to produce.
the longer lifetime is useful too, but not so useful they bothered to mention it in the abstract of their paper.
the small particles mentioned are made of a silicon-germanium blend, although they claim you can use different semiconductors for this. they picked that blend because its bandgap is about a volt, so it absorbs photons of more than about an electron volt.
Black chromium plating (absorption 0.87, emission 0.09) is often used for this purpose. It can handle the temperature, tolerates thermal expansion, and, like most hard chrome plating, is a hard plated surface that can be cleaned aggressively, as with pressure washing. There are other black coatings with up to 0.99 absorption, but they aren't as tough.
So what this new work has done is improve performance from 0.87 to 0.90.
(Why are so many "nanotechnology" articles like this? The title and lede sound like it's some earth-shaking development, and then it turns out it's at best a minor improvement.)
Electricity is like steak, heat energy is more like hamburger. It's useful but not nearly as useful as electricity, so you're going to need another conversion step (steam turbines are best at this right now) to get to a more usable form of power and that conversion step will have losses (radiation losses, mechanical losses, electrical losses).
So 'overall' efficiency is the key, not the efficiency of a single step in the process (they should at a minimum then list their current efficiency next to the previously achieved maximum for that step and how cost effective this new method is).
Lonnie Johnson's JTEC is an interesting looking approach for that bit - http://en.wikipedia.org/wiki/Johnson_thermoelectric_energy_c...
Also my inner steampunk geek will love the sight of huge sterling engines moving around ...
And if you have a nice source of heat, it could provide a nice A/C without requiring electricity (http://en.wikipedia.org/wiki/Einstein_refrigerator)
What heatpumps do is transfer heat from one place to another while using electricity. And they have some nice limitations on temperature operating ranges.
This never gets close to over 100% efficiency because of the laws of thermodynamics.
> The new material can also withstand temperatures greater than 700 degrees Celsius and survive many years outdoors in spite of exposure to air and humidity.
For simplicity, lets assume that it's 723°C (1333°F), and there is a nice summer afternoon and the environment temperature is 23°C (73°F). In Kelvin, we have 1000K and 300K.
By the second law of thermodynamics, we have that Q_in/T_in < Q_out/T_out,
so Q_in/1000K < Q_out/300K
then Q_out > 3/10 Q_in.
At least the 30% of the heat that enters has to be released to the environment in some type of cooler. So the efficiency of the heat to electricity conversion is at most 70%. If we multiply that by the 90% efficiency of the light to heat conversion, we get at most 63%. (65% in a cool winter morning :) ).
The Wikipedia article is not very clear ( http://en.wikipedia.org/wiki/Energy_conversion_efficiency ), but I guess that in a real power plant, we'd get at most a 40% or 60% heat to electricity conversion efficiency instead of the theoretical 70%.
> As of 2008, the world record for solar to electric efficiency was set at 31.25% by SES dishes at the National Solar Thermal Test Facility (NSTTF).
The 90% * 60% number is probably very optimistic.
The Wikipedia article is also interesting, because it discuss that when the temperature is too high the heat receiver is an important heat emitter. I didn't thought about that.
[0] http://en.wikipedia.org/wiki/Solar_water_heating#Economics.2...
Though raising the heat exhaust to say 40 C only slightly changes the efficiency, from 70% to 68%.
I am deriving 33% of the energy used for heating our startup headquarters with a solar thermal system we rigged up out of cardboard and black aluminum foil. We are bootstrapping and the electric heat the building has is much more expensive per BTU than oil/gas.
Black aluminum foil will reach 156F in direct sunlight in December in Southeast Connecticut. I have read that black aluminum foil will convert 88% of light to heat. We have 50 square feet of these panels that spend every clear or partly cloudy day between 130-156F, warming the building through convection. On a clear day with an outside temperature of 27F our rig heats two floors to 61F. We are going to add another 50 sq. ft. of panels to attempt to reach 70F+
And the heat mass of the building keeps it warm for four hours after the sun sets. We have some large floor to ceiling windows and we installed the panels so they stand behind the bottom three feet of some of the south-southeast facing windows.
The total cost of our system was $94 and a couple hours of time.
If we owned the building I would install solar hot air panels (basically an insulated rectangular box with a plexiglass top and black aluminum foil tacked into the inside with an intake and exhaust) and run a couple air ducts into the building.
This building already had a solar hot water heating system, with two 4' x 8' water heating panels on the roof. This gives us much of our hot water.
We are awash in solar energy, and heating air with the sun is the cheapest and most efficient way of capturing it. Solar hot air is THE low hanging fruit of solar power.
The only downside with our system is that there is no energy storage. But that could be engineered easily. A concentrated solar trough connected to a buried large cement block or other heat sink could easily store a day or two worth of heat for night time and cloudy days.
55% of the days here are clear or partly cloudy and great for solar heating.
Update:
If you were wondering what we are doing in Southeast CT, we are participating in the first of what we are calling The Winter Startup Challenge, our own laid back, low burn rate version of Y Combinator.
My team rented a waterfront three bedroom house in a beach community for the offseason, October-May. Being the off season we got a great deal.
We have to leave May 31st. We have 8 months to develop the product and reach ramen profitability or get funding. The product challenges have been overcome, the prototype is being built, we have committed buyers waiting for the first production run. Five months left.
Heat is extremely hard to transport over longer distances without huge loss.
He's talking about installing solar devices to collect heat at the place of business/home and use it there. On-site creation (if you consider using sunlight creation) and consumption.
There is nothing stopping the creation of electricity/gas/etc and transporting that over long distances... while ALSO using solar devices at the business/home.
Why use electricity to heat water, when you can use the sun? Why run an electric heater when you can use the sun to provide some/all of the heat needed?
It's a great idea and he makes a lot of good points. If the engineering can be simplified and brought to the masses
Solar concentrators are typically massive and are relatively dangerous to operate. Especially if you do two axis concentration (I should know, nearly set my old office on fire with one...).
A residential scale solar parabolic trough could heat water to 160F to run through baseboard heaters in a hybrid solar/fossil fuel system.
It could also easily boil the water and turn it to steam, its all about the size of the trough and the speed water is moved through it.
This new material seems like an improvement over the current tech in this type of setup.
The advantage of concentrated solar is that it can still generate usable heat on mostly cloudy days, where flat collectors certainly do not.
and 90% of all statistics on the Internet are made up. Unless you meant to say, "climate control" instead of space heating, this is just not true. You can't just take the "average" of what people use energy for in a country like the US, and expect it to be close to true for everyone.
For those of us living in the South, Southwest US (it was 65 and sunny here on Christmas day), energy usage is much higher for air-conditioning than for heating, and you can't just take a passive solar system and expect it to cool your house down.
Yes, passive solar heating can be great for some people, but not for everyone. Geography matters.
Solar thermal could be huge in the South too. If you can generate heat you can generate cold:
What I don't get is why thin aluminium foil is good for this. Don't you need a bigger heat absorber? Or is it surface area that's important?
The aluminum foil is cheap, and I found some anodized foil that is really dark for great absorption. Anodized black foil is much better than painting foil black.
I don't believe the total BTUs would be any higher if one replaced the thin foil with a 1" sheet of aluminum. An aluminum sheet with fins on the backside for heat dissipation might help, but I still think the total heat would be the same because the amount of energy hitting the surface is the same.
It is surface area and temperature of that surface that counts and we don't need fans because of convection.
If you take an infrared thermometer and take a reading off a baseboard heater you will see 140-180F temps radiating off the casing and the metal fins inside that are put there to increase surface area.
These flat panel aluminum foil based collectors work the same way.
When light/heat energy enters a room through the window some of it turns to heat and some is reflected back out the window. That is why you can see objects from the other side.
Seeing those objects is how we lose our heat. These collectors let us capture and convert a much higher percentage of the energy coming into the window already.
If you look at one of these collectors through the window from the outside it appears invisible almost, they are hard to see, nothingness from which precious free energy is harnessed and consumed and not allowed to escape.
If 90% of the captured energy is turned into heat, what is the other 10% turned into?
http://en.wikipedia.org/wiki/Hydrogen_production#Steam_refor...
http://www.livescience.com/49133-super-efficient-solar-energ...
I was unaware about the steady progress. Still far away from the 90+% thermal efficiency that is possible with solar heating.
My hopes on photovoltaics are on the relatively new contender Perovskite. Really nice to see the steep progress in efficiency there.
http://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit
Here's a better source URL:
http://www.jacobsschool.ucsd.edu/news/news_releases/release....
Any random black paint absorbs more than 90% of the light, and lots of black coatings survive 700°C.
You can find materials and substances that'll survive years at 700C although its non-trivial (not home depot, but no challenge for real engineering). And you can find materials and substances with ridiculous awesome IR profiles that are unfortunately incredible fragile or at least not "engineering useful" tough. But both characteristics in the same material is where the real story is. Its pretty cool.
There is another aspect of industrial scale use, not discussed in the weeks since the story came out, where for example, nickel oxide powder has some serious issues for lungs, and no one seems to know the toxicology of this new stuff. I donno where this stuff fits on the continuum of health, if its better or worse that your example of nickel oxides. It would suck if everything downwind turned into a superfund site, then again maybe its harmless as a charcoal bbq.
I guess a bad computing analogy would be its not very hard to find a low power computing device. Think of TI and microchip pic series of picowatt or nanoamp things. I've fooled around with the 10F220 series for no reason, "just because". And its not hard to find a computing device that does stuff really fast, any ole COTS desktop CPU or high end video card has interesting specs. But finding a processor that simultaneously uses nanowatts of power while making gigaflops of calculations, in 2014 anyway, would be pretty impressive. And getting a good ratio of flops/watt while being engineering-worthless isn't that impressive, but getting a good ratio of flops/watt while being engineering useful and deployable is really cool.
http://www.iflscience.com/technology/new-super-black-materia...
So yeah, this article is bull.
Those in charge still seem to be of a 'secure the oil and the heroin' and you rule the world.
Oh dear -> https://www.youtube.com/watch?v=xW3XeT7qavo
Fossil fuels also have the advantage of having extremely high energy density. They can be transported cheaply and efficiently and they store well. Electricity suffers large losses when being transported long distances directly, and batteries are significantly heavier per kWh. Batteries also degrade over time, are expensive to replace, and often require substances that can be as (or more) destructive to mine than oil is to burn.
http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
It's about 80% efficient and would probably get more so. So you can solve the storage and intermittency problems of non fossil fuel storage pretty simply.
Tesla has shown that batteries can be viable in some cases (e.g., passenger vehicles), but that is but a tiny fraction of the cases where the versatility, mobility, and energy density of fossil fuels are used. Virtually all other long-haul transport (passenger flight and cargo hauling for example) uses them exclusively for starters.
Nothing about transitioning away from fossil fuels is "simple", and it's likely to involve a patchwork of partial solutions[2].
[1]: http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-stor...
[2]: http://physics.ucsd.edu/do-the-math/2012/02/the-alternative-...
When there's a dense network of battery hot swap stations, then perhaps.
We don't have good storage for electricity at the scale that is needed, not within few orders of magnitude, so at all times energy produced must be equal to energy used (the available storage is insignificant globaly, it is very expansive and is limited by geography - basicaly we can pump water upstream and let it flow back through turbines - this is only possible when you have a lot of water and some place much lower, where it can safely go, and it's still not cheap).
Additionaly each transmission line has maximum capacity and it will destruct itself if you try to send more.
With old-style energy sources we had baseload produced by water dams, coal, gas and nuclear plants, and peak load produced by plants that can be quickly (in less than 30 minutes) switched to produce more or less energy depending on demand - these are usually gas or coal powerplants. So with average demand for X, and peak deamd of Y you need X of stable powerplants and (Y-X) of controllable powerplants. Network is designed around that Y, using assumptions that power is divided into smaller and smaller lines from source to destination.
Only thanks to that, and to accurate predicting of demand by each level of power distribution hierarchy (I know about details of Polish system, but I guess it's similar everywhere) - the system works.
If you just swap 1000 MW of coal/gas/nuclear baseload plants with on-average 1000 MW of photovoltaics or wind turbines - you will literaly destroy your energy network. Half of the time it will produce too much energy (which results in blackouts and costly repairs), the rest of the time you will have blackouts because of not enough energy produced. You need to prepare infrastructure for that.
You need to adjust the whole network to bigger load, and to change the network topology from "connected stars" to peer-to-peer (or at least orders of magnitude more stars, connected orders of mganitude more intimately), and you need to expand the transmission lines a lot, because the only way to provide baseload with renewables is to average out production from a lot of places with different weather.
Right now electric networks aren't designed for that, and upgrading the whole infrastracture is going to be very expansive.
Germany is trying to do that - props to them, but in the meantime they are kinda problematic to their neighbors, because when they cannot deal with excess energy produced by renewables - they dump in on Polish, Czech,etc networks. Germany needs to pay for that (too much power is exactly as bad as not enough power - Polish and Czech controllable powerplants need to adjust production because of that and it costs both ways, also routing the power through the lines need to change because some lines may exceed capacity with that additional energy, and that cascades through the whole network. Energy distribution is organised in such a way, that when somebody predicted demand or production wrong - they pay for the rebalancing of network caused by that.
Sorry for wall of text...
Interesting about German energy production.
>CSP power plants create the steam needed to turn the turbine by using sunlight to heat molten salt. The molten salt can also be stored in thermal storage tanks overnight where it can continue to generate steam and electricity, 24 hours a day if desired, a significant advantage over photovoltaic systems that stop producing energy with the sunset.
For example, if you have tanks big enough to hold a week or so of drinking water, then as long as you produce more than a weeks drinking water per week, you're all good.
This applies to almost any process that requires energy that is either a long term average or you can store in a tank. Electro-refining copper (good luck keeping aluminum cells warm, lol) or pumping irrigation water into fields. I would imagine you can solar distill ethanol whenever you feel like it, more or less. Given big enough tanks, you could generate chlorine for anything from swimming pool size to municipal water system size. A country needs X megatons of ammonium nitrate fertilizer per season and yes all of it is made today from natgas, but you could theoretically make it from solar power, air, and water, as long as the long term average power generated is high enough to make enough fertilizer per year.
Some industries like aluminum refining and some chemical plant work have a batch or shutdown time longer than the average weather related issue, so for basic chemistry scientific reasons they're screwed and will always require coal powered electricity, but most others theoretically only need a couple minutes of UPS power to shut down. Because electrical power is now super cheap, there are industries that have not put the slightest engineering effort on it... think CNC machinery, where there's no scientific reason a machine can't enter "sleep mode" within seconds, and return to work in seconds after sleeping, although in practice no one has ever made or shipped a machine like that, that I know of. As a simple example there are very few gcode programs that don't involve a dwell or toolchange where it could simply sleep in the middle of it, aside from the more difficult task of interrupting a cut. I guess this is an awesome industrial startup idea, not just for CNC machines but numerous other industrial machines. (And edited to add, there are numerous 3rd world areas overseas and California where the coal powered electric grid is totally unreliable, and machines that respond cooperatively to power interruptions would be quite handy even if there's no solar or wind generation involved.)
The biggest challenge to solar powering those industries is going to be non-renewable energy is very cheap compared to long term capital costs, so if its cheaper to run on diesel than to let it sit while continuing to paying the bank loan, or if your competitors can out produce you because they're not sunlight limited, then they'll have to run on diesel or coal-based electricity for financial department reasons, even if its no engineering challenge at all to run on intermittent solar power.
> good luck keeping aluminum cells warm, lol
There was article on hackernews recently about exactly that: https://news.ycombinator.com/item?id=8666681
> Because electrical power is now super cheap, there are industries that have not put the slightest engineering effort on it... think CNC machinery, where there's no scientific reason a machine can't enter "sleep mode" within seconds, and return to work in seconds after sleeping, although in practice no one has ever made or shipped a machine like that, that I know of.
Big power consumers even now can enter "consumption reduction offer" market. They provide offers that they will reduce consumption by 1 MW between 11:00 and 13:00 at thursday, and when electric network needs rebalancing - distributor buys these offers from them (often at many times the regular electricity price) because it's cheaper to slightly reduce consumption here, than to pay someone else to power on a whole new powerplant block elsewhere and send the energy longer way around just because at one point in the network there's not enough transfer capacity for a few minutes.
There's a whole exchange market, allowing to publish these offers on consumers side, and buy these offers on distributor side, and regular traders doing brokering beetween them, even some automated trading systems, you can even buy futures based on that :). It is quite elegant system - using free market + some regulation to solve allocation and prediction problem.
This, with law support for smaller consumers (and serious automation, because consumers wuldn't want to spend their time trading energy) could make these changes (quick sleep/wake modes) profitable, even if the energy savings alone aren't enough to justify it.
In the end new washingmachine etc could be connected to internet, automaticaly publish such offers when you switch them to energysaving mode, and react when someone buys its offer.
I think EU wanted to expand these regulations to allow regular consumers to participate, but I don't know how advanced it is (I changed job and no longer work on energy trading systems).
The goal is to substantially reduce the CO2 being pumped into the atmosphere, not to just talk about how People Like Us are better than Those Fossil Fuel People, right?