Slashdot Mirror
Super Soaker Inventor Hopes to Double Solar Efficiency
mattnyc99 writes "With top geeks saying photovoltaic cells are still four years away from costing as much as the grid, and the first U.S. thermal power plant just getting into production, there's plenty of solar hype without any practical solution that's efficient enough. Until Lonnie Johnson came along. The man who invented the Super Soaker water gun turns out to be a nuclear engineer who's developed a solid-state heat engine that converts the sun's heat to electricity at 60-percent efficiency—double the rate of the next most successful solar process. And his innovation, called the Johnson Thermoelectric Energy Conversion (JTEC) system, is getting funding from the National Science Foundation, so this is no toy. From the article: 'If it proves feasible, drastically reducing the cost of solar power would only be a start. JTEC could potentially harvest waste heat from internal combustion engines and combustion turbines, perhaps even the human body. And no moving parts means no friction and fewer mechanical failures.'"
It may be "oxidized" as in the opposite to "reduced". See also http://en.wikipedia.org/wiki/Redox
(I haven't RTFA to figure out for sure, but if they're talking "hydrogen" on one side of a reaction and "proton/electron" on the other, it seems plausible on first blush.)
News for Geeks in Austin, TX
The article doesn't say the device is good for 60%, it states IF they are able to design it to work with with high-temperature ceramics, and IF it is able to reach 600C, then CARNOT efficiency is 60%, of which this device will obtain some fraction.
I didn't see any details on how this is any better than century-old heat engine ideas, unless the solid state design allows dirt cheap mass production, in which case he might be onto something...
Normally I would agree with you here and while IANAP (Physicist) I think you are not interpreting what he is saying properly.
He's not saying he found a more efficient solar cell (a doubling of that would be high on the BS scale). He is stating that he has created a new evolution of the Stirling Engine http://en.wikipedia.org/wiki/Stirling_engine.
From what I've read he looks to be on the up and up but again IANAP. Obviously since he has yet to have a production model we need to take it with a grain of salt but it looks very promising. *Crosses fingers*
We have four boxes with which to defend our freedom: the soap box, the ballot box, the jury box, and the cartridge box.
From TFA
The engine does not require oxygen or a continuous fuel supply, only heat.
This might just mean that oxygen is not consumed, while it could also mean the system contains no oxygen.
But also...
On the high-pressure side of the MEA, hydrogen gas is oxidized resulting in the creation of protons and electrons... On the low-pressure side, the protons are reduced with the electrons to reform hydrogen gas.
Here it looks like the article describes the reaction: H => e- P+ => H
So I think you might be right: oxidize is equivalent to ionize
As I understand it, there's only a violation if that someone claims they can use ALL of the heat to do work (thermal efficiency of 1). If some heat is still being dispersed into a cooler temperature environment, it's still perfectly doable. After all, are you going to tell me you can't use waste heat from the ICE to heat up some water?
I'm not an expert in the subject (I'm an electrical engineer, so I've only gotten very basic freshman-level introductions to the laws of thermodynamics), but I think there's a well-known upper bound to how efficient recovery of heat to do work can be. Some googling led to wikipedia which tells me that upper bound is the efficiency of the Carnot Cycle. Apparently it's not quite possible to reach it, but you're not violating thermodynamics if you're below it.
Warning: Opinions known to be heavily biased.
That's a nice theory, but it doesn't actually work in practice.
There is a limit to how much water is naturally evaporated from the ocean each year (far, far less than we're dumping into it) and rained down onto solid ground. There is a limit to how quickly water absorbed by the soil will leech down into the aquifers it was drawn from (it takes centuries) and that's where most of our water supplies comes from.
And as for location, there's no place on earth where the rainfall would possibly exceed the needs of a densely packed urban population, without conservation. The troubles Atlanta is having are just a start. Being located in the desert merely brings the problem to the forefront more quickly.
Look at the farm-packed interior of the US, and you'll find ridiculous quantities of water being used, all drawn from a gigantic aquifer, which is now being dramatically drawn down, with no sign of replenishment. You're welcome to go tell them they're just imagining it, when they run out of water supplies.
I'd gamble that, over the next decade, cities all across the US will have to begin copying the water conservation measures that have long been in-use in the southwest. And if they don't, the cost of water is going to go through the roof, as the expense for finding new supplies, and building new recycling facilities, goes through the roof.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
No, I was merely pointing out that "oxidized" doesn't have to mean "oxygen" or "that crud you think of on old metal", that in fact there is a technical meaning to the term the average software engineer who took one freshman level science course a decade ago -- which may not have even been chemistry -- might not connect with. Ionization and oxidation/reduction are in fact closely related terms, which the wikipedia link was meant to illustrate. If you compare the two entries ("Redox" and "Ionization"), I think you'll see the connection. Describing the process as oxidation and the effect as ionization is not a priori incorrect.
News for Geeks in Austin, TX
This device runs on the same principle as a Stirling engine and it shares the same theoretical efficiency: (Hot temp) / (Hot + Cold temp), all in Kelvins.
According to TFA, their first prototype is limited to 200*c because of material concerns. If they were to draw ice-cold water from the deep ocean as the cold side, it could theoretically acheive 473 / (473 + 273) or 63% efficiency. They talk about future materials allowing a hot side of 600*c, which despite being nearly twice the absolute temperature would only raise theoretical efficiency to 76%. Some sort of exotic oxide ceramic that could run at 1500 or 2000K would only add another 10% or so.
What fraction of that efficiency this or other engines acheive depends on the design. I believe the most efficient toy stirling engines can reach 90-96% of Carnot efficiency.
This is why turbochargers are often used on high performance engines - it extracts extra energy from the exhaust flow and thereby raises the thermodynamic efficiency of the whole package. Typical exhaust gas temperatures (at the exhaust manifold) are on the order of 1500 degrees F, which is hot enough to do lots of work.
Less is more.
Issued 1 year ago, this patent describes this system in great detail. I am doubtful it can work. The electric current out of the hot end of the device is less than or equal to the current in to the cold end (since the H circulates and each passage thru either side consumes or generates one electron). To create more electric power out than goes in, the proton exchange membrane would have to create significantly higher voltages at high temperature than at low temperature. But I believe the membrane voltage is pretty much limited to the ionization potential of H, and that is not going to change significantly over temperature). Lonnie Johnson sort of weasel-words around this in column 4 lines 30-50 of the patent body. This glossing over of detail is, to me, the most damning evidence (I am a PhD physicist with 89 issued US patents).
It's a popular concept in some circles: Use affordable high-tech devices to let folks in the developing world have a better life.
An example are cell phones. They've brought connectivity to folks in even isolated villages who could not dream of getting a land line.
Or the "life straw," a simple, cheap, but high-tech gadget that filters the filth and germs from streams. It's literally a straw.
Or a simple solar-charged LED light. Hang it outside your hut in the day, bring it in at night so the kids can study or mom can make extra money doing piecework.
A sturdy, self-contained solar electrical generator could act as an adjunct for a decentralized high-tech low-budget infrastructure. You'd use it to charge cell phones, XO Laptops (and their adult equivalent), and so on.