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Harvesting Energy From Humidity

Soulskill posted about two weeks ago | from the it's-not-the-heat,-it's-the-dizzying-electric-shocks dept.

Power 89

rtoz writes: Last year, MIT researchers discovered that when water droplets spontaneously jump away from superhydrophobic surfaces during condensation, they can gain electric charge in the process. Now, the same team has demonstrated that this process can generate small amounts of electricity that might be used to power electronic devices. This approach could lead to devices that can charge cellphones or other electronics using just the humidity in the air. As a side benefit, the system could also produce clean water. The device itself could be simple, consisting of a series of interleaved flat metal plates. A cube measuring about 50 centimeters on a side — about the size of a typical camping cooler — could be sufficient to fully charge a cellphone in about 12 hours. While that may seem slow, people in remote areas may have few alternatives.

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89 comments

Electricity & Water? (1, Funny)

Anonymous Coward | about two weeks ago | (#47461557)

Could we place banks of these along the US / Mexico border at aid stations so that incoming immigrants can stop and hydrate and recharge their cell phones?

Re: Electricity & Water? (0)

Anonymous Coward | about two weeks ago | (#47461765)

That would be cost effective. No, the whole point of illegal immigration is to break the tax payers back while simultaneously create a whole class of dependents. And just like the test of South America, the North shall two be broken up into the 'Haves' and 'Have nots'.

Re: Electricity & Water? (0)

Anonymous Coward | about two weeks ago | (#47462605)

"Shall be"?

Re: Electricity & Water? (0)

Anonymous Coward | about two weeks ago | (#47462699)

No, the whole point of illegal immigration is to break the tax payers back while simultaneously create a whole class of dependents.

Wrong. The point of illegal immigration is that after they settle down, become citizens, and register to vote, 90% of them with vote Democratic.

Re: Electricity & Water? (0)

Anonymous Coward | about two weeks ago | (#47463771)

A class of dependents implies voting Democrat. We are in an agreement here.

Re: Electricity & Water? (0)

Anonymous Coward | about two weeks ago | (#47471397)

I'm not American, and even in my home country, I'm not partisan.

But as near as I can see, the history of repeated Republican and Democratic legislatures and executive in the US have a consistent trend from the past few decades: deficit financing. Since the mid-70s, the closest thing to a leveling in outstanding debt came during the Clinton administration, though I don't know who controlled Congress at different times during his tenure.

When a Republican President and Congress actually reign in the deficit financing, for real and not just in rhetoric, then criticism of the Democrats will be meaningful.

The US is dependent on many countries, incl. its most powerful enemies, for money to pay the bills. That's world-class dependent. And both parties love being part of that class. One pretends to hate it more than the other.

Moisture Farmers! (2)

Commontwist (2452418) | about two weeks ago | (#47461577)

Power and water to produce... more power and water? Hmm... I wonder how much this could scale up

Re:Moisture Farmers! (1)

Commontwist (2452418) | about two weeks ago | (#47461735)

To be clearer: if a temperature difference can start the power generation in a humid area, can the power generated be enough to power an air conditioner to cool down enough air to extend the duration of the water condensation when the metal gets too warm and needs to be cooled? I doubt that it would allow perpetual water production but would the extra cooling allow it to extend the condensation process and power generation any significant degree?

Re:Moisture Farmers! (0)

Anonymous Coward | about two weeks ago | (#47461869)

It might be enough to pump cold water out of the ocean to keep the process going. Ultimately if you can generate clean water, even if there is no net energy it would be huge.

Re:Moisture Farmers! (2)

MrBigInThePants (624986) | about two weeks ago | (#47462071)

Err....

0.5m cubic of spaced sheet metal to charge a phone in a mere 12 hours and produce x litres of water.

Why on EARTH would you want to scale this up??

Perhaps on a distant, humid planet far from the sun?

Re:Moisture Farmers! (1)

viperidaenz (2515578) | about two weeks ago | (#47462495)

Math fail...

0.5 x 0.5 x 0.5 = 0.125 cubic metres.

Re:Moisture Farmers! (1)

MrBigInThePants (624986) | about two weeks ago | (#47463969)

I meant 0.5 cubed or in cube form. Brain fail...

PS: Nerd! ;)

Re:Moisture Farmers! (1)

ozmanjusri (601766) | about two weeks ago | (#47463795)

Why on EARTH would you want to scale this up??

You could use windtraps to increase humidity and use the electricity to pump the resulting water to your sietch water stores. Maybe not necessary on earth now, but who knows...

Re:Moisture Farmers! (1)

cdrudge (68377) | about two weeks ago | (#47465647)

If it takes 12 hours to charge a cell phone, I'm not sure how much water you'll be pumping in the same time period.

Re:Moisture Farmers! (1)

gl4ss (559668) | about two weeks ago | (#47464363)

well a shipping container sized thingy cold power an ordinary house if it scales up.

if you can get cool from somewhere I suppose for the condensation?

is it more efficient than peltiers for temp difference power generation?

Re:Moisture Farmers! (0)

Anonymous Coward | about two weeks ago | (#47466347)

well a shipping container sized thingy cold power an ordinary house if it scales up.

if you can get cool from somewhere I suppose for the condensation?

is it more efficient than peltiers for temp difference power generation?

A 20' shipping container has 33 m^3 on the inside. That means about 264 of these cell phone chargers could fit inside. Presuming they generate about 1/2 watt (which is generous, to charge a cell phone battery in 12 hours requires about 1/3 watt since they hold between 4 and 6 watt-hours, but i will give them the benefit and say that the phone is on, consuming the other fraction of a watt). So, 132 watts... that's enough for a collection of LED room lights and maybe either a slow cooker or refrigerator (if you shut your lights off) so say goodbye to any sort of HVAC.

Re:Moisture Farmers! (1)

MrBigInThePants (624986) | about two weeks ago | (#47471759)

No, no it couldn't.

And again, sheet metal plates in cube form.....not exactly cheap....

uhh yeah they do... (5, Informative)

Anonymous Coward | about two weeks ago | (#47461589)

its called a solar panel. it'll charge your phone in about an hour

Re:uhh yeah they do... (0)

Anonymous Coward | about two weeks ago | (#47464559)

S...e...a...t...t...l...e might benefit.

I know Seattle gets sunlight, but for places that don't, or at night, why not?

Re:uhh yeah they do... (1)

Thanshin (1188877) | about two weeks ago | (#47464565)

Unless you're inside a cave; both humid and dark.

This might be less-useless to maintain a small underground device, like a sensor to detect floods in a sewer system.

Re:uhh yeah they do... (1)

Namarrgon (105036) | about two weeks ago | (#47464767)

You'll need a much larger panel than 50cm to charge it that fast. And sunlight. This device should work day & night, regardless of weather.

Oblig. StarWars (5, Funny)

psybre (921148) | about two weeks ago | (#47461613)

"What I really need is a droid who understands the binary language of moisture vaporators."

Re:Oblig. StarWars (0)

Anonymous Coward | about two weeks ago | (#47461719)

Which rather makes little sense, as you'd want to condense moisture if you intend to collect it.

Re:Oblig. StarWars (1)

Livius (318358) | about two weeks ago | (#47461781)

Maybe you vaporise it at night when the ground is cold?

Re:Oblig. StarWars (2)

SuricouRaven (1897204) | about two weeks ago | (#47461783)

Did you see any crops on the surface? It might be a humidifier for an indoor farming area.

Re:Oblig. StarWars (4, Funny)

demonlapin (527802) | about two weeks ago | (#47462377)

What you're saying is that Owen and Beru were running a massive grow op?

Re:Oblig. StarWars (1)

ahaweb (762825) | about two weeks ago | (#47462405)

Makes as much sense as Lucas's claim that the robots flying around on Mustafar in Revenge of the Sith are "energy collectors", collecting energy from the lava. Because they are hot, I guess. So you want to collect ... the lava because it is hot.

Re:Oblig. StarWars (0)

Anonymous Coward | about two weeks ago | (#47466389)

Makes as much sense as Lucas's claim that the robots flying around on Mustafar in Revenge of the Sith are "energy collectors", collecting energy from the lava. Because they are hot, I guess. So you want to collect ... the lava because it is hot.

12 parsecs. Kessel run, 12 parsecs. LESS than 12 parsecs, even. Boom, mind blown.

Dehumidifiers that PRODUCE power?! (2)

GenaTrius (3644889) | about two weeks ago | (#47461617)

I'm from Florida and I'll take 30.

Re:Dehumidifiers that PRODUCE power?! (1)

RabidReindeer (2625839) | about two weeks ago | (#47462465)

I'm from Florida and I'll take 30.

It's like bringing matches to a gasoline refinery.

moisture farms? (1)

halfEvilTech (1171369) | about two weeks ago | (#47461619)

Are these modeled after the moisture vaporators used on the moisture farms of Tatooine

Re:moisture farms? (0)

Anonymous Coward | about two weeks ago | (#47461943)

They're the reason you don't see power cables spread throughout the Dune Sea

5 Years Away (1)

Anonymous Coward | about two weeks ago | (#47461681)

the amount of power produced was vanishingly small â" just 15 picowatts, or trillionths of a watt, per square centimeter of metal plate. But Miljkovic says the process could easily be tuned to achieve at least 1 microwatt ... per square centimeter.

This is another "5 years away" technology. I'll believe it when I see it.

Also, how did they calculate that? My phone's battery contains about 1000mAh at about 3.5V, or 3 joules. To charge that in 12 hours, you'll need 250000 square centimeters, or 50000 square centimeters per cube side, which comes out to larger than 2 meters cube.

They talk about making it smaller by having a large internal surface area, but I do not believe their fins-on-a-radiator strategy will work, since the moisture would condense near the edges of the fins that are exposed to open air, and the air reaching the middle wouldn't have any moisture left to condense.

Re:5 Years Away (1)

viperidaenz (2515578) | about two weeks ago | (#47462531)

... unless the cube is made of 10 50cm square sheets 5cm apart.
Then you've 50,000cm2 of surface area in a 50cm cube.

Re:5 Years Away (1)

mikael (484) | about two weeks ago | (#47462795)

They would need to increase the surface area of the plates, probably using three-dimensional fractals. This would increase the ratio of surface area to volume in the same way that human lungs or fish gills work.

Re:5 Years Away (1)

Bengie (1121981) | about two weeks ago | (#47467871)

A joule is a watt second. a 3.5v 1Ah battery will supply 1 amp @ 3.5v for 1 hour. That is 12,600 joules. I could be wrong, I'm great at making minor math errors.

meh (1)

djupedal (584558) | about two weeks ago | (#47461745)

"While that may seem slow, people in remote areas may have few alternatives."

''few' as in this device but no bug spray or cookstove, or few as in near death, out of water and food with only one magic wish left?

dont use a cell phone (0)

Anonymous Coward | about two weeks ago | (#47461761)

certainly not fandroid or Yphone

Re: dont use a cell phone (0)

Anonymous Coward | about two weeks ago | (#47462161)

I bet you're a riot at parties.

Where? (3, Insightful)

Red Herring (47817) | about two weeks ago | (#47461785)

At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours. Tiny cell phone battery. Heck, a tiny lithium coin cell will provide ~150mWh.

For contrast, a typical solar cell will give 130W/m^2 (-ish), so a 0.25m^2 solar cell will provide ~33W, while the sun shines, obviously.

I'm not sure where exactly on Earth is sufficiently "remote", dark, moist, and unreachable that this makes sense. (Yes, I though of that, but it's really uncomfortable to fit a camping cooler there...)

Re:Where? (1, Funny)

Mr D from 63 (3395377) | about two weeks ago | (#47461931)

I'm not sure where exactly on Earth is sufficiently "remote", dark, moist, and unreachable that this makes sense.

Thor's vagina.

Re:Where? (0)

Anonymous Coward | about two weeks ago | (#47462439)

I'm not sure where exactly on Earth is sufficiently "remote", dark, moist, and unreachable that this makes sense.

Thor's vagina.

You mean this [time.com] Thor, right?

Practically speaking nowhere (1)

mveloso (325617) | about two weeks ago | (#47461973)

It's interesting, but practically speaking is it worth building a large, passive electricity and water generator in a cave system?

Not really.

OTOH, it would generate electricity forever, or at least until dust caked all the plates.

Re:Where? (3, Informative)

Ichijo (607641) | about two weeks ago | (#47462081)

At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours.

That's just one 50x50 cm plate. They're suggesting a 50x50x50 cm cube of stacked plates.

Re:Where? (1)

Actually, I do RTFA (1058596) | about two weeks ago | (#47462521)

At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours. Tiny cell phone battery. Heck, a tiny lithium coin cell will provide ~150mWh.

50x50x50 cm cube. Presumably they were able to fit (by your math) 5 plates in the cube.

Re:Where? (3, Insightful)

viperidaenz (2515578) | about two weeks ago | (#47462555)

A solar panel doesn't produce much clean drinking water.
.

Re:clean drinking water (1)

Technician (215283) | about two weeks ago | (#47467237)

With electrolisis and a fuel cell, only the gas carried contaminates could possibly contaminate the drinking water. For quanity and qualityproduced, I'll take the solar solution. The distances traveled and the amount produced are both quite small. In the solar solution, the volume would be much greater and due to the recombining of gasses, much less likely to transport pathagens.

Re:Where? (1)

afidel (530433) | about two weeks ago | (#47462947)

More like 30-60W/m^2 depending on if they're amorphous or poly-crystalline, most folks won't be buying 25+% efficient monocrystalline panels for charging their cellphone =)

Re:Where? (1)

Sobrique (543255) | about a week ago | (#47501077)

Solar panel by day, wind trap by night!

Cool (1)

Livius (318358) | about two weeks ago | (#47461809)

As in, you need some cooling to get the condensation happening.

Still, pretty neat to get electricity from it.

Re:Cool (1)

viperidaenz (2515578) | about two weeks ago | (#47462583)

So if it's hot a humid and this technology is integrated in to home heat pumps, they could dehumidify more effectively at the same time as lowering power consumption a tiny fraction?

The surface area of the heat exchangers in heat pumps is huge.

Just wait until you try and make a warranty claim (0)

Anonymous Coward | about two weeks ago | (#47461829)

The sales droid at the local Verizon store will state that your humidity powered phone has a no warranty coverage because it was subjected to humidity.

New, or just adapted from a story? (1)

Onuma (947856) | about two weeks ago | (#47461845)

Didn't Frank Herbert write of something similar to this in Dune? I recall small objects which collected water, but I don't recall whether they provided any sort of power generation in the process.

Re:New, or just adapted from a story? (1)

Solozerk (1003785) | about two weeks ago | (#47462111)

They didn't - they were 'simple' water collectors (such as, I think, already exist), providing a small amount of clean water at dawn but not generating any energy in the process.
This tech, however, would be a nice one to power the Fremen's stillsuits in the same universe - providing additional water from the atmosphere while at the same time powering the various pumps and recycling tech inside of the suit :-) though if I remember correctly Herbert described those as powered by the movements of the user.

Re:New, or just adapted from a story? (1)

Onuma (947856) | about two weeks ago | (#47462539)

Yes. In Children of Dune, Leto's stillsuit was sabotaged. They tampered with the pumps located in the heels, which would normally circulate water as the wearer walked through the desert.

Good call.

Good! (1)

anchor_tag (2971059) | about two weeks ago | (#47461899)

Now my fat sweaty body will actually be good for something... Eat It Mom!

Snow? (1)

phorm (591458) | about two weeks ago | (#47461953)

Would this work with snow? Sounds useful for Canada and other places that have snowy winters that aren't so solar-friendly. Won't help on an overcast-but-not-wet day though.

Few alternatives? (1)

CrimsonAvenger (580665) | about two weeks ago | (#47461981)

A cube measuring about 50 centimeters on a side â" about the size of a typical camping cooler â" could be sufficient to fully charge a cellphone in about 12 hours. While that may seem slow, people in remote areas may have few alternatives.

You're not going to be carrying this thing in a backpack, so it's not like you won't have a car to charge your cellphone.

On the other hand, you might be far enough out in the boonies that you can't get a car to where you are. Of course, the question then becomes "how are you using a cellphone when the nearest cell tower is 40 miles away"?

That aside, if my choice reduced to carrying a cube 20 inches on a side to charge my cellphone or eight extra cellphone batteries, I know which I'd pick.

Re:Few alternatives? (1)

mythosaz (572040) | about two weeks ago | (#47462501)

Arguably *something* like this could be placed remotely to power the search and rescue device at the end of a trail in a national park... It could spend months just making sure that it keeps its own battery topped of for when someone needs to signal for help.

Re:Few alternatives? (0)

Anonymous Coward | about two weeks ago | (#47462701)

Arguably, a solar panel would be more effective.

Re:Few alternatives? (1)

mythosaz (572040) | about two weeks ago | (#47462927)

I suppose that depends on the trail, but sure.

Re:Few alternatives? (1)

viperidaenz (2515578) | about two weeks ago | (#47462623)

What if that cube provides you with clean drinking water as well? Spare cellphone batteries won't do that.

What this means if it can scale. (1)

Stoutlimb (143245) | about two weeks ago | (#47461983)

Given that a low end cell phone charger is about 2 watts, 1 watt would be a fair performance assumption for that 50cm unit. That gives us an approximate 8 watts per mÂ. Scaling up, this means that a cube 5 metres on a side will generate a kilowatt of electricity.

How does it compare to a thermocouple (2)

American Patent Guy (653432) | about two weeks ago | (#47462043)

under the same conditions? That's what would really be interesting.

This new device needs a temperature differential and humidity to operate. A thermocouple only needs a temperature differential. The new device won't work anywhere where there isn't a humidity high enough to provide condensation (such as space).

It's a curiosity, but I'm not investing any money in it in the short term...

I know who could use this (1)

puppetman (131489) | about two weeks ago | (#47462099)

Quick, someone call Kickstarter and get iFind up and running again.

Florida (1)

ITEM-3 (3348273) | about two weeks ago | (#47462107)

So you're telling me that when I'm outside pouring sweat in the oppressive Floridian humidity, I can look down at my phone to see it's charging and for a brief moment not hate where I live? TAKE MY MONEY!

Re:Florida (0)

Anonymous Coward | about two weeks ago | (#47463271)

If you're living in Florida and not walking around in a t-shirt (optional), shorts*, and flip-flops (optional), you're doing it wrong. You should probably move to coastal California 'cause we have the best climate in the country. (Disclaimer: I grew up in Florida, and would like to return once I reach a point in my life that I can deal with the oppressive humidity through nudity. You can still build a house on a snow-white beach in some areas for cheaper than a studio in San Francisco.)

* Also optional in many places.

Yes (1)

X-Ray Artist (1784416) | about two weeks ago | (#47462193)

and you can create X-rays by rapidly unrolling scotch tape in a vaccuum. I don't see conventional X-Ray machines, let alone CT scanners, leaving the scene to make way for "Scotch Tape" X-Rays. I also don't see me getting rid of my USB charging cord to make way for dehumidifier chargers. It is interesting that people have found these things out though. It gives me hope that there is still enough inquisitive nature left for true innovation.

energy? (0)

Anonymous Coward | about two weeks ago | (#47462325)

did not know that water vapor has much energy to power small electrical devices. Thanks for sharing.

Re:energy? (1)

mikael (484) | about two weeks ago | (#47462811)

There are ways of measuring the speed of flowing water through the small magnetic fields created from dissolved metal ions in the water. These are enough to distort the local magnetic field and allow readings to be made.

Bad idea (1)

Tablizer (95088) | about two weeks ago | (#47462415)

This will not only trigger Global Drying, but Republicans will deny it's happening, making it hard to do anything about it, and Koch bro's will buy up moisturizer lotion companies to profit from it.

Alternative (1)

jklovanc (1603149) | about two weeks ago | (#47462421)

While that may seem slow, people in remote areas may have few alternatives.

Try this [biolitestove.com] or this [inhabitat.com] as alternatives.

Super hydrophobic (1)

Culture20 (968837) | about two weeks ago | (#47462507)

How much energy does it take to create a super hydrophobic surface?

Remote areas? (1)

jgotts (2785) | about two weeks ago | (#47462601)

Way too high tech for remote areas.

Bringing clean water to remote areas in Africa means using parts that can be sourced from those remote areas using skills taught in those remote areas or else it's back to dirty water in a few years.

Think about aliens crashing a ship on Earth. Where would we get the parts to fix it? Alien technology is worse than useless when it fails.

Re:Remote areas? (1)

sir-gold (949031) | about two weeks ago | (#47472653)

It's easier to fix alien tech if you are living in an alien junkyard.

I don't know about those areas specifically, but there are many extremely poor areas of the world that are drowning in 1st world waste like plastic bottles and broken electronics.
Maybe the solution could use those "resources"

Some of this already exists, like the 20oz-bottle skylight (fill bottle with water and 2 cap fulls of bleach, drill hole in tin roof, stick bottle half-way through, and seal it somehow) The end result is a bright light that fills the area like a light bulb, and lasts pretty much forever.

If this new hydrophobic layer could be cheaply painted onto bottle plastic, it would take care of a large part of the raw material cost, especially if the hydrophobic layer could somehow also be made from whatever chemicals are in those old electronics.

It's cheaper to make lemonade if life hands you free lemons.

dam (1)

rossdee (243626) | about two weeks ago | (#47463583)

dam! I wish I had thought of that

Stop! This could destroy the world. (1)

mtthwbrnd (1608651) | about two weeks ago | (#47463745)

Scientists have conducted simulations using super computers and whole bunch of formulas to test the impact that these devices might have on climate. Their research was inconclusive due to lack of funding but they say that it could lead to devastating planetary dryness and eventually global catastrophe. They are requesting another $10bn annually to continue the important research and have begun to lobby for Al Gore to become their fund raising spokesperson. Meanwhile a base of deniers is building who deny that these devices will cause any harm. They are all funded by big oil though and their opinions do not count.

Twist on a very old idea? (2)

BillX (307153) | about two weeks ago | (#47463981)

While the "water droplets spontaneously jumping off superhydrophobic surfaces" effect is interesting in itself, the mechanism of stripping charge from those droplets as they leave the apparatus sounds like a variation of the Kelvin water-drop energy harvester from 1867 [wikipedia.org] . In this case, rather than charge separation via the cross-connected cups, electric-double-layer charge-separation occurs between the droplet and the hydrophobic surface, causing the two to come away similarly unbalanced when the droplet jumps away.

Re:Twist on a very old idea? (0)

Anonymous Coward | about two weeks ago | (#47466871)

totally different principles. So no.

Funny (1)

sgunhouse (1050564) | about two weeks ago | (#47464237)

I gather that "remote areas" somehow excludes deserts? Amazing ...

Energy from Humidity (0)

Anonymous Coward | about two weeks ago | (#47465503)

This is news? Any good RF engineer or ham radio operators know that water droplets moving through the air develop static charges that cause interference. Every see the arc jump across an antenna connector when humidity builds up on the surface of a 60 foot vertical antenna and the droplets run down? Transfers all the electrical charge to antenna and then arc across the connection at the radio. Many a radio has been destroyed due to this effect. What about the high school science experiment where you take two soup cans, attach wires to them and bring the wires to within an 1/8 of an inch of touching and then drip water through both cans? Watch the spark you get out of that!

Some scientific discovery.

Re:Energy from Humidity (1)

WindBourne (631190) | about two weeks ago | (#47466835)

and yet, none used that to develop an energy producing system.

Few alternatives? (1)

rgbatduke (1231380) | about two weeks ago | (#47465855)

While that may seem slow, people in remote areas may have few alternatives.

Other than:

Solar power, at roughly $1/watt (and then "free" for 10-20 years), price falling on a nearly Moore's Law trajectory.
Wind power -- expensive, unreliable but simple technology and humidity isn't reliable either.
The entire panoply of standard sources -- coal, oil, gasoline, nuclear, hydroelectric, alcohol, diesel, methane... which we can deliver a variety of ways including simply delivering a small generator and fuel.

I would truly be amazed if a new, patented technology of this sort was within an order of magnitude -- or even two -- of the cost of a solar source superior in nearly every way, and there are very few places where the humidity is high, temperatures are reasonable, and the sun does not produce enough light to make this work. This is truly an edge technology unless they make it astoundingly cheap.

rgb

Re:Few alternatives? (1)

Maury Markowitz (452832) | about two weeks ago | (#47466009)

> Solar power, at roughly $1/watt (and then "free" for 10-20 years), price falling on a nearly Moore's Law trajectory.

Ummm, no. Current prices, all in and spinning the meter, is around $1.70/W. Those are the latest cross-US numbers.

> Wind power -- expensive, unreliable but simple technology and humidity isn't reliable either.

Whereas wind actually is about $1/W (same source, DoE) and has a CF of 30% as opposed to 15% for PV.

Both are inexpensive and work well. We need both, and are installing both faster than any other power source ever. 95GWp combined last year.

Re:Few alternatives? (1)

bluefoxlucid (723572) | about two weeks ago | (#47466869)

I really hate solar panels.

Concentrated sunlight into thermal generators is more efficient, cheaper to produce, cheaper to maintain, less toxic to produce, and so on. Europe? Parabolic reflectors focus light from an infinite-distance focal point to a fixed focal point, where you place a sterling engine or a salt tower.

For the home, you don't want all that conversion waste. Electricity is the last thing you want. You should have a solar hot water system with an evacuated tube collector--a set of 18 180mm tubes costs $450, and can keep a 150L hot water tank at 190F in the summer (92F outside temperature design spec, Baltimore) or 140F in the winter (Baltimore design spec of 14F or -10C). They're not that big: 2.75m^2 panel at 37-45 degree mounting taking up 1.75 square meters of roof space. You can shove multiple up there to far exceed your hot water needs.

With the solar water heat, you can pipe directly to your hot water tank with a set temperature of 160F. Use a thermostatic mixing valve so that hot water draws hot mixed with cold, providing 130F water or cooler. The hot solar loop will bypass when the tank's 160F, by use of a thermostatic bypass valve.

In the winter, a hydronic heating coil will circulate your hot water (down to 130F) through a hydronic heating coil in your air handler. In the summer, the solar heating loop passes through an absorption cooler, providing air cooling. Thus your direct solar heat powers your heating and your air conditioning, both. AC can use an electric or gas back-up; water heat back-up is also your central forced air heating back-up.

When both the hot water tank and AC are bypassed, the solar hot water loop is pumped through a reverse-flow cooler. This cooler exchanges its temperature (at above 80% efficiency) with the hot water loop temperature: if your solar loop is coming down at 190F, and your cooling loop is 150F, then your solar loop will become 150F and the cooling loop will become 190F. Some mixing can control the cooling loop to keep it hot (i.e. pump part of the hot water loop through it, so that the hot water loop maintains or continues to raise temperature). This prevents the solar loop from overheating without shutting it down (normal practice is to stop the pump and let the tubes get ridiculously hot; with normal polyethylglycol coolant, this becomes acidic).

The hot cooling loop powers the hot side of a Sterling engine, which is cooled by vent fan or ground cooling (in a basement, use the sump!). The sterling engine, of course, generates electricity!

So, in short: evacuated tubes on your roof heat your hot water, your space heating, and your cooling, directly, all by the use of a single plumbing line down to your basement or furnace room. A sterling engine (likely 20%-30% efficient, unlike 8% thermocouple--but watch for newer quantum tunneling junctions configured as thermocouples, in 12-15 years) converts any remaining solar energy into electricity.

Glass tubes. Plumbing. Thermostatic valves. Ethanol and water. Four small pumps--main loop, hydronic, sterling hot, sterling cool.

Old idea (1)

Maury Markowitz (452832) | about two weeks ago | (#47465973)

Really MIT? Stooping to ripping off the University of Dayton?!

http://books.google.ca/books?id=ZgEAAAAAMBAJ&pg=PA75

Re:Old idea (1)

WindBourne (631190) | about two weeks ago | (#47466797)

totally different. Daytons is a mechanical system. MIT's is not.

remote location transmission (1)

WindBourne (631190) | about two weeks ago | (#47466781)

Seriously, something like that would enable a transmitter and a camera to be set up. Where this could be useful is for fire, weather, geological monitoring. Heck, this could even be used to put simple digital telescopes up on 14K' tops and broadcast back.

Powerless dehumidifier (1)

John Bokma (834313) | about two weeks ago | (#47468543)

I live in an area with high humidity (~80% / 25C) and am wondering how well this would work as a dehumifier that uses no electricity. The one we own is rated at 400 Wh. We often run in daily for 2+hrs. Also, if this is effective I can see other uses, like drying clothes. Or a small set up that can provide 2-3 liters of potable water/day.
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