Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Solar Power Minus the Light

ScuttleMonkey posted more than 8 years ago | from the green-energy-saving-green dept.

439

An anonymous reader writes "Popular Science is running a story about a small company trying to take advantage of all the global warming hype. Matteran Energy uses 'thermal-collection technology to heat a synthetic fluid with a very low boiling point (around 58F), creating enough steam to drive a specially designed turbine. And although a fluid-circuit system converting heat into electricity is nothing new, Matterans innovative solution increases the systems efficiency to a point where small-scale applications make economic sense.' Notably, this comes during a record breaking heat wave here in the US. So has the day finally arrived where I can run my AC off of all that heat outdoors?"

cancel ×

439 comments

Sorry! There are no comments related to the filter you selected.

Only solves 50% of the problem (5, Interesting)

chriss (26574) | more than 8 years ago | (#15774753)

Hm, looks simply like a small sterling engine or mini gas turbine used to drive an AC. They managed to make it cheap so it will be applicable in small installations, but both the sterling engine and the gas turbine (using a fluid in a closed circuit) require a temperature difference, so the machine would not be driven by heat alone. You'd have to cool down the steam after it had passed the generator to make it condensate to a fluid again and pump it back into the thermal collectors. The article does not mention how this should be done or where the energy for this should come from.

Power stations using closed fluid circuits (e.g. nuclear plants) use a secondary circuit to cool the first one after the steam passed the turbine. They are usually located near rivers for this. Larger installations for sterling engines can store heat during the day in a water tank and use the difference in temperature between the water and the surrounding cooler air during the night to drive a sterling engine. This obviously works best in areas where the difference in temperature between day and night is significant, i.e. deserts. I don't think it to be realistic to turn 1/4 of your apartment into a heat/cold storage just to drive the AC.

So in the end they made it cheaper, but inefficient (5%) even compared to solar panels (20%) without offering something that could replace a conventional AC. To achieve this you'd still have to build houses in a smarter way, e.g. isolate the walls from the inside and outside and use them as thermal storage. More energy efficient construction has been done for cold regions (where houses require almost no heating during winter when isolated well, the inhabitants' body heat is sufficient) and warmer regions (traditional buildings build with clay and wind-traps and smaller windows to the sunny side). So it is possible, but do not expect too much from our current architecture.

Re:Only solves 50% of the problem (2, Interesting)

NightRain (144349) | more than 8 years ago | (#15774772)

Presumably however, you'd at least be able to use the existing temperature difference to at least offset the cost of running the airconditioner? Obviously it's not a perpetual energy machine, so you'd lose out in the end, but it seems to me that at least it could use some of the cooled air that is otherwise just going to be wasted.

Re:Only solves 50% of the problem (2, Insightful)

thealsir (927362) | more than 8 years ago | (#15774793)

yeah it could use some of the energy from the air, key point. The machine doesn't have to be near 100% efficient, but the big question will be if it is efficient enough to be worth the added cost of purchase installation. That must always be factored in when piggybacking machines that take advantage of ambient energy onto fuel-driven machines.

Just use solar already... (1)

drgonzo59 (747139) | more than 8 years ago | (#15774827)

Solar pannels might just work better. Besides with solar if you have an excess you can pump it back into the grid which is just the perfect cure during the high power demand scorching heat weather.

Re:Just use solar already... (2, Informative)

Alioth (221270) | more than 8 years ago | (#15774845)

The trouble with solar is it's ruinously expensive. The surface area required generally isn't a problem for a house (use the roof), but when a solar panel costs £450 (about US $700) for a 120 watt panel, to actually get enough solar panel to do something like run your home becomes fantastically expensive. You'd need at least twice (preferably three times) the solar capacity that you actually use in many places, so you can store enough during the day for the night, and not be without power on a cloudy day. Just to run your desktop computer and monitor, realistically you'd need three of those 120 watt panels to avoid frequent power shortages. Even if the panels were half the price they are now, it would still be so expensive it would never actually pay back (monetarily - apparently the energy payback for a solar panel is about 6 years, and solar panels are typically guaranteed for 25 years) compared to just buying power from the electricity company.

our galactic stone-age (3, Insightful)

uioreanu (554486) | more than 8 years ago | (#15774950)

Solar energy is yet expensive, but it's easy just to look at the effects of the crisis in middle east over the fuel price to understand that we need to start thinking differently when we're talking about energy consumption. Most of the house devices we have could work just slower and consume half of what they do now; but this is a lesson we were not yet trained to learn.

Our story resembles more and more with some Age of Empires game where we start on an island, burn out everything there is to burn over there, and then have no more resources to build transporting ships.

Re:our galactic stone-age (3, Insightful)

antoinjapan (450229) | more than 8 years ago | (#15775193)

The middle east will own the solar age like they do the oil age now, they have the sand and the sun, and huge deserts to coat with panels. They're just waiting for the oil to go before they get started.

Re:Just use solar already... (1)

plantman-the-womb-st (776722) | more than 8 years ago | (#15775136)

Um, so? Pay a lot once and forget about it -or- pay a little at a time over th course of years and constantly worry if you'll be able to get enough.

Seems a simple choice to me.

Re:Just use solar already... (4, Interesting)

Alioth (221270) | more than 8 years ago | (#15775198)

I'm afraid it's a bit naive to think you can pay a lot for solar and forget about it.

The panels eventually do fail/wear out. They do last a long time - most are guaranteed to still produce 80% of their rated output when 25 years old. Cells will fail and will need replacing from time to time, and will be expensive to do. So you have to *keep* paying a lot time and time again. Also, you need somewhere to store the energy for later - home energy usage is pretty much the exact inverse of when the most solar radiation is available - where I live, you need the most electricity in the winter when it doesn't get light till 9am and is dark by 4pm - so you need to store the power during the day for your peak night time usage. The most cost effective way of doing this currently is deep cycle lead acid batteries (since you don't care about weight as it's in a building). Try pricing up enough lead acid batteries to be able to get you through a week of shitty, dark, rainy winter weather just when you need the power the most. Then realise you'll probably have to replace the whole set of batteries every 8 years (and that's optimistic). And factor in the energy cost to make and (preferably recycle) those batteries.

Solar is fine for running small things; I am considering it for running outside lighting and things like the pond pump - the whole thing only needs one 120W panel and a leisure battery, inverter and controller - and in the winter time when the solar energy isn't very abundant, I'm hardly going to need the power anyway. However, for serious microgeneration, at the current time the only halfway practical and affordable renewable energy source is wind, which is vastly cheaper - and when you need the power most, it also tends to be windy, so the energy availability actually matches domestic energy usage much better. Wind also has a much better energy payoff. The energy to make a typical wind turbine is generated by the turbine over a period of six months - it's more like 6 years for solar. Unless photo voltaic solar becomes vastly cheaper, it's simply a non-contender except for novelty value, even if you live in the desert.

Why? (1)

Ogemaniac (841129) | more than 8 years ago | (#15774853)

It is just cheaper to add a new gas or coal plant and update the grid. As long as this is true (and it will not be forever) people are going to choose the dirty way. PV costs several times what dinofuel does. This isn't what you want to hear but it is the truth.

Re:Why? (1)

Tatarize (682683) | more than 8 years ago | (#15774982)

Nuclear Please.

I want to breathe.

Re:Only solves 50% of the problem (2, Interesting)

lordcat (949055) | more than 8 years ago | (#15774789)

You want cool? bury it! The temperature underground tends to stay nice and cool, even during the heat of the summer... If you've ever lived in a house with a full basement... you'll know that during the summer, that basement is the coolest part of the house... Similarly, in the winter time, that basement doesn't get as cold as the rest of the house can... (obviously heat rises so if you heat the house the upper levels will get warmer quicker, but if you didn't heat the house the basement would be the warmest part from the radiant heat in the walls vs the radiant cold upstairs)... Either you should get a nice difference in temperatures between the surface and 10-20 feet underground (maybe less... and you should get a nice difference both durring summer and winter)... or you don't need the ac!

Re:Only solves 50% of the problem (1)

Alioth (221270) | more than 8 years ago | (#15774860)

Radiant COLD? No such thing.

Re:Only solves 50% of the problem (1)

Smidge204 (605297) | more than 8 years ago | (#15774947)

I beg to differ; If you make an object cooler that the surroundings, there will be a net radiative heat transfer from the surroundings to that object. It's been done.

The catch is, if you're going to use an existing radiant heat floor/wall/ceiling system, you have to keep the temperature of the surface above the dew point or things will get wet.
=Smidge=

Re:Only solves 50% of the problem (1)

Alioth (221270) | more than 8 years ago | (#15775143)

But that's still not radiant cold. You can't have a radiant cooler. If radiant heating is being done then it's the surroundings heating the cooler parts - the warmer surroundings are doing the radiating, not the thing that's cold.

Re:Only solves 50% of the problem (1)

bhima (46039) | more than 8 years ago | (#15775110)

Radiant cool: think like the floor and the walls of a fully underground basement

Re:Only solves 50% of the problem (5, Interesting)

Jedi Alec (258881) | more than 8 years ago | (#15774864)

this very principle is currently being put to use in a part of the Netherlands that used to be mined for coal. The water in the now abandonded mine-shafts will be used to provide heating in the winter and cooling in the summer.

Sig (2, Funny)

Poromenos1 (830658) | more than 8 years ago | (#15775074)

People replying to my sig annoy me. That's why I change it all the time.

Well, one can always quote it :P

Re:Only solves 50% of the problem (1)

Schraegstrichpunkt (931443) | more than 8 years ago | (#15774871)

What's the thermal conductivity of the ground? Even though the overall temperature of the ground might be cooler than the air, the area around the buried pipes will just heat up and reduce your temperature differential. The poorer the thermal conductivity of the ground, the larger the apparatus needed to exploit the temperature differential.

Re:Only solves 50% of the problem (2, Interesting)

Aceticon (140883) | more than 8 years ago | (#15775035)

Actually as you go deeper underground the temperature of the soil gets closer and closer to the average yearly temperature in that area as shown here [nrc-cnrc.gc.ca]

How fast the temperature approaches the yearly average as depth increases depends on the type (and moisture content) of the soil, but as a rough guide, at 8m depth the temperature is very close to the yearly average.

Note that this is not valid for extreme depth (or vulcanic areas) for the obvious reason ;)

BTW, the graphic was taken from here [nrc-cnrc.gc.ca] - if you want to know the depth at which the yearly variation of temperature has 1% of the amplitude of the variation outside, look for "Table I. Depth of Penetration of Diurnal and Annual Temperature Cycles" (sorry, no anchor in doc) and check the column "Depth Year (m)"

Re:Only solves 50% of the problem (4, Insightful)

MichaelSmith (789609) | more than 8 years ago | (#15774794)

Hm, looks simply like a small sterling engine or mini gas turbine used to drive an AC

Summer power consumption by aircon units determines max peak load on the power grid here in Melbourne, Australia. I think aircons should run primarily on photovoltaics because that way you get the highest power when it is needed the most.

Re:Only solves 50% of the problem (1)

Alioth (221270) | more than 8 years ago | (#15774872)

It would be nice, except for the cost. I bet a 120 watt solar panel costs around AU$1000 in volume. Even in a sunny place you're going to want at the bare minimum 10 of those panels per kilowatt you need, so by the time you're done you're going to be spending $200,000 on solar panels to run your house.

Re:Only solves 50% of the problem (1)

MichaelSmith (789609) | more than 8 years ago | (#15774935)

by the time you're done you're going to be spending $200,000 on solar panels to run your house.

I am thinking more about office buildings with unused roof space. If you write the building regs to require solar cells to run the aircon systems you will increase the economies of scale in solar cell manufacture and drive costs down overall.

Re:Only solves 50% of the problem (1)

squoozer (730327) | more than 8 years ago | (#15774963)

It will never happen and for one very good reason. There just isn't enough energy hitting the roof of even a moderate office block to power the aircon irrespective of the price of solar cells. Energy from the sun totals about 1kW per sq m. Look at amount of unused space on the roof mostoffice blocks. The amount of power you can generate simply isn't enough to power the aircon even if solar cells were 100% efficient. Even the best solar cell is 20% efficient and that drops with time (not counting the fact that huge amounts of power go into making a solar cell int he first place).

Solar cells have a loooooong way to go before they are worth it. Wind turbines on the other hand are nearly there.

Re:Only solves 50% of the problem (1)

ozmanjusri (601766) | more than 8 years ago | (#15775010)

There just isn't enough energy hitting the roof of even a moderate office block to power the aircon irrespective of the price of solar cells.

Except that energy hitting the solar cells now isn't hitting the roof. You should be able to turn the aircon off...

Re:Only solves 50% of the problem (1)

12WTF$ (979066) | more than 8 years ago | (#15775207)

Except that energy hitting the solar cells now isn't hitting the roof. You should be able to turn the aircon off...
Yes the solar panels will shade the roof, but they will radiate heat onto the roof. Solar panels are 14-17% efficient. Some of the other 80% of the light energy is converted to heat, enough so they run about 25C above ambient temperature. Solar panels are mounted at least 10cm (a few inches) above the roof so that air can flow freely to help cool the panels.

Re:Only solves 50% of the problem (1)

kfg (145172) | more than 8 years ago | (#15774985)

you will increase the economies of scale in solar cell manufacture and drive costs down overall.

"Economies of Scale" is not a magic wand you can wave to simply reduce cost to some level you would prefer.

We already make photovoltaics at or near the limits of economies of scale. They are just . . .plain . . .expensive to make. Innately.

If you're losing money per unit you can't "make it up on volume" either.

KFG

Re:Only solves 50% of the problem (5, Informative)

B2382F29 (742174) | more than 8 years ago | (#15774971)

Wow, that would be expensive. Here (germany) you get 2kW (10x200W) for 9000 EUR [energetik.de]

Next time please don't pull prices out of your ass.

Re:Only solves 50% of the problem (1)

Alioth (221270) | more than 8 years ago | (#15775120)

Why so hostile? The prices were "not pulled out my ass" but sample prices from a supplier of panels. You could have said something a little bit less rude such as "I think you're incorrect, we can get panels in Germany for this price here" instead of making a mindless flame that makes you look like an asshat.

Re:Only solves 50% of the problem (1)

Alioth (221270) | more than 8 years ago | (#15775130)

Additionally, before you flame also check your maths. EUR9000 per 2kW is still EUR 90,000 per 20kW - converted to AU$, that's still over $150,000 for 20kW - which I maintain is ruinously expensive for that much power.

You already have thermal energy (3, Interesting)

dbIII (701233) | more than 8 years ago | (#15775063)

I think aircons should run primarily on photovoltaics
Run them on heat instead - instead of having water in a rooftop solar hot water system you could have your airconditioning working fluid (eg. ammonia) getting hot then expand it through a nozzle to give you cooling. This gives you cooling with no moving parts and would use a lot less roof space than the photovolatics required to run an electric airconditioner. Electricity is not the answer to everything - it's a way to get energy from one place to another.

Re:You already have thermal energy (2, Informative)

Diamondback (111383) | more than 8 years ago | (#15775098)

That's so crazy it just might work. I always marveled at the propane refrigerators my parents had at our cabin - you boil something to make something else cold! Wow!

Solar-powered air conditioning, using no electrical conversion at all... brilliant.

Re:You already have thermal energy (1, Informative)

Anonymous Coward | more than 8 years ago | (#15775146)

As to heating something near an object to get that object cool:

An very old, now deceased, friend of mine used to tell me they would bury a six-pack in sand, pour fuel on it, and light the fuel, during WWII. The beer would then be cool enough to drink(for Americans who like cool beer). This always sounded a bit nutty to me, but I guess it worked.

If you try this and it works, make a toast to Carmine Mangano!

Re:Only solves 50% of the problem (1)

z0idberg (888892) | more than 8 years ago | (#15774804)

Perhaps this could be integrated into the hot water system so incoming cold water can be used to cool the condensate back to fluid and you get hot water out the other end.

Obviously you can only do this for a limited period (i.e. until your hot water storage limit is reached), unless once your hot water storage limit is reached you let the excess escape as steam. This wouldn't be ideal as you are losing fresh water out of the system but the benefit might outway that cost.

Re:Only solves 50% of the problem (1)

chriss (26574) | more than 8 years ago | (#15774817)

It's stirling engine [wikipedia.org] after Rev. Robert Stirling, not sterling engine.

Solves almost 100% of the problem (1)

Yetihehe (971185) | more than 8 years ago | (#15774876)

Main innovation here is that they removed feed pump, which makes whole thing more efficient at low temperatures. If their fluid boils above 58F, then it condensates below 58F. If it condensated just above outdoor temperature, then thermal collectors could heat it and normal outdoor temperature could make it condensate back. With such low temperatures however it's very inneficient to run a feed pump. They however have plan:
1. Eliminate feed pump
2. ??
3. Profit.

Deep in the earth... well not that deep. (3, Informative)

IBitOBear (410965) | more than 8 years ago | (#15774881)

On the average, the underground temprature at ten feet below ground level is something like 52 degrees. (I am looking into geothermal [q.v. ground-sourced] heat pumps.) If the fluid boils at 58 degrees and you put a reasonably large ground loop you would have your temprature differential.

Toss a solar collection array on the hot side, and if the latent heat of vaporation of the mistery fluid isn't too high you should be able to get a pretty flow.

You might need to pull-start it (8-) to get the initial pressure differential, but once the system was running the cost of using some of the energy to replenish the boiler from the condensate coils should be low enough.

It mostly comes down to a matter of surface area.

In a steam/turban plant the energy to move the turban doesn't _really_ come from boiling the water, it comes from super-heating the steam. You have to move the steam through the turban energetically enough to move the machinery (which cools the steam as the pressure is relieved (etc). So it isn't so much the boiling temprature, its how much energy the media can carry _after_ boiling. A lot of volatiles do an incredibly poor job as a (relatively, in this case) super-heated fluid because of crosiveness or viscosity.

ASIDE: If I were trying to build a solar-powered air conditioner I'd use basically the same material and design as a propane-fired refridgerator and a Clever Arrangement(tm) of concentrating mirrors. The whole system is low pressure and has no moving parts. The mirros would have to track, but those moving parts wouldn't ever have interract with the volatiles.

Re:Deep in the earth... well not that deep. (1)

Max von H. (19283) | more than 8 years ago | (#15775041)

in a steam/turban plant the energy to move the turban doesn't _really_ come from boiling the water, it comes from super-heating the steam. You have to move the steam through the turban energetically enough to move the machinery...

Steam-powered turban?? There's a few pakistani taxi drivers who might be interested ^^

Re:Only solves 50% of the problem (3, Funny)

bhima (46039) | more than 8 years ago | (#15774933)

"I don't think it to be realistic to turn 1/4 of your apartment into a heat/cold storage just to drive the AC."

I see you haven't met my ex-wife.

Re:Only solves 50% of the problem (3, Interesting)

Smidge204 (605297) | more than 8 years ago | (#15774966)

Photovoltaic panels get hot because they absorb all that sunlight with only ~20% efficiency. Install the heat exchanger in close proximity to the back of the solar cells to make use of this high temperature and take advantage of the shade it provides (prevent the heat sink from being heated by the sun as well. Now your microturbine may be only 5%, but that's effectively ~25% overall for the PV-turbine system combined.

Make that a concentrating PV and your efficiency increases for both systems.

Every little bit helps.
=Smidge=

Too little (1)

bWareiWare.co.uk (660144) | more than 8 years ago | (#15775185)

Even if you assumed that the 5% efficiency was constant at any absolute value (it is highly likely that it is 5% peek at some specific temperature) and the solar panel did not reduce the efficiency of your heat collector (it is also likely that a solar panel reflects and radiates more energy then a dedicated collector) then you would only get a combined efficiency of ~24% as the collector can't get the 20% the solar panels are converting
Either way solar is very rarely constrained by size, but rather cost of installation. I expect that in most situations installing a solar cell with 120% of the service area is more cost effective then installing another complex system that would need additional maintenance.

Re:Only solves 50% of the problem (1)

kfg (145172) | more than 8 years ago | (#15775004)

warmer regions (traditional buildings build with clay and wind-traps and smaller windows to the sunny side)

I've never lived so comfortably as when I lived in a traditional adobe house in a high desert region . . .at about 17 degrees north latitude. Simply lovely. Cool in the day when it was hot. Warm at night when it was cold. No heating, no airconditioning, but nearly always perfect for comfort.

Adobe, but built in a modern fashion, at sea level against the rainforest, not so nice at all; and the scorpions liked to hide in the tile roof during the day, and then drop down on you when when it got cold at night.

Location, location, location. Plus a bit of native engineering.

KFG

Re:Only solves 50% of the problem (1)

cheater512 (783349) | more than 8 years ago | (#15775032)

Yay now I can use the spare heat generated by my cpu, gpu, hard drives, etc... to power my computer!
Ok yes I know it wouldnt work but it could at least recycle part of that excess energy back in to running the computer.

no, it solves 100%, it clearly states ambient air (4, Informative)

_Shorty-dammit (555739) | more than 8 years ago | (#15775083)

it very clearly states in the animation at the company's website that ambient air temp is sufficient to cool it back down. You seem to be forgetting that those big black panels on rooftops that heat water using the sun's solar energy heat the water up to a much higher temperature than the ambient air is. What exactly would be the point of a solar water heater if it only gave you water that was the temperature of the ambient air? Anyway, so, you use that heat source to boil the liquid in the closed circuit. Don't forget, it ain't water. It's some liquid that boils at a pretty low temp. And then you use the ambient air for the heat exchanger to cool the 'steam' in the closed circuit back down, condense, and start all over again. So, from what I gather the only requirement for this to work is that the boiling point of the liquid in the closed circuit needs to be higher than the ambient air temp, and lower than the temp you can achieve from a device similar to / same as those rooftop solar water heaters. Then you should have no problem boiling or condensing that liquid, since you have the capability of getting the substance up to the boiling temp, and back down below that temp so it condenses again.

Re:Only solves 50% of the problem (1)

asc99c (938635) | more than 8 years ago | (#15775119)

Hm, looks simply like a small sterling engine or mini gas turbine used to drive an AC.
Well it's nice to know all those anonymous cowards are environmentally friendly at least.

Re:Only solves 50% of the problem (1)

hort59 (966434) | more than 8 years ago | (#15775165)

Of course it looks like sterling technology. Look at the name that patents are issued to - Jeffery Sterling. :)

Thermo (3, Interesting)

LesPaul75 (571752) | more than 8 years ago | (#15774761)

So has the day finally arrived where I can run my AC off of all that heat outdoors?
Ok... I'll be the first to admit I wasn't paying close attention when this was discussed in my college physics class, but something having to do with the laws of thermodynamics feels wrong here. :)

Re:Thermo (3, Interesting)

Umbral Blot (737704) | more than 8 years ago | (#15774783)

What's specifically wrong is this: to condense the steam back into a liquid you need something colder than its boiling point. Thus on a hot day you couldn't get it to condense, and thus it wouldn't work. What you really need is a a large heat sink, like the ocean or a big peice of ice, and then you could turn the tempertature differential into energy using this device (at the cost of heating up whatever cold thing you were dumping heat into).

Re:Thermo (1)

Fred_A (10934) | more than 8 years ago | (#15774788)

Well, you could put the condensing coil in your fridge. Problem solved !

(I know, just being silly)

Re:Thermo (4, Informative)

warewolfe (877477) | more than 8 years ago | (#15774849)

Energy is being extracted from the fluid circuit system and being converted into electricity. Steam re-condenses into fluid because it has lost it's energy to the turbine.

No perpetual motion or violation of the laws of thermodynamics involved, just energy transfer.

MOD PARENT UP (n/t) (1)

Schraegstrichpunkt (931443) | more than 8 years ago | (#15774880)

no text

ACTUALLY, MOD PARENT DOWN (0)

Anonymous Coward | more than 8 years ago | (#15775072)

Because he didn't explain shit, exctracting heat energy from a system doesn't work without a heat sink of lower temperature

Re:ACTUALLY, MOD PARENT DOWN (-1, Flamebait)

Anonymous Coward | more than 8 years ago | (#15775092)

Sure it does. Get yourself a can of canned air. Hold down the button.

Now, how cold does the can get? Think about where all that heat is going.

Incidentially, every reasonable airconditioner uses a compressor for the same principle, so that the air inside can be colder than the "heat sink" outside.

All that aside, other posters have already pointed out that you can use the ground as a heatsink, go down a dozen or so feet and it's usually cool enough down there. Plus, the planet is a mighty big heat sink. We should be able to pump a lot of heat into it before we have to worry about "global" warming.

cooling water needed (2, Informative)

Anonymous Coward | more than 8 years ago | (#15775085)

"Steam re-condenses into fluid because it has lost it's energy to the turbine....
No perpetual motion or violation of the laws of thermodynamics involved,"

Yes, perpetual motion or violation of the laws of thermodynamics involved. Plus, if you look at their website, that's not what they are claiming.

If you put the steam through the turbine, you now have lots of low-pressure steam that you can't get any more useful work out of. They are condensing the steam back into liquid using copious amounts of cooling water (see the condenser and motorless pump in their animation). You don't get energy for nothing.

Also, keep in mind that the article summary is a little misleading by mentioning that the liquid boils around 58F. They are actually heating the system up to 150F - they are _not_ running this at room temperature. They are simply arguing that it's easier to get 150F temperatures from natural sources (geothermal, solar) than the higher temperatures required for more traditional steam engines.

Re:Thermo (1)

Timmmm (636430) | more than 8 years ago | (#15775204)

That's just plain wrong. You need a temperature difference to generate electricity*. I.E. if he wanted to run AC from the heat outdoors, you would need a cooler (or hotter) place too in order to generate electricity. Using a hotter place is just a conventional power station, and if you *have* a cooler place, why do you need AC? Just connect your house to the cold place with pipes.

*If you don't believe me, read this: http://en.wikipedia.org/wiki/Carnot_cycle [wikipedia.org]

Especially: efficiency = 1 - (t_cold / t_hot)

Depends where you are, but very inefficient (1)

Flying pig (925874) | more than 8 years ago | (#15774882)

In many places in the world the deep soil temperature never reaches summer air temperature maximum. In such cases it is theoretically possible to use the Sterling cycle to obtain energy by, effectively, transferring heat from air into the soil. However, eventually this is going to stop working as the soil around the heat exchanger warms up. There is also the problem that the efficiency of a heat engine cycle is limited to 1- the ratio of output to input temperature. Since the ratio is rarely lower than about 0.95, and you need power to drive the fluid through the soil circuit - do the math. It would be much more effective to grow sunflowers or sugar beet and use the product in your bio-Diesel or bio-ethanol engine.

Re:Thermo (1)

stunt_penguin (906223) | more than 8 years ago | (#15774926)

How about using the ground, which stays cool even during hot summers. Geothermal heating/cooling systems draw heat from or sink heat in the ground or a body of water depending on whether they're being used for heating or cooling. In this case, you'd run the system underground and deposit your heat there. Obligatory Wiki [wikipedia.org]

Re:Thermo (1)

smitty_one_each (243267) | more than 8 years ago | (#15774987)

to condense the steam back into a liquid

Hm. PV=nRT, right?

Why not have a compressor somewhere removed from the thing you're trying to refrigerate?

With the right engineering/business model, that work could come from people on exercise bikes.

Attack power generation, fat, and unemployment problems in parallel.

This idea is too good to work in practice.

Re:Thermo (1)

Firehed (942385) | more than 8 years ago | (#15775008)

What you really need is a a large heat sink, like the ocean or a big peice of ice

I'm sure Al Gore will love you for suggesting that.

Celsius (1, Informative)

jakuis (816654) | more than 8 years ago | (#15774770)

That would be around 14,5 degrees for the rest of the world.

Re:Celsius (-1, Flamebait)

mccalli (323026) | more than 8 years ago | (#15774785)

Speak for yourself - it's 14.5 for this part of the world (UK). That's "fourteen point five". None of your continental commas here if you please, leave it for the thousands where God quite clearly intended it to go. :-) Cheers, Ian

Carnot efficiency. (5, Informative)

Anonymous Coward | more than 8 years ago | (#15774797)

58f = 14.4C or 287.6K

Now lets be generous and let our panel "superheat" the stuff up to 80C or so, and put the cold reservoir in a bucket of ice.

That gives us a heat source at 353.15K and a sink at 273.15.

Efficiency = 1.0 - cold/hot = 1.0 - (273.15/353.15) = 0.226, or about 23% efficient.

Not great.

it aint that great (4, Interesting)

hamburger lady (218108) | more than 8 years ago | (#15774799)

~5% efficiency.

what's wrong with a reflective dish and a stirling engine [stirlingenergy.com] , anyways? much higher efficiency, materials aren't as expensive as solar panels and not nearly as bad for the environment.

Re:it aint that great (2, Interesting)

chriss (26574) | more than 8 years ago | (#15774843)

The main problem with stirling engines and reflective dishes is that they consume a lot of space, most of which is the empty area between dish and engine. While they may be more efficient and their production be less hazardous to the environment, they cannot compete with solar panels which can be put on roof tops or basically any flat surface. Newer PV technology even promises "paint on" solar cells. They are simply less invasive and therefore can be put into more places, leveling their lower efficiency. For rural areas this may be different, but for cities PV wins.

Re:it aint that great (1)

hamburger lady (218108) | more than 8 years ago | (#15774904)

i'd say you'd have the same problem with the system in the story, with a turbine and all.

as for a stirling dish-solar system, they would work alright in the city; one would easily fit on the roof of my rowhouse (since a satellite dish would fit just fine). it actually has a smaller footprint, per kwh, than solar cells. however, if you're talking about the suburbs, you're right; solar roof shingles etc are a much more usable option.

Re:it aint that great (1)

dbIII (701233) | more than 8 years ago | (#15775108)

they cannot compete with solar panels which can be put on roof tops or basically any flat surface
There is the issue of scaling. If you double the area of photovoltaics you only get double the power output. If you double the size of a thermal power generation method you usually get more than double the output - which is why the idea is to build really big solar thermal power installations on bits of land no-one wants. This happens because you can use bigger turbines and more of them to get more out of the same temperature difference, and because losses such as friction become a lot less of the total percentage generated. This scaling up of thermal power as distinct from the additive output from photovoltaics is why the nuclear power industry always use it as a comparison - a really big thermal source doesn't have to be very cost effective to come out ahead of thousands of acres of photovoltaics (which would be a stupid use for them - there's plenty of other ways to use them). About the only nuclear power plant that didn't even come ahead of this ridiculously skewed comparison was the fast breeder Superphoenix - hundreds of acres of photovoltaics would have been cheaper per MW.

Solar powered Air conditioning (5, Informative)

Hal_Porter (817932) | more than 8 years ago | (#15774807)


Notably, this comes during a record breaking heat wave here in the US. So has the day finally arrived where I can run my AC off of all that heat outdoors


I guess you're making a perpetual motion joke, but the strange thing is it's not a daft as it sounds.

You could have an electrically powered heat pump to pump heat into the ground in summer, and back out again in winter.

http://www.igshpa.okstate.edu/geothermal/geotherma l.htm [okstate.edu]

Very popular here in Sweden.

If you insulate your house enough, the energy required to heat or cool it is pretty minimal, so you could generate it from solar panels, at least in the summer. And heat pumps are 3 to 4 times more than resistive electric heaters.

As wikipedia puts it

http://en.wikipedia.org/wiki/Heat_pump [wikipedia.org]

When used for heating on a mild day, a typical heat pump has a COP of three to four, whereas a typical resistive electric heater has a COP of one. That is, one joule of electrical energy will cause a conventional heater to give off one joule of warmth, while under ideal conditions, one joule of electrical energy can cause a heat pump to move more than one joule of heat from a cooler place to a warmer place. Sometimes this is expressed as an efficiency value greater than 100%, as in the statement, "XYZ brand heat pumps operate at up to 400% efficiency!" This is not quite accurate, since the work does not make heat, but moves existing heat "upstream". This does not violate the second law of thermodynamics, because it takes less work to move the heat than to make the heat.

obligatory Austin Powers (0)

Anonymous Coward | more than 8 years ago | (#15775215)

Swedish heat pump?

"Honestly, it's not mine!"
"This sort of thing ain't my bag, baby!"

Its still a heat engine (-1, Redundant)

15Bit (940730) | more than 8 years ago | (#15774821)

Its a great idea, but it still looks like a heat engine to me and so is limited by the difference between hot (the solar collector) and cold (not mentioned in the article) parts of the cycle. Its an idea that resurfaces every few years (i remember reading when i was a kid about undersea power generation utilising the temp difference between surface and deep water), but no-one seems to be able to make it work commercially.

The problem is fundamental - thermodynamics defines the maximum efficiency to be eff=1-T(cold)/T(hot). Given that those temps are in Kelvin, not celcius, optimistic max efficiency for this system (ie assuming you can boil the water and have a glacier in your back garden for cooling) is about 26%. Solar cells are already near this, and more centralised forms of power generation are well above.

Re:Its still a heat engine (0)

Anonymous Coward | more than 8 years ago | (#15774868)

Carnot efficiency isn't the only metric here, however. Economic efficiency and thermodynamic efficiency, though correlated, aren't the same thing.

If the heat source is free (as opposed to having to buy oil, coal, or uranium) and the engine itself costs less to manufacture than high-purity semiconductors with equivalent power output, it's quite possible for something like this to make economic sense (others have mentioned heat pumps, woefully inefficient in the Carnot sense, yet still perfectly sound from the economic perspective).

Very inefficient (4, Interesting)

Cyberax (705495) | more than 8 years ago | (#15774828)

This turbine can't be very efficient. Efficiency of any heat engine is limited by the Carnot cycle (http://en.wikipedia.org/wiki/Carnot_cycle).

Basically, you can estimate it with this formula: e=(T2-T1)/T1 where T2 is the highest temperature of the working body and T1 is the lowest temperature. For such a small temperature drop as in this engine we'll get a very minuscule efficiency.

Re:Very inefficient (2, Insightful)

KiloByte (825081) | more than 8 years ago | (#15774884)

Yet, you're forgetting that heat is exactly what we have too much of. It's for all practical purposes free, so efficiency energy-wise doesn't matter.

What matters, is the efficiency time-wise, space-wise or monetary cost-wise. Having twice as much power from the same heat would be nice, but it isn't the point.

Re:Very inefficient (1)

Cyberax (705495) | more than 8 years ago | (#15775067)

The only problem: you'll need a lot of these devices to generate usable amount of energy.

Re:Very inefficient (1)

KiloByte (825081) | more than 8 years ago | (#15775142)

The only problem: you'll need a lot of these devices to generate usable amount of energy.
Exactly, that's what I meant with "space-effective" and "cost-effective". If these devices can be cheap and compact, efficiency isn't really a concern.

Re:Very inefficient (2, Interesting)

IcePop456 (575711) | more than 8 years ago | (#15775007)

I thought we only worry about efficiency when the energy supply is low? Granted I wouldn't want a huge piece of equipment, but considering how much thermal energy is in the air during the summer, cost is what I'm worried about more than efficiency.

Re:Very inefficient (1)

Cyberax (705495) | more than 8 years ago | (#15775077)

You need a temperature differential, not just a high temperature. I see that one can use water from a river/lake/sea in which case this device might very handy.

But in most places such device will be less effective then solar panels (which are not limited by the Carnot cycle, BTW).

Didi I really read ... (3, Funny)

Anonymous Coward | more than 8 years ago | (#15774837)

... all the global warming hype? I guess in the US of A the hype warms you.

Re:Didi I really read ... (0)

Anonymous Coward | more than 8 years ago | (#15775086)

I was gonna post the exact thing but you beat me to it. Thanx mate. Let them stew in the heat waves and clam its ONLY a hype. And let me quicxkly add: it doesnt matter if it is made made or if it is natural. Once ithe global warming begins to affect our food supply EVERYONE WILL get concerned. Untill then, keep on hiding your collective heads in the sand.

A/C on solar cell? (-1, Troll)

Anonymous Coward | more than 8 years ago | (#15774867)

A stupid question: would it make sense to have an A/C being charged by a solar cell?

Theoritically, a 10 m2 solar cell could produce 2 KW, enough to power a small A/C.

It probably doesn't make sense economically (at least now), but I was wondering about the effects on global warming.

Good idea. (1)

Meor (711208) | more than 8 years ago | (#15774908)

Not that I've been duped in to believing human caused global warming, but we need more passive/green energy sources like this. Geothermal is one of the most abundant, constant sources of energy that doesn't generate any waste. You don't have to worry about using exotic materials for the cycle of storage as with wind and solar.
I would recommend looking at some pictures of geothermal power plants, I was very impressed with the first one I saw. They don't even really need buildings.

best solution to global warming (3, Funny)

zimsters (978940) | more than 8 years ago | (#15774913)

best solution: pop more holes into the ozone so we can get the absolute zero temperatures of outer space cooling the earth ;) come on everybody, act now to save the planet! Buy the biggest SUV money can buy!

Re:best solution to global warming (0)

Anonymous Coward | more than 8 years ago | (#15774931)

How would buying or driving an SUV pop more holes in the ozone layer?

More flies in the ointment ... (4, Interesting)

JumpingBull (551722) | more than 8 years ago | (#15774920)

First, the refrigerant used in their independent calculation is R-22, a cloroflorocarbon that kills the ozone layer, implicated in crop failure due to high uv exposure.

Second, the cooling cycle uses water. Considering that potable water is in short supply, this is a problem...

Third, the thermodynamic Carnot cycle is a cap on the efficiency. Higher working temperatures do give a better efficiency, but you still have to cool them!

A different working fluid can be used. unfortunately, organic fluids tend to be flammable. Methanol might be a candidate. It is less toxic then ammonia.

Before the advent of mechanical refrigeration, some AC was done with evaporative air coolers. (for cinemas at the start of the 20th century). This might mitigate the second point.

Perhaps we are missing an important use. The humidity usually makes an environment uncomfortable. This system might find even more effectiveness driving a dehumidifier.

Finally, it might be equally effective to use a two stage boiler. A flat plate to get the fluid up to working temperature, and a solar concentrator to superheat the fluid to drive the system to a higher efficency

The Kalina cycle (1)

Richard Kirk (535523) | more than 8 years ago | (#15775033)

It is a pity about the chlorofluorcarbons. There is a good alternative process that uses ammonia and water that has been around for some time. It is more efficient than the straight water cycle, and the system is closed so the water isn't going anywhere. See for example http://www.geothermie.de/gte/gte46/geothermal_powe r_plant.htm [geothermie.de]

Re:More flies in the ointment ... (1)

Lord Bitman (95493) | more than 8 years ago | (#15775200)

"It uses water" ... "Potable water is in short supply"
If all water was Potable, it wouldnt be in short supply ;)

Not a chance it will work, or ever break-even. (3, Interesting)

Ancient_Hacker (751168) | more than 8 years ago | (#15774944)

Ahem, this thing won't work.

The diagram shows 10 PSI gas being condensed. Then somehow, without a pump, the 10PSI liquid "flows" into a 65 PSI boiler. No way, Jose. And no, you can't use the height of the condenser to supply "gravity" pressure. There is no free lunch.

Then there's this dang thing called the Carnot Cycle, which is impossible to violate, and dooms all these low-temp difference heat engines to extremely low efficiencies. So low, in most cases, you can't even keep up with paying the interest on the investment.

I didnt see a single numeric calculation for the loop efficiency, a really bad sign. These calculations have been basic, simple, and mandatory for upwards of a century and a third.

sure it will, it's not 10PSI (3, Informative)

_Shorty-dammit (555739) | more than 8 years ago | (#15775167)

Link to animation [matteranenergy.us] Page 7 explains how it works. The liquid is heated by an external source, such as solar water heaters on a rooftop, to a temperature much higher than ambient air temp. This heat is transferred to the liquid, which boils and gets pressurized, and goes through the turbine. After which it is condensed in the condensor, which is cooled via ambient-temperature water. Then the second heat exchanger comes into play. This second one is isolated by valves at both ends. Before the condensed liquid is released into the second heat exchanger, the empty HE is cooled by the same ambient-temperature water as the condensor was. Once the HE is roughly the same temp as the condensed liquid, the top valve opens and the condensed liquid enters the HE, and then the valve closes. Now it is isolated by both valves inside the HE. And the HE is then heated by the same solar heater, bringing the liquid up to the same temp and pressure as it is in the boiler. Then the bottom valve is opened, and the liquid moves into the boiler. The valve is then closed. Then the HE is cooled again, so it can receive more condensed liquid. And on and on. The animation, and their more clear explanation, shows the entire operation rather well. Click it, I say! Click it!

Re:Not a chance it will work, or ever break-even. (1)

Van Cutter Romney (973766) | more than 8 years ago | (#15775182)

They do show a simple solution to this. The temperature increases in the heat exchanger from 80F to 160F and as that happens the pressure increases from 10 PSI to 65 PSI. When the pressure in the heat exchanger reaches 65PSI, the pressure in the boiler reaches below the same. QED

AC?? (3, Funny)

AcidLacedPenguiN (835552) | more than 8 years ago | (#15774980)

So has the day finally arrived where I can run my AC off of all that heat outdoors?

I thought you just had to log out to run AC.

The day came 100 years ago (2, Informative)

dbIII (701233) | more than 8 years ago | (#15775002)

So has the day finally arrived where I can run my AC off of all that heat outdoors?
Early refrigeration used heat sources such as kerosene to expand the working fluid - so there are such things as the kerosene fridges with no moving parts used in remote areas. A big curved mirror reflecting the sun could have been used as the heat souce a century ago, but is a bit inconvenient. It would make far more sense to use solar heating to drive your airconditioning than have a not paticularly efficient way of converting solar energy to electricity first and then a not paticularly efficient way of using electricity to move heat about. Doing other stuff that can only be done with electricity is a different story and solar thermal scales up - but doing stuff with heat when you already have a heat source is not the best way to do it.

Re:The day came 100 years ago (1)

kfg (145172) | more than 8 years ago | (#15775034)

Early refrigeration used heat sources such as kerosene to expand the working fluid. . .

Don't be silly. I've been told right here on Slashdot that you can't make things cold by applying heat to the system. Anyone can see that doesn't make a lick of sense.

KFG

The heat-wave taught me something... (-1, Offtopic)

bogaboga (793279) | more than 8 years ago | (#15775020)

Well for me, this heat wave has been an eye opener. Like most Americans, I thought all of Africa is hotter than anything to be found in the USA. But I was wrong. Capitals of countries like Kenya, Uganda and Rwanda that I visited last year never have temperatures beyond 80 degrees Fahrenheit though they are on the equator! I was shocked.

One needs a sweater at night. I was informed that it's because of these countries' high altitute. I believe this because even when temperatures are so high in the USA, it's freezing at higher altitudes. One thing also; When [president] Bush visited Africa 2 years ago, re did not remove his jacket even though it was noon in Uganda! This tells me something. I was not "educated!"

In fact, I was told by my guide that he's never needed an A/C. When I told my relatives about what I discovered, they just could not believe it. To them like most Americans, Africa is hotter than anything found in the USA. I know they are not alone.

You're not using your head (1, Informative)

Anonymous Coward | more than 8 years ago | (#15775101)

The Mid-Atlantic has always been brutally hot in summer.

DC always has a month of weather than is 90-100 degrees with 80-100% humidity. Makes you wonder why we were stupid enough to build a city here.

And in Pennsylvania we always had 1 week fo 105-110 degree weather (accompanied by 4 weeks in january/february of 0 degree weather.

This is not a symptom of anything other than brutal weather in eastern US.

One small problem: You need a heatsink.... (1)

gweihir (88907) | more than 8 years ago | (#15775039)

Thermodynamics allows you to convert a temperature differential into mechanical energy. Heat in itself is basically worthless as enegry source. So if it gets warmer everywhere, this does not generate the possibility to produce energy.

One thing that usually can be done is to have heat/cold storage and to radiate the heat into space at night. Ironically deserts are best suited for that.

Solar Roof Powers the H2o Pump, Steam Engine (2, Interesting)

digitaldc (879047) | more than 8 years ago | (#15775117)

How about recycling the gathered water back to the steam engine with energy collected by solar roof shingles [oksolar.com] , then you have both heat and light-powered A/C.

This house [oksolar.com] would be the best of both worlds.

take a bath in the heatsink (2, Insightful)

hogghogg (791053) | more than 8 years ago | (#15775170)

If you have something cold to work as a heatsink, eg, cold water, why not just take a bath in it? A one-minute cold bath beats hours of AC any day!
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>