Solar Power Minus the Light

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?"

Comments

Only solves 50% of the problem

[chriss]

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

[NightRain]

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

[lordcat]

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

[thealsir]

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.

Re:Only solves 50% of the problem

[MichaelSmith]

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

[Jedi Alec]

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.

Re:Only solves 50% of the problem

[bhima]

"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

[Smidge204]

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=

Re:Only solves 50% of the problem

[B2382F29]

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

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

Re:Only solves 50% of the problem

[Aceticon]

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

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 - 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

[Rhett's Dad]

That cost estimate is pretty accurate. I went through getting a quote on installing solar panels on my $160k house, to just replace 50% of electric usage, and it priced at >$270k. It calculated out as "pays for itself after 42 years".

Contrast that with considering replacing a traditional electric heat pump with a geothermal system. About twice the cost to install, but electric costs associated with using it drop tremendously, as in $225/month summer dropping to $80/month. This calculates out to paying for itself after only about five years.

Re:Only solves 50% of the problem

[josecanuc]

That's still convective, not radiant. Radiant heat is essentially a specific wavelength range of electromagnetic waves (light). There is no equivalent negative-energy "ray".

Re:Only solves 50% of the problem

[It'sYerMam]

In other news, subtraction doesn't exist, you can only add negative numbers. Language is a convenience tool, and sometimes it's just more convenient to say that something sucks air, or radiates cold, or whatever.

Re:Only solves 50% of the problem

[Ohreally_factor]

I think the point he was making is that cold does not radiate, despite appearances. Radiation has a specific scientific meaning. While it might make "sence" to you, it will lead to all sorts of problems and misunderstandings should you want to, say, build something that needs to be cooled. That and you might get hauled into court for attempting to break the second law of thermodynamics. =)

Re:Only solves 50% of the problem

[Fordiman]

I don't get how this works without bleeding the efficiency of the systems it draws from.

I don't see what's wrong with having a parabolic mirror concentrate sunlight on the hot side, and running the cool side through a finned radiator, and blowing ambient air through it (mounted under the mirror to take advantage of its shade would be most efficient, I think). You could go stirling (more efficient, lower speed) or turbine (less efficient, higher speed) that way.

I wouldn't be worried about night-time or cloudy-day stuff. Electrical use is highest when the sun is beatin'est.

Re:Only solves 50% of the problem

[jbb1003]

2kW @ 9000EUR means 120W comes in at 540EUR, or 900AU

The OP said it would cost 1000AU. So "Next time please don't pull prices out of your ass" feels a bit harsh - and who's to say that panels aren't cheaper in Europe?

Re:Only solves 50% of the problem

[rk]

'but you can't "radiate cool"'

Speak for yourself, buster!

Re:Only solves 50% of the problem

[jank1887]

But in the initial post he didn't say radiate cool. he said "radiant cold". if you're nitpicking semantics, stick to the right ones.

starting with a response to the validity of the term radiant cooling, it is just as valid as any other type of cooling. As said before, you never create "cold", i.e., destroy energy. You move it. Thus calling an effect heating or cooling is a relative term, and it is relative to the desired end temperature of the item of interest. your conventional room air conditioner doesn't create cold within your house, it heats the outside air by transferring energy to it from inside your house, leaving net less energy inside. Cooling just describes the end effect of that energy transfer on the interior condition of your house. Radiant cooling just means you've used the process of radiation to achieve a more comfortable personal heat transfer steady-state in your house.

Heating or cooling is a relative term. In either case your are just transferring energy from a hot item to a cold item. Even the terms hot and cold are relative. You are transferring energy from the item with more to the item with less. That item with less may seem hot relative to another item. If you say something is 'cold' you actually mean "it's colder than something else (your skin, etc.). If it 'feels cold' that means thermal interaction with it creates a transfer of heat from you body to the item.

So, radiant cooling exists as much as radiant heating, as either is just transfer of energy via radiation. The person stated originally, "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". Radiant cold, being a relative term, means it is a colder radiant source than the comparative hot item, meaning it will be a net absorber of energy. It is an item which primarily transfers heat via radiation yet primarily absorbs energy from the other radiative participants.

He didn't say "thermal sink" or anything that involved the "injection of cold into the system" which wouldn't make sense. He never sugested violating physics, and didn't even invent the radiant cooling terminology (Google radiant cooling or radiant cold). Technically he was not incorrect in that respect, and this whole argument/thread about radiant cold is rather silly. But then, it's slashdot. What else should we expect :)

Re:Only solves 50% of the problem

[Mr. Slippery]

Yeah but by saying "you radiate cold" you fundamentally don't understand what's going on.

It makes every bit as much sense to speak of something "radiating cold" as it does to speak of "hole flow" in a semicondutor, or indeed "conventional current" in any electric circuit. Relax.

Re:Only solves 50% of the problem

[AnotherBlackHat]

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 most office 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.

The colo facility my servers are in has about 5,000 square meters of roof space, of which more than 50% is unused.
2,500 square meters = 2.5 megawatts at 100% efficiency, or more than twice the power used.

Data centers aren't typical though, a more typical business uses less than 100 watts per square meter of office space.
Without bothering to post the details, the breakdown point is about two stories, buildings taller than that don't get enough sunlight to completely power themselves, though if all you wanted to run was the air conditioning you could probably go taller.

All of which is irrelevant.
Solar cells on the roof are worth it when they generate more electricity than it costs to put them there.
Whether that's 100%, 50%, or 2% of the total amount of electricity consumed by the building doesn't matter.
You don't have to run all the air conditioning off solar, you can have a mix of conventional and nonconventional technology.
The "magic" price point is a dollar a watt, which we aren't at yet, but we are close. ($3 a watt is the cheapest I've seen)
And more importantly, it's likely that we will have some fundamental improvements in solar cell technology, like cheap Gratzel cells.
Wind turbans on the other hand are are very old technology.
There have been some improvements, but they nearly as cheap today as they will ever be.
The only real "improvement" is that the price of alternatives is going up.

-- Should you believe authority without question?

Re:Only solves 50% of the problem

[bhiestand]

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.

Nice to know you pulled a nice round number out of your ass. I know a small CNC machine shop (think several large computerized cutting machines constantly running), complete with air con at 74 degrees and several computer workstations on 12+ hours per day that runs entirely off of solar. The whole system cost around $40,000 before tax rebates, if I remember right. During the summer months the meter actually rolls back (it's on the grid), so that the net electricity bill is essentially nill.

Thermo

[LesPaul75]

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

[Umbral Blot]

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

[warewolfe]

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.

Carnot efficiency.

[Anonymous Coward]

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

[hamburger lady]

~5% efficiency.

what's wrong with a reflective dish and a stirling engine, 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

[chriss]

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.

Solar powered Air conditioning

[Hal_Porter]

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

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

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.

Very inefficient

[Cyberax]

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

[KiloByte]

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

[IcePop456]

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.

Didi I really read ...

[Anonymous Coward]

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

Re:Just use solar already...

[Alioth]

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.

Deep in the earth... well not that deep.

[IBitOBear]

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.

best solution to global warming

[zimsters]

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!

More flies in the ointment ...

[JumpingBull]

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

Re:More flies in the ointment ...

[asuffield]

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.

This one is not a big deal because R-22 can almost always be replaced one of the common modern refrigerants (I'm not sure which offhand, might be R-409c), which has extremely similar properties and is often used to replace R-22 in old air conditioning units. It's a little bit less efficient though (and most equipment can be redesigned to use more modern chemicals that work better). I have no idea why they used R-22 here.

Your other points are more significant problems.

(Incidentally, R-22 is an HCFC but not a CFC, and is not a major threat to the ozone layer, you're thinking of the banned R-12 which was both a CFC and a major issue. However, R-22 is being phased out anyway because there are better choices available which are even less harmful and no particularly compelling reasons to use R-22 any more)

Not a chance it will work, or ever break-even.

[Ancient_Hacker]

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.

our galactic stone-age

[uioreanu]

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

[antoinjapan]

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:our galactic stone-age

[El Torico]

The middle east will own the solar age like they do the oil age now...
Last time I checked, there was sunshine and open spaces in a lot of places other than the Middle East.

Re:our galactic stone-age

[CreatureComfort]

Well, there's lots of oil in other places also, so why does the middle east still control the world energy market? Easy, for the same reasons they will control the solar market.

1) Cheap labor
2) All their open land doesn't have any NIMBY neighbors to complain
3) No environmental restrictions/regulations
4) The open land cannot be used for anything else, especially crops.

The big downside they face is how do you transfer all the energy collected to the markets that need it? The great thing about oil is that it is extremely portable. Direct electrical transmission over power lines is hugely ineffecient and unreliable over even multi-state regions, let alone continent-wide or global distances. If only there was some ubiquitous power storage and transport system with high efficiencies to help the big middle east oil barons keep making money... hmm.. what's that.. GWB (Halliburton) is now supporting moving to a hydrogen based economy? Remember kids, hydrogen isn't an energy source, just an energy storage medium.

Is anyone still naive enough to think that all of this hasn't been thought about, researched, and planned for years? The global cartels know to the year, possibly to the month, when oil will be too expensive in recovery to maintain a strong global economy, i.e. current levels of comfort for the ultra rich. Spending large amounts of money on researching alternatives too soon just wastes current year investment income, and results of such research would interfere with pulling every last cent of profit from the current system. As soon as the money/lifestyle/economy equation balances you will see vast changes in the energy landscape, almost overnight. And the same people making huge profits now will still be making huge profits then.

Re:our galactic stone-age

[B3ryllium]

America's largest supplier of oil is ...

wait for it ...

Canada.

Re:our galactic stone-age

[WeAreAllDoomed]

Now the president runs Halliburton... hahaha. You guys just keep cracking me up.

other way 'round.

Re:our galactic stone-age

[thealsir]

I have an idea: Peer to peer power. The power company subsidizes some of the cost of installing a solar panel on people's homes, and in turn, power can be shared home-to-home. The power company wins, because they do not have as much load on their plants and can power more area with fewer plants. The people win because they have a more stable energy supply (not reliant on one/few sources). Financially, I'm sure it could be made so that people pay less for power bills and get more reliable power. The company will still have more money than they did before to invest in new plants and power more area with the same number of plants.

AC??

[AcidLacedPenguiN]

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.

Reichstag, Berlin

[D4C5CE]

Here's another "tiny, little-known building" that uses the method. Involved quite a bit of drilling, but then again we're talking several GigaWatt-hours of heat transfer per year... (Web site only partially in English)

The day came 100 years ago

[dbIII]

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.

You already have thermal energy

[dbIII]

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

[Diamondback]

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

[PeterChenoweth]

http://en.wikipedia.org/wiki/MythBusters_(season_2 )#Episode_29_.E2.80.94_.22Cooling_a_Six_pack.22

Re:You already have thermal energy

[lubricated]

In this house we do not violate the laws of thermodynamics.

Sig

[Poromenos1]

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

Well, one can always quote it :P

no, it solves 100%, it clearly states ambient air

[_Shorty-dammit]

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.

cooling water needed

[Anonymous Coward]

"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.

Solar Roof Powers the H2o Pump, Steam Engine

[digitaldc]

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

This house would be the best of both worlds.

sure it will, it's not 10PSI

[_Shorty-dammit]

Link to animation 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!

take a bath in the heatsink

[hogghogg]

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!

Re:Just use solar already...

[Alioth]

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.

Re:Just use solar already...

[Ohreally_factor]

You're talking about getting off the grid entirely, it seems. Where I live, the power company is required by law to purchase any excess electricity you put back on the grid. So, no need to store your home generated electricity with batteries.

Depending on how expensive electricity gets in the near future, solar panels to supplement what one takes off the grid might make the whole thing economically viable. Combine this with tax credits and suddenly it doesn't seem so expensive.

Not all places are equally windy. Where I live, we get a good deal more sunshine than we do wind. Wind power wouldn't work for me.

The wonders of popular science?

[dud83]

Despite using a liquid with a low boiling point, the basic laws of thermodynamics still applies.

The energy which needs to be absorbed for turning a liquid into gas can be X. A turbine cannot utilize all energy because of friction, slowness etc. So the energy which the turbine produces would be X - delta X, which could be Y.
Then you'd like to use that energy Y to power air condition to lower the temperature inside?

Did it ever strike these people to think about something called "Solar Photovoltaic Panels", commonly named "Solar Panels", the efficiency of using the photovoltaic effect is indeed much higher than relying on heating a liquid.
Anyone even slightly familiar with thermodynamics and physics will tell you that a large part of the energy to heat up a liquid into a gaseous phase will be lost to the enviroment (owning to the rather amazing "Second Law of Thermodynamics"!).

To summarize, heating a liquid into steam to harvest energy, and then attempt to convert the energy into electric energy, INSTEAD of putting up a solar panel array... Is a fantastically stupid idea. It doesn't matter that the liquid has a lower boiling point, what that means is that less energy has to be absorbed for it to leap into a gaseous phase. In plain english, by using such a liquid you collect less energy than if you were to use good old water.
Also, lets not get into the whole aspect of the fact that the boiling point of a liquid is not only dependent on temperature, but pressure as well... No matter how you twist and turn, you end up with X energy and you will loose energy in every single step and conversion.

Solar Photovoltaic Panel is much more efficient, in every possible way you look at it.

This whole idea reminds me of when you're a kid and you try to lift yourself off the ground by pulling your own legs hehe.... ;)

Use Nature's Solar Panels

[giafly]

... by planting Trees nearby. Their shade keeps your house cool, all trees produce fuel for the winter, and if you choose the right varieties they deliver free organic fruit. You'll save power by not having to run your air conditioner so much. Why must some engineers make things difficult for themselves?

Eyesore solution

[aplusjimages]

I bet you wouldn't mind looking at the windmills if I put some porn on them. Eh. You like that. I bet you do. You so dirty.

If you actually visit the company's website...

[RebornData]

There's a link in the article to the company's website. They've developed a motorless feedpump system, and there's a rather elaborate flash animation that describes specifically how it works, and several possible sources of energy... solar water heaters, sub-boiling geothermal sources, or even wood stove waste heat. The point is that they think it can work efficiently with a 50 degree temperature differential above ambient temperatures, which is pretty easily achievable without a lot of elaborate heat/cold storage.

The point of their system is not to be more efficient than solar panels, but to be MUCH CHEAPER. We don't have a shortage of energy from the sun... we have a shortage of cost-effective ways to harnass it.

-R

Re:You're not using your head

[Don853]

I don't know where in Pennsylvania you live. I grew up in the middle of the state (out in a podunk town past Gettysburg, if it makes any difference), and for the 21 years I was there, 100 degrees happened an average of maybe twice a year, and 0 degrees less often than that. Granted, 0 is a lot more common in say, the Allegheny forest, but 100 isn't. In terms of temperature change, the Mid-Atlantic is far less extreme than the plains states.

And this is totally trivial, but it's a peeve of mine: 90 degrees and 80% relative humidity is an 83 degree dewpoint, which never happens in this area of the country. Maybe the Amazon basin. The hyperbole scales badly from there.

Re:Why?

[QMO]

I don't mind at all.
Especially since I'd get paid pretty well for it.
Unfoutunately:
1- My backyard isn't big enough for nuclear waste disposal/storage.
2- Some laes restrict what I can do with my back yard.

Quick fix

[glaserud]

Just turn off all of the AC's out there, and the temperature should drop by, like, 10 degrees.

At least it was the DIFFICULT 50%

[WebCowboy]

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.

Well, this new development solves the difficult part of the equation--it provides a low-cost way to capture that heat. The cold-side of the operation is the easy part. You are onto the solution already:

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.

Well, any residence, office or industrial space with electrical service would have water service as well. This water is brought in through underground pipes and is significantly cooler than the ambient temperature in the summer. This serves a dual purpose too--even in the summer we need hot water so after the vapour in the generation circuit releases its heat energy to the water in the cooling circuit the heated water can actually be used.

Of course, this isn't a total solution to our power needs for the most part, unless you live close enough tho the equator that it is always warmer outside than the temperature of the water brought in. Of course, up here in Canada half the time the situation is reversed--it is below freezing outside and the cold water coming in is warmer, so you could use a heat pump of sorts in reverse fashion. However, the technology described here wouldn't work passively in the winter becasue you couldn't boil even this low-boiling-temperature when it is 20 below freezing. Perhaps natural gas would work and still be quite efficient (cheaper than heating your water anyways).

I think this sort of research is exactly what we need to solve our energy consumption and environmental problems. Right now, there is way too much focus on a few huge projects to solve a few huge problems. Witness the ineffectiveness of Kyoto--yes most of the signatory nations will meet their targets but at what cost? France is permamently addicted to nuclear power generation, Germany didn't even have to try because their 1990 target included dirty, antiquated, cold-war-era east-german industry that needed to be modernised anyways. Russia has not been consistent in its commitment and also has a low hurdle to jump given that it had a period of economic contraction starting around 1990. Canada signed on then did nothing at all--its GHG emmissions increased at a rate twice that of the US--a country that didn't even ratify the accord. China, India and pretty much all of Africa are exempt and are massive polluters. So what was gained out of all the time and expense and bureaucracy? Absolutely nothing--and Kyoto only addressed one single environmental issue--greenhouse gasses. In the meantime there are polluted and improperly dammed waterways, acid rain, an ozone hole, asthma-causing smog, oil-dependency, etc. that have not been adequately addressed.

Instead of dismissing these small innovations they should be embraced. Whether it is solar energy, thermal-collector-powered heat engines or fuel-cells or whatever, being able to equip houses and other buildings with "personal power generators" would have a profound positive impact on the electrical grid and power consumption. Right now the grid is like the early internet--a huge network of unreliable connections with content (electricity) delivered from a small number of large, centralised nodes. Personal generators would make it like the internet--a large, unreliable network but with an equally large number of smaller nodes providing power. This would make the grid hugely more reliable. In the event of a network/grid failure a node/generator could still provide a certain level of content/power to its local network/building electrical system. In the event of a node/generator failure, the network/grid could provide content/power to the LAN/building. Also, less overall power would

Re:Just use solar already...

[Venik]

While you guys are still playing with windmills and solar panels, I already have a small lead-cooled reactor in my garage. And enriched plutonium is not as expensive as everyone thinks.

Re:Just use solar already...

[Anonymous Coward]

Anyone else confirm this (or, prove yet again, that I'm talking out of my arse?)

I don't know about that, but I've just thought of a great place to put a wind turbine.

Re:Just use solar already...

[Bryansix]

Solar obviously does not make sense for everyone. However it makes complete sense for people in the Los Angeles area of California. The reasons are various. First of all most energy usage is in the Summer when solar energy is abundant. Secondly there is plenty of time when the sun shines here and we have many more sunny days then overcast or stormy days. Thirdly, Southern California Edison has a program to interconnect solar panels to their energy grid. In essence wehn you generate electricity you spin your meter backwards. This means they have to buy less power from outside sources and this saves them money too and no batteries are involved. If you need power at night, you are still connected to the grid. Most estimates say that it will take about 19 years to pay off a solar panel installation. However power prices have risen since those estimates where made and they will most likely rise again. The point is that solar not only pays for itself but it adds clean energy to the grid and bypasses most of the distribution associated with large power plants thereby cutting those costs as well. All of society as a result benefits. Solar is not just a novelty.

Radioisotope thermoelectric generators (RTGs)

[ElliotLee]

Can we harness a technology similar to RTGs for the consumer market? RTGs last for a long, long time: 10 to 20 years or more. They're currently used in spaceflight, and have been used by the Apollo lunar landings, the Viking Landers, the Voyager explorations, and, of course, Cassini. RTGs are not nuclear reactors, have no moving parts, and use neither fission nor fusion. The heat generated by the natural radioactive decay of plutonium, mostly Pu-238 (a non-weaponsgrade isotope), is changed into electricity by solid-state thermoelectric converters. Would it be possible to generate electricity from other sources of heat, too (such as the sun, described in this article)? On Cassini, Power and Pyrotechnic Subsystem (PPS) provided a regulated 30V DC electrical power to the spacecraft, derived from the three RTGs onboard. It is then conditioned and distributed to the powered spacecraft components. RTGs don't provide a lot of power at once, but they provide it for a long time. But they're designed to last for many, many years. If the timespan were shortened, could they generate more power?

Re:Just use solar already...

[WeAreAllDoomed]

buckminster fuller suggested putting a windmill on basically every existing high tension line tower.

they're an eyesore already, and the generated electricity can be transferred directly to to grid. (supplementally, of course).