Solar Energy

well it doesen't matter how huge you go ive got ones that can collect about 6 months worth of power but what im not useing going into batterys

we've just reached 40% in the lab, it'll be decades until 70%, if at all. Entropy has a funny way of limiting us.

Yes,

There are solar panels that capture ~81% of the sunlight as heat, the other 19% is lost to things like reflection, convection, and re-radiation.

Take a look at http://www.solarandthermal.com/ for more info.

went there and nothing about efficency. Its a sales page with some BS about costs.

16.6.08

Vicini in all probability is talking of solar energy conversion to electrical energy whereas Tick Tock is talking of Solar to Thermal.

Considering one of the main uses of electricity is heating, it will be interesting to know how much of the installed capacity in solar panels worldwide is for heating and how much for electricity generation. In India, for example, I suspect this ratio is 90:10.

Vinay Isloorkar

The site had a ORC device that get 81% of the solar, doubtful because of temperatures required. Then the rankin cycle has a 70% eff, net 56%, then the rest of the system to electricity and its down to 40%.

I think you don't understand the point: As a huge amount of our energy needs are simply used to heat up water and houses why not using the suns energy to directly heat up the water and store some of the heat for the colder months?

Solar collectors do have huge efficiencies (>80%), that even can go higher if you would reduce the temperature you need.

Under floor heating systems work perfect with water at 40°C and even lower (top of the floor may not go above 28°C) with a decent insulated house.

Stop using oil for heating purposes.

Hello Gwen: I like your idea, especially since I am doing what you have suggested and more. I am a house builder and I have incorporated many energy saving ideas in my house. The house is ICF construction. It amazes me how little my heat requirements are. This house will be totally solar heated which is no small feat considering we do have periods of -40C weather. The boiler will distribute the solar heated water (dual coil indirect hot water tank) throughout the house. My biggest problem is dumping the surplus hot water. I can radiate it through my garage pad but if it were possible to generate power when heat requirements are met, that would be sweet. If anyone has any practical experience in this area, I would like to hear from them. I believe proper methods of construction are as, if not more important than supplemental heat. Floyd

the lowest temperature for a stirling engine is about 200 degrees F. But that means the cold end is at 70 F, sooooo. at a 130 F differential, it could be feasible to have a 0 degree F cold end and a 130 F warm end.

Eureka, switch to rankine cycle, use propane as the fluid. Lets say you have propane as a fuel source, back up. it's 5 degrees F out side the propane is at 30 psig. A small diapham pump pumps 1 gallon per minute to 200 psig, cost of .1 HP. Excess heat will vapourize the propane at 110 degrees F. The propane is sent through a pressure let down pump or turbine connected to a generator. The pressure coming out is 31 psig and temperature is 17 F, the generator makes 2.25 HP (1.6 Kw), for a net 2.15 HP. The propane is sent back to the propane tane through coils in the air that cool it back to the 5 degrees F.

Thanks

I have done some research on the Rankine gen and it looks promising. Is there anything other than propane. This is for a residential application, so something a little less volatile would be nice. The info on Rankine looks like a boiler plus generator. I need only the generator.

Floyd

freon 134A, pressures will be 13 psig in cold tank, 150 psig out of pump.

If the opportunity exists, you might try passing the hot water through a heat exchanger connected to under ground piping to function as a snow melt, for walk ways and drive ways, or to similar piping on your roof or in your attic to help with reducing the snow load and more importantly ice build up and ice damming around the eves of the roof. You might also use it to warm a small green house, thus providing for winter plant growth.

TMF

The best is to store some of the excess heat in a heat storage vault which uses the principle of latent heat.

The lower you choose the storage temp the lower the losses will be.

As explained before floor heating is perfectly happy with 40°C as hot side, when you would improve the heat exchange system and step away from the equilibrium bottle the values can be lowered.

I once made a calculation that I would need 60 ton water to cover the winter heat needs from my house. (dT was 50K if I recall right). With the latent heat system you should be able to reduce this.

If you then are able to add heat by means of other sources than pure solar heat the size of the heat storage can be significantly reduced.

I read that you plan to work with biomass, a suggestion: use a digestion process to generate methane from the biomass and this methane can be used to fire a Stirling engine. The heat at the cold side can be used to replenish the heat vault.

For a house I would work with two heat storage vaults: one a t65°C and another at 35°C.

Sorry Gwen; I wasn't clear. I guess what you call a heat vault we, in Canada, call a bio-mass, at least that's all I've heard it called. I'm using water as my storage medium. What I am trying to do is turn my surplus into electricity. If I can eliminate my gas bill and lower my electrical bill at the same time, at a reasonable cost and also in a residential application, this will be a prototype. (I hope) I 'm not doing this for my health.

Floyd

I get the picture: you have huge storage of heat in a water tank beneath the house.

What is the dT you plan to achieve? (end of summer to the end of winter)

What size does the tank have and what type and thickness of insulation do you use to conserve the heat?

You explained before that you are a house builder, do you plan to use your house as an example to sell more of the same type?

After all an intersting plan, I never heard of such an experiment driven by private persons. (the techniques used are simple but as it is not standard quite expensive)

Hello Floyd, Toomuchfun here.

I am aware of a wealthy property owner who lived in on the north shore of Lake Tahoe in Nevada. He had 3 1,000 gallon tanks for holding water installed in the crawl space beneath his house, insulated them and connected them to 6 solar water heating panels at the back of his house facing south. Of course everything was first class work. He had the necessary materials and equipment installed to salvage the heat in the water and use it to help warm the building when needed. IT DIDN'T WORK! It turned out that he would have needed the water capacity of a swimming pool, insulated in ground, to store enough heat to accomplish anything useful. The only time it helped was in the afternoon and later, and only in the summer time, and the benefit didn't last to midnight. There were just not enough exposure hours at that altitude, 6,000 ft ab. sl.

I considered trying the same thing with using concrete with two sets of piping running through out. One would contain antifreeze and the other would be used for circulating ammonia for cooling my home here in sunny Florida. After comparing the cost of construction vs the possible performance and realizing that there would be no way to make repairs or changes inside the concrete block, I determined to let someone with money to burn work out the bugs in that idea and build a working example, before I would give that a try.

Hope I helped

Tmf

You are right and indeed size does matter.

The 15000 gal Floyd is planning to use is a swimming pool. (15000 gal is 68m³)

If Floyd plans to work with an underfloor radiant heating system where he circulates water up to 35°C he can realise it.

It could be necessary to add a heat pump so that he can overcome the last part of winter when the storage goes below 35°C.

Beneath the bottom insulation he can add a system which uses the ground as cooling for summer cooling applications (not using the floor as this would invoke condensation)

But it all stands with the ability to get the heat from the sun in and keep it there till you need it. The full roof facing south should be used.

Another thing to take into account: the better you insulate your house, the better the system will work.

Good luck,

Just one more comment and I'll move on to the next forum," don't swim in the heated pool, you will come out looking like a cooked lobster," "that is if you come out at all." One other thing that has not been noted is replacing the evaporated water. It will need to be preheated, maybe at the colder time of the year.

Tmf

You will need to cover the water with an evaporation prevention.

That plastic bubble sheet is perfect vor the job. Better would be if you could store the water in a bag.

Otherwise you will end up with serious corrosion and moisture problems in your house.

Of coarse: this is a perfect situation for my solution: latent heat storage with n-Parafin.

40% total efficiency would be cause for a happy dance!

The OP said panels, not electricity, so I played with it.

I've always felt strongly that the discussion should be about the *cost* not the plot of Watts v Solar Flux. Sure the efficiency is interesting, but when a solution that satisfies the need comes in at 1/3rd of the TCO of the other solutions, does the n(eff) really matter?

This comment is really in response to posters that were bothered by the criticisms of 'technologies' that claim to skirt some of the laws of thermo-dynamics. Of run rough-shod over them at least. There are *No Exceptions* to the laws.

I tossed out th4e 81% to see who said what and foster some debate. But unless the OP wants hot pressurized ORC vapor, the reading only exists on an analysis diagram. Total system efficiency is much much lower, in fact the worst case design goal was only 15% @ 800W/m^2 insolation, but who cares if the system is making $$$?

But even with the low thermal efficiency the cost ($/W or $/MWh) is much lower than the competition. That's *real efficiency*; all within the laws of thermodynamics.

You are right, but the installed capacity ratio is because of high cost of Solar to Electricity conversion. In fact India needs less conversion to Heat than Electricity, being tropical country, as compared to Europe or US.

If the Solar to Electricity conversion costs come down drastically, India (and almost all othe countries) will be happy to reverse this ratio.

You are right, the sun's heat can be efficiently used to drive a stirling engine of fluidyne pump!

Spencer.

Can you tell me about the stirling engine and fluidyne pump. I have built a house that will be totally solar heated. I am using a 15000 gal bio-mass for storage. If surplus energy could be used to generate power once the heat demand is satisfied, it would save me dumping the surplus.

Floyd

The problem is that most power generation from heat requires 'high quality' heat.

If you are generating methane (my assumption), it can be run through standard generators that use natural gas (which is basically methane). You do need to ensure it is dry and of sufficent capacity. Another option is to chemically disassociate the hydrogen from the methane and use a fuel cell to generate electricity. (The primary effluent from the disassociation is water vapor that can be recovered if needed. That is if I remember my chemistry correctly.)

If what you have left over is low quality heat is usable in 'low delta T' sterling engines. The capital cost for effictive power generation is probably prohibitive.

The fluidyne pumps are basically a 'liquid piston' stirling cycle engine. It to runs best with 'high quality' heat. (Think a couple to several hundred degrees F.)

The best fluidyne pump application information I have seen is at http://www.iedu.com/DeSoto/Projects/Stirling/ (I have no association other than an admirer of his work)

I think Yanthram's last answer hits one of the main nails right on the head; we commonly use solar for straight water heating, or else go for electricity; probably because this fits in with how we most commonly use energy now (most Western heating systems running on hot water, most equipment / appliances being electrically driven). I know Stirling engines and the like are a bit marginal, but perhaps a bit more thought / effort into what we do with this energy and how we convert it to do useful work could pay dividends: - of course, this opens the doors to all the "free energy / perpetual motion / power of the crystals" nuts, but it shouldn't be too hard to filter all that tosh: - this forum does a pretty good job!

Hi Frozennorth,

Why do you think Stirling engines are a bit marginal?

There are several hundreds of them in everyday use here in the UK, and there are several thousands in use around the world today, even in space!

I have designed and build Stirling engines for the last 35 years, and I have one at home to produce electricity!

Spencer.

We hear there is a company in Australia that makes a system for boats, that is right expensive. On CR4 Stirling Stan has apparently the most information. As a Question on CR4, your question seems timely, and I suggest it in that Category, since we are all wondering. Still if something works, and is expensive, typically you may find it in the Grid Category. I am considering addressing energy questions in Off Grid, Or Grid Categories. The Battery Powered Home as a Hybrid will likely run up the price of Lead. Somewhere else I argued that Batteries were required for Solar Systems. You can make a case to postulate that all power past and future is Solar. So I can recommend integrated systems that are affordable for The Off Grid Life, which is some of what I think the point of the efforts is commonly. Possibly as a Governmental Policy people ought to get Tax Breaks for Experiments. I like the idea as a Transcendian political theorist. It would be nice if someone in the Forum would get Jared Diamond to participate in some of these discussions, since he has certainly influenced much of the framing, and in particular by stating that we, Humankind, are in a dangerous bottleneck. Another way of considering it all and the repetitive mentions of Stirling Engines, which are not common and I myself have never seen or touched one, is as a conflict between the Internal Combustion Machine, and the External Combustion Engine. Say we admit that the obvious trend is towards Hybrid, and then allow for Trybrid, or Quad Systems, then codify the entire package as IC and EC engine systems, put together in an integrated way for the mythical 100 Percent. The Transportation Grid is cleared and I do imagine Off Grid and On Grid Transportation Vehicles, even Trucks, that achieve efficiencies and range by being able to get to the Wire. Now of course the thing to do is imagine whatever system integrated with Solar PV, Thermal, Bio fuels, gas from decomposing things, in a micro and macro way, so scale and cost are only related to size. My interest as a Politician is in great opposition to Nuclear Energy, which enables a Weapon of Mass Destruction, is certainly more dangerous than Steam, and which has to be replaced by Solar, which comes in a number of forms. As a system I keep coming to gas from bio, and waste, thermal solar systems of the new fresnel mirror low fluid or regular, coupled to whatever else is around, for boost to boil essentially. In another area Chandu's solar cooker was questioned for Turbine and was run back to the Stirling. The point was that Turbines had to be big as they are in the Niagara River of Buffalo. I want my country to run from anything but Nuclear Power, which demands the integration of systems in practical ways for both the grid and off grid. It is some even equated with Private and Public when you consider the implications of Power Company Control of your Thermostat, as is postulated. The US is at least willing to put people in jail for corruption near as much as for selling drugs. Of course they are also willing to provide every possible motivation for both. At least the Russians had leaders who where obviously drunk enough to change things for the better. Energy Policy is an international issue. The Government does need to give us an infrastructure that meshes with what we can afford to own privately, and Solar Power is the only power everybody gets. Utilization of it is dependent on machines for the modern age. Getting through the bottleneck will depend on using the Sun as a replacement for Nuclear Power Stations, and Oil.

P.S. Having Formatting problem with unfamiliar Mac. Sorry no spell check, or paragraph breaks.

So long as govt. reaps bountiful tax revenue and the wealthy investors reap bountiful incomes from their investments, THERE WILL ALWAYS BE RESISTANCE TO ENERGY PRODUCED BY ONES SELF. THERE WILL NEVER BE ANYTHING BUT A TOKEN CONSIDERATION FROM GOVT. ONLY WHEN THE GOVT. AND THE INVESTORS CAN BENEFIT WILL YOU WITNESS CHANGE BY THE MASSES. I am not a radical only a realist. Look at the revenue the Govt. reaps from your utility taxes as a community, and recognize that Govt. is forever influenced by those who can and will spread the wealth. Creating home grown methods that can be reproduced by the masses is the only way to compensate for this issue, and the Govt. will find a way to tax it some how. It doesn't matter whether you are talking about any particular energy saving what ever. They are all taxed. The only way to save is to be at the head of the class, take advantage of the fact that not everyone can do it right now.

TMF

There is always the sales tax to keep them happy. I often point out what the conflicts are as I try to figure out how to strategize for my goals or agenda. I prefer to think of myself as a radical realist. Not all governments are corrupt, though many are. It might well fly in some that there be a Tax Credit for Independent and Costly experiments. For my model country Transcendia, I would do such, while taxing vice like gambling and pot to pay for it. There are many reasons to be gloomy since as a species we are sort of short on options in time. In your concept as Head of the Class, the duty is to lead. Head of Class is not necessarily a Leadership Position. On the Sustainable Energy Blog, somewhere, in questions concerning politics, I have recommended that a Political Party be picked to support, or another be created. Certainly I would be pleased if some of the correspondent, generous, and impassioned engineers and scientists of CR4 wanted to help my invention Transcendia. I've gotten from it about all I wanted from SW radio, I never got. -Makes me remember Barry Goldwater was a Ham. At least I've got a Grundig. Off Grid and On Grid and ECM, and ICM are in conflict that is distorted by winning investors, when all needs shared win win agreements. Anyway, be cheery. We can figure it out if we want to.

Hello Spencer, I don't mean to decry Stirling engines; they're very elegant devices in many ways. I'm not an expert on them, and hence I'm not aware of any which fit the bill for generating significant power using solar energy as the source; but if you have got this up and running I'd be very interested in your performance data if you'd like to share it: eg solar collecter area, power output (in what form? electrical? mechanical?), performance relative to weather conditions, reliability, projected or actual engine life, overall manufacturing and maintenance costs, and so on. It sounds as though you may be pointing in exactly the direction I was thinking.

Regards,

John

Hello Scapolie

How about some technical details about your sterling engine. I have a parabolic solar reflector which gives me about 300oC. I am intrested in coupling this to sterling to generate electricity. Thanks

It is marginal in most cases as compared to making hot water and you live in a climate that has more heating days. The temperature wher I live drops to the 40's at night. Our house is all windows facing south. By 4:00, its 90 degreess inside and 80 outside. So at 5:00 am when its 40 outside, its 68 inside. Not one penny spent on machinery.

I'm looking at solar water because we heat with hot water so its a fit. I'll get more BTU's used per dollar than PV or sterling in this case (our electricity is $.11/kWhr and gas is $29/MMBTU delivered)

Scapolie; can you build me a Stirling engine that could run off of surpluss heat from my collectors?

Floyd

I would be very interested in purchasing Stirling engines. I have looked and searched and can find nothing in a reasonable price range. I am also very into this. www.solarthermalelectric.org and putting up a 22 foot dish in the next two months. Any help is very welcome. Thank you,

Nick Landherr theflag@smig.net

Unfortunately Frozennorth the are a few uncompromising jerks like vicini and several others who own this forum and any other that they choose to take over, and are so chastizing that those of us who are making progress with some of the ideas that not long ago were radical perpetual dreams, that those of you who might like to be made aware of the progress will be left at the starting gate, as we choose to do our work quietly, with out the nasty attitudes infiltrating our investigative lives. It was not all that long ago that solar panels that can produce electrical energy were just as much a dream as sending and returning humanity to the moon safely. Today humanity travels safely many leagues below the surface of the sea and can sent rockets to anywhere on the planet. Somewhere along the way we must have found a way around the laws of Thermodynamics, Stick it in your ear vicini!

TMF

17.6.08

Vicini should not be vilified so much. Unwittingly, he is doing the job of an agent provocateur! In samll doses, we do need these blokes around to spice up things a bit. Distilled water aint no good for drinking unless laced with trace additions. Too much of it , of course, contaminates beyond potability.

Next time Vicini gets your goat, give it a thought! He probably suffers from the " Veni,Vidi, Vicini " syndrome.

Cheers!

Vinay isloorkar

I compromise, look ma, no problemo with Sterling engines, I've not said a word here. When the idiot on you tube sent electromagnetic waves through salt water and generated H2 gas that he then ran a stirling engine with, I went PhD in thermodynamics on that one. In the background the watt meter was up over 700 watts. The sterling engine was identified as a 200 watt unit. hummmmmm put in 700 watts, get out 200.

Going to the moon, mars, or the bottom of the Mariana Trench, NOT ONE of the Three basic laws of thermodynamics were broken. Every home grown thing you boost about has been done in laboratories for centuies before trying to get close to the third law of thermo and there has not been any significant improvement. We've tried the superconducting cryogenic route as try to approach a unity machine, nope not even close.

All the 100 mpg carburator, free energy devices, magical molecules can ever be reproduced in a laboritory. If you are serious about this, the government will pay you money to prove it and if its true, I'll bet exxon will buy you off like they did so many others, you'll be a gazillonaire!

ALL THE 100 MPG CARBS., FREE ENERGY DEVICES,MAGICAL MOLECULES, ETC.

Even though it's performance was sometimes over complimented the Z. carb. proved itself to be far superior to Strombergs, Carters, and others of the times. As for energy, it will never be free, as there will always be some cost to create and maintain such productive devices, and they will be outlawed until the Govt. can find a way to tax the performance of such products. As for magical molecules, I would like to identify just a couple, nylon, teflon, kevlar, synthetic rubber, and enough explosives to blow your brains out. Now if we can just improve the solar panels to comparable improvements regarding electricity!!!!!. AND avoid the "KILLER EEEEE'S", along the way, we just may be a little closer to something somewhat perpetual.

TMF

PV cell's aren't that bad at all;

They transform a certain wavelength into energy, typical short wavelengths.

The wider the acceptance band is the better the overall performance becomes.

But to be correct they are measured with a spectrum equal to the average sunlight as available on earth. Then the efficiency drops below 20%.

Together with the suns short wavelengths there are also long wavelengths, which heat up the panel. Reducing the efficiency again. This has been countered with setting the panels at a 20°C cell temperature (they are cooled while in test),

Results in a problem as you will not take the efforts to do this at home, but it reduces the efficiency with more than 10%.

One device is a little problem with regards to thermodynamics: thermocouples. Somehow it generates energy just by being in the hot zone. Not that you are able to do much with this energy, as it is at a reasonable low voltage but it does. The main idea is used in nuclear batteries.

But after all the TC driven units don't have better results than traditional techniques.

So it just might be that the correct translation of what happens in a metal-metal junction towards the laws of thermodynamics is not found yet.

That is where you should look into those magical devices: where did they "forget" to use the correct values or measure them correctly.

check out the threads on free energy, they contain an awful load of explications and experiments which proved that the claimers were thru scammers or just technically not capable. (some could win a Nobel Prize, on literature )

Hi Gwen,

I have know for some time now that the heating of solar panels by the suns longwavelengths, and I have often wondered if it would be economically possible to keep them cool to enhance their output?

I would like your thoughts on this please.

Spencer.

Look at this:

http://www.green-energy-news.com/arch/nrgs2004/20040150.html

This story has mostly to do with a commercial plant, but it may have links and suggestions you can use

remember to use deionized water as the minerals will plate out and leave a residue worse than the dust!

Nice link, thanks Comrade.

BAB.

The idea how it is done in the californian experiment is a bit odd.

I would use a plate radiator style to cool the PV cells (pressed against the plate and thermal connection ensured with the sticky grease)

The heated water is circulated so that the heat is exchanged with a storage device (n-Hexadecane, melts at 18°C).

A heat pump then uses the heat in this storage to supply the heat you need.

A second storage at 60 to 80°C could be added, to have the heat pump working with the solar power.

What will the system consume extra? with regards to the extra power you get from the panels? A circulator consumes about 100W, for a 3 kW system this is approx 3 to 5% of the delivered power.

Nicely described -

are there any problems with n-Hexadecane ? manufacture - toxicity ?

Back when I designed my solar storage - rocks were the answer -

I like the idea of phase change to improve the quality -

rcb

Testing - Testing - Testing

Where I live the only rocks are imported.

The n-Paraffin family is not known to be toxic. (It is even added to food as non digestible fat, to enhance the back exit passage)

the shorter the chain, the lower the flash point will become, so attention whit the heat as an overheated tank can catch fire.

The shrink ration is also rather high. all heat exchange through the walls.

Gwen- what would be an example of n-paraffin - and sources please - what are they used for ?

Thanks

rcb

There are several suppliers, some do pack the stuff already in shapes that can be used in heat storage systems.

This is a document I once found on the web.

You need a bit of puzzeling to get all data together.

show us your data TMF. Real numbers. Until you have some, just listen and learn.

The last time I checked, solar energy conversion to electricity with panels was only at about 15%, but that was a couple of years ago.

I believe Hitachi [or maybe Toshiba] announced 28.2% efficiency under lab conditions--after working a year with solar PV installations, most came in about 18%, a little more if you had means to keep them clean and cool--had a customer in Indian Wells, CA, installed a 5800 watt-rated system, but it only hit 5600 watts after being hosed down--additionally, local construction kept spreading dust on modules, which cut into production--I think the average observed was 4900 watts during summer--of course, the HOA rules prohibited the rooftop installation from being visable from the street, which meant the modules were virtually flat [on a flat roof] instead of optimal 17 degree angle.

Certainly it does seem to turn out that Solar Thermal is desirable and making great advances. PV solar panel systems have a place especially for portable systems from what I know from my study. I thought well of the Sunwise PV systems I looked up awhile back. I remember a race car driver telling me years ago that a typical car engine was only 25 percent efficient on the face of it, and he went on to say he liked to blow engines up across the finish line as a sign he had gotten all that could be gotten for the race. The Stirling engine comes up all the time and last manufacturer mentioned was Kockums in Sweden.(I was going somewhere with the idea that it is not necessarily how efficient something may be, but whether or not it gets you where you need to go.)

Solar panels are not available with high conversion efficiency to electricity. It is commercially somewhere <20% now . If the panels gets higher concentration of sunlight by using tracking reflectors then we can get higher output from a panel.

Solar Thermal for heating water is more efficient. Water having high specific heat , can capture much higher energy from sunlight than any thing else. This heat obtained can be used for heating water/making steam to run engine etc.

now my questions are.

1. which is more efficient electricity via direct conversion or electricity via thermal/sterling/etc ?

2.In each case a storage device is needed. Which is more cost effective storing in lead acid battery or storing as hot water or steam for may be two days of usage ?

3 Lastly what would be overall efficiency of a solar panel with 12 % efficiency and making hydrogen by elctrolysis of water? Storing and using via battery or hydrogen which will be efficient?

One thing you can be sure of: the battery solution is better than the hydrogen.

The primal conversion factor to go from electricity to H₂ is approx 60% efficient (if you really use a decent technique), going back to electricty thru a carnot cycle will have a total effiency of approx 25%.

The actual daily losses of hydrogen storage are approx 4%, so hydrogen is also not the best choice for long term storage.

I can't answer your question on the efficiency comparison PV/Stirling at the moment: SES is developping solar tracking sterling devices, Just ask the question directly to them.

You're using "efficiency", "unit efficiency" and "yield" interchangeably.

Concentrating panels yield more energy, because they capture more sunlight that the area of the "active" collector. Whether a Si cell or a thermal pipe. The area under panel must still be assumed to be either the total aperture of the panels, or a more honest roof or land area.

None of us are quite honest enough yet to brag about the land area requirements, because so many external factors influence those numbers negatively.

The STS panels concentrate and capture 81% of the incident sunlight normal to the aperture, losing 19% to reflection, convection, & radiation. It sounds good.

The land required to achieve an 8-hr operating window, can be 4x larger than the aperture... Should the panel be advertised as 20% efficient?

A PV panel loses output as the cosine on the sun's position in the sky; only making 15% at solar noon on the equinoxes. Should PV advertise panels at 4% efficiency?

The answer to both is: probably not. But it should be pointed out that the customer has a lot to learn to truly know what is being discussed.

Solar energy is a function of area 1st, and a function of efficiency 2nd. The total efficiency of capture also looks at how big the shadow of the panels is.

The Light is Green!

Well, so far it's been quite interesting to follow and participate in this discussion; however we still have to see any real data on the various technologies being proposed (come on Spencer / Scapolie, what about your Stirling engines??), all we seem to have is various assertions and opinions, some personal abuse,and a fair bit of navel gazing etc.

I'm a professional engineer who has worked in the oil business for more than twenty years, and in my business (and most others) this kind of thing just doesn't cut it.

Here's the point:

If you want to be taken seriously, you need to be upfront and able to show what you can do; all the technical chat and assertions in the world won't convince anyone to spend their money. Until that happens this will all stay marginal, as per my previous comment re Stirling engines.

Come on folks, stop blethering and get on with it!

Accepting your comment: your are right, we all are relying on stomach feeling more than on figures.

I did a web search and ended up at the Sandia National Laboratories.

Why are there so many efforts to chase for other techniques than PV?

Just because they have a better efficacy and are perhaps cheaper too, especially when deployed on a wide scale.

This document explains that the actual status of Solar Dish - Stirling engine combinations deliver an efficiency of 29.4% (might have been improved as the report which brings up this figure is from 1996)

The second system which is studied on a wide scale now are the solar towers: heat is used to boil water which drive a turbine. This heat can also be stored and used during the night. The efficacy is remarkably lower but the fact of being able to produce power from the stored heat is what makes Solar towers useful.

But never forget: these systems only make sense where sun is shining directly for the whole year. In Scotland you can't do a thing with it.

http://www.energylan.sandia.gov/sunlab/PDFs/solar_dish.pdf

Hi frozennorth,

Well you asked for it, so here it is, these are the facts and figures of an experimental Stirling engine for use in a car by GM:

The engine itself has four cyliders placed in a 4 square configuration, displacement 92cc. per cyl.

Heater head temperature - 1,000k or 700C.

Cooler temperature - 30c.

Working gas - H2.

Working gas pressure - 110kg/cm 2.

Output power - 165kW.

RPM - 130 to 2.100.

Efficiency - 36%.

The same engine was tested using Air and Helium, and then the efficiency and power dropped by 50% for air, and 5% for helium.

I have always used Air as my woking fluid (gas) for the simple reasons that it is readilly available and does not leak from the stirling engine as would both Hydrogen or Helium.

I have tried various heating fuels specifically for use in the third world countries, wood (small logs), wood chippings, other bio-mass and gas ie, methane.

Heater head temperature 550C to 700C, cooler temperature 20 to 30C.

My Stirling engine is a two cylinder "Alpha" configuration of 300cc,Internal fluid pressure - 10 to 15 bar, this produced 600 to 1500rpm and.

The power output with methane was in the region of 7hp, with bio-mass the power was increased slightly to 10hp, but this was because I used an air pump to increase the air-fuel mixture ie, more heat.

This was the Stirling engine I put into my boat, but I later produced a smaller copy (150cc) which I used in conjucture with my room heating system (combination Oil or Wood). This only produced 3kW maximum, but it did prove that the lower grade Stiling engine could be a possibilty in a modern dwelling or in the 3rd world countries for producing electricity for individual use.

I bought my boat engine home from Norway but as yet I have not bought another boat. Anyone who wants to build a Stirling engine as efficient and powerfull as the GM, Phillips or MAN engine will have to spend a small fortune to manufacture a prototype!

I welcome any questions.

Spencer.

how much energy did the "air pump" consume. What was the net increase.

What metallurgy is used for 1300F and and 1550 psig?

Hi Vicini,

There are several alloys that can be used, the best is a Nickel,Cobalt, Chromium alloy, or one of the Nickel alloys like "Inconel" this is used in the turbines of jet engines and gas turbines. But for lower power engines Stainless Steel can be used, but it has to be acid resistent!

Spencer.

4 cyl, 0.368 dm^3, 165kW ??? Something doesn't sound right! 16.5 kW perhaps?

Hi tick-tock,

Sorry you are right, it should have read 592cc per cyl, I must have missed the 5 out because of a disturbance outside. It turned out that three kids were having a fight over a dog.

Spencer.

Thanks for the clarification. I'm still somewhat dubious as to the reliability of such a design. That's a lot of power in a very small package! Wall temperatures & pressures *scream* creep, fatigue, and fracture.

Have you got any more data on this beast? If those numbers are any indication... Thx.

one has to first harness the energy. Solar parabolic collectors with sun tracking devices and having gold coating on reflecting surface will give best of the results.

Add a vacuumed quartz bulb having Ni-black coated Cu tube at the focal point of the collector this will convert water to steam. use it on to a turbine. store the energy generated in a battery. This can give yo the highest efficiency.

great, lets make the cost so high that at 20%/ year energy escalation, PV systems have a 30 year payback.

its still pick to of the three, cost, efficency, delivery today

Also, a lot of the 'efficiency' boosting options are great, and I applaud the research.

But we have to look at the 'life cycle' models. If we are interested in the energy, is it more efficient to put in fewer 'high end' collection systems, or many 'lower efficiency' collectors systems, and possibly 'distributed power collection systems' (a few small arrays on most buildings concept ... it keeps down the power distribution costs and allows for system redundancy).

IMHO, there is no one 'silver bullet'. There are needs that vary, as do the capital available, costs, and environmental impact concerns.

The current 'central generation' model used by most works pretty well, and overcomes costs of distribution with economies of scale. This also makes for an industry that does not want to 'let go' as any for of a 'distributed generation' model starts to make its way in to the economics, even as they complain there is not enough generation capacity.

I agree most alternative fuel alternatives are not 'full time' power generation. But even the power companies have supported 'load shedding' when use approaches the generation capacity. (They have used contractual means - industries paying lower rates for the ability for the power companies to turn off high use consumption at critical times, automation - automatically turning off air conditioners for some amount of time (I had this in Houston TX) or electric water heaters, or the worst option for consumers, rolling brownouts).

Nuke power plants are not 'life cycle green' due to the residue from both making and dealing with spent fuels and the resources needed to make them. But they do fit into the current 'full time' and 'central generation' models pretty nicely, so power companies do tend to tilt in this direction before other scenarios.

One of the big things we seem to be missing on making 'green energy', is to calculate in how 'green' is the building process (how many power plants are 'highly LEED compliant' - or for that matter even solar panels or windmills?), from the property, building facilities and materials used to build it, consumption of other resources during the 'life cycle' of the facility, through the eventual de-comissioning and 'de-construction' of the facility and turning the properties over to other uses. Yes, estimates will be a lot of 'hand waving', but standardized, reasonable assumptions can help us compare 'apples to apples' as we compare generation schemas. It at least gives a basis for comparison.

I don't think many of the 'nuke plants that have been built in the past have done the full impact life cycle analysis I alluded to above, and I believe most of the Coal fired power plants are in the same situation.

Enough pontificating... Again - no one silver bullet works. ... bummer.

If you are looking to heat water, I have evacuated tubes (CSA approved) that are 80% or better. Let me know where you are and maybe I can help. I have 6 -20 bank units on my house working very well. I have achieved temperatures of 245 degrees F, but normally you don't run them that high. I import them, so the cost will be substancially lower. There are many brands out there and mine are as good as some and better than most. (20 bank producing 6000 BTU per hour)

Floyd

that means you can make 36,000 BTU/hr with an average of 5 hours or about 180,000 BTU's per day you can make 300 gallons of hot water.

My tankless heater would run consume 200,000 BTU's costing me just over $750 per year. How much did it cost to install those puppies?

We design and install EVT thermal systems, and have over 6000 tubes under our belt. Your comment just serves to remind me of the potential errors when using production specs to build financial models. It is probable that your numbers overestimate the simple solar btu/propane btu statement.

Most tankless units are 85% or so efficient, or if you have a condensing model, maybe as high as 95%, This will help your model, as you are putting in more BTU's than you are getting out., if you are counting propane btu's.

The problem area is that your tankless unit makes hot water when, and only when, you need it. A graph of potential to supply is flat over 24 hours. That graph for your solar system is very different, and will require that your peak solar supply is a fraction of total hourly demand (in any season) in order to guarantee consumption, or large storage, with is of course more expensive both financially and in terms of energy loss.

What many people don't want to hear is that the most cost effective system design usually provides around 40% of demand, for DHW, if you build more than a multiple collector system. Another words, the closer you get to meeting demand, the more often you are paying for equipment that is producing unused BTU's. Unused BTU's are of no value. This is especially true when you build space heat systems without a summer use of btu's.l

Solar panel efficiency is not usually important, because it is an equation that does not recognize the cost of equipment over production.

Is 12K gold better than 24 K gold? Not really, but it takes up more space, and weighs more.

What if you could buy 12 K Gold for $10 an ounce, but 24K gold was $60 an ounce?

That is where we are with these solar panel efficiency issues. Experimental high efficiencies are not feasible, because the mass produced lower efficiency panels are a much better deal. Remember, 1 KW of 20% efficient solar panels makes no more energy than 1KW of 15% efficient solar panels. The former are smaller and more expensive.