Refrigerant for Engine Power (Not Freon) for Solar Generator

"I hope to have a working model of the entire system by Earth day 5014."

I see you are planning way ahead. The 3000 year time line should give you plenty of time to complete your project!

Sorry about the typo. I ran it through a spell check but it didn't catch that.

Here's a working model of your concept, but I don't think you are going to be able to escape using refrigerant. If it is an enclosed system, it shouldn't matter; why fight it?

http://www.yourownpower.com/Power/#Project Overview ...

From what I can see, he wants those properties, but with something that's as harmless as water. I don't think such a substance exists.

Dunno, he said he didn't have a problem with flammability because of closed system (but if it's a closed system, why would refrigerants be objectionable?). Of course, he could always use water - he did say low pressure .

Sounds like a greenie that has chosen to step out of reality, rather than just accept it.

Then again, earth day 5014 is a long way away. He's got plenty of time to perfect the system.

Actually I have about 9 lbs. of R11 which would be way more than I need for the model the only reason not to use it would be that I am trying not to use a freon restricted type of refrigerant and it might not be enough for the full size unit. Nbutane might very well work but it is at the limits of my psi criteria at the higher end. The nPentane doesn't have enough pressure difference at the temperature range for the engine I will be using. I am not familiar with the HCFC123 and will research that. Thanks

Then you could try iPentane, if you want a hydrocarbon. It has a little higher vapor pressure. Found this Ph diagram at http://www.core.org.cn/NR/rdonlyres/Chemical-Engineering/10-391JJanuary--IAP--2007-Spring-2007/Assignments/ps3_geothermal.pdf

Minto Wheel?

If so, I don't think he'd be worried about lubricant compatibility, would he/she?

Given your 100 C and 40C temp range butane or propane under a bit of pressure will easily work in that range plus they are both compatible with common oils as well.

Down side it you will have to have a sealed system that can withstand the working pressures.

Now as far as the green aspect and the history of refrigerants goes unfortunately it stinks of more bad politics and bad science than it does truth.

Why not put an axial flow turbine on this? Why the radial flow turbine? I didn't get that backward did I? Definitely ORC, and these are commercially available. You could use steam from low pressure steam generator, but the results would be less than impressive. OR you could use ammonia as long as the thing were as well sealed as ORC. OR you could try using supercritical carbon dioxide, but that's already been done, and they are still trying to work out the bugs with the SCO2 dissolving all the lubricant.

A lot of efficiency depends on the high molecular weight of these working fluids, and minimal pinging(small vapor droplet size) to reduce turbine wear....The clue to the turbine design may lie in the name, in this application they are called gas expanders, which produce energy, as opposed to compressors, which use energy...

http://www.youtube.com/watch?v=EPGDqxkpt6c

ref...

http://accessengineeringlibrary.com/browse/perrys-chemical-engineers-handbook-eighth-edition

I have found, that thinking about whether or not something will work, accomplishes nothing. Just do it.

If your aims are honest and true, you can't lose.

why not post a sketch of your basic system?

I'm quite curious to see your design, a new branch of physics perhaps? I'm envisioning something like the head of a sterling solar engine that's being heated by either some parabolic or a Fresnel lens...then you're proposing to "inject liquid refrigerant. the heat from the sun is added to the refrigerant, you expect a rise in both pressure as well as temperature of the refrigerant. the "phase change" (as you call it) will change the liquid refrigerant to a gaseous state. as this change occurs to expect to harness the expansion of of the gas with a piston or turbine of some type. how am I doing so far?

Well, Fredski, I'm NOT the OP (obviously), but that is the picture I got of the OPs intent, also. Pretty much verbatim.

And it does sound like a really cool method of recovering otherwise lost energy. Think about Smoky Yunick, trying for years to create an Adiabatic engine (with how much success I don't know) but with a modern tech bent. This sounds more useful, actually, since you not only get the cooling affect, but the primary power source that results can be coupled to nearly anything to get work out of it.

Drive a lumber mill (if it's powerful enough), or power a generator (for the fan on the AC unit?) or ...

Cool idea, if he can make it work.

This is a simple reciprocating piston/crank 2 cycle engine modified by removing the spark or glow plug and installing an injector that is thermally isolated from the head which is heated by a water jacket. Both the intake and the exhaust ports will be open to exhaust the vaporized coolant to the condenser mounted externally. The engine will be lubricated by oil added to the refrigerant. The engine will provide a sort of pumping action to move gases into the top of the condenser and the injection pump will be located at the bottom of the gravity operated condenser. the injector will open when it received a pulse from the injector pump. This is similar to how most mechanical diesel injectors work. In this, it has almost no similarity to a sterling engine which cools and reduces the volume of the working gas internally. I know of no sterling that actually condenses the gas to a liquid although I haven't really looked that hard. it really has more in common to a diesel engine except that no air intake is provided, no combustion takes place, and the working fluid/gas is reused continuously. Also instead of heat being generated, heat will be removed from the water jacket. The head will be heated by circulating a water-glycol solution to lower the freezing point and raise the boiling point. The heat will be a concentrating collector to heat the water glycol solution and an insulated, stratified tank will store this until use in the engine. The engine will be sized to operate more than 24 hours on the tank of hot solution. Any excess heat will be used to actually pump into grid if the heating exceeds 72 hours generation capability which will be the max the heat storage can stand. In general, I will avoid pumping into the grid, since I will get no benefit for it with my local utility structure.

My working model will be 2/100 scale to reduce cost and prove the design. This will use a small satellite TV antenna and a modified model airplane engine with a small permanent magnet starter/generator. I have both collectors at this time. I will post some pictures when available of pieces. I have already modified the model airplane engine and will soon be working on the reflector/collector unit. The model will have only 24 hour heat capability and will not have a stratified tank. It is actually more costly to build a small stratified tank than a large one.

I had originally based my design on R113 which I was familiar with the design and maintenance of the GE Vaportran transformer built in Rome, Ga. I simply prefer if possible to use a product without any Ozone restrictions. It will be a closed system and will be contained within a enclosure, so a flammable substance is not a problem since I can install a combustible gas detector to sense any leaks. I prefer not to use anything that goes to explosive conditions with only a small leak, since a combustible gas detector could not be used in that case.

This engine is closest to an early steam engine which had water injected into the cylinder and the cylinder was heated externally with a wood fire to cause the water to produce steam. It worked but never went far (It was a locomotive engine) since the piston ring was rope wrapped in a grove which caught fire after a short use and they were never able to figure out how to lubricate the piston. This was made and used in the area near Ironbridge, England.

Take a look at R290 Propane it is very similar to R22, and should have minimal problem with lubricants and is fairly inexpensive.

R290 (Propane) needs a higher pressure at 104F to stay a liquid than I would like. I am looking at R600(n-butane) unless I find something better. One thing I have trouble with is that all the data is for other purposes than what I am doing so I have to get information sort of backwards. I want the lowest possible pressure to remain a liquid at 104F and the highest possible pressure when vaporized at 210F The amount of heat removed when cooled is not very important. The amount of heat to vaporize at 210F is very important. The lower the better.

Why are you limited to 210 F as the upper temperature? I predict whether you use piston engine or turbine, this will not be a successful project due to lack of efficiency, based on a mere 58-59 degree K difference between upper and lower operating temperature. If you wish to generate power with this and be efficient, you need to put more solar gain into the equation, and consult with a competent, experienced engineering company who has worked directly with ORC.

Reply to message of James Stewart: The water/glycol heat transfer agent will at time reach nearly 300F, but by the time the head is heated it may at times be as little as 200F. If it will work at 200F, it will work at 300F and I will agree that it will not more efficient at that temperature. I will design for 210 for the required output of the engine. It will work at that level. One thing about efficiency is that the higher the temperature, the more losses due to heat loss. I have worked on Solar facilities that use a reflector to heat oil to well over 2000 in temperature, stored at that temperature underground in insulated bunkers, and that in turn is used to produce steam and generate power for the grid 24 hours per day. That is a very large generating plant. One reason for my more modest approach is cost and avoiding boiler restrictions due to pressures, plus I just want to experiment.

Absolutely do experiment. Also refer to www.cyclonepower.com to see what they offer in terms of radial piston engines that are lubricated by the feedwater to the steam generator. I suppose you could do similarly. They are using external combustion on tube style steam generator, however, I suppose solar heat recovery will also work, as they offer heat recovery models. I do not know where or how to buy one yet, and I think they are in search of licensees.

Check your mailbox. I sent you a message.

This would basically be like a compressed air engine? ...but with a closed cycle of air...

This is a rotary air engine I came across...

http://runingonair.blogspot.com/2008/12/angelo-di-pietros-amazing-rotary-air.html

http://pesn.com/2006/05/11/9500269_Engineair_Compressed-Air_Motor/

No this is nothing like a compressed air engine. Many freon engines run that way where the freon is expanded outside the engine. This engine is totally diferent and will expand the refrigerant from a liquid to a gas INSIDE the engine.

But that is evaporation, which absorbs rather than produces energy.

The energy comes from the heat in the water/glycol in the water jacket on the head. As the refrigerant expands it takes heat from that source. If you do your physics, it will drive the engine. The water/glycol solution is heated by the sun. This has been done before except the engine is usually at the focus of the concentrated sunlight and only operates during sunshine, which makes it only marginally more efficient than Solar Voltaic. Hey, this is just an experiment at this time, I have no idea of the efficiency and may try several different refrigerants in the model. I will be able to vary the injector volume to match load, even in the model. That will allow me to inject the precise amount of refrigerant to match different refrigerant properties, so I won't be tied to any one refrigerant.

Just shooting from the hip, It seems that you will have a hard time maintaining a high enough temperature in the cylinder head to make this work...Have you run the numbers on rate of heat transfer necessary to maintain adequate RPM?? Could you make a sketch outlining proposed rates of heat supply and transfer for perusal....?

Try heating the refrigerant to just below the flash point at pressure of system somewhere upstream of the point where injection takes place, and really apply some form of intense heat to the injector (if you don't destroy it by doing so). IF you try to adiabatically vaporize the working fluid (refrigerant), I think all you will get is a brain freeze (really cold head).

I have run numbers and the difference in temperature within the engine is the most important factor in delivering power. Heating it externally really reduces power. The refrigerant will not be cooled before injection and most of the vaporization will take place as it is injected. there will be a tube between the head and the injector. Not very long but this will act as a heat shield for the injector and vaporizer for the refrigerant. I have quite a capability of increasing the flow of the heated fluid in the head, so I don't really see much problem. Most of the cooling will take place in the cylinder. I have already tested the seal between the head and cylinder and the difference in temperature is not a problem. On paper the numbers work right now with R600. It might have more power with a different refrigerant but I have not done an extensive search. The reason for the model is to prove calculations. I will be getting the full size donated dish tomorrow but won't do anything with it until I get the model going. With what I have on hand the model will be less than $100 investment. It will be well worth it to prevent going down a wrong path for the final unit.

I know for a fact that a solar heated brine pond can get to way over 240 F. That kind of heat can drive a large piston where the cylinder contains a super-critical fluid: carbon dioxide (this is not low pressure stuff, sorry), but the engine is sealed and can handle the pressure, in fact the carbon dioxide in this baby never leaves the cylinder at all. You put your hot water through the jacket to drive the piston forward, and then you apply cooler water to re-draw the piston back to the top, as the volume of SCC decreases drastically. This is reasonably efficient, given that the top and bottom temperatures are not all that far apart.

Now if you can top off your circulating temperature to a higher value than 240 F you will realise more output, not less. The trick would be designing the cylinder, piston, and rod (linear motion only, sorry) to maximize stroke for the expected driving temperature (difference). Speed of this engine is not great, so you might be stuck looking for ways to efficiently use the motion produced.

There was a fellow in Sarasota, FL in the late '70's/80's who spent a great deal of time on this. Can't remember his name, but you may be able to find his notes with a bit of research.

Most of you who know electric power, know that demand for power is the highest in the summer months in the southern U.S., and that HVAC is the biggest portion of this demand. Back in the 1970's there was a great deal of "talk" about solar powered air-conditioning...whatever (pray tell) happened to that?

Is it just that all forms of solar power do not possess the energy density to compete? (not necessarily a useful argument in the light of solar concentrated power).

Or, has the cost of implementation simply been to high?

Or, was it that the range of refrigerants considered (such as the ammonia absorption cycle) was either too dangerous to consider, or still operated at the "wrong" temperatures?

I propose this: Either ammonia absorption cycle, using large volumes of humid outside air to condense water vapor and recover (for all purposes), thus modifying the cold side temperature as delivered to indoor service, or perhaps the Einstein refrigerator. Either of these will operate on fairly low grade thermal sources. The limitation would be providing enough heat storage to continue to provide service well into the dark hours.

I think the problem with solar produced air-conditioning is the lack of capacity utilization.

Consider 3 systems:

1. Solar heat → absorption cycle

2. Solar mechanical power production → vapor cycle refrigeration.

3. Solar mechanical power production → mechanical to electrical conversion → vapor cycle refrigeration.

In all but a few areas of the U.S., even in the south, there is no demand for air-conditioning for a significant part of the year. During that part of the year, the equipment investment of systems 1 and 2 sits idle. But system 3 has the capacity to export electricity when AC is not needed (and import power when solar is insufficient). This system does require the equipment (generator/inverter/motor) to convert from electrical to mechanical and back, but this equipment is relatively inexpensive and efficient. And existing homes have the back half of the system already in place. Coupled with the gub'ment requirement to purchase 'green' power at above-market price, that's why we see the emphasis on solar electricity production, as opposed to solar air conditioning.

I wonder (just thinking) if there might be a way to actually make the solar side of the absorption unit pay off during winter months as a heat source? I understand that reversing the absorption cycle is a bit out of the question. Or is it? Seems to me that by looping the hotside back to the house HX, and the cold side to the outside, one has created something resembling a heat pump. This would have to be augmented on the coldest/overcast days I presume.

I would like to get this topic back to the subject. This is not a discussion of refrigeration or air conditioning which is a good topic but deserves it's own discussion. Back on the topic, I was asked what the power will be used for. Right now it is an experiment, and calculations made with, as always assumptions, which produce varied results. With the best results the over 10 foot diameter parabolic reflector can produce 2.4 KW average over 24 hour period. But that depends on a lot of guesses about what the reflection and absorber characteristics and engine efficiency are. I know that some of you will question that but I have access to some measurements made where I live in Los Alamos, NM that support those numbers. Suffice it to say that some of the information on the internet is inaccurate to say the least. Of course those measurements were taken at 7600 feet altitude, they do not apply to sea-level measurements which are lower.

If the final design is successful, I will probably produce DC power and convert it to AC with a grid tie inverter. This will allow for variations in the available power. I will not use batteries unless I divert it to an electric car. I may couple it with the large LiFEPo4 batteries in my motor home and the solar voltaic collectors on that.

Locally there is an interesting test home that my County and a couple of Japanese companies are funding that is total electric off solar voltaic and uses a battery from a vehicle (but no vehicle) for the night time use. It ties to the grid but supplies all needed power for it's computer driven human load simulators. I went for a tour of that and the 2MW solar voltaic demonstration project that uses liquid Sodium batteries for night time coupled with conventional flooded lead for peak loading. Well worth the time if anyone is in the Northern New Mexico region. Los Alamos Smart Grid

I think you would need a dish about twice that size to get any useful work....I also think you can assume about 10% efficiency max, if you get everything set right....An expander turbine would be more efficient....possibly an old turbo charger from the junkyard might work....

I have had a lot of experience with power generation involving gas turbines, Steam turbines, and refrigerant based turbines to capture left over heat. They are efficient in large power applications but don't work so well at the lower power levels. I considered the micro turbine but it too was too large. Most of the conversion of turbo chargers are not particularly efficient. I think that the 10% is way too pessimistic but we will see what my model brings. One of the biggest problems with efficiency is accurately tracking the sunlight which is needed on a concentrating collector. I can build a circuit, but I would prefer to purchase and can't find anything within reason which will give the accuracy needed. I will probably use a computer with the angles pre-programmed by date and have a fine tuning done with sensors. I may even use separate actuators for the fine tuning with only a few degrees needed, which would help on cloud shadows if we ever have them again. My model would be able to use the smaller actuators anyway and be able to prove my circuits.

Have you considered the use of a boundary layer turbine (Tesla turbine)? The constructions is reasonably simple to do...the only thing is these operate at a really high rotation rate as I recall, might be hard to sync up with the grid, so unless you try some higher frequency generator, this might not be the ticket, or you could install a speed reducer on the shaft.

I am not concerned with sync to the grid. I will produce dc or rectify an ac output. I will direct that to a grid sync'ed inverter. The inverter I am looking at will also have the capability of charging batteries and can operate as an Isolated Island if necessary. The problem I have with high rpm is that the generator construction becomes more costly.

Is it not true that when a DC generator spins at higher rpm, there is more power produced due to more conductors traversing magnetic field "lines"? Would this not improve your efficiency somewhat? True that you might have to speed reduce between the turbine and generator anyway but not a tremendous amount if you limit the turbine to 20K/min. Suppose you found a generator that could actually handle at least 10K/min (rpm)? Just a parting thought, best wishes.

I agree with 4wsilver that a recip design seems better than a turbine for modest sized applications like this. Is there a strong reason for having a full expansion/evaporation/condensation cycle? How about just a steam engine with a solar concentrator boiler, simply expending the water?

I think he does believe he has enough solar gain with the particular bits of equipment in inventory.

I have harvested the 10 foot antenna except for the post that was cemented into really hard volcanic rocks. After going at it with a jackhammer for over an hour, we finally measured the height of the pipe and it looks like it is over 3 feet into the ground. We are at about 15-16 inches average right now. The Volcanic rocks are really huge and will not break with the jackhammer. The cement breaks easily but we have to remove it in fairly small pieces. At least another half day left on that part. I really don't have a use for the large antenna yet but had to harvest it since it was available. I will store it at a cabin I own until I get the model operating and some questions answered. Right now it is at my home on my trailer.

I am nearly complete on the engine for the model and have designed control circuits in my mind. Next I need to put them on paper.

I absolutely hope you do some experiments. Log the results...change only one variable at a time. Thats what Edison did. And everybody else who created anything worthwhile.

I love that you are actually doing something. Has this ever been done before? If so, then why is it not common? If not, then why not? Just curious...

Medium-temperature refrigeration systems have COPs (coefficients of performance) around 2.5 to 3.0. I.e., they move (not produce) 2.5 to 3.0 times as much energy as they consume. Calculating in reverse, it may be that they can generate only 0.33 to 0.40 as much energy as the heat they absorb from the sun and reject to the environment.

I thought I would bring anyone who is interested an update on my progress. I have the large satellite dish stored at my cabin in pieces. The small dish for the model is stored in the back yard of my residence. The model engine is modified except for connections and building an injector, but I do have availability of a hobby machinist who is willing to either let me use his equipment or do it for me.

The small satellite dish will be covered with mirror type peel and stick which is claimed to be 95% efficient as heat and light reflecting. I have the material and will be making tests prior to using it on the dish to determine it's effectiveness.

As far as using the reciprocal of COP to predict performance as to converting power to heat, the people I contacted locally (we have a higher percentage of doctorates in physics here than anywhere else on earth) pointed out that if you use that premise a steam engine or turbine will not work. I will be using R600 (nbutane) on my first experiment but depending on the results quite possibly will change to another fluid. That's what experimentation is all about. The charts give a clue, and manufacturing data for the item gives more, but that data is not really what I need to predict the outcome.

I will be using flat black paint for the collector, but have already proved that I will need the really high temperature version made for barbecue grills.

I will report again as this progresses.