My community is not unlike many in mountainous areas…all our roads are one lane, and out of commission whenever a narural event, heavy rain extreem wind etc. covers them with trees and ? or if NASA’s predicted solar event did occur… whenever ?
And that kills all the wires or at least most of the transformers and controlers that regulate electrical power to our mostly elderly and underemployed therefor lower income population!
Without electricty! We are toast!!!
I’m not refering to electricty for heat or most cooking we can get by without that!
We could be producing enough electricty locally to keep our oxygen generators and well water pumping, emergency communications for emt’s and fire protection, and house lights working on a on a 24-7 basis no mater what happens to Monpower’s generators or transmission lines!
Actually if we could employ “your” system it would lower our cost of power as a great deal of our cost is in keeping the ” to us worthless transmission lines” working from the source of power generation … to us at the end of Monpowers distribution system geographically!
Thats right, we are at the end of their distribution network, “Apalachan Power,” is a little over a mile from us; and serviices the communities to the south and east of us! And they don’t connect to each other! So when one only is down we can’t get power from the other … really stupid but thats the nature of “for profit” power systems nationwide!
When I was young there were almost no electrical power systems that weren’t publically …or ratepayer owned ! Then along came the republican party supporting the ” more effecient” and “more responsive to consumers needs…??? ” Publicly regulated powoer companies ! They have never been regulated..only encouraged to manipulate the regulators…and no for profit electric company has ever been more effecient and cost protective than the few survivors of the great public power system built by the federal government in the twenties and thirties! Who today still provide power at about 12% lower rate than the “for profit companies” nationwide! Even out west most of the hydroelecteic power was paid for by the Federal Governments dam building, their lower cost was a government subsidised benefit!
Mostly delivered by a for profit company!
In todays energy demanding inviornment we can’ t really do anything without some electricty… simple hand powered tools are antiques and very hard to find so nobody still has hand powered tools! All our water is provided by 220 volt electric pumps 50ft, to 400 ft down!!
I’m not refering to electricty for heat or most cooking we can get by without that! We can’t get by without electricty to pump water!
We all have wells, for our only water, with electric pumps, all are 220 volt , so few generators will power them! The bigest problem I had during the June 29th “Deratio” Was water for my livestock I never even thought about my needing a bath till the event was completely over! We were saved by catching drips from a rain we were lucky to get
We couldn’t have gotten any one in our community to a Doctor or hospital for over 9 days as the only Hospital within 45 miles, and only 10 miles away was blocked from us by all roads being unpasable mostle from trees and powerlines in the road!
Sure they were fixing everything as fast as posible… with out of state repair crews and our own working around the clock but the logic fails me when the solution is in us having our own electrical generation within our community!!!
I hate “arrogant” Monpower… when they finally got repairs to our community… after ten days they then refused to connect up the power to our “entire community” because two of the houses in our community had their electrical connections to their houses torn away but not disconnected by the wind storm … “When there wasn’t a certified electrician available within 50 miles to do a “certified repair” Then you need to realize that almost no house in this whole community has ever had the ???benefit of “a “Certified Electrician” they have never worked on our electricty ever!!! I built my own house and most all houses here were also owner built the rest are trailers built like trash looking for a place to die!. Naturally I did all ectricty connections up to Monpower connecting me to grid power….
when push came to shove , Insted of assisting us they finally just gave in and connected us to grid power! That tells me what was the real problem…
And there were no problems from the “non-certifiable house connections”.
All regulations are to support the power companies and not to keep us safe, we already know what we need to about housewhold electrical power and etc.
Nearlly all regulations about plunbing, electricty, etc. are supporting industry not peoples needs and of course safety is the supposed excuse!
I want as much info on your system as you can supply . We can probably build it if parts arn’t dificult to come by.
thank you
Monte McKenzie a founding director…
“The Neighborhood Association of Ballengee W.V. inc.” mgmckenzie80@frontier.com
Are you already thunking of producing your Stirling?
For me, that would really mean the start of a breakthrough.
The other components are interesting (especially the panels, because of their contribution to total cost) but current solutions could also be used.
The ‘system change’ depends on the stirling coming avalaible, reliable, working at the temperatures you describe and more or less at the cost level. Even slightly higher cost would still not make a big difference in overall project cost.
This was a thought, design and build experiment I have been doing for years, and just recycling and reworking. I have decided to actually do something with it. It is a pretty simple concept. Very large volume, low speed, and large surface area radiator LTD (Low Temperature Differential) Stirling engine. It is simple, you run as close to the Carnot Cycle as possible. Of course it will be a really bulky system, but who cares about that, if it is really cheap to produce and reduces the cost of energy.
When the project comes to fruition definitely let us know on here so we can all invest accordingly. Though some of us may not be well versed in G-Code, we would definitely love the opportunity to assist you in anything else you can think of. I, for one, don’t expect anything in return. Please ask readily.
Hi David.
for indonesia we are looking for such a reliable and extremely cheap system like yours to provide electricity for the poorest, where they don’t get any help from the government. is it possible to purchase such a complete build in system in a medium scale dimension, let’s say for 15 kW system? kindly let us know about your thoughts and how we can go from here. thanks a lot
One of the important things I am working on is a set of standards for these devices. The reason it is important is I wish to do “energy production as the commodity”. I am looking to standardize the power levels, and specifications of these Stirling’s. This way, much like NEMA standard stepper motors, you can swap out any unit, from any manufacturer with the equivalent, with no issues. The reason this is important is, you would decide how much power you need and want and order it in power level modules.
Going onto your question.
Currently it is not possible to purchase these Stirling’s or the solar thermal panels. I only just recently got pissed off enough to actually run with this concept. Give me a year and a little.
Hi David,
Your intentions are commendable and I think your concept of “big & cheap” is good, but the engine you propose will not meet your stated goal of “running as close to the Carnot cycle as possible”. Robert Stirling’s innovation was to add a regenerator, and that was the key to efficiently generating hot & cold temperatures, and thus pressure differentials, which drive the engine. Your engine leaves out this innovation, thus the air needs to be heated completely from the incoming heat source every time, and that means it will need a lot more incoming heat. While you’ve gone far to minimize the mechanical friction in this rotary design, the thermal losses due to leaving out the regenerator eclipse these gains by a hefty margin.
I also once came up with a low-friction rotary design similar to this one, but with a very different type of power piston. Then I realized that I too had left out the regenerator. After several other unsuccessful attempts, it is now my belief that it’s not possible to include an effective regenerator within a low-friction rotary design.
Best wishes & good luck to you in your future efforts.
The design does include a regenerator. The regenerator was left out of the design image for a simple reason. The article was already 3 pages long. The CleanTechnica.com article would have been twice as long if the thermodynamics behind 50% efficient regenerator’s and 99.999% heat exchanger’s had been explained. CleanTechnica is a place for layman wanting to know more about the goings on in clean technology, not people wanting full blown science journal articles.
Truth be told, the article with out the regenerator, was 8 pages long before I cut it down to 3 pages.
Other than the magnetic coupling, and maglev pistons, the regenerator implementation is the only new concept in this design. It is what pulls the system from a max .195 efficiency to a theoretical max efficiency of .667. It is what makes this design work. So, no I am not going to be posting that, at this time.
“The thermodynamic efficiency of a solar based LTD Stirling changes based on time of year, and time of day, based on the outside (radiator) temperature. It is not that Carnot takes a holiday (eff not = 1 – tc/th). It is that the temperature differential changes, changing the efficiency. The greater the temperature differential, the greater efficiency of an engine. During the summer months you have a plethora of energy (3x winter), and poor (5%-15%) efficiencies due to a low temperature differential between the heat source and the radiator (outside air). During the winter months you have a high (15%-30%) efficiency, due to the high temperature differential between the heat source and radiator. This allows the system to generate power in the winter more efficiently, with less energy input. It is counter intuitive and thermodynamics at work. “
I won’t be able to use this until the Stirling is into production and tested. If you keep a list of interested people, add Douglas Hvistendahl, (email adress removed) onto it, please. I work at a custom plastics plant: if parts are molded, the cost of making the molds needs to be figured into this.
The testing versions of these are going to be done on a 3D printer. Each design is going to take about 8 days to print because of their size.
It is weird that you should mention the molds. I have been trying to figure out how to do the pour on 1,100-1,500 lbs of Aluminum to cast them, prior to CNC’ing them to finish. I have done castings on some really big pieces, but this is 900+ lbs bigger than my biggest casting to date.
Quite intriguing! Count me in as wanting to keep up with your progress of this project. I’ve add your RSS to my reader so I don’t miss anything. I’m mildly tempted to prototype my own similar to your design just to see it in action.
As for getting this project forward, I’d love to help contribute through Kickstarter, Indiegogo or a similar service if that is the direction you desire to take.
But please, don’t let this all go dead in the water, if nothing else, post the full plans so others can benefit. We are all here to help each other.
If you prototype based on the design above, your max efficiency will only be about 15%-18%. It is missing the regenerator.
I would like to go the crowd funding route via indiegogo or kickstarter. I just suck at self promotion and would need to find people who are good at promotion before I start.
I have the design pretty much done. I have some efficiency issues I am working on, the regenerator only runs at about 25% eff, instead of the theoretical max of 50%. I think I may have cracked it over the weekend but have been fielding so many questions I haven’t had time to to do the numbers.
I will also be doing another article for Cleantechnica.com on the thermal panels. That is the main cost component in the design. I want to get the price down to a point where it pays for itself in under two years, at current electrical rates.
Please also keep me in the loop. As with Rusli, above, I am looking at low-cost generation for those in poverty in South Africa. We have 50% unemployment, even 75% amongst young people.
You are going to generate a huge amount of interest if this even looks like coming to fruition. I have a database and automated e-mail system I wrote for users who register on my website and I brief them every week using it. You’re welcome to the code for that or the CleanTechnica.com team can have it if it helps let you concentrate on your project rather than communicating via this blog.
My goal is to solve the worlds energy issues, make a little money along the way, and share the profits with those who help. The plan is to finish the design, create standards for packaging and energy output, and to design a cheap factory to build these things.
The benefits to really cheap energy is it opens up so many possibilities. It ends issues people have with obtaining clean water. It allows for education, manufacturing, communications, transportation, and many other things.
I admit that I still don’t see how or where a regenerator could fit into this design. But if you’ve found a way to do it, bravo!
In this case I’d suggest filing a provisional patent on it, if you’re in a country where provisionals are allowed. That will help you prove to others that you found it first, which can be helpful if or when everyone else starts trying to duplicate what you’ve done. It’s a reasonably economical step towards the real thing, and gives you a year to work out the details while still claiming the original filing date.
I’m a bit curious what temperatures you’re aiming to run this engine at. You mention a theoretical max efficiency of 0.667. The Carnot equation says that this is possible with a cold side at around 25 and a hot side at 625 (both in Celcius), but I don’t know of any injection molded plastics that will handle that kind of treatment. Aluminum melts at around 660, so it also wouldn’t have much if any strength left at that temperature. High temperatures can also cause some magnets to lose their magnetism, though I’m less clear on what temperatures you could get away with, or what magnetic materials would get you around those problems. That’s another problem to avoid if possible.
More moderate temperatures would get you more moderate performances, but the engine would last longer and you could use cheaper materials. If you could get an efficiency of 15-18% in practice (rather than max eff), and at the prices you’re describing, that would still enable the kinds of changes you’re seeking.
The target efficiency is 42 percent, which is “so never going to happen”. The temperature differential is only 30 – 40 C. The design is meant to run as close to perfect, with an ideal heat source and ideal heat sink as possible. Hence the 500-600 sq feet of radiator. (think half the floor space of a medium sized house) It is not meant for high speed it is meant for very slow strokes of and an 18+ inch piston.
If you do the math and chart it out, you end up with something like this.
All in all Stirling engines are most efficient when they are running at their slowest speeds. They produce almost no power at low speed, they do however approach these perfect engine limits.
Everyone sits around yelling Delta t, Delta t. It is not about that. It is about how efficiently you conserve energy in the system (regenerator) and how you tap the expansion and contraction of gases.
Ok – nice graph, and I see where you’re coming from; the efficiency does peak at really low speeds. Rising to near the peak will certainly get you higher efficiencies, but Carnot says that your max efficiency peak would be at around 1-(273+25)/(273+25+40), or closer to 12%. Your low-friction design would probably get you closer to that peak than most other engines, and running at low speeds would also help, but I don’t see how anything you’re doing could get you beyond that point. If everything you’re aiming to do works well, including the regenerators, I’d expect an efficiency of perhaps 10%. I’d love to have you prove me wrong about this!
Since you’re aiming to run at really moderate temperatures, I have two suggestions which I hope will help you:
You can save a bundle on making those big molds if you go with polyethylene rather than the conventional injection molded materials. This plastic itself costs a bit more, but you can mold it at low temps & pressures, which means you can make the molds from aluminum rather than stainless steel. Once you’re making thousands a day, you’ll be better able to justify the more expensive molds.
On the thermal storage, you’ll do better with a phase change material that will return most of the heat you store at the same temperature you store it. Otherwise you’ll get a declining efficiency as the thermal storage cools off as it discharges.
After what you said about Carnot efficiencies (1-(273+25)/(273+25+40)), I am going through the C+ code I wrote to design this, to find where my error is. Doing the math by hand shows that I must have an error.
There is no way the regenerator can be 98% efficient like the model says, that is approaching counter-current flow heat exchanger efficiency. Even with evolutionary algorithms doing the design, and really loose and open parameters based on the baseline design above, the max regenerator efficiency should be less than 50%.
Thanks for the udates on the efficiency.
For production purposes: I was thinking of producing the plastic parts by 3D printing, at least for the time being, to spare the moulds.
ABS or PA should be able to withstand the temperatures you have in mind.
A somewhat higher temperature design which could be used together with more advanced (and more expensive panels) could also be considered: if you go to a hot side of 95°C, your Carnot maximum becomes (95-25)/(273+95)= 0,19 or 19 %. Realistiscally you could perhaps expect 13-15%, but that could justify the higher panel cost.
If you think you have a producable design, I am willing to find a suitable 3D printshop (as I live in the Netherlands, that shop would also be in the Netherlands)
I still can’t find the flaw in the code, but thermo is thermo, and Carnot takes it FTW. The system still works with the available energy, November, January, and December worry me though. Standard flat panel thermo cells only have 1.9 kWh/M^2/day in December (NREL Manual) using panels with double pane glass, the panels we designed years back, or TIGI panels would actually give us better (> 1.9 kWh/m^2) output in the winter months.
During the summer most of the energy gathered is wasted or not used. I wish there was some easy way to generate methane from atmosphere based CO2 and H2, or some easy way to store hydrogen. This way we could just drop a second Stirling in and store the energy for winter use.
I was actually going to 3D print the prototypes up myself. My current setup is a Taig 3 axis mill with a heated bolt on table and 3D print head.
The plan is to scale up and build a 2 x 1.5 x 1 meter unit. The price to build one of these monsters, is less than a quarter the price of the prototyping in a professional 3D print shop.
I went through and checked all the methods and properties in my code. All the equations are correct. When looking at the computer evolved regenerator – displacer I found something odd that I thought might be a result of using a 1 mm grain size on the simulation. I ran it at granularity of .1 mm and got the same results a couple hours later. It seems to be storing heat, at different temperatures, along different paths in the displacer – regenerator. Really odd.
Sometimes I love evolved designs, sometimes like now though, they drive me completely up a wall. Engineers design with a purpose, evolution on the other hand comes to counter intuitive and sometimes incorrect solutions.
I am sticking with Carnot and saying the program is wrong on the efficiency, even if the displacer-regenerator is storing energy and reusing it. I will however test the displacer design for grins and giggles. You never know.
I love the idea of using a phase change material, water to steam having a couple hundred calories per mole and all, etc. Unless it is something that will melt at 70 C, and is dirt cheap, it kind of ruins the low cost part of the design criteria. The main goal is sub $20 USD per megawatt hour energy. With the need to gather more energy with the current inefficiency, it pushes the cost to the high teens, low twenties. F-me I really wanted to hit my secondary goal of sub $10 per MWh. 🙂
Hi I came here from Cleantechnica. Your efforts and goals are admirable however I think it’s apparent you have more of a mechanical than an electrical background/perspective. I’d love to see your full writeup, but I have a few questions and comments.
Apart from the 30% assumed conversion of radiant solar energy to heat (am I understanding this correctly?) and sterling carnot efficiencies, are you considering the efficiency of the electrical system of which this will be connected to? Assuming 100% efficiency from a coil passing through a magnet doesn’t seem reasonable to me, let alone this is AC not DC current. Therefore you should have a rectifier-inverter combo. Additionally, although inverter efficiency can be quite high, it depends on electrical loading. Also, if I recall correctly Carnot efficiency is achieved when a system is operated infinitely slow. How does this impact your mechanical-to-electrical conversion? Of course this is all moot if you’re $20/MWh-ish figure is based on mechanical output and not electrical. Just wanted to give you some food for thought…
I also had the same concern about your Carnot calculations that DanielB had… Also while we’re at (and considering I’m not so hot on the mechanical side) as the efficiency increases the practical power output is quite low. Is this accounted for in your $20/MWh figure? Isn’t this inefficiency on top of the difference between “practical” mechanical efficiency and carnot efficiency?
Just some food for thought before you claim to have figured out how to save the world… 😀
If you remove fuel, maintenance, all the other things a standard energy plant has, you end up with cost / MWh for LCOE. That ends up being system cost div the total power output. I could sit back and do the whole summation of n years thing, the math ends the same.
Yeah, I do know there will probably be a need to replace the 3 bearings, but 20-40 bucks of parts doesn’t add up to much in the LCOE.
Edit : FYI I am answering questions on reddit, here, google, facebook, cleanntechnica, email, google chat, and several other places. I am actually enjoying it a lot. 🙂
The Stirling has the cost of a bridge rectifier and capacitor built in. It is not shown in the image, Cleantechnica.com is not a technical journal. The article was hacked down from an 8 page monstrosity, with every detail, to what you read on CT.
The parts hacked out were many. The efficiency charts based on time of year and time of day, winter nights get you the best efficiency (tc is much lower). The different solar panels types and energy gathering capability. In the article I used the NREL data for 1961 style flat panels and left out CPC, evacuated tube, and several other low profile (3 inch high or less) designs. All of which do much better than the NREL numbers. The system was designed around those numbers and the numbers work. It was designed for horrible efficiency in the summer and better efficiency in the winter. Those charts were also left out.
As I said before, the system is designed for a nuclear winter, zombie apocalypse, or for some random ancient god to blot out the sun for a week. It has way more power coming in than it can use. It is not the final system design.
The version I plan on doing on kickstarter is going to be steel instead of plastic (95 C continuous temp on most plastics), use CPC (Compound Parabolic Collectors) flat panels (steel framed), and run at a temp differential of 150 C to 200 C depending on time of year. The cost of the Stirling will be in the $400 – $500 range and the number of panels need will be reduced substantially, as will the system cost. Plus it will run in the 4 – 4.5 kw range.
Your magnetic bearing, levitation, and coupling concepts are of interest to me. There is a guy in my locality who developed a permanent magnetic coupler. He is specializing in magnetic levitation using permanent magnets now. http://levx.com/ is his maglev site. http://www.magnadrive.com/ is the company that purchased his magnetic coupler patents. My first impression is there are major differences in the coupling designs from what you are using.
Please let me know if these concepts are of use to you in your design work. I am trying to learn more about home power generation and the possibilities of Stirling cycle units.
Steve Harris is an engineer who is big on solar energy, emergency preparedness, and energy independence. He doesn’t want to bother with Stirling cycle, seems to think we need to go with off the shelf tech., more conventional stuff applied in unconventional ways. I would like to know what you think of his approach. His website is http://www.solar1234.com/.
And another question: would it be more energy efficient to have a low voltage dc system and eliminate the inverter? This would require major changes in lifestyle, going off grid, using different major appliances, maybe going to propane or natural gas for many appliances.
Hope you survived Sandy and the winter weather ok.
The magnetic slides, and coupling concepts are all just old school 100+ year old technology with the word “magnetic” added. Replace the word pin, or the greased slide with a magnet and they are the same thing.
Both magnetic designs were discussed in sci-fi and tech literature from the 1940’s – 60’s. Truth be told, due to cost of Neodymium magnets, I may go for air floating the piston in the final design.
“And another question: would it be more energy efficient to have a low voltage dc system and eliminate the inverter? ”
At any distance DC sucks, the cables need to be to large and the losses are serious.
I will read up on the concepts in the links you sent. They will probably not do much for my design. I am trying to use new or 50 year old out of patent designs to generate energy.
Many a sound stage created i’m sure that you’ll obtain plenty of people who want to voice their own viewpoint as properly, thanks for the period spent on this.
Your article is interesting but of theoritical value. In practice it is not so easy to produce electricty at home just like purchasing and home appliance.
Invertos are in use for last 10 to 15 years which are battery operated when electrical power is not available to provide lighting in the house.These inverotors during normal electrical power supply in the area/house keep on charging inverotr batteries electrically.
Nothing to beat this solution.
Thanks for your interesting article.
My community is not unlike many in mountainous areas…all our roads are one lane, and out of commission whenever a narural event, heavy rain extreem wind etc. covers them with trees and ? or if NASA’s predicted solar event did occur… whenever ?
And that kills all the wires or at least most of the transformers and controlers that regulate electrical power to our mostly elderly and underemployed therefor lower income population!
Without electricty! We are toast!!!
I’m not refering to electricty for heat or most cooking we can get by without that!
We could be producing enough electricty locally to keep our oxygen generators and well water pumping, emergency communications for emt’s and fire protection, and house lights working on a on a 24-7 basis no mater what happens to Monpower’s generators or transmission lines!
Actually if we could employ “your” system it would lower our cost of power as a great deal of our cost is in keeping the ” to us worthless transmission lines” working from the source of power generation … to us at the end of Monpowers distribution system geographically!
Thats right, we are at the end of their distribution network, “Apalachan Power,” is a little over a mile from us; and serviices the communities to the south and east of us! And they don’t connect to each other! So when one only is down we can’t get power from the other … really stupid but thats the nature of “for profit” power systems nationwide!
When I was young there were almost no electrical power systems that weren’t publically …or ratepayer owned ! Then along came the republican party supporting the ” more effecient” and “more responsive to consumers needs…??? ” Publicly regulated powoer companies ! They have never been regulated..only encouraged to manipulate the regulators…and no for profit electric company has ever been more effecient and cost protective than the few survivors of the great public power system built by the federal government in the twenties and thirties! Who today still provide power at about 12% lower rate than the “for profit companies” nationwide! Even out west most of the hydroelecteic power was paid for by the Federal Governments dam building, their lower cost was a government subsidised benefit!
Mostly delivered by a for profit company!
In todays energy demanding inviornment we can’ t really do anything without some electricty… simple hand powered tools are antiques and very hard to find so nobody still has hand powered tools! All our water is provided by 220 volt electric pumps 50ft, to 400 ft down!!
I’m not refering to electricty for heat or most cooking we can get by without that! We can’t get by without electricty to pump water!
We all have wells, for our only water, with electric pumps, all are 220 volt , so few generators will power them! The bigest problem I had during the June 29th “Deratio” Was water for my livestock I never even thought about my needing a bath till the event was completely over! We were saved by catching drips from a rain we were lucky to get
We couldn’t have gotten any one in our community to a Doctor or hospital for over 9 days as the only Hospital within 45 miles, and only 10 miles away was blocked from us by all roads being unpasable mostle from trees and powerlines in the road!
Sure they were fixing everything as fast as posible… with out of state repair crews and our own working around the clock but the logic fails me when the solution is in us having our own electrical generation within our community!!!
I hate “arrogant” Monpower… when they finally got repairs to our community… after ten days they then refused to connect up the power to our “entire community” because two of the houses in our community had their electrical connections to their houses torn away but not disconnected by the wind storm … “When there wasn’t a certified electrician available within 50 miles to do a “certified repair” Then you need to realize that almost no house in this whole community has ever had the ???benefit of “a “Certified Electrician” they have never worked on our electricty ever!!! I built my own house and most all houses here were also owner built the rest are trailers built like trash looking for a place to die!. Naturally I did all ectricty connections up to Monpower connecting me to grid power….
when push came to shove , Insted of assisting us they finally just gave in and connected us to grid power! That tells me what was the real problem…
And there were no problems from the “non-certifiable house connections”.
All regulations are to support the power companies and not to keep us safe, we already know what we need to about housewhold electrical power and etc.
Nearlly all regulations about plunbing, electricty, etc. are supporting industry not peoples needs and of course safety is the supposed excuse!
I want as much info on your system as you can supply . We can probably build it if parts arn’t dificult to come by.
thank you
Monte McKenzie a founding director…
“The Neighborhood Association of Ballengee W.V. inc.”
mgmckenzie80@frontier.com
Are you already thunking of producing your Stirling?
For me, that would really mean the start of a breakthrough.
The other components are interesting (especially the panels, because of their contribution to total cost) but current solutions could also be used.
The ‘system change’ depends on the stirling coming avalaible, reliable, working at the temperatures you describe and more or less at the cost level. Even slightly higher cost would still not make a big difference in overall project cost.
Are you considering funding and production?
Kind regards
Harold Lever
Harold
This was a thought, design and build experiment I have been doing for years, and just recycling and reworking. I have decided to actually do something with it. It is a pretty simple concept. Very large volume, low speed, and large surface area radiator LTD (Low Temperature Differential) Stirling engine. It is simple, you run as close to the Carnot Cycle as possible. Of course it will be a really bulky system, but who cares about that, if it is really cheap to produce and reduces the cost of energy.
David
Any timeline for Sterling engine production prototype? Need any help?
I am heading down the kickstarter path with this. I can use all the help I can get. How good are you with G-Code?
When the project comes to fruition definitely let us know on here so we can all invest accordingly. Though some of us may not be well versed in G-Code, we would definitely love the opportunity to assist you in anything else you can think of. I, for one, don’t expect anything in return. Please ask readily.
Hi David.
for indonesia we are looking for such a reliable and extremely cheap system like yours to provide electricity for the poorest, where they don’t get any help from the government. is it possible to purchase such a complete build in system in a medium scale dimension, let’s say for 15 kW system? kindly let us know about your thoughts and how we can go from here. thanks a lot
One of the important things I am working on is a set of standards for these devices. The reason it is important is I wish to do “energy production as the commodity”. I am looking to standardize the power levels, and specifications of these Stirling’s. This way, much like NEMA standard stepper motors, you can swap out any unit, from any manufacturer with the equivalent, with no issues. The reason this is important is, you would decide how much power you need and want and order it in power level modules.
Going onto your question.
Currently it is not possible to purchase these Stirling’s or the solar thermal panels. I only just recently got pissed off enough to actually run with this concept. Give me a year and a little.
more importantly, couldn’t you plug 5 stirlings into the same load?
is there a huge efficiency gain if you mega scale?
Hi David,
Your intentions are commendable and I think your concept of “big & cheap” is good, but the engine you propose will not meet your stated goal of “running as close to the Carnot cycle as possible”. Robert Stirling’s innovation was to add a regenerator, and that was the key to efficiently generating hot & cold temperatures, and thus pressure differentials, which drive the engine. Your engine leaves out this innovation, thus the air needs to be heated completely from the incoming heat source every time, and that means it will need a lot more incoming heat. While you’ve gone far to minimize the mechanical friction in this rotary design, the thermal losses due to leaving out the regenerator eclipse these gains by a hefty margin.
I also once came up with a low-friction rotary design similar to this one, but with a very different type of power piston. Then I realized that I too had left out the regenerator. After several other unsuccessful attempts, it is now my belief that it’s not possible to include an effective regenerator within a low-friction rotary design.
Best wishes & good luck to you in your future efforts.
Daniel
Daniel.
The design does include a regenerator. The regenerator was left out of the design image for a simple reason. The article was already 3 pages long. The CleanTechnica.com article would have been twice as long if the thermodynamics behind 50% efficient regenerator’s and 99.999% heat exchanger’s had been explained. CleanTechnica is a place for layman wanting to know more about the goings on in clean technology, not people wanting full blown science journal articles.
Truth be told, the article with out the regenerator, was 8 pages long before I cut it down to 3 pages.
David
Could we see the 8 page version here?
The cleantechnica.com blog post is where I did the editing so those pages are now gone.
http://www.hephaestusproject.com/Energy/clean-technica-article-on-sub-20-per-mwh-energy/
Other than the magnetic coupling, and maglev pistons, the regenerator implementation is the only new concept in this design. It is what pulls the system from a max .195 efficiency to a theoretical max efficiency of .667. It is what makes this design work. So, no I am not going to be posting that, at this time.
It seems that the eight page article might become available as time goes by and people ask me questions.
http://www.hephaestusproject.com/Energy/clean-technica-article-on-sub-20-per-mwh-energy/
This has been added to the “NOTE:” section
“The thermodynamic efficiency of a solar based LTD Stirling changes based on time of year, and time of day, based on the outside (radiator) temperature. It is not that Carnot takes a holiday (eff not = 1 – tc/th). It is that the temperature differential changes, changing the efficiency. The greater the temperature differential, the greater efficiency of an engine. During the summer months you have a plethora of energy (3x winter), and poor (5%-15%) efficiencies due to a low temperature differential between the heat source and the radiator (outside air). During the winter months you have a high (15%-30%) efficiency, due to the high temperature differential between the heat source and radiator. This allows the system to generate power in the winter more efficiently, with less energy input. It is counter intuitive and thermodynamics at work. “
I won’t be able to use this until the Stirling is into production and tested. If you keep a list of interested people, add Douglas Hvistendahl, (email adress removed) onto it, please. I work at a custom plastics plant: if parts are molded, the cost of making the molds needs to be figured into this.
The testing versions of these are going to be done on a 3D printer. Each design is going to take about 8 days to print because of their size.
It is weird that you should mention the molds. I have been trying to figure out how to do the pour on 1,100-1,500 lbs of Aluminum to cast them, prior to CNC’ing them to finish. I have done castings on some really big pieces, but this is 900+ lbs bigger than my biggest casting to date.
Would it be easier to get a big block and mill it down?
Quite intriguing! Count me in as wanting to keep up with your progress of this project. I’ve add your RSS to my reader so I don’t miss anything. I’m mildly tempted to prototype my own similar to your design just to see it in action.
As for getting this project forward, I’d love to help contribute through Kickstarter, Indiegogo or a similar service if that is the direction you desire to take.
But please, don’t let this all go dead in the water, if nothing else, post the full plans so others can benefit. We are all here to help each other.
-Ryan
Ryan
If you prototype based on the design above, your max efficiency will only be about 15%-18%. It is missing the regenerator.
I would like to go the crowd funding route via indiegogo or kickstarter. I just suck at self promotion and would need to find people who are good at promotion before I start.
I have the design pretty much done. I have some efficiency issues I am working on, the regenerator only runs at about 25% eff, instead of the theoretical max of 50%. I think I may have cracked it over the weekend but have been fielding so many questions I haven’t had time to to do the numbers.
I will also be doing another article for Cleantechnica.com on the thermal panels. That is the main cost component in the design. I want to get the price down to a point where it pays for itself in under two years, at current electrical rates.
David
David,
Please also keep me in the loop. As with Rusli, above, I am looking at low-cost generation for those in poverty in South Africa. We have 50% unemployment, even 75% amongst young people.
You are going to generate a huge amount of interest if this even looks like coming to fruition. I have a database and automated e-mail system I wrote for users who register on my website and I brief them every week using it. You’re welcome to the code for that or the CleanTechnica.com team can have it if it helps let you concentrate on your project rather than communicating via this blog.
No reply necessary. Good luck.
Ian
My goal is to solve the worlds energy issues, make a little money along the way, and share the profits with those who help. The plan is to finish the design, create standards for packaging and energy output, and to design a cheap factory to build these things.
The benefits to really cheap energy is it opens up so many possibilities. It ends issues people have with obtaining clean water. It allows for education, manufacturing, communications, transportation, and many other things.
Yes, I will certainly keep you in the loop.
David Fuchs
I admit that I still don’t see how or where a regenerator could fit into this design. But if you’ve found a way to do it, bravo!
In this case I’d suggest filing a provisional patent on it, if you’re in a country where provisionals are allowed. That will help you prove to others that you found it first, which can be helpful if or when everyone else starts trying to duplicate what you’ve done. It’s a reasonably economical step towards the real thing, and gives you a year to work out the details while still claiming the original filing date.
I’m a bit curious what temperatures you’re aiming to run this engine at. You mention a theoretical max efficiency of 0.667. The Carnot equation says that this is possible with a cold side at around 25 and a hot side at 625 (both in Celcius), but I don’t know of any injection molded plastics that will handle that kind of treatment. Aluminum melts at around 660, so it also wouldn’t have much if any strength left at that temperature. High temperatures can also cause some magnets to lose their magnetism, though I’m less clear on what temperatures you could get away with, or what magnetic materials would get you around those problems. That’s another problem to avoid if possible.
More moderate temperatures would get you more moderate performances, but the engine would last longer and you could use cheaper materials. If you could get an efficiency of 15-18% in practice (rather than max eff), and at the prices you’re describing, that would still enable the kinds of changes you’re seeking.
With regards, Daniel
The target efficiency is 42 percent, which is “so never going to happen”. The temperature differential is only 30 – 40 C. The design is meant to run as close to perfect, with an ideal heat source and ideal heat sink as possible. Hence the 500-600 sq feet of radiator. (think half the floor space of a medium sized house) It is not meant for high speed it is meant for very slow strokes of and an 18+ inch piston.
If you do the math and chart it out, you end up with something like this.
http://www.hephaestusproject.com/Energy/stirling-power-curve/
All in all Stirling engines are most efficient when they are running at their slowest speeds. They produce almost no power at low speed, they do however approach these perfect engine limits.
Everyone sits around yelling Delta t, Delta t. It is not about that. It is about how efficiently you conserve energy in the system (regenerator) and how you tap the expansion and contraction of gases.
Ok – nice graph, and I see where you’re coming from; the efficiency does peak at really low speeds. Rising to near the peak will certainly get you higher efficiencies, but Carnot says that your max efficiency peak would be at around 1-(273+25)/(273+25+40), or closer to 12%. Your low-friction design would probably get you closer to that peak than most other engines, and running at low speeds would also help, but I don’t see how anything you’re doing could get you beyond that point. If everything you’re aiming to do works well, including the regenerators, I’d expect an efficiency of perhaps 10%. I’d love to have you prove me wrong about this!
Since you’re aiming to run at really moderate temperatures, I have two suggestions which I hope will help you:
You can save a bundle on making those big molds if you go with polyethylene rather than the conventional injection molded materials. This plastic itself costs a bit more, but you can mold it at low temps & pressures, which means you can make the molds from aluminum rather than stainless steel. Once you’re making thousands a day, you’ll be better able to justify the more expensive molds.
On the thermal storage, you’ll do better with a phase change material that will return most of the heat you store at the same temperature you store it. Otherwise you’ll get a declining efficiency as the thermal storage cools off as it discharges.
Regards, Daniel
Daniel
After what you said about Carnot efficiencies (1-(273+25)/(273+25+40)), I am going through the C+ code I wrote to design this, to find where my error is. Doing the math by hand shows that I must have an error.
There is no way the regenerator can be 98% efficient like the model says, that is approaching counter-current flow heat exchanger efficiency. Even with evolutionary algorithms doing the design, and really loose and open parameters based on the baseline design above, the max regenerator efficiency should be less than 50%.
Thanks
David
Thanks for the udates on the efficiency.
For production purposes: I was thinking of producing the plastic parts by 3D printing, at least for the time being, to spare the moulds.
ABS or PA should be able to withstand the temperatures you have in mind.
A somewhat higher temperature design which could be used together with more advanced (and more expensive panels) could also be considered: if you go to a hot side of 95°C, your Carnot maximum becomes (95-25)/(273+95)= 0,19 or 19 %. Realistiscally you could perhaps expect 13-15%, but that could justify the higher panel cost.
If you think you have a producable design, I am willing to find a suitable 3D printshop (as I live in the Netherlands, that shop would also be in the Netherlands)
Kind regards,
Harold Lever
Harold
I still can’t find the flaw in the code, but thermo is thermo, and Carnot takes it FTW. The system still works with the available energy, November, January, and December worry me though. Standard flat panel thermo cells only have 1.9 kWh/M^2/day in December (NREL Manual) using panels with double pane glass, the panels we designed years back, or TIGI panels would actually give us better (> 1.9 kWh/m^2) output in the winter months.
During the summer most of the energy gathered is wasted or not used. I wish there was some easy way to generate methane from atmosphere based CO2 and H2, or some easy way to store hydrogen. This way we could just drop a second Stirling in and store the energy for winter use.
David
Harold
I was actually going to 3D print the prototypes up myself. My current setup is a Taig 3 axis mill with a heated bolt on table and 3D print head.
The plan is to scale up and build a 2 x 1.5 x 1 meter unit. The price to build one of these monsters, is less than a quarter the price of the prototyping in a professional 3D print shop.
David
Daniel
I went through and checked all the methods and properties in my code. All the equations are correct. When looking at the computer evolved regenerator – displacer I found something odd that I thought might be a result of using a 1 mm grain size on the simulation. I ran it at granularity of .1 mm and got the same results a couple hours later. It seems to be storing heat, at different temperatures, along different paths in the displacer – regenerator. Really odd.
Sometimes I love evolved designs, sometimes like now though, they drive me completely up a wall. Engineers design with a purpose, evolution on the other hand comes to counter intuitive and sometimes incorrect solutions.
I am sticking with Carnot and saying the program is wrong on the efficiency, even if the displacer-regenerator is storing energy and reusing it. I will however test the displacer design for grins and giggles. You never know.
I love the idea of using a phase change material, water to steam having a couple hundred calories per mole and all, etc. Unless it is something that will melt at 70 C, and is dirt cheap, it kind of ruins the low cost part of the design criteria. The main goal is sub $20 USD per megawatt hour energy. With the need to gather more energy with the current inefficiency, it pushes the cost to the high teens, low twenties. F-me I really wanted to hit my secondary goal of sub $10 per MWh. 🙂
David
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Hi I came here from Cleantechnica. Your efforts and goals are admirable however I think it’s apparent you have more of a mechanical than an electrical background/perspective. I’d love to see your full writeup, but I have a few questions and comments.
Apart from the 30% assumed conversion of radiant solar energy to heat (am I understanding this correctly?) and sterling carnot efficiencies, are you considering the efficiency of the electrical system of which this will be connected to? Assuming 100% efficiency from a coil passing through a magnet doesn’t seem reasonable to me, let alone this is AC not DC current. Therefore you should have a rectifier-inverter combo. Additionally, although inverter efficiency can be quite high, it depends on electrical loading. Also, if I recall correctly Carnot efficiency is achieved when a system is operated infinitely slow. How does this impact your mechanical-to-electrical conversion? Of course this is all moot if you’re $20/MWh-ish figure is based on mechanical output and not electrical. Just wanted to give you some food for thought…
I also had the same concern about your Carnot calculations that DanielB had… Also while we’re at (and considering I’m not so hot on the mechanical side) as the efficiency increases the practical power output is quite low. Is this accounted for in your $20/MWh figure? Isn’t this inefficiency on top of the difference between “practical” mechanical efficiency and carnot efficiency?
Just some food for thought before you claim to have figured out how to save the world… 😀
Also, your LCOE costs are just $cost/mwh ignoring the LCOE formula…
Sorry if you’ve addressed some of these issues before in other comments on other forums, however I’m genuinely interested in your responses.
If you remove fuel, maintenance, all the other things a standard energy plant has, you end up with cost / MWh for LCOE. That ends up being system cost div the total power output. I could sit back and do the whole summation of n years thing, the math ends the same.
Yeah, I do know there will probably be a need to replace the 3 bearings, but 20-40 bucks of parts doesn’t add up to much in the LCOE.
Edit : FYI I am answering questions on reddit, here, google, facebook, cleanntechnica, email, google chat, and several other places. I am actually enjoying it a lot. 🙂
The Stirling has the cost of a bridge rectifier and capacitor built in. It is not shown in the image, Cleantechnica.com is not a technical journal. The article was hacked down from an 8 page monstrosity, with every detail, to what you read on CT.
The parts hacked out were many. The efficiency charts based on time of year and time of day, winter nights get you the best efficiency (tc is much lower). The different solar panels types and energy gathering capability. In the article I used the NREL data for 1961 style flat panels and left out CPC, evacuated tube, and several other low profile (3 inch high or less) designs. All of which do much better than the NREL numbers. The system was designed around those numbers and the numbers work. It was designed for horrible efficiency in the summer and better efficiency in the winter. Those charts were also left out.
As I said before, the system is designed for a nuclear winter, zombie apocalypse, or for some random ancient god to blot out the sun for a week. It has way more power coming in than it can use. It is not the final system design.
The version I plan on doing on kickstarter is going to be steel instead of plastic (95 C continuous temp on most plastics), use CPC (Compound Parabolic Collectors) flat panels (steel framed), and run at a temp differential of 150 C to 200 C depending on time of year. The cost of the Stirling will be in the $400 – $500 range and the number of panels need will be reduced substantially, as will the system cost. Plus it will run in the 4 – 4.5 kw range.
Your magnetic bearing, levitation, and coupling concepts are of interest to me. There is a guy in my locality who developed a permanent magnetic coupler. He is specializing in magnetic levitation using permanent magnets now. http://levx.com/ is his maglev site. http://www.magnadrive.com/ is the company that purchased his magnetic coupler patents. My first impression is there are major differences in the coupling designs from what you are using.
Please let me know if these concepts are of use to you in your design work. I am trying to learn more about home power generation and the possibilities of Stirling cycle units.
Steve Harris is an engineer who is big on solar energy, emergency preparedness, and energy independence. He doesn’t want to bother with Stirling cycle, seems to think we need to go with off the shelf tech., more conventional stuff applied in unconventional ways. I would like to know what you think of his approach. His website is http://www.solar1234.com/.
And another question: would it be more energy efficient to have a low voltage dc system and eliminate the inverter? This would require major changes in lifestyle, going off grid, using different major appliances, maybe going to propane or natural gas for many appliances.
Hope you survived Sandy and the winter weather ok.
The magnetic slides, and coupling concepts are all just old school 100+ year old technology with the word “magnetic” added. Replace the word pin, or the greased slide with a magnet and they are the same thing.
Both magnetic designs were discussed in sci-fi and tech literature from the 1940’s – 60’s. Truth be told, due to cost of Neodymium magnets, I may go for air floating the piston in the final design.
“And another question: would it be more energy efficient to have a low voltage dc system and eliminate the inverter? ”
At any distance DC sucks, the cables need to be to large and the losses are serious.
I will read up on the concepts in the links you sent. They will probably not do much for my design. I am trying to use new or 50 year old out of patent designs to generate energy.
Many a sound stage created i’m sure that you’ll obtain plenty of people who want to voice their own viewpoint as properly, thanks for the period spent on this.
Your article is interesting but of theoritical value. In practice it is not so easy to produce electricty at home just like purchasing and home appliance.
Invertos are in use for last 10 to 15 years which are battery operated when electrical power is not available to provide lighting in the house.These inverotors during normal electrical power supply in the area/house keep on charging inverotr batteries electrically.
Nothing to beat this solution.
Thanks for your interesting article.
Hi. I haven’t see any updates on this in the last three years. Are you still planning to take this to kickstarter?
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