The LTD Stirling or the Ringbom LTD Stirling engine is a sterling engine that can run on very low temperature difference, in 2013 i Stefan Nyström, was exploring some way to scale up, and maintain low cost build to be able to utilize this Stirling engine design for extracting heat from a wood fired stove, to provide a descent amount of electrical energy, in an off grid situation.
LTD mean low thermal displacement, as in small difference between the hot and cold side of an engine. Low efficiency, but also abundant low grade heat sources can be used. Efficiency is not always the best approach, the best bang for the buck, can be a better road. Especially for the long run cost of operations.
This model of Stirling engine, has so far as i could see, just be used as a demonstration or like a toy, running on the heat from the palm of the hand, or from a coffee cup.
There are aswell numerous videos of how you can build this type of Stirling engine from a coca cola can aswell.
However the output is very small, and unless if you can manage to scale it up in some meaningful way, it has no use at all, as an electrical generator. Thermal efficiency is lower than 5%, reports have been made, about high efficient low thermal displacement Stirling’s, but, this information is yet to be found anything about, no schematics, pictures or anything useful, was i able to find, after years of searching.
Nevertheless i started to think of this engine model in bigger terms.
We know that in the arctic zone, temperature can be well below the -50’s, this means, that in some locations, the colder it gets, the more free energy from the cold, can be extracted. Well, not from the cold really, since that is impossible, but to utilize the very cold weather, and use the arctic ocean water as a heat.
Under the ice, the water will be always 4C and can be pumped up, in insulated pipes. So if you have a insulated container, filled with LTD sterling, the hot side would be 4+ and the cold side -50C or higher. This means endless amounts of energy is present and readily available. In summer time, cheap solar collectors, could provide heat, and let energy be produced abundantly, and for low cost.
Now to the technology, i wanted to use common materials, so i settled for standard plywood, Styrofoam insulation, and T-junctions made for water piping. It worked out that bearings will fit readily inside the T junctions and will not require machining to be utilized.
For the working cylinder, i found that its possible to use 2 sets of Teflon, already machined, all that is needed is to cut to the length needed. Volume for the working piston is 50cc the displacer piston has diameter of 400mm
In my prototype, i wanted to maintain readily made components as much as possible, therefore i chose a standard 115mm rubber wheel as flywheel, this is fairly expensive, and a steel plate would do just the same, for far less price.
Picture above has the wood made transparent so the displacer plate can be sen. The picture below, shows the high density Styrofoam plate, with laser-cut or water-jet cut holes for the assembly.
As we can number of engines on this 2,4mx1,2m plate is 14, and according to other models proven, this would give one plate at least 250watt electric output. in my CAD the assembly has an oversized belt drive, i found it was very difficult to model one myself, so i used built in functions in Autodesk, to at least get the resemblance of what it would look like. Very cheap belt drives is existing, used for hobby models, as helicopters etc. One other way is to go for a bicycle chain, but the belt drive is more durable, maintenance free, and is readily seen more frequently replacing chains also on bicycles.
The idea with the rubber wheels, was to be able to drill holes in the rubber and press Neodymium magnets in the hole, to make the unit generating electrical power. Having a coil, sitting on the upper board collecting the magnetic flux when the wheel spins, this is of course also possible, on a steel plate flywheel. with a glued or screw attached magnet.
The name for the innovation came about the idea to stack these pancake sized cylinders on top of each other, to make a larger unit.
As in the picture below 56 engines in one pancake stack 🙂
This would produce 1000 Watts per hour, or as we say 1 KW/H perfect to be powered from excess heat from a wooden stove in a remote hunters cabin, where normally no electricity is available.
Charge mobile phones, HAM radio, electrical appliance, television or whatever equipment could be used out in the wild.
This is a short video that shows the mechanical components in motion.
As of 2015 price for one Stirling Pancake plate with 14 displacer cylinders parts price was 232 USD a 1KW stack would be 1000USD with electrical output added. Cost can be cut down to around 600 USD for the 1KW stack, if metal plates is used instead of the rubber wheels. Fairly cheap i would say for a wood driven electrical generator. For the arctic cold driven generators, i think the abundance of electrical energy for locals use would be priceless, however, for professional use, alterations to the material choice would be necessary.
Worthwhile for an endless energy source, that works stronger in the dark of nigh, aswell as during the day, the more dire the weather, the more output can be achieved.
Investors are needed, contact me for more information, many projects of this type and of greater magnitude is already developed. Lack of funds has stalled my projects, due to investors that have not performed.
As of this i release the technology for free, for anyone to use, more details can of course be added to the technologies, but for this i cannot maintain at no cost operation. So if you are prepared to add some funding in the mix many aspects of the development, manufacturing etc can be avoided. Feel free to contact me.
Energy hegemony must end, do your part. Tweet, make videos, spread the message, abundance of cheap energy is here, help it come to fruition.