LTD or Low Thermal Displacement, is a word that describes the use of low temperature differences for an engine, the record must be the LTD Ringbom Stirling engine that has been run on difference as low as 2 degree C. However, as Stirling engines looks enticing at the first glance, to actually crank out high power and build such is another story. Commercially built Stirling engines is high priced, and after all the DIY ability is low, unless you want to have a low powered toy.
Tesla turbines can not be fit in the LTD category, since they need high pressure steam to be run efficiently. Overall efficiency would be lower than for an Stirling unless, much hotter temperature, than can be gained by for example solar is to be used. Gas and Diesel powered Stirlings would work alright, but as for now the worlds most efficient Stirling is the NASA developed free piston Stirling, utilized in the Concentrated Disc solar project, that has for now the highest efficiency. However the price per KW is ridiculous, if i remember correct the price for a 10KW is 18000 USD and cant compete, as we shall soon see.
I Stefan Nyström has been working since 2014 with different approaches to achieve what hasn’t been done just yet, a low cost DIY friendly LTD engine, that has low cost, low wear and tear, fairly low skilled to build, and would work from 100C on the hot side, yes even lower, but energy is not worth the effort under 100C.
The same machine can be used at up to 1000C in the hot side if built with different materials.
The LTD Version is at a cost around 3500 USD for a output of 10KW.
This is achieved by buying already mass manufactured materials, that needs little to no machining, and not to many specialized parts.
This is the prototype setup for the LTD Engine, its main feature is a bendable Teflon tube, with internal piston made of Teflon aswell. In reality the hose has a bend radius of 1,5m, but limitations in the CAD animations made me have to make it a single circular coil.
The box in the middle has heat exchangers inside, and seen around the tube we can see coils who would pickup the magnetic flux established when the piston moves inside the tube. The Piston has 2 strong Neodymium magnets, classified for use in high temperature environment.
The Piston can flew and follow the curve inside the tube, and will have tight fit and precision, and is self lubricated by the properties of the Teflon. Not drawn here, but i have worked out a better design of the piston to have a round magnet on each side of it, this way more magnetic flux can be produced and fewer parts machined, this piston is shown below, but for animation and presentation purpose this is the type of piston to be used, since time consumed for redrawing it all for the new piston etc is to high due to rendering times of video.
One one side of the tube a pressurized vapor of acetone is let in, and on the other end of the tub, a condenser will be working to collapse the vapor to ensure vacuum on that side. Acetone is used to be able to have a ground cooled system that will collapse the vapor at 25C.
Higher than 40C the vapor will be pressurized and will allow for high efficiency of the LTD Engine. To allow this a slight under pressure is to be made when the LTD Engine is built and trimmed in. This will vary between different ground temperatures, or if cold water is present as a more efficient cooling method.
The main limit is the friction that the Teflon can maintain with the high temperature, speed of the piston needs to be kept under 3m/s, this means as for this prototype, that has a length of 6M, one cycle is finished every 2 seconds, to keep “speed limit”. Teflon will work as for temperatures up to 250C, after that different materials for tube, and different design of the engine needs to be achieved, since the main goal was a LTD style low cost operation, the later development of a cheap HTD….H as in High. The Ltd Engine has a variation of max performance, around 40% at max temperature 1000C up to 80% efficiency.
Below is the proposed measures for the tube and magnets inside.
Clearance for the magnets inside the tube is 0,25mm on each corner.
The boiler and the condenser will work with electronically agitated 3 way valves, which will shut, and open, to let pressure reverse and let the engine work in the other direction after completing the cycle, this will ensure no advanced electronics needs to be used, just timer set opening and close of the valves, and regulation of the pressure by temperature control.
The model on the picture is found here: http://www.valworx.com/product/electric-3-way-stainless-t-diverter-valve-1-12-12-or-24-vdc
Cheaper ones is found here: https://www.alibaba.com/premium/3_way_ball_valves.html?
These valves is stainless, but for the adventure of water steam brass ones can be used for cheaper construction. Teflon tube is found here: https://www.alibaba.com/product-detail/Used-metal-braiding-teflon-tube-pipe
Note that metal braided one is not needed with pressures achieved by max 250C.
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.
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.
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