Building a Low Cost Stirling Engine for Power Generation

Before I will start my Instructables want to emphasize that this is not a finish project and still going on as of the moment I'm creating this Instructables. I already spent more than 3 months making this though I am near to realization still it is not enough to finish the whole system on time. None the less although not finish, this Instructables will be enough for you to build a low cost running Stirling engine and more.

The aim of these Instructables is to build a working Stirling engine that could be coupled with generator for electric generation like this one http://en.wikipedia.org/wiki/Stirling_engine#media... or this http://www.power-technology.com/projects/maricopas... awesome! but not that kind, we will be building a much much .... much simple one. Honestly while building this project I want to find the best materials available but then my budget restrict me from doing it. Due to financial constraint, this Instructables became a research on building a Stirling engine having always in mind the cost (most affordable), availability of materials locally and that it could be build using the most basic tools available (poor-man's tools).

Here is my guide to make it run in few attempts. Hope you will like my Instructables please vote for it. If you find it useful please hit favorite and share.Thank you.

Understanding the Engine

What is Stirling Engine? A Stirling engine is a heat engine that operates by cyclic compression and expansion of air or other gas (the working fluid) at different temperatures, such that there is a net conversion of heat energy to mechanical work. "as per wiki" for more info check this http://en.wikipedia.org/wiki/Stirling_engine . Understanding how Stirling engine is easy as explained in this site http://www.bekkoame.ne.jp/~khirata/english/howwor... but making it run is a different story.

The Stirling engine that I made is beta type where the displacer and piston is in the same cylinder. There are many types of Stirling engine but all works in the same process. It relies on expansion and contraction of gas inside a confined space. When the air inside the cylinder is heated it will expand and when cooled it contract. All 4 image are borrowed from there respected sites. as the images are very informative so I included it here. I would like also to mention approtechie for his Stirling engine which inspires me to create my own. Some of measurement are almost identical to his engine including the use of stainless bottle as cylinder. https://www.youtube.com/user/approtechie.

In order for you to build a running engine might as well read this pdf from Andy Ross a prominent Stirling Engine experimenter. It help me a lot https://docs.google.com/file/d/0B_t-6mPcD-IYOTc4M2... page 9. If your engine doesn't work for the first time don't worry because I made 5 different engine using different materials from trash to barely running to wow!.

Preparing Materials and Tools

Prepare the materials and tools necessary for the project. This part was second most laborious to my part because I started my project without a guide or manual. It was like an building a puzzle and its pieces are not included in the set.

stainless water bottle

steel wool pack #00

luncheon meat can

wooden chopping board

dip cloth hanger

aluminum can

defective hard disk drive

terminal blocks

RTV silicone

steel filled epoxy

steel or copper or aluminum tube

nails

Building the Engine (cylinder)

The engine cylinder will house the displacer and the piston.

Cut the stainless bottle near its neck, I done it by using sharp pointed knife and hitting the knife with a hammer to puncture the bottle. be careful in doing it the knife usually bounce when hit by hammer. If you have a better way of cutting it do it. I only done it because its the only tools I have.

After I poorly cut it, I put a masking take around the bottle as the picture shown and it will serve as a marking and making sure that the bottle height is 15cm.Then I cut it using tinsnip to remove jagged edge of the bottle by carefully following the marking.

Building the Engine (displacer)

The displacer purpose is to move the air from cold side to hot side of the cylinder. While it displaces the air it also regenerator or economizer as what Robert Stirling call it. The regenerator removes the heat from air as the air moves from hot side to called side. When the air moves from cold side to warm the heat from the regenerator are transfered back to the air.

The steel wool is used as the displacer so it will act as regenerator at the same time.

As i rolled the steel wool I sandwich an aluminum foil from disposable aluminum pan to add firmness to its shape.

The foil is not visible since it was wrapped up by wool.

The height of the displacer is 10cm its diameter is almost the same as the cylinder not too tight not too loose.

The displacer must be 2/3 the height of cylinder.

Building the Engine (crankshaft)

One of important consideration in crankshaft is balance, placing of connecting rod, and reduction of friction.

my crankshaft is not well balance but its good enough.

Piston throw is 3cm or 1.5cm radius.

Displacer throw is 5cm or 2.5 radius.

The piston and displacer must be 90 degree apart.

Building the Engine (coolant Cover and Piston Base)

Building the Engine (power Piston)

The Power piston I used here is a RTV silicone using illustration board as mold.

Using alternate diameter of board as a mold.

The diameter of the mold is exactly the diameter of the cylinder.

the base of the piston is wider by 1 cm so it can be attached in the wooden cover.

Building the Engine (connecting Rod)

the connecting rods are made from wire hanger. connected to crankshaft using terminal block. sorry no picture as of this time. i'll add it later.

Building the Engine (coolant)

The engine coolant will serve as the cold side of the engine. The better the cooling of this part will give better contraction of air thus better piston drive.

The can is opened in the bottom just enough for snug fit of cylinder.

The wood pieces are attached in the can using 2 small wood screw in both side.

I used red RTV silicone as sealant to prevent water leak.

the chopping board serves a cover.

I attached to stainless tube 5mm in diameter about 5cm long. It will serves as water intake and water outlet.

The longer one 8cm long serves as intake and the shorter one serves as outlet of warmer water.

Attaching Generator

The generator I use in this project came from mini fan http://junreyparacuelles.wix.com/flickers-of-ideas... . The winding are 500 turns of #21 AWG enamel wire.

You can use any small DC motor. Just observe polarity. Polarity depends upon the direction of rotation. Just experiment with it.

If you have this kind of mini fan and decided to use it this becomes an AC generator you will be needing a full bridge rectifier to convert AC to DC