KS90S Solar Acrylic Inverted Stirling Engine

Inverted configuration

The KS90S inverted engine takes the classic KS90 solar acrylic engine and turns it on its head. With all the attachments like the flywheel, power cylinder and main pillar being underneath, sunlight can heat the whole of the top without shadows, giving optimal heating. Place it on a firm surface in the sun, such as a south-facing windowsill and the sunlight hitting the top plate will drive the engine. Alternatively you can position a small halogen or incandescent lamp near the top plate and the heat from the lamp will drive the engine. You can also invert the engine and it will run equally as well. If you warm the bottom plate by placing the engine upside down on a cup of hot coffee or tea, TV digibox or the human hand the engine will run.

Eco-friendly

This KS90S acrylic solar engine is the ultimate eco-friendly device, showing with one spin of the flywheel a clean and simple way of converting waste heat into motion. Because Stirling engines rely on a temperature difference for operation, they will run on almost any heat source. Although this particular engine is optimised for solar operation it will also run just as well from any other heat or cold applied to the top plate. As long as the top plate is 5°c to 10°c warmer or cooler than the aluminium middle plate the engine will run. If you warm the top plate as in solar operation the engine will run clockwise. If you cool the top plate by placing a bowl of ice on it the engine will run anti-clockwise.

How does it work?

Stirling engines work by cyclically heating and cooling the air inside the main chamber. As the air heats up it expands, and as it cools down it contracts. This expansion and contraction drives a small piston which in turn drives the flywheel. The clever thing about Stirling engines is that the mechanism for cycling the heating and cooling of the air is built into the engine in the form of the displacer, which is driven by the flywheel and crank arrangement and moves the air from the warm side to the cool side and back again over and over.

The Stirling engine is named after its inventor, Rev. Robert Stirling, who patented his idea in 1816.

Heat Sources

• The engine can run on strong direct sunlight. The top surface will be the hot side and the bottom the cool side and the engine will run anti-clockwise.
• The engine can run on hand heat. If you have a warm hand in a cool room the engine will run upside down from the heat of your hand.
• Placing a freshly made cup tea or coffee (NOT BOILING) on the top plate will provide enough energy for it to run at a relatively high speed for up to 30 minutes. Similar to solar heating, the engine will run clockwise.
• Placing a bowl of ice on the top plate will provide enough temperature difference for operation. If you cool the top plate the engine will run anti-clockwise.

Main features:

• Inverted main chamber
• Optimised for solar power, runs on direct sunlight
• Will run on a 5°c to 10°c temperature difference
• Extremely low friction self-lubricating graphite piston
• Built in flywheel balancing
• Main chamber pillars thermally isolated with nylon screws
• Regenerating power piston
• Elegant brass legs

Materials

• Stainless steel connecting rods and ball-race bearings
• PEEK connecting rod bushes
• Micron precision borosilicate glass cylinder
• Micron precision graphite power piston
• Aluminium main pillar, hub and spokes
• Brass chamber pillars and flywheel rim
• Brass gland and cylinder holder
• Brass legs
• Acrylic top plate
• Aluminium middle plate
• Acetal base

Dimensions

• Top plate - 98mm diameter, 3mm thick (3.86" x 0.19")
• Base - 100mm diameter, 10mm thick (3.94" x 0.39")
• Displacer - 70mm diameter, 7mm thick (2.75" x 0.27")
• Flywheel - 82.5mm diameter, 4mm thick (3.25" x 0.16")
• Power piston - 9.5mm diameter (0.375")
• Overall height - 167mm (6.57")

Assembled or Kit

The engine is available fully assembled and ready to go or as a self-assembly kit.

Instructions

Click the image below for PDF assembly, operation and maintenance instructions for this engine.