How do Muscle Wires® drive Dr. Johnson's Clean Heat Engine?ConceptsThere are some basic concepts we should review before we discuss the clean heat engine. Do you remember the three fundamental machines? The ancient Greeks know of the lever, the wheel (Put a rope around it and you have the pulley. Make it small and it's an axle), and the wedge or inclined plane (wrap it around a shaft and it becomes a screw). We use the wheel in two forms- as a pulley, and as a gear. Plus a new material you probably have never seen before- Shape Memory Alloy.  The PulleyA pulley consists of a disk, turning on a shaft, with a rope or other long flexible object running over it. The pulley changes the direction of a force, but the force on the left and right sides are the same. Well, they aren't perfectly the same because there's always some friction in the shaft, but usually we can make the shaft and bearings good enough that the forces left and right are very close to the same. Let's say someone pulls on one side of the rope. The pulley will immediately rotate to reduce this uneven force. The pulley will continue to rotate, very fast, until the force on one side reduces and/or the force on the other side increases, and they are again in balance. The Gear A gear always connects two or more shafts, and it ensures that the shafts turn at speeds that are in a fixed ratio. This ratio is defined by the number of teeth on the two gears, known as the gear ratio. If for example one gear has 20 teeth and the other has 30, then the first shaft will make one and a half revolutions each time the second shaft turns once, i.e. the first shaft turns at 1.5 the speed of the second. The gear ratio also determines the relative force (called "torque, which is in opposite ratio. So in this example, if we turn the first shaft with a torque of 15 inch-pounds, the second shaft will see a torque of 10 inch-pounds. What is a Shape Memory Alloy?Shape Memory Alloys (or SMAs) are one of the newer forms of metal. They are alloys, meaning that at least two metals are melted and mixed together. SMA alloys have two different crystal structures, and change from one to the other based on temperature. When cold the alloy is soft, longer, and easily deformed. When hot the alloy is shorter, stronger, and most importantly actually "remembers" its original shape. There are many discussions of this effect online. For example here is a link to the wikipedia discussion on this subjecdt This leads to some very interesting uses. This class of alloys was first discovered when a researcher made some with a particular mix of metals looking for high corrosion resistance. It didn't look unusually promising, so he crumpled up some thin foil and tossed it into an ashtray. Later someone stubbed out their cigarette- and the foil flattened itself! One early use was as a tubing coupler. You can form a ring of SMA metal a little too small to go over two pieces of tubing. Now cool it until it is soft, and stretch it. Put it over the pipes and heat it. It will shrink and become very strong, sealing the tubes together tightly. There are a number of medical uses. It is very useful for orthodontic braces, and it is used for eyeglasses. When formed into a wire is has other interesting uses. It can replace motors and solenoids as an actuator. It can be heated by ambient temperature, by a heating source, or by electric current flowing through the wire. Like a light bulb, both heating and cooling can occur quite quickly. When heated, these alloys contract similarly to a muscle and are sometimes referred to as "Muscle Wires®". For commercial applications, where SMAs with high repeatability are needed Flexinol® actuator wires are used. A more thorough discussion can be found at: http://www.dynalloy.com. The main point, is that movement occurs through an internal "solid state" restructuring in the material that is silent, smooth, and powerful! For the clean heat engine, we use Muscle Wire® formulated so it changes phase at about body temperature. Energy
The online encyclopedia Wikipedia defines energy as "a scalar physical quantity that is a property of objects and systems which is conserved by nature. Energy is often defined as the ability to do work." Heat is a form of energy, because it can be used to make steam and turn a generator. A thrown ball has energy, called kinetic or moving energy. Some forms of energy are more useful than others. A river running down a steep slope has a lot of potential energy, hich we can use by building a dam, storing the water, and using it to turn some form of wheel or turbine. Some forms of energy are very difficult to extract. 
Our modern lives and economies use a lot of energy. Almost all that energy currently comes with unwanted environmental side effects. There probably is no bigger problem facing the world today than finding enough affordable energy that doesn't harm the environment. Let us be clear- we at insight are techies. We like factories and industry and new cool useful stuff. 
There is a valid debate about how severe these side effects are, how urgent it is that we reduce or eliminate them, and where the right balance is. But there is no question that we need to something. We feel that to keep those things coming we must find ways to have all those factories and use all that energy without polluting or bankrupting ourselves or overheating our planet or otherwise doing harm. 
Heat EngineA heat engine is a machine which turns heat into usable energy. There are many common heat engines in use in modern industrial societies. The steam engine, used initially to pump out mines and drive trains and ships, was the first industrial heat engine. How it works:Dr. Johnson invented a way to use a coiled spring of SMA wire to make a heat engine. Recently the foremost manufacturer of SMA actuator wire, Dynalloy, Inc. has been working to make this technology a real source of usable energy. The key feature in this heat engine is the two-to-one gear between the two upper pulleys, as we shall see in a moment. 
Note that the left upper pulley is going at half the rotational speed of the right upper pulley. In other words, there is twice the length of spring going over the right upper pulley compared to the left. With a normal metal spring this would not work- the pulleys would rapidly stop. For this clean heat engine, the unique properties of SMA wire make this work. Remember that in the cold water the wire becomes longer and quite soft. Therefore the cold spring stretches to twice the length of the hot spring, and does so with very little force. How strange- twice as much length of spring goes into the hot water as comes out! What's it good for?Finding a good supply of clean, affordable energy is probably the biggest challenge facing the world today. The clean heat engine you have here is not the solution to that problem- it just shows a new possibility. We believe that within our lifetimes a descendant of this will be an important part of the solution. Current renewable energy sources like geothermal require high temperature, but this technology does not. The clean heat engine runs nicely on water about the temperature of your shower! That kind of heat energy is far easier to find. A bigger cousin to this could be designed to use surface sea water (which is hotter) and deep sea water (which is much colder), or solar-heated water, or industrial waste heat, or just a metal sheet or black plate in the sun. We're not ready to build that one yet, but we're working on it. |
||||||||||||||||
|
||||||||||||||||
|
