Fall Update 2016The Axial Flux AlternatorNote: the following is a continuation of the work described in the Winter 2015/2016 update.The generation of electrical energy is an essential part of creating energy sovereignty at the village level. As a result, a key part of B2M involves weaving the ability to convert woody biomass into electricity into this work. Given society's current dependency on automobiles that burn liquid fuels, B2M's primary goal is to convert woody biomass into a fuel that can be burned by today's fuel-flexible cars, but such a fuel will only capture about a third of the energy contained in wood. The remainder will leave the process as some form of what's known as "sensible" energy; i.e. energy that you can sense as the heat you feel in your car's exhaust. In a state-of-the-art coal fired electrical plant, more than half of the energy in the coal is lost as sensible heat. A key part of the suite of techniques that make up B2M involves ways to capture sensible heat and put it to use in the community. One way to do that is with a heat exchanger that uses the hot exhaust to heat domestic water or warm a greenhouse. As long as there's sunshine, our greenhouses are pretty much self-heating, but when the sun's not shining, the sensible heat that B2M gives off is a viable option. While liquid car fuel is the "holy grail" of biomass conversion, a reasonable argument can be made that electricity is the form of energy that is most essential to the sustainable operation of homes and villages. Try to imagine what life would be like without electric lights, refrigeration or washing machines, and you'll get the idea. Even one's ability to utilize other forms of energy such as natural gas depends on electricity for control and ignition circuits, and to power the fans that move the warm air around the home. Two key parts of B2M that generate sensible heat are the reactor where syngas is condensed into methanol and in the wood gas powered hydraulic pump that drives the compressor. The reaction that combines carbon monoxide and hydrogen to produce methanol is exothermic; i.e. it gives off heat. To keep the reactor from overheating, a heat-exchanger draws off the heat of reaction by using it to boil water and produce steam. At another stage of the process, wood gas is burned in an internal combustion engine to power the hydraulic pump that operates the compressor. The engine exhaust is hot enough to generate steam to drive a steam engine and recover some of the energy that otherwise would be lost. In both cases, the heat exchanger functions as a flash boiler. Once it's up to temperature, small amounts of water are injected into the heat exchanger where it instantly turns into steam. A key design aspect of a flash boiler is that there's no body of superheated liquid water inside the boiler, a feature which makes a flash boiler inherently safer than the traditional sort of boiler. It's a design that is inherently safer, and in keeping with our commitment to ensuring that B2M is as safe a design as we can make it. If you've watched someone prepare a latte by blowing steam into milk, that steam was generated in a flash boiler. Once we have steam, the next step involves converting it into electricity; that's were the Axial Flux Alternator comes in. AFAs were developed for use in windmills and are designed to operate at below 500 rpm instead of above the 5,000 rpm that automotive alternators run at. The lower speed reduces the internal stress in the alternator to the point where an AFA can be manufactured and maintained in community using readily available tools, and bearings can be fabricated on-site. The neodymium magnets, on the other hand, have to be purchased, but once acquired they'll generate power for a lifetime. To test out the concept of using steam power to generate electricity, we acquired a 1 horse power steam engine manufactured by Mike Brown Steam Engines. At this point in the research process, we're using compressed air to power the engine; once all the operational details are worked out, we'll switch over to using steam, but we prefer to go with compressed air because it's inherently safer. Last summer, Ruben worked out the details of how to digitally track the engine's rpm so that we could use an Arduino to control the steam engine's operational speed. This summer, Yosef completed the initial work that Oana did on our AFA. With the AFA up and running, we're one step closer to our goal. Here's a pic of our air-powered steam engine driving the AFA; the glowing headlight shows that it's generating lots of electricity.
Thank you again for your faithful support; it's what makes this work possible. ~~ Walt Here's a pic of Yoseph showing off our latest stator. He's holding it up so that sunlight shines through to show the placement of the nine internal coils where the electricity is generated. This is the second stator we've cast for B2M, as we test out various options. Because the design specs for our application are different from a wind generator, we expect that we'll have to make up a series of stators using different wire sizes and number of turns in order to settle on the design that will optimize the conversion of thermal energy into mechanical energy into electricity. This work is key to what makes B2M different from coal, oil or natural gas powered on-demand energy systems that convert one third of the input energy into electricity. B2M is designed to convert that "easy third" into liquid fuels, and then to go on to use a series of additional steps to use the "waste" energy to meet the village's electrical and residential heating needs. By operating as a village energy system, B2M can look to achieve energy utilization rates in the 90% range. That level of efficiency translates into much lower pressure on the village's forest to supply biomass, hence increased system sustainability. Thank you again for your willingness to have faith in this project, and to help support the work. We couldn't do this without you. ~~ Walt |
