Dear Dennis...
EN-Genius Network's Dennis Feucht answers your design
queries in his new Circuit Design Clinic!
April, 2010
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EN-Genius Network presents a new, interactive
analog design service to readers! Send us your design questions (with
relevant data; schematics in JPEG or GIF, please) for some free
engineering advice from EN-Genius Network's circuit
consultant, Dennis Feucht, on how you might solve a design problem or
improve circuit performance. Submissions may be edited for clarity or
brevity, and submitters and their email addresses will remain anonymous
(unless otherwise indicated). Please send your questions to Dennis here.
Practical Eco-Electrical Home Power Electronics
&
Your Own Eco-Electrical Home Power System
by Dennis L Feucht
Practical Eco-Electrical Home Power Electronics
by D Fichte, Published by Elektor International Media BV
ISBN 13: 978-0-905705-83-5, paperback, 150 pp, $34.15, November 2009
Your Own Eco-Electrical Home Power System
by D Fichte, Published by Elektor International Media BV
ISBN 13: 978-0-905705-82-8, paperback, 76 pp, $25.96, September 2009
The first book presents selected topics in the power electronics of “alternative energy” or eco-electricity, as the British call it. It begins by considering the optimal off-grid power system strategy and concludes that a high-voltage dc (HVDC) system based on a 170 V dc bus is more efficient than using a 12 V battery bus in most residential and small business uses. A brief outline is given of a HVDC bus design with control of multiple power sources.
The subsequent chapters cover electric system components, one chapter at a time: solar chargers, battery-driven inverters, battery chargers, and wind converters. Circuit diagrams traced from popular commercial products are accompanied by detailed explanation and analysis, such as the Xantrex C-60 solar charger, Black & Decker (formerly Vector Mfg) inverters for automotive use, and Vector and Schumacher off-line (from a generator, for the eco-electric case) battery chargers. Low-cost battery inverters designed to be kept in trucks for occasional use can be retrofitted for continual eco-electric use with some minor design modifications. This includes replacement of the fan with a long-life ball-bearing fan. The converter topology deemed optimal for low-Rin (low voltage, high current, such as from battery banks) applications is developed with engineering design equations worked out. Some practical aspects of system maintenance, such as fan repair or refurbishment, are included.
The chapter Wind Converter Circuits explains the electric machine as a system component with an electrical-mechanical model and development of the basic design equations for using a motor as a wind generator. Then what the author considers the optimal topology for wind converters is developed in some detail. It is a half-bridge series-L converter. This topology has a half-bridge primary circuit and an inductor in series with the secondary winding, followed by a full-wave rectifier – just the opposite order as a forward converter. This circuit is more complicated to analyze, but the analysis is worked out, with design equations and benefits expressed numerically. Voltage and current waveforms are both illustrated as are oscilloscope graphs of the rather odd-looking voltage waveforms that conform well to the basic theory, as presented. (Beware of some equation errors on the bottom of pages 117 and 118.)
Going beyond components, the book then addresses the kind of power supplies found in typical household loads. Those with transformer-input supplies are not suitable for direct 170 V dc routing; most else are. The fluorescent lamp chapter shows the FL model for engineering use, replete with circuit diagrams of three compact fluorescent lamps (CFLs), traced out from commercial products. CFL driver repair is covered briefly. (There is not much to it.) The circuit diagram of a tubular emergency FL is also given. A chapter on LED lighting gives a flashlight LED driver circuit and discusses some design considerations.
A final chapter presents an alternative approach to solar electricity, that of using solar thermal instead of solar PV. A solar collector heats a liquid in an insulated tank; thermoelectric modules (TEMs) designed for power conversion are applied to it, with backsides cooled by an automotive radiator scheme. The engineering model for TEMs is given in some detail for design purposes. A cost comparison with solar PV shows solar thermal to be 2/3 or less the cost for a comparable system. The lack of batteries to wear out is a major feature as well as the decoupling of solar energy collection and conversion, which results in an additional advantageous free variable in the system design.
The second book is actually the first in the two-book series and is less technical than the second, though it contains basic information on solar panels, battery banks, generators, power distribution, loads and the use (not design) of eco-electric power components. It does provide some useful design information, such as a wire table and battery life-cycle and discharge charts, though it is mainly intended for the semi-technical installer and maintainer of eco-electric systems such as homesteaders and resort operators. Brief final chapters include wind and stream generation, home-made ethanol production, and how to size components for a given set of system requirements.
The two books taken together form a complete set, with the electronics sequel referring here and there to material in the first book. For anyone with a technician (first book, second as listed above) or engineering (second book) understanding of power electronics, these books taken as a set offer a detailed presentation of not only what is inside commercial products but also how to improve on them by using optimal design schemes not found in them. For the engineer, these books as a set, present an in-depth look at eco-electric power electronics design, commercial manifestations, and its use.
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