Since most of the electricity in the world is generated by the burning of fossil fuels, developing better systems for the more efficient use of electric power will be an essential part of the solution to the global warming crisis. Almost all modern office equipment made in the last ten years has become world wide compatible, but operates with a power factor of only 55% to 65%. This is the typical power factor for virtually all modern switchmode power supplies operating from a single phase AC supply, because although they are efficient DC to DC converters, they are fed by a classic bridge rectifier and filter from the AC supply. Modern LED lighting systems currently being introduced operate from AC with a typical power factor of 40% to 45%.
Although rectification and filtering has been the classic and universal method of turning AC into DC, it is a very inefficient and wasteful SUV-like approach to electrical consumption, where only the voltage peaks are used, and the rest of each waveform is wasted. The wasted 35% to 45% goes back into the grid as higher order harmonics of the power line frequency, which do no useful work, and harm the grid and other equipment. Harmonics are an electrical pollution which overheat utility transformers and neutral conductors, and cause AC motors to draw more power to do less work. Additionally, as the input current to the rectifier becomes more discontinuous, the current peaks become proportionately greater, and circuit losses rise as the square of the current, adding to the losses from poor power factor. Fig. 1 illustrates these waveforms. Note that work is done only when both voltage and current are present, and that is a small percentage of the total time.
Coherent Power has developed and patented technology which integrates modern power factor correction techniques with modern switchmode power supplies. In higher power applications, it can be integrated into existing products, or be used as an add-on. For multiple low power devices, such as the typical office full of computers, monitors, printers, scanners, and copiers, etc., an add-on device which can operate from 20 to 60 computer systems has been designed and a demonstration unit constructed. This device can power all the office equipment and LED lighting in a typical small to medium office, requires no internal changes to existing equipment, and reduces the power otherwise consumed from the grid by at least 35% to 45% by operating at near unity power factor. This is much more cost effective than trying to integrate power factor correction into each individual computer or peripheral device. Output connection and distribution to computers with standard IEC cords and distribution strips simplifies retrofitting existing offices, and provides maximum versatility.
As an additional benefit, this design can function as a superior UPS (Uninterruptable Power Supply), by being able to switch over to standard 48V battery systems as a backup source if the main power source is interrupted, without any change in output to the equipment, and waiting 10 seconds after return of main power to switch back. When operating from the main supply it provides the charging function to reach and maintain the proper float level for the battery system.
Since DC is being supplied to the equipment at all times, at least 35% to 45% less energy (55% to 60% less for the LED lighting) is consumed from the batteries as well. In UPS systems for computers and their peripherals, the conventional method of inverting from batteries to AC (so that they then waste at least 35% to 45% due to their poor power factor) makes no sense whatsoever. By correcting power factor to unity when operating from the grid, and eliminating a needless inversion to AC when operating from batteries, a superior UPS results, which reduces the electrical consumption of computers and their peripherals by at least 35% to 45%, and LED lighting by 55% to 60% at all times, from all sources.
Additional versatility comes from the ability to operate from either AC or DC as the main supply. What this means is that in addition to being able to switch between the AC grid and the battery system as just described, it can switch between a solar array and a battery system in off-grid applications, or blend the solar array with the AC grid and/or the battery system as required.
Coherent Power is actively seeking suitable manufacturers to license and produce the new products made possible by this body of intellectual property, trade secrets, and mature, tested designs. Below is the original prototype which has been running the entire Coherent Power office continuously since March 2007, through countless power outages which are common in this coastside area. A new portable demonstration unit has been constructed to facilitate demonstration to prospective licensees.
* Can run on 95 to 170 Volts AC or DC as main supply, and 48 VDC backup supply.
* Seamlessly switches to backup supply on loss of main supply, preserving critical data.
* 10 second delay on switchback when main power returns protects from erratic return of power.
* Charges backup batteries when running from main supply.
For further inquiries, contact: Coherent Power, Ltd. 169 Stanford Avenue Princeton, CA 94019 Mail: PO Box 2133 El Granada, CA 94018-2133 Tel: 415-412-6670 Web: http://www.coherentpower.com General and Marketing E-Mail: firstname.lastname@example.org Technical E-Mail: email@example.com
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