Common Sense Powers Intelligent Energy Management

It's the relatively rare design today that solves a classical problem without leaning on new technology. Now and again, there's hope: Power Metrics International/MHT Lighting (Staten Island, N.Y.) is touting its series of SP1000 intelligent energy-optimization systems for ballasted lighting devices.

PMI says it cuts power delivery and usage costs by as much as 15 percent using techniques that have been around for a while. It employs a conventional triac, long-life switches, and small capacitors in its analog power-factor-correction section, and basic digital topology to monitor, calculate, and make decisions on power factor, kVAr, and total harmonic distortion. The system, for installation in electrical subpanels, is available in three versions: two for 208V service rated at up to 17kVAr, and a 480V, 30kVAr unit.

PMI revisited and carefully applied fundamentals that all this time have been overlooked, largely because few understand the real-world issues of PFC, power surges, parasitics, and system efficiency, says Hamid Pishdadian, who led the SP1000 effort.

Indeed, none of the applied technologies is unique. Using a refined capacitor-based technique to maintain power-factor close to unity, the SP1000 quickly adds/subtracts small amounts of capacitance to each leg of the system to correct for load imbalances. It also applies an advanced demand-based correction method that evaluates kVAr 128 times per cycle, doing away with the traditional fixed-value capacitor setup that corrects for average power factor. PMI also applies a rule-of-thumb technique to eliminate any capacitor values that tend to resonate with a given inductive load, which can create troublesome harmonics.

The result: a touted game-changing product in price/performance for the toughest game we now face — conserving energy.

Why doesn't “out of the box,” yet basic, reasoning prevail more often? Because designers are often hardwired to apply advanced techniques they learned in school, thus tending to pick the most difficult way to go. It brings to mind a different sort of analog problem I saw three years ago.

For 55 years, antenna experts didn't, or couldn't, solve a multiband resonant antenna problem using Maxwell's equations. One reason was that you ultimately need to readily convert parameters such as electric and magnetic field intensity and flux density into electrical parameters familiar to antenna engineers, such as voltage, inductance, capacitance, and feedpoint impedance. For whatever reasons, the pros didn't or couldn't apply the apparently forgotten notion that the antenna is often a basic extension of its transmission line.

Thus an easy solution: Use appropriate electrical forms derived from Maxwell's (i.e., the transmission-line) equations to create a set of five algebraic/trigonometric equations to determine the various inductance/capacitance elements, their placement along the wire antenna, and the dimensions of the antenna system. Then solve these nonlinear equations simultaneously — easily done, using a $12 piece of canned numerical computation software.

The solution was there waiting all the time. But textbooks (and scads of correspondence from the experts) said the problem had to be solved experimentally. No, it didn't. The experts, with all their knowledge, simply forgot what they knew.

Happily there are still a few “dinosaurs” who've learned how to lead the way. “I believe the simplest solution is always the best solution, and there are no problems that cannot be resolved just by understanding the issues,” Hamid Pishdadian told me. “Overall, we expect a reduction of 5 to 10 percent in kWh. The rest of the savings are due to a reduction in [monetary] penalties and charges for power-factor.”

In the end, all the advanced technology and think-tank procedures went out the window and let some common sense shine through. I only wish it happened a lot more often.

4 comments on “Common Sense Powers Intelligent Energy Management

  1. eafpres
    April 4, 2013

    Hi Vincent.  Nice article.  I think I read about the PFC device recently.  Reading your  comments made me think way, way back when my dad talked about doing things with the power coming into the house which would mess up the Power Factor.  My question for you is: If such devices were very widespread, would they improve the load conditions for power genration so that utilities could be more efficient?  In other words, could there be additional efficiencies gained if all loads were ideally corrected when drawing power from the Grid?

    (P.S.  My dad once rewound a 3-phase motor and build his own control system to build a rotating 2-phase to 3-phase converter.  He used it to power a 3-phase motor in a large metal lathe he had wedged into the garage.  He was unhappy with commercially available converters, and claimed replacing the motor in the lathe with a 2-phase motor would not provide enough horsepower in the space available.  I always loved hearing this whole thing spool up–you first powered up the converter and he had some kind of relay on it so that it was disconnected from the load until it reached speed; when you heard the relay close you could then power on the lathe.  The lathe motor ran continously and there was a belt-driven clutch to engage it to the drive gear of the lathe.  Quite the electro-mechanical wonder.)

  2. vbiancomano
    April 6, 2013

    In the last reckoning, the basic goal of PFC is to increase overall power-grid efficiency. Thus PFC more directly addresses the ease with which the power utility can provide energy. As such, we might reasonably expect an incremental improvement in power-grid efficiency with every effort to “match,” as it were, the load at the consumer's end to the AC mains. But by how much? Perhaps not a lot; the business involving universal “ideal” correction isn't straightforward. I'm presently awaiting word from several sources for such data on efficiency.

    As an aside, cost savings that reportedly accrue from the use of PFC and more “efficient” residential systems are another issue. Industrial users can likely avoid “surcharges” for poorly conforming equipment (an issue involving charges for reactive power). On the other side of the coin, residential users (consumers) who have PFC front-ends in their products by most accounts won't likely notice anything much in the way of a reduced utility bill.

  3. Brad Albing
    April 30, 2013

    Let us know when we can expect more info regarding PFC. It's a good topic that not everyone knows that much about, so when will you blog again on the topic?

  4. vbiancomano
    April 30, 2013

    Hopefully soon—the day I secure the kind of worthy, no-nonsense info I'm looking for. Indeed, there's a lot to talk about.

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