It is precisely the sort of thing advocated by Mr. L.T. Thomasson, PE, in the June issue of Power Engineering (p. 7) that injures us as a profession and industry.
The electrical power industry is involved in the conversion of energy from one form to another, and the delivery of this energy to customers. Mr. Thomasson apparently does not understand the basics of such devices as incandescent light bulbs. If an incandescent bulb is operated at a lower voltage, the lumens of light produced decrease markedly, and the overall power consumption per lumen of light produced goes up. The same applies to other types of light bulbs. A great deal of effort has gone into the optimization of light bulbs so as to maximize the efficient production of light, just as a similar effort has gone into the optimization of all our appliances. To operate these equipments at other than the design voltage, which is standardized at a utility service voltage of 120 V plus or minus 5 percent, insures we lose the efficiency designed into the devices, and further shortens markedly the life of most motor-driven appliances. It is precisely for this reason that utilities are reluctant to cause a “brown-out” by reducing the voltage on the system rather than use rolling blackouts to achieve a reduction in the system load.
As many devices draw more current at lower voltages, many of the losses in the system increase by a factor of the square of the current (remember I2R losses). In no case will the reduction in voltage levels reduce the energy required by the consumer unless he is wasting energy. Switching-type power supplies as used in many electronics devices require power input to develop the required power output, the differences in output and input being the losses in the system, just as other electrical devices. There is nothing magic about their function. While these devices may tolerate large changes in supply voltages, they are not more efficient at lower voltages than the design value.
There is no free lunch, and despite what I have told a few people, there is not really an energy fairy either. Professional engineers should be embarrassed to propose such schemes, and Power Engineering ought know better also. We professional engineers ought be educating the public on the reality of our energy situation, and above all we ought not be proposing foolish schemes that infer there is some magic fairy with a wand who will solve our problems. If consumers can get by with a 60 W bulb instead of the installed 100 W bulb, they ought do this. However, let us not infer that a 100 W bulb operated at a reduced voltage supplies the same light as it does at the rated voltage. Let us not infer that the average household could save energy costs by reducing their voltage. Let us not fail to understand the fact that much effort on the part of many electrical engineers has gone into the improvements in efficiency of many appliances, and that this efficiency improvement has been based on a nominal operating voltage for the device. When operated at a different voltage, the efficiency will in almost all cases decrease. In some cases this may also result in adversely affecting the life of the device as well.
Professional engineers need to exercise great care in what they write and publish since they are likely to be trusted sources of policy guidance to those involved in the process who do not possess their supposed level of understanding and technical knowledge.
Colin M. Jones P.E.
Captain USN (Retired)
Mr. Thomasson is ill-informed about the most basic of electrical principles: power equals voltage times current (in a purely resistive circuit). Lowering voltage increases current draw from the load – always. This increased current will result in lower efficiency and less system capability due to higher voltage drops in wiring and other internal components.
From my experience as an electrical operator on a nuclear sub, let me tell you that I have tweaked an electrical distribution system every which way but loose and when, after a reactor scram, I needed as good a rig-for-reduced-electrical as possible to reduce battery drain, I always cranked up my AC system voltage. It was the first thing every good operator did (actually I was raising the power factor from 0.8 lagging to near unity). I wonder if Mr. Thomasson ever thought about why utilities use such high voltages for transmission lines.
James R. Williamson
Fort Collins, Colo.
Mr. Thomasson has raised an interesting point regarding the effects of voltage reduction on electrical power systems. The idea of reducing demand and energy consumption by reducing voltage was investigated extensively in the late 1970s in California.
At that time, American National Standards Institute (ANSI) Standard C84.1-1970 specified two voltage ranges, Range A and Range B, which included both service voltage and utilization voltage. Service voltage for this situation was usually interpreted to be at the meter, and utilization voltage was at the terminals of the utilization equipment. Electric supply systems were to be so designed and operated that most service voltages would be within the limits specified in Range A. The occurrence of service voltages outside Range A was to be infrequent. Range A service voltage was to be 120 V (+/-5 percent), which would be 114 to 126 V. Range A utilization voltage was specified to be between 110 and 126 V. Voltage outside of Range A would be in Range B.
The California Public Utilities Commission directed that the service voltage provided by the utilities should be 120 V (+0/-5 percent), or between 114 and 120 V. This requirement put a great strain on the utilities to maintain the system-wide service voltage between 114 and 120 V.
Subsequently, the three major investor-owned utilities in California conducted tests to determine the amount of real energy reduction that would occur on a typical distribution circuit operated at reduced voltage. They ran reduced voltage tests on many circuits and individual appliances. The final result was that with a 5 percent voltage reduction on the distribution circuit, there was about a 5 percent energy usage reduction and a 5 percent demand reduction. Beyond the 5 percent reduction, many electrical devices started to malfunction or the energy reduction leveled off. There were many tests done on resistive heating appliances such as toasters and fry pans, which just required longer cooking time at the lower voltage, as pointed out by Mr. Thomasson. Most electric motors could operate at the reduced voltage and operated more efficiently but there was a definite limit as to how far down the voltage could go and still operate. Television sets at that time experienced a reduction in the picture size. Most appliances did not operate at a constant kVA and therefore did not draw more current at the reduced voltage. They simply did less work over a given period of time.
In conclusion, I would say that this subject has been given a “broad-based industry-wide analysis.” The conclusion was that voltage reduction works only up to a point. It has been demonstrated that voltage reduction is only effective within the 5 percent range without degradation of equipment performance.
Phillip L. Wheeler, P.E., Consultant
Dove Canyon, Calif.
Mr. Thomasson proposed cutting voltage to address the inadequate power generation capacity on the West Coast. In my area, we usually have one to five days without power each winter. We didn’t have to wait for a statewide crisis for practice. All-electric houses were once glorified as “Gold Medallion,” but when the power goes out, you use flashlights, not candles, because there is no fire department, you eat cold canned or dry food while you worry about the fish and steaks in the refrigerator, you cringe thinking about your critical path schedule on the work you promised, you crawl in bed early before you get chilled, you use paper plates and don’t wash the last dishes, and you carry buckets of water to flush the toilet.
Lowering voltage on a short-term, emergency basis might have usefulness, but Thomasson proposes going even further, “the proposed voltage goal might even be lowered to 100 VAC, leading to a 20 percent reduction in line voltage and a 36 percent reduction in resistive heating and lighting power loads.” My electric water pump would burn out. I would have to buy some more heaters to compensate for the existing inadequate ones. My computer may not be like “most” and burn out too.
Along my Northwest coast, air conditioning load is non-existent, but government says “one size fits all” and pushes fluorescents. Incandescent lights are more efficient here because they provide light as well as distributed heating. Politician-lawyers redesigned toilets to use less water. Now you have to flush two or three times, then get out the plunger. Government may reduce voltage. Too bad I can’t use the politician lawyer hot air, but with the help of wood, sun, and water, I’ll get off the centralized grid somehow.