Green Power

Making a Case for Power Factor Correction as a LEED Credit

By J. Michael Pearson, P.E., Senior Electrical Engineer, DLR Group, Phoenix -- Consulting-Specifying Engineer, 6/1/2005

In this era of green architecture, there is one sustainability tool at our disposal that has been most underutilized—the technology of power-factor correction. In fact, the U.S. Green Building Council would do well to include power-factor correction as one of its credits for its Leadership in Environmental and Energy Design certification program.

We engineers know power factor (PF) mainly as a mathematical expression of the efficiency with which electrical energy is used. More specifically, it is the ratio of "apparent" to "real" power, or even more precisely, the cosine of the angle between these two electrical vectors. And while this famous power triangle is among the first lessons taught in engineering school, its significance too often becomes overshadowed when one gets down to the business of designing building systems.

There are several reasons for this, and they have, largely, to do with economic realities. First and foremost, there is the fact that poor PF is easy to ignore. While power companies have long paid lip service to the drag poor PF exerts on the nation's power grid, users have had little or no financial incentive to improve. On the supply side, downside effects are masked by the money being made. On the demand side, operating budgets routinely account for standard electric rates, a practice that covers up the system's inefficiencies.

Simply put—and this is a characteristic common to nearly all forms of inefficiency—there currently exists little financial incentive to improve. Even considering the fact that utility company regulations almost universally provide for the assessment of penalties for poor PF, such regulations are seldom enforced. As a result, like most speed limits, the penalties are generally ignored.

To appreciate the impact PF has on the economy, it may be instructive to consider a simple hypothetical case. Say the PF for an average building is 80%. What this means is that 80% of the energy used actually goes to lighting, cooling and running the owner's equipment—and that the 20% balance is wasted. Also consider that, according to the U.S. Dept. of Energy, the total amount of energy consumed by the United States in 2002 was almost 99 quadrillion BTUs. This would mean that almost 20 quads were wasted that year. Translate that figure into tons of coal and barrels of oil wasted—not to mention the cost of tons of carbon dioxide and hydrocarbons being released into the atmosphere—and one can see the why power-factor correction is vital.

But another reality, one that electrical engineers are compelled to take more to heart, is the need for excellent power quality. While they may be aware of the existence of less than optimal PF, designers have learned to avoid the voltage transients created by the conventional capacitor banks used to solve the PF problem. The potential improvements to energy efficiency are simply not worth the drawbacks to sensitive electronic systems and equipment.

Most conscientious engineers will immediately shout "power quality" when someone proposes PF correction. And since the past is the best predictor of the future, they are amply justified. In the digital age, the phenomenon of the capacitor-induced transient voltage has been one of the strongest arguments against power factor correction. Due to the fact that the products that are commercially available today involve relatively large, stepped cap banks—the operation of which can wreak havoc on electronics—avoidance has rightly been an almost universal reaction. Furthermore, when we acknowledge that direct financial incentives are virtually nonexistent, we can see why the risk has almost invariably been judged to overwhelm the reward.

However, ideas introduced in the last ten years hold real promise for solving even the largest of these issues. The related technology uses variable-impedance circuits, coupled with sophisticated monitoring and control equipment in filters that, applied on a small scale, have virtually eliminated damaging voltage transients in electronic equipment. Along this line of reasoning, formal LEED recognition of power-factor correction could serve to encourage technical advances.

Enter the USGBC's Leadership in Environmental and Energy Design program. LEED, as many engineers know, is a phenomenon that is gathering momentum at an impressive rate, inducing more architects and engineers to become certified, and enticing more owners to demand that their buildings be LEED-accredited. LEED ratings have become a badge of honor for modern buildings, and as such, are much sought-after by owners wanting to be good citizens.

According to Jeff Stanton, AIA, principal, SmithGroup, Detroit, "The purpose of LEED is really to facilitate positive results for the environment, occupant health and financial return. It will also help to promote whole building integrated design."

Which brings us back to PF. Supporting the efficient use of resources is exactly what power-factor correction is all about. Consequently, it is in the interest of the green building movement to acknowledge the positive impact that improving power factor can have in this area.

Even with these possibilities in mind, the case still needs to be made that the indirect savings associated with successfully reducing the "drag" of poor PF are worthy of serious consideration. U.S. DOE studies suggest that buildings make up 65% of the load on the U.S. power grid. If we say that the average power factor for these buildings is 85%—an optimistic figure in my estimation—it's obvious that the potential amount of energy to be saved is significant. Look back to the hypothetical above. For example, each percentage point of power-factor correction could reduce annual U.S. energy consumption by a billion BTUs. And since so much of the energy comes from coal- and oil-burning power plants, this equates to millions of barrels of oil and millions of tons of coal per year.

In terms of carbon dioxide and particulate emissions—well, one would have to plant literally millions of new trees every year to have the same effect on the atmosphere as power-factor correction.

This diversity of potential savings has historically sparked little enthusiasm, however, because the immediate beneficiaries would be the power utilities—not the people footing the bill. But just as recycling a pop can or a piece of paper, or reusing a brick, are like raindrops in the ocean, the cumulative effect is worth our attention now. After all, we know how impressive the ocean can be.

And as recent massive outages and brownouts on both sides of the country have demonstrated, the North American power grid can use all the help it can get.

Perfecting the power factor of the building-related loads would overnight have the same impact as bringing countless power plants on-line.

Perhaps the reasons given are compelling enough to encourage the U.S. Green Building Council to recognize power-factor correction as a distinct credit in the category of innovation and design process, with status equal to erosion control, water-efficient landscaping, recycling and other LEED categories. Power-factor correction is one potential tool in the sustainability toolkit that could have a big impact with a modest effort on the part of design professionals.