The Environment and Oberlin: An Update

Page 5

The True Energy Picture

After more than two years of operation we can now evaluate the Lewis Center’s energy performance. So far the building has been powered mostly by coal, not sunlight. In its first 27 months of use, the rooftop photovoltaic array produced 70,000 kilowatt-hours of electric energy, only 17 percent of the 420,000 kilowatt-hours of energy consumed by the building (including transformer losses and parking lot lights) during this same period. The bulk of the energy was purchased from the local power company.

The architect and I have independently presented energy simulations for the as-built structure. R. Perry, managing partner of WM+P, presented the results at a public lecture in October 2000 in which he acknowledged that the original projections did not apply to the final building. My results were presented in March 2001 and will be published this year in ASHRAE Transactions. Both confirm that, as designed and constructed, the building, under normal use, is expected to consume two to three times more energy annually than the photovoltaic array can supply.

It is now quite clear that the excessive energy use is not the result of poor operating procedures or changes that came about during construction—it is largely the consequence of WM+P’s mechanical design completed in October 1998. The original energy claims were nothing more than speculation. There is not now and never has been any factual basis for the energy claims for this building. Oberlin has completed an extensive commissioning process verifying that the Lewis Center was built per construction documents and that systems are operating per specifications. This process uncovered many problems that have been subsequently corrected, resulting in lower energy use. But the major causes of excessive energy consumption remain because they are associated with the building’s very design.

Actual energy consumption depends on weather, occupancy (how much is the building used), and the inside temperatures maintained during use. In the last 12 months, the energy use by the Lewis Center has decreased to 130,000 kilowatt-hours, of which the photovoltaic array furnished 46 percent. There are many reasons for this reduced energy use, including the fact that northeast Ohio experienced its warmest winter in 50 years. (Indeed, heating energy for all College buildings was reduced by 10 to 20 percent.) This performance, while interesting, does not change any of the facts already presented.

In evaluating the Lewis Center’s performance, it is important to separate energy consumption from the energy generated by the photovoltaic array. A $420,000, 45-kilowatt array can be installed on the roof of any building and instantly lower the amount of energy the building imports. The benefit is clear, but it says nothing about the energy-efficiency of the building itself. As a leading advocate of photovoltaic power has frequently said, you don’t make a conventional building green by simply adding a photovoltaic array to it.

As constructed (absent the photovoltaic array) the building is expected to consume 150,000 to 190,000 kilowatt-hours of electric energy annually, assuming average weather and occupancy. This corresponds to an on-site or site energy use of 35,000 to 45,000 British Thermal Units (or BTUs) per square foot per year. But site energy fails to account for the associated energy consumption and pollution that occur at off-site electrical power plants that run at 30 to 35 percent efficiency. The EPA and Department of Energy use a concept called source energy, which considers the total energy use—on-site and off-site — associated with a building’s operation. For the all-electric Lewis Center, the source energy is three times its site energy. Hence the projected source energy use is 110,000 to 140,000 BTUs per square foot per year. One of the ironies of this debate is that Oberlin’s Environmental Studies faculty members focus on site energy rather than source energy, ignoring the off-site pollution and energy consumption associated with operating the building.

The source energy consumption for the average non-residential building at Oberlin is about 130,000 BTUs per square foot per year. Hence, without the photovoltaic array, the Lewis Center is projected to consume about the same amount of energy and cause the same amount of pollution as a conventional College building. Because of its photovoltaic array, it does much better—but the credit goes to the photovoltaic array, not the building design. Oberlin could have achieved far more energy savings by constructing a conventional building at half the cost and erecting photovoltaic arrays on seven other buildings.

Can this design be fixed? Of course—and the College has begun this process, authorizing $100,000 to replace the 112-kilowatt electric boiler with a ground-source heat pump. But this change is not without consequences, as it increases significantly the amount of heat that will be taken from the ground, probably lowering the winter water temperature below the acceptable range of the 23 existing heat pumps and requiring that they be changed as well. And there are many other heating, ventilation, and air-conditioning (HVAC) system design flaws that must be addressed for the building to reach its original target. No one knows how long this will take or how much it will cost.

Is the building, on the whole, a good thing for Oberlin? Yes! It provides many educational opportunities to learn about our built environment. I have focused on the failures in the mechanical design. But even with these, the Lewis Center, with the boiler removed, is more efficient than a conventional building. Its lighting design, extensive use of natural lighting, and HVAC control system are exceptional at saving energy in ways not found in other campus buildings. The facility is a bright and delightful space in which to work and learn. And its rooftop photovoltaic array provides a large fraction of its energy. If the College continues to correct the mechanical design flaws, I expect that over time it will move closer to its original energy targets.

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