Questions About Article & John Petersen's Response
written by HPB Admin , December 14, 2011

Questions about Article
The author, John Petersen, cleverly packages his energy production and consumption data for Oberlin College's Adam Joseph Lewis Center to argue that the building has a net-negative annual site energy (i.e., generates slightly more energy than it consumes). But a close reading of his argument reveals that the time frame for his energy consumption average differs from that of his energy production average. In short he argues that "this year we generated more energy than we used last year." The relevant question, of course, is did the building generate more energy this year than it used this year?

Mr. Petersen does not provide us with a graph of annual energy consumption and production by year. If Mr. Petersen showed us this graph it would clearly demonstrate that there is not one year in its 11 year existence for which this building has generated more energy than it consumed. Most recently -- the first nine months of 2011 -- the building has purchased 35,000 kWh of energy from the grid.

John Scofield, Professor of Physics, Department of Physics & Astronomy, Oberlin College

John Petersen’s Response
There is ample room for legitimate disagreement regarding the most appropriate approaches for assessing the past performance of a building and predicting future performance. I welcome debate on this issue. However, I stand by the twin approaches that I took to capturing and conveying the first ten years of energy performance of the Lewis Center. Mr. Scofield faults me for not providing a graph of annual energy consumption and production by year. However, figure 1 on pg. 24 of the article displays our assessment of ALL available electricity production and consumption data stacked by end use averaged within months over the entire duration that we have gathered data. In my view this provides the reader with the capacity to develop far greater insight into important seasonal patterns as well as magnitudes of energy metabolism in the facility. I’m not clear how the more detailed depiction that I provide in the article constitutes “clever packaging” as Mr. Scofield asserts.

Mr. Scofield has invented a quote for me that I have not written in the article (“this year we generated more energy than we used last year"). I assume he must be referring to figure 2. The legend of this figure makes very clear that the analytical approach I took was to average data for each variable over ALL available data in the database since January of 2001. Since we have consumption data and rooftop photovoltaic production data back to that time, this is what I used for these variables. Since the parking lot array was installed in June of 2006, I used ALL data available after installation to estimate the performance of this system. Error bars described in the figure legend allow the reader to assess the impacts of interannual variability in production. It remains my view that averaging over all years for which data is available for each variable provides an affective summary of available data.

For Mr. Scofield, the most relevant question may well be, “did the building generate more energy this year than it used this year?” But I was specifically asked by the editors of High Performing Buildings to write an overview article that reflected broadly on the Lewis Center as one of the earliest green buildings and so this is what I did; Mr. Scofield’s question was not the question I was asked to address.

John E. Petersen
Associate Professor of Environmental Studies and Biology Director, Environmental Studies Program, Oberlin College

Questions about Article and John Petersen’s Response - Part 2
written by HPB Admin , February 06, 2012

Questions About Article
Mr. Petersen's statement above that "Solar panels produce slightly more energy than the building consumes" is not true. Data clearly show that, on an annual basis, the Solar panels do not annually produce more energy than the building consumes.

John Petersen's response:
Although I stand by the methods I used in evaluating and presenting data on the building, there is one important correction to the article that I must make. In the fall of 2011 (after the article was published) we discovered that the data that we have been collecting directly from a city-owned utility meter -- the data used in the HPB article as our best measure of total integrated solar production -- is in fact, inaccurate. Specifically it turns out that we have inadvertently and unknowingly been recording and reporting data on apparent power instead of real power (i.e. kVA instead of kW). This inaccuracy resulted in an overestimate of total solar production by about 6%. So, on the issue of annual energy balance, in the four complete years since the parking lot array was installed (2007-2010) solar electric production accounted for an average of 92% of what the AJLC consumed on a yearly basis. In its best year (2007) the AJLC produced 97% of what it consumed. Although numbers are sometimes close, thus far there is no single year in which total annual photovoltaic production has exceeded total annual electricity consumption. On page 27 of the HPB article I wrote that the facility produces, “slightly more electricity on an annual basis than the building consumes”. With corrections we have made to the data, the appropriate wording should be that the facility produces, “slightly less electricity on an annual basis than it consumes”. This is an important correction to make, but it is not one that significantly changes what a reader should take away from the HPB article.


The reality that the AJLC has been operating primarily on solar energy and that the facility has considerable room for improving future performance with upgrades to the mechanical systems is entirely consistent with the overall conclusions drawn in the article. Errors need to be corrected, but one hardly needs to apologize for the the corrected numbers. The reality is that we would live in a better world if it was populated by buildings that, like the AJLC: capture 92% of the energy that they use though on-site renewable energy systems, internally treat and recycled the majority of water used, restore native ecosystems, and produce significant amounts of food in the immediate landscape. But aspiration is important; I am pleased to agree with anyone who argues that capturing more solar electricity than the building consumes is a worthy goal that can and should be achieved for the AJLC. In the fall of 2011 we hired a new facilities manager and the top item on his agenda is to facilitate an extensive retrocomissioning process through which we intend to significantly reduce electricity consumption in the building. We anticipate that in the next two years, through changes in operations and repair and replacement of equipment, we should easily be able to move the energy balance of the facility from “slightly less” to “significantly more” electrical energy produced than consumed. Interested readers should visit www.oberlin.edu to explore updated real-time and historic data on building performance, to view a detailed explanation of data verification, and to track our progress towards achieving the goals we set.