This presentation is being made by the Center for Renewable Energy Advanced Technological Education and Madison Area Technical College for the 2020 Hi-Tec Impact Exchange Virtual Conference. The work presented was originally described in a manuscript entitled Enlightened Education: Solar Engineering Design to Energize School Facilities that was recently published with the American Society for Engineering Education. This work won the Best Paper Award at the ASEE 2020 Virtual Conference, and we are now presenting it to the Hi-Tec audience so that we might reach a larger number of faculty and schools with an interest in pursuing solar projects. This presentation and the ASEE publication examine some of the engineering considerations and lessons learned that went into the design of a new 1.85 MW solar photovoltaic system that was commissioned in 2019 by Madison Area Technical College in Madison, WI.

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This is an aerial view of the Madison College solar photovoltaic system. The system contains 5700 solar PV panels, for a total system size of 1,850 kWdc making it the largest rooftop solar system in the State of Wisconsin. The system is composed of multiple sub-arrays that are installed over a dozen different roof sections and elevations that comprise the 1.1 million square foot facility. When skies are clear, the system produces enough electricity to provide 100% of the power needed by the building for several hours in the middle of the day. Of course, many days in Wisconsin are cloudy, and the college also teaches class at night. So, when averaged over the year, the system provides roughly 25% of the energy consumed by the building. This is equivalent to the amount of electricity consumed by about 300 average sized residential homes.

The solar system at the Truax campus was completed as part of the college’s Solar PV Roadmap. The college created the roadmap in 2018 with the assistance of the Midwest Renewable Energy Association to examine the potential for solar energy at all of its campuses and facilities. The roadmap planning team began by identifying the motivating reasons to pursue solar energy, and the top ranked goals were to provide cost savings to the district and to provide learning opportunities for students. Since the Truax campus is the largest energy consumer in the district, and it also serves the largest number of students, this building was identified as the top priority for the solar roadmap. The college also completed a solar installation at its Goodman South campus in 2019, and solar construction work is currently underway at the Commercial Avenue, Fort Atkinson, and Reedsburg campuses with projects to be completed yet in 2021. The college’s ultimate goal is to execute solar projects on all of its buildings, however, it is not practical to engage in dozens of projects all simultaneously. By creating a solar roadmap, the college was able to strategically prioritize its solar investments.

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Financial considerations were a strong motivating factor for Madison College to pursue solar power, and we are frequently asked to share economic information about the project and the value of solar energy. The project was incentivized in part by a cash grant program offered by Madison Gas and Electric that was established through a settlement agreement with the Environmental Protection Agency. The grant provided for about 20% of the system cost, and the college paid for the remaining portion. The solar panels have a 30-year warranty, so this was chosen as the time horizon for the economic analysis (note that there are many solar panels that have been operating for much longer than this in the field, so this is a conservative estimate). The system has a simple payback period of just under 10 years, and an internal rate of return of about 10.5%. The levelized cost of electricity for the system is 3.8 cents/kWh which is less than half of the retail rate that the college currently pays. Like most large educational institutions, Madison College has separate budgets for capital and operating expenses. An additional financial benefit provided by the solar system is that it allowed for investment of capital construction dollars to build infrastructure that could provide energy for the school and thereby reduce future operating costs. This sort of cost hedging approach helps to stabilize the college’s operations by locking in a portion of the school’s future energy costs, making for more controllable and predictable budgeting.

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Learning opportunities for students was another strong motivating factor for Madison College to pursue solar energy. The college has had a Renewable Energy Certificate program since 2005, and solar energy is a predominant technology featured in the program. The foreman on the solar installation was a Madison College alumnus, and several of the people on crew were enrolled in the college’s electrical apprenticeship program.

The solar system was intended to be used as a teaching tool for Madison College students. However, the only previous access to the roof was to climb up a vertical ladder and up through a ship’s hatch door. That situation would obviously not be compliant with the Am with Disabilities Act requirements for instructional space. So, the college built an ADA accessible ramp and cut a hole in an exterior wall to install a new glass exit door opening onto the roof. The space surrounding the ramp and exit door has windows that look out onto a section of the solar system, so that it can serve as an observation area for tour groups even if the weather is not favorable for viewing the solar panels up close outside. An interpretive display with photos and factual signage was also installed in this area to inform students and visitors about the system.

The glass exit door shown in the previous slide opens onto the lower roof section shown in this photo. This section is designated as an outdoor classroom for students enrolled in the college’s solar photovoltaic courses. The panels shown here represent a bit less than 1% of the total system, arranged in two strings of 20 panels each. This array can be electrically disconnected, de-energized, and locked out from the rest of the solar system, so that students can then work safely on this section. The panels can be disassembled by staff, and then re-assembled by students learning safe installation, inspection, and commissioning practices. Because this array is located on a roof section having a lower elevation than the rest of the surrounding building, it is physically impossible to fall off the edge of the roof from this position. This also makes the space suitable for public outreach through tours, open house, and student recruitment events. With the installation of the grey traction walkway treads, the space can safely accommodate groups of over 100 people at a time.

The system features multiple types of roof surfaces such as the black EPDM rubber roof seen on the left, the white TPO polymer membrane roof shown in the center, and the standing seam metal roof shown on the right. Each of these roofs has different thermal characteristics, and students in the colleges renewable energy program are able to compare the output to see the effect on electric potential, instantaneous power output, and annual energy production. The system makes use of both south facing panels (shown in figure a) and east-west facing panels (shown in figure b), and students can also compare the performance of these sub-arrays to see the effect of panel orientation on electrical production and to see if the actual results from the field match theoretical model predictions.

The system includes a solar performance dashboard that provides real-time monitoring of system output as well as archiving of data for the life of the system. This information is also displayed on a flat screen kiosk located near the rooftop classroom and indoor observation area. This photo shows a week of solar production for March 2020, along with some of the financial and environmental benefits of the system.

The system uses Solar Edge DC to AC inverters and module level power electronics in the form of DC power optimizers. Each optimizer serves a pair of solar modules, andhas its own communication signal that transmits data to the inverter. The inverter then sends this data to the cloud where it is archived and can be accessed by students for analysis. Sections of the system can be selected and magnified to see output of individual strings and panels, as shown in the green box for the student instructional array. The following three slides show a quick example of the type of student learning made possible by this system.

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The upper graph on this slide shows the solar output data (in MW) on the vertical axis for a week in Nov 2020 with the date shown on the horizontal axis. The lower graph shows the temperature and humidity on those same dates. A weather event happens on the evening of Nov 5, as the humidity peaks at 100% and the temperature drops below 32F – this representing the first snowfall of the year for the past winter in Madison.

Of course, the question that we always get is “What happens to the solar output if the panels get covered with snow”…. This past year, students had the opportunity to do this experiment first hand and gather data to quantify the effect. The student array was de-energized and locked-out, and then students were able to clear and remove snow from the first of the two strings that comprise the instructional system.

This slide contains the data that students retrieved and analyzed from the solar systems data acquisition archive. For the first two days of the week, the two strings of panels shown in red and blue have essentially equal electrical production. On day three, when the two strings are both covered in snow, the power output drops to near zero. Then we see that on the last two days of the week the blue string of panels that had the snow removed greatly outperforms the red string of panels where the snow was left in place to weather naturally. Of course, this result is not surprising. But that is also not the point of this lesson. The really interestingquestion is if it would be cost effective for the school to pay a maintenance person to remove the snow from the solar panels. Students actually performed an analysis to answer this question. They determined the amount of time required for removing the snow, accounting for documentation of a work order, retrieval of a shovel and broom, dressing for the outdoors, etc. They then developed estimates for the maintenance person’s hourly wage and benefits, and determined the value of the additional electrical energy that could be produced as a result of cleaning the panels. The end result of the analysis was that it was not cost effective to pay for snow removal, and rather the snow should just be left to weather away naturally by the action of sun and wind. Of course, the faculty and staff at the college had already done this analysis and we knew the answer, but the learning opportunity for students was of great value as they explored this question for themselves and processed real-world data to reach their conclusion.

Madison College has created a 10-step guide for other colleges who might be interested in pursuing a solar roadmap for their campus. The ten steps are 1. Assemble the team and articulate purpose. 2. List and Rank Motivating Objectives. 3. Identify Stakeholders. 4. Quantify Current Energy Usage and Costs. 5. Examine Energy Management Practices. 6. Assess Sites for Solar. 7. Seek and Secure Sources of Funding . 8. Model and Prioritize Projects. 9. Disseminate the Plan. And 10. Implement Projects

A further description of each of these 10 steps is available in the manuscript published with ASEE and the Ten Step Solar Roadmap Guide. You can download these documents along with an executive summary of the Madison College solar Roadmap from the Center for Renewable Energy Advanced Technological Education. Visit www.CreateEnergy.org and go to the Publications Page. While there, you might want to sign up for the CREATE mailing list to receive our newsletter and more updates on our work with solar and renewable energy education. These resources along with the ASEE manuscript and other materials are being assembled by CREATE to share in a Solar on Schools Toolkit, which we expect to have available for download later this summer or early fall.

This work was made possible by Madison College, The Midwest Renewable Energy Association, SunVest Solar, and Madison Gas and Electric. This work was supported in part by grants from the U.S. Department of Energy and the National Science Foundation. Any Opinions, findings or conclusions are those of the authors, and do not reflect the views of the Department of Energy or the National Science Foundation. Thank you for viewing the presentation, and we hope that you enjoy the rest of the Hi-Tec conference.