Equipment & Purchasing

Each of the six arrays totals approximately 10 square meters in size and is expected to produce about 1 kW of direct current electricity. All electricity is sent back to the grid but only offsets a tiny fraction of the schools’ usage. The systems can be scaled up at any time to make a larger impact on school energy load; however, at present the scope of the Sun Power for Schools program is educational in nature. The installations size and output lend themselves well to math calculations and give the students a tangible connection to potential for solar energy.

All components for the Sun Power for Schools solar electric systems were purchased complete as a kit from Sunwize Technologies, which maintains distribution facilities in New York and California. Each kit included: seven Sharp NE-165U1 165 W modules, a Sunny Boy model SWR i1800U inverter and AC disconnect, DC disconnect, Power-fab top-of-pole mount, as well as all the cables and electrical wiring for the panels themselves. Tracking systems were not purchased as part of the kit because of the added expense and maintenance associated with these devices. Pole mounts were chosen for five of six schools for ease of installation, flexibility in PV site location, lower cost and avoiding problems typical of building mounts such as potential roof leaks and structural issues. The pole-mounted arrays can be adjusted if necessary or desired. While system kits came with seven panels, the pole-mount racks were built for eight. Marketing signs were crafted to fill this visual gap. The exception was Sandy Creek High who wanted the PV array located in a courtyard that is part of their outdoor classroom. It was not possible to get all necessary equipment into this space for pole-mount installation, so wall-mount was employed instead.

With installation costs, Green Power EMC spent just under $11,000 at each of the 6 schools. After pricing several other systems and components, the decision was made to purchase Sunwize kits. Their decision took several factors into account, including time and effort required to coordinate buying parts separately, employ custom fabrication and troubleshoot installations. Using the kits ensured a common denominator at the schools and simplified the procurement of individual parts and pieces. The latter was important given the continued difficulty obtaining PV technology in the United States. Consumer demand for PV remains by and large in international markets, and delays are common. In the case of Green Power EMC, the initial purchase order for equipment was put out in May but the first shipment did not arrive until August, rendering any installations before the start of the school year (as had been hoped) impossible.

To some extent the shipping delays helped compensate for the local coops indecisiveness picking school partners; however it also made coordinating the installation so that the installers, local coops and school officials could all be present difficult. Ideally, all details, arrangements and agreements would be worked out before the end of the school year so that systems could be installed during the summer and ready to start in the fall. However, only a few delays can prevent this from happening. To curb delays in the future, equipment should be ordered well in advance and specific target dates for installations set (as well as several back up dates in the event of rain). This should accommodate long wait times needed to acquire all of the system components and help mitigate scheduling conflicts for the parties involved.

Once solar electric systems were installed, the next step was to get all of the systems online and data uploaded. Data acquisition systems (DAS) were purchased from Fat Spaniel, a California-based company. The school districts of participating high schools were responsible for providing Internet connection at the site of the installation. Difficulty with the DAS, due to school IT security issues, presented one of the greatest challenges during installations in phase one.

The Fat Spaniel data logging system uses sensors, wiring and signal conditioning devices to monitor the performance of the solar electric system via computers and the Internet where the information is recorded and displayed. The sensors are polled every minute. The data is then averaged and integrated every fifteen minutes and stored internally. Using an online interface, Fat Spaniel allows students to monitor the vital stats of their PV system, as well as other school PV systems across the nation and worldwide. The collected information displays the amount of electricity generated daily, weekly, monthly, yearly and over the lifetime of the system. Students and teachers can also delve further into the DAS, downloading an Excel workbook of data recordings taken in fifteen-minute intervals.

The geographic range and number of schools on the Fat Spaniel site ensured Sun Power for Schools affiliates access to a large, and more importantly, normalized dataset that students could use to analyze the variables affecting power production, including: AC and DC output, irradiation levels, and ambient and cell temperature. Access to data from a range of schools also makes glitches in the DAS system of a Sun Power for Schools member school less detrimental than it would be if a classroom was relying on their data alone. This is particularly important in the early phases of the program when teachers are becoming familiar with the new resource. For example, Greystone EMC had to bore under the street to bring in a fiber optics cable for the data acquisition system at Hiram High School. By April 2006, the school’s PV system was still not sending data. Additionally, Heritage High School had intermittent sensor problems. Incomplete or non-existent data sets for their system’s power output would alter how a teacher must present a lesson, but does not prevent a teacher from carrying out that lesson plan. These issues have been resolved, and data is coming in from all six schools.