The Open Solar Outdoors Test Field

The Open Solar Outdoors Test Field (OSOTF) is a project organized under open source principles, which is a fully grid-connected test system that continuously monitors the output of many solar photovoltaic modules and correlates their performance to a long list of highly accurate meteorological readings.

History

As the solar photovoltaic industry grows, there is an increased demand for high-quality research in solar systems design and optimization in realistic (and sometimes extreme) outdoor environments such as in Canada.[1] To answer this need, a partnership has formed the Open Solar Outdoors Test Field (OSOTF). The OSOTF was originally developed with a strong partnership between the Queen's Applied Sustainability Research Group run by Joshua M. Pearce at Queen's University (now at Michigan Tech) and the Sustainable Energy Applied Research Centre (SEARC) at St. Lawrence College headed by Adegboyega Babasola. This collaboration has grown rapidly to include multiple industry partners and the OSOTF has been redesigned to provide critical data and research for the team.

The OSOTF is a fully grid-connected test system, which continuously monitors the output of over 100 photovoltaic modules and correlates their performance to a long list of highly accurate meteorological readings. The teamwork has resulted in one of the largest systems in the world for this detailed level of analysis, and can provide valuable information on the actual performance of photovoltaic modules in real-world conditions. Unlike many other projects, the OSOTF is organized under open source principles.

All data and analysis when completed will be made freely available to the entire photovoltaic community and the general public.[2]

The first project for the OSOTF quantifies the losses due to snowfall of a solar photovoltaic system, generalizes these losses to any location with weather data and recommends best practices for system design in snowy climates.[1][3] This work was accomplished by creating a synthetic day using empirical data from the OSOTF.[4][5] This application of the OSOTF has been covered extensively in the media.[6]

Partners

This system has been made possible by the Natural Sciences and Engineering Research Council of Canada and contributions and collaborations from:

The development of this test facility is a testament to the commitment of the photovoltaic industry to continuous innovation, and the researchers hope that it will be a valuable tool for ensuring the development of a sustainable power system worldwide.[7]

Open Solar Outdoors Test Field

The SEARC Open Solar Outdoors Test Field consists of two discreet test beds, the largest of which is located on the roof of the new Wind Turbine and Trades building at St.Lawrence College and which has room for 60 commercial PV panels, which are divided between eight angles of 5.10,15,20,30,40,50 and 60 degrees. Live video for the test field is openly available online. Full data access available here.

The second test field is located on a flat rooftop at St.Lawrence College and consists of two commercial flat roof ballasted systems. Live video of this test field is also available online

In addition the Queen's Innovation Park Test Site which was developed as part of a preliminary study on the effects of snow on photovoltaic performance funded by Sustainable Energy Technologies. It consists of 16 panels mounted at angles from 0 to 70 degrees, with two each at increments of 10 degrees. By monitoring panel output, solar influx, snow fall and meteorological factors a loss due to snowfall can be determined for a general system at a variety of angles. In addition, thermal panel measurements lead to a better understanding of snow shedding mechanisms. A series of analysis algorithms have been developed which allow for constant data mining to determine factors such as snow coverage ratio using image analysis, performance ratio, and estimated losses/gains due to snowfall. A detailed description of the sensors and measurements used in the study can be seen below.

Specifications

The Open Solar Outdoors Test Field is designed to be a state-of-the-art outdoors test facility which makes this site one of the premier PV test beds in North America. The capabilities of this test bed are shown in the following table.

Measurement Device Description Accuracy
Solar Radiation-Direct CMP-22 Pyranometer The highest quality secondary standard device, calibration directly traceable to the World Radiometric Reference in Davos, Switzerland <1%
Solar Radiation-Diffuse CMP-22 Pyranometer The highest quality secondary standard device, calibration directly traceable to the World Radiometric Reference in Davos, Switzerland, fitted with an adjustable shadow band <1%
Solar Radiation-Albedo CMP-11 Pyranometer Secondary standard device, calibration directly traceable to the World Radiometric Reference in Davos, Switzerland. <2%
Wind Speed and direction RM-young wind monitor WMO standard integrated wind speed and direction sensor. +/- 3 m/s

+/- 3 °

Temperature/RH Rotronic HygroClip Integrated temperature/ RH sensor with radiation shield. RH: +/- 1.5%

Temp: +/- 0.2 C

Snow Depth SR50 ultrasonic snow depth sensor Provides accurate readings of snow on ground using calibrated ultrasonic pulses. Can give total snow depth and accumulation/settling rate. +/- 0.4%
Data Acquisition System Campbell Scientific CR1000 The industry standard for high-accuracy environmental monitoring. Expanded with multiplexers to accept 106+ point measurements +/- 0.12%
Photographs StarDot NetCam IP camera High-resolution camera, photographing array at 5-minute intervals. Photos will be used with customized image analysis software to give: Covered area, accumulation rate, sliding rate. 3 megapixel sensor
Panel Temperature Custom T-type thermocouple Monitoring of panel temperature profiles using Special Limits of Error T-type thermocouple wire. Attached to solid-state multiplexers with integrated cold-junction compensation. +/- 0.5 C
Panel Power monitoring Custom Transducers with MPPT The panels are monitored using a proprietary DC power transducer, calibrated using instrumentation traceable to NIST. This transducer measures Vmp and Imp at the regular collection intervals. The use of a 99.7% efficient MPPT device ensures that the DC maximum power point of the panel under any real world condition is known <1%
Spectral Distribution Ocean Optics USB4000 Spectrometer High quality spectrometer allows for monitoring of spectral effects within the range of PV sensitivities. This can be extremely useful when monitoring practical performance ratios and when investigating the effects of Albedo on PV performance >99.8 % corrected linearity, spectral range 200 nm-1100 nm

References
  1. Solar panels for all seasons - Canadian Geographic May 2012
  2. Joshua M. Pearce, Adegboyega Babasola, Rob Andrews, “Open Solar Photovoltaic Systems Optimization” Proceedings of the 16th Annual National Collegiate Inventors and Innovators Alliance Conference, Open 2012, pp. 1-7.open access
  3. Rob Andrews and Joshua M. Pearce, “Prediction of Energy Effects on Photovoltaic Systems due to Snowfall Events” in: 2012 38th IEEE Photovoltaic Specialists Conference (PVSC). Presented at the 2012 38th IEEE Photovoltaic Specialists Conference (PVSC), pp. 003386 –003391. Available: DOI open access
  4. Rob Andrews, Andrew Pollard, Joshua M. Pearce, “Improved parametric empirical determination of module short circuit current for modelling and optimization of solar photovoltaic systems”, Solar Energy 86, 2240-2254 (2012). DOI, open access
  5. http://www.appropedia.org/Effects_of_snow_on_photovoltaic_performance Effects of snow on photovoltaic performance
  6. Examples: Construction Canada, Renewable Energy World, Kingston Herald, Reuters, San Francisco Chronicle, Txchnologis Archived 2011-09-03 at the Wayback Machine, Toronto Star
  7. "Open Solar Outdoors Test Field - Appropedia: The sustainability wiki".
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