Girasol, a sky imaging and global solar irradiance dataset

The energy available in Micro Grid (MG) that is powered by solar energy is tightly related to the weather conditions in the moment of generation. Very short-term forecast of solar irradiance provides the MG with the capability of automatically controlling the dispatch of energy. We propose to achieve this using a data acquisition systems (DAQ) that simultaneously records sky imaging and Global Solar Irradiance (GSI) measurements, with the objective of extracting features from clouds and use them to forecast the power produced by a Photovoltaic (PV) system. The DAQ system is nicknamed as the Girasol Machine (Girasol means Sunflower in Spanish). The sky imaging system consists of a longwave infrared (IR) camera and a visible (VI) light camera with a fisheye lens attached to it. The cameras are installed inside a weatherproof enclosure that it is mounted on an outdoor tracker. The tracker updates its pan an tilt every second using a solar position algorithm to maintain the Sun in the center of the IR and VI images. A pyranometer is situated on a horizontal support next to the DAQ system to measure GSI. The dataset, composed of IR images, VI images, GSI measurements, and the Sun's positions, has been tagged with timestamps.

Methods
We built a system composed of VI and IR solar radiation cameras, a tracking system, anda pyranometer, to collect the data. A weatherproof enclosure contains the two USB cameras,and it is mounted on top of two servomotors. The cameras are connected to a motherboard thatruns a solar tracking algorithm. This motherboard is placed inside of a different weatherproofenclosure together with a router, a servomotor control unit, a data storage system, plus theirrespective power supplies. The enclosure’s degree of protection is IP66. This is an internationalstandard utilized for electronic equipment that provides protection against dust and water.

The tracking system and DAQ software is currently operative. The software was programmed in Python 2. The system is placed on the top roof area of the Mechanical Engineer-ing building at UNM central campus (35.0821,−106.6259). The DAQ sessions can be visuallymonitored through a webpage. All devices were interconnected via a LAN network built by DHCP server.