YouSolar has developed its own historical and real-time solar irradiance data service, SPOT™, that has global coverage and includes terrain shading. SPOT™ accesses historical and real-time meteorological and terrain data from international satellites to create a location-specific historical data set and real-time forecast. This data is used to configure the PowerBloc™ nano-grid during the sales process and in a 24-hour forecast which is sent hourly to each PowerBloc™ to be used by its Energy Management System. The irradiance data is calculated for the plane of the solar array and converted to solar energy production by PowerBloc™’s EDISON™ energy management system and used in daily and day-ahead operations.
We tested SPOT™ at a YouSolar PowerBloc™ installation on the coast of Big Sur, California, which has tall cliffs and sees rapid weather changes. We have compared SPOT™ and EDISON™ production “backcasting” for 2018 and compared it to the actual output of the solar system of a house within 100 meters from our project. SPOT™ was “spot on” with its monthly solar production profile which is greatly influenced by winter weather. At Big Sur the ratio of solar energy in the summer to the winter is large, 3 x.
On 1 September 2019, we tested the accuracy of SPOT™’s terrain shading calculations. Sunrise was at 6:41 AM, but the cliffs at the location block the sun for a few hours. SPOT™ predicted that the sun would hit the solar array at 9:24 AM. The array was fully illuminated at 9:28 AM. This small error is due to the uncertainty of the actual cliff-shape from the available 10-meter elevation satellite data. An error in the terrain-sky boundary elevation angle of 2.5° equates to about a 10 minutes in timing error.
But not to worry, over time EDISON™ will determine the exact terrain-sky boundary from the production of the solar array and get the timing down to the minute.
Cliffs above a YouSolar project on the Big Sur Coast block the sun in the morning. On 7 July 2019 the cliffs block the sun for 2+ hours.