Irradiance Modeling Variance on Vertical Plane of Array Surfaces
Open Access
- Author:
- Burger, Scott William
- Area of Honors:
- Energy Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Jeffrey Brownson, Thesis Supervisor
Dr. Sarma V Pisupati, Thesis Honors Advisor - Keywords:
- Plane of Array
Passive Systems
Irradiance
t-test
Residuals
EEB Hub
Building 101
NOAA
TRNSYS - Abstract:
- Significant radiative transfer occurs outside of buildings, yet energy control systems are typically signaled by internal air temperature thermostats. As façades essentially behave as flat plate solar thermal collectors, windows permit rooms to behave as cavity collectors. It is believed that buildings may perform at higher economic efficiency with external signals. An analysis of measured irradiance for plane of array (POA) vertical surfaces was compared to modeled irradiance data (TRNSYS) to evaluate residuals. The measured POA irradiance data integrates all irradiance components for a given orientation, collected on minute intervals for half of the year between the months of July and December. The data were available for the East, West, and North surfaces of the Energy Efficient Buildings Hub's Building 101 in the Philadelphia Navy Yard. Modeled data was generated from global horizontal irradiance from a meteorological station in Avondale, Pennsylvania, located thirty three miles from the Philadelphia Navy Yard. Comparative analyses between irradiance data averaged over each hour and irradiance collected from Avondale, PA resulted in occasional residuals on the order of hundreds of watts per meter squared. To evaluate if the residuals between the measured and modeled data were considered statistically different, a t-test was employed to compare each B101 sensors' average irradiances with Avondale's average irradiances for each month from July to December. The results of the t-tests proved with 95% confidence that between the months of August and December for the North and East walls and during the month of July for the West wall, the measured irradiance values were statistically different from the modeled irradiance values due mostly to surrounding objects. As a result, the modeled data cannot represent the measured data during those months. Use of local sensors that report actual shading conditions upon a building are actually more useful in this case, as a shaded region will lead to reduced energy gains for entire zones of the building, and require control response to maintain a comfortable indoor environment. Solar irradiance varies significantly on a building's many surfaces based on the environment and surrounding objects. This case study shows how local plane of array irradiance data can be informative to a building control system.