Abstract
Current industry methods for estimating energy savings resultant from energy conservation measures such as lighting, HVAC, and solar Photovoltaic (PV) projects at California K-12 schools include various software systems. The current calculation methods being examined are the following: lighting calculations are completed through an Excel spreadsheet, solar PV generation and system sizing is calculated using Helioscope, and HVAC energy savings is calculated using the California Energy Commission (CEC) developed Excel based calculator. The energy savings from each calculation source are manually combined to assess total energy savings. Although each energy conservation measures calculation tool was assessed, the CEC HVAC calculator is a focus of this report as it is required to use when an HVAC project is funded by the State, which is very common for K-12 HVAC projects. Upon closer examination it was found that the CEC calculator does not consider weather and temperature trends of the project location, causing estimated energy savings to be underestimated when compared to measured. To increase the accuracy and efficiency of calculating estimated savings while maintaining simplicity, an alternate simplified method was developed in MATLAB specifically for heat pump HVAC systems to allow for streamlined preliminary energy savings calculations of a common K-12 HVAC equipment type. Several K-12 projects completed by a U.S. energy services company were selected as case studies to assess the accuracy of the MATLAB tool by comparing estimated savings to actual measured savings. As lighting is not dependent on geographical location, HVAC heat pumps and solar PV were assessed by climate zone using temperature and weather data specific to the location of interest. Solar PV and HVAC energy savings results from the MATLAB tool showed to be accurate and comparable to measured savings and followed geographical patterns. For the three HVAC California K-12 heat pump projects selected, the measured savings were on average 46% higher than what the CEC calculator estimated while the MATLAB tool estimated savings were on average 5% different than measured. The solar PV project results compared to the MATLAB tool results resulted in an average 2% variance. Overall K-12 energy savings potential for energy conservation measures were shown to highest in Northern, Eastern, and Southern California where ambient temperatures are more extreme and availability of global horizontal irradiance is also significant.