*2.4. Solar Resources*

The datasets provided by the National Aeronautics and Space Administration (NASA) were used as the information of solar resources in the simulation [23]. Figure 4 presents the annual baseline datasets of the solar resources. Based on the datasets, 0.554 of the annual solar clearness index and 5.257 kWh/m2/d of the solar average daily radiation are presented. The definition of solar clearness index is defined as "*the ratio of the daily horizontal radiation to the extraterrestrial value*" [24].

**Figure 4.** Solar resource information of Chiang Mai University (created by the authors).

### **3. Key Parameters for the Simulation**

### *3.1. Annual Real Interest Rate*

To calculate the accurate economic results from the simulation, the annual real interest rate in Thailand should be input in the HOMER simulations [25]. Based on the official introduction of the World Bank, an annual real interest rate of 5.38% was used [26].
