Quick Answer
To calculate energy needs for solar and generator systems, consider the total daily energy consumption in watt-hours (Wh) and the available solar irradiance in kilowatt-hours per square meter (kWh/m²). Use tools like PVWatts or solar irradiance maps to estimate solar power generation. Calculate the generator's required run time and reserve capacity to cover energy shortfalls.
Calculating Total Energy Needs
The first step in designing a solar and generator system is to calculate the total energy needs of the off-grid load. This involves determining the daily energy consumption of the household or equipment in watt-hours (Wh). For example, a household with a refrigerator, lights, and a computer might have a daily energy consumption of 5 kWh. Multiply this by 365 to find the annual energy needs: 5 kWh/day * 365 days/year = 1825 kWh/year.
Designing the Solar Power System
To determine the required solar panel size, use tools like PVWatts or consult solar irradiance maps to estimate the available solar irradiance. For example, at 1000 W/m², a 5 kWh/day system would require a 1.5 kW solar panel array with a 5-6% efficient panel. To account for energy shortfalls, add a 20-30% reserve capacity to the solar panel size.
Generator Auto-Start Design
To ensure generator auto-start functionality, calculate the required run time and reserve capacity to cover energy shortfalls. For example, if the solar panel array is sized to cover 80% of the daily energy needs, the generator would need to run for 20% of the day to cover the remaining 20% of energy needs. The generator’s reserve capacity should be sized to handle short-term energy shortfalls, such as cloudy days or equipment surges. A 10-20 kW generator with an auto-start controller would be suitable for a 5 kWh/day system with a 1.5 kW solar panel array.
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