You have been commissioned to design a stand�]alone solar PV system (solar panels + battery array) for a 1000ft2 occupied between May through October, off�]line cottage located near Corpus Cristi, Texas. The PV array should supply the daily average requirement of 7.2 kWh and could be mounted on the south�]facing sloping roof at any required angle (which should be determined). Determine the required battery array sizes. State clearly all assumptions. (You can find solar data in the Solar Radiation Data Manual for Flat�]Plate and Concentrating Collectors)
To determine the required battery array size for a stand-alone solar PV system, we need to make a few assumptions and calculations. Here's the step-by-step process:
1. Determine the daily energy requirement:
The daily average requirement is given as 7.2 kWh.
2. Calculate the total energy requirement for the specified occupancy period:
Assuming 184 days (May through October), the total energy requirement would be:
Total Energy = Daily Energy Requirement * Number of Days
Total Energy = 7.2 kWh * 184 days
Total Energy = 1324.8 kWh
3. Determine the solar panel output:
We need to consider the solar radiation data in Corpus Cristi, Texas, to estimate the daily solar energy. Let's assume an average solar efficiency of 75% for the solar panels.
Using the solar radiation data, you can find the average daily solar radiation in Corpus Cristi for each month. Multiply the solar radiation value by the area of solar panels to get the daily solar energy. Considering shading, system losses, and temperature effects, a conservative estimate of 4 sun hours per day can be used.
Assuming a standard solar panel size of 1 m² and a 75% efficiency, the daily solar energy can be calculated as follows:
Daily Solar Energy (kWh) = Solar Panel Area (m²) * Solar Radiation (kWh/m²/day) * Efficiency
We will need the solar radiation data from the Solar Radiation Data Manual for Flat-Plate Collectors for Corpus Cristi to proceed with this calculation.
4. Determine the required PV array size:
Divide the total energy requirement by the daily solar energy to get the required PV array size (in m²):
Required PV Array Size (m²) = Total Energy / Daily Solar Energy
5. Determine the required battery capacity:
To determine the battery capacity, we need to consider the following factors:
- Depth of Discharge (DoD): This indicates the percentage of battery capacity that can be used before needing recharging. Let's assume a DoD of 50% to prolong battery life.
- Battery efficiency: This accounts for energy losses during battery charging and discharging. Let's assume 80% for a typical lead-acid battery.
Battery Capacity (kWh) = Total Energy / (DoD * Battery Efficiency)
By following these steps and making assumptions about solar radiation and system efficiency, you will be able to determine the required battery array sizes for the stand-alone solar PV system for the given occupied cottage.