How to Calculate Electrical Energy Generated by a Photovoltaic Solar Panel

Calculating the electrical energy generated by a photovoltaic solar panel involves several key factors, including the panel’s area, efficiency, solar radiation, and performance ratio. This comprehensive guide provides step-by-step instructions, formulas, and examples to help you accurately determine the energy output of your solar panel system.

Understanding the Photovoltaic Effect

The photovoltaic effect is the process by which solar cells convert sunlight into electrical energy. When photons from the sun strike the solar cell, they excite the electrons within the semiconductor material, causing them to flow and generate an electric current.

The efficiency of a solar panel, denoted as “r” in the formula, is the ratio of the electrical power output to the solar power input. Typical solar panel efficiencies range from 15% to 22%, with higher-efficiency panels generally being more expensive.

Calculating Electrical Energy Output

The formula to calculate the electrical energy (E) generated by a photovoltaic solar panel is:

E = A × r × H × PR

Where:
– E = Energy (kWh)
– A = Total area of the solar panel (m²)
– r = Solar panel yield or efficiency (%)
– H = Annual average solar radiation on panels (kWh/m²/day)
– PR = Performance Ratio (default value = 0.75)

Example Calculation

Let’s say you have a 300-watt solar panel with an area of 2 square meters, located in an area with an annual average solar radiation of 2,000 kWh/m²/day, and a performance ratio of 0.8.

Plugging these values into the formula:
E = 2 m² × 0.15 (15% efficiency) × 2,000 kWh/m²/day × 0.8
E = 4.8 kWh/day or 1,752 kWh/year

Calculating Daily Output

To calculate the daily output in kWh, you can use the following formula:

Daily Output (kWh) = Wattage (W) × Hours of Sunlight × Efficiency

For example, if you have a 300-watt solar panel with an efficiency of 20% and it receives 5 hours of sunlight per day, the daily output would be:

Daily Output (kWh) = 300 W × 5 hours × 0.2
Daily Output (kWh) = 3 kWh

Calculating Monthly and Yearly Output

To calculate the monthly output, simply multiply the daily output by the number of days in the month.

To calculate the yearly output, multiply the daily output by 365 days.

Calculating Solar Panel Needs for Camping

To calculate the output for a solar panel used for camping, you can use the following formula:

Output = Solar panel kilowatts × Environmental factor × Solar hours per day

For example, if you have a 100-watt solar panel with an environmental factor of 80% and it receives 4 hours of sunlight per day, the output would be:

Output = 100 W × 0.8 × 4 hours
Output = 3.2 kWh

Determining Solar Panel Needs for a Location

To determine the solar panel needs for a specific location, you can use the following formula:

Solar array output = Electricity consumption / (365 × Solar hours in a day)

For example, if your yearly electricity consumption is 10,000 kWh and the location receives 4 hours of sunlight per day, the solar array output would be:

Solar array output = 10,000 kWh / (365 × 4 hours)
Solar array output = 6.85 kWh

Calculating Solar Array Size

To calculate the solar array size, you can use the following formula:

Solar array size = Solar array output × (Bill offset / Environmental factor)

For example, if you want to offset 50% of your electricity bill and the environmental factor is 80%, the solar array size would be:

Solar array size = 6.85 kWh × (0.5 / 0.8)
Solar array size = 4.28 kW

Determining the Number of Solar Panels Needed

To calculate the number of solar panels needed, you can use the following formula:

Required panels = Solar array size in kW × 1000 / Panel output in watts

For example, if the solar array size is 4.28 kW and the panel output is 300 watts, the number of solar panels needed would be:

Required panels = 4.28 kW × 1000 / 300 W
Required panels = 14.27 or approximately 15 solar panels

Calculating Load Wattage of Electrical Appliances

To calculate the load wattage of electrical appliances, you can use the following formula:

Load Wattage = Power used by each device × Number of usage hours per day

For example, if a refrigerator consumes 300 watts per hour and is used for 6 hours per day, the load wattage would be:

Load Wattage = 300 W × 6 hours
Load Wattage = 1800 Wh or 1.8 kWh

Calculating Energy Usage

To calculate the energy usage per day, you can add up the load wattage of all the appliances and divide by 1000 to convert watt-hours to kilowatt-hours.

To calculate the energy usage per month, multiply the energy usage per day by the number of days in the month.

To calculate the energy usage per year, multiply the energy usage per day by 365 days.

Calculating Cost of Going Solar vs. Solar Savings

To calculate the cost of going solar vs. solar savings, you can use the following formula:

Solar savings = (Solar panel system cost – Solar incentives) / System lifetime

For example, if the solar panel system cost is $10,000, the solar incentives are $3,000, and the system lifetime is 25 years, the solar savings would be:

Solar savings = ($10,000 – $3,000) / 25 years
Solar savings = $300 per year

Calculating Payback Period

To calculate the payback period, divide the solar panel system cost by the solar savings.

For example, if the solar panel system cost is $10,000 and the solar savings are $300 per year, the payback period would be:

Payback period = $10,000 / $300 per year
Payback period = 33.33 years

References:
– How to Calculate Solar Panel Output
– Ultimate Guide to Solar Panel Calculation
– Solar Panel Output Calculator
– How to Calculate Solar Panel Output