Calculating the Dimensions of Your Solar Power Setup
For farmers and agricultural businesses looking to harness the power of solar energy, accurate estimation of electric usage and solar system size is crucial. Here's a 7-step process to help you determine the ideal solar electric system for your farm.
1. Collect Detailed Energy Usage Data
Gather historical electricity consumption data for your farm, focusing on total kilowatt-hours (kWh) used monthly and annually. This data can be obtained from electric bills over the past 12 months. Analyzing this data will help you understand your farm's energy usage patterns and account for future expansions.
2. Forecast Energy Demand
Because agricultural operations often have variable or seasonal loads, use predictive methods such as short-term forecasting models to estimate daily or seasonal electricity requirements more accurately. This will ensure your solar system is designed to meet your farm's energy needs throughout the year.
3. Determine Solar Insolation and Production Ratio
Find the solar production ratio for your geographic location. This is the average energy output per installed watt of solar capacity, heavily influenced by local solar irradiance and weather conditions. Production ratios vary by region—for example, the Southwest US will have a higher production ratio than the Northeast.
4. Calculate Solar System Size
Use the formula:
Then divide by the wattage per panel to determine how many solar panels you need. For example, if the farm uses 12,800 kWh annually, and your local production ratio is 1.6, and your panels are rated at 320 Watts each, the number of panels is:
5. Consider Land Use and Agro-Technical Factors
For agricultural solar (“Agri-PV”), assess land suitability not only in terms of solar irradiance and grid proximity but also agro-technical conditions like soil health, drainage, machinery accessibility, and seasonal land use patterns. This helps determine the best solar setup without compromising farming productivity.
6. Integrate Dual-Use Approaches if Suitable
Options like solar grazing (allowing livestock to graze under panels) can keep land productive and reduce maintenance, which may influence system design, spacing, and height.
7. Plan for System Operation and Maintenance
Account for cleaning needs (solar PV requires occasional cleaning) and any water usage considerations relevant to your farm’s environment, noting that solar PV uses less water than traditional thermal power generation.
In Ohio, you can expect approximately 1,100 kWh per installed kW of solar per year. The size of a solar electric system can be estimated using data about the proposed site, monthly kWh usage, and the output of a solar panel. Net metering is a billing arrangement where customers who produce their own electricity can receive a credit on their electric utility bills for any extra electricity produced.
Chart 2 illustrates the impact of different size panels on the overall footprint required for development. For instance, if 140-peak watt panels are used instead of 250-peak watt panels, the system would require 192 panels, requiring 2,035 sq. ft. of space.
Several resources are available to help with solar electric system sizing and design, such as the E3A Exploring Energy Efficiency and Alternatives Educators Toolkit, Energize Ohio: On-Farm Renewable Energy Tools, NREL PV Watts Calculator, NREL Cost of Renewable Energy Spreadsheet Tool (CREST), and the Public Utilities Commission of Ohio's Net Metering FAQ.
Remember, the steps outlined in this fact sheet provide a general estimate of the solar electric system size required to meet needs, but should not be the only source used to size a system. Conducting an energy audit can help identify strategies to reduce energy use and integrate energy efficiency practices. Many online tools and system calculators can be used to confirm projections and generate a more comprehensive system design.
- To investigate the potential for solar energy in the context of agricultural businesses, it would be advantageous to explore financing options and incentives provided by the renewable energy industry and various financial institutions.
- The conservation of resources and the reduction of environmental impacts are important factors to consider when designing a solar electric system for a farm, particularly regarding the efficient use of land and water resources, as well as minimizing disruptions to current farming operations.
- By collaborating with experts in the agriculture and solar energy sectors, it is possible to identify innovative farming practices, such as solar grazing or dual-use solar agricultural systems, that can both generate renewable energy and promote the growth of crops or livestock.
