Solar Electric for Poultry Houses
Spencer Pope owns and operates Spencer Pope Farms, Inc., a six-house broiler operation in Carthage, Mississippi. Pope was interested in integrating solar energy production to diversify his farm, use the available roof space on his poultry houses, maintain cash flow when empty and offset some of his electricity costs.
Flush mount installation on a 40' X 500' clear-span poultry house with a 5/12 pitch roof facing due south at Spencer Pope Farm. Photo by Will Hegman.
The 5/12 pitch roof angle of the poultry houses provides a 22.5 degree array tilt (latitude is equal to tilt angle). This is 10.5 degrees off-latitude in Carthage Mississippi, which is at about 32 degrees. Production can be maximized by increasing the tilt angle in winter and decreasing the tilt angle in summer. Pope decided to flush mount the system to decrease maintenance, lower costs and avoid wind load. This flush mount loses 8-9 percent efficiency during winter months – a small loss in comparison to the other benefits. Fortunately, the east-west (end to end) orientation that is commonly used in poultry houses in the Southeast provides a 180-degree azimuth (due south), which is about optimal in this case. Shading at this particular site was not an issue.
The estimated weight of the photovoltaic system is around 2.5 pounds per square foot dead load. This weight is almost equally distributed across a surface area of 682 square feet. The speed rail racking used on this system is mounted perpendicular to the trusses and secured with 3.5-inch lag bolts. This adds some structural integrity to this modern poultry house. This poultry house, like many other clear-span houses, is constructed for a live load of 31 pounds per foot.
System Specifications and Performance
- DC rating: 8.4 kW (175 DC watts per module)
- Modules: 48 Solarworld SW-175 modules / year
- Inverters: 48 Enphase M175-240240-S01 AC microinverters
- Mounting system: Hollaender Speed Rail lagged into trusses at 5-foot intervals
- Estimated Energy Production: 10,848 kWh AC / year (from PVWatts)
In older houses, the load and structural considerations should be seriously considered. While most poultry houses are expected to last anywhere from 25 to 30 years, a PV system's estimated life of 30 years may outlast the poultry house. "Also, talk with your farm insurance underwriter about increasing your insurance premium before installation," said Pope. A qualified solar contractor should be familiar with these considerations.
The grid-tied system takes advantage of the Tennessee Valley Authority's Green Power Generation Partners® program. "TVA purchases all the energy we can produce for the next 10 years at 12 cents a kilowatt hour (kWh) above the retail rate", said Pope. Because the retail rate is 10 cents a kWh, TVA pays Pope 22 cents (10 cents plus a 12 cent guaranteed premium) for each kWh produced. However, Generation Partners is not available in all areas and Mississippi does not have a net metering law requiring interconnection. This means that many farmers in Mississippi may not have the opportunity to sell or receive a credit for the renewable electricity they generate. To see if you have a net metering law or incentive for installing renewable energy, visit www.dsireusa.org.
Solarworld SW-175 modules on top of a 12-year-old poultry house. The system is eligible for depreciation as farm equipment under MACRS. Photo by Will Hegman.
The Rural Energy for America Program (REAP) provides competitive grants of up to 25 percent of eligible project costs. Key eligibility criteria include being a rural farm or small business and having project costs that meet the minimum grant amount of $2,500. This project received just under $20,000 from the REAP program. This project also took advantage of the 30 percent federal renewable energy tax credit and the solar equipment was depreciated as farm equipment using the Modified Accelerated Cost Recovery System (MACRS) in the IRS tax code.
The system has encountered a few minor interruptions that were quickly diagnosed through online system monitoring. "Weather variability has been the greatest factor affecting system performance and production", said Pope. The system was designed, installed and interconnection agreements were negotiated by Will Hegman who owns and operates Mississippi Solar.
To monitor this system's performance online visit www.schoolsonsolar.com and click on "Energy Production" and select "Poultry Farm".
System Costs and Incentives and not System Specifications and Performance
- Total system cost: $79,632 ($9.48 per watt)
- REAP grant: $19,908
- Federal tax credit: $17,917
- Generation Partners: $1,000 upfront incentive; retail electricity rate plus $0.12 / kWh for 10 years
- Estimated cost after all incentives: $16,941*
For the contact information of Mississippi Solar, visit ATTRA's Directory of Energy Alternatives, a nationwide directory of alternative energy installers and consultants.
Solar Electric for Poultry Houses
By Leif Kindberg, ATTRA Farm Energy Specialist, December 2009
This page was last updated on: June 13, 2016