HOUSING
PIH-90
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Solar Heating for Swine Buildings
Authors
Arthur J. Muehling, University of Illinois
Marvin D. Hall, University of Illinois
Richard E. Phillips, University of Missouri
Randall C. Reeder, Ohio State University
Charles K. Spillman, Kansas State University
Reviewers
Arlen Benteman, Clifton, Kansas
Harlen Murley, Aurora, Iowa
Art Paus, Fairfield, Nebraska
Larry Wilson, Moneta, Iowa
Fuel costs for heating swine buildings represent a significant—and growing—portion of the total cost of swine production. Producers are looking for alternative sources of energy to reduce these costs. Solar energy is one such energy source because it is abundant and inexhaustible. This fact sheet discusses the solar heating fundamentals and presents several systems being used to help heat swine buildings. It is not intended to be a comprehensive design manual.

Energy conservation is important especially when solar heat or any other heating system is used for swine buildings. Money must be spent to insulate a building before solar heating can be effective. Also, check the winter ventilation rate (see PIH-60, “Mechanical Ventilation of Swine Buildings”) to prevent overventilating, wasting much valuable heat. In a building insulated to the standards of PIH-65, “Insulation for Swine Housing,” solar energy can provide a large amount of the total energy required for heating.

The Amount of Solar Energy Available
The energy available on a solar collector surface depends on the time of day, the time of year, the weather, the latitude (location) of the collector site and the collector's tilt angle. In the Midwestern United States at noon on a sunny day in winter, the amount of solar energy striking a southfacing surface at a right angle is about 300 Btu/hr./sq.ft, of collector or 88 watts/sq.ft. Figure 1 shows the total amount of solar radiation available on a clear day for a south-facing surface located at 40° north latitude. The different curves represent various collector tilt angles measured from the horizontal. Fixed solar collectors receive the most energy if they face south, but deviations up to 15° from due south make little difference in total energy received. For maximum solar energy, set the tilt angle of the collector so the sun’s rays are perpendicular to the collector at solar noon.
For a fixed collector, use the average of the optimum tilt angle for each month during the heating period.

The curves in Figure 1 show that at 40° north latitude, a vertical south-facing wall receives the most energy during October through February, and considerably less the remainder of the year. A horizontal surface receives the most energy during the summer but the least during the winter. Normally, a tilt angle of the latitude plus 15°, or an angle of 55° at 40° north latitude, will give the maximum heating during the winter heating season as shown in Figure 1. A standard roof slope of 4/12 (18.4°) receives considerably less solar radiation during the normal heating season than either a vertical wall or the 55° sloped collector. The minimum tilt angle for regions with high snowfall is about 55-60° so the snow will slide off. For detailed information and monthly solar radiation data for your state, refer to Midwest Plan Service Solar Livestock Housing Handbook, MWPS-23.

Solar Economics
Will solar energy be economical for your swine building? It depends, for many things affect the economics of solar energy. Wide ranges in these factors can mean that the solar energy saved may be worth ten to twenty times as much for one pork producer as it is for another.
To reach a reasonable decision on a solar system you need to know several things:
•	How much solar energy is available in your location?
•	How many months can you use solar?
•	How much of your fuel will a solar system replace?
•	What is the cost and expected life of the solar system?
•	What percent of the available solar energy will the system collect and use?
•	What are the solar tax credits (federal and state), interest rate, operating and maintenance costs?
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex. religion, national origin, age or handicap.