Assuming a total photovoltaic system efficiency of .069 [Litka et al.,
1981] the average hourly output of the photovoltaic array was estimated
at .03418 KWH/m2. By setting this expression equal to the continuous
 2
KWH demand of the pump motor and solving for m the size of the photo-
voltaic array is obtained. The peak kilowatt (KWP) output rating of the
 2 2
array is determined by dividing the size of the array (m ) by 12.5 m
This calculation is based on the photovoltaic array in operation at the
Florida Solar Energy Center [Litka et al., 1981].
 The assumptions utilized in determining the size of the photovoltaic
system imply that during a day in which the irrigation system is func-
tioning, there will be a period when the photovoltaic system's electri-
cal output must be supplemented by purchase electricity and a period of
time when the system is generating a surplus of electricity which can be
sold to the utility. In addition, if irrigation occurs at night, all of
the electricity used to power the system must be purchased. During time
periods when no irrigation is occurring, the entire output of electricity
produced by the photovoltaic system can be sold to the utility. Given
the intermittent nature of irrigation, it is expected that surplus gen-
eration sold to the utility will exceed supplemental electric purchases
during the year.

 Annual Array Generation and Irrigation Energy Demand Component

 The annual amount of electricity produced by the photovoltaic system
 2
is obtained by multiplying the annual amount of solar insolation per m
by the estimated system operating efficiency (.069). This results in an
 2
average expected system output of 118.1949 KWH/m2 annually. To obtain
total annual system output, the size of the photovoltaic system (m 2) is
 2
multiplied by this value. For example, an 800 m array (64 KWP) would
annually produce approximately 94,556 KWH of electricity.
 The amount of electricity needed for irrigation is estimated by
 first determining the total number of KWH necessary to complete one
 irrigation. This estimate is then multiplied by the number of

 number of variables from 1952 to 1974. Data pertaining to global solar
 radiation on a tilted surface were used in calculating the hourly solar
 insolation profile.