To analyze the effects of these factors on the economic feasibility of
photovoltaic systems several scenarios describing future economic condi-
tions are simulated.
 The scenarios differ in the degree to which future economic events
are conductive to establishing the economic feasibility of photovoltaic
powered irrigation systems. Thus, the optimistic scenario assumes a
rapid decline in the cost of photovoltaic arrays and a rapid rise in
conventional fuel prices. Conversely, the pessimistic scenario tsPumes a
very slow decline in array cost and no real increase in conventional
fuel prices. The base scenario assumes a moderate decline in array cost
and a moderate increase in fuel prices. For all scenarios, the ratio of
the price utilities pay for electricity relative to the prices at which
they sell electricity ("buyback" ratio) is varied over a range of values.

 BASIC CONCEPTS AND ASSUMPTIONS

 Any irrigation system is composed of two basic components. The
water dispersal system structure (e.g., pipes, sprinklers, support
structures) and a pump-power unit. A variety of energy sources can be
used to drive the pump-power unit. The two most common types of energy
used in Florida are diesel fuel and electricity [Stanley et al, 1980].
From a technical standpoint, the type of energy used to drive the pump-
power unit is, in most cases, independent of the type of system structure.
Thus, for example, a permanent overhead system can be powered by an
electric motor or a diesel engine [Stanley et al., 1980].
 Given this independence between pump-power units and the corres-
ponding energy source, and water dispersal system structure, an assess-
ment of the economic feasibility of utilizing photovoltaic arrays to
power irrigation systems is fairly straightforward. If the discounted
cost of currently used conventional alternatives over the useful life
of the photovoltaic system, economic feasibility can be established.3


Regulation Commission (FERC) regulations, electric utilities are required
to purchase surplus electricity from dispersed producers.
 3The discussion here, and that which follows, assumes that irrigation
as a cultivation practice is economically justified. Give this assumption