2.3.
Constraints
47
For example, if the crop is sugar beets and the following data are established for one class of farms for 0.24 acre-ft of irrigation water per acre of
crop land
Land required: 0.09 acre/ton =
(l/yn)
Costs, inclusive of labor and land: $2.37/ton
Market price: $28.50/ton
then the net revenue from the farm before new irrigation water was available would be (omitting a charge for the land)
(1/0.24)[$28.50 - $2.37](l/0.09)
By adding more water the yield yn would be increased; hence the maximum
value of the water could be estimated, given the water versus yield relationship. If the latter were linear, Eq. (2.7) would have a linear term involving Dij t ; but if the relationship were nonlinear, then Eq. (2.7) would
be nonlinear in
Di Jt .
A second contributor to revenue from the operation of a reservoir is the
generation of hydroelectric power. The amount of electricity generated by
a hydroelectric plant associated with a reservoir depends upon the installed
capacity of the plant, the inflow of water into reservoir, the available
storage capacity in the reservoir, the level of the water in the reservoir,
and the mandatory releases to meet other downstream requirements for
water. Installed capacity may only indicate the potential or theoretical
value for power generation. It is necessary to distinguish between "dependable" or "firm" power, which is the continuous output capacity available throughout every year, and "secondary" power, which is power
available intermittently or for only portions of the year because of the
inadequacy of inflow and water-storage capacity, or because of large downstream flow requirements for irrigation, pollution control, navigation, and
so on. Therefore, it is customary for the value of electricity from a hydro
plant to be expressed in terms of two components: a value in mills per
kilowatt hour for "firm" energy and another value for "secondary" energy.
In any power system there are changes in demand for electricity over
any 24 hours. The ratio of peak demand to average demand, which is
called the system-load factor, is generally a function of the composition of
the customers in a system. For example, the larger the relative magnitude
of the electricity consumed by industrial consumers to householders the
smaller the system-load factor will be. It might seem logical to use plants
having the lowest operating costs to provide the base load, and plants
with higher operating cost to meet energy requirements at peak load.
Since operating costs of hydro plants are virtually zero, it would be ex-
Constraints
47
For example, if the crop is sugar beets and the following data are established for one class of farms for 0.24 acre-ft of irrigation water per acre of
crop land
Land required: 0.09 acre/ton =
(l/yn)
Costs, inclusive of labor and land: $2.37/ton
Market price: $28.50/ton
then the net revenue from the farm before new irrigation water was available would be (omitting a charge for the land)
(1/0.24)[$28.50 - $2.37](l/0.09)
By adding more water the yield yn would be increased; hence the maximum
value of the water could be estimated, given the water versus yield relationship. If the latter were linear, Eq. (2.7) would have a linear term involving Dij t ; but if the relationship were nonlinear, then Eq. (2.7) would
be nonlinear in
Di Jt .
A second contributor to revenue from the operation of a reservoir is the
generation of hydroelectric power. The amount of electricity generated by
a hydroelectric plant associated with a reservoir depends upon the installed
capacity of the plant, the inflow of water into reservoir, the available
storage capacity in the reservoir, the level of the water in the reservoir,
and the mandatory releases to meet other downstream requirements for
water. Installed capacity may only indicate the potential or theoretical
value for power generation. It is necessary to distinguish between "dependable" or "firm" power, which is the continuous output capacity available throughout every year, and "secondary" power, which is power
available intermittently or for only portions of the year because of the
inadequacy of inflow and water-storage capacity, or because of large downstream flow requirements for irrigation, pollution control, navigation, and
so on. Therefore, it is customary for the value of electricity from a hydro
plant to be expressed in terms of two components: a value in mills per
kilowatt hour for "firm" energy and another value for "secondary" energy.
In any power system there are changes in demand for electricity over
any 24 hours. The ratio of peak demand to average demand, which is
called the system-load factor, is generally a function of the composition of
the customers in a system. For example, the larger the relative magnitude
of the electricity consumed by industrial consumers to householders the
smaller the system-load factor will be. It might seem logical to use plants
having the lowest operating costs to provide the base load, and plants
with higher operating cost to meet energy requirements at peak load.
Since operating costs of hydro plants are virtually zero, it would be ex-