电力需求与定价(18)

these costs are usually small and their allocation will not

greatly affect the results.

E. Analysis of Hydroelectric Generation [31], 15.51

Next, we .briefly mention several specific issues which arise

in the analysis of hydro systems, and when seasonal variations

in LRMC are important. Generally, in an all hydro system the

LRMC of generating capacity would be based on the cost of

increasing peaking capability (i.e., additional turbines, penstocks,

expansion of powerhouse etc.), while incremental energy

costs would be the costs of expanding reservoir storage.

When there is significant spilling of water (e.g., during the wet

season), incremental energy costs would be very small (e.g.,

O&M costs only), and at times when demand does not press

on capacity, incremental capacity costs may be ignored. However,

if the system is likely to be energy constrained and all

incremental capacity is needed primarily to generate more

energy because the energy shortage precedes the capacity constraint

for many years in the future, then the distinction between

peak and off-peak costs, and between capacity and

energy costs, tends to blur. In an extreme case, because hydro

energy consumed during any period (except when spilling)

usually leads to an equivalent drawdown of the reservoirs, it

may be sufficient only to levy a simple kilowatt-hour charge at

all times, e.g., by applying the AIC method to total incremental

system costs.

In a mixed hydro-thermal system, an important general

guideline is that if the hydro is used to displace thermal plant,

during a rating period then the running cost of the latter is the

relevant incremental energy costs. If pumped storage is involved,

the marginal energy costs or value of water used would

be the cost of pumping net of appropriate losses. Also, if the

pattern of operation is likely to change rapidly in the future

(e.g., shift from gas turbines to peaking hydro as the marginal

peaking plant, or vice versa), then the value of the LRMC

would have to be calculated as a weighted average, with the

weights depending on the share of future generation by the

different types of plant used.

IV. ADJUSTINGST RICTL RMC

Once strict LRMC has been calculated, the first stage of

tariff setting is complete. In the second stage, the actual tariff

structure which meets economic second best, social, financial,

political and other constraints must be derived by modifying

strict LRMC, and this topic is dealt with below. This process

of adjusting LRMC will, in general, result in deviations in both

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