A Utility Perspective of Wind Energy - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 730

station in the Altamont Pass and a projected station in Solano County [Smith and Ilyin 1991].
During the summer the PG&E load usually peaks at 1600 Pacific Daylight Time.
Figure 13-4 illustrates the results of this study for 1987 and 1988. The rising wind speed
in the morning in Solano County usually occurs about two hours in advance of that in the
Altamont Pass. As a result, the average wind speed at this site during the peak load hour
equaled or exceeded the rated wind speed during four of the five years studied. The average
wind speeds at the Altamont site during the peak hour, however, were usually only between
cut-in (the lowest speed in the operating range) and half of the rated speed. Thus, a signifi-
cantly higher LCC is indicated for the projected Solano County wind power plant.
Figure 13-4. Typical hourly output data required for calculating the load carrying capa-
bility (LCC) of a wind power plant, with the peak load time of the utility system noted.
Hourly data are averages over one year. Altamont Pass site data are measured and Solano
County site data are projected. [Smith and Ilyin 1991]
To obtain a more-accurate LCC, the output at all hours of the year needs to be exam-
ined and compared to the system load, hour by hour. Another factor that is needed for the
determination of the LCC of a power source is its relative loss of load probability , or LOLP.
The LOLP is the chance that the utility cannot meet its load demand, because of unexpect-
edly high loads, equipment failures, or other reasons that the necessary plant capacity would
not be available. An LOLP needs to be computed for each hour of the year using Garver's
formula [Garver 1966]. The projected hourly outputs of a power source are then multi-
plied by their associated LOLPs before calculating the LCC of the source. An LCC of about
80 percent of the rated power times the projected on-line availability was calculated for the
Solano County site in this study. This relatively high value is the result of the excellent fit of
the Solano wind resource to the PG&E load cycle.
Indirect Value
Wind energy has additional indirect value to the utility and the community. These
benefits are typically not counted in a utilities generation planning models or in the regional