ABSTRACT
The intermittency in output from a VLS-PV plant renders its matching to the requirements of a conventional electricity grid an issue of quite complex proportions. In the first place, the grid has its own intermittency problems, associated with customer requirements. These problems are handled via a combination of economic considerations and the controlled input from three basic kinds of power plant. Base-load plants (typically coal-fired or nuclear) have limited ramping capabilities. They operate on a continuous basis for extended periods of time (days or weeks) with relatively infrequent shut-downs for maintenance. Intermediate-load plants (typically gas-fired or oil-fired) have improved ramping capabilities. They can be started up in the early morning and shut down in the evening. Peak-load plants (typically fast-reacting gas turbines) are capable of ramping from zero to full power in typically 10 minutes and can undergo smaller ramping steps with extreme rapidity. They are used to follow the moment-to-moment requirements of the grid. Each of these plant types has its own economic considerations based on: fuel cost, frequency of maintenance, age of plant, cost of replacement, and moment-to-moment selling price of the electricity.
