Civil Engineering Reference
In-Depth Information
FIGURE 1-3
Growth of electricity demand in the U.S.A. (Source: U.S. Department of Energy and Electric
Power Research Institute)
The economic size of the conventional power plant has been 500 MW to
1,000 MW capacity. These sizes could be justified in the past, as the entire
power plant of that size, once built, would be fully loaded in just a few years.
At a 2 percent growth rate, however, it could take decades before a 500 MW
plant could be fully loaded after it is commissioned in service. Utilities are
unwilling to take such long-term risks in making investment decisions. This
has created a strong need of modularity in today's power generation industry.
Both the wind and the solar photovoltaic power are highly modular. They
allow installations in stages as needed without losing the economy of size
in the first installation. The photovoltaic (pv) is even more modular than the
wind. It can be sized to any capacity, as the solar arrays are priced directly
by the peak generating capacity in watts, and indirectly by square foot. The
wind power is modular within the granularity of the turbine size. Standard
wind turbines come in different sizes ranging from tens of kW to hundreds
of kW. Prototypes of a few MW wind turbines are also tested and are being
made commercially available in Europe. For utility scale installations, stan-
dard wind turbines in the recent past have been around 300 kW, but is now
in the 500-1,000 kW range. A large plant consists of the required number
and size of wind turbines for the initially needed capacity. More towers are
added as needed in the future with no loss of economy.
For small grids, the modularity of the pv and wind systems is even more
important. Increasing demand may be more economically added in smaller
increments of the green power capacity. Expanding or building a new con-
ventional power plant in such cases may be neither economical nor free from
the market risk. Even when a small grid is linked by transmission line to
the main network, installing a wind or pv plant to serve growing demand
may be preferable to laying another transmission line. Local renewable
