Long term factors to keep in mind

As worldwide installed wind capacity increases and appears to be poised for continued growth in the U. S., it is important to remember some key issues related to continued development in the U.S. for the long term.

1. Nameplate capacity does not always equate to the same megawatt-hours per year
2. Intermittent generation sources require back-up from more dispatchable sources
3. Transmission capacity will be a large factor in adding new generation

Nameplate capacity does not always equate to the same megawatt-hours per year

Total installed wind nameplate capacity in 2006 was 9,149 MW and is expected to yield 24,800,000 MW-hrs of generation for an approximate capacity factor of 30%. The installed wind capacity in 2004 was 6,740 MW which produced 14,200,000 MW-hrs for a capacity factor of 24%. It is clear that actually generation will be dependent on regional wind conditions in any given year. Although nameplate capacity is growing at a very respectable percentage it still represents a very small portion of the grid requirements and impacts on the electrical system. U.S. generation in 2004 was 3,970,550,000 MW-hrs of which wind represented approximately 0.36 % and only about 4% of renewable generation.

U.S. Renewable Generation (MWHs) 2000 to 2004 (DOE/EIA 2006).

Intermittent generation sources require back-up from more dispatchable sources

Full nameplate capacity is only available when the wind is blowing which is often in non-peak periods. As more intermittent renewables such as wind are brought on line, they will require additional capacity from sources that can be more predictably dispatched. Currently these are usually thought of as natural gas and hydropower. In an expanding market, the cost and availability of this back-up power will impact the attractiveness of intermittent power sources. Wind does not yet bear the full burden of providing reliable power 24 hours per day. Growing capacity will highlight this cost to the system.

Transmission capacity will be a large factor in adding new generation

In Texas which as seen the largest growth in wind generating capacity, the industry has already seen transmission constraint issues limit the power that can be delivered. In the upper Midwestern states, where a majority of new wind potential exists, the system is hampered by a lack of major load centers to use the new capacity and inadequate transmission capacity to move the power to major markets. Solving the infrastructure issues will be critical to expanding utilization of intermittent generating sources such as wind.

None of these issues will limit winds growth in the immediate future. Because it represents such a small % of system capacity there is currently less focus on balancing this environmentally desirable intermittent source with system requirements. Over the long term, system capacity requirements and transmission constraints will influence the attractiveness and economics of wind capacity. As you look at the growth potential of wind and other intermittent generation, it is important to keep these long term constraints in mind.