Accommodating High Levels of Variable Generation - NERC

Introduction
1. Introduction
Fossil-fired generation produced nearly 70% of the total electrical energy in the United States in
2006, with nuclear producing 19% and existing renewable generation approximately 8%. 1
Natural gas-fired generation produced 21% of the electrical energy while representing 41% of
the installed summer generating capacity. Coal-fired generation produced 49% of the electrical
energy in North America and represented 32% of the installed summer capacity. Heavy and
light oil is primarily used as a back-up fuel for natural gas. Oil-fired capacity is negligible and
total oil generation comprised less than 2% of the electrical energy produced in 2006. 2 Fossil
fuels are non-renewable: that is, they draw on finite resources. In addition, they contribute to
the production of greenhouse gases and particulates. In contrast, renewable energy resources,
such as wind, solar, ocean, biomass, hydro, etc., can be replenished at a generally predictable rate
and have no direct greenhouse gas or particulate emissions.
Government policy has been the key driver for renewable energy expansion in the US and
Canada. For example, over 50% of (non-hydro) renewable capacity additions in the US from the
late 1990s through 2007 have occurred in states and provinces with mandatory Renewable
Portfolio Standards (RPS) 3 or equivalent policies (see Figure 1.1 4 ). Other significant motivators
include federal, provincial
and state tax incentives,
renewable energy
investment funds,
economic
competitiveness,
voluntary green power
markets, public support,
and hedging against fuel
price increases and carbon
regulation. Figure 1.1,
shows a province-byprovince
and state-by-state
breakdown of North
Figure 1.1: Snapshot of North American Climate
Initiatives
1 http://www.eia.doe.gov/emeu/aer/pdf/aer.pdf
2 http://www.eia.doe.gov/cneaf/electricity/epa/epat1p1.html
3 http://www.pewclimate.org/what_s_being_done/in_the_states/rps.cfm or more detailed resource maps at:
http://www.pewclimate.org/what_s_being_done/in_the_states/nrel_renewables_maps.cfm
4 The Florida Public Service Commission (FPSC) Renewable Portfolio Standard is currently under development
Accommodating High Levels of Variable Generation 1