The operations and planning rules for integrating variable resources aren’t the same across the electric power industry in the United States at present. Opinions are somewhat divided about what...
Shaping system transformation.
provide reliability support has long been in the operator’s toolbox, but usually as utility-controlled unscheduled or emergency load shedding. The potential for distribution smart grid concepts to provide grid reliability benefits in a less intrusive—and presumably less expensive—manner, implies that it could complement as well as compete with other methods for providing reliability services— i.e., load following, frequency management, etc.
One example is the use of customer storage for providing grid regulation services. Perhaps the most intriguing prospect for use of customer storage for grid support is associated with deployment of plug-in hybrid electric vehicles (PHEV) and electric vehicles (EV). While vehicle to grid (V2G) services have been suggested and analyzed 2 for providing grid services, concerns over voiding vehicle warrantees—due to deep discharge—suggests caution with this approach. An alternative version, V2G½, allows the utility to vary charging to provide grid regulation service. 3 Analysis of this approach suggests that significant regulation service could be provided even when confined to the charging cycle for PHEVs and EVs. 4 As with some grid support options, such as frequency support, the location of the asset isn’t a vital attribute; what is vital is that it’s available, dispatchable, and reliable. Smart grid assets can provide both local and wide-area grid support, if institutionally enabled.
The use of smart grid as a means of providing regional or even extra-regional reliability services will require means of incenting and rewarding such use. To the degree this can be accommodated within existing markets and regional and extra-regional agreements, no further institutional or regulatory action is needed. However, it’s more likely that the institutional underpinning for wide-area utilization of smart grid assets hasn’t yet reached a state that it would enable such utilization.
Deployment of renewable generation is growing rapidly, in part as a response to financial opportunities to receive state renewable energy credits (legislated by renewable portfolio standards) and federal production tax credits. Over 63 percent of the total electric generation additions in 2009 were wind power. 5 While wind power additions were lower in 2010 (estimated to be about 40 percent of new generation), wind and growing solar electric generation will continue to be a significant source of new generation additions, at least as long as state and federal subsidies encourage development. The prospect of continued low natural gas prices entices development of gas-fired generation, but if concerns over greenhouse gas emissions remain strong, our future will include substantial amounts of new renewable generation.
One major challenge with variable renewable generation—namely wind and solar—is its stochastic nature, and potential for sudden ramps, both up and down. Wind ramp rates exceeding 100 MW per minute have been observed at the control area level, even at the relatively modest levels of wind power penetration today. Such variability causes significant challenges for grid operators, as they seek to balance electricity generation to meet load.
Grid operators are developing improved tools to manage this higher level of generation uncertainty, using improved forecasting, better understanding of the probabilities of high ramp rates (and associated reserve requirements), and increasing the use