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Dispatchability

Dispatchability graphic.pngFor sustainable high penetration of solar power into the grid, it is imperative that solar power is available: (a) on-demand, (b) when and where it is needed, (c) in the desired amounts and (d) in a manner that is comparable to or better than conventional power plants.

The Dispatchability activity area aims to ensure that solar power plants based on PV and CSP technologies at utility and distributed scales are capable of being dispatched in a fashion that is comparable to or better than conventional power plants. SunShot addresses the issue of dispatchability with a two-pronged approach: (a) extensive analyses to understand the impact of high penetration of solar power plants on the bulk power system and distribution system operations, and (b) research on understanding and enhancing the dispatch capability of PV solar power plants, and investigating the value of varying energy storage capabilities for CSP plants. SunShot also supports the development of standardized methods for testing grid performance of PV solar power plants, and exploring and demonstrating the value of energy storage.

CHALLENGES

Under high penetration of solar power, the constrained availability of solar energy only during the daytime and its associated intermittency and variability, results in steep ramps of other types of generation using fuels such as natural gas, hydro, coal and possibly even nuclear, in order to match the total generation profile to the load profile. These ramp requirements from conventional generation are atypical and can be potentially difficult and expensive to accommodate in order to incorporate high solar penetration. Further, challenges arise for the system operator to properly determine the appropriate levels of dispatch for all conventional generation; since solar irradiance and power output must be predicted and cannot be planned with certainty in advance, there is inherent uncertainty in the magnitude and timing of the ramps required due to high solar penetration.

A further impact of high solar penetration is in the capacity value of solar. To enable increasing penetration of solar power on the grid in a manner that is efficient, cost-effective and minimizes curtailment of solar energy, it is critical that solar-generated power is available at any time during the day or night.

Dispatchability Challenges of High Penetration of Solar
  • Grid Operations – quantifying impact of dispatchability of solar on cycling and ramping of conventional generation, transmission utilization patterns and generation curtailment
  • Grid Reliability – determining impact on operating reserves, generation flexibility and grid codes compliance
  • Solar Power Plant Controls – determining optimal levels of controls at the local, regional and global scales
  • Solar Power Optimization – choosing optimization parameters for efficient dispatch such as timescale, ramp rates, grid characteristics, and determining their impact and value for regulators and adjacent power grids 

POTENTIAL SOLUTIONS

Dispatchability graphic2.pngSunShot’s mission is to be a catalyst to enable dispatchability in solar power plants in order to accommodate and interconnect ANY level of high penetration of solar generation in the grid. Potential pathways for handling high solar penetration include forecasting, supply shifting (energy storage), load shifting and additional load, among others, to ensure that solar power is not curtailed due to its lack of dispatchability. As solar penetration and generation on the grid increases eventually well into the envisioned hundreds of GW of interconnected capacity, all of the approaches must be considered in concert and implemented at varying scale, for reliable and cost-effective integration into the grid.

METRICS

Achieving SunShot’s Dispatchability target metrics will result in a significant and disruptive improvement in the integration of solar power plants into the grid, supporting more efficient and cost-effective operation of the power system, and helping maintain grid reliability while increasing the proportion of cleaner, renewable generation.

SunShot Technical Metrics for Dispatchability of Solar Power Plants
  • Reduce integration cost of solar plants (both PV and CSP) 
    • Integration cost < $1/MWh
  • Exceed current and future grid performance standards 
    • > NERC standard
  • Accurately predict power production from solar plants 
    • < 3% variation from forecasted power generation from solar plants, at all timescales
  • Achieve dispatchability of solar plants that meet or exceed utilities/ISO dispatch rules  for conventional generation, while maintaining SunShot levelized cost of electricity (LCOE) target
    • > Utilities/ISO dispatch rules
    • LCOE < 6 ¢/kWh at the utility scale, without subsidy, by the year 2020

PROJECTS