This is an excerpt from the Second Quarter 2011 edition of the Wind Program R&D Newsletter.

On March 16, 2011, DOE's National Renewable Energy Laboratory hosted a kick-off meeting for Phase 2 of the Western Wind and Solar Integration Study (WWSIS). The first phase of WWSIS identified the operating impacts of penetration levels at up to 35% of wind and solar energy on the power system operated by the WestConnect group of utilities in Arizona, Colorado, Nevada, New Mexico, and Wyoming. The study found that it is feasible for WestConnect to accommodate 30% wind and 5% solar if significant changes to operating practices were made, including balancing area cooperation and intra-hour scheduling.

Western Electric Coordinating Council regulators, utilities and state policymakers would now like to gain a better understanding of the wear and tear and increased maintenance/repair costs due to increased ramping and cycling of conventional coal and gas generators. They would like to know when it makes sense to upgrade a conventional generator to better accommodate wind and solar and the potential mitigation options to reduce overall costs by reducing the cycling and ramping of conventional generators.

In Phase 2 of WWSIS, researchers will use a new modeling tool, PLEXOS, to examine the impact of variable generation on conventional units. Traditional production cost modeling uses hourly time steps; however, many of the effects of renewable generation are apparent at the sub-hourly level. PLEXOS models a 5-minute dispatch and can easily optimize multiple constraints, including additional costs due to ramping and cycling of conventional generators. It is used by industry analysts and power companies to resolve regional reserve allocations, resource expansions, emission values, and market prices for energy and reserves. It offers more detailed modeling of conventional generator emissions that result from ramping events and allows analysts to examine the benefits of faster markets, balancing area cooperation, and shorter time horizon forecasting techniques.

The objectives of WWSIS Phase 2 include:

  1. Obtain better data for wear and tear costs of conventional generators during cycling and ramping
  2. Analyze existing monitored emissions from WECC generators and develop higher fidelity emissions inputs
  3. Optimize unit commitment and economic dispatch with these inputs and examine impact of increasing penetrations of wind and solar on thermal units
  4. Examine mitigation options to reduce costs of thermal unit cycling and ramping.