Utilities exploring ways to integrate their renewable energy sources into their existing fleet should carefully examine the costs and characteristics of the many flexibility options at their disposal. This advanced planning can greatly reduce their investment needs, according to Jon Pietruszkiewicz, Project Manager, Black & Veatch.

“Our message to utilities concerning their variable energy renewable (VER) integration is this: Know your options, save money, don’t over-invest,” said Pietruszkiewicz. In fact, that is the title of his recently published white paper, which looks at a variety of flexibility options utilities should explore, as well as a case study of utility operations in Hawaii.

“Some utilities are often more influenced by what they are most familiar with rather than by a systematic evaluation of available flexibility options,” Pietruszkiewicz said. Black & Veatch has more than one way to approach the systematic planning. It can use modifications to existing tools or the Black & Veatch Adaptive Planning Framework to evaluate alternative technology and capacity plans, as well as the adequacy of these plans to meet all reliability requirements.

In Black & Veatch’s 2014 Strategic Directions: U.S. Electric Industry report, almost two-thirds of executives surveyed said they believe energy storage will be the most important single factor facilitating integration of variable wind and solar resources. The second and third most important factors cited by utility executives were “transmission system upgrades” and the addition of “new, flexible conventional power plants.”

However, Pietruszkiewicz said lower cost flexibility options than those typically considered are now available. “Variable renewable energy changes the shape of dispatch requirements so that system flexibility must be reassessed,” he said.

Some of the flexibility options that should be considered include:

• Wind and solar forecasting
• Allowing curtailment of VER
• Sharing operating reserves for ramp events
• Intra-hour scheduling and sub-hourly dispatch
• Sharing diversity and faster multi-utility dispatch
• Demand response for VER integration
• Implementing smart grid automation

This illustration shows the relative cost of various methods for providing increased flexibility.

Wind forecasting has advanced rapidly, and costs have declined, Pietruszkiewicz said. Utilities are starting to acknowledge that forecasting is a viable, low-cost integration technique. He said all of the Regional Transmission Organizations (RTOs) in the United States have adopted wind forecasting, and at least 17 balancing authorities in the western states are using VER forecasting. Solar forecasting is also being implemented at some western utilities. According to one utility executive, one day of reduced hedging costs pays for the cost of forecasters.

Pietruszkiewicz cited a study by the California Independent System Operator (CAISO) that discovered as VER penetration increases to 50 percent, over-generation becomes a significant problem. Grid operators generally may curtail any generation, including wind, to maintain reliability during emergency situations.

With intra-hour scheduling, Pietruszkiewicz said the faster scheduling improves the efficiency of balancing. “Sub-hourly scheduling allows more efficient use of available transmission capacity and enables operators to fully use the inherent flexibility of the existing generation fleet.”

He noted that the Federal Energy Regulatory Commission (FERC) now requires intra-hour schedules, CAISO mandates 15-minute scheduling, and other transmission owners are adopting 15‑minute or less schedules.

Another option includes multi-utility dispatching, Pietruszkiewicz said. “The pooling of load, wind and solar power into a larger balancing area results in less per-unit variability because of the diversity of load, wind and solar,” he stated.

Smart grid solutions that support utility operation efficiencies, reliability improvements and customer service can also support integration of high penetration VER, Pietruszkiewicz said. Smart communications and distributed monitoring/control systems can manage voltage, reactive power, power quality and other important grid characteristics.

Hawaii Utility Implements Adaptive Planning Framework

Hawaii is at the forefront of implementation of high penetration VER, Pietruszkiewicz said. Hawaiian Electric Company (HECO) has indicated that it plans to achieve a 67 percent renewable energy content by 2030. HECO will accomplish this by implementing a portfolio of mitigation options having varying levels of cost.  These include:

• Reducing the “must-run” requirements of thermal generators.
• Increasing the operational flexibility of existing thermal generation not slated for retirement.
• Selecting future thermal generation resources that have a high degree of operation flexibility.
• Using demand response as a tool for better managing system dispatch.
• Installing storage to provide regulating and contingency reserves.
• Curtailing variable renewable energy 3 percent of the time.
• Modernizing the power grid with smart technologies.

Distributed solar PV generation is a substantial part of the VER growth in Hawaii. The utility has expressed hope that the use of advanced smart inverters and other key grid modernization steps will enable HECO to ultimately triple the more than 300 megawatt connections existing on its grid.

Black & Veatch’s Adaptive Planning Framework was used to evaluate different solution approaches for HECO. The focus was to improve economics, flexibility, grid resiliency and other factors.

Pietruszkiewicz said the reliability features needed for a utility and the amount of flexibility required can be determined by time-series analysis of system production costs.

“Many different flexibilities exist, each having different reliability features and different costs and benefits,” he said. “Since electric systems should deploy the most economical resources for operational flexibility, multiple solutions should be studied to provide the desired reliability at the least cost.”

Published originally on Black & Veatch Solutions.