IRC Paper Addresses Renewable Energy Integration Challenges

A recent briefing paper on variable energy resources (VERs) has proposed various remedies that independent system operators (ISOs) and regional transmission organizations (RTOs) can implement when incorporating increasing amounts of renewable energy resources onto their grids.

The briefing is part of a more comprehensive paper submitted by the ISO/RTO Council (IRC) to the Federal Energy Regulatory Commission (FERC) in response to FERC's Notice of Inquiry on the Integration of Variable Energy Resources, which was issued in January 2010.

Increasing amounts of renewable energy, primarily wind and solar, will be required to meet state renewable energy targets, but current market and system operating procedures were originally designed around the relatively stable characteristics of conventional electricity generating resources.

The variable nature of renewable energy requires that market designs and system operations be altered. As a result, the industry has been developing new processes and tools in order to effectively integrate VERs.

"As an industry, we are making great strides in harnessing the power of variable energy resources," Paul Murphy, president and CEO of Ontario's Independent Electricity System Operator (IESO) and chair of the IRC, said in a press release. "Effectively integrating this new supply is a long-term process that requires us to refine our respective systems, modify our operating procedures, and make adjustments to our markets for energy, operating reserve and ancillary services."

According to the briefing paper, systems, products and procedures need to be put in place to obtain and utilize forecasts, improve the visibility of VERs, upgrade control centers and equipment, mitigate the intermittent nature of VERs, and modify operating procedures as required.

In addition, adjustments to the competitive marketplace will have to take place in order to successfully integrate more VERs. For example, bidding and dispatch procedures may need to be adjusted. Changes to ancillary-services procurement may also have to occur, and the impact on energy prices and capacity markets will need to be closely observed, according to the paper.  


Forecast accuracy

Forecast errors and the inherent variability of production are two of the key challenges posed by integrating more VERs. The reciprocal relationship between VER forecast errors and load forecast errors may increase or decrease the impact on system and market operations.

ISOs and RTOs are utilizing VER forecasting services and driving the renewable energy industry to make improvements to the data that lead to better centralized forecasts.

Many ISOs and RTOs say they achieve a better aggregate VER forecast using a centralized forecast rather than utilizing the sum of forecasts developed by VER operators, according to the report.

Centralized processes for forecasting wind energy have been established or are being evaluated in most ISOs and RTOs. The California Independent System Operator recently began developing a centralized solar energy forecast.

Good data that is made available in a timely manner is also an important factor in accurate forecasts. For example, operators of wind projects usually provide real-time meteorological data, such as wind speed and direction, barometric pressure, humidity and ambient temperature, as well as current megawatt output and availability. In addition, information about turbine availability is important because it indicates whether the operator is experiencing outages.

The paper concludes by saying that although challenges to integrating intermittent sources of energy remain, ISOs and RTOs are developing, implementing and improving tools - such as different forecasting methodologies - to efficiently and effectively incorporate VERs.