Operations & Maintenance

Nuclear consultant, Margaret Harding, offers her insights into how smart grid technologies can boost storage capacity on the already constrained US grid network. She also looks at how nuclear's demand response record could actually help solar projects and overall power stability across the US.

By Margaret Harding

The concept that smart grids are separate from, and conflict with, traditional grids has been discussed in recent times. A key fact that has to be understood is that the current electricity grid in the US is a demand system. That is, electricity is generated as it is demanded.

Very little storage capacity is available on the grid today. This makes electricity generation, transmission and distribution among the most complex systems in the world. This relative inelasticity of the industry is at the heart of the issues of intermittent power supplies and demand response.

In the past, electricity supply was generated through means that were fairly well controlled. Baseload was provided by coal, hydro, and nuclear with some natural gas and other sources.

Natural gas and some of the older less efficient oil units were used to manage demand with highly responsive systems coming on line as demand increased.

Stressed out grid

However, with the advent of intermittent power suppliers like wind and solar, and changing load curves due to increasing electricity usage (electric cars, more electrical appliances and equipment), the traditional methods of managing the grid are being significantly stressed.

In addition, there are significant losses of electricity occurring in the current US transmission and distribution (T&D) system as well as inflexibility for transmission of electricity across long distances required to use intermittent sources that are generally more available in the west at major population and industrial centers in the east.

Voltage events, even minor reductions in voltage, have increasingly significant effects on society. With the increased use of computers and sensitive electronics both as stand- alone devices and as a part of equipment used both in industrial and residential applications, we need to find ways to assure the reliability of the grid is as high as possible.

What is ‘smart grid’?

Smart grid is really about improving the reliability of the overall electricity supply. This entails managing supply as well as demand, but most importantly, the T&D of electricity.

By better sensing and prediction of potential issues, including intermittent sources like wind and solar, faults such as transformer failures, or voltage irregularities, and increasing demand, a “smarter grid” will allow various energy sources to work together more effectively with fewer issues reaching the industrial, commercial, and residential consumers of electricity.

Where does nuclear fit in?

How do nuclear energy facilities contribute to the overall reliability of energy supply? And how can they support some of the other initiatives on the grid?

In the US, generation and T&D have been separated in many markets. This separation means that nuclear generators don’t have direct ability to improve the reliability and detection of grid events in the T&D. However, it does not mean that nuclear utilities do not contribute to grid reliability.

Nuclear energy tends to be used as base load supply. The reasons for this are primarily economic, though technology does play a role. The economic reasons center around the fact that nuclear is a capital intensive energy source.

Because the majority of costs are in the design and construction of the facility, the owners of these plants need to operate them as much as possible to maximize the return on their investments.

Nuclear power plants can load follow, but at an efficiency cost in fuel use. Such load-following operation has to be planned for well in advance to assure safe operation of the plant at varying power conditions. Since most utilities want to maximize investment, they are reluctant to plan in advance of intentional operation at other than 100 per cent power.

This drive to be base load makes current nuclear energy facilities less an ideal match with wind energy for daily interaction where intermittency is less predictable and peak availability tends to occur in early morning hours when demand is low.

In a more seasonal evaluation, most nuclear plants target outages for spring and fall, both periods when wind is more reliably available and seasonal demand tends to be lower.

Nuclear solar combo

Nuclear and solar, however, can work together in some interesting and more optimal ways. Because solar is tied to hours of daylight and tends to peak at midday when demand is starting to rise to peak as well, nuclear and solar can work as baseload and peak demand response very effectively.

In addition, nuclear load-following is best used when a predictable pattern of reduced power and increased power can be used. As solar tends to be more predictable in its cyclical availability, nuclear energy fuel planning can be designed to work in concert with these arrays, should the amount of solar power being generated exceed demand.

Solid base of reliable power

Aside from nuclear’s direct interaction with intermittent sources, nuclear power plants can have their own impact on grid reliability. Responding to a loss of 1000 MW or more of electricity during peak demand periods can risk cascading failures if unexpected plant trips occur during operation.

Nuclear utilities have worked to continue to improve the reliability of these machines, with capacity factors moving into the 90% range and providing a solid base of reliable power. Unplanned reactor outages have become increasingly rare and allow grid operators to rely on nuclear energy for base load demand.

In addition, nuclear utilities have increased the robustness of their facilities to withstand loss of power events. By ensuring that the facilities will be available even during severe weather events, or that they can get back online quickly in the event of grid damage, nuclear energy facilities serve as anchor points in regional grid structures that can keep power delivery to consumers.

Margaret Harding is president of 4Factor Consulting. She has worked in the nuclear industry for more than 30 years and advises clients on quality, regulatory, technical, and business issues within the nuclear industry. Before starting her own firm, Margaret worked for GE for 27 years departing as Vice President of Engineering Quality in their Nuclear Energy division. Margaret received an ANS presidential citation for her role in communicating events at Fukushima and has appeared on NBC, Fox News, CNN and many others.

She has co-authored a paper on the effect of Fukushima on the nuclear industry and is teaching a class for Iowa State University called “Nuclear Energy in Society”.