Bridge To Our Energy Future?

Would it be a good idea to use more natural gas to generate electricity in the coming decades? The effect that would have on the economy, household budgets, the reliability of power supplies, plus the impact on the environment—the “yeas” and “nays” on this question make for challenging debates, and the outcome is still uncertain.

To understand the proposal, let’s look at the role natural gas plays in the nation’s power grid now, and how that could change.

In today’s electric grid, location matters. In some regions, natural gas is the leading star, on stage at all times generating electricity day and night in every season. In other regions, natural gas is only a supporting player, one who comes on and off stage at certain times of the year according to the weather.

The power grid’s needs:
base and peak loads
When deciding on what kind of power plant to build, electric utilities look at locally available resources in their region. They compare fuel costs and operating costs to generate electricity using different resources. In order to provide steady, reliable electricity, utilities must balance careful investments in equipment with their expected needs. Sometimes natural gas is the best choice—and sometimes it isn’t.

Before utilities make decisions, they must look at two needs.

The first need is called base load. That’s the usual amount of electricity all consumers want for many purposes throughout the day and night, week after week, month after month. Base load tends to stay within a predictable range for long periods of time. It’s the backbone of the power supply. A base load power plant is typically very large and operates almost all the time.

The second need is called peak load. That’s the added amount of electricity that consumers need in special situations. Peak load typically occurs during extremely hot summer weather or extremely cold winter weather.

Peak load tends to vary a lot: sometimes it’s just a bit more than base load for a few hours on a few days, and sometimes it’s a lot more during several weeks or months. A peak load power plant can be small, medium, or large. It must be able to be turned on quickly and then off again as the need for extra electricity goes up and down.

Kentucky and Louisiana provide good examples of the regional differences in power plant choices.

In Louisiana, there are only four coal-based power plants. In that state, the most plentiful local resource is natural gas, so abundant it’s used for both base load electricity generation and for peak load times.

In Kentucky, coal is the most plentiful natural resource available locally. Eighteen base load power plants that use coal provide about 90 percent of the state’s electricity during a year. The relatively small amount of natural gas used to generate electricity in Kentucky at peak load power plants comes through hundreds of miles of large pipelines from sources in Gulf Coast states.

A future of peaks,
bridges, and valleys
Any realistic discussion of a future power grid recognizes that electricity needs will still vary, and include both base load and peak load.

The U.S. Energy Information Administration says that natural gas provides about 24 percent of the nation’s electricity, and coal about 45 percent. These percentages count the power coming from all base load and all peak load plants in a full year.

One version of the future proposes using less coal for base load and building more natural gas power plants instead. According to the Environmental Protection Agency, “Compared to the average air emissions from coal-fired generation, natural gas produces half as much carbon dioxide, less than a third as much nitrogen oxides, and 1 percent as much sulfur oxides at the power plant.”

A new study released this past June by the Massachusetts Institute of Technology says that replacing many coal-based power plants with natural gas power plants over the next 25 to 30 years could be a valuable step toward reducing overall emissions in the power sector.

But increasing natural gas use for base load while continuing its role for peak load is not the end of the story.

Henry Jacoby, MIT professor of management and co-chair of the study, says, “People speak of (natural) gas as a bridge to the future, but there had better be something at the other end of the bridge.”

One possibility features solar and wind-based generating stations on the other side, renewable power resources that would replace many base load plants that use fossil fuels like coal or natural gas. But using more wind, which varies in strength, and more sunlight, which isn’t available at night, will change the steadiness of the supply of electricity. When renewables are not producing enough base load power, something else will be needed to make up the difference.

In that scenario, natural gas plays a new starring role—as the always-ready stand-in, able to take over at a moment’s notice when wind and solar stop working.