Base load generating capacity and US electrical grid reliability

Posted Oct 2, 2017 by Karen Graham
There has been a lot of talk lately about the U.S. power sector's "base load" power generation capacity being outdated and becoming less important in maintaining the grid's reliability, yet the DOE looks at the problem differently.
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In August, the U.S. Department of Energy released its highly anticipated grid study, finding cheap natural gas to be the main driver behind base load power plant retirements. This was very obviously, not good news for coal-fired and nuclear power plants.
Even though the study did not find a clear link between retiring coal and nuclear power plants and reduced electrical grid reliability, the DOE is asking federal regulators to "assume" this may be the case and create a rule to “ensure that certain reliability and resilience attributes of electric generation resources are fully valued.”
However, Alison Silverstein, who drafted the technical portions of the DOE grid study, says its summary and recommendations missed key points on grid reliability and resilience, according to Utility Dive. And while the final draft of the study did get some things right, DOE’s staff summary of the technical study focused only on DOE Secretary Rick Perry's specific questions.
What exactly is base load generating capacity?
We have heard the phrase "base load generating capacity" thrown about a lot lately, especially in connection with coal-fired and nuclear power plants. But what does the term mean?
Basically, in electrical engineering jargon, a "load" is the amount of current being drawn by all the components (anything being powered by electricity). A load would include such mundane things as a toaster, microwave oven or a machine in a factory. A load is further broken down into "base" and "peak" loads, depending on the type of electrical things connected.
Think about this for a second - Not all electrical appliances operate at the same time in a typical household, right? For example, a toaster may be used for a few minutes in the morning, while a computer or television may be used for several hours. And then there are the lights, and they are not turned on unless you go into a room.
OK, taking the example one step further - Some appliances, like a refrigerator and freezer, need to be plugged in at all times. Another example is the HVAC system controlling the heating, ventilation and cooling systems in our homes.
Base load and Peak load
Base load is the minimum level of electrical demand required over a period of 24 hours. It is also called continuous load, sometimes. This is because it is needed to provide power to components that run all the time, like refrigerators and such.
Conversely, peak load is the time of high demand. Peak loads are usually associated with shorter time frames, although with the extreme heat experienced in the U.S. and Canada this year, electric grids have had days of "peak load" consumption. Think of peak load as being when the kids get home from school and turn on their computers, the television and whatever else they switch on.
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Understanding base and peak loads in the electrical grid
SinoVoltaics looks at the electrical grid as a huge household. And usually, under normal conditions, the power needed for the electrical grid is fairly constant. And this constant power is required at all times. This is the base load.
Now, when the Super Bowl is playing, more people will be tuning in to watch, creating a demand for more power, and this short high demand period is called a peak load.
For years, coal-fired and nuclear power plants were referred to as "base load power plants." This term is no longer applicable because “Base load” is not equivalent to reliability or any other system needs. This is one of the things the DOE report in August got right, says Silverstein.
However, with the decline in coal-fired power plants and the closing of many nuclear power plants recently, it is evident that these large, expensive to run facilities are out-moded in our electronically-based, electricity-dependent society. And with the growing popularity of renewable energy sources, the idea that the power grid needs base load generating capacity has taken a backseat.
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The North American Electric Reliability Corporation (NERC) clearly identifies "Single Fuel Dependency" is a real risk-threat to power grid reliability, pointing out the power-energy mix is one of the important factors to sustaining U.S. power grids’ reliabilities in past and recent years.
However, as NERC also points out, solar and wind energy are "non-dispatchable’" power sources and can actually increase the need for added reserve power to maintain base load generation capacity. The NERC cites natural gas as being a good alternative.
And until storage batteries are commercially available to assist in generating base load capacity on a large scale, we will need to rely on base load generation provided by natural gas and nuclear power plants. Yes, the power sector's net generation sources have changed radically over the decades due to a number of factors including evolving technologies, like nuclear and renewables developments, and in our continually changing world, they will continue to evolve.