Why Transitioning to Renewable Energy Leads to Power Outages
According to Xcel Energy, the largest electric utility company in the state of Minnesota, the closing of large “baseload” power facilities in favor of renewable energy sources like wind and solar could have serious consequences, including power outages and widespread blackouts in the future.
Indeed, with recent rolling blackouts hitting California – home to the most solar capacity of any state in the country – we are already seeing these consequences play out in real life.
Baseload power facilities are typically fuel-based generators – such as coal facilities like Sherco and AS King and nuclear facilities like Monticello and Prairie Island – that produce enormous amounts of electricity year-round.
As Xcel states in Appendix J2 of the utility company’s most recent resource plan, “the ability to provide reliable electric service depends on a complex and interconnected network of generating resources and transmission infrastructure that provides capacity and delivers energy to customers.”
This “complex and interconnected network of generating resources” – comprising of transmission lines, distribution centers, and power facilities – acts, as Xcel describes, like a large synchronous machine of interconnected gears (i.e. power facilities) that depend on large baseload facilities serving as “a strong backbone for the machine’s operation.”
The Electrical System Depends on Baseload Power
“In fact,” Xcel continues, “the Upper Midwest grid and the NSP System has been designed around the current baseload units, and relies on the unique aspects of these units to not only generate capacity and energy for our customers, but also to provide numerous essential system operational services.”
In other words – Minnesota’s electrical grid, and those of surrounding states, have been built around the existence of large baseload power facilities like Sherco, AS King, Monticello and Prairie Island serving large amounts of electricity into the system and maintaining reliability.
As explained by Xcel:
The existing transmission system has been developed to be able to receive the approximately 2,400 MW of power injected from Sherco, 671 MW injected from Monticello, 598 MW injected from King, and 1,150 MW injected from Prairie Island and to deliver it to various area substations to meet the electrical power demands of customers. This power deliverability capability is often referred to as “transfer capability” or “thermal limits” of the system. Transmission systems are made capable of receiving and moving power from specific generators at specific locations; changing generator characteristics or locations requires corresponding changes to grid capabilities.
Xcel goes on to warn that “When analyzing the impacts of ceasing operations at one of our existing coal or nuclear units, it is important to consider these operating and technical characteristics beyond just the unit’s energy output.”
To put it plainly – Xcel is saying that transitioning the grid from large fuel-based generators to renewable energy is not as simple as closing coal and nuclear facilities and installing wind turbines and solar panels.
Wind and solar energy sources are fundamentally different from energy sources like coal, natural gas, and nuclear power. Even if Minnesota installed enough renewable capacity to match the energy output from coal and nuclear facilities (which would be an enormous amount of capacity given the low capacity factors of both wind and solar, which are sometimes not operating at all) these facilities still wouldn’t be as beneficial to the resiliency of the electrical system as traditional fuel-based sources of power.
Without Baseload Power, the Electrical System Loses Key and Necessary Features
In fact, Xcel states at least six important features baseload energy sources like coal, nuclear and combined-cycle natural gas facilities offer that wind and solar inherently cannot provide. Even more alarming is the fact that these features are essential for the entire operation of the electrical grid, and it would not be as resilient without their existence.
In Xcel’s own words, here are those six indispensable features:
Already quoted and discussed above, power deliverability describes the capability of baseload generators to serve large amounts of electricity to the system to “meet the electrical power demands of customers” throughout the state.
Large generators like Sherco Unit 3 and King have large spinning shafts that provide a strong backbone for the machine’s operation. With enough of these big “gears” spinning, the machine can stay electrically stable and continue operating without interruption when small gears drop in and out of operation (like when the wind stops blowing or sun stops shining), or when another big gear drops out, or a “contingency,” happens to some part of the machine. These large gears are also more likely to stay connected to the grid during a contingency than the small gears because large rotating masses have more inertia and are therefore not as easily jarred, or disrupted by a disturbance. Having the large gears in place also enables more small gears to be connected to the machine because they don’t have as much impact with the large gears in place. The large generating units thus provide “dynamic stability” to the grid.
Large synchronous generating units provide “fault current,” which is necessary for the system protection equipment to function properly. If the system has too little fault current, it is difficult for system protection systems to differentiate customer load from an electric fault, which could cause the protection system to not function properly. The protection system is the overarching electrical monitoring scheme that assesses the real time condition of the transmission grid and acts to prevent damage to system components and prevent cascading failures. The large generating units operating today are important sources of fault current, and the protection system and existing deployed assets rely on sufficient fault current for the protection system and other electrical facilities to work as designed. Many of the electric devices that are deployed on the grid and in service today, such as wind generators and other assets, are engineered and designed to function properly with the amount of fault current that has been historically available on the grid. Therefore, changing the amount of fault current on the grid could not only impact protection systems, but could also impact other electric assets.
Black Start Capability:
In the event of a major regional grid outage, firm dispatchable generating units with a secure fuel source are an integral resource to restoring power to the electrical grid, or “restarting the machine.” Only firm dispatchable generating units of a certain size that are capable of creating and absorbing reactive power are eligible to perform black start functions. Once Sherco Units 1 and 2 retire, the Sherco Combined Cycle (CC) will be an important part of our black start plan. Renewable generation, such as solar and wind are not currently considered eligible Target Units due to their inherent intermittent nature, and their inability to provide or absorb reactive power. A large battery energy storage system can be configured to be technically capable of providing black start service, likely as part of a relatively small Initial Black Start Unit. However, they may not yet be economically viable for this purpose. There are also technical concerns with regard to how batteries can absorb reactive power, which would be needed if the battery was not paired with another type of generation asset.
The real time conditions on the transmission system are constantly changing and require ongoing adjustments to maintain voltages at required levels. Large synchronous power sources like our current baseload units, provide significant system voltage support along with necessary “reactive power.” Reactive power is required to start and run motors, like in air conditioners and industrial equipment (called “inductive loads”). Large population centers generally require large generating units located reasonably nearby to support system voltage effectively. As in the dynamic stability discussion, without enough large units in place, the machine isn’t as capable and robust when it runs.
System regulation essentially means the ability of the system to respond to changes in usage, i.e. keeping the generators and loads matched at all times. Combined cycle generating units have the electrical characteristics to provide this fast response balancing in real time. The system frequency, required to be maintained at 60 Hz in the US grid, is an active measure of this balance. When there are changes to the generation/load balance, as when wind speeds drop or a large industrial load comes online, the frequency drops if there is insufficient regulation capability on the system. This is another aspect of the dynamic stability of the system, typically in a longer timeframe.
Renewable Energy Advocates Need to Address ALL the Limitations of Renewable Energy – Not Just Low Capacity Factors and Intermittency
Advocates of 100% renewable energy – like Democratic nominee and former Vice President Joe Biden – have a lot of work cut out for them to explain how in the world they plan on addressing these necessary features of the grid in the absence of large fuel-based generators.
The recent rolling blackouts in California are excellent examples of what can happen when these features aren’t addressed properly, and when politicians and grid operators prematurely rush into propping up energy sources that aren’t able to support the grid in all the complex and intricate ways it operates – such as wind and solar energy.
Before Minnesota goes any further into the current “transition” to renewable energy – as wind and solar already make up around 25 percent of total capacity in the state – Minnesotans should be asking state leaders to explain how they plan on addressing these important features of the grid in the absence of coal, natural gas and nuclear facilities.