Three Approaches to Grid Stabilization
Around the world, alternative energy sources are being connected to utility grids to improve sustainability and reduce environmental impacts. Nevertheless, the proliferation of power sources can make grid management more complex. This article quickly surveys some responding approaches and shows how load banks can offer value.
Utility grids typically connect multiple power plants to customers across a wide area. To ensure safe and proper operation, the voltage, frequency, and other electrical characteristics of the grid must be maintained within specific ranges. If these parameters go out of range, the grid could become unstable, producing effects that impact or damage equipment on the power network. One effect … when the amount of power on the grid exceeds demand, its operating voltage can increase, creating a reverse power effect that can damage power generation equipment in utility power plants.
One might conclude that utilities should reduce their power input by throttling back or shutting down generating stations. They can … to a point. However, powerplant generating apparatus, which typically involves large steam boilers and complex and sensitive steam turbines, may not be able to operate properly without producing a minimum amount of power. In addition, a utility could face high expenses and operating losses if its generating apparatus is not loaded as designed. For these reasons and more, utilities need to maintain base levels of power output.
There are a variety of solutions for managing excess power that would otherwise destabilize a power grid. The following sections briefly survey three approaches.
1. Store the Excess Energy for Use When Demand Increases
Several means can be used to store excess energy for consumption when demand exceeds supply. One approach is to use storage batteries, which charge whenever excess power becomes available, then discharge when demand increases. Doing so at scale can apply sufficient load to avoid a reverse power condition and meet peak demands. Perhaps the most famous example of a battery storage solution is the Hornsdale Power Reserve near Adelaide in Southern Australia, which uses technology and equipment developed by Tesla.
This approach is not without limitations. One is that batteries have a finite capacity to store power. This becomes relevant when the area served by a grid experiences an extended run of sunny temperate weather. When the batteries reach capacity, there will be no further ability to absorb excess power. Without another means to absorb or consume this power, the batteries could fail to stabilize a grid once fully charged.
Furthermore, defects in design or manufacturing could result in conditions such as thermal runaway, where batteries become hot enough to cause fire or thermal damage. In February 2018, the U.S. Consumer Product Safety Commission reported 25,000+ incidents of overheating or fire involving more than 400 types of lithium battery-powered consumer devices over five years. 1More recently, lithium-ion batteries that power automobiles may have played a role in a fire that resulted in the sinking of a cargo ship. 2
Hydraulic Energy Storage
Another energy storage means involves hydroelectric generation. A water reservoir can be created to store water above another watercourse by erecting a hydroelectric dam. During periods of excess power, utility power is used to pump water up from the watercourse into the reservoir. When power demand increases, the stored water is released from the reservoir through generation equipment in its dam to create power. The Yards Creek Generating Station in New Jersey, USA is an example. Water is pumped up daily from the Delaware River into two reservoirs when power demand is low, then released back to the river when power demand is high. The reservoirs cover more than 450 acres (182+ hectares), store more than 10,000 acre-feet ( ~13 million cubic meters) of water, and can provide up to 420 megawatts of power.3
For all of their benefits, energy storage projects present multiple characteristics that must be considered. These include:
Space Requirements: Storing energy at scale requires space, potentially much of it. For a battery storage project, the equipment footprint can be large, for a reservoir, much larger still. Consequently, these facilities work best outside of urban areas where space is less likely to be available and surrounding communities would more like be affected by potential impacts.
Finite Capacity to Absorb Load: When batteries are fully charged or a reservoir is full, the solution can no longer be used to stabilize the grid when excess power is available. Likewise, a completely filled energy storage solution cannot distribute power until sufficient demand returns.
Environmental Impacts: The life cycle of energy storage solutions impacts the environment, albeit in different ways. For batteries, environmental concerns begin with the mining of minerals, extend through manufacturing, and then to disposing of the toxic substances used to construct them. For hydropower, the construction of a dam and reservoir consumes a large area of land that might otherwise have ecological, agricultural, or economic value.
Safety Considerations: Overcharged batteries can present safety issues. Events such as fires in consumer electronics and at Tesla’s own battery storage facility show the potential results of problems in small-scale and large-scale battery storage systems. Dams used to create reservoirs typically provide reliable service, but must be properly designed, constructed, inspected, and maintained to avoid undue risk to downstream communities. Regardless of the technology, storing large amounts of energy in one place requires precautions to avoid events that could impact human health, safety, or the environment.
2. Convert Excess Energy to Fuel
Excess electricity can power the electrolysis of water, a relatively straightforward process that yields hydrogen and oxygen gases. Industrial uses for these substances already exist, and hydrogen can be used as a fuel stock. Oxygen is also used in healthcare. A cleaner-burning fuel, wider use of hydrogen could play a role in future energy strategies and has been suggested as a replacement fuel for motor vehicles and other applications that presently rely on petroleum.
Some concerns with converting excess energy to hydrogen include:
- Hydrogen production and storage facilities require adequate space. Utilities may not be able to place these facilities where excess power is available, thus requiring the construction of transmission infrastructure to production locations.
- The use of excess grid energy is dependent upon the proper functions of any hydrogen manufacturing process or facility. If hydrogen production is interrupted, the facility cannot be used to stabilize the grid when needed.
- Chemical manufacturing is beyond the existing business interests and core competencies of most electricity producers. Using third parties to use excess energy to produce hydrogen could introduce business risk.
- Hydrogen and oxygen are explosive gases that are typically stored under pressure, and thus present safety risks that must be managed.
- Beyond present uses, there is no infrastructure in place for an emerging “hydrogen economy”. Without additional infrastructure, there may be no demand for all of the hydrogen that could be produced.
- It may not be practical to locate hydrogen production near where excess power is available, particularly in densely developed areas.
- Like the energy storage solutions above, hydrogen production cannot be used to stabilize a grid after storage facilities are filled to capacity.
3. Absorb and Dissipate Excess Energy Using Load Banks
Load banks are electrical devices that convert power to heat, which is subsequently dissipated to the surrounding environment. Easy to install and operate, they do not rely on the chemical conversion of energy in the way that storage batteries and hydrogen production do.
Suitable load banks are available to the power industry now and offer compact footprints as well as favorable capital and operating costs. Furthermore, they can operate regardless of weather conditions, and because they are never “full”, they can provide stabilizing loads indefinitely. They can be used nearly anywhere excess power is available.
Unlike the other solutions reviewed, load banks dissipate excess energy. While the other solutions use some of the excess power to convert energy from one form to another, load banks absorb the entire excess amount. In this sense, the efficiency of grids that use load banks could be less than grids stabilized by other means. Nonetheless, viewing this inefficiency against the consequences of an unstable or damaged electrical utility grid can make load banks an attractive option.
The proliferation of alternative energy sources offers sustainability benefits but can make the operation of a reliable utility grid more difficult. When new sources result in excess power, solutions are needed to ensure the proper and reliable operation of the utility grid. Storing energy in batteries and water reservoirs can help stabilize grids by absorbing energy when excess supply is available, then releasing stored energy back into the grid when power demand is greater. Likewise, power can be used to manufacture fuel for later use. These types of solutions require space, present safety and logistical issues, and offer finite capacities for storing energy. In contrast, load banks offer a compact and reliable stabilization solution for managing excess power and are available to do so now.
1United States Consumer Product Safety Commission. Status Report on High Energy Density Batteries Project. February 12, 2018. p.4. https://www.cpsc.gov/s3fs-public/High_Energy_Density_Batteries_Status_Report_2_12_18.pdf?UksG80UJqGY0q4pfVBkbCuUQ5sNHqtwO, accessed March 11, 2020.
2Quartz Media, Inc. Lithium-ion batteries are fueling the fire on a burning cargo ship full of Porsches. Aurora Almendral. February 21, 2022. https://qz.com/2130711/electric-vehicles-make-it-harder-to-quell-fire-on-felicity-ace-cargo-ship/, accessed March 14, 2020.
3National Association of Utility Regulatory Commissioners. Nexus between Water and Electricity: A Visit to the Yards Creek Pumped-Storage Hydro Station. Uprenda Chivukula. Undated. https://www.naruc.org/bulletin/the-bulletin-03-08-2018/nexus-between-water-and-electricity/, accessed March 11, 2020.
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