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.
Growing Pains
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.
Potential Solutions
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
Storage Batteries
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. 2While the incident remains under investigation, it nevertheless serves as a reminder that there are safety risks that must be managed whenever large amounts of energy are concentrated in a single location.
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
Growing Pains
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.
Potential Solutions
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
Storage Batteries
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. 2While the incident remains under investigation, it nevertheless serves as a reminder that there are safety risks that must be managed whenever large amounts of energy are concentrated in a single location.
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
