The traditional Grid is composed of energy producers, distributors, utilities, customers, and regulators. The Grid was designed to safely and reliably distribute energy from large generators through monitored transmission lines to consumers – with major aspects of energy generation and distribution controlled. The Grid has preventive control over potential Grid disturbances, in part, by monitoring the use of power and dispatching or absorbing real or reactive power, as needed, to a section of the Grid.
This centralized generation system was designed for one-way energy delivery. The traditional Grid was not designed to handle small amounts of power produced from many locations with varying and uncontrolled outputs and two-way delivery, as presented by distributed renewable energy systems, like solar and wind.
Solar energy has been widely successful, fueled by energy usage, greenhouse gases, and general concern for the environment. Initially, these renewable technologies seemed to be the solution for our energy future. However, today these technologies have introduced a whole set of new problems that have disrupted the grid, and the problem only gets worse with each additional solar panel installed on someone’s rooftop.
The reasons are threefold: 1) intermittency 2) uncoordinated distribution and 3) failure to produce all forms of energy
- Intermittency: solar and wind power are inherently intermittent, as they rely on the unpredictable nature of our environment. When the clouds block the sun, and thousands of solar panels stop generating power instantaneously, the voltage dropoff can have devastating effects on the Grid. The Grid is forced to instantaneously turn on generators (in most case from “dirty” power sources) for voltage support and to supplement the loss in power. These voltage support issues can have rippling effects on entire Grids, and are often the cause for rolling brown outs.
- Uncoordinated Distribution: traditionally the Grid has operated as a coordinated unit. Energy was produced on an as needed basis, and coordinated through independent system operations (ISOs), utilities, and generators. Along come renewable technologies, and now, anyone with a rooftop can generate power that feeds into the Grid. As a result, power is being pushed into the Grid at times and locations when it is not needed, and there is nothing that the system operators can do to control it.
- Failure to Produce All Forms of Energy: solar was developed to offset the amount of kilowatt-hours a residential customer sees on his bill. For most people, this is the extent to which they measure their energy usage. However, watts are only one form of power. Energy is actually made up of both real and reactive power—billed separately on most commercial and even some residential “smart meters.” Reactive power affects transmission efficiency, voltage stability, and is crucial to the Grid’s ability to distribute energy efficiently, but is neglected by almost all solar installations. Much of the voltage support issues caused by intermittency can be resolved through the supply or absorption of reactive power, while adding a new revenue stream to a solar system.
The Evolving Grid
With the growth of renewable energy, utilities, ISOs, and government regulators have been struggling to resolve the conflicts arising from calls for a greener energy with the realities of the Grid. Much of the debate has focused on solar which has grown rapidly due to wide adoption. Hawaii, which saw huge solar growth in the last few years as a result of extremely high energy prices coupled with an aggressive renewable energy policy, had to significantly reduce interconnections for solar systems because the Hawaiian island Grid was becoming dangerously unstable. Today, it is increasingly difficult to get an interconnection for solar systems in many areas of Hawaii.
California is currently trying to balance the capabilities of its Grid with the statewide mandate that will require California’s energy production to be 1/3 renewable by 2020. As a result, the California Public Utilities Commission (CPUC) has proposed sweeping changes to Electric Rule 21 which regulates Grid interconnections to require solar installations to provide increased functionality including voltage support (read more here). The Western Electric Industry Leaders (WEIL) Group—an industry group composed of nearly all the top executives of the utilities in the Western United States—put out an open letter to the public, suggesting that if we are to continue with rapid solar growth, than system owners will need to start installing “smart inverters” that are able to manage voltage locally to offset the Grid disrupting effects that these systems cause.