Can load-shedding technologies effectively provide immediate relief to the grid?
According to the EIA’s Annual World Energy Outlook 2008, total electricity usage in the world is supposed to approach 203 million GWh by 2030 across all sectors- residential, commercial and industrial. This number translates to a growth rate of 1.6 percent per year. Additionally, the last infrastructure report from the American Society for Civil Engineers downgraded the U.S. national power grid from a D+ to a D rating (on an A-F grading scale) and Europe also recognized the necessity to upgrade its transmission capabilities given infrequent, yet serious blackouts in the last few years. While most if not all agree that cleaner sources of energy are imperative, it is indisputable that that significant “gains” can be achieved through conservation and efficiency improvements. As the load demand reaches grid capacity in many areas, this is where some of the “low-hanging fruit” will be found.
Load-shedding is the process by which certain pre-established electrical loads are decreased or shut off as soon as peak energy demand is reached. Technical advancements have made this an easily implementable approach to managing energy demand. Recently, Axis Technologies Inc. announced the development of their next generation of energy-efficiency ballasts; a technology that is riding the wave of success from their original designs for daylight harvesting ballasts. The new prototype will provide load-shedding capabilities via wireless connection to the local power company’s Peak Demand Reduction Program, similar to the one initiated by the New York Power Authority in summer of 2008. Through breaker sequencing, Schneider Electric is addressing the same issue at a much larger scale delivering engineering power system control solutions to more industrial and commercial-type clients.
The true benefits of this type of technology can be seen when applied at a more macro-level. As previously mentioned an outdated grid combined with increased load establishes a propensity for blackouts. When the grid reaches capacity the natural tendency is for the AC transmission frequency to decrease. In a process called “under-frequency load-shedding”, pre-established constant values are given to the frequency settings, time delay settings and load-shedding amount, thus ridding the system of demand completely agnostic of the actual grid disruption. In an article in IET Generation, Transmission and Distribution entitled, “New Centralized Adaptive Load-Shedding Algorithms to Mitigate Power System Blackouts” researchers actually propose a unified system that reacts to disturbances by evaluating system responses and/or events (e.g. low voltage/stability and plant outages respectively). Load-shedding responds to the disturbance location and the amount shed is proportional to the magnitude of the disturbance. Through modeling, this methodology proved to both preserve stability and minimize the amount of load-shedding necessary to maintain stability.
On both sides of the micro and macro equation creative applications of load- shedding can provide answers to our preeminent concerns about the current grid infrastructure capacity. Part of the energy solution is making sure that the transmission capacity we currently have is being used in most efficient way possible and load-shedding is one technology which can both stave much needed infrastructure investment and realize immediate cost savings.
For information on adaptive load-shedding check out IET Generation, Transmission and Distribution, January 2009 Volume 3 Issue 1 http://www.ietdl.org/
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