Ken Allen, Chief Operating Officer, Principal Solar
April 18, 2012 | 2 Comments
As the nation looks to the sun for alternatives to conventional fossil fuels for generating power, the electrical grid is being seen by policymakers in a significant new light. Improving interconnectivity of the electrical grid infrastructure has the potential to accelerate the advancement of renewable energies – solar, wind and geothermal – into the nation's mainstream power supply. The problem, however, is that a good portion of these abundant and unlimited resources are generated in remote markets that make transmission to the nation's electrical grids for distribution and storage to the benefit of massive populations ambiguous, at best.
As utility companies clamor for solutions to utilize the upside of these currently intermittent sources of energy, more emphasis is needed to develop solutions to effectively absorb solar, wind, and geothermal alternatives to the electrical grid without destabilizing a region’s power supply.
Now is as good a time as any to find answers. New legislation – some states are mandating as much as 40 percent of their power supplies come from alternative sources in the next few decades – has made the challenge imperative for grid operators and regulators to store and manage large amounts of energy from solar and wind sources more efficiently and effectively.
The task is in its infancy, but the ultimate goal is certainly attainable. A better understanding of electrical grids, these highly regulated pathways to transmit and distribute power across the nation, could enable the sale of renewable energy across a wider region and develop markets where it is needed most – reducing the nation’s dependence on foreign oil and, most importantly, providing cleaner air to breathe, today and tomorrow.
Making it Work
Transmission systems are typically controlled by private and public utilities or related companies. They are managed by Independent System Operators (ISO), which are non-profit entities autonomous of all individual market participants and segments in the electrical utility industry. ISOs oversee electrical grids for specific areas of the country to ensure equitable and reliable access and pricing. Under the authority of the ISO, local electrical grid systems are most commonly run by local utilities, which retain ownership and the responsibility to provide restoration, maintenance and metering services.
When more wind and solar renewable energy systems are added to the electrical grid, the ISO must become more sophisticated at predicting daily wind and cloud patterns, and the resulting generation likely to be available from wind and solar systems. Renewable energy sources can be significantly affected by wind and cloud patterns compared to their fossil and nuclear counterparts at power plants. Therefore, ISOs must ensure that sufficient controllable resources, such as natural gas, coal and nuclear, are on-hand to meet energy demands.
Forms of power affect the electrical grid differently. Stability is optimum when the frequency is at 60 cycles and the transmission voltage is within a specified range. System instability can occur when generation does not match load, causing frequency and voltage to deviate from normal. Electrical grid stability must be maintained during these system upsets.
The process for interconnecting power resources and, specifically, renewable generation with a utility system can involve federal, regional and state regulatory agencies as well as utility personnel, consultants and attorneys. The ability of a grid system to accommodate a new power resource is dependent upon many factors including feeder loading, substation capacity or MVA rating, the existing protection scheme of the system and conductor size. Sufficient capacity to handle the increased power flow must be available or, in most cases, the new resource operator will be responsible for the cost of system upgrades.
When connecting to the grid, several studies must be conducted to ensure the transmission system will remain stable. Studies determining how the grid will react to the new generation source and potential reliability issues may need to be examined. Engineers can then determine the equipment necessary to ensure stability and reliability. Once these studies are completed, costs can be evaluated to determine if the project has a reasonable chance for success.
Ron Seidel, PE, Board of Directors, Principal Solar, contributed to this article. Seidel is principal of RBS Energy Consulting, where he interacts with private equity, investment banks and government on energy issues, most notably for the Electric Reliability Council of Texas (ERCOT). He is a past president of Texas Independent Energy, where he had full P & L responsibility for two 1,000-megawatt combined-cycle plants in ERCOT; senior vice president of Energy Supply at City Public Service of San Antonio; and an executive at TXU as senior vice president of Fossil Generation and Mining, president of TXU Energy Trading, and operations manager at the Comanche Peak Nuclear Plant.