Harmonizing Edison and Tesla with HVDC and Microgrids
- Written by Massoud Amin
We envision a drastically different electric grid than what exists today, one with efficient markets, idealized grid-pervasive demand-response, rapid real-time end-point control, smart peripheries and fully coordinated networks of microgrids, synergistic electrified transportation, green and automated distribution systems and efficient AC-DC transmission systems. That kind of grid will effectively and securely meet demands of a pervasively digital society in the face of extreme events and climate change while ensuring a high quality of life and fueling economic growth.
If Thomas Edison had had his way in the late 1880s, microgrids with direct current and distributed generation would be the norm, as all power would be produced and used locally, rendering transmission lines unnecessary and impractical. But Edison, at the time he lived, was wrong. Nikola Tesla had a better idea and won the first "battle of the currents," thanks in large part to George Westinghouse, who commercialized his inventions and built the first power generators at Niagara Falls to supply markets in New York City.
Today’s global grids, based on the prevailing model of electrical generation and distribution, operate mainly on alternating current (AC), achieving an efficiency of nearly 97 percent for High Voltage Alternating Current (HVAC) transmission lines, which constitute the backbone of nearly all power grids.
Large turbines produce several hundred megawatts of electricity and then transformers step up the voltage so it can be transmitted long distances with minimum loss. At the other end the voltage is reduced to a lower level by step-down transformers for delivery to end-users. Taking all elements into account, today’s power grids are networks of generation plants, transformers, DC/AC and AC/DC converters, high-voltage transmission lines for long-haul transfers, low-voltage distribution lines and substations for short-haul transfers into homes, offices and factories.
Thus, while Edison and his team invented the light bulb, it was Tesla who envisioned and invented the entire infrastructure needed to power those light bulbs.
Fast-forward to today, some 120 years later: A new battle of the currents is arising, both in local distribution and bulk transmission. On the home front, new digital technologies and appliances such as computers, mobile devices, LED lighting and electric vehicles use or work better on DC rather than AC. Nationally and regionally, High Voltage Direct Current (HVDC) lines promise higher efficiencies and lower losses than HVAC in transmitting large volumes of current from new sources of generation—the sunniest or windiest regions, for example—to cities and industry. By 2030, up to 40 percent of electricity demand could be satisfied by wind generation, if the transmission system is augmented with a stronger HVDC backbone.
I am often asked whether we should have a high-voltage power grid or go for totally distributed generation, featuring microgrids for example. The short answer is that we need both.
Considering the whole North American system, in order to address energy security and integration of available generation resources, as well as for increased environmental, economic and national security, our first strategy should be to expand and strengthen the transmission backbone by adding about 42,000 miles of high-voltage transmission lines to the existing 450,000 miles. This expansion will cost about $82 billion, provide 210,000-214,000 sustainable good-paying jobs and will result in about 40 percent of electricity to come from integration of wind resources in the United States. Most of that new transmission will consist of HVDC lines. Locally, highly efficient microgrids combining heat, power and storage systems will be built out over 20 years, at a cost of $17-24 billion annually. At all levels, smarter grids come to have self-healing capabilities.
Localities are starting to build microgrids to serve campuses, communities and cities, and many of those microgrids will be fully DC, drawing their power from locally available and preferably renewable sources like wind and photovoltaics.They use smart grid technologies to continually monitor customer demand and offer innovative pricing and other programs to manage demand and encourage customers to conserve energy; excess energy produced is fed back into the grid.
Microgrids can be almost entirely self-sustaining. In fact, they can produce as much energy as they consume and generate "zero net" carbon emissions. We have shown this at the University of Minnesota, where we are building and demonstrating a microgrid on one of our campuses. Using biomass from nearby farms, as well as solar and wind resources, it will soon be energy-self-sufficient. It has been zero-net-carbon since 2008.
Cities, communities, and universities are great candidates for microgrids because microgrid projects are manageable in size. Citizens can have a real sense of involvement, become enthusiastic about new opportunities and develop a determination for programs to succeed. Microgrids provide a context in which innovations like smart homes can be tested and demonstrated with consumers.
Certainly, the power grid backbone also needs to become increasingly efficient, integrating renewable resources that reduce society’s need for fossil-based resources, among other approaches. The upgraded backbone, combined with microgrids, will help us meet our goals for an efficient and eco-friendly electric power system.
The expectation in the power industry, according to research commissioned by IEEE and published in December 2012, is that smart microgrids will play a growing role in meeting local demand, enhancing reliability and ensuring local control of electricity The microgrids concept may eventually be extended to higher voltage levels, to create self-contained, self-sufficient systems.
For reliability’s sake, multiple automated microgrids could be built with similar properties and arrayed in a "cellular power network" in which each microgrid possesses numerous independent, intelligent decision-making agents in a multi-agent architecture. These intelligent agents gather and exchange information with each other in real-time or near real-time in order to provide coordinated protection and to optimize system performance. Asset management in this context requires more than sensors that enable condition-based maintenance, as is the case elsewhere on the grid. Asset management means understanding how a cellular power network behaves and how it can be managed and maintained for optimal performance.
Microgrids that incorporate a dynamical systems perspective encompassing threat and uncertainty have been tested by various methods to investigate the performance of a multi-agent architecture. In contrast to a computer science perspective focused on securing data, the focus of assessing the efficacy of a multi-agent architecture is on analyzing the actions or dynamics of network components and their overall management. The goal of such assessments is to determine the expected performance of such systems, including the effects of failure, repair, contention for resources, attacks and other uncertainties. Simulation models capture detailed system behavior, but they require a great deal of time to run. Analytical models, in contrast, create an abstraction of the system, but once set up, they make it easier and faster to carry out trade-off studies, perform sensitivity analyses and compare design alternatives.
The development and deployment of bulk energy storage also has a critical role to play in supporting the power delivery systems of the future. Without an "inventory" or "energy stock" to draw on, utilities have little flexibility in managing electricity production and delivery; intermittent renewable resources like wind and solar cannot be relied upon for hourly electricity supply, and therefore cannot be used to best effect without storage capabilities. Yet only about 2.5 percent of North American generation capacity is backed by storage plants. Most energy storage options, with the exception of pumped hydro and compressed air, are relatively unproven commercially; their value proposition is complex and poorly understood; and the uncertainties of changing regulatory rules makes storage options too risky for most investors.
We need collaboration between public and private organizations to analyze the costs and benefits of existing storage options, and sophisticated tools to predict the costs of producing large-scale storage systems 5-20 years in the future. We also need new models to simulate the economic characteristics of future power delivery system conditions to predict the potential benefits of storage options to generation, transmission and distribution owners as well as end-use consumers. What will also be essential is high-end communication to key stake holders to address investor concerns about existing or new storage options and modernizations.
And that is not all. Accounting for uncertainties and managing risk at all levels can and must be addressed in a transparent dashboard at a level of detail that consumers, regulators, decision-makers and investors demand - that is, a smart dashboard of "Google-Bloomberg"-like analytics with fast-solving dynamical stochastic systems, for a smarter grid and energy options, now in the making.