Challenges of Supply
An Evolving Energy Paradigm
All commentators agree that the current power grid represents a magnificent engineering achievement. As is often mentioned, the U.S. National Academy of Engineering declared electrification the greatest engineering achievement of the 20th century. Noting the changes already underway and the dramatic demands currently being made, high-voltage power grids may well repeat as the greatest engineering achievement of this century. Nonetheless, given the magnitude of the challenges current objectives pose and their somewhat contradictory nature, achieving our current goals may be attainable only at an unreasonable cost using the familiar centralized paradigm and minimal integration across fuels and energy carriers (F+ECs).
A more promising approach may be to partially decouple loads and dispersed resources from the highly centralized megagrid (the tightly controlled meshed grid upstream of substations) and to manage smaller energy sources (such as electrical and thermal) and sinks locally in microgrids.
Microgrids can potentially apply all available assets using all F+Ecs from both local and central sources and choose the technologies that best meet their objectives (be they cost, efficiency, environmental stewardship, or, most likely, a combination), while tailoring the quality of energy delivered to devices to match their highly heterogeneous delivered energy service requirements. Further, we now appreciate the added resiliency of decentralized systems, such as the Internet.
Consider the formidable smart grid improvements being called for:
- making the grid sustainable (primarily decarbonized) by increased end-use efficiency and dispersed renewable energy harvesting
- expanding transportation electrification beyond mass transit to private vehicles as well as serving increasing electrical building space conditioning and water heating with heat pumps
- increasing load responsiveness facilitated by inexpensive ubiquitous metering, communications, and control technology coordinated with building-scale generation
- establishing efficient competitive markets at both the wholesale and retail levels
- improving and maintaining high universal power quality and reliability (PQ+R) to meet the requirements of our digital economy
- hardening the energy supply infrastructure to extreme events, both natural and malicious, including cyberattack.
The hype surrounding the smart grid represents recognition of the changing technology and requirements of energy supply and use. There is growing agreement that current technology can provide energy as well as control PQ+R close to loads while integrating assets using multiple fuels and loads under local control; however, current group think remains impaired by a limited view of how the electricity supply industry must be reorganized and integrated around multifuel systems. Smart grid visions often start from the premise that the task at hand consists of refining the traditional centralized paradigm. But such thinking represents only partial recognition of the implications of emerging technology and the dramatic changes necessary and possible.
The yoke of high universal PQ+R must be lifted. The objective should be to provide the appropriate level of PQ+R given the need served using the most appropriate fuel and carrier, i.e., this should be largely an economic choice. Feeding gourmet power to gourmand loads is simply wasting precious resources. The framework also needs to be made feasible by allowing necessary tradeoffs between reliability, power quality, economy, and sustainability. Currently, PQ+R are thought of as absolutes, rather than tradeoffs, and as rules of thumb rather than chosen optimums. Further, it may well be that the future megagrid that can meet our current expectations in some dimensions (e.g., carbon footprint) cannot deliver others (e.g., high universal PQ+R). And further, the megagrid that serves our combined goals best overall may not be a high PQ+R grid at all. In other words, the way to lift the yoke is to provide for demanding gourmet loads locally, which already happens to some extent via back-up generation with local fuel storage, and via power conditioning, thereby leaving the megagrid to settle on its optimum global specs, appropriate for its multiobjective mission, including the delivery of huge renewable energy streams from remote sites to urban centers.
Somewhat paradoxically, a major driver toward smaller scale power generation derives from the need to increase the efficiency of fossilfired conversion because the heat loss that large central station generation involves is increasingly unjustifiable. Smaller scale combined heat and power (CHP) systems can deliver better efficiency overall, despite the economies of scale that have driven centralization to its current extreme. Thermal generation in large part takes place at stations far from potential economic sinks for its low-grade waste heat. The poor economics of long-distance heat transport argues for smaller systems close to heat sinks, with thermally activated cooling being one worthy of special note. Despite the apparent poor thermodynamics of this technology, economically it is often quite attractive because the displaced cooling load typically lowers peak electricity load in warm climates. Not only is this displaced electricity of great value but since the peak is reduced, all electrical supply infrastructure, both central and in the microgrid, can be downsized.
Similarly, controlled loads can be of great economic value to microgrids. You may think it fanciful, but it may prove true that a more localized perspective will lead to more rational tradeoffs between investment in supply versus the demand side, as well as across F+ECs. Could our historically chronic underapplication of efficiency, CHP, and load management be mitigated by decision makers with vantage points that offer a clear view of all opportunities available for meeting microgrid objectives? At a minimum, they will have a cost picture localized in time and space and adequate analysis tools to take advantage.
The integrated controlled energy microgrid can present itself in energy markets with savvy and at a scale compatible with current technology and practice, hopefully alleviating fears of managing hundreds of thousands, if not millions, of tiny resources relative to the grid. The microgrid can be the aggregator across resources as well as across fuels while buffering the megagrid from variable and/or lower quality resources. Deploying decentralized microgrids may facilitate achievement of our challenging objectives with a megagrid as we know it today, or even with a somewhat degraded alternative. In other words, if microgrids shoulder the burden of providing for critical loads, society may find that the megagrid that best serves our other requirements (e.g., delivering low carbon footprint electricity from remote renewable-rich regions to population centers) may in fact be a lower quality grid. We need a change in mind set away from defining the megagrid in terms of universal minimum performance standards and toward establishing a grid that matches our changing objectives while trading off its costs and benefits.
Beyond being a substantial new load, the future roles of plug-in electric road vehicles (PEVs) are many and potentially game changing. They offer the potential provision of mobile electricity storage and, subsequently, stationary storage using their partially degraded battery cells. Being mobile, PEVs may challenge the traditional paradigm simply by potentially undermining two of our industry’s cornerstones, price discrimination and unrestricted supply, while offering valuable services. Moving sources or sinks are unknown to traditional power systems, but they make electricity fungible and can provide both microgrid and megagrid services. The latter capability is increasingly recognized, while the former may ultimately prove the more important. Current electricity pricing rests heavily on approximation and discrimination, i.e., electricity tariffs do not accurately nor universally reveal the cost of generating and delivering electricity to any particular meter, while neighboring meters can carry significantly different prices. PEVs will make this scheme unsustainable because they will be able to trade in electricity, buying at times and in places where prices are lower and selling where the reverse holds.
Theft may also become a problem, while controlled access outlets remain rare. My office happens to be on the ground floor, and an outdoor extension cord ban has already been implemented. In addition to potentially changing the nature of the megagrid, the greater availability of storage (of all carriers) makes smaller scale systems more viable because one of their greatest problems, load and resource volatility, is attenuated. Cost-effective batteries are particularly important and are one of multiple dc devices likely in microgrids, bolstering the case for local dc power systems.
Our energy supply infrastructure challenge has been misstated by our profession. It shouldn’t be how do we maintain the current PQ+R of the megagrid while accommodating the emerging reality of high renewables penetration, competitive markets, enduse market participation, increasing loads including PEVs, extreme events, and other “threats.” Rather, it should be what is the optimum grid configuration that meets our changing societal priorities, given our technology options today and in the future. Evolving power electronics, the diverse nature of enduse devices, the increasing availability of storage, and the need to control renewable sources locally and optimize across F+Ecs together suggest that a multitiered paradigm is both achievable and beneficial, with electricity integrated with other energy carriers in local systems. A viable framework must be established as the projected investment in electricity infrastructure in the next 25 years is projected by the International Energy Agency to be US$17 trillion or more, and poor investments could be very costly in terms of our sustainability, PQ+R, and cost goals.