July 1, 2009

The Odd Couple: Renewables and Transmission

Martin Piszczalski, PhD

Wind and Solar Generation Are Intermittent

Wind and solar farms produce power intermittently due to weather changes and time of the day and season. For either technology, the nameplate power can be produced only over about one-third of the daily hours. Stated another way, a plant’s potential annual capacity factor is typically around 33%.

Some opponents of wind projects take an overly simplistic approach and state that any utility that has renewable energy sources must provision three times the number of wind/solar megawatts and claim that that overhead produces the equivalent baseload power. Unfortunately, simply scaling up wind or solar power in this manner does resolve the delivery mismatch to the baseload demand that is actually needed.

Someplace in the delivery chain this intermittency of energy production versus load demand must be smoothed out. LSEs traditionally have taken on this burden themselves. Typically, an LSE backfills wind/solar gaps with natural gas – fired plants to make up for any shortfall in energy production based on a number of factors, including the season, weather, and the region’s operating experience. Using the same approach with very remote wind and solar farms isn’t as straightforward. To do so would make the entire long-distance energy delivery chain, in effect, run intermittently — if the remediating, balancing measures are not applied.

A more recent procurement practice is for the LSE to insist that the renewable producer directly supply steady, baseload-style power. In particular the LSE expects the renewable power producer to have its own storage or natural gas backup. An example would be Xcel Energy’s April 2009 request for proposal for 600 MW of solar thermal that is "fortified" in this way.

It’s All About the Dispatch

Energy researchers have been seeking the holy grail: a technology that transforms intermittent forms of energy production into the same sort of firm, baseload capacity we now enjoy from coal-fired and nuclear power plants. Many have proposed the standard list of energy storage options, such as compressed air energy storage, pumped hydro, stored heat or ice storage, batteries, flywheels, and the like. None of these alternatives has been proven in a utility-scale energy storage facility, so their use remains hypothetical.

The ultimate grid would accept power generated from any type of plant, especially widely dispersed wind or solar farms that have complimentary operational patterns. This grid would also serve to "pool" the many disparate, nondispatchable renewable plants so that they would appear to the grid as a reasonably predictable, virtually dispatchable, baseload energy – generating "plant." Nature, in effect, would do the energy balancing. This approach assumes an extensible and far-reaching transmission grid that is all but invisible to the energy generator but that has sufficient capacity to absorb all projected future renewable power sources.

Developing this renewable energy transmission superhighway is sure to require a legislative "push" to mature the concept into steel, concrete, and wires. Such a radical transformation of the transmission grid would allow resources planners to move past the antiquated concept of a market "pull" for traditional baseload power, because supply and demand would be average over large numbers of plants, especially the predicted plethora of small renewable projects located in every corner of the country.

Today, building renewable plants is not the problem. The principal problem facing developers is economically connecting those plants with the grid to get the power to market. New transmission planning must encourage and sustain the renewable power renaissance rather than be the cause of project delay and deferral, as it is today. The transmission planning now under way in the Western Interconnection, and the new transmission lines recently awarded by ERCOT, are excellent examples of rigorous regional planning. The next step: Interconnect each of the regions to form the ultimate grid.

Questions Awaiting Answers

The electricity industry is now facing up to several very important decisions that demand answers now rather than later. Will it be necessary to have almost the entire fossil fuel fleet dispatchable to fill the gaps in renewable power production? Will the U.S. need to move to a French-style infrastructure: highly centralized operations that are regulated at the national level? Should the federal government assume complete responsibility for siting new transmission corridors?

Some have even questioned whether the federal government should be picking winners and losers by specifically allocating capacity on interstate transmission lines or whether the government should consider direct investment in what has been a market-driven business if private investors are not available.

Answers to these questions must be forthcoming, as they will direct the overhaul of the country’s power delivery system, change today’s commercial practices, and streamline regulatory oversight of future transmission infrastructure projects.

—Martin Piszczalski, PhD (martinp@ic.net) is an industry analyst with Sextant Research. He works with renewable power developers, governments, and multi-lateral agencies to develop renewable power markets, especially for geothermal energy. For the past year he was in the Western Renewable Energy Zones study group of the Western Governors’ Association.