By Chris Nelder | March 28, 2012
A persistent myth about the challenges of integrating renewable power into the grid is that because solar and wind are intermittent, grid operators need to maintain full generation capacity from “baseload” plants powered by coal and nuclear. Recent real-world data and research shows that not only is this not true, but that baseload capacity is fundamentally incompatible with renewables, and that as renewables provide a greater portion of the grid’s power, baseload generation will need to be phased out.
But before we get into the details, some background information is in order.
Types of power plants
“Baseload” power generators are typically large units that operate more or less continuously at 70 to 90 percent of their rated capacity, and do not shut down except for maintenance. These include nuclear, coal, and combined-cycle natural gas plants which capture and recycle the exhaust heat of traditional gas turbines. Coal and nuclear plants can take from one to three days to start up, and take a long time to shut down.
“Load-following” power generators can increase or reduce their output based upon demand, and typically run at 30 to 50 percent of capacity. They are typically traditional gas turbine units, and may be shut down on a daily or weekly basis as needed. Older coal plants, combined-cycle natural gas plants, and some nuclear plants can operate in a load-following mode, but their ability to do so is limited. For example, newer nuclear plants can cut output by as much as 20 percent in an hour, but need as much as eight hours to ramp back up to full capacity.
“Peaking units” typically run for a few hours at a time at low capacity factors when demand reaches unusually high peak levels, like in the middle of a hot summer day. These units are typically simple gas turbines.
The grid today
In the U.S., there are three main grids: one in the east, one in the west, and one in Texas. Some utilities are regulated while others are not, some are publicly owned while others are private, and although they are interconnected within the three main grids, they operate with a certain amount of autonomy. Grid power comes from about 5,800 utility-scale power plants, comprising some 18,000 generating units. A patchwork quilt of agencies with overlapping jurisdictions regulate the grid, including Federal Energy Regulatory Commission (FERC) and the North American Electricity Reliability Corporation (NERC) at the federal level, a range of Regional Transmission Operators (RTO) and Independent System Operators (ISO) at the regional level, and Public Utility Commissions (PUC) at the state level. Ten major RTOs and ISOs serve about two-thirds of consumers in the U.S. and more than half in Canada, with the remainder served by smaller regional operators.
The grid’s architecture developed in a fairly ad-hoc way. As the country was built up, more generation capacity was added, and the grid was extended. Technologically speaking, most of the grid is old and “dumb”: Power gets generated somewhere, and transmitted somewhere else, but there is very little in the way of sensors, storage buffers, switches, or security mechanisms along the way. It’s more like plumbing than an iPhone. This is why it was possible for one overloaded transmission line in Ohio take down much of the grid in Ontario, the Northeast and the Midwest in the blackout of August 14, 2003.
Grid operators have one overriding, fearsome task: They must maintain enough supply from this very complex system, within a narrow range of frequencies and voltages, to meet constantly fluctuating demand at all times. Therefore they tend to be risk-averse, preferring to stick with what they know to be reliable, and avoiding innovation.
Before the advent of renewables, generating power was a pretty straightforward task: When demand increased, you just added more fuel to an engine. With renewables, the task is reversed: The engines (wind turbines and solar collectors) ramp up and down of their own accord, and grid operators must adjust to accommodate their output.
The growth of renewables in the U.S. has been driven primarily by state Renewable Portfolio Standards (RPS) requiring a certain percentage of power to be generated from renewables by a certain date. According to an April 2011 MIT report just released this month, 29 states have RPS mandates which typically require 15 to 25 percent renewables by 2015 to 2025. Many of these states mandate that grid operators give the renewably-generated power priority, so when wind generation spikes, for example, they must ramp down other generating units. In other areas of the U.S. and in parts of Europe, operators may instead curtail peak production from renewables to accommodate their baseload generation—for example, forcing a wind farm operator to furl their blades or apply brakes to their turbines.
The baseload fallacy
The notion that renewables cannot provide baseload power is really an artifact of the way the grid and its regulators have evolved. If all generators were able to ramp up and down on demand, and if grid operators were able to predict reliably when and where the sun would be shining and the wind would be blowing, accommodating any amount of power from renewables would be no problem.
A 2010 study called “The Base Load Fallacy” by Australian researcher Dr. Mark Diesendorf, an expert on integrating wind into power grids, fingers the “operational inflexibility of base-load power stations” as the main obstacle to further integration of renewables. “The renewable electricity system could be just as reliable as the dirty, fossil-fuelled system that it replaces,” he observes, if demand were more efficient and intelligent, and supply were made up of a wide variety of renewable sources plus a small amount of gas-fired capacity to cover the peaks. The perpetrators of the baseload fallacy, he argues, are mainly the industries who benefit from the status quo: coal, oil and gas companies, the nuclear industry, power generators, and industries who depend on them like aluminum and cement manufacturers.
Claims that renewables could never generate more than a few percent of grid power without taking down the grid have been given the lie by the real-world experience of areas that deliberately adapted their grids.
The best example in the U.S. is Texas. By virtue of having its own grid (technically, an “interconnection”), it is generally outside the purview of federal regulation by FERC. The entire grid is operated by a single ISO, ERCOT, so it has a lot of control over its generation mix and grid planning. Texas decided long ago to pursue its wind potential vigorously, and now has the largest installed wind capacity in the States at over 10 gigawatts (GW).
On March 7, ERCOT used a record 7,599 MW of wind power, constituting 22 percent of the load and representing over 77 percent of its nameplate wind capacity. The previous day it had met 24 percent of the load with wind. Baseload proponents had said that such levels of integration were flatly impossible. But ERCOT had made it possible with the help of a new modeling tool that analyzes real-time conditions every half-hour, giving grid technicians greater ability to match generation with demand and control transmission more discretely. The National Renewable Energy Laboratory has found that if other grid operators adopted similar tools, over one third of U.S. power could be generated from renewables.
All that ERCOT needed to accommodate more wind power was some sensors, a better flow of information, and better modeling tools. As the MIT report notes, the hardware to provide better grid information already exists, but few operators have employed it in their control and dispatch operations. The obstacle is not technology, but “the industry’s culture of resistance to new and experimental projects.”
That’s not a problem for China, however. The MIT report mentions that China is piloting a program that will allow it to monitor the national grid in real-time and control it automatically. The system eventually could allow China’s grid to uptake a far greater percentage of renewably-generated power than the antiquated and obsolete U.S. grid can, although the former is still the world’s top consumer of coal for power generation.
Another 2010 study by the German Renewable Energies Agency turned conventional baseload logic on its head, finding that due to their relatively inflexible ability to adjust to changing demand, “nuclear power plants are incompatible with renewable energies.” To meet forecasted wind production in Germany, conventional baseload operation would be cut in half by 2020, assuming renewable generation continues to enjoy priority dispatch. As renewables gradually replace conventional baseload capacity, only more flexible gas generators that can operate at under 50 percent of their capacity will still have a role to play.
The European example
Europe serves as another model of why good grid planning and management are key to integrating renewables into the grid. If baseload proponents were correct, then we would expect the countries with the highest levels of renewable penetration to have the most trouble in managing their grids, but the reality is quite the opposite.
A comprehensive new report on renewables integration by European consultancy eclareon GmbH surveyed the policies and grid functions of the 27 member states of the European Union, and found that “large quantities [of renewable generation] can be effectively managed on the grid.” Countries that planned for adequate grid capacity generally didn’t have a problem with accommodating renewables, and unsurprisingly, those are the same countries that have pushed for more renewable generation.
Solar and wind generation as a percentage of electricity consumption in 27 European Union countries in 2010 (first bar) and 2020 (second bar). Grid integration designated by color: green = positive, yellow = neutral, red = negative. Source: RES Integration Final Report, eclareon GmbH.
Countries where the share of renewable power is greatest—Germany, Denmark, Spain, Ireland, and Portugal—offer “positive conditions for grid operations,” although some barriers to integration were identified, including the potential for curtailment in Germany, challenges to priority dispatching in Ireland, and strict distribution parameters in Portugal. Identified barriers for grid development in those countries revolve around public policy issues, permitting, regulatory regimes, cost distribution, and the obligation (or lack thereof) of grid operators to beef up their grids to accommodate more renewable power.
Ripe for innovation
The real issues around the integration of renewables into the grid have to do with human arrangements, not technology. As the MIT report concluded, “There is a clear need for a statement on national goals for the electricity sector to streamline the US regulatory structure, which currently is complex and fragmented.” We need smart policy, and an intelligent approach to planning the grid of the future that is not simply beholden to the vested interests of the status quo.
This will run directly at odds with the free-market ideologies that have brought us this far. As the EU project THINK observed, “the main shortcomings of the conventional regulatory framework are that grid companies have disincentives to innovate.” A firm regulatory hand, like that in the most renewably-powered countries of Europe, will be necessary to integrate more power from solar and wind onto the grid.
Renewables should be able to meet at least 20 percent of electricity demand without disrupting the grid just about anywhere in the world with good grid planning and management. As geothermal and marine power technologies mature, they will become a much less intermittent, natural substitute for the baseload technologies of the past. A host of other technologies will even out the bumps in renewable generation by adding storage (batteries for distributed storage, and pumped hydro and solar thermal for utility scale); increasing the connections between grids (allowing better transmission between sunny and cloudy, or windy and still areas); and transitioning to on-demand natural gas-fired peaking generators. Over the next decade, the current assumptions about the need for traditional baseload capacity will begin to fade as new storage, interconnection, and smart grid management strategies come into play, and ultimately, a combination of these technologies might raise the limit on renewables to 100 percent.
The attachment to our antiquated architecture of power generation and grid management is simply a failure of imagination and innovation. Those who benefit from its arrangement today hold it up in too-precious reverence, not unlike the those who, one hundred years ago, protested the banning of the ancient Chinese practice of foot-binding depicted in the photo at top. It may be beautiful to them, but to those with modern sensibilities, it’s an ugly, even grotesque fetish that should be consigned to the dust bin of history, and one that one hundred years from now will seem unbearably dumb, quaint, and cruel. The problem is not that the feet are too big; it’s that the shoes are too small.
Photo: Feet of Chinese woman, bound, compared with tea cup and American woman’s shoe, World War 1 era. (otisarchives/Flickr)