Get used to the tail wagging the dog.
Until a few years ago, renewable energy resources were like a small tail on a big dog–utility owned and operated fossil-fueled generation. With their increased penetration in many parts of the world, the tail has grown big relative to the dog. In a few cases, the tail is now wagging the dog, rather than the other way around. The trend can only grow over time with important implications for both the dog and the tail. It is already happening in certain places and during certain times. With passage of time, it will become more commonplace, and troublesome.
In June 2010, and again in 2011, the Pacific Northwest has been blessed with unusually high hydro runoff simultaneous with extremely gusty winds during a period of tepid power consumption. The result: too much renewable generation and not enough load. Similar patterns can be expected elsewhere as more renewable resources feed the grid when there is little demand on the network.
BPA resorted to giving power away for free to whoever would take it.
The Bonneville Power Administration (BPA), among the largest of US federal power agencies, which operates massive hydro resources of the Columbia River Basin, could have spilled water over the reservoirs, but due to environmental restrictions could not do so. It shut down all its own fossil-fueled plants and even reduced the output of the region’s sole nuclear plant by 78% – but there was still too much power and not enough demand.
Some 2,000 MW of newly installed wind turbines, twice the load of city of Seattle, were spinning in strong gusts, just as their owners had hoped. At the height of the crisis, the entire BPA system was virtually running on renewable generation, hydro and wind. It was not a pretty picture as any experienced system operator would tell you.
BPA resorted to giving power away for free to whoever would take it, but due to transmission constraints, there was only so much that could be exported out of the region. As a last resort, BPA was forced to shut down fossil and wind generators feeding the network, offering to provide them with free electricity for what they would have generated in the absence of the crisis.
Thermal generators generally welcomed the offer. They could save the fuel cost, and would get free replacement electricity from the BPA. But the wind generators did not like what was being offered since there are no fuel cost savings while they would have to forego the federal production tax credits (PTCs) and state renewable energy credits (RECs), which only apply when the turbines are actually spinning.
BPA’s largess in offering “free” replacement energy was not appreciated. In all, the shutdown resulted in an estimated loss of 100,000 MWhrs of wind generation with significant financial implications for the privately-owned wind farms. They filed a complaint with the Federal Energy Regulatory Commission (FERC) claiming, among other things, discrimination in wholesale markets. There have also been multiple filings at the courts. It will take a while to sort things out.
The experience of the past two years has prompted BPA to plan for a repeat of the same in the years to come. One option may be to pay others to take some of the unwanted power off the grid. But that may conflict with BPA’s charter, just as spilling water over the dams run into environmental restrictions.
BPA now thinks that one way to get rid of the unwanted energy at times of low demand is to pay consumers to use more energy during such emergencies. As reported in New York Times (Nov 5, 2011) it has been experimenting with devices that could absorb large amounts of energy, such as space heaters and water heaters.
A 100-gallon water heater can store 26 kWhrs of electricity, a large ceramic space heater as much as 40 kWhrs. The stored energy can be used later on. BPA has installed a number of special devices at homes of volunteers allowing the excess energy to be absorbed during critical periods such as those it has recently encountered. It will need thousands more if the scheme is to make a dent. Getting rid of, say, 100,000 MWhrs of electricity in a hurry is not going to be easy.
Having a large number of electric vehicles would be one way to go since EV batteries can soak up a lot of juice and use it in lieu of petrol later on to deliver transportation at virtually zero cost and – in this case – zero carbon emissions. In fact, for a desperate utility like the BPA, it will probably make commercial sense to pay consumers to charge their EVs, hot water heaters, space heaters and whatever else they have during emergencies.
Utilities around the world have to get used to the idea that having large amounts of renewable capacity on the network comes with unexpected and occasionally unpleasant side effects.
It is ironic that, while most utilities are working hard to encourage consumers to use less during peak demand hours, BPA is struggling to encourage customers to use more, so it can get rid of the excess generation on its constrained network. It is all about timing.
A recent book, Smart Grid: Integrating Renewable, Distributed, and Efficient Energy, edited by Sioshansi, explores the many dimensions of the smart grid . With contributions from a number of prominent experts, scholars and practitioners with different perspectives, the book provides a broad coverage of the what, how, when, why and other facets of the smart grid.