Taming unruly wind power
ENERGY
Utilities in the Pacific Northwest have recruited consumers to draw in excess electricity from the grid, save it in a basement water heater or a space heater, writes Matthew L Wald
For decades, electric companies have swung into emergency mode when demand soars on blistering hot days, appealing to households to use less power. But with the rise of wind energy, utilities in the Pacific Northwest are sometimes dealing with the opposite:
moments when there is too much electricity for the grid to soak up. In a novel pilot project, they have recruited consumers to draw in excess electricity when that happens, storing it in a basement water heater or a space heater outfitted by the utility.
The effort is rooted in some brushes with danger. In June 2010, for example, a violent storm in the Northwest caused a simultaneous surge in wind power and in traditional hydropower, creating an oversupply that threatened to overwhelm the grid and cause a blackout. As a result, the Bonneville Power Administration, the wholesale supplier to a broad swath of the region, turned this year to a strategy common to regions with hot summers: adjusting volunteers’ home appliances by remote control to balance supply and demand.
Soaking up extra power
When excess supply threatens Bonneville’s grid, an operator in a control room hundreds of miles away will now dial up a volunteer’s water heater, raising the thermostat by 60 more degrees. Ceramic bricks in a nearby electric space heater can be warmed to hundreds of degrees. The devices then function as thermal batteries, capable of giving back the energy when it is needed. Microchips run both systems, ensuring that tap water and room temperatures in the home hardly vary. “It’s a little bit of that Big Brother control, almost,” said Theresa Rothweiler, a teacher’s aide in the Port Angeles, Wash., school system who nonetheless signed up for the programme with her husband, Bruce, a teacher.
She said she had been intrigued by an ad that Bonneville placed in the local paper that asked consumers to help enable the grid to absorb more renewable energy, especially wind. “We’re always looking at ways to save energy, or be more efficient or green, however you want to put it,” said Rothweiler, who worries about leaving the planet a livable place for her 21-year-old daughter, Gretchen. Bonneville paid for the special technology, which runs around $1,000 per home. The initial goal of Bonneville’s pilot programme is to gain experience in charging and “discharging” the water heaters and space heaters to see how much response operators can count on as the use of these thermal batteries expands.
Mark K Lauby, director of reliability assessment at the North American Electric Reliability Corp., which enforces standards on the grid, said that such storage innovations would be “the holy grail” as there is a shift to greater reliance on renewable energy. While the threat of excess supply is most severe in the Pacific Northwest, other regions may land in the same situation in coming years because a surplus would threaten to destabilise the electric system as much as a shortage.
Stress on renewable sources
California, for example, is committed to getting a third of its electricity from renewable sources by 2020. That would be harder if it had to turn off the wind machines on their best generating days to prevent the grid from being overwhelmed.
While the wind turbines produce electricity far below their capacity most hours of the year, they get busy when a storm rolls through, which is when river flows are highest, too.The agency can simply shut down the wind machines, and it did so intermittently this summer when excess power threatened the grid. But that angered the wind operators, who earn money from the electricity they sell and from tax and other credits based on their production.
For Bonneville, the full dangers of excess supply first hit home during the June 2010 emergency, when a severe storm whipped through the region. The transmission network had so much power that the agency turned off all its fossil fuel generation, gave electricity away to neighbouring networks and even told the system’s only nuclear plant to slash its production by 78 per cent, a highly unusual step. The region squeaked through, but the agency was stretching its resources “to their limits,” said Doug Johnson, a spokesman for Bonneville. At one point, the system was running almost entirely on renewable energy.
Bonneville began advertising for volunteers to accept extra electricity, mainly homeowners with electric heat and with water heaters of recent vintage. Plumbers install a mixing valve on the water heaters to keep the faucet temperature safe, and new wiring and a small computer keep track of energy flows. The agency says that some 200 homes will soon have the adapted water heaters, space heaters or both.
For the time being, the storage devices collectively can absorb the output of only a handful of wind turbines.
A 100-gallon home water heater can store about 26 kilowatt-hours, or about a day’s worth of electricity for a typical house, or less if the house relies on electricity for heat. The ceramic bricks in the space heater can store 40 kilowatt-hours, or more in some larger configurations. The heat can be drawn off by passing air and delivered to living spaces by a fan, with the bricks also functioning as a thermal battery.
