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Energy imbalance WTF?!

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Jonathan Thompson | Mar 08, 2013 10:30 AM

A few weeks ago, certain sectors of the environmental/renewable energy community got all fired up. We had reached a “major turning point” said one blogger. Another called the mid-February news a “milestone.”

So what was all the fuss about? Did we manage to pull some charismatic megafauna away from the brink of extinction? Or perhaps we figured out that coal combustion waste could be recycled into tasty and nutritious snack chips?

Arizona Grid Pic

Nope. The brouhaha was over an agreement between PacifiCorp, a giant utility that sells power to a big swath of the West, and the California Independent System Operator, which manages most of that state’s grid. The two announced in February that they will cooperate in an energy imbalance market.

That, my friend, was the milestone: an energy imbalance market. It’s not the sexiest sounding concept. But when it comes to integrating large amounts of renewable energy into the grid, an EIM truly is key.

One of the basic truths of the electrical grid is that the amount of power that generators put into the thing has to equal the amount that’s taken out. So, if all the lights, gadgets and air conditioners connected to a particular grid are collectively using 100 units of power per hour, then the grid operator needs to crank up his power plants to collectively generate that same 100 units of power. If that balance is lost, it can result in instability and blackouts. Across the Western grid, this balancing act is repeated in 38 different balancing areas. Though all interconnected, each balancing authority must keep its own portion of the grid in check.

When dealing with coal, nuclear and hydropower -- all of which put a fairly controlled, steady stream of power into the grid -- the balancing act is relatively simple (but still challenging). The grid operator does his best to predict the next day’s load curve (it might shoot up on a hot afternoon as everyone cranks their air conditioners, for example), and schedules his power plants to meet the curve. On an hour-by-hour basis, if the load and generation curves don’t meet up, the difference between the two is the imbalance. In order to cover potential imbalances, the grid operator keeps reserves on hand, like a natural gas power plant, that can be fired up to be generating electricity in a matter of minutes.

Throw a bunch of intermittent solar and wind power into the mix, and the balancing act becomes more challenging. Now, both sides of the scale, load and generation, can fluctuate. If a big cloud shades a solar plant, or a huge gust hits a wind farm (causing the turbines to shut down), the amount of juice going into the grid can plummet unexpectedly, throwing everything out of balance. Utilities, working a day in advance, will typically commit enough fossil-fueled reserve generators to cover a serious imbalance resulting from a consecutive drop -- however unlikely -- of all the intermittent renewables on the system. Among other things, that costs money, and gives old school utilities an excuse for staying mired in their fossil-fueled rut. As you can imagine, it also makes accurate weather forecasting that much more important.

Enter the energy imbalance market! Put rather simply, the PacifiCorp/Cal ISO deal will allow those two balancing authorities to cooperate more closely with one another to smooth out imbalances. They can share reserves, rather than each having their own. If a storm diminishes solar generation in California, then Cal ISO can buy some wind power from PacifiCorp’s Wyoming wind farms to balance it out -- spreading wind or solar out across geographic regions is probably the best defense against serious fluctuations. They will also operate on a real-time market, with 5 minute balancing periods, which is much more accommodating to the ups and downs of solar and wind than the current system.

Renewable energy advocates have long urged the creation of an imbalance market that preferably covers the entire Western grid. It will be difficult, they say, and costly, to integrate 20 or 30 or 80 percent of renewables into the current, balkanized system. Yet many utilities, burdened by that Western penchant for independence and happy with the status quo, aren’t interested. Still, others are: Xcel Energy, which has a whopping 4900 megawatts of wind power in a 17,000 megawatt system, has shown interest in engaging its neighbors in an EIM, and the Western Governors Association is on board. Perhaps this latest deal will push things along.

Photo of Arizona transmission lines by the author.

Jonathan Thompson is a senior editor at High Country News. Lately, he's been spending his time trying to understand the electrical grid.

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