While many nations, states, and utilities are working hard to increase renewable energy production, managing these resources is a challenge. In particular, when it comes to managing wind energy, you really can have too much of a good thing.
This week the World Wind Energy Association issued its 2011 half-year report, saying the world market “regained momentum after a weak year in 2010… This capacity can cover almost 3% of the electricity demand all over the world.”
Though a small absolute number, this 3% is already too much — creating operational and financial challenges for the grid in Texas, the Pacific Northwest, Germany, and elsewhere.
Fortunately the smart grid offers one potential (although partial) solution.
The trouble with wind power
Wind is a wonderful resource: It has no fuel cost, operating costs are minimal (mostly maintenance) and it has zero air emissions.
Location is one of wind power’s main disadvantages. Wind farms tend to be far away from population centers, so existing transmission lines often quickly reach capacity quickly. And it’s expensive to build new transmission lines — especially given the challenges in obtaining rights-of-way.
The smart grid can help power companies solve the location problem by enabling techniques such as dynamic line rating which can push more electrons through existing lines, effectively increasing transmission capacity.
Intermittency is another problem. The grid has limited storage capability, which can make it hard for grid operators to accept wind energy when nature provides it.
Hydro pumped storage is one good way to store extra energy. This means using off-peak wind power to pump water uphill, then letting the water flow downhill during peak hours to spin turbines. The downside is that it requires two reservoirs, and it can be tough on shoreline environments. In any case, potential sites for this strategy are very limited.
Other grid-scale storage strategies remain cost-prohibitive. However, researchers are hopeful that over time the cost of grid-scale batteries and other storage technologies may drop.
But for now, the lack of grid-scale storage means that when there is too much wind energy for the transmission grid to handle, or when there is no buyer in the market, grid operators order wind producers to “curtail” production — stop the turbines.
In Texas last year these curtailments led to an estimated $57 million in generation losses, according to PBT Consulting. Curtailments in that state grew by 182% compared to 2009. Meanwhile, Texas keeps building more wind generation.
Wind curtailments have additional costs — especially negative prices in wholesale power markets. Other generators usually end up paying this cost, through depressed prices for their production. Sometimes, generators operating nuclear, gas, or other plants actually pay other generators to shut down, since ultimately that’s cheaper than ramping down their own plants. In 2010, Texas wholesale power prices went negative 17% of the time.
West Texas clearing market prices for 2010. Click to enlarge.
How the smart grid can help
There’s a huge potential source of grid-scale energy storage: existing building thermal mass. Smart grid technologies can make this feasible to implement.
By pre-cooling in summer and pre-heating in winter, homes and businesses can shift significant amounts of load — thereby using some of the excess wind power available. One study reported that “up to 51% of the total cooling load could be shifted to off-peak hours through optimal control.”
Here’s what’s needed to turn existing buildings into a grid-scale energy storage system:
- Time-varying prices. This gives consumers a direct financial incentive to shift their loads. Of course, these should always be voluntary.
- Detailed energy information. Smart meters can supply this in real time via the home area network interface, and online via the web and smart phones (“backhauled” data). Consumers can use this data to understand how and when they use energy, and to decide how to save energy or shift when they use it. Recently California issued rules for how consumers can gain access to their data, while keeping it private and secure.
- Automated response. Smart thermostats are the key here for grid-scale energy storage. These devices are now widely available (for example, about $90 at Amazon.com). Customers want to “set and forget” their devices to shift load and save money automatically.
The smart grid combines and capitalizes on all of these elements to make energy storage work as a system across the grid.
Beyond their thermal mass, buildings offer other opportunities for grid-scale energy storage — especially electric water heaters, plug-in electric vehicles, and ice storage systems. We’ll be covering these technologies more in the future.
The smart grid will make it possible to capture more benefits from wind power — and greatly reduce the problems that too many turbines currently can create.