New solutions to managing the power grid for wind
Most readers of this column will likely know that wind generation is among the greatest clean energy success stories. Growth in wind energy has been nothing less than phenomenal. In fact, Northwest annual wind energy production now averages about twice that of the iconic Bonneville Dam. While wind still supplies only a few percent of the total electric energy demand, more is on the way.
Efficiently and economically managing higher levels of wind requires changes in how power systems manage the greater variability that comes with wind. Better managing wind power variability is uncannily similar to what was done to accommodate hydro variability. Just as power systems across the Northwest and British Columbia entered into cooperative agreements to trade power to manage drought and flood conditions, utilities today are coming together again to more effectively manage wind variability.
One example of the new level of cooperation involves opening and automating sub-hourly trading. Today each utility is essentially on its own to meet demand through each hour. More frequent trading allows greater sharing of resources and needs within the hour, allowing the least expensive resources available to supply the needs. While such markets are common in other regions of the country and abroad, they are new to the Northwest. Utilities are also working to make better use of available transmission lines, which current business practices often leave under-utilized. A great leap forward will occur once these two initiatives better connect Northwest utilities to the vast California power system. Yet, even with all this activity, more can be done to lower the costs of bringing more renewable energy onto the grid.
A key to managing variability is energy storage. One way to think about the above mentioned initiatives is that they open up access to existing storage capability in the vast Northwest hydro system, natural gas fields and pipelines, and in coal piles across the west. In addition to implementing cooperative strategies, many power planners are considering increasing storage capability. Although many technologies show promise, most are relatively expensive. The most promising technology may in fact be found in our own basements and garages. Electric water heaters prevalent in the Northwest may well provide the most cost effective storage capability available today, and new pilot projects are beginning to tap them.
Around the region, electric water heaters consume about four times the output of Bonneville Dam. Most water heaters operate in a temperature range of 110F-120F and can be selectively energized or de-energized providing about one kilowatt-hour of storage capability without noticeably affecting end-users. A comparably sized lithium ion battery would cost more than $4,000, have a more limited lifetime, and higher energy losses.
Not only does water heater storage have great value-- the cost is largely already paid by the end-user. Making the storage available to the utility entails relatively modest costs to install control and communication equipment. Commercially available technology costs well under $1,000 per installation with targets as low as $250. Specially built water heaters multiply the effective storage capability even further by incorporating mixing valves that allow units to operate over greater temperature ranges while maintaining constant water temperatures to the home.
Buildings represent another source of relatively inexpensive energy storage. Heating and cooling systems can be operated within acceptable ranges while supplying power system balancing services—potentially at much lower costs than smaller residential water heating loads.
The Bonneville Power Administration has entered into agreements with several of its customers to further explore technologies to tap customer loads to help it balance the power system. One of those customers is the Eugene Water and Electric Board. The new pilot project is not the first of its kind (pdf)-- using homeowner and business demand to help balance the power system has been demonstrated before. What is new this time is that utilities better understand the value of these services as they calculate the cost of managing wind and examine the alternatives.
Historically, power generators such as hydro and natural gas-fueled power plants have been called on to balance the variations in customer load. In a future dominated by wind generation, this will be turned upside down. In preparing for their country’s goal of operating on 50 percent wind power, Danish researchers plan to control demand to help balance the power system. BPA and other utilities are beginning to explore these possibilities here. If you are interested in contributing to a sustainable future, you can encourage your utility to consider participating in such programs. Realizing a clean energy future means exploring new strategies, technologies and grid efficiencies, and it is clear that we will all have a role to play.
Ken Dragoon is Research Director at Renewable Northwest Project, where heworks on power system wind integration issues, analytical support for utility resource plans and on the implementation of renewable energy portfolio standards. He previously worked at PacifiCorp for nine years and with Bonneville Power Administration for nearly fifteen. He recently wrote a book entitled Valuing Wind Generation on Integrated Power Systems and collaborates with energy experts around the world.