Idaho National Laboratory (INL), working with public power utility Idaho Falls Power, has completed a series of tests designed to assess how small hydropower plants can provide startup power during outages.
The city of Idaho Falls, Idaho, owns five, small run-of-river hydro plants on the Snake River that, combined, can provide enough power to meet about one-third of the city’s power needs.
After a December 2013 outage left 3,500 residents without power in subzero weather for hours, the public power utility began to explore options that would make the city’s power system more resilient in such an emergency.
Even though Idaho Falls has its own generating plants, they are all low head, low pressure hydro plants. “We assumed the plants would be able to start up on their own in an emergency, but assuming is not knowing,” Ben Jenkins, systems engineer at Idaho Falls Power, said.
In 2016, Idaho Falls and INL began investigating the ability of its generators to start up on their own, known as black start capability, and their ability to island or operate independently of the surrounding grid.
In December 2017, the utility tested its assumptions and found that as it started adding load to its generators, they would become unstable at about 30 or 35 percent of rated capacity. The test found the limits of the utility’s system. “There was plenty of water, but low head machines need the grid to keep them stable,” Jenkins said.
Idaho Falls Power began looking for ways to fix the problem and enlisted the aid of INL, which is based in Idaho Falls and is an Idaho Falls Power customer.
“The INL folks were looking at the larger picture, the larger grid, and we were looking at the local picture,” Jenkins said. “Our needs dovetailed nicely.”
For its part, INL tested the use of ultracapacitors, which can store and discharge large amounts of energy very quickly, to provide pseudo inertia to the generating plants.
The tests demonstrated that “small hydropower plants like Idaho Falls’, combined with integrated energy storage technologies, may prove to be as nimble as natural gas when it comes to load following,” Thomas Mosier, INL’s energy systems group lead, said in a statement.
Idaho Falls Power tested two operational changes. Working with equipment provider American Governor, the utility tested variations in the gates and blade pitch of its hydro plants to find the most efficient and stable configurations.
Idaho Falls Power also tried bringing multiple plants online simultaneously, running nine tests, each with different combinations of operating parameters. “In effect, we were simulating a large plant,” Jenkins said.
“The one big thing we learned, we didn’t even know we were looking for,” Jenkins said. “If all the load is on one plant, it is unstable, but if you bring them all up simultaneously, they overperformed. We got more out of the combined plants than out of each plant individually.”
“We were pleasantly surprised; operational control can make a huge difference,” Jenkins said. If Idaho Fall Power lost power from the grid, it could implement the operational changes and restart its generators and gradually add load and operate in islanded mode.
Operational changes can also be implemented with minimal costs.
The test results have also prompted Idaho Falls Power to look at another form of energy storage, batteries. They can provide “multiple values,” Jenkins said, citing their ability to provide services such as peak shaving in addition to providing generation stability.
Idaho Falls Power is in conversation with INL about batteries, Jenkins said, and, with battery prices coming down, they could become more attractive. “What was financially unattainable two years ago is now becoming viable,” he said. “There could be value we can look at.”
With the testing portion of the collaboration concluding, there is going to be a lot of evaluation of the next few months, Jenkins said. The data collected in the tests will be fed into INL’s digital real time simulators, which can offer insight into how grids will act and react under different conditions. Then, two reports will likely be generated, one simple and another more detailed.
“We are very happy with what we learned from this, and if the information can be used by other small utilities, all the better,” Jenkins said. “We feel we are part of a bigger involvement. It helps Idaho Falls, but it could have a much broader impact on the national grid.”