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Wind, Sun And Water: An Old Source Of Renewable Energy Finds Its Place In The Sun

July 26, 2019
The bulk of the electricity generated in the United States still comes from fossil fuels, but the times are changing. In April this year, the country generated more power from renewable sources than from coal for the first time ever. Amid the excitement over rocketing solar and wind power production, it is easy to forget the quiet, reliable stalwart in the renewables pack: hydropower. The country’s hydropower plants have generated 250-300 terawatt-hours of carbon-free power for the country every year over the last decade.
But the numbers do not tell the whole story, because the country’s hydropower plants are adjusting to a whole new way of working. They are no longer switched on all day and night, churning out baseload power. Instead, hydropower plants are learning to join and depart the grid at the whim of the elements, which places new demands on the facilities in terms of flexibility, reliability and sustainability. The U.S. also has some of the world’s oldest hydropower plants, which means that modernization has become a priority.

One man who relishes the challenge is Pierre Marx, the general manager for GE Renewable Energy’s hydropower business in North America. Marx, who is in Oregon for the Hydrovision International, the U.S.' largest gathering of hydro professionals, led GE Reports through the new landscape. He also explained why he needs to spend plenty of time thinking about ducks and salmon. Here’s an edited version of our conversation.

 width= Top image: A massive pumped hydro power plant in Linthal, Switzerland, is using GE generators. Image credit: GE Reports. Above: Image credit: Getty Images.

GE Reports: Why do we need to be talking about hydropower now?

PM: The growth of fast-growing renewables such as wind and solar has changed hydropower from being a baseload generation to a load-following generation. Operators use to start and stop their plants once or twice per month, but they now need to do so twice per day. That is the case in the western states in the U.S., where the increasing penetration of solar and wind in California has turned hydropower facilities in Washington and Oregon into load-following generators.

GER: Load-following? What do you mean by that?

PM: OK, so let’s take California, which has a very high penetration of solar energy in its generation mix, but is also supplied by hydropower plants in Washington and Oregon. The sun rises in the morning and pushes solar power’s share of the mix up to 30%. But at sunset, you suddenly lose all of that power. Those conditions create the state’s famous ‘duck curve’, because the load curve looks like the profile of a duck. Hydropower needs to step up — once in the morning before the sun rises and at then again at sunset — when those solar power slumps occur. Ramping hydropower generation up and down to meet demand puts a huge strain on those assets, which challenges their reliability and flexibility. This challenge arrives against a backdrop of an aging hydropower fleet — the average age of the U.S. fleet is over 60 years — and stricter environmental regulation.

GER: So how could you deal with these duck curves?

PM: Well, hydropower pumped storage facilities are one solution because they can provide a grid with a reserve of energy that it can call on at any time for extra flexibility. But we are also working to improve the management of hydropower assets with digital solutions. For example, we are gathering and analyzing data about every aspect of a hydropower plant which allows us to reduce planned and unplanned outages or predict how that machine is going to operate for example.

GER: Could you give an example of how gathering data helps?

PM: Let’s take the example of unplanned outages. An analysis of mountains of data about pressure, temperature or turbulence might be able to predict an unplanned outage, or tell an operator that they don’t necessarily have to stop their turbines for unneeded maintenance. In both cases, the operator minimizes downtime, winning them several more generation hours that boosts their wholesale power revenues. It’s a game changer.

GER: We hear that GE Renewable Energy has also been working on some other new features?

PM: That’s right. We’re building fish-friendly hydropower turbines that prevent the injury and death of migratory fish caused by either passage through the turbines. That’s in response to U.S. regulation on hydropower plants, which stipulates that 98% of fish must survive the passage through a turbine.

GER: Fish-friendly turbines? How does that work?

PM: Well, when fish pass through run-of-river hydropower plants, they can get buffeted around by the turbine blades. That can stun them, leaving them vulnerable to predators, such as birds. So we are designing special turbine runner blades that reduce the blade strikes on fish that pass through the McNary Dam on the Columbia River on the Oregon-Washington border, where we are carrying out a huge modernization program after being awarded the contract by the U.S. Army Corps of Engineers and have received recently the notice to proceed. The runner blades have been designed according to the shape and size of the fish, which in this case, are young salmon. The goal is to significantly boost the fish survival rate at the McNary Dam while ensuring the excellent performance and efficiency of the plant. The McNary project is a significant contract for us — because of the size and length of the contract (14 units over approximately 14 years). It highlights our proven expertise and competitiveness in the hydropower rehabilitation business and our dedication to provide environment-friendly technologies to our customers.

GER: Could you explain the dissolved oxygen problem?

PM: There are also strict rules in the U.S. about minimum dissolved oxygen levels in the water passing through a hydropower plant. Oxygen-rich water ensures a favorable habitat for fish and other aquatic life. But the water that is diverted through a hydropower plant can be hypoxic, or low in oxygen levels. That’s because the deeper you go, the less aeration there is. That deeper water is also the water that travels through the hydro turbines, meaning that there is a risk of oxygen-depleted water being released downstream, and impacting an entire river.

GER: So what’s the solution there?

PM: We are using innovative technology, such as specially shaped interblade profiles that are easy to integrate into the runner blade design. That ensures that more oxygen bubbles into the water. We know that the smaller the bubbles, the better the transfer of oxygen into the water, and that’s what our technology achieves. Cube Hydro is already using that technology in its High Rock facility in North Carolina.

GER: And have you had good results?

PM: Yes. Early results suggest they have boosted both the efficiency of the plant and the oxygen levels of the water. The project is exceeding expectations, injecting significant levels of oxygen with just one of the three turbines using the technology. We've already sold the technology to one other customer and we're getting good feedback from other customers that these initial positive results are encouraging for the Industry. It’s great news for the fish because maintaining a high level of oxygen means good living conditions for all aquatic wildlife. But it also means that our customers can operate plants that are technically efficient and environmentally friendly.