Strengthening Swiss hydropower with science

Researchers at ETH Zurich led by Robert Boes are growing particular options to optimize electrical energy manufacturing from Swiss hydropower vegetation. This may be sure that hydropower stays the spine of Switzerland’s electrical energy provide sooner or later.

“Though Swiss hydropower is a confirmed expertise, we should consistently work on optimizing it. If we do not, electricity production and storage at current vegetation will slowly erode,” explains Boes, who has headed the Laboratory of Hydraulics, Hydrology and Glaciology at ETH Zurich since 2009. It is because reservoirs particularly have a pure tendency to shrink on account of rubble and gravel. And sediment within the waterways inevitably results in put on and tear on the generators over time.

ETH Zurich researchers have spent a number of years tackling these and different challenges of their analysis: They’ve developed options for environment friendly water administration, calculated upkeep methods for generators and proven which places have the potential for making the best and eco-friendly use of hydropower. That is how they’re making certain that hydropower stays the spine of Switzerland’s electrical energy provide sooner or later—particularly in winter, when photovoltaic methods generate much less energy.

Higher water administration for run-of-river energy vegetation

There are 11 run-of-river energy vegetation alongside the 36 kilometers that the River Limmat flows from Lake Zurich till it meets the River Aare. Lake Zurich resembles a big head reservoir via which water is drained into the Limmat. The authorities use the weir system at Zurich’s Platzspitz park to manage the extent of Lake Zurich and thus additionally how a lot water flows into the river. Apart from enjoying a task in flood safety, navigation and ecology, this water degree is especially related for electrical energy manufacturing.

Boes and his analysis group not too long ago confirmed in a examine that optimized weir regulation at Platzspitz might permit about 2% extra electrical energy to be generated within the energy vegetation alongside the Limmat. This enhance in effectivity would come up from a brand new administration technique that, first, permits lake water ranges to be greater below right now’s rules and, second, makes use of weather models to raised modify water degree regulation in Lake Zurich to anticipated precipitation and influx volumes.

As a normal rule, the extra evenly the water flows into run-of-river energy vegetation, the extra electrical energy they’ll produce. Particularly within the case of small and medium ranges of excessive water, the brand new rules would make higher use of the extra water current.

“If the weather model predicts heavy rain, the smart weir system would release a little more water into the Limmat ahead of time. Then, when the predicted rain arrives, the lake would have more of a buffer and could continue to release water evenly into the Limmat despite the heavy rainfall,” Boes explains.

This may stop the generators from being overloaded by an excessive amount of water. In fact, water managers would nonetheless need to adjust to high-water rules in addition to ecological and different necessities.

Related diversifications would even be doable on different rivers on the Swiss Plateau downstream of Alpine lakes. Boes and his group have calculated that electrical energy manufacturing from run-of-river energy vegetation may very well be elevated by round 100 gigawatt hours per yr if weir methods have been managed extra intelligently. This may be sufficient to satisfy the annual electrical energy wants of about 25,000 four-person households.

Defending generators extra successfully towards sediment

The tremendous silt that rivers carry is the pure enemy of each hydropower turbine. It acts like sandpaper, inflicting generators to wear down over time and generate considerably much less electrical energy. Though this drawback has been identified for a very long time, it has nonetheless not been totally resolved. Whereas many energy vegetation characteristic what are often called sand traps, these typically fail to take away sufficient of the tiny particles from the water.

To extend the sand traps’ effectiveness, and thus defend the generators and keep away from manufacturing losses, Boes and his group investigated which forms of entice are notably efficient: “Long traps with a gentle bottom gradient, which make the water flow as slowly as possible, work best. They let the particles settle more easily to the floor,” Boes says.

These findings have already been used to enhance the sand entice on the Susasca hydropower plant in Graubünden. Nevertheless, longer traps additionally require extra constructing supplies and take up extra space, making them costly. In consequence, choices on which structural diversifications make financial and technical sense will differ from energy plant to energy plant.

Boulder bypasses for reservoirs

Climate-related erosion causes stones, gravel and different sediments to enter reservoirs by way of their water consumption and scale back their storage quantity. This drawback, often called sedimentation, might scale back the storage capability of Swiss reservoirs by about 7% by 2050.

As we speak, small and medium-sized reservoirs use bypass tunnels as a structural measure towards sedimentation. These tunnels information stones, gravel and silt previous the dam wall throughout floods. Nevertheless, since floodwaters carry quite a lot of sediment, the ground of the bypass tunnel is usually topic to pronounced put on.

Boes and his group have repeatedly regarded into this drawback lately. For instance, the researchers investigated which supplies are finest suited to lining the ground of such tunnels. After numerous exams, they got here to the conclusion that high-strength granite is finest in a position to face up to the heavy put on and tear in notably harsh situations. Based mostly on this realization, a number of bypass tunnels around the globe have since been lined with granite.

Utilizing the Solis reservoir in Graubünden for instance, the researchers have been additionally in a position to show how efficient bypass tunnels really are. The tunnel has diminished annual sedimentation in Solis by greater than 80%. Nevertheless, this requires changes to storage administration.

The facility plant’s operators can additional enhance the tunnel’s effectiveness by bringing the water degree within the reservoir down low sufficient, as this permits the inflowing river to move notably giant portions of rock and sediment and discharge them by way of the tunnel. These findings are additionally related for the operators of quite a few different energy vegetation.

Extra electrical energy via optimized turbine upkeep

One other strategy to take care of the buildup of silt in reservoirs is to channel tremendous sediments into downstream sections of the river by way of the headrace and generators. “The problem with this is that it causes more turbine wear. But it can still be a worthwhile measure for Alpine reservoirs if alternative measures, such as bypass tunnels, would be too expensive or not feasible,” Boes says.

Nevertheless, to raised assess the feasibility of this strategy to the issue of sedimentation, energy plant operators have to know what harm the silt causes to the generators and the way a lot it reduces their effectivity. Boes and his group analyzed this drawback in a single hydropower plant in Valais and one other in Graubünden.

The researchers used their findings to develop a mannequin that predicts when a turbine will lose output on account of sediment put on and ought to get replaced. This permits energy plant operators to optimize the upkeep of their methods and in the end produce extra electrical energy.

The potential of Swiss hydropower

Along with these particular options for current hydropower vegetation, Boes and his group at ETH Zurich have additionally been conducting in-depth analysis lately into the potential for increasing Swiss hydropower. For instance, his analysis group have investigated which areas of glacial retreat can be best suited for brand new reservoirs and which current dams is perhaps raised to create extra storage quantity.

In 2020, the Swiss Federal Workplace of Power used the outcomes of those ETH research on appropriate websites as the premise for a roundtable dialogue at which electrical energy firms, environmental safety organizations and cantons agreed on an inventory of 15 hydropower plant enlargement and new building tasks.

Appearing as facilitator between the events, ETH Professor Emeritus Michael Ambühl additionally performed a component in serving to the events attain a compromise. These tasks have been subsequently integrated into a brand new Electrical energy Provide Act. Whether or not this laws comes into drive in the end is determined by the Swiss voters, which can vote in June on the enlargement of hydropower and different renewable power sources.