Published on August 18th, 2015 | by Tina Casey24
Squeezing Every Last Drop Of Juice From Hydropower, In Switzerland
August 18th, 2015 by Tina Casey
Hydropower is a relatively simple system when applied directly to rivers, but throw in a couple of extra lakes and reservoirs and the options increase dramatically. One of Switzerland’s leading energy companies, the KWO, operates just such a complex hydropower system in the country’s Grimsel Pass, and it’s facing some interesting changes with the addition of wind and solar energy to the grid mix — and the forthcoming loss of nuclear generating capacity in Switzerland, too.
The KWO Hydropower System
CleanTechnica is on a technology tour of Switzerland this week thanks to Presence Switzerland and swissnex, and they sent us on a quick 2.5 kilometer drive down a granite tunnel to the bowels of the KWO’s largest power plant, Grimsel 2, where we got the inside scoop from Gian Marco Maier, Head of Operations (KWO is short for Kraftwerke Oberhasli btw).
As a side note, the KWO is all over electric mobility (Maier himself drives an e-Golf company car), but our ride was a conventional shuttle bus. According to Maier, several years ago the KWO introduced an electric bus into the Grimsel 2 works, but the damp conditions and chill air underground were not particularly friendly to the battery, and the pilot project was dropped.
However, other forms of alternative transportation are quite popular underground, namely, bicycles (these are just two of the many bikes parked around the works):
Where were we? Oh, right Grimsel 2. Grimsel 2 is one of nine power plants operated by KWO in the dramatic Grimsel Pass. All together, the plants have a combined capacity of 1,125 megawatts, comprising 26 turbines that push out 2,350 gigawatt hours annually, or about 7 percent of the total hydropower output in Switzerland.
Grimsel 2 is the KWO’s newest and single biggest plant at a capacity of 348 megawatts. It has four integrated turbine-generator-pump units (we’ll explain the pump thing in a second), which you can see in the topmost photo.
Because each of the four units has both a turbine and a pump, a multiplicity of valves are involved for each unit (four to be exact), which you can see below in this partial shot of the valve room. The lake is behind the wall on the left, and the turbine room is behind the opposite wall:
If you’re thinking that all those turbines and generators and valves — and pumps– add up to a lot of maintenance, you would be right. The KWO employs several hundred people among its operations. Maintenance of the turbines and other parts of the system is performed on site with pinpoint attention to detail, by hand. In case you had any doubts about that, here is just one side of one of the tool racks we came across:
…and here is more evidence of the human touch, on this unit broken down for a touchup:
May You Live In Interesting Times, Hydropower Edition
As described by Maier, the KWO’s hydropower operations have been an important factor in achieving grid stability. Hydropower is ideal for that purpose because, unlike some other systems, it can be revved up (or down) in a matter of minutes as needed.
There’s more in store. With more wind and solar entering the grid, the number of changes called in to the system has been increasing. The new normal is about 40 to 50 changes per day, according to Maier.
While that may push maintenance costs upward, the complexity of the KWO system provides it with some unique benefits that could enable it to remain competitive into the future.
Part of the reason why Grimsel 2 plays such an important role in grid stability is that it pairs with a water battery, which is where the pumps come in. In the summer, when rain and runoff make the rivers run high, excess water is pumped uphill to Lake Oberaar for extra energy storage.
In winter, which is Switzerland’s “dry” period, the extra stored water flows by gravity back downhill to Lake Grimsel.
The pumps, of course, require energy to run, but that doesn’t come from the hydro plant. It comes from a grid mix that includes a heavy dose of nuclear energy, if not from Switzerland’s own plants (more on that in a second) then imported from France and elsewhere. That means the pumps normally run on off-peak hours, during nights and weekends.
The emergence of wind and solar into the grid is putting hydropower at a competitive disadvantage (considerations to local governments also push up hydro costs in Switzerland), but it does provide the KWO with more flexibility, providing the potential to run the pumps economically during peak hours as well as off peak.
Another boost for the system has recently come about, thanks to an accident of design. At Grimsel 2, Maier explained, a large maintenance area had been set aside when the dam and power plant were first constructed. For the past two years, that area has housed the world’s largest frequency converter, which does this:
The world’s largest frequency converter for the pumped storage power plant Grimsel 2 in Switzerland was supplied and commissioned by ABB. The 100 megavolt ampere (MVA) variable speed converter, fitted to the existing generator/motor set, now enables pumping with variable power and results in higher operating profitability. The installation, built on ABB’s PCS 8000 converter, sets a new benchmark in flexibility and efficiency of the hydro pumped storage power plant operation.
The KWO also anticipates adding another 250 megawatts (MW) of capacity to the system, which will bump its capacity up to a total of 1,400 MW from the current 1,125 MW. If you’re thinking the math doesn’t quite add up, it actually does, because the company expects to achieve a significant increase in efficiency (namely, a decrease in water friction) by doubling the duct system.
About Those Nukes…
Just yesterday we noted that Switzerland is phasing out its five nuclear power plants, which currently account for about 40% of the country’s generating capacity (the other 60% is hydropower, and a thin sliver of other renewables).
After the hydropower plant, we dropped by the Swiss Federal Office of Energy for an overview of the country’s Energy Strategy 2050, and were informed that for a variety of planned and unplanned reasons, not one of those five power plants is in operation (at least, they weren’t as of yesterday).
There hasn’t been a hitch in the grid, partly because of the country’s position as a transmission hub between France, Italy and Germany.