Europe's green battery

With all of its hydropower plants Norway wants to become a huge "green battery". Delta had a look inside a power plant that might one day store excess solar and wind energy from all parts of Europe.

After following the river Nidelven from the Norwegian city of Trondheim up into the mountains for 20 minutes, PhD student Peter Joachim Gogstad parks his car in front of two doors the size of an airplane hangar carved into a cliff. Behind these massive gates, a long windy asphalted road sways down towards a cave in the heart of the mountain. There, two of Norway's thousand treasures are hidden; a couple of hydropower turbines that together generate about 50 megawatts. They are operated by Norwegian state-owned hydropower company Statkraft.

We are on a press tour organised by the Norwegian University of Technology in Trondheim (NTNU) and SINTEF, an independent Scandinavian research institute. NTNU just received a grant from the Norwegian government to investigate what it can do to turn Norway into the "green battery of Europe". And it is anxious to show the world.

Sixth largest hydropower producer

Sixth largest hydropower producer

Sixth largest hydropower producer

96% of the electricity in Norway comes from Norwegian hydropower, from the country‘s 937 hydropower stations. Norway is the sixth largest hydropower producer in the world. However, the country can produce much more energy from hydropower and has the potential to become Europe’s green battery.

The idea is that excess power from Europe's growing network of solar arrays and wind farms could be sent to Norway to pump water up from lower reservoirs to higher tanks. Then, when Europe needs this power again, Norway opens the tap and lets the water spin through its hydropower turbines.

Gogstad is a PhD student at NTNU's Department of Energy and Process Engineering. His research is about pressure pulsations in Francis Turbines. He works on a technology that must reduce the trembling of the generators to avoid mechanical failures. This is key if Norway wants to increase the power output and if it wants to operate its power plants on a more flexible basis.

Open sesame. Unfortunately, unlike in the story of Ali Baba and the Forty Thieves, the gates do not open. "We are not allowed inside with the car because it is electric," said Gogstad. "Only diesel cars may enter since they are less likely to catch fire than electric vehicles and cars running on petrol."

You wouldn't expect either one to catch fire spontaneously. Norwegians, however, do not take security lightly. So we take a side entrance instead and continue by foot.

Thunderous noise

Thunderous noise

Thunderous noise

"Welcome to Leirfossene Power Station," said Gogstad. "If ever there is flooding due to a break in the piping you have to run back up following the luminous arrows alongside the road. You will only have a few minutes before the whole power plant is flooded."

We still have a few hundred metres to go and fifty metres to descend before reaching the turbines. But already the young engineer has to raise his voice to overcome the thunderous noise coming from the turbines. As we descend the temperature drops by eight degrees, to 12 degrees centigrade.

Norway‘s hydropower stations weren’t built for flexibility. Improving existing power plants, rather than developing new ones, is the focus of ongoing research. The first step is to solve the challenges associated with increasing the capacity and flexibility of existing plants.

What that is all about Gogstad explains when we have finally reached one of the two turbines. We can't see the turbine itself. A steel oval shaped bubble of a couple of metres diameter surrounds the turbine. It is fed with water streaming through a big yellow pipe that comes out of the cliff. 45 thousand litres of river water flow through the turbine per second, generating an output of 29 megawatts.

"Hold your hand against the turbine. Do you feel how it vibrates? And this is nothing yet," said Gogstad. "It is now running under optimal conditions. We can decrease or increase the water flow up to 55 thousand litres per second. Either way, the turbine will tremble much more because it will be running outside its best efficiency point."

Besides the risks of mechanical failures, the trembling can be disturbing for people living in the vicinity. Last spring there was a lot of melting water coming from higher up in the mountains. Statkraft had to increase the water flow. "People living nearby the power plant called Statkraft to ask what was going on," said Gogstad. "They thought there was an earthquake."

The vortex breakdown in the draft tube, the outlet of the turbine, is the primary cause of the flow instabilities and pressure fluctuations causing the vibration. Gogstad believes that if an extra tube, a shaft, is installed behind the vanes of the turbine, the water will be forced downwards more ferociously and cause fewer pressure fluctuations. He will fit his invention in a few weeks when the turbine is opened up for maintenance.

Where does all the water come from? The water is sucked up just in front of a barrage in the Nidelven river 64 metres higher up in the mountains. You can see the dam when standing in front of the doors of the power plant. Once it was the site of a spectacular waterfall, but now behind the dam all one sees is a steep cascade of barren rock. In the lake the water gurgles. A sign warns that you should not swim in between the vortices.

Swiss cheese

Swiss cheese

Swiss cheese

The Leirfossene Power Station is one of many in the Nidelven watershed. In total, there are 16 stations that combined generate 617 megawatts. Some of them are very old. Like the one just downstream. It is called Lower Leirfossene Power Station and was built at the beginning of the last century. With all of its arches, it looks more like a castle. In no way does it resemble the modern plants.

Between the two stations, there is no river. A 3.5 kilometre-long pipe through the mountain connects the modern Leirfossene Power Station with its smaller older brother. There, at the old power station, the water springs out of the rocks again, and the river continues its path towards Trondheim.

In Norway, most large power plants are built with very long power tunnels to transport water from the reservoir to the hydroelectric plant and onwards. The mountains are full of water tunnels. They add up to 4300 kilometres. The mountains are like Swiss cheese.

NTNU‘s professor in hydro-energy, Ole Gunnar Dahlhaug, has high hopes that Norway will become Europe’s green battery. "The Norwegian electricity grid is already connected to the grids of The Netherlands, Finland, Sweden, Denmark and Russia via high voltage cables," he said.

What's more, Norway is planning to build two new subsea power cables; one to Germany and the other to the UK. The German cable will come into operation in 2018. The cable to the UK will be the longest subsea cable of its type in the world, and will be operational in 2020.

Norway produces over a 130 Terawatthour per year," said Dahlhaug. "And the storage capacity in the Norwegian reservoirs amount to up to 86 Terawatthour." That is a tremendous amount. To put it into perspective, the whole of The Netherlands consumes about 117 Terawatthour per year.

A substantial part of it is in the northern parts of Norway. Laying down the infrastructure to transport that to Europe is expensive. NTNU researchers think that the electricity could partly be used to produce hydrogen, which can be shipped to the rest of Europe.

100 GW of new peak energy

In an article in the magazine of NTNU and SINTEF, Gemini, hydro-energy professor Magnus Korpås, explains why he believes Europe‘s energy market needs Norway’s hydro plants.

Korpås said: "Germany has installed a great deal of solar and wind-power in its energy system. So much, in fact, that the country will soon need better access to generation sources that can be switched on rapidly when the sun disappears or the wind doesn't blow."

"Germany could either build rapid start-up gas-fired power stations that can be quickly switched on and off to deal with peak loads – or use Norwegian hydropower as a ‘battery’."

Korpås believes the same holds for the export of balance power to the Netherlands and the UK, two nations that are going in for wind-power. According to the International Energy Agency (IEA), Europe needs about 100 GW of new peak energy to ensure energy supplies. "Norwegian hydropower could meet at least a quarter of this need," said Korpås.

For pumping of this sort to be made available to a sufficient extent, tunnels would have to be drilled between reservoirs that are not linked at present. New subsea power cables to the Continent would be needed, and the Norwegian national grid would have to be strengthened.

Not convinced

Tour leader Peter Joachim Gogstad is not completely convinced by the arguments of his superiors. "Does the idea of Norway being a green battery make sense? Yes partially. But it is only a short term solution," he said. "Houses are becoming more sustainable. And batteries will become cheap. So if you have your own solar panels, your house will be able to function as a small power plant by itself. But the efforts are not in vain. We can export our technology to other parts of the world."

This battery will not suffice

TU Delft energy market expert Dr. Nicolas Höning, of the Faculty of Electrical Engineering, Mathematics and Computer Science, encourages Norwegian ambitions. He defended his PhD research last May about flexible energy markets; ‘Peak reduction in decentralised electricity systems’.

"If this plan goes ahead, it will make investments in solar and wind energy more attractive. Because it will mean that producers of these forms of energy will be able to sell their energy for reasonable prices at all times. A few weeks ago surplus wind energy in Germany had to be sold for a negative price. With Norway as a green battery, extremes like that will not occur anymore. It is however also possible that if there is too much buffer capacity in Norway this will reduce the price of green energy. Predicting the future of our energy market is very complex."

"If we want to run our energy system completely on renewable energy by 2050 (with little or no nuclear power), we should use Norway as a green battery. But this battery will not suffice. Sometimes peak energy is needed within minutes. I don't think we should rely on one country delivering that short-term reserve energy to the rest of Europe. That would be a single point of failure. For those sharp peaks we need the smart grid. A system with dynamic local prices, where next to conventional local sources like gas turbines, households and electric cars can function as energy suppliers and buffers. But for balancing energy demands over periods, of say fifteen minutes or more, Norwegian hydropower would work out well."