Norway has a lot of hydroelectric plants: a total of 937 of them, which provide a population of 5 million with around 98 percent of its electricity. In fact, the Scandinavian country is home to roughly half of all the hydroelectric water storage reservoirs in Europe.

This vast system could also offer a Europe a substantial amount of energy storage -- up to 20 gigawatts of it -- if an ambitious scheme currently being proposed can overcome political and social hurdles and get the necessary funding. That’s according to Kaspar Vereide, an engineer at the Norwegian University of Science and Technology in Trondheim. And his models suggest it could all be achieved in seven years.

Vereide is not alone in thinking Norway could become a vast green battery for Europe. The Centre for Environmental Design of Renewable Energy has concluded that there are four realistic scenarios for pumped hydro energy storage in the country, ranging from a Nordics-only scenario, where Norway only looks after its own needs, plus some of those of its Scandinavian neighbors; to a so-called ‘big storage’ scenario, which, it says, would see “Norwegian hydropower play an important role in integrating variable renewable sources into the European power system by providing large volumes of balancing over various time horizons to the North Sea countries through highly integrated grids and power markets.”

It’s this "big storage" scenario -- with Norway becoming "the green battery of Europe" -- that Vereide has in mind.

A nationwide 20-gigawatt pumped hydro energy storage project sounds expensive, requiring a massive amount of new infrastructure. But that's not necessarily so, says Vereide and his colleagues, because the 20 gigawatts of storage could be created by simply modifying existing plants whose reservoirs currently fill up and drain slowly over time, depending on ice melt, rainfall and other seasonal factors. These upgrades would allow them to be filled and drained much more rapidly, in order to meet the needs of commercially viable energy storage.

Vereide claims that it would cost around €6 billion ($6.6 billion) to refit the 20 existing plants needed and to supply the necessary grid connections. Basically, he calculates €300 million ($328 million) to ensure 1,000 megawatts for each of 20 existing hydropower plants, plus the same amount of money again for adequate connection to the Norwegian grid. What this amount doesn’t include is the price tag for additional interconnectors to strengthen links between Norway and the rest of Europe, however -- which would be essential for the scheme to fly.

Norway already has some HVDC interconnectors with neighboring countries and is planning more. And these are already used for what Christer Gilje,
 vice president of corporate communications for Statnett, describes as “virtual energy storage.” Effectively, Statnett -- the Norwegian electricity system operator -- imports cheap renewable energy from surrounding countries to use in place of the country’s usual hydropower. Norwegian hydroelectricity is exported back to those countries on demand.

There are currently six HVDC interconnectors -- four HVDC cables to Denmark totaling 1,700 megawatts, and another 700-megawatt link to the Netherlands -- that make this current energy exchange market possible. Giving an example of how the arrangement works right now, Gilje explained that Denmark’s reduction of coal-generated energy in favor of wind, with its more variable output, means that there has been an increased need for the Danes to be able to export excess electricity and have plenty of Norwegian hydropower on tap for when wind couldn’t deliver. As renewables grow in other parts of northern Europe, so will the need for this “virtual energy storage,” is Statnett’s thinking -- hence the advance plans for two more high-voltage links.

The recently announced 1,400-megawatt NSN Link will join the U.K. to Norway, cost €1.5 billion ($1.64 billion), and, at 740 kilometers, will be the longest HVDC interconnector in the world. It’s hoped it will be operational in 2021, and Statnett specifically cites the projected expansion of British wind power as being a key motive for its construction. Meanwhile, the Nord.Link interconnector should also provide a 1,400-megawatt connection, in this case to Germany, a year or so earlier.

Of course what Gilje describes as “virtual energy storage” isn’t exactly what most of us would describe as energy storage. What Vereide is proposing, however, is the real deal. And the interconnector system currently being used to mop up cheap, variable renewable energy and export hydropower could, of course, be used to provide energy storage for the increasing amount of wind and solar energy sprouting up all over Europe. But there would have to be even more interconnectors to maximize Norway’s storage potential, says Vereide.

By his calculation, the big-storage scenario would need around eight more connectors than are currently planned. As they have a price tag of around €1.5 billion ($1.64 billion) each, that would add another €12 billion ($13.1 billion) to the original €6 billion ($6.6 billion) bill for the refit of 20 hydroelectric plants. When asked, Statnett spokesperson Gilje underlined that there are no plans he knew of to go beyond the two new interconnectors at present, and to do so would have to be the result of new government policy.

And government policy is where the big problems start for big storage. In 2013, Anne Therese Gullberg, a senior researcher at the Center for International Climate and Environmental Research in Oslo, published a paper entitled "The Political Feasibility of Norway as the ‘Green Battery’ of Europe." She concluded that while it was technically feasible for Norway to become a green battery, the political climate meant that that scenario would not come about anytime soon. In a recent interview, she emphasized that the situation has not changed in the intervening two years, due to continued political and social opposition in the country.

A major and influential party in the current governing coalition has pledged to keep electricity bills down. Investment in storage would add to those bills, as would a number of additional HVDC connectors and the accompanying need to upgrade the grid infrastructure. What’s more, some of those bill-payers -- Norway’s intensive energy users -- would be subsidizing storage, but they wouldn’t be reaping its profits, and they are a powerful lobby, says Gullberg.

And even if private investment can be found to prevent bill increases, there is also lack of enthusiasm in the country for more changes to the hydroelectric system and the additional cables that would be needed to update plants and the grid, says Gullberg. “In Norway, people don’t like to see more grids in their wilderness,” she explains.

In addition, the repurposed reservoirs, which have traditionally filled up and drained according to an annual cycle, would have rapidly changing water levels to fulfill their new energy storage role. Not only could that have an impact on the natural beauty and perhaps the ecology of the area, it’s not very good if you like to skate or ski across winter ice, as many Norwegians do.

This nature-aware constituency is not necessarily swayed by low carbon arguments, either. “Why should we sacrifice parts of our landscape when there’s no real guarantee that storage will bring down emissions?” is an argument that’s often heard in Norway, says Gullberg.

Vereide, too, concedes that the ambitious plans for 20 gigawatts of storage, while technically feasible, might be more politically realistic at a more modest 5 gigawatts -- at least in the short term.

However, despite the current situation, both remain quietly optimistic -- at least for the longer game. “The issue of energy storage is like a pendulum in Norway. We go from an extreme enthusiasm on the one side to total pessimism on the other. At the moment, we are somewhere in the middle,” summarizes Gullberg.

Which way the pendulum swings next is certainly worth keeping an eye on.