Europe hydro vision needs 165km of tunnels Nov 2012
Patrick Reynolds for TunnelTalk
Up to 165km of new water tunnels could be needed to link the dozen new hydropower schemes proposed in Norway in the main scenario to deliver on its Green Battery initiative of lending strategic energy storage and electric grid balancing support to mainland Europe via a so-called supergrid.
Fig 1. Key hydro projects in Norway's Green Battery plan requiring major tunnelling

Fig 1. Key hydro projects in Norway's Green Battery plan requiring major tunnelling

The tunnels range widely in length from a few kilometres to almost 30km for the giant hydropower schemes, some of which alone would be among the largest in Europe. The entire cluster of projects in south west Norway would dominate the energy sector's development in the region as well as drawing heavily on the tunnelling sector.
The initiative's chief sponsor is Germany, a country whose environmental advisory board submitted a report to Parliament arguing that it is reasonable to achieve almost all of its electrical power needs from renewable sources by 2050. But the need to establish Norway, which accounts for more than half of Europe's water reservoir reserves, is seen as key to the plan.
By increasing capacity for hydro electricity generation there, Norway is envisaged as Europe's Green Battery. It would be able to respond rapidly to plug the supply gap when other less reliable renewables, notably solar and wind, are offline; and at times when solar and wind are operating at peak capacity surplus energy from the mainland and the UK can be used to pump water back to the reservoirs in Norway. Sintef, one of the largest independent energy research organisations in Northern Europe, is collaborating with energy industry industry players, governments and other partner organisations and has just published a major report on the Green Battery options. It believes that at current levels of production, Norwegian hydropower is theoretically capable of compensating for the loss incurred should all of Europe's existing wind turbines shut down for a period of one month.
A dozen hydro projects - seven conventional and five pumped storage - have been identified in the main scenario considered by researchers at Sintef when looking at options to use existing reservoirs to help fulfil the 20GW of new capacity needed for the so-called Green Battery scheme. The main scenario would provide 11.2GW of capacity from new plants towards that goal.
The longest tunnels foreseen would be for the 1GW Tinnsjo and 1.4GW Tonstad pumped storage schemes, with lengths of 29.3km (82m2 cross section) and 22.4km (128m2), respectively.
Long tunnels are also needed for the 700MW Sy-Sima hydropower project, the 1.4GW Kvilldal pumped storage scheme and the 700MW Tyin hydropoewer project - with lengths of 21.7km (45m2), 19.1km (88m2) and 18.9km (39m2), respectively.
Two other projects call for tunnels longer than 10km - the 1.4GW Josenfjorden hydropower project and 700MW Holen pumped storage scheme, the respective lengths of which would be 14.1km (82m2) and 12.4km (66m2).
The remaining five projects among the dozen all have tunnels of less than 10km long but their combined length is 27.2km. They are: the 700MW Aurland hydropower project (9.1km long tunnel, 46m2 cross section); the 400MW Mauranger hydropower project (5.3km, 23m2); the 1.4GW Lysebotn hydropower project (5.6km, 125m2); the 700MW Oksla hydropower project (4km, 100m2); and, the 700MW Tysso pumped storage scheme (3.2km, 56m2).
Sintef's Green Battery report

Sintef's Green Battery report

The construction cost for those principal hard rock tunnels on the projects - excluding any penstock excavation, access, cable, gallery or other underground works - is estimated at almost NK4.86 billion (US$853 million). The typical construction period foreseen for the hydropower or pumped storage projects, as full schemes, is about four to five years.
The tunnels would enable the plants and cascades of existing reservoirs to be controlled in a larger regional network of neighbouring river basins, providing massive storage under the Green Battery plan to soak up excess electricity production from renewable energy projects in mainland Europe, especially Germany. The fast response capability of individual hydropower and pumped storage plants would also allow the massive network to provide load balancing, frequency support and other ancillary services when the renewables sporadically produce less than needed and the transmission grid needs rapid help.
The problem for the grid, and the opportunity for hydro - and tunnelling - comes as a result of the intermittent and unpredictable generation from wind and solar power projects, which are being invested in heavily in Europe, most notably Germany.
As those renewables take an ever-greater share of the generation mix in the coming years the energy wastage challenge - or even plant shutdowns, if it is too windy - and the need for grid balancing will become an increasing problem. The most immediate challenge for the energy utilities and governments is to build high capacity transmission links for the grids, below the North Sea and also through Denmark to Germany, with a large number of hydropower schemes earmarked as needed in the next couple of decades.

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