Tapping hidden hydropower potential in Swiss Alpine catchments in the context of the planned nuclear power phase out

In its Energy Strategy 2050, Switzerland is revising its energy perspectives with a strong focus on renewable sources of energy and in particular hydropower. In this context, the Swiss Government funded a number of competence centers for energy research (SCCERs), including one on the Supply of Energy (SCCER-SoE), which develops fundamental research and innovative solutions in geoenergies and hydropower . Hydropower is already the major energy source in Switzerland, corresponding to approximately 55% of the total national electricity production (which was 69 TWh in 2014). The Energy Strategy 2050 foresees at least a net increase by 1.53 TWh/year in average hydrological conditions, in a context were almost all major river systems are already exploited and a straightforward application of recent environmental laws will impact (reduce) current hydropower production. In this contribution, we present the roadmap of the SCCER-SoE and an overview of our strategy to unravel currently non-exploited hydropower potential, in particular in river systems that are already used for hydropower production. The aim is hereby to quantify non-exploited natural flows, unnecessary water spills or storage volume deficits, whilst considering non-conventional approaches to water resources valuation and management. Such a better understanding of the current potential is paramount to justify future scenarios of adaptation of the existing hydropower infrastructure combining the increase of storage capacity with new connections between existing reservoirs, heightening or strengthening existing dams, increasing the operational volume of natural lakes (including new glacier lakes), or by building new dams. Tapping hidden potential shall also require operational changes to benefit from new flow patterns emerging under an evolving climate and in particular in the context of the ongoing glacier retreat. The paper shall present a broad view over the mentioned issues and first conclusions of ongoing research at the country scale.

Potential increase in energy storage capacity in the Swiss Alps to support the massive development of renewables: Case study of the Grande Dixence hydropower scheme

Pedro Filipe De Almeida Manso, Jérôme François Sylvain Dujardin, Blaise Monay, Anton Schleiss

Only 42 % of the mean annual production of large hydropower plants in the Swiss Alps is stored in their reservoirs. Once the reservoirs are full at the end of the summer semester, plants are operated as run-on-the-river in order to avoid spilling. A significant part of the hydropower resources are thus sold at discount prices and cannot be transferred to the winter semester. It is precisely in the winter semester that Switzerland imports large volumes of electricity from its neighbours. In order to support the nuclear power phase-out planned in the Swiss Energy Strategy 2050, hydropower must not only maintain its 2012 production level but mainly step-up its role in the grid and improve its remuneration. Following this strategy, the present production of the nuclear plants will be mainly replaced by renewables and the total electricity storage capacity must therefore be increased by 10 to 30%. Hydropower schemes face two challenges: to reduce the lack of electricity production in the winter semester and to lay a suitable foundation for the increased storage demand of intermittent renewables such as wind and solar. In this work, we propose a methodology to evaluate the potential increase in energy storage capacity of a portfolio of large reservoirs in Alpine regions, considering future climate scenarios and future reservoir operation scenarios corresponding to different economic conditions (e.g. more/less PV and wind production) and reservoir management time scales (seasonal, multiannual). In addition to exploring the performance of existing reservoirs in different future conditions, we assess the possibility to link reservoirs (mutualising the use of storage) and/or to raise dams (increasing storage and annual runoff regulation). In fact, several large dams provide the structural capacity to be heightened by at least 10% of their height. Additionally, there are strategic locations that could be used to create new large reservoirs. This methodology is applied to a test site located on the left bank of the Rhône River in Switzerland. Our method uses both recent and future hydrology, as well as operational data to determine the optimal reservoir live storage capacity for a hydropower scheme. In addition to intra-annual energy and water transfer, we also consider the transfer in between years to account for adverse climate conditions. In order to apply this methodology to the Grande Dixence hydropower scheme, we show two opportunities to increase the seasonal storage capacity: heightening of the main dam and the creation of a new upstream reservoir. Our study shows that the largest Swiss reservoir with 400 hm3 can provide more seasonal storage in all climate scenarios, however a full heightening of 10% may not be optimal regarding the different intra-annual operation modes investigated. However, should the operator wish to guarantee production in extreme dry years the reservoir heightening would also provide the possibility of establishing a pluriannual reserve or extra room for pumped storage.

2019

Optimized and adapted hydropower management considering glacier shrinkage scenarios in the Swiss Alps

Frédéric Jordan, Anton Schleiss, Stéphane Christian Olivier Terrier

Global warming is an alarming reality and likely leads to an increase of multiple pressures on socio-economic systems. However, in high-mountain regions it might also become an opportunity to adapt existing hydropower schemes and future projects to this new reality. In the Alps, the melting of glaciers first produces over the near future an increase of the average annual discharge depending on glacier and catchment characteristics, especially during the summer season. Nevertheless after a certain time, significant decrease of runoff related to glacier melting must be considered for hydropower management. Moreover, the melted glaciers free new alpine valley areas, which have a potential for the construction of new dams and reservoirs. The opportunity to build new dams and hydropower plants downstream of retreating glaciers is studied systematically in Switzerland within the framework of the National Research Program on Sustainable Water Management (NRP61) under the project “New lakes in deglaciating highmountain areas: climate-related development and challenges for sustainable use (NELAK)”. The developed methodology is based on several prediction models. Regional climate models provide spatially distributed rainfall and temperature scenarios for the next 50 years. The RS3.0 CLIMATE rainfall-runoff hydrological model computes the glacier evolution, the river discharge at the outlet of the catchment area as well as the hydropower production of the new lakes. Another model (GlabTop) is used to predict the future topography and geomorphology underneath the melting glaciers, in order to define the optimal locations of the future dams and reservoirs. As a case study the Corbassière glacier near the Mauvoisin reservoir in Valais is presented. The opportunity of the construction of a new dam and a hydropower plant is studied, as well as its economic benefit and its impacts on the environment. The result of the case study provides a basis to assess the potential of investing in such projects to ensure the Swiss hydroelectricity production also in future.

CRC Press, Taylor & Francis Group2011

Pumped-storage with small hydropower – an option?

Nicolas Crettenand, Philippe Heller, Benoît Mailler

This paper contributes towards exploring the technical and institutional feasibility of small hydropower storage and pumped-storage schemes in Switzerland. Within the European and Swiss context of the facilitation of renewable energy technologies, which includes small hydropower (SHP), intermittent sources such as solar and wind increase the need for additional energy storage capacities. Hydropower pumped-storage schemes remain the most efficient and profitable option to “store” electricity. In Switzerland, most of the large scale hydropower potential is already exploited. The potential of SHP (