Abstract
The electricity generation in Norway is dominated by more than 90 percent of hydropower, mostly developed in the period of 1960-1990. At the time of development, electricity consumption was dominated by an almost constant consumption for energy-intensive industries and household heating, creating a load profile with small variations although a strong seasonal pattern. Most hydropower plants were designed to meet this load profile, with little flexibility and high use time.
With the energy transition towards renewable energies, both the load profile and the electricity generation pattern are changing towards a more variable system. Recent additional interconnectors to neighbouring countries have also connected the Norwegian power system to other systems with large shares of variable renewables that are strongly weather-dependent. Power prices are becoming more volatile with large variations over different time horizons ranging from intra-day to week and season. This opens for investments in flexibility and storage
Norway has currently only nine pumped storage plants with installed capacity of 1 344 MW. These assets are mostly used for seasonal pumping to preserve water at higher altitudes in periods with high inflow and low power price. Following the more volatile power market and the energy transition, several Norwegian hydropower companies are looking into the possibility to develop pumped storage between existing reservoirs. Norway has many pairs of large reservoirs at different altitudes, making pumped hydro possible without large new environmental impacts. The most known projects in planning are:
• Illvatn pumped storage (licence given): 48MW.
• Three new pumped storage power plants in the Røldal-Suldal system (filed for license): Kvanndalsfoss, Røldal and Novle pumped storage plants of 664MW in total.
• Converting two conventional turbines in Saurdal power plant to pumped storage (in planning): Increasing existing reversible pump turbine capacity from 320MW to 660MW.
• Upper Otra pumped storage plant from Botsvann to Vatnedalsvatn or Urarvatn (in planning): around 1 000MW.
• Rjukan pumped storage plant from Tinnsjø to Møsvatn (in planning): around 1 000 MW.
• Driva pumping station from River Driva to Gjevilvatnet, and a new power plant from Gjevilvatnet to the sea (in planning): 400MW.
The main challenges for developing pumped storage hydropower between existing reservoirs are related to the investment costs and tax regime in relation to expected power price variation and market solution and environmental impacts and permitting as well as local and societal acceptance.
Pumped storage hydropower systems affect the environment primarily through two mechanisms. First, by transferring water between reservoirs, these systems mix water masses with different physio-chemical properties. Secondly, the operation of these systems results in fluctuations of water levels within the reservoir, which can influence shoreline erosion, habitat availability, and ecosystem structure.
This paper will briefly show the planned pumped storage developments in Norway and discuss challenges related to environmental impacts and how it is possible to mitigate negative effects and potentially improve both hydro-physical and ecological conditions in some reservoirs that have been degraded by hydropower operations.