Despite its important role for the future energy system, limited focus has been placed on how increasing hydropower capacity can help Sweden achieve a valuable balancing act within its power grid.
With hydropower currently accounting for around 40% of electricity across the country, its 2000 plants generated 66TWh in 2023 with an installed capacity of 16.4GW. Large scale plants above 10MW account for around 94% of this.
By 2045, Swedish electricity demand is expected to double and the share of intermittent power, mainly wind, is also expected to increase. And this where problems may arise. Between 2010 and 2023 total installed capacity in Sweden increased by 14.5GW and although wind and solar power also increased, hydropower capacity has remained largely unchanged. With higher levels of intermittent renewables in its energy system, Sweden is in growing need of a good balancing act.
To help resolve this, the Swedish Association of Engineers commissioned AFRY Management Consulting to carry out research during the summer of 2024. As Swedish hydropower is considered to be ‘built-out’ with limited potential for new plants, its aim was to identify ways in which existing hydropower plants can meet growing electricity demand.
The study encompassed a literature review, expert interviews, and quantitative analysis. It discovered that existing Swedish hydropower plants could increase capacity by 4000MW, a boost of 24% on current levels. The greatest potential is in northern Sweden due to 82% of current hydropower being sited in the northernmost areas of the country. And this enhanced capacity could also support an additional 800-1200MW of wind power integration, but challenges do exist.
For example there are major obstacles in the form of hydropower permit reassessments, with ambiguity concerning the implementation of a national plan as initial benchmarks for acceptable production loss are reported to have created great uncertainty. In addition altered flow approvals and financial viability for plant owners are also a cause for concern.
The report highlighted three main measures that can be taken to increase hydropower expansion across Sweden. These are:
- Full or partial turbine upgrades to improve flow rate and efficiency.
- Upgrading power units by replacing generators, turbines and related equipment to increase capacity.
- Installing additional power units in stations prepared for future capacity expansion.
In conclusion the study calls for further investigation into regulatory and financial barriers to unlocking hydropower’s full potential in Sweden.
Go with the flow
Other research focusing on Sweden analysed the complex balancing act that needs to be played out between hydropower production and ecosystem rehabilitation, when looking at environmental flows in a future climate.
In their research published in Science of the Total Environment, Widen et al hope their work contributes in shedding light on an increasing interest in environmental flow assessments, and the need to consider the effects of climate change and potential climate-change consequences for environmental flow versus hydropower conflicts.
In an effort to improve ecological conditions while ensuring a continued national supply of hydropower in Sweden, all hydropower permits are in the process of being relicensed, with environmental flows being designed to help meet the demands of this dual challenge. As the authors explain, to avoid implementing ineffective measures and enabling mitigation of extreme events, environmental flows need to be viewed ‘through the lens of climate warming and changing hydrological regimes’, and require a time perspective of at least a decade to consider among-year variability in hydrological conditions.
Widen et al’s study focuses on an entire regulated river system. Located in the north of Sweden and flowing from the Scandinavian mountain range to the Gulf of Bothnia, hydropower production on the Ume River developed during the 1950s and 1960s with 19 dams and hydropower stations. Six dams are storage reservoirs and the remaining 13 are impoundments with hydropeaking. Impacts on the ecosystem have included the replacement of lotic fish communities with lentic ones, with a reduction in fauna diversity and abundance as a result of loss of rapids, flow diversions and hydropeaking.
The researchers used the Intergovernmental Panel on Climate Change’s climate change projections for up to 2040, and modelled the consequences for electricity production when introducing a range of environmental flow options that have the potential to promote ecosystem functions or habitat conditions for riverine organisms. The simulation software One-area Power-Market Simulator (SINTEF, 2023) was also used.
The researchers based the 13 environmental flow options on combinations of four components:
- Prohibiting zero-flow events by requiring a minimum water flow through the station at all times, to prevent stretches of the river system becoming completely dry
- Matching seasonal water flow, with flow levels higher in spring and lower in summer, to promote the growth of vegetation alongside waterways
- Ensuring the release of water into fishways – areas of the river system intended to enable the movement of various fish species
- Ensuring the release of water into bypass channels – areas of the system that directly connect stretches of river upstream and downstream of a hydropower facility.
As the authors explained, introducing environmental flow measures like the ones analysed in their present study offer the opportunity to mitigate negative effects on riverine ecosystems caused by the combined stress of hydropower production and climate change, helping to avoid the most harmful flow and water-level events while increasing ecosystem resilience. They go on to give the example of the Storuman hydropower station. Here the duration of zero-flow events was projected to increase during hydrologically dry years in the future, with a 18% increase in the climate of 2040 compared to 1981–2010. However such a risk can be alleviated by introducing rules for continuous discharge.
Overall, the climate models predicted higher water runoff entering the river system in future scenarios than under recent conditions, with average annual water discharge at the hydropower station at the mouth of the Ume River predicted to be 1.8% greater in 2030 and 2.2% greater in 2040. The models also predicted seasonal changes, with lower runoff levels from June to October and higher levels from October to May.
Without any environmental flow management and taking into account hydropower operations, regulated flow in the river was not projected to change significantly under future scenarios. However, under these conditions there would be a reduction in seasonal variation in water flow. The difference between annual maximum and minimum flows at the river-mouth station under 2040 conditions was predicted to be 17% lower under the 2040 climate scenario than recent conditions.
Overall hydropower production without environmental flow restrictions would rise by 2.6% under a 2040 climate compared to recent conditions. Under six of the environmental flow options, projected power production under 2040 conditions looked higher than recent conditions without any environmental flow restrictions. Power production variability through the year was projected to reduce under 2040 conditions, primarily due to a less extreme dip in April.
This study demonstrates the feasibility of introducing environmental flow actions in Sweden, and other regions where increases in runoff are projected, with sustained hydropower production, having large benefits for riverine biodiversity and enhancing resilience of riverine ecosystems to climate change. Indeed, the environmental benefits of such management in this area would be especially significant in the future, when biodiversity is likely to be under increasing pressure from climate change impacts.
However, the researchers encourage an understanding of the interactions between environmental protection and power production on a case-by-case basis when determining optimal flow management options. Projected flow increases in a catchment can facilitate environmental flows, but also raises important questions about whether to allocate flow to ecosystem rehabilitation versus increasing renewable electricity production, since both can be argued to contribute to climate change mitigation, they add. In addition, any increase in hydrological extremes may lead to situations where meeting environmental flow demands might conflict with hydropower production if negative effects in riverine ecosystems and organisms are to be avoided.
This is why the authors suggest further studies are needed to understand the consequences of environmental flow management in regions where water scarcity is expected to increase in a future climate, since the challenges of meeting the requirements of all users may be greater. Collaboration among stakeholders will also be required for successful outcomes.
