In the renewable energy sector, a dunkelflaute (German: [ˈdʊŋkəlˌflaʊtə] , lit. 'dark doldrums' or 'dark wind lull', plural dunkelflauten) [1] is a period of time in which little or no energy can be generated with wind and solar power, because there is neither wind nor sunlight. [2] [3] [4] In meteorology, this is known as anticyclonic gloom. [5]
Unlike a typical anticyclone, dunkelflauten are associated not with clear skies, but with very dense cloud cover (0.7–0.9), consisting of stratus, stratocumulus, and fog. [6] As of 2022 [update] there is no agreed quantitative definition of dunkelflaute. [7] Li et al. define it as wind and solar both below 20% of capacity during a particular 60-minute period. [8] High albedo of low-level stratocumulus clouds in particular – sometimes the cloud base height is just 400 meters – can reduce solar irradiation by half. [6]
In the north of Europe, dunkelflauten originate from a static high-pressure system that causes an extremely weak wind combined with overcast weather with stratus or stratocumulus clouds. [9] There are 2–10 dunkelflaute events per year. [10] Most of these events occur from October to February; typically 50 to 150 hours per year, a single event usually lasts up to 24 hours. [11]
In Japan, on the other hand, dunkelflauten are seen in summer and winter. The former is caused by stationary fronts in early summer and autumn rainy seasons (called Baiu and Akisame, respectively), [12] while the latter is caused by arrivals of south-coast cyclones. [13]
These periods are a big issue in energy infrastructure if a significant amount of electricity is generated by solar and wind power. [14] [1] [15] Dunkelflauten can occur simultaneously over a very large region, but are less correlated between geographically distant regions, so multi-national power grid schemes can be helpful. [16] Events that last more than two days over most of Europe happen about every five years. [17] To ensure power during such periods flexible energy sources may be used, energy may be imported, and demand may be adjusted. [18] [19]
For alternative energy sources, countries use fossil fuels ( coal, oil and natural gas), hydroelectricity or nuclear power and, less often, energy storage to prevent power outages. [20] [21] [8] [22] Long-term solutions include designing electricity markets to incentivise clean flexible power. [19] A group of countries is following on from Mission Innovation to work together to solve the problem in a clean, low-carbon way by 2030, including looking into carbon capture and storage and the hydrogen economy as possible parts of the solution. [23]
In the renewable energy sector, a dunkelflaute (German: [ˈdʊŋkəlˌflaʊtə] , lit. 'dark doldrums' or 'dark wind lull', plural dunkelflauten) [1] is a period of time in which little or no energy can be generated with wind and solar power, because there is neither wind nor sunlight. [2] [3] [4] In meteorology, this is known as anticyclonic gloom. [5]
Unlike a typical anticyclone, dunkelflauten are associated not with clear skies, but with very dense cloud cover (0.7–0.9), consisting of stratus, stratocumulus, and fog. [6] As of 2022 [update] there is no agreed quantitative definition of dunkelflaute. [7] Li et al. define it as wind and solar both below 20% of capacity during a particular 60-minute period. [8] High albedo of low-level stratocumulus clouds in particular – sometimes the cloud base height is just 400 meters – can reduce solar irradiation by half. [6]
In the north of Europe, dunkelflauten originate from a static high-pressure system that causes an extremely weak wind combined with overcast weather with stratus or stratocumulus clouds. [9] There are 2–10 dunkelflaute events per year. [10] Most of these events occur from October to February; typically 50 to 150 hours per year, a single event usually lasts up to 24 hours. [11]
In Japan, on the other hand, dunkelflauten are seen in summer and winter. The former is caused by stationary fronts in early summer and autumn rainy seasons (called Baiu and Akisame, respectively), [12] while the latter is caused by arrivals of south-coast cyclones. [13]
These periods are a big issue in energy infrastructure if a significant amount of electricity is generated by solar and wind power. [14] [1] [15] Dunkelflauten can occur simultaneously over a very large region, but are less correlated between geographically distant regions, so multi-national power grid schemes can be helpful. [16] Events that last more than two days over most of Europe happen about every five years. [17] To ensure power during such periods flexible energy sources may be used, energy may be imported, and demand may be adjusted. [18] [19]
For alternative energy sources, countries use fossil fuels ( coal, oil and natural gas), hydroelectricity or nuclear power and, less often, energy storage to prevent power outages. [20] [21] [8] [22] Long-term solutions include designing electricity markets to incentivise clean flexible power. [19] A group of countries is following on from Mission Innovation to work together to solve the problem in a clean, low-carbon way by 2030, including looking into carbon capture and storage and the hydrogen economy as possible parts of the solution. [23]