Impacts of climate variability and climate change on renewable power generation

Anthropogenic climate change represents a major risk for human civilization and its mitigation requires reductions of greenhouse gas emissions. To stay consistent with the long-term temperature targets of international climate policy, global greenhouse gas emissions have to reach zero within a few decades. Such a dramatic transition towards sustainability in all sectors of human activity requires the decarbonization of power generation at an early stage. In absence of other viable technology choices and given the significant cost declines, renewable power generation forms the backbone of the decarbonization. In contrast to thermal power plants, most renewables are not dispatchable but their generation dynamics are governed by the weather. This dissertation adds to the quantification of impacts of climate variability on wind power generation on different time scales. In particular, it shows that inter-annual wind power generation variability already today has a strong influence on congestion management costs in Germany. Understanding this variability as a normal system feature helps to prevent short-sighted reactions in legislation and power system design. Moreover, it is shown that relevant multi-decadal wind power generation variability exists. Owing to timescales of up to 50 years, these modes are not sufficiently sampled in any modern reanalysis (e.g., MERRA2 or ERA-Interim), which currently cover around 40 years. Consequently, power system assessments based on modern reanalyses may be flawed and should be complemented by multi-decadal assessments. In this context, I also show that 20th century reanalyses (ERA-20C, CERA20C, 20CRv2c) disagree strongly and systematically with respect to long-term wind speed trends. The discrepancy can be traced back to marine wind speed observations which also feature strong upward wind trends that are likely due to an evolving measurement technique. As a consequence, 20th century reanalyses should be employed with care and cross-validation of results is recommended. Due to their weather dependency, renewables are potentially vulnerable to climate change. Indeed, I show that the benefits of large-scale transmission infrastructure in Europe shrink under strong climate change (RCP8.5). The effect is robust across a five member EUROCORDEX ensemble and can be solidified in a larger CMIP5 ensemble. It is rooted in more homogeneous wind conditions over Europe that lead to less smoothing effects via large scale spatial integration. Lastly, the debate around negative emission technologies to enlarge the carbon budget currently focuses on land-based approaches such as Bioenergy with Carbon Capture and Storage. Based on a schematic integration of Direct Air Capture (DAC), we show that its flexibility complements renewable generation variability and can help to integrate large shares of renewables

Climate information websites: an evolving landscape

The climate change agenda is populated by actors and agencies with different objectives, values, and motivations, yet many seek decision scale climate information to inform policy and adaptation responses. A central element of this network of activity is the climate information website (CIW) that has seen a rapid and organic growth, yet with variable content and quality, and unfettered by any code of practice. This builds an ethical–epistemic dilemma that warrants assessment as the presence of CIWs contribute to real-world consequences and commitment. This study considers the context of CIW growth, and reviews a representative sample of CIWs to draw out key issues for consideration in CIW development. We assess content, function, and use-case value through a dual approach of a typology and user experience narratives to evaluate the general efficacy of a CIW. The typology reveals strong contrasts in content, complicated interfaces, and an overload of choice making it difficult to converge on a stable outcome. The narratives capture user experience and highlight barriers that include navigation difficulties, jargon laden content, minimal or opaque guidance, and inferred information without context about uncertainty and limits to skill. This illuminates four concerns: (1) the ethics of information provision in a context of real-world consequences; (2) interfaces that present barriers to achieving robust solutions; (3) weak capacity of both users and providers to identify information of value from the multimodel and multimethod data; and (4) inclusion of data that infer skill. Nonetheless, results provide a positive indication of a community of practice that is still maturing. WIREs Clim Change 2017, 8:e470. doi: 10.1002/wcc.470. For further resources related to this article, please visit the WIREs website

European multidecadal solar variability badly captured in all centennial reanalyses except CERA20C

Long-term historic climate datasets are valuable tools to investigate climate variability, validate climate models and contextualize anticipated climate change. Surface solar radiation is one particularly relevant variable, with implications on policy decisions (e.g., performance of solar panels) and fundamental questions in climate science (e.g., regarding the energy budget). While all current twentieth century reanalyses provide surface solar radiation, we demonstrate that most of them fail to capture multidecadal surface radiation variability in Europe. To this end, we systematically compare the reanalyses 20CRv2c, 20CRv3, ERA20C and CERA20C and the free model run ERA20CM. We show that only CERA20C captures dimming (1949 - 1979) and brightening (1979 -2009) in line with station observations, satellite-era reanalyses and established theory. The lack of multidecadal surface radiation variability in 20CRv2c/v3 is plausible given the use of constant aerosols. In contrast, ERA20CM, ERA20C and CERA20C are forced with time-varying aerosols. Despite this common forcing, ERA20CM and ERA20C surprisingly show no trends in clear-sky fluxes over the dimming and brightening periods while CERA20C shows significant trends. We discuss different potential explanations for this discrepancy (model versions, ocean coupling and ensemble size) and conclude that none of them provides a convincing explanation. Our results therefore imply that only CERA20C is suitable for assessments of surface solar radiation variability on multi-decadal timescales. This particularly applies to impact studies, for example, on long-term potentials of solar power generation

FPGA implementation of a 32x32 autocorrelator array for analysis of fast image series

With the evolving technology in CMOS integration, new classes of 2D-imaging detectors have recently become available. In particular, single photon avalanche diode (SPAD) arrays allow detection of single photons at high acquisition rates (\geq 100 kfps), which is about two orders of magnitude higher than with currently available cameras. Here we demonstrate the use of a SPAD array for imaging fluorescence correlation spectroscopy (imFCS), a tool to create 2D maps of the dynamics of fluorescent molecules inside living cells. Time-dependent fluorescence fluctuations, due to fluorophores entering and leaving the observed pixels, are evaluated by means of autocorrelation analysis. The multi-{\tau} correlation algorithm is an appropriate choice, as it does not rely on the full data set to be held in memory. Thus, this algorithm can be efficiently implemented in custom logic. We describe a new implementation for massively parallel multi-{\tau} correlation hardware. Our current implementation can calculate 1024 correlation functions at a resolution of 10{\mu}s in real-time and therefore correlate real-time image streams from high speed single photon cameras with thousands of pixels.Comment: 10 pages, 7 figure

Differential climate impacts for policy-relevant limits to global warming: The case of 1.5 °c and 2 °c

Robust appraisals of climate impacts at different levels of global-mean temperature increase are vital to guide assessments of dangerous anthropogenic interference with the climate system. The 2015 Paris Agreement includes a two-headed temperature goal: "holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C". Despite the prominence of these two temperature limits, a comprehensive overview of the differences in climate impacts at these levels is still missing. Here we provide an assessment of key impacts of climate change at warming levels of 1.5°C and 2°C, including extreme weather events, water availability, agricultural yields, sea-level rise and risk of coral reef loss. Our results reveal substantial differences in impacts between a 1.5°C and 2°C warming that are highly relevant for the assessment of dangerous anthropogenic interference with the climate system. For heat-related extremes, the additional 0.5°C increase in global-mean temperature marks the difference between events at the upper limit of present-day natural variability and a new climate regime, particularly in tropical regions. Similarly, this warming difference is likely to be decisive for the future of tropical coral reefs. In a scenario with an end-of-century warming of 2°C, virtually all tropical coral reefs are projected to be at risk of severe degradation due to temperature-induced bleaching from 2050 onwards. This fraction is reduced to about 90% in 2050 and projected to decline to 70% by 2100 for a 1.5°C scenario. Analyses of precipitation-related impacts reveal distinct regional differences and hot-spots of change emerge. Regional reduction in median water availability for the Mediterranean is found to nearly double from 9% to 17% between 1.5°C and 2°C, and the projected lengthening of regional dry spells increases from 7 to 11%. Projections for agricultural yields differ between crop types as well as world regions. While some (in particular high-latitude) regions may benefit, tropical regions like West Africa, South-East Asia, as well as Central and northern South America are projected to face substantial local yield reductions, particularly for wheat and maize. Best estimate sea-level rise projections based on two illustrative scenarios indicate a 50cm rise by 2100 relative to year 2000-levels for a 2°C scenario, and about 10 cm lower levels for a 1.5°C scenario. In a 1.5°C scenario, the rate of sea-level rise in 2100 would be reduced by about 30% compared to a 2°C scenario. Our findings highlight the importance of regional differentiation to assess both future climate risks and different vulnerabilities to incremental increases in global-mean temperature. The article provides a consistent and comprehensive assessment of existing projections and a good basis for future work on refining our understanding of the difference between impacts at 1.5°C and 2°C warming

High-resolution large-scale onshore wind energy assessments : A review of potential definitions, methodologies and future research needs

Funding Information: KG, MK, JS, OT and SW gratefully acknowledge support from the European Research Council (’‘reFUEL’’ ERC-2017-STG 758149). JL has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 715132). MJ and IS were funded by the Engineering and Physical Sciences Research Council [ EP/R045518/1 ] through the IDLES programme. JW is funded through an ETH Postdoctoral Fellowship and acknowledges support from the ETH foundation and the Uniscientia foundation. The authors gratefully acknowledge the helpful comments of three anonymous reviewers on an earlier version of this paper.Peer reviewedPublisher PD

The importance of weather and climate to energy systems: a workshop on next generation challenges in energy-climate modelling

Over 80 international participants, representing weather, climate, and energy systems research, joined two 4-hour remote sessions to highlight and prioritize ongoing and future challenges in energy-climate modelling. The workshop had two primary goals: to build a deeper engagement across the “energy” and “climate” research communities, and to identify and begin to address the scientific challenges associated with modelling climate risk in energy systems

Multi-decadal offshore wind power variability can be mitigated through optimized European allocation

Wind power is a vital ingredient for energy system transformation in line with the Paris Agreement. Limited land availability for onshore wind parks and higher wind speeds over sea make offshore wind energy increasingly attractive. While wind variability on different timescales poses challenges for planning and system integration, little focus has been given to multi-decadal variability. Our research therefore focuses on the characteristics of wind power on timescales exceeding ten years. Based on detrended wind data from the coupled centennial reanalysis CERA-20C, we calculate European long-term offshore wind power potential and analyze its variability focusing on three locations with distinct climatic conditions: the German North Sea, the Greek Mediterranean and the Portuguese Atlantic coast. We find strong indications for two significant multi-decadal modes that are identified consistently using two independent spectral analysis methods and in the 20-year running mean time series. In winter, the long-term evolution of wind power and the North Atlantic Oscillation (NAO) are directly linked in Germany and Portugal. While German North Sea wind power is positively correlated with the NAO (r=0.82), Portuguese Atlantic coast generation is anti-correlated with the NAO (r=−0.91). We evaluate the corresponding potential for spatial balancing in Europe and report substantial benefits from European cooperation. In particular, optimized allocations off the Portuguese Atlantic coast and in the German North Sea allow to reduce multi-decadal generation variance by a factor of 3–10 compared with country-level approaches.ISSN:1680-7340ISSN:1680-735