Danish Energy Agency

Key observational indicators of climate change in the Arctic, most spanning a 47 year period demonstrate fundamental changes among nine key elements of the Arctic system. We find that, coherent with increasing air temperature, there is an intensification of the hydrological cycle, evident from increases in humidity, precipitation, river discharge, glacier equilibrium line altitude and land ice wastage. Downward trends continue in sea ice thickness (and extent) and spring snow cover extent and duration, while near-surface permafrost continues to warm. Several of the climate indicators exhibit a significant statistical correlation with air temperature or precipitation, reinforcing the notion thatincreasing air temperatures and precipitation are drivers of major changes in various components of the Arctic system. To progress beyond a presentation of the Arctic physical climate changes, we find a correspondence between air temperature and biophysical indicators such as tundra biomass and identify numerous biophysical disruptions with cascading effects throughout the trophic levels. These include: increased delivery of organic matter and nutrients to Arctic near-coastal zones; condensed flowering and pollination plant species periods; timing mismatch between plant flowering and pollinators; increased plant vulnerability to insect disturbance; increased shrub biomass; increased ignition of wildfires; increased growing season CO 2 uptake, with counterbalancing increases in shoulder season and winter CO 2 emissions; increased carbon cycling, regulated by local hydrology and permafrost thaw; conversion between terrestrial and aquatic ecosystems; and shifting animal distribution and demographics. The Arctic

The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol = 1 martian day = 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander (VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1.

This article provides a synthesis of the latest observational trends and projections for the future of the Arctic. First, the Arctic is already changing rapidly as a result of climate change. Contemporary warm Arctic temperatures and large sea ice deficits (75% volume loss) demonstrate climate states outside of previous experience. Modeled changes of the Arctic cryosphere demonstrate that even limiting global temperature increases to near 2 °C will leave the Arctic a much different environment by mid-century with less snow and sea ice, melted permafrost, altered ecosystems, and a projected annual mean Arctic temperature increase of +4 °C. Second, even under ambitious emission reduction scenarios, high-latitude land ice melt, including Greenland, are foreseen to continue due to internal lags, leading to accelerating global sea level rise throughout the century. Third, future Arctic changes may in turn impact lower latitudes through tundra greenhouse gas release and shifts in ocean and atmospheric circulation. Arctic-specific radiative and heat storage feedbacks may become an obstacle to achieving a stabilized global climate. In light of these trends, the precautionary principle calls for early adaptation and mitigation actions.

The European Space Agency's Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies of the CMB over the whole sky, with unprecedented sensitivity ( T T 2 10 -6 ) and angular resolution (5 arcmin). Planck will provide a major source of information relevant to many fundamental cosmological problems and will test current theories of the early evolution of the Universe and the origin of structure. It will also address a wide range of areas of astrophysical research related to the Milky Way as well as external galaxies and clusters of galaxies. The ability of Planck to measure polarization across a wide frequency range (30-350 GHz), with high precision and accuracy, and over the whole sky, will provide unique insight, not only into specific cosmological questions, but also into the properties of the interstellar medium. This paper is part of a series which describes the technical

This paper deals with power fluctuations from wind farms. The time range in focus is between one minute and up to a couple of hours. In this time range, substantial power fluctuations have been observed during unstable weather conditions. A wind power fluctuation model is described, and measured time series from the first large offshore wind farm, Horns Rev in Denmark, are compared to simulated time series. The comparison between measured and simulated time series focuses on the ramping characteristics of the wind farm at different power levels and on the need for system generation reserves due to the fluctuations. The comparison shows a reasonable agreement between simulations and measurements, although there is still room for improvement of the simulation model.

Relying on generation side alone is deemed insufficient to fulfill the system balancing needs for future Danish power system, where a 50% wind penetration is outlined by the government for year 2025. This paper investigates use of the electricity demand as frequency controlled reserve (DFR), which has a high potential and can provide many advantages. Firstly, the background of the research is reviewed, including conventional power system reserves and the demand side potentials. Subsequently, the control logics and corresponding design considerations for the DFR technology have been developed and analyzed, based on which simulation models have been built using the DIgSILENT Power Factory. The simulation studies of different scenarios confirm that the DFR can provide reliable performance of frequency control. Furthermore, relevant issues regarding implementing DFR in reality have been discussed.

Abstract Spectra of atmospheric turbulence recently measured at various heights and sites under a variety of stability conditions have been analysed and compared. The results are: In regions over which the spectra obey −5/3 power laws, the ratio of the lateral to the longitudinal spectra shows fair agreement with the 4/3 ratio predicted by the Kolmogorov hypothesis for the inertial sub‐range. The vertical‐longitudinal ratio has a similar tendency. Dissipation rates computed from the longitudinal spectra seem to be consistent with the hypothesis that dissipation is balanced by the total production of mechanical and convective turbulent energy, provided that the turbulence is in equilibrium. In transition from rough to smooth terrain, dissipation exceeds the other terms. Vertical‐velocity spectra obey Monin‐Obukhov similarity theory up to a height of about 50 m. Their shapes are reasonably uniform, the major change with stability being a change of scale of the wave number axis, i.e., any characteristic nondimensional wave number is a function of z / L only. This function appears to be the same as the relation between the normalized dissipation and z / L . These results are consistent with previously measured Kolmogorov constants and with measured ratios of standard deviation of vertical velocity to friction velocity. Up to about a height of 50 m the wavelengths of the maxima of the logarithmic spectra increase linearly with height and more slowly thereafter, up to about 300 m. The spectra in stable air above 50 m suggest the existence of a buoyant sub‐range. Longitudinal spectra do not obey similarity theory in a number of ways. The wavelengths do not scale with height, and there may be differences between sites when the spectra are plotted in similarity coordinates. Spectra over the sea seem to have relatively more energy at low frequencies than those over land.

Abstract After several decades of theoretical developments, desk studies, experimental wind turbines and prototype wind farms, the first large‐scale commercial developments of offshore wind farms are now being built. To support and accelerate this development, the European Commission funded a project, ‘Concerted Action on Offshore Wind Energy in Europe’ (CA‐OWEE), which aimed to gather, evaluate, synthesize and distribute knowledge on all aspects of offshore wind energy, including offshore technology, electrical integration, economics, environmental impacts and political aspects. The partners are from a wide range of fields and include developers, utilities, consultants, research institutes and universities. This article reports on the final conclusions of this project, with the complete report being available online at http://www.offshorewindenergy.org . Copyright © 2003 John Wiley & Sons, Ltd.

International technology transfer is central to the debate about how to curb the carbon emissions from rapid economic growth in China and India. But given China and India's great progress in building innovation capabilities and green industries, how relevant is technology transfer for these countries? This paper seeks insights from three green technology sectors in both countries: wind power, solar energy and electric and hybrid vehicles. We find that, conventional technology transfer mechanisms such as foreign direct investments and licensing, were important for industry formation and take-off. However, as these sectors are catching up, new ‘unconventional technology transfer mechanisms’ such as R&D partnerships and acquisition of foreign firms have become increasingly important. We argue that there is limited practical and analytical mileage left in the conventional approach to technology transfer in these sectors in China and India. We argue that the emphasis should shift from transfer of mitigation technology to international collaboration and local innovation.

The offshore wind industry currently relies on subsidy schemes to be competitive with fossil-fuel-based energy sources. For the wind industry to survive, it is vital that costs are significantly reduced for future projects. This can be partly achieved by introducing new technologies and partly through optimization of existing technologies and design methods. One of the areas where costs can be reduced is in the support structure, where better designs, cheaper fabrication and quicker installation might all be possible. The prevailing support structure design is the monopile structure, where the simple design is well suited to mass-fabrication, and the installation approach, based on conventional impact driving, is relatively low-risk and robust for most soil conditions. The range of application of the monopile for future wind farms can be extended by using more accurate engineering design methods, specifically tailored to offshore wind industry design. This paper describes how state-of-the-art optimization approaches are applied to the design of current wind farms and monopile support structures and identifies the main drivers where more accurate engineering methods could impact on a next generation of highly optimized monopiles.

Abstract This paper deals with modelling of power fluctuations from large wind farms. The modelling is supported and validated using wind speed and power measurements from the two large offshore wind farms in Denmark. The time scale in focus is from 1min to a couple of hours, where significant power fluctuations have been observed from these wind farms. Power and wind speed are measured with 1s sampling time in all individual wind turbines in almost 1 year, which provides a substantial database for the analyses. The paper deals with diversified models representing each wind turbine individually and with aggregation of a wind farm to be represented by a single large wind turbine model. Copyright © 2007 John Wiley & Sons, Ltd.

Abstract Detailed knowledge of mean wind speed profiles is essential for properly assessing the power output of a potential wind farm. Since atmospheric stratification plays a crucial role in affecting wind speed profiles, obtaining a detailed picture of the climatology of stability conditions at a given site is very important. In the present study, long time series from offshore measurement sites around Denmark are analysed, with the aim of quantifying the role of atmospheric stability in wind speed profiles and in our ability to model them. A simple method for evaluating stability is applied, and the resulting statistics of the atmospheric stratification is thoroughly studied. A significant improvement in the mean wind speed profile prediction is obtained by applying a stability correction to the logarithmic profiles suitable for neutral conditions. These results are finally used to estimate power densities at different heights. Copyright © 2004 John Wiley & Sons, Ltd.

As renewable energy sources increase their penetration, the traditional providers of frequency regulation service, i.e., fossil fueled thermal power plants, will be displaced, motivating the search for novel providers such as demand-side resources. This paper presents the results of field experiments using demand as a frequency controlled reserve (DFCR) on appliances with programmable thermostats. The experiments conducted showed the response of a population of thermostatically controlled loads acting as normal reserves (up and down regulation) and disturbance reserves (up regulation only) as defined by the Nordic Grid Codes . In addition, industrial pump loads and relay-controlled loads were tested as DFCR. The tests show that a population of refrigerators was able to deliver frequency reserves approximately equal to their average power consumption. Electric space heaters in the autumn season were able to provide frequency reserves of a magnitude 2.7 times their average power consumption.

OBJECTIVE: To investigate the cognitive functioning of migraineurs vs nonmigraineurs in a large population-based sample of middle-aged twins where headache diagnoses were established by neurologists. METHODS: Twins identified through the population-based Danish Twin Registry participated in face-to-face structured interviews, which included cognitive tests and two previously validated questions screening for migraine. Twins who screened positive for migraine and their co-twins were invited to participate in a telephone-based interview conducted by neurologists, who established headache diagnoses according to the International Headache Society criteria. Cognitive scores on fluency, digit span, delayed word recall, and symbol digit substitution test were compared between migraineurs and nonmigraineurs. Comparisons within monozygotic and dizygotic same sex twin pairs discordant for migraine were also performed. RESULTS: Of the 1,789 twins who were eligible for inclusion in the present study, 1,393 (77.8%) were interviewed. A diagnosis of migraine was established in 536 twins (migraine without aura n = 347; migraine with aura n = 157). Average scores on cognitive tests in twins with migraine or one of the migraine subtypes did not differ from those of nonmigraineurs in any of the tests. Comparisons within twin pairs discordant for migraine produced highly comparable results. Adjustment for possible confounders and stratification by cumulated number of lifetime attacks did not influence the results. CONCLUSIONS: A lifetime diagnosis of migraine was not associated with cognitive deficits in middle-aged subjects.

Decarbonising the heating sector is one of the key elements to realizing the ambitious dual carbon goals of China, which is the largest carbon emitter and energy consumer globally. Currently, district heating (DH) systems have penetrated approximately 88% of the urban heating areas in Northern China. Nevertheless, around 90% of the heating demand in China still relies on fossil fuels. A larger scale integration of renewable energy and waste heat (REWH) sources into the DH systems is critical for decarbonising the entire heating sector in China. However, a deeper level of comprehension is required to harness its full potential. This paper provides a thorough investigation of the status, potential, and national policy schemes of REWH in the DH systems of China. Combined with a critical review of recent literature on relevant areas published in both international and Chinese domestic sources, the trends, challenges, and future perspectives are discussed from scientific research and practical implementation aspects. This paper highlights the synergy of the integration of REWH in DH, the energy efficiency improvements as well as the use of thermal storage technologies through the implementation of 4th generation district heating and smart energy systems that could offer a more economically viable pathway forward.

As the share of VRE (variable renewable energy) has grown rapidly, curtailment issues have arisen worldwide. This paper evaluates and compares curtailment situations in selected countries using an objective and quantitative evaluation tool named the “C-E map” (curtailment-energy share map). The C-E map is a correlation map between curtailment ratios that mean curtailed wind (or solar) energy per available energy and energy shares of wind (or solar). The C-E map can draw a historical trend curve in a given country/area, as an at-a-glance tool to enable historical and/or international comparison. The C-E map also can classify the given countries/areas into several categories, according to the current levels of curtailment ratio and historical trends. The C-E map helps institutional and objective understanding of curtailment for non-experts including policy makers.

<i>Planck<i/> is a scientific satellite that represents the next milestone in space-based research related to the cosmic microwave background, and in many other astrophysical fields. <i>Planck<i/> was launched on 14 May of 2009 and is now operational. The uncertainty in the optical response of its detectors is a key factor allowing <i>Planck<i/> to achieve its scientific objectives. More than a decade of analysis and measurements have gone into achieving the required performances. In this paper, we describe the main aspects of the <i>Planck<i/> optics that are relevant to science, and the estimated in-flight performance, based on the knowledge available at the time of launch. We also briefly describe the impact of the major systematic effects of optical origin, and the concept of in-flight optical calibration. Detailed discussions of related areas are provided in accompanying papers.

The word flexibility is central to Smart Grid literature, but to this day a formal definition of flexibility is still pending. This paper present a taxonomy for modeling flexibility in Smart Grids, denoted Buckets, Batteries and Bakeries. We consider a direct control Virtual Power Plant (VPP), which is given the task of servicing a portfolio of flexible consumers by use of a fluctuating power supply. Based on the developed taxonomy we first prove that no causal optimal dispatch strategies exist for the considered problem. We then present two heuristic algorithms for solving the balancing task: Predictive Balancing and Agile Balancing. Predictive Balancing, is a traditional moving horizon algorithm, where power is dispatched based on perfect predictions of the power supply. Agile Balancing, on the other hand, is strictly non-predictive. It is, however, explicitly designed to exploit the heterogeneity of the flexible consumers. Simulation results show that in spite of being non-predictive Agile Balancing can actually out-perform Predictive Balancing even when Predictive Balancing has perfect prediction over a relatively long horizon. This is due to the flexibility-synergy-effects, which Agile Balancing generates. As a further advantage it is demonstrated, that Agile Balancing is extremely computationally efficient since it is based on sorting rather than linear programming.

It is now over 20 years since the seminal paper on energy law as a discipline was published. The aim of this article is to review what currently constitutes energy law after this 20-year hiatus. There are two main ambitions of this article, which we hope will have a similar impact on the field. The first is to develop for scholars and practitioners a view of what constitutes energy law—and to make this accessible to both law and non-law energy scholars. The second is to advance a set of core principles that guide energy law, in essence a treatise for energy law. We advocate for a paradigm shift in our current understanding of what constitutes energy law. We advance that it should revolve around this set of guiding principles; however, we acknowledge that to some degree it is perhaps not a paradigm shift due to the current absence of any core principles of energy law. Nevertheless we argue that in our advancing of a guiding set of principles we set out a new path for the study of energy law and thus we aim to change what constitutes energy law and challenge the assumptions of existing researchers as globally society moves towards a transition to low-carbon economies.

As Denmark progresses towards a carbon neutral future, energy system models are required to address the challenges of the energy transition. This article describes design, input data and current usage of TIMES-DK, the first Danish energy system model that includes the complete national energy system, covering long-term technology investments. The article aims at explaining the modelling approach; highlighting strengths and reflecting upon limitations of the model; illustrating possible applications of TIMES-DK and inspiring new model developments. Some of the key strengths of the model include simultaneous optimisation of operation and investments across the complete energy system over the whole modelling horizon, explicit representation of the most important sectors of the economy, modular structure and the possibility of linking to a computable general equilibrium model for an additional insight on, e.g. public finance or CO2-leakage. TIMES-DK is being developed in close collaboration between an energy agency, a university and a consulting firm, to improve its robustness, relevance and impact on policy making. It allows for a wide range of applications including exploratory energy scenarios and policy analysis. To meet challenges of the future, further development of the model is needed and consequently the article provides references to ongoing projects addressing current development needs, such as improved representation of transport and flexible handling of the temporal dimension. To support a democratic and transparent process around decisions for the future Danish energy system, TIMES-DK should become available to interested parties. Keywords: Energy systems analysis, TIMES model, Denmark, Model description, Model application, Energy transition