Web tool for energy policy decision-making through geo-localized LCA models: A focus on offshore wind farms in Northern Europe

International audienceEnvironmental performances of electricity generation, expressed as environmental impacts per kWh of electricity produced, depend strongly on technical, methodological and geographical parameters. When considering the global environmental performances of renewable energies, a geo-dependent life cycle assessment (LCA) taking into account geographical issues is of high interest. To illustrate this issue, a web map service enabling "geolocalized life cycle assessment" of offshore wind farms for different configurations has been developed. Based on a modular LCA model and on collaborative works made within the framework of the FP7 co-funded project EnerGEO, the developed tool should help decision makers in assessing the global environmental impacts caused by an offshore wind farm in Northern Europe

Environmental data for the planning of off-shore wind parks from the EnerGEO Platform of Integrated Assessment (PIA)

International audienceThe EU-sponsored EnerGEO project aims at providing decision makers with a modelling platform to assess the environmental impacts of different sources of renewable energy. One of the pillars of the project is the Wind Energy Pilot, addressing the effects of offshore wind parks on air pollution and energy use. The methods used in the pilot and the underlying environmental databases are integrated into a WebGIS client tool and made available to the public. This paper is dedicated to describing the environmental databases and supporting data incorporated in the client tool. A 27-km resolution, 11-year wind database is created using the WRF model. The wind database is used to assess the wind climate in the north-west Atlantic region and to derive the potential power output from offshore wind parks. Auxiliary data concerning water depth, distance to shore and distance to the nearest suitable port are created to aid the planning and maintenance phases. Seasonal workability conditions are assessed using a 20-year wave database. The distance at which future wind parks should be placed to exhibit different wind climates is investigated

On the evolution of sea surface temperature in the tropical Pacific

The aim of this thesis is to improve our understanding of El Niño, by using recently available observational datasets to analyze and verify mechanisms that drive El Niño. A secondary goal is to improve model simulations of El Niño, which can lead to improved forecasts. Chapter 2 gives an analysis of how changes in SST are related to thermocline depth variability. There is a time delay between a local thermocline depth anomaly and the resulting SST anomaly at the surface. It is shown that the delay varies with longitude. Two important pathways are distinguished that cause the relation between thermocline depth and SST. The upwelling pathway (involving kelvin waves, upwelling and mixing) is found to be dominant in the eastern Pacific, approximately east of 140°W. The wind coupling pathway (involving convection, mixing and evaporation) is dominant west of 140°W. Chapter 3 analyzes the mechanisms that are important for the development of SST anomalies in the western equatorial Pacific, the warm pool region. In a budget study it is shown how SST anomalies propagate zonally from the western Pacific to the central/ eastern Pacific and back during the development and decay of an El Niño event. An analysis of the mixed layer heat budget in an ocean model simulation shows that both zonal wind anomalies (anomalous upwelling and zonal advection) and wind speed anomalies (anomalous latent heat flux and changes in mixed layer depth) are important. Eastward propagation of SST anomalies during the growth phase of El Niño is caused partially by a reduction of the mixed layer depth east of the SST anomaly, and partially by zonal advection. Westward propagation during the decay phase is caused by warming in the western Pacific through mean zonal advection across an anomalous temperature gradient, and radiative cooling east of the SST anomaly. The theme of chapter 4 is the question "How does El Niño change under the influence of human induced global warming?". An analysis of 62 coupled ocean-atmosphere model simulations over the period 1940-2080 shows no significant changes in ENSO characteristics, despite a simulated global average warming of ∼ 1.2K. A detailed investigation is performed to find out if flaws in the model used for the simulation are responsible for the insensitivity of El Niño to global warming. The model behavior is found to be qualitatively similar to that of a stable system driven by stochastic noise. The zonal wind response to SST anomalies in the equatorial Pacific is shown to be insensitive to changes in background SST. The zonal wind response pattern is too narrow around the equator, which leads to a more stable system, insensitive to changes in background temperature. Concluding, model deficiencies make the model insensitive to global warming. It is necessary to analyze and improve coupled general circulation models with respect to these deficiencies before they can be used answer the questions whether and how ENSO will change due to global warming. Chapter 5 discusses the results found in chapters 2,3 and 4 and provides a summary of the conclusions

Evaluating the Robustness of EGNSS Based Timing Services

This paper proposes a set of Key Performance Indicators (KPIs) for European GNSS (EGNSS)-based timing services that are relevant from the user perspective; these KPIs quantify the accuracy, integrity, and stability of the services. Furthermore, the instrumentation and procedures required for reproducing the threats and evaluating the proposed KPIs are described. The proposed test setup makes use of a precise time/frequency reference distributing a Coordinated Universal Time (UTC) realization and is intended for post-processing. The test results provide an indication of the performance of the envisioned Galileo and EGNOS timing services in terms of the proposed KPIs when the receiver is subject to various abnormal conditions

Performance of EGNSS-based Timing in Various Threat Conditions

Today’s society is highly reliant on time and frequency synchronization, for example in communications systems and financial networks. Precise timing is more and more derived from satellite navigation receivers, which are unfortunately very susceptible to various signal threats. We studied the performance of Global Navigation Satellite System (GNSS) timing under different operating conditions, and tested the effectiveness of different techniques that improve timing receiver robustness. These features were tested under various threat scenarios related to specific vulnerabilities in GNSS-based timing, such as interference and navigation message errors, and their efficiency was analyzed against corresponding scenarios. We found that interference or meaconing-type spoofing can threaten GNSS timing, but can be detected by means of automatic gain control (AGC) and carrier-to-noise ratio based methods. GNSS interruptions due to interference can be bridged by a local oscillator holdover technique based on a Kalman filter whose parameters are based on a GNSS time solution. Navigation message errors are mitigated by the European Geostationary Navigation Overlay Service (EGNOS), and constellation-wide timing errors can be detected by the use of a dual-constellation (GPS-Galileo) cross-check. Dual-frequency operation for timing, in addition to mitigating first-order ionospheric effects, was found to be more robust to interference with the option to fall back to single frequency.fi=vertaisarvioitu|en=peerReviewed

Receiver-Level Robustness Concepts for EGNSS Timing Services

GNSS-based time transfer is utilized in various critical infrastructures as it provides important advantages which are being increasingly exploited. In this paper, we present the various implementation options for robust timing service concepts based on European GNSS (EGNSS), i.e., Galileo and EGNOS, that are expected to further foster the use of EGNSS timing; this concept can make use of the redundancy of measurements and of available GNSS constellations. The stability properties of the local oscillator, which are known to the designer, are also exploited. The algorithms are developed to account for cases where several measurement faults occur simultaneously, which is a possible scenario in land-based reception conditions. Furthermore, we derive time protection level equations to quantify the integrity of the GNSS time solution as a function of the false alarm and missed detection probabilities as well as the maximum number of simultaneous outliers to be accounted for. Some of the considered fault scenarios can only be detected but not rectified by the algorithms: in such case, holdover, i.e. processing based on the local oscillator alone, is triggered. Thus, the performance in these scenarios is dependent on the stability of the local oscillator; in this paper, the analysis is based on a low-cost temperature-compensated crystal oscillator. The effect of the robustness concepts is illustrated with a set of experiments which show that when implemented in a timing GNSS receiver, the algorithms presented can deal with failures that affect individual satellites or even an entire constellation. Local disturbances affecting the receiver can also be effectively detected. Specifying EGNSS timing as proper services along with well-defined procedures for testing receiver compliance paves the road for standardizing and certifying robust EGNSS timing receivers, which would be beneficial for many applications and in particular in safety or liability critical use cases