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Heat production from a geothermal energy source is gaining increasing attention due to its potential contribution to the decarbonization of the European energy sector. Obtaining representative results of the environmental performances of geothermal systems and comparing them with other renewables is of utmost importance in order to ensure an effective energy transition as targeted by Europe. This work presents the outputs of a Life Cycle Assessment (LCA) performed on the Rittershoffen geothermal heat plant applying guidelines that were developed within the H2020 GEOENVI project. The production of 1 kWhth from the Rittershoffen heat plant was compared to the heat produced from natural gas in Europe. Geothermal heat production performed better than the average heat production in climate change and resource use, fossil categories. The LCA identified the electricity consumption during the operation and maintenance phase as a hot spot for several impact categories. A prospective scenario analysis was therefore performed to assess the evolution of the environmental performances of the Rittershoffen heat plant associated with the future French electricity mixes. The increase of renewable energy shares in the future French electricity mix caused the impact on specific categories (e.g., land use and mineral and metals resource depletion) to grow over the years. However, an overall reduction of the environmental impacts of the Rittershoffen heat plant was observed.

Purpose Microalgae are considered a promising source of bioenergy and high value-added products that could help face the rising demand for energy and raw materials. However, microalgae systems entail consumption of materials and energy, with potential environmental, economic, and social costs. While environmental and economic impacts have been analyzed in the literature, the social dimension has been barely explored. In this article, social life cycle assessment (S-LCA) is applied to identify the main contributors to social risks. Methodology In this paper, an approach is proposed and applied to exploit outcomes of a Life Cycle Costing (LCC) study as the input data to model and evaluate the potential social impacts of microalgae biorefinery schemes. Such approach helps ensure the consistency between the economic and social assessments, while facilitating data gathering in a context of data scarcity typical of an emerging technology. Priority levels for stakeholder categories and impact subcategories have been assigned based on the literature. Workers and local communities were identified as the stakeholders with the highest priority, related to impact subcategories such as health and safety issues and fair salary for the former and local employment for the latter. An inventory model was built, using PSILCA database v2.0 Starter and openLCA software, together with cost estimates from an LCC using real data from experiments at lab and pilot scale. Results According to the results, the main contribution to social risks of the biogas production is expected to be linked to the anaerobic digestion. Some contributors, both from the cultivation and the anaerobic digestion, are basic chemicals production and market public sewage activities, together with civil engineering and construction, and metal products and machinery production. The geographical distribution of risks depends on the stakeholder category and impact subcategory. Since many activities of the value chain are assumed to happen in Spain, a non-negligible part of social risks take place there. However, other countries with minor contributions to total working time are found to have the highest social risk for subcategories and indicators such as fatal accidents. Finally, three scenarios have been compared, considering production in a Chinese, French, or Spanish context, which lead to significant differences. Conclusions This study aims to highlight the importance of assessing the different dimensions of sustainability in a coherent manner. Furthermore, it provides useful information and hints on main contributors to potential social impacts in the microalgae-based sector based on available information and generic S-LCA databases, and their dependence on geographical locations of the life cycle activities. Despite limitations, conducting such social assessments with available tools is key to better understand the need for widening the scope of sustainability studies.

Purpose Life cycle assessment (LCA) is a robust approach to estimate the environmental impacts of an offshore wind farm (OWF). However, methodological hurdles remain, particularly the lack of appropriate indicators to assess ecosystem impacts during OWF construction and operation and the scarcity of marine ecological data. To address the lack of indicators, this article focuses on developing an impact indicator specifically related to bird collision with OWFs. Methods To assess bird collisions during the operation of OWFs, we adapted a life cycle impact indicator originally developed for onshore wind farms. This indicator combines spatial data on bird species distribution and vulnerability to collisions with OWF technical characteristics (number of turbines, power production, rotor diameter). Results The results model and map seabird collisions at OWF worldwide and introduce a biodiversity impact characterization factor into LCA. The results are expressed as the potentially disappeared fraction of species (PDF) annually per gigawatt-hour (GWh) and vary between 2.0e −15 and 1.69e −13 PDF.year/GWh. It correlates 1344 bird species distribution with the locations of 226 operational and 181 planned OWFs. The spatial differentiation of the characterization factors highlights the OWF collision impact variability worldwide. Such mapping is crucial for identifying areas with varying levels of risk, which is essential for the strategic planning of OWFs. Projections indicate higher potential collision risks in Asia than in Europe, and future expansion of the OWF into new regions with higher collision potential is expected to increase collision risks. In addition, the main factors affecting collision intensity were statistically identified. Therefore, to mitigate collisions, it is essential to focus on three key aspects: fewer turbines, smaller rotors, and greater distance from the shoreline. In addition, the LC-IMPACT method was employed to compare the collision impacts for two OWF projects in France, with those resulting from climate change. Over the lifetime of these OWFs, the collision impacts are quantified at around 2.0e −7 PDF, where effects attributed to climate change will be six times higher. Conclusions The development of this collision indicator is a first step towards integrating OWF biodiversity impacts into the LCA framework. It also demonstrates how LCA indicators can inform marine spatial planning in the context of marine renewable energy development.

Internal airlift reactors are closed systems considered today for microalgae cultivation. Several works have studied their hydrodynamics but based on important solid concentrations, not with biomass concentrations usually found in microalgae cultures. In this study, an internal airlift reactor has been built and tested in order to clarify the hydrodynamics of this system, based on microalgae typical concentrations. A model is proposed taking into account the variation of air bubble velocity according to volumetric air flow rate injected into the system. A relationship between riser and downcomer gas holdups is established, which varied slightly with solids concentrations. The repartition of solids along the reactor resulted to be homogenous for the range of concentrations and volumetric air flow rate studied here. Liquid velocities increase with volumetric air flow rate, and they vary slightly when solids are added to the system. Finally, liquid circulation time found in each section of the reactor is in concordance with those employed in microalgae culture. [PUBLICATION ABSTRACT]

The Agence Nationale de la Recherche (ANR-EESI) ENERGY ReCOvery from Low Temperature heat sources (ENERCO_LT) project is a waste heat recovery project that aims to reduce energy consumption in industrial gas production sites, by producing electrical power from exothermic processes discharges at low and medium temperature. Two promising thermal sources, consisting of: (i) almost dry gas flow at 165 °C and (ii) moist gas flow at 150 °C with a dew point at 60 °C, were then investigated. In this paper, the challenge was to discern suitable recovery solutions facing resource specificities and their thermodynamic constraints, in order to minimize the overall exergy destruction, i.e., to move up the exergy efficiency of the entire system. In this spirit, different designs, including Organic Rankine Cycles (ORCs) and CO2 transcritical cycles, operating as simple and cascade cycles, were investigated. Combined exergy analysis and pinch optimization was performed to identify the potential of various working fluids, by their properties, to overcome the global irreversibility according to the studied resource. Supercritical parameters of various working fluids are investigated too, and seem to bring promising results regarding system performances.

Single-sided natural ventilation is a free cooling solution which accommodates readily to most office building layouts. However, this technique is often ruled out by building designers since its ability to maintain comfort conditions is difficult to assess. Indeed, the cooling effect of this technique driven by wind and stack effects is highly dependent on outdoor conditions. This article intends to review the techniques of single-sided natural ventilation and the tools available to assess the performance of this technique. Then, the performance of single-sided natural ventilation is assessed for low-energy office buildings in two European climates. The methodology is based on the use of a building energy simulation program coupled with a recently developed correlation for single-sided ventilation. Several cases of office buildings are assessed, taking into account the main factors influencing the natural ventilation potential such as building loads, thermal inertia and orientation. For each building case, the energy-saving potential of a mixed-mode cooling system is analysed compared with the same building case with a full air-conditioning system. The comfort level of non-air-conditioned buildings is then studied for each building case. Finally, the impact of the window type on the performance of single-sided natural ventilation is assessed.

This work deals with the carbon dioxide cycle and emissions from biomass incineration under a hydrogen production context. It is proposed to use the thermal energy obtained by biomass combustion to produce water steam, which afterwards would be converted into hydrogen by high temperature electrolysis (HTE). In France, the thermal energy potential from nonvalorised biomass reaches almost 6.5 Mtep. In this study, the potential avoided carbon emissions are quantified as well as the feasible hydrogen production capacity based on the steam supplied by the incineration units. Results show that carbon consumption in hydrogen production by steam methane reforming (SMR) or biomass incineration–HTE process is almost equivalent between both processes. However, the hydrogen produced by the biomass incineration–HTE process used to fuel vehicles, would lead to a decrease of 135 Mt of carbon from fossil origins yearly, in contrast to SMR.

This paper presents an investigation on alternative approaches to the providing of uncertainty estimates associated to point predictions of wind generation. Focus is given to skill forecasts in the form of prediction risk indices, aiming at giving a comprehensive signal on the expected level of forecast uncertainty. Ensemble predictions of wind generation are used as input. A proposal for the definition of prediction risk indices is given. Such skill forecasts are based on the dispersion of ensemble members for a single prediction horizon, or over a set of successive look-ahead times. It is shown on the test case of a Danish offshore wind farm how prediction risk indices may be related to several levels of forecast uncertainty (and energy imbalances). Wind power ensemble predictions are derived from the transformation of ECMWF and NCEP ensembles of meteorological variables to power, as well as by a lagged average approach alternative. The ability of risk indices calculated from the various types of ensembles forecasts to resolve among situations with different levels of uncertainty is discussed.