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Abstract This work reports a detailed experimental study that is aimed at investigating the Thermal Energy Storage (TES) performance of cementitious systems containing Microencapsulated Phase Change Materials (MPCMs). New spherical-shaped test specimens for TES measurements were produced following an innovative casting technique, developed at the Institut fur Werkstoffe im Bauwesen – TU Darmstadt. Three water-to-cement ratios and three MPCMs volume fractions, leading to a total of nine different mixtures, were investigated. The thermal experiments were accompanied by mechanical tests to observe the effect MPCMs have on the resulting strengths in both compression and bending. The analysis and discussion of the TES results are employed for calibrating an enthalpy-based model. The experimental data have been applied to evaluate the corresponding temperature-based material parameters like specific heat, conductivity, or more in general, the energy storage capacity of a system under transient heat conduction conditions.

Abstract Microgrids integrating local renewable energy sources at low-voltage level show promising potentials in realizing a reliable, efficient, and clean supply of electricity. Further improvements are expected when such a microgrid is operated based on direct current (dc) instead of alternating current (ac) infrastructure for power distribution commonly in use today. Our study aims to systemically quantify the gap between environmental impacts of microgrids at building level using the case study of power distribution within office buildings. For this purpose, a scalable comparative life cycle assessment (LCA) is conducted based on a technical bottom-up analysis of differences between ac and dc microgrids. Particularly, our approach combines the micro-level assessment of required power electronic components with the macro-level requirements for daily operation derived from a generic grid model. The results indicate that the environmental impacts of employed power electronics are substantially reduced by operating a microgrid based on dc power distribution infrastructure. Our sensitivity analyses show that efficient dc microgrids particularly lead to savings in climate change impact emissions. In addition, our study shows that the state-of-the-art scaling rules of power electronics currently used in LCAs leads to inaccurate results. In contrast, the proposed methodology applies a more technical approach, which enables a detailed analysis of the environmental impacts of power electronic components at system level. Thus, it provides the foundation for an evaluation criterion for a comprehensive assessment of technological changes within the framework of energy policy objectives.

Abstract Public participation is often part of planning and decision-making processes relating to the German energy transformation (Energiewende). Factors influencing the active involvement of individuals have not been fully investigated, although these factors may impact the outcome of participatory decision making. However, a few concepts are discussed relating to what kind of people participate in governance processes: political efficacy, place attachment, value orientation, and sociodemographic characteristics. We further assumed that the aspects of attitudes toward renewable energy technologies, general knowledge about environment and energy, specific knowledge about electricity-generating technologies, personality strength, and living situation might influence people's participation in planning and decision making related to energy issues. In this study, we examine the relevance of these concepts based on a survey for which (n=) 2400 respondents were recruited from an access panel to build up a quota sample on the three crossed characteristics: gender, age, and school education. Many of the respondents are aware of participation options but very few become actively engaged in participation processes. The multivariate analyses conducted showed that attitudes towards renewable energy technologies, value orientation towards nature, political efficacy, personality strength, and individuals' specific knowledge have a strong influence on whether someone becomes actively involved or not.

Abstract The impact of the spatial variation of inertial response and fast frequency services has not been fully investigated in power system scheduling models incorporating constraints on network security. This paper demonstrates the importance of acknowledging the variety of local frequency dynamics in the aftermath of a generation loss. It proposes a novel scheduling methodology that enables the system security in all areas of the system thus preventing potential tripping of distributed generation triggered by locally-measured high rates of change of frequency. The proposed methodology highlights the positive contribution to local frequency dynamics from an HVDC link, whose capacity is optimally dispatched to allocate power flow and fast-frequency services. The novel power system scheduling model is applied to analyze a typical 2030 GB low-carbon scenario. Results show that there are changes in the commitment decisions compared to the solution obtained with a one-area formulation when local security is taken into account. These changes translate into additional operational cost.

Solar radiation is the main factor that must be considered when predicting solar systems energy output. Especially in built-up areas the use of Digital Surface Models (DSM) and analysis with Geographic Information Systems (GIS) has gained popularity for these predictions in recent years. However, the identification of small objects and their impact in the shadowing of solar systems is a very important factor that cannot be entirely acquired by models from common available Light Detection and Ranging (LiDAR) data. Thus higher resolutions DSMs are required. These can be generated from photogrammetric point clouds derived from Unmanned Aerial System (UAS) based large scale image flights. This paper presents a comparison between a common available resolution DSM generated from standardized LiDAR data and a DSM with very high resolution from photogrammetric point clouds. The added value of using high-resolution DSMs for solar radiation estimation for PV rooftop-systems is discussed with a focus on elevation, slope, aspect and on the suitability for selection of usable roof-top areas. Although DSMs with resolutions up to 1 cm have been generated, the results show that a DSM of 25 cm is enough for considering all small roof-top objects that are relevant for estimation of solar radiation.

Abstract Offshore cultivation of seaweed provides an innovative feedstock for biobased products supporting blue growth in northern Europe. This paper analyzes two alternative exploitation pathways: energy and protein production. The first pathway is based on anaerobic digestion of seaweed which is converted into biogas, for production of electricity and heat, and digestate, used as fertilizer; the second pathway uses seaweed hydrolysate as a substrate for cultivation of heterotrophic microalgae. As a result the seaweed sugars are consumed while new proteins are produced enhancing the total output. We performed a comparative Life Cycle Assessment of five scenarios identifying the critical features affecting resource efficiency and environmental performance of the systems with the aim of providing decision support for the design of future industrial scale production processes. The results show that all scenarios provide environmental benefits in terms of mitigation of climate change, with biogas production from dried Laminaria digitata being the most favorable scenario, quantified as −18.7*10 2 kg CO 2 eq./ha. This scenario presents also the lowest consumption of total cumulative energy demand, 1.7*10 4 MJ/ha, and even resulting in a net reduction of the fossil energy fraction, −1.9*10 4 MJ/ha compared to a situation without seaweed cultivation. All scenarios provide mitigation of marine eutrophication thanks to bioextraction of nitrogen and phosphorus during seaweed growth. The material consumption for seeded lines has 2–20 times higher impact on human toxicity (cancer) than the reduction achieved by energy and protein substitution. However, minor changes in cultivation design, i.e. use of stones instead of iron as ballast to weight the seeded lines, dramatically reduces human toxicity (cancer). Externalities from the use of digestate as fertilizer affect human toxicity (non-cancer) due to transfer of arsenic from aquatic environment to agricultural soil. However concentration of heavy metals in digestate does not exceed the limit established by Danish regulation. The assessment identifies seaweed productivity as the key parameter to further improve the performance of the production systems which are a promising service provider of environmental restoration and climate change mitigation.

Changes in the concentration and spectral absorption of chromophoric dissolved organic matter (CDOM) may strongly condition the optical properties of tropical and subtropical water bodies. We examined the spatial distribution of CDOM-related absorption, spectral slope and vertical attenuation of solar radiation in two shallow lakes in the Esteros del Iberá wetland system. In situ measurements were made to examine spatial variations in photobleaching yields in natural lake conditions. The results showed that "fresh" allochthonous CDOM is more susceptible to phototransformations than either "aged" allochthonous organic matter or autochthonous sources, if the distances from sources are considered as proxies for residence time. Based on measured changes in absorption spectral slope in relation to solar ultraviolet irradiance, a model was developed which used CDOM as a non-conservative tracer of water masses. Spatial changes in CDOM absorption within the lake were then used to compare photo related transformations to those associated with conservative mixing.