• Energy Research
• 2016-2025close
• 7. Clean energy close
• Renewable Energy close

Abstract Compared with other traditional energy sources, renewable energy, which results the less pollution and has numerous resources, is a significant factor in addressing the current issues of the serious environmental pollution and the resource depletion. Large-scale renewable energy integrated to the grid could bring change in both morphological structure and operation modes of energy transmission. Therefore, it is necessary to research the evolution mechanism of the future transmission network with a high proportion of the renewable energy. In this paper, an evolution framework of power system with high proportion of renewable energy is proposed. Firstly, a network equivalence and simplification based on power transfer distribution factors (PTDFs) is proposed, which can effectively simplify the decision-making process of evolution of large-scale power system. Then, an annual production simulation (8760 h) which takes into account renewable energy and load fluctuations is used to find out the bottleneck of the power grid. Based on the above methods, evolution strategy of power system with high proportion of renewable energy is studied for finding out optimal expansion strategy. A real power system of Zhejiang province is used as a test system. Test results demonstrate the feasibility of the proposed evolution framework.

Abstract In this paper, the charging/melting of phase change materials (PCM) in thermal energy storage is discussed. An oil-driven system is considered in which oil acts as a heat-transfer fluid while solar salt (KNO3 – NaNO3) is used as a PCM. The aim of this study is to analyze the influence of increasing the number of heat transfer fluid HTF tubes during the charge cycle as a geometrical factor. The effect of changing inlet temperature is also examined. Four cases of geometric configurations are analyzed in this research in order to understand the effect of increasing the number of HTF tubes on the total melting time of PCM. Moreover, three inlet temperature conditions are considered to study their influences on melting time. Results indicate that by increasing the number of HTF tubes, total melting time of PCM decreases as it liquefies in four tube cases in almost 165 min, as compared with a single tube which took 234 min to completely melt. Furthermore, inlet temperature plays an essential role in reduction of total melting time.

Abstract This literature review was built upon recently published articles on Life Cycle Assessments (LCAs) of agricultural biogas plants, to: enhance understanding of the relevant literature in the field and the related question by readers worldwide. It was designed to highlight methodological issues and impact indicators, which best represent this research field; consequently, they should be considered in performing environmental assessments of agro-biogas derived energy systems. The literature review highlighted the wide variability of environmental results due to the ways the feedstock mixtures were produced, managed, and supplied; and due to the regions in which the anaerobic digesters were located and operated. Differences were found to be related to the aim and function of the study and to the methodological approach used, especially for the development of the environmental impact assessments. Other differences resulted from the ways the energy produced was utilised, whether it was used as an input to the natural gas national grid, and/or if it was used within the production system. The authors of this review concluded that, although much progress has been made, many unsolved challenges and methodological choices must be addressed to further improve the robustness of LCA in relation to AD and to related approaches.

Abstract This paper proposes a new methodology for determining the geometrical parameters and the optimal distribution of small-scale linear Fresnel reflectors on flat roofs of urban buildings. This engineering problem is highly complex as it involves 21 variables; in contrast to present-day studies available in the literature, our method provides a global solution. The algorithm involves several stages, in which it uses multiple objective functionals: maximization of the used area of the roof, minimization of the cost, minimization of losses. The solution found by this method combines all the relevant aspects from the technical and/or economic point of views and obtains, as the final objective, the maximization of the absorbed annual energy for the stated problem.

Abstract A recently proposed analytical wake model for a horizontal axis utility scale wind turbine is revisited, and revised and improved. The model is based upon conservation of momentum in the context of actuator disc theory, and the assumption of a distribution of the double-Gaussian type for the velocity deficit in the wake. The model is developed and improved and reveals characteristics of the wind turbine wake velocity deficit for the full wake, including the near-wake to within close proximity of the wind turbine rotor. Full 2-dimensional model fitting to lidar wake measurement data obtained from a 5 MW utility scale wind turbine is carried out for the full range of inflow wind velocities of primary interest. Such a full wind turbine wake model has the potential to facilitate analytic calculations within the wind turbine wake region, and the potential to improve understanding of wind turbine aerodynamics.

Abstract Solar energy, as main energy supply that sustains life on Earth, is also an unavoidable component of the complex strategy in achieving a clean and fair energy transition and goals for sustainable development by 2030. The present work studies the potential of installing Photovoltaic Distributed Generation at Universidad Politecnica de Madrid – Ciudad Universitaria campus. To this end, the study focuses on the electricity generation, carbon reduction and economic feasibility of solar photovoltaic systems installation using and comparing two different approaches based on data input with different time resolution, simulation software and level of details. Results show that the optimal photovoltaic power that maximizes emissions savings also ensures the best economic return, and in addition coincides with the maximum solar potential of the Campus, which is about 3.3 MW. At campus level, approximately 77% of the photovoltaic electricity production would be consumed locally, which would suppose a coverage of about 40% of the total electricity consumption. Emissions savings could reach 30% and an in-depth economic analysis indicates that the project is highly profitable. These results and methodology could be used to assess the feasibility of photovoltaic systems at other universities and help entities study the solar potential of their buildings.

Abstract Wind climate analysis and modelling is of most importance during site selection for offshore wind farm development. In this regard, reliable long-term wind data are required. Buoy measurements are considered as a reference source in relevant applications including evaluation and calibration of wind data obtained from less reliable sources, combined assessment, blending and homogenization of multi-source wind data, etc. Most of these applications are based on regression techniques elaborated by using the principle of ordinary least squares (OLS). However, wind data usually contain several outliers, which may question the validity of the regression analysis, if not properly considered. This study is focused on the implementation of the most important robust regression methods, which can identify and reveal outliers, and retain at the same time their efficiency. Long-term reference wind data series obtained from buoys at six locations in the Mediterranean Sea are used to calibrate hindcast (model) wind data by applying robust methods and OLS. The obtained results are compared according to several statistical measures. The effects of the calibration methods are also assessed with respect to the available wind power potential. The results clearly suggest that least trimmed squares and L1-estimator perform in all respects better than OLS.

Abstract Standardization of biogas technology is immensely important for the promotion of the biogas industry worldwide. China has built a complete biogas standard system, which is divided into common, household biogas, biogas engineering, biogas digester for domestic sewage treatment, output utilization, and service system standards. The problems and potential barriers for biogas standardization in China are analyzed and come down to sluggish standard, overlapped standard, government-dominated standard, and lagging international standard. Accordingly, all potential biogas standards should be evaluated and placed under the same department. China Biogas Society and China Association of Rural Energy Industry play leading roles in developing enterprise or group/association biogas standards and ISO biogas standards. The bio-natural gas standard system and experimental standardization should be developed as well to replenish biogas standard system. A paradigm shift in biogas standardization should be from government-dominated to market-oriented model. The lessons learned for other developing countries includes expanding standardization to multi-aspects to realize full lifecycle control and management, building rapid responding mechanism of standardization to adopt industry transformation, integrating outdated standards into new versions, and establishing market-based standard system.

An algorithm to optimise the number of solar panels and battery size to meet the water demands of an installation has been developed. The algorithm adjusts for seasonal changes in energy use and production in a pressurized irrigation network and production in an off-grid solar panel system. By using this algorithm, we aim to create an efficient and sustainable irrigation system by reducing the infrastructure and reliance on the power grid. This method can enhance irrigation systems in far-off regions, strengthen their endurance, and promote sustainable energy in farming and water administration. This work was supported by the project “Hi-Edu Carbon”"Erasmus Plus Programme, Key Action KA22021, action type (2021-1-SK01-KA220-HED-000023274.