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Topic Review
Energy Poverty
The term “energy poverty” usually refers to the lack of affordability or of access to basic energy services to meet one’s most common needs, such as lighting, cooking, heating and cooling.
  • 3.1K
  • 15 Oct 2021
Topic Review
Nafion-Based Membrane
Nafion, a perfluorosulfonic acid proton exchange membrane (PEM), has been widely used in direct methanol fuel cells (DMFCs) to serve as a proton carrier, methanol barrier, and separator for the anode and cathode. A significant drawback of Nafion in DMFC applications is the high anode-to-cathode methanol fuel permeability that results in over 40% fuel waste.
  • 3.1K
  • 20 May 2022
Topic Review
Heat Pump
The Heat Pump (HP) is an environmentally friendly and renewable energy technology that exploits renewable heat energy from the ground, air or water for building or industrial applications by reversing the natural heat flow from a lower to a higher useful temperature. HP technology is commonly classified according to its source, function, type of energy and application. The HPs in cold climate countries are accepted as one of the most outstanding technologies of heating in both residential and commercial buildings, because they provide high seasonal performance factor (SPF), 1.8–3.4 for air source heat pump (ASHP) and 2.5–5.6 for ground source heat pump (GSHP) and water source heat pump (WSHP). However, the spread is large, because of different equipment, design and installation quality as well as maintenance. 
  • 3.1K
  • 28 Jan 2022
Topic Review
Hydrogen Economy
Environmental issues make the quest for better and cleaner energy sources a priority. Worldwide, researchers and companies are continuously working on this matter, taking one of two approaches: either finding new energy sources or improving the efficiency of existing ones. Hydrogen is a well-known energy carrier due to its high energy content, but a somewhat elusive one for being a gas with low molecular weight. The so-called "Hydrogen Economy" is based on the use of hydrogen as an energy source. This entry examines the current electrolysis processes for obtaining hydrogen, with an emphasis on alkaline water electrolysis.
  • 3.1K
  • 18 Sep 2021
Topic Review
Grid Code Requirements in Ethiopia
Rapid integration of renewable energy into the electric grid has ramifications for grid management and planning. Therefore, system operators have formulated grid code requirements to ensure that the grid continues to operate in a secure, safe, and cost-effective manner. The current state of grid code in Ethiopia, as well as the need for it, is discussed here. It lays out the technological grid integration requirements, with a focus on small and microgrids, which are especially important for the integration of renewable. 
  • 3.1K
  • 08 Aug 2022
Topic Review
Multilevel Inverters for PV Systems
Over the last decade, energy demand from the power grid has increased significantly due to the increasing number of users and the emergence of high-power industries. This has led to a signifi-cant increase in global emissions with conventional energy generation. Therefore, the penetration of renewable energy resources into the power grid has increased significantly. Photovoltaic sys-tems have become the most popular resources as their protentional is enormous, thus, the world-wide installed PV capacity has increased to more than 635 gigawatts (GW), covering approxi-mately 2% of the global electricity demand. Power electronics are an essential part of photovoltaic generation; the drive for efficient power electronic converters is gaining more and more momen-tum. Presently, multilevel inverters (MLI) have become more attractive to researchers compared to two-level inverters due to their abilities to provide lower electromagnetic interference, higher efficiency, and larger DC link voltages. 
  • 3.1K
  • 23 Mar 2021
Topic Review
Proton Exchange Membrane Fuel Cells
Proton exchange membrane fuel cells (PEMFCs) operate by converting the chemical energy in a fuel into electrical energy. The most crucial parameters in the operation process are the temperature, pressure, relative humidity, and air stoichiometry ratio. The classical structure of a PEMFC consists of a proton exchange membrane, anode electrode, cathode electrode, catalyst layers (CLs), microporous layer (MPLs), gas diffusion layers (GDLs), two bipolar plates (BPs), and gas flow channels (GFCs). The mechanical behavior and the conductivity of the protons are highly dependent on the structure of the MEAs.
  • 3.1K
  • 20 Feb 2023
Topic Review
Redox Flow Batteries
Redox Flow Batteries (RFB) are electrochemical energy storage devices that converts chemical energy into electrical energy through reversible oxidation and reduction of the working fluids. Redox flow batteries are considered by many to be a promising technology for the storage of energy for days or even weeks. Other advantages of RFBs are modularly and the ability to change the output power and energy capacity independently, by changing the size and number of cells in a stack and by adjusting the volume of electrolyte. Also, RFBs show a long lifecycle compared to lithium-ion batteries.
  • 3.1K
  • 14 Oct 2021
Topic Review
CO2 Storage in Shale Reservoirs
As a new “sink” of CO2 permanent storage, the depleted shale reservoir is very promising compared to the deep saline aquifer. To provide a greater understanding of the benefits of CO2 storage in a shale reservoir, a comparative study is conducted by establishing the full-mechanism model, including the hydrodynamic trapping, adsorption trapping, residual trapping, solubility trapping as well as the mineral trapping corresponding to the typical shale and deep saline aquifer parameters from the Ordos basin in China. The results show that CO2 storage in the depleted shale reservoir has merits in storage safety by trapping more CO2 in stable immobile phase due to adsorption and having gentler and ephemeral pressure perturbation responding to CO2 injection. The effect of various CO2 injection schemes, namely the high-speed continuous injection, low-speed continuous injection, huff-n-puff injection and water alternative injection, on the phase transformation of CO2 in a shale reservoir and CO2-injection-induced perturbations in formation pressure are also examined. With the aim of increasing the fraction of immobile CO2 while maintaining a safe pressure-perturbation, it is shown that an intermittent injection procedure with multiple slugs of huff-n-puff injection can be employed and within the allowable range of pressure increase, and the CO2 injection rate can be maximized to increase the CO2 storage capacity and security in shale reservoir.
  • 3.0K
  • 11 Jan 2021
Topic Review
Fuel Cell Hybrid Electric Vehicles
With the development of the global economy, the automobile industry is also developing constantly. In recent years, due to the shortage of environmental energy and other problems, seeking clean energy as the power source of vehicles to replace traditional fossil energy could be one of the measures to reduce environmental pollution. Among them, fuel cell hybrid electric vehicles (FCHEVs) have been widely studied by researchers for their advantages of high energy efficiency, environmental protection, and long driving range.
  • 3.0K
  • 08 Oct 2022
Topic Review
Gaseous and Liquid Fuel Cook-Stove
Clean and efficient cook-stoves and fuels are essential to address energy demand and ensure safe cooking for billions of people across the globe. Currently, nearly 2651 million people in developing countries (Africa—910 million, Asia—1674 million, Central and South America—57 million, and Middle East—10 million) are without clean cooking facilities.
  • 3.0K
  • 03 Feb 2023
Topic Review
Application of Ground Heat Exchangers
Geothermal energy is a widely available, constant source of renewable energy that has shown great potential as an alternative source of energy in achieving global energy sustainability and environment protection. When exploiting geothermal energy, whether is for heating or cooling of buildings, a ground heat exchanger (GHE) is the most important component, whose performance can be easily improved by following the latest design aspects. 
  • 3.0K
  • 26 May 2021
Topic Review
Integrated Photovoltaic-Fuel Cell Systems
Integrated photovoltaic-fuel cell (IPVFC) system uses photovoltaics and fuel cells to majorly generate power and hydrogen, using solar energy as the prime mover. IPVFC amongst other integrated energy generation methodologies are renewable and clean energy technologies that have received diverse research and development attentions over the last few decades due to their potential applications in a hydrogen economy.
  • 3.0K
  • 29 Oct 2021
Topic Review
Hydrogen Fuel Internal-Combustion Engines
To achieve the goals of low carbon emission and carbon neutrality, some urgent challenges include the development and utilization of low-carbon or zero-carbon internal combustion engine fuels. Hydrogen, as a clean, efficient, and sustainable fuel, has the potential to meet the abovementioned challenges. Thereby, hydrogen internal combustion engines have been attracting attention because of their zero carbon emissions, high thermal efficiency, high reliability, and low cost.
  • 2.9K
  • 28 Oct 2022
Topic Review
Photovoltaic Module Degradation
An evaluation of the degradation effects on photovoltaic modules is essential to minimise uncertainties in the system operation. Bifacial photovoltaic technology is attracting attention due to the capacity of generating energy from the front and rear sides. The term degradation is defined as a gradual deterioration of the characteristics of a material, component, or system. This deterioration may cause an impact on the system capacity to operate within the expected limits and therefore impact directly on their operating conditions.
  • 2.9K
  • 07 Dec 2021
Topic Review
Byproduct Oxygen for Green Hydrogen Electrolysis
Water electrolysis for hydrogen production with renewable electricity is regularly studied. The inclusion of byproduct electrolytic oxygen capture and sale is of interest for parallel decarbonisation efforts elsewhere in the industry and could contribute to reducing green hydrogen costs. A deterministic hydrogen electrolysis system model is constructed to compare oxygen inclusion/exclusion scenarios. This uses wind and solar-PV electricity generation timeseries, a power-dependent electrolysis model to determine the energy efficiency of gas yield, and power allocation for gas post-processing energy within each hourly timestep. This maintains a fully renewable (and therefore low/zero carbon) electricity source for electrolysis and gas post-processing. The model is validated (excluding oxygen) against an existing low-cost GW-scale solar-hydrogen production scenario and an existing hydrogen production costs study with offshore wind generation at the multi-MW scale. For both comparisons, oxygen inclusion is then evaluated to demonstrate both the benefits and drawbacks of capture and utilisation, for different scenario conditions, and high parameter sensitivity can be seen regarding the price of renewable electricity.
  • 2.9K
  • 18 Jan 2024
Topic Review
Emerging Thermo-Mechanical Energy Storage Technologies
Thermo-mechanical energy storage can be a cost-effective solution to provide flexibility and balance highly renewable energy systems. Thermo-Mechanical Energy Storage (TMES) can be directly compared with pumped hydro storage because they have similar discharge characteristics and capacity (order of 100 s of MW).
  • 2.9K
  • 13 Sep 2022
Topic Review
Digital Applications in Energy Sector
Digitalization is a transformation process which has already affected many parts of industry and society and is expected to yet increase its transformative speed and impact. In the energy sector, many digital applications have already been implemented. However, a more drastic change is expected during the next decades. Good understanding of which digital applications are possible and what are the associated benefits as well as risks from the different perspectives of the impacted stakeholders is of high importance. On the one hand, it is the basis for a broad societal and political discussion about general targets and guidelines of digitalization. On the other hand, it is an important piece of information for companies in order to develop and sustainably implement digital applications. This entry provides a structured overview of potential digital applications in the German energy (electricity) sector on the basis of a literature review.
  • 2.9K
  • 14 Apr 2021
Topic Review
Gas/Oil-Relative Permeabilities
Thermal recovery processes for heavy oil exploitation involve three-phase flow at elevated temperatures. The mathematical modeling of such processes necessitates the account of changes in the rock–fluid system’s flow behavior as the temperature rises. To this end, numerous studies on effects of the temperature on relative permeabilities have been reported in the literature. Compared to studies on the temperature effects on oil/water-relative permeabilities, studies (and hence, data) on gas/oil-relative permeabilities are limited. However, the role of temperature on both gas/oil and oil/water-relative permeabilities has been a topic of much discussion, contradiction and debate. The jury is still out, without a consensus, with several contradictory hypotheses, even for the limited number of studies on gas/oil-relative permeabilities. This study presents a critical analysis of studies on gas/oil-relative permeabilities as reported in the literature, and puts forward an undeniable argument that the temperature does indeed impact gas/oil-relative permeabilities and the other fluid–fluid properties contributing to flow in the reservoir, particularly in a thermal recovery process. It further concludes that such thermal effects on relative permeabilities must be accounted for, properly and adequately, in reservoir simulation studies using numerical models. The paper presents a review of most cited studies since the 1940s and identifies the possible primary causes that contribute to contradictory results among them, such as differences in experimental methodologies, experimental difficulties in flow data acquisition, impact of flow instabilities during flooding, and the differences in the specific impact of temperature on different rock–fluid systems. We first examined the experimental techniques used in measurements of oil/gas-relative permeabilities and identified the challenges involved in obtaining reliable results. Then, the effect of temperature on other rock–fluid properties that may affect the relative permeability was examined. Finally, we assessed the effect of temperature on parameters that characterized the two-phase oil/gas-relative permeability data, including the irreducible water saturation, residual oil saturation and critical gas saturation. Through this critical review of the existing literature on the effect of temperature on gas/oil-relative permeabilities, we conclude that it is an important area that suffers profoundly from a lack of a comprehensive understanding of the degree and extent of how the temperature affects relative permeabilities in thermal recovery processes, and therefore, it is an area that needs further focused research to address various contradictory hypotheses and to describe the flow in the reservoir more reliably.
  • 2.9K
  • 14 Jul 2020
Topic Review
Probabilistic Optimization Techniques in Smart Power System
Stochastic programming is used to solve optimization problems in which the majority of the parameters are probabilistic. Probabilistic optimization can make efficient use of information, both in terms of selecting evaluation points and the message they convey. It can handle many sorts of noise and adapts to various aspects of optimization issues. Unlike deterministic optimization, probabilistic optimization techniques discover the best solution for data with randomness.
  • 2.9K
  • 17 Feb 2022
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