Showing papers on "Electricity generation published in 2021"

Hydrogen energy systems: A critical review of technologies, applications, trends and challenges

Abstract: The global energy transition towards a carbon neutral society requires a profound transformation of electricity generation and consumption, as well as of electric power systems. Hydrogen has an important potential to accelerate the process of scaling up clean and renewable energy, however its integration in power systems remains little studied. This paper reviews the current progress and outlook of hydrogen technologies and their application in power systems for hydrogen production, re-electrification and storage. The characteristics of electrolysers and fuel cells are demonstrated with experimental data and the deployments of hydrogen for energy storage, power-to-gas, co- and tri-generation and transportation are investigated using examples from worldwide projects. The current techno-economic status of these technologies and applications is presented, in which cost, efficiency and durability are identified as the main critical aspects. This is also confirmed by the results of a statistical analysis of the literature. Finally, conclusions show that continuous efforts on performance improvements, scale ramp-up, technical prospects and political support are required to enable a cost-competitive hydrogen economy.

Organic solar cells—the path to commercial success

Abstract: Organic solar cells have the potential to become the cheapest form of electricity, beating even silicon photovoltaics. This article summarizes the state of the art in the field, highlighting research challenges, mainly the need for an efficiency increase as well as an improvement in long‐term stability. It discusses possible current and future applications, such as building integrated photovoltaics or portable electronics. Finally, the environmental footprint of this renewable energy technology is evaluated, highlighting the potential to be the energy generation technology with the lowest carbon footprint of all.

Power generation and thermoelectric cooling enabled by momentum and energy multiband alignments.

Abstract: Thermoelectric materials transfer heat and electrical energy, being useful for power generation or cooling applications. Many of these materials have narrow bandgaps, especially for cooling applications where this property has been seen as particularly important for enhancing the thermoelectric properties. We developed SnSe crystals with a wide bandgap Eg ~ 33 kBT with attractive thermoelectric properties through Pb alloying. The momentum and energy multiband alignment promoted by Pb alloying resulted in an ultra-high power factor ~75 μWcm–1K–2 at 300 K, and a ZTave ~ 1.90. We show that a 31-pair thermoelectric device can produce a power generation efficiency ~4.4% and a cooling ΔTmax ~ 45.7 K. These results demonstrate that wide bandgap compounds can be used for thermoelectric cooling applications.

A survey on deep learning methods for power load and renewable energy forecasting in smart microgrids

Abstract: Microgrids have recently emerged as a building block for smart grids combining distributed renewable energy sources (RESs), energy storage devices, and load management methodologies. The intermittent nature of RESs brings several challenges to the smart microgrids, such as reliability, power quality, and balance between supply and demand. Thus, forecasting power generation from RESs, such as wind turbines and solar panels, is becoming essential for the efficient and perpetual operations of the power grid and it also helps in attaining optimal utilization of RESs. Energy demand forecasting is also an integral part of smart microgrids that helps in planning the power generation and energy trading with commercial grid. Machine learning (ML) and deep learning (DL) based models are promising solutions for predicting consumers’ demands and energy generations from RESs. In this context, this manuscript provides a comprehensive survey of the existing DL-based approaches, which are developed for power forecasting of wind turbines and solar panels as well as electric power load forecasting. It also discusses the datasets used to train and test the different DL-based prediction models, enabling future researchers to identify appropriate datasets to use in their work. Even though there are a few related surveys regarding energy management in smart grid applications, they are focused on a specific production application such as either solar or wind. Moreover, none of the surveys review the forecasting schemes for production and load side simultaneously. Finally, previous surveys do not consider the datasets used for forecasting despite their significance in DL-based forecasting approaches. Hence, our survey work is intrinsically different due to its data-centered view, along with presenting DL-based applications for load and energy generation forecasting in both residential and commercial sectors. The comparison of different DL approaches discussed in this manuscript reveals that the efficiency of such forecasting methods is highly dependent on the amount of the historical data and thus a large number of data storage devices and high processing power devices are required to deal with big data. Finally, this study raises several open research problems and opportunities in the area of renewable energy forecasting for smart microgrids.

Comprehensive assessment and multi-objective optimization of a green concept based on a combination of hydrogen and compressed air energy storage (CAES) systems

Abstract: In this paper, a novel efficient and environmentally-friendly hybrid energy production/storage system comprising a compressed air energy storage, a heliostat-driven Brayton cycle, and a hydrogen production unit is proposed and thoroughly investigated. The aim is to minimize the pollutant emission of compressed air energy storage technology while adequately addressing intermittency and electricity curtailment of power grids with high penetration of renewable sources. The proposed system uses the surplus power and wasted heat of the solar-powered Brayton cycle to store pressurized air and hydrogen during off-peak periods, and releases them for extra power generation during peak demand periods. For the performance analysis of this hybrid solution, the reference system is precisely analyzed from thermodynamic and economic points of view. Then, training the results of the developed model employing an artificial neural network, four multi-objective optimization programs based on MOPSO, NSGA-II, PESA-II, and SPEA2 algorithms are performed to find an optimal trade-off between thermodynamic performance and economic attractiveness of the system. It is concluded that the system has an exergy round trip efficiency of 60.4% and a total cost rate of 117.5 $/GJ at the optimum solution. Applying the proposed method for the case study of Los Angeles with real historical data, 3313 ton/year Carbone-Dioxide emission is prevented, resulting in around 80,000 $/year environmental cost reduction. Also, the economic analysis indicates a payback period of shorter than 4.6 years for the system.

Thermoelectric generator (TEG) technologies and applications

Abstract: Nowadays humans are facing difficult issues, such as increasing power costs, environmental pollution and global warming. In order to reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their capacity to transform thermal energy directly into electric power through the Seebeck effect. Due to the unique advantages they present, thermoelectric systems have emerged during the last decade as a promising alternative among other technologies for green power production. In this regard, thermoelectric device output prediction is important both for determining the future use of this new technology and for specifying the key design parameters of thermoelectric generators and systems. Moreover, TEGs are environmentally safe, work quietly as they do not include mechanical mechanisms or rotating elements and can be manufactured on a broad variety of substrates such as silicon, polymers and ceramics. In addition, TEGs are position-independent, have a long working life and are ideal for bulk and compact applications. Furthermore, Thermoelectric generators have been found as a viable solution for direct generation of electricity from waste heat in industrial processes. This paper presents in-depth analysis of TEGs, beginning with a comprehensive overview of their working principles such as the Seebeck effect, the Peltier effect, the Thomson effect and Joule heating with their applications, materials used, Figure of Merit, improvement techniques including different thermoelectric material arrangements and technologies used and substrate types. Moreover, performance simulation examples such as COMSOL Multiphysics and ANSYS-Computational Fluid Dynamics are investigated.

Phase change material-integrated latent heat storage systems for sustainable energy solutions

Abstract: Thermal energy plays an indispensable role in the sustainable development of modern societies. Being a key component in various domestic and industrial processes as well as in power generation systems, the storage of thermal energy ensures system reliability, power dispatchability, and economic profitability. Among the numerous methods of thermal energy storage (TES), latent heat TES technology based on phase change materials has gained renewed attention in recent years owing to its high thermal storage capacity, operational simplicity, and transformative industrial potential. Here, we review the broad and critical role of latent heat TES in recent, state-of-the-art sustainable energy developments. The energy storage systems are categorized into the following categories: solar-thermal storage; electro-thermal storage; waste heat storage; and thermal regulation. The fundamental technology underpinning these systems and materials as well as system design towards efficient latent heat utilization are briefly described. Finally, the exciting research opportunities available to further improve the overall energy efficiency of integrated TES systems are discussed.

Comparative assessment of renewable energy-based hydrogen production methods.

Abstract: Hydrogen is acknowledged as a potential fuel as it can be used as an energy carrier, a storage medium, in fuel cells and as a fuel as well and offers carbon-free solutions. This paper investigates three renewable energy based configurations for hydrogen production. The renewable energy sources considered in this study are solar PV, geothermal power generation and biomass gasification. The proposed study also presents a novel configuration of biomass gasification for hydrogen production via multistage water gas shift reactors. The solar PV and geothermal energy based hydrogen production systems are analysed employing the EES software while the hydrogen production system employing biomass gasification is simulated employing Aspen Plus. All three designed configurations are proceeded through numerous parametric analyses to investigate the system behavior and effect on system efficiencies. The hydrogen production using biomass gasification technique provides with the energetic and exergetic efficiencies of 53.6% and 49.8% and the efficiencies for the geothermal power generation based hydrogen production system are found to be 10.4% and 10.2% respectively. The exergetic and energetic efficiencies of hydrogen production system employing solar PV system are found to be 17.45% and 16.95%, respectively and the system is designed to produce 1.13 mol/s of hydrogen. Furthermore, the results of the parametric studies and sensitivity analyses are presented and discussed.

Advancements and prospects of thermal management and waste heat recovery of PEMFC

Abstract: Despite that the Proton Exchange Membrane Fuel Cell (PEMFC) is considered to be an efficient power device; around half of the energy produced from the electrochemical reaction is dissipated as heat due to irreversibility of the cathodic reaction, Ohmic resistance, and mass transport overpotentials. Effective heat removal from the PEMFC, via cooling, is very important to maintain the cell/stack at a uniform operating temperature ensuring the durability of the device as excessive operating temperature may dry out the membrane and reduces the surface area of the catalyst hence lowering the performance of the cell. In addition to cooling, capturing the produced heat and repurposing it using one of the Waste Heat Recovery (WHR) technologies is an effective approach to add a great economic value to the PEMFC power system. Global warming, climate change, and the high cost of energy production are the main drivers to improve the energy efficiency of PEMFC using WHR. This paper presents an overview of the recent progress concerning the cooling strategies and WHR opportunities for PEMFC. The main cooling techniques of PEMFCs are described and evaluated with respect to their advantages and disadvantages. Additionally, the potential pathways for PEMFC-WHR including heating, cooling, and power generation are explored and assessed. Furthermore, the main challenges and the research prospects for the cooling strategies and WHR of PEMFCs are discussed.

Sustainable renewable energy supply networks optimization – The gradual transition to a renewable energy system within the European Union by 2050

Abstract: In order to achieve the goal of a carbon neutral EU by 2050 and meet the climate targets of the Paris Agreement, a sustainable, efficient, competitive and secure energy system needs to be developed. This paper presents the synthesis of sustainable renewable energy supply networks within the EU-27, proposing a stepwise energy transition in the transport and power sectors, achieving a carbon net neutral target by 2050. A multi-period mixed-integer programming model is developed, with the objective of maximizing sustainability net present value, considering different biomass and waste resources for the production of biofuels, renewable electricity, hydrogen, food and bioproducts, employing different types of technologies. The results show that, with further development of existing technologies, the goal of a carbon-neutral EU can be achieved without compromising food production. Wind farms have proven to be the most promising solution at present for the rapid expansion of electricity generation from renewable energy sources, while the importance of solar photovoltaics is increasing over the years, reaching the 43% share of electricity generation from RES in 2050. Moreover, the energy transition within the EU could have a significant positive impact on the economic, environmental and also social aspects of sustainability, with more than 1.5 million new job opportunities created across the EU over the next 30 years.

Can sustainable ammonia synthesis pathways compete with fossil-fuel based Haber–Bosch processes?

Abstract: As renewable electricity prices continue to decline, interest grows in alternative routes for the synthesis of sustainable fuels and chemicals, including ammonia. Considering demand for fertilizers, as well as its future potential as a dispatchable energy vector, sustainable synthesis of ammonia is being explored as an alternative to the capital- and carbon-intensive fossil-fuel-driven Haber–Bosch process. Here we assess stages along a transition to the sustainable synthesis of ammonia, looking at economic feasibility and climate impacts compared to the incumbent Haber–Bosch without and with CO2 capture. This analysis enables us to suggest technological thresholds for sustainable synthesis of ammonia to become economically and environmentally favourable. When driven by renewable energy sources, the water electrolyzer (near $400 per kW) coupled Haber–Bosch process will reach cost parity near 2.5 cents per kWh electricity. In the case of direct electrochemical ammonia synthesis, achieving cost-parity using the same 2.5 cents per kWh electricity will rely on achieving major advances in performance: an electrolysis full-cell energy efficiency exceeding 40% at a current density of 0.5 A cm−2. Once this operating performance is reached, electrically-powered ammonia synthesis will bring climate benefits when coupled with low-carbon electricity (<180 gCO2e per kWh), achievable when over half of today's U.S. electricity generation is supplied by renewable energy sources. We conclude with a forward-looking perspective on the key challenges and opportunities for sustainable ammonia synthesis routes to be competitive with the incumbent Haber–Bosch process in the future.

A review on the development of compressed air energy storage in China: Technical and economic challenges to commercialization

Abstract: To reduce greenhouse gas emissions and the environmental impact of fossil fuels, China has become the world's largest country in electricity production from renewable energy. The intermittent nature of renewable energy poses challenges to the stability of the existing power grid. Compressed Air Energy Storage (CAES) that stores energy in the form of high-pressure air has the potential to deal with the unstable supply of renewable energy at large scale in China. This study provides a detailed overview of the latest CAES development in China, including feasibility analysis, air storage options for CAES plants, and pilot CAES projects. According to China's energy structure, the application of CAES is reviewed from the perspectives of grid regulation, energy generation, and demand side management. A cost-benefit analysis shows that promoting electricity trading market could enable CAES to realize high-level arbitrage in areas with large power consumptions, and the integration of CAES with renewable energy generation in the “Three North” regions of China reveals considerable economic and environmental benefits. The challenges for commercializing CAES in China are also discussed.

Challenges and prospects of renewable hydrogen-based strategies for full decarbonization of stationary power applications

Abstract: The exponentially growing contribution of renewable energy sources in the electricity mix requires large systems for energy storage to tackle resources intermittency. In this context, the technologies for hydrogen production offer a clean and versatile alternative to boost renewables penetration and energy security. Hydrogen production as a strategy for the decarbonization of the energy sources mix has been investigated since the beginning of the 1990s. The stationary sector, i.e. all parts of the economy excluding the transportation sector, accounts for almost three-quarters of greenhouse gases (GHG) emissions (mass of CO2-eq) in the world associated with power generation. While several publications focus on the hybridization of renewables with traditional energy storage systems or in different pathways of hydrogen use (mainly power-to-gas), this study provides an insightful analysis of the state of art and evolution of renewable hydrogen-based systems (RHS) to power the stationary sector. The analysis started with a thorough review of RHS deployments for power-to-power stationary applications, such as in power generation, industry, residence, commercial building, and critical infrastructure. Then, a detailed evaluation of relevant techno-economic parameters such as levelized cost of energy (LCOE), hydrogen roundtrip efficiency (HRE), loss of power supply probability (LPSP), self-sufficiency ratio (SSR), or renewable fraction (fRES) is provided. Subsequently, lab-scale plants and pilot projects together with current market trends and commercial uptake of RHS and fuel cell systems are examined. Finally, the future techno-economic barriers and challenges for short and medium-term deployment of RHS are identified and discussed.

Ocean wave energy converters: Technical principle, device realization, and performance evaluation

Abstract: As a renewable energy with immense development potential, ocean wave energy has abundant storage. The utilizations of wave energy technology to exploit wave energy resources have broad application prospects and an important realistic meaning. The researchers worldwide have designed many wave energy converters (WEC) with varied and structures based on different concepts. In this paper, the principle of wave energy power generation technology is reviewed and analyzed from basic structure and power take-off (PTO). Some typical WEC and multi-degree of freedom WEC (MDWEC) and their realization are introduced. The analytic hierarchy process (AHP) is employed to construct a comprehensive multi-index model and evaluate the present WEC from five perspectives: energy capture, technology cost economic, reliability, environmental friendliness and adaptability. Results show that in the field of wave energy utilization and development, the MDWEC has a good comprehensive performance and a wide application range. Qualitative and quantitative methods are adopted to find the optimal WEC technical scheme based on the review and analysis of technology principles of wave energy power generation and realization of devices, which can be used for the development of WEC.