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The existing hydropower plants that were built to serve the base load in the past are now made to run as stand-by units to take up the variation in generation caused due to the increasing solar and wind energy in the grid. This reduces the generation as well as the revenue of these plants and creating a conflict of interest between generating companies and system operators. Thus, arising a need to revise the operating policies of existing hydropower plants, not only for the present capacities of solar and wind but also taking future additions into the account. This problem is taken up in this study on behalf of the state power generating company for their existing hydropower plants. The optimization is carried out using two algorithms, i.e. non-linear optimization and logical optimization. The optimization results provide certain operational observations on many powerhouses, following which the generation could be increased without any additional investment. The algorithms when used for the future additions of solar, wind and thermal, is found to be quite sensitive to the reservoir inflow data. The critical comparison of the used algorithms reveals that rule of thumb can also perform very well when compared with the true optimization. • Existing hydropower plants are facing financial distress due to increasing solar and wind energy in the grid. • The optimization of existing hydropower plants can enhance their generation with changes in existing operating policies. • The rule of thumb used in the operation of hydropower plants can yield results comparable to classical techniques. [ABSTRACT FROM AUTHOR]

Integrating dispatchable hydropower with nondispatchable photovoltaic (PV) power is a promising way to enhance resource use efficiency. However, hybrid generation of these energy sources may exert greater pressure on the integrated water resources management, calling for reservoir reoperation. To address this issue, we propose a procedure to derive adaptive operating rules for a large hydro—PV hybrid power plant consisting of following steps: (1) establish a short-term simulation model to estimate the PV curtailment rate arising from specified long-term hydropower output, in which the relationships are represented as PV energy-loss functions to bridge long- and short-term operations; (2) design six operating rules that incorporate the PV energy-loss functions to simulate the system's long-term operation; and (3) develop a multi-objective optimization model to identify the most effective operating rules. A case study was carried out for China's Longyangxia hydro—PV hybrid power plant. Results showed that, compared with traditional operation, the average annual energy production and power supply reliability of the optimal rule curves increased to 7.3 billion kWh (4.3%) and 90% (47.5%), respectively, while the water shortage index decreased to 114 (6.6%). The derived operating rules could achieve good balance between PV integration and water management. • Short-term operation was considered for long-term reservoir re-operation. • PV energy-loss functions approximately exhibit an S shape. • No conflict between maximizing energy production and power supply reliability. • Coordination between PV integration and water management was achieved. [ABSTRACT FROM AUTHOR]

Abstract This paper performs a multi-model comparison to assess strategies for adaptation to climate change impacts in hydropower generation in Brazil under two Representative Concentration Pathways. The approach used allows for evaluating the interactions between climate change mitigation and adaptation strategies under low and high impact scenarios through 2050. Climate change impact projections of sixteen General Circulation Models indicate that a global high emissions trajectory scenario would likely yield more severe impacts on hydropower generation than a mitigation scenario. Adaptation modeling suggests that climate change impacts can be compensated by a wide range of alternatives, whose optimality will depend on the level of mitigation effort pursued. Our results show that climate change impacts would lead to even higher emissions in the absence of climate change mitigation policies. On the other hand, mitigation strategies to pursue lower emissions are maintained under climate change impacts, meaning that mitigation strategies are robust when faced with adaptation challenges. Mitigation efforts could yield a more diverse and less carbon intensive mix of technological options for adaptation. When analyzing investment costs to adapt to climate change impacts, in some cases mitigation can lead to a lower total investment level. Highlights • Climate change impacts on hydropower are assessed for sixteen models and two scenarios. • Interactions between climate change mitigation and adaptation are analyzed. • Adaptation/mitigation strategies from six different energy models are compared. • Adaptation and mitigation investment costs are assessed and compared. [ABSTRACT FROM AUTHOR]

Abstract This paper formulates an electricity market dominated by price-making hydro-thermal generation. Generation companies optimize their unit commitment, scheduling and bidding decisions simultaneously as a Mixed Integer Programming problem and participate in a market under quantity competition, giving rise to a discontinuous Nash-Cournot game. Both hydropower and thermal units are considered as price-makers. The market equilibrium under uncertainty is computed via time stage decomposition and nesting of a Continuous Nash game into the original Discontinuous Nash game that can be solved via a search algorithm. To highlight applicability of the proposed framework, a case study on the Scandinavian power market is designed and suggests positive welfare effects of large scale storage, whereas the implications on scheduling of conventional units are subsequently discussed. Reformulation allows computationally efficient scaling of the problem and possible extensions to allow large scale applications are discussed. Highlights • A stochastic game model for hydro-thermal power market with price-maker hydropower producers. • A computational method to locate all Nash equilibria for the proposed non-convex game model with integer variables. • A decomposition approach to cope with periodical inflows. [ABSTRACT FROM AUTHOR]

Abstract Recently, Chinese government has determined to guide the energy structure adjustment. The rapid development of hydropower is still important for the low-carbon transition. Therefore, we established a scenario-based system dynamics model considering emission trade scheme (ETS) and government policy. 4 scenarios (No ETS & policy; Only ETS; Only policy; Both ETS & policy) were established to investigate the development path of hydropower in China. In 2030, the installed-capacity of conventional hydropower will reach 364.2, 416.1, 428.7 and 470.5 million kW under four scenarios; and the installed-capacity of pumped-storage power will be 75.8, 85.6, 95.5 and 100.8 million kW under four scenarios. Note that, the development paths of installed-capacity and power generation of pumped-storage power and conventional hydropower are characterized by oblate “S-shaped” curves. By analyzing the differences between scenario 2 (Only ETS) and scenario 3 (Only policy), we can conclude that the effect of policy support on the development of hydropower is larger than the ETS. The conclusions derived from sensitivity analysis show that the changes in policy intensity have greater impact than changes in ETS price. In brief, all the results and discussions can help Chinese government shape a development plan for hydropower generation. Highlights • This paper systematically investigated current situation of hydropower in China and sorted out related policies. • A scenario-based system dynamics model is used to analyze the development path of hydropower under policy incentives. • The development paths of conventional hydropower and pumped-storage power are characterized by oblate shape like “S”. • We carried out a comprehensive scenario analysis to investigate the effects of government support and ETS policies. [ABSTRACT FROM AUTHOR]

In the present study, an optimal renewable energy management strategy (REMS) is proposed as a sustainable policy for non-fossil fuel-based centralistic energy policies. Accordingly, the demand load data and weather big datasets were analyzed using neural networks and analysis of variance, respectively. Biogas generation was modeled using a BSM2 dynamic model, and the available hydropower was evaluated in the form of a techno-economic assessment. A hybrid solar PV/wind turbine/biogas generator/hydroturbine/battery/inverter system was simulated as a gauge unit using the processed data to evaluate the potential of all renewable energies in Iran. The results were used to cluster Iran into various classes based on optimal green energy potential using a K -means algorithm. A factor analysis (FA) was performed using a big matrix consisting of 13 social, economic, environmental, and technical variables in all of Iran's provinces. Factor score coefficients were then employed in a mature multi-criteria decision making analysis technique to determine the order preference for an ideal solution (TOPSIS). These details were used to inform the REMS. The optimal hybrid renewable energy maps were generated and were combined with the FA-TOPSIS results to produce an action plan proposal. The results show that FA can explain 99% of the variance in the big data matrix. Iran can be efficiently clustered into five classes, while a four-stage action plan can assure sustainable development. [ABSTRACT FROM AUTHOR]

The electricity sector in Malaysia is dominated by fossil fuels. This has immensely increased the amount of CO 2 emissions and other pollutants. The objective of this paper is to investigate the potential for inter-fuel substitution between the four major fuels of coal, gas, oil, and hydropower that are currently being used in the generation of electricity in Malaysia. Using a translog production function, the study adopted a ridge regression procedure to estimate the parameters. The results suggest a potential for substitution among the fuels. Hydropower is observed to be a substitute for other fossils fuels which is an indication that the country can gradually move towards adopting a cleaner fuel in the generation of electricity. We also extended the analysis to Thailand and China to show the consistency of the method when applied to different countries. [ABSTRACT FROM AUTHOR]

Hydropower remains, by a wide margin, the largest source of renewable electricity around the world, and hydropower dams supply a greater source of commercial energy than the world's fleet of nuclear power plants. Yet far less attention has been paid to the political, security, and governance elements underlying the continued use and growth of hydropower. Theorists from many disciplines—political geography, security studies, development studies, economics, public policy, and governance—have questioned both the proper role and ostensible benefits from the generation of electricity from large-scale hydroelectric dams, but have tended to approach the problem on a case-by-case basis. In this study, we provide the first systematic, cross-comparative assessment of five hypotheses about global hydropower states, using World Bank data from 1980 to 2010 and a research design which incorporates five reference classes of countries. Based on regression and comparative country analyses, we find tentative statistical evidence that hydropower countries do seem to perform worse on a series of security, economic development, and governance metrics. [ABSTRACT FROM AUTHOR]

The completion of Shuibuya, the last hydropower station to be constructed in the Qingjiang cascade, signifies China's successful development of the world's largest mixed cascade hydropower generation system. Joint operation of such cascaded hydropower stations is considered necessary to improve hydropower output in China. In this study, two modeling methods – routine and optimal operations – were adopted, based on existing rules of reservoir operation, to determine the effects of joint operation. To investigate the realistic and potential effects, the two models were computed using observed runoff data (1951–2009). The potential effects were identified by comparing the total hydropower generation two single cascades and their cogeneration. Under the routine operational mode, the incremental power generation of joint operation would be 5.73 × 10 8 kWh, an increase of 5‰ compared to isolated operation. However, even in isolation, if reservoir operation is optimized through the dynamic programming algorithm, the incremental power generation of the cascade would be 42.24 × 10 8 kWh, which is seven times that of joint operation with routine reservoir operation (5.73 × 10 8 kWh). The results showed that, under current reservoir operating rules, there is little room for improvement in hydropower generation, although joint operation could increase hydropower generation to a certain extent, especially in the reservoirs' refill and release stages. China must amend its existing operational mode for reservoirs to enhance the economic benefits of cascade hydropower stations. Furthermore, to meet increasing demands for both water and energy, carefully considered planning of constructing clusters of these stations is required. [ABSTRACT FROM AUTHOR]

Climate change is projected to increase hydropower generation in some parts of the world and decrease it in others. Here we explore the possible consequences of these impacts for the electricity supply sector at the global scale. Regional hydropower projections are developed by forcing a coupled global hydrological and dam model with downscaled, bias-corrected climate realizations. Consequent impacts on power sector composition and associated emissions and investment costs are explored using the Global Change Assessment Model (GCAM). We find that climate-driven changes in hydropower generation may shift power demands onto and away from carbon intensive technologies. This causes significantly altered power sector CO 2 emissions in several hydro-dependent regions, although the net global impact is modest. For drying regions, we estimate a global, cumulative investment need of approximately one trillion dollars (±$500 billion) this century to make up for deteriorated hydropower generation caused by climate change. Total investments avoided are of a similar magnitude across regions projected to experience increased precipitation. Investment risks and opportunities are concentrated in hydro-dependent countries for which significant climate change is expected. Various countries throughout the Balkans, Latin America and Southern Africa are most vulnerable, whilst Norway, Canada, and Bhutan emerge as clear beneficiaries. [ABSTRACT FROM AUTHOR]

Pumped hydroelectric storage (PHS) is the main utility-scale storage technology. Although PHS systems generally constitute a fraction of generation, they receive increasing attention due to their potential balancing role towards higher penetration of variable renewable energy sources (RES). In the European context it is widely believed that PHS are key elements of the ongoing energy transition. The present analysis examines if this assumption is valid and PHS utilization grows parallel to RES. We collected, harmonised and analysed datasets for 1991–2016 revealing an uneven utilization among European states. While certain countries increased the utilization rates of PHS by a factor of three to four, in several others PHS units are heavily under-utilized. In three extreme cases the utilization rate, compared to the past, is at 10–25% level. We analysed this controversy by identifying tendencies in the electricity markets, ownership and management status in the various countries, as well as competition with other technologies with balancing potential. Finally, we developed a new approach to display PHS tendencies in a compact picture. Building on the growth-share matrix Economics framework, we identified the strategic direction of PHS for each of the analysed countries. [ABSTRACT FROM AUTHOR]

As part of its ambitious long term energy strategy, Switzerland plans to phase out nuclear power production and replace most or all of its significant share of national electricity production (40%) by renewables, in particular by photovoltaics (PV) and wind energy. The existing large fraction of hydropower and significant pumped-storage hydro capacity in the mountainous regions of the country will potentially provide valuable balancing and ancillary services for the management of intermittent production from PV and wind. We present a set of calculations based on data from the current Swiss electricity system, which investigate the effect of different PV-wind mixing ratio scenarios on required import and export from foreign neighbors. It is shown that the current hydropower is a good basis to deal with intermittent energy sources and to keep import rates of electricity at current levels in a fully renewable Switzerland as long as the PV-wind ratio is small. For higher PV-shares, forced export and import will increase but appear acceptable if PV-contribution stays below 0.6. Enlargement of reservoir capacity or oversizing of intermittent renewables can further reduce required import effectively. These findings are quantitatively specific for Switzerland but qualitatively transferable to similar mountainous environments with abundant hydropower resources. [ABSTRACT FROM AUTHOR]

The pump-as-turbine (PAT) technique is limited by its undesirable performance and narrow range of high efficiency due to the mismatch between the conventional backward-curve centrifugal impellers and the turbine running condition. This study aims to significantly improve the performance of PAT by designing a special impeller with forward-curve blades for the turbine working condition, and investigating the method for determining the blade inlet and outlet angles that play important roles in the energy conversion. The performance tests of PATs with the designed special impeller and an original backswept blade impeller were performed. The improved performance after replacing the original impeller with the special impeller was demonstrated by numerically investigating the PATs of specific speed of 18.1 with different impellers by use of a verified computational fluid dynamics technique. The suitability of the proposed methods to other cases was verified by designing and experimenting on two other special impellers used in two other centrifugal pumps as turbines with various specific speeds. Compared with the original backward-curve impellers, the experimental maximum efficiencies of special forward-curve impellers of three various specific speeds are more significantly increased and the flow-efficiency curve is flatter, suggesting the obvious superiority of the forward-curve impeller in PAT. The experimental flow rate of best efficiency point (BEP) is very close to the theoretically designed flow rate, indicating that the theoretical relationship expression between the blade inlet angle and design flow rate provides an effective prediction method of BEPs' flow rate in PAT's turbine operating mode with special impeller. A low-cost and convenient way to significantly improve the efficiency of PAT in turbine mode is provided in this study. [ABSTRACT FROM AUTHOR]

Recently, the spot utilization of surplus pressure in water pipelines to generate and supply energy to intelligent water networks using micro hydropower generation systems has gained significant attention. However, the mechanical seal which is generally adopted in traditional hydropower generators has friction loss and water leakage problems, causing low power generation efficiency and operation stability of generators. In this context, a novel integrated permanent magnet generator (IPMG) which replaces the traditional dynamic mechanical seal with a static seal is proposed. A finite element method based optimization approach is developed to enhance IPMG configurations under multiple design criteria. An IPMG prototype was subsequently manufactured, and its electricity generation performance under different rotation speeds and water velocities was tested. Also, the impacts of different key parameters on the IPMG performance were numerically investigated. The results revealed that the employment of permanent magnet generator helped IPMG to possess superior performance in completely eliminating friction loss and reducing leakage risk. Compared to the traditional generator, the startup water flow velocity of IPMG was effectively reduced so that the total operating hours were significantly extended by 35%. And its annual power generation can be increased by 35.8% for application in urban water supply pipelines. • A novel integrated permanent magnet generator (IPMG) was proposed. • Experimental and numerical investigations were comprehensively carried out. • The average power output of the IPMG is significantly enhanced by 21.8%. • The annual power generation of IPMG can be improved by 35.8%. [ABSTRACT FROM AUTHOR]

Hybrid generation of hydropower and large-scale solar photovoltaic (PV) power has become an effective way to promote the consumption of the PV energy. Although various stochastic optimization (SO) models have been proposed to derive operating rules for a hydro–PV hybrid generation system (HGS), there is a general lack of understanding regarding which kind of SO model could yield potentially better operating rules. To address this issue, we proposed a methodology to evaluate 3 types of representative SO models for deriving operating rules of a grid-connected hydro–PV HGS. First, the SO models were constructed to derive 10 operating rules using historical hydro-meteorological data. Then, a multivariate stochastic simulation approach was proposed to generate the HGS's uncertain inputs synchronously under historical and various hypothetical climatic conditions. Finally, the performance of these operating rules was evaluated in terms of economy, reliability, vulnerability, resilience, and robustness. China's Longyangxia hydro–PV HGS was selected as a case study. It is shown that parameterization-simulation-optimization model has the capability to produce effective operating rules for the hydro–PV HGS that can balance economy, reliability and robustness under various climatic conditions, and is recommended to use in the long-term operation modelling of the hydro-based HGS. [ABSTRACT FROM AUTHOR]

The demand for hydrogen in conventional and unconventional oil refining industries is considerable. Currently, the predominant source of hydrogen is from fossil fuel production pathways, in particular, steam methane reforming (SMR), which incurs a significant greenhouse gas (GHG) emissions footprint. Thus, alternative environmentally benign sources of hydrogen will be needed in oil refinery complexes the world over, if their greenhouse gas (GHG) emissions footprint is to be reduced materially. In this paper, an integrated data-intensive techno-economic model is developed to provide a credible estimate of hydropower-hydrogen production costs in Western Canada. The minimum hydrogen production cost for the hydropower-hydrogen plant amounts to $2.43/kg H 2 – this corresponds to an electrolyser farm with 90 units of a 3496 kW (760 Nm 3 /h) rated electrolyser. This cost is competitive with SMR/SMR coupled with carbon capture and sequestration (CCS) production costs, which vary from $1.87/kg H 2 to $2.60/kg H 2 . This point is buttressed by the fact that if existing hydropower plants are used (hence negating hydropower capital costs), the minimum production cost amounts to $1.18/kg H 2 . Hydrogen from hydro power, under the techno-economic conditions considered here, is competitive compared to SMR. [ABSTRACT FROM AUTHOR]

The structure of the electricity market in Iran is based on a pay-as-bid auction mechanism. In such a market, hydropower generators need to have accurate estimates of energy price in peak hours of the day-ahead market to optimally operate the reservoir and maximize the revenue. This paper aims at providing a robust model with the best predictors for forecasting the maximum daily electricity price (MDEP) in Iran's electricity market. To reach the goal, hourly electricity prices in 2020 and 2021 were used and several artificial intelligence models were employed to predict the MDEP and ADEP (average daily electricity price). A sensitivity analysis of the inputs showed that in most of the models for forecasting the day-ahead MDEP (P t max), the best predictors were P t − 1 max , P t − 7 max , and P t − 30 m a x . Also, the convolutional neural-long short-term memory network (CNN-LSTM) had the best performance for forecasting both MDEP and ADEP in Iran's energy market. Compared to the multivariate linear regression model, the CNN-LSTM dealt well with sinusoidal characteristics and fluctuation of electricity prices. Therefore, it could improve the accuracy and correlation of the MDEP forecasts by 31% and 3.5%, respectively. • The maximum daily electricity price (MDEP) is very important for hydropower plant's operation. • Nonlinearity, instability, and hourly fluctuations of electricity price make it difficult to forecast. • Several artificial intelligent models, SVM, ANN, ANFIS, ANN-GA, and CNN-LSTM, were used for forecasting MDEP. • The best predictors (P t − 1 max , P t − 7 max , and P t − 30 max) were determined in a sensitivity analysis. • The CNN-LSTM model improved the accuracy of forecasts for MDEP by 31% in comparison with the conventional MLR model. [ABSTRACT FROM AUTHOR]

To enhance the security and dispatch ability of a system to supply water and electricity in a cost-effective manner, we propose a model to integrate the operations of a reservoir, hydroelectric power, desalination and wind power. The effect of seasonal energy storage for intermittent wind power is taken into account such that desalination plants can increase power consumption during cold seasons in which wind power is abundant but power demand is small, and can then relieve the burden of water supply from existing reservoirs to enable full operation during peak hours in hot seasons. Our model differs from the combination of an energy-storage system, pumped hydropower, desalination and renewables commonly applied in preceding research. A case study of Taichung city shows that the proposed model can fulfill that water requirement in 2030; the capability of sharing the peak load of existing hydroelectric power units is greatly increased from 398 MW to 1368 MW with an addition of extra 342-MW units, which also eliminate the requirement for 979-MW gas-turbine power fired with natural gas, even though, according to the proposed model, the greater expense from desalination can become compensated by the decreased expense from the power sector. [ABSTRACT FROM AUTHOR]

Here we translate the impacts of climate change on hydropower generation, and discuss implications on greenhouse gas (GHG) emissions and operation in California. We integrate a model of major surface-water reservoirs with an electric grid dispatch model, and perturb it by projected runoff based on representative concentration pathways (RCP4.5 and RCP8.5). Results show that climate change and variability is expected to decrease the average annual hydropower generation by 3.1% under RCP4.5, but have negligible impact under the RCP8.5. Model simulations indicate more inflow, caused by more future extremes, in the future that does not necessarily translate to more energy production because of reservoir spillage of water. While overall volume of future available water for energy production may be similar or higher, the delivery of this volume is expected to be significantly more variable in the future climate than the historical average, which has many implications for hydropower generation. Our results show that the expected changes in future climate leads to increases in grid GHG emissions, load-following capacity, fuel usage, and costs for the RCP4.5 due to generation shortfall, and very slight increases in the same metrics for the RCP8.5 case due to variability causing decreased efficiencies in load-following power plants. [ABSTRACT FROM AUTHOR]

A one-dimensional numerical code estimating the performances of centrifugal PATs (pumps used as turbines) is presented. Firstly, the code calculates the geometrical components of the PAT using information provided in manufacturer catalogues. Then, once these parameters are deduced, it calculates the losses and determines the characteristics curves of the PAT. The method was validated by comparing the theoretical curves with some experimental measurements acquired at the Department of Mechanical, Energy and Management Engineering (DIMEG) of the University of Calabria, at the Mechanical Propulsion National Centre (CNPM) in Milan and at the University of Trento (Italy) on PATs working in a range of specific speed from 9 to 65 rpm m 3/4 s −1/2 . The estimation error was comprised in a range of 5 ÷ 20%, generally acceptable for this kind of application. [ABSTRACT FROM AUTHOR]

Breastshot water wheels were in widespread use in the Nineteenth and Early Twentieth century for the production of energy; although they represent an economic, efficient and sustainable technology, only a small amount of research has been paid to water wheels nowadays, in particular to the breastshot ones. In this work a theoretical approach is adopted to estimate the different kinds of power losses occurring inside a breastshot water wheel, in order to predict its mechanical output power. The theoretical results are then validated with experimental results on a physical steel model. The characteristics experimental curves of the wheel are also illustrated, reporting the wheel efficiency and output power versus the flowrate, stream and wheel velocity. The average estimated error between the experimental and the estimated theoretical output power is 9%, which is much lower than that calculated using some past formulations found in literature. The theoretical results show that the big power losses are the dissipation of the stream kinetic energy against the blades and the hydraulic losses in the headrace, after the passage through the sluice gate; therefore, a better design of the inlet and blades geometry may improve the efficiency of the wheel. [ABSTRACT FROM AUTHOR]

Federal hydropower plants account for approximately half of installed US conventional hydropower capacity, and are an important part of the national renewable energy portfolio. Utilizing the strong linear relationship between the US Geological Survey WaterWatch runoff and annual hydropower generation, a runoff-based assessment approach is introduced in this study to project changes in annual and regional hydropower generation in multiple power marketing areas. Future climate scenarios are developed with a series of global and regional climate models, and the model output is bias-corrected to be consistent with observed data for the recent past. Using this approach, the median change in annual generation at federal projects is projected to be -2 TWh, with an estimated ensemble uncertainty of ±9 TWh. Although these estimates are similar to the recently observed variability in annual hydropower generation, and may therefore appear to be manageable, significantly seasonal runoff changes are projected and it may pose significant challenges in water systems with higher limits on reservoir storage and operational flexibility. Future assessments will be improved by incorporating next-generation climate models, by closer examination of extreme events and longer-term change, and by addressing the interactions among hydropower and other water uses. [ABSTRACT FROM AUTHOR]

The hydropower regulation ability, as an important factor of energy complementarity, can be used to alleviate the fluctuation of wind and photovoltaic power for meeting the load demand, and should not be ignored. To address this issue, the study proposes a hydropower complementarity assessment method for a hybrid energy system considering the load demand variation of the power grid. To begin with, two complementarity assessment indicators, including time and magnitude, are proposed by accounting for the probability that the power output of a hybrid energy system matches the load demand. Then, the complementarity of a hybrid energy system is assessed considering varied installed capacities of wind and photovoltaic plants. The Guandi wind-solar-hydro hybrid power plant on China's Yalong River is selected as a case study. Results from the case study show that: (1) The proposed method is superior to the traditional complementarity assessment methods, such as Pearson correlation coefficient and fluctuation index. (2) The complementarity of the hybrid energy system is underestimated when the hydropower regulation ability is not considered, and the power curtailment rate is overestimated by about 20%. This study provides a new complementarity assessment method for a hybrid renewable energy system. • Complementarity assessment indicators are proposed from time and magnitude. • Hydropower regulation ability and load demand are considered. • The installed proportion of wind and solar plants is analyzed. [ABSTRACT FROM AUTHOR]

The world is undergoing a transition to a more sustainable energy sector dominated by renewable energy sources. This paper proposes an innovative solution that consists of catching water from streams at high altitudes to fill storage containers and transport them down a mountain, converting the potential energy of water into electricity with the regenerative braking systems of electric trucks and storing it in the truck's battery. The energy stored in the electric truck can be sold to the grid or used by the truck to transport other goods. Results show that the levelized cost of the electricity truck hydropower is 30–100 USD/MWh, which is cheap when compared with conventional hydropower 50–200 USD/MWh. The electricity generation world potential for the technology is estimated to be 1.2 PWh per year, which is equivalent to around 4% of the global energy consumption in 2019. Apart from being a low cost and impact electricity generation technology, electric truck hydropower can operate in combination with solar and wind resources and provide energy storage services to the grid. • Innovative hydropower generation alternative. • Levelized cost of the electricity truck hydropower is 30–100 USD/MWh. • The electricity generation world potential for the technology is estimated to be 1.2 PWh per year. • Asia and South America have the highest potential for ETH. [ABSTRACT FROM AUTHOR]

In this work, three different-diameter energy harvesters driven by turbulent air flow and rainwater are designed. Experiments are conducted first on the air-driven harvesters to gain insight on the energy conversion process. Unlike conventional blade-involved systems, the present setup involves using a number of co-rotating compact discs. They are closely spaced and attached to a central shaft, on which a magnet is attached. As the air flow excitations are set to 4 different levels, the harvester performances are measured in both open- and closed-loop electrical circuits. The results show that approximately 0.3 W electricity is produced. Parametric analysis is then conducted to highlight the effect of the system parameters, such as disc diameter, number, exhaust flow rates and inter-disc distance on its performance and to gain insight on its optimum design. Numerical simulations are then conducted to understand the flow physics. Finally, a 40 mm harvester is used to harness energy from rainwater. Compared with the same size air-driven harvester, the rainwater-driven one is working more efficiently in terms of the overall energy conversion efficiency. The maximum electric current is about 4.5 mA. A practical demonstration is then conducted by using the electricity generated to power a red light-emitting diode (LED). [ABSTRACT FROM AUTHOR]

Abstract: The variable electricity output of the RES (renewable energy sources) power plants, such as wind and hydropower, is an important challenge for the electricity system managers. This paper addresses the problem of an electricity system supported mainly on hydro, thermal, and wind power plants. A binary mixed integer non-linear optimization model with hourly time step is described. The model is applied to a system close to the Portuguese electricity case assuming demand forecasts for the year 2020. The main objective of this paper was to analyze the impact that different levels of installed wind power can have in the operation of this electricity system, taking into account the hourly and intra-annual variation of the renewable resources, the demand projections and also the technical restriction of thermal power plants. The results confirmed wind power as strategic technology to reduce both the marginal cost and CO2 emissions. According to the simulations run, wind power will not replace hydropower but a decrease of thermal power production is foreseen as more wind power is added to the system. Large wind power scenarios will particularly affect gas power plants performance, reducing both the load level and the number of operating hours. [Copyright &y& Elsevier]