Hydropower Generation Capacity Research Articles

Hydropower Development and Economic Growth in Nepal: Challenges and Prospects

Nepal is rich in water resources, and hydropower development has been a key issue for the country's socio-economic development. But, it needs to produce huge amounts of electricity to support economic activities and growth, though it faces challenges. The paper attempts to fill this gap by studying hydropower development in support of economic growth and overall development, and further discussing its challenges through a literature review analysis and Key Informant Interviews. Economically, Nepal has more than 42000 MW of hydropower generation capacity, but the present generation capacity is 2945 MW, though only below more than 50 percent of the total generation capacity works out in the dry season due to low water discharge and faces a deficiency of electricity. Nepal also imports electricity from India to fulfill domestic demands in the season. There is a gap in the demand and supply lines. Hydropower has become a de-facto reality in light of economic development and the production of hydropower is crucial as Nepal exported electricity of Rs.15.4 billion worth last year. However, this study shows that the prospect of hydropower development is optimistic, though, there are several challenges in terms of priorities of needy projects, investment, environment-forest-land policies, and governance aspects. If pragmatic policy, effective governance, and leadership interventions are adopted on time, challenges can be overcome.

Greed is good? Of equilibrium impacts in environmental regulation

This paper presents a novel method to quantify the market equilibrium impacts of tighter environmental policies. The approach is taken to evaluate the welfare effects of emerging environmental regulations to protect the biodiversity of river ecosystems that put pressure on reducing hydropower generation capacity. A dataset of 129 million bids in the Nordic electricity market is used to calculate how small reductions in hydropower capacity change market outcomes and surpluses hour-by-hour for the years 2011–2022. Reaching the EU Biodiversity Strategy target of 2030 is estimated to reduce 56 MW of hydropower capacity in Finland. Such a change would lead to quantifiable welfare losses of €62 million over time, not counting environmental benefits. Notably, the producer surplus increases by €318 million over time through electricity market price changes, suggesting that instead of lobbying against biodiversity enhancing regulation, agreeing to an industry-wide implementation could benefit both the environment and the firms. Yet the fact that consumer costs increase more than the mere implementation cost reads as a sign of caution when tighter biodiversity policies are introduced.

System Studies to Assess Preparedness of the Zambian Electrical Grid for the Energy Transition Through Integration of Large-Scale Variable Renewable Energy Sources

Zambia still faces significant challenges in her quest to become a middle-income nation by 2030. Some of these issues include low access to clean energy technologies, low electrification rates and limited infrastructure to transport electricity. Moreover, for a country that is predominantly hydropower dependent with an 85% share, climate change induced droughts contributed to approximately a 30% power deficit in 2020 owing to reduction in the hydropower generation capacity. Two years down the line the situation has not changed much with load management anticipated to commence in the fourth quarter of 2022 with an average outage duration of 6 hours a day countrywide. However, with approximately 3000 sunshine hours per annum and an average solar insolation of 5.5 kWh/m2/day and great wind resource potential (~6 to 11 m/s) for utility scale wind power in some parts of the country at heights between 80 and 200 m above sea level (A.S.L), Zambia has potential to benefit from its immense renewable resources endowment to accelerate electricity access and decarbonization of the power sector. In 2019, RES4Africa alongside Enel Foundation and with technical expertise from CESI conducted an optimal technical-economic penetration of variable renewable energy sources (VRES) in Zambia. This study had limitations as it did not tackle site-specific geospatial mapping of VRES, nor did it delve into technical system studies to include steady state and dynamic stability analyses for the Zambian power grid owing to the large-scale VRES penetration. With this motivation in research gap, a systematic methodology was developed by the author for the potential of conducting renewable energy penetration system studies for the Zambian integrated power system for the year 2025 and 2030. Thereafter, the potential sites were mapped using QGIS before applying the formulated modelling methodology on the Zambian grid to conduct steady state and dynamic stability studies for the various scenarios and study cases (i.e., 2025 base, 2025 peak demand with VRES, 2025 peak solar, 2025 peak VRES). The results obtained using Power factory Dig SILENT modelling, and simulation software are presented as system steady state, short circuit, system inertia estimation and dynamic stability analyses. The results obtained for each scenario were compared to the base case i.e., before connecting the proposed VRES projects. Further, investigation of system adequacy and security were performed through contingency analysis. The 2025 steady state analysis for the peak VRES case revealed that the loading of the transmission lines was below 100%. With the proposed VRES projects contributing to about 68% of the total system generation under this condition, the results showed huge reduction in loadings of the transmission lines from the major power plants i.e., Kariba North and Kafue Gorge Power plants when compared to the base case results. The 2025 system inertia analysis for the peak VRES case showed a reduction in the system inertia by approximately 68.5% compared to the base case. This is because the dispatch to serve the grid load in this scenario prioritized VRES over hydropower. The 2025 short circuit analysis revealed that the largest decrease in the fault level was Kariba North Bank and Kafue gorge power stations under peak VRES condition with a reduction of 6kA owing to all the machines being switched off at Kariba North from the initial 6 while Kafue Gorge upper had 2 running machines from the initial 6 in the base case. On the other hand, an overall increase in short circuit levels was experienced across the network for the Peak demand case with VRES. In the dynamic stability analysis, fault ride through (FRT) studies were conducted to ensure that VRES plants stay connected when the AC grid voltage is temporarily reduced or increased due to a fault or large load change in the grid. Moreover, the study demonstrated that for all 2025 study cases, a general increase in rate of change of frequency (RoCoF) values was observed with increased VRES integration. However, all RoCoF values obtained were well below the 1Hz/s threshold as stipulated in the Zambian transmission grid code with both frequency nadir and zenith values being well within the 50±2.5% limits.Seeing that a large share of grid demand will be met by VRES in 2025, 2030 and beyond, detailed future research must go towards utilization of machine learning and artificial intelligence in nowcasting and day ahead short-term forecasts. This has the potential to optimize both system operations during dispatch and energy market trading both local and regional.

A method of short-term risk and economic dispatch of the hydro-thermal-wind-PV hybrid system considering spinning reserve requirements

The objective of the traditional dispatching model of multi-energy systems is to seek the most economical scheduling mode, while ignoring the operating risk caused by inaccurate predictions of wind and PV power. Given this, this paper proposes a framework for the short-term risk and economic dispatch of the hydro-thermal-wind-PV hybrid system (HTWPS). First, a quantile regression method and multivariate Gaussian distribution are adopted to generate wind-PV scenarios. Then, a short-term risk and economic dispatching model of the HTWPS considering spinning reserve (SR) requirements is established to minimize the operating risk and cost. Finally, a synchronic peak-shaving strategy for hydropower stations is developed to determine reasonable hydropower generation plans in model solving. The proposed framework is applied to China’s Qinghai grid. The results show that: (1) As comprehensive utilization flow rises, the cost and risk drop sharply in the dry season, but almost keep unchanged in the wet season constrained by hydropower SR boundary. (2) The power abandonment risk in the dry season is high due to the low hydropower generation capacity induced by limited runoff. The power abandonment and shortage risk are mainly subject to the hydropower SR boundary in the wet season. (3) Compared with the operating mode with hydropower SR alone, the comprehensive risk decreases by 10.6%, and the comprehensive cost rises by 5.8% under the operating mode with hydro and thermal power SR (HTSR) in the dry season. The comprehensive risk decreases by 51.4%, and the comprehensive cost increases by 172.8% under HTSR in the wet season.

Forecasting China's hydropower generation capacity using a novel grey combination optimization model

Hydropower is the largest renewable energy power generation source with the largest construction scale and power generation capacity. A reasonable prediction of hydropower generation is conducive to achieving the carbon peak and neutrality goals. Hydropower generation is affected by seasons and precipitation, which have significant randomness and uncertainty. To realize a reasonable prediction of hydropower generation in China, this paper constructs a novel grey combination optimization model using different parameter combination optimizations based on the three-parameter discrete grey model TDGM(1,1). Further research shows that a better model performance can not necessarily achieved by a higher number of parameter combination optimizations, mainly due to the different effects and influence of various parameters on the model. Subsequently, the TDGM(1,1,r,ξ,Csz) model is applied to forecast China's hydropower generation. The results show that China's hydropower generation can reach 1687.738 hundred million kWh in 2025, an increase of 24.5% compared with 2020. Finally, the rationality of the prediction results is analyzed, and relevant countermeasures and suggestions are proposed.

Optimal Operation of Nashe Hydropower Reservoir under Land Use Land Cover Change in Blue Nile River Basin

Changes in LULC (land use land cover), which significantly influence the spatial and temporal distribution of hydrological processes and water resources in general, have a substantial impact on hydropower generation. The utilization of an optimization approach in order to analyze the operation of reservoirs is an important concern in the planning and management of water resources. The SWAT (Soil and Water Assessment Tool) and the HEC-ResPRM (Hydrologic Engineering Center reservoir evaluation system Prescriptive Reservoir Model) were combined to model and optimize the Nashe hydropower reservoir operation in the Blue Nile River Basin (BNRB). The stream flow into the reservoir was determined using the SWAT model, considering the current and future impacts of LULC changes. The HEC-ResPRM model has been utilized in order to generate the optimal hydropower reservoir operation by using the results of the SWAT calibrated and validated stream flow as input data. This study proposes a method for integrating the HEC-ResPRM and SWAT models to examine the effects of historical and future land use land cover change on the watershed’s hydrological processes and reservoir operation. Therefore, the study aimed to investigate the current and future optimal reservoir operation scenarios for water resources management concerning hydropower generation under the effect of LULC changes. The results reveal that both the 2035 and 2050 LULC change scenarios show the increased operation of hydropower reservoirs with increasing reservoir inflows, releases, storage, and reservoir elevation in the future. The effects of LULC change on the study area’s hydrological components reveal an increase in surface runoff until 2035, and its decrease from 2035 to 2050. The average annual reservoir storage and elevation in the 2050 LULC scenario increased by 7.25% and 2.27%, respectively, when compared to the current optimized scenario. Therefore, changes in LULC have a significant effect on hydropower development by changing the total annual and monthly reservoir inflow volumes and their seasonal distribution. Reservoir operating rule curves have been commonly implemented in the operation of hydropower reservoirs, since they help operators to make essential, optimal decisions with available stream flow. Moreover, the generated future reservoir rule curves can be utilized as a reference for the long-term prediction of hydropower generation capacity, and assist concerned authorities in the successful operation of the reservoir under the impact of LULC changes.

Optimal hydropower generation of Maithon multi‐purpose reservoir system

AbstractThe present study focuses on optimizing the hydropower generation capacity of a multi‐purpose reservoir system considering various constraints, including reservoir water mass balance, minimization of sediment, maximum and minimum reservoir water storage, maximum and minimum reservoir water releases, reservoir water drawdown levels, reservoir overflows, maximum flood zone space, and maximum and minimum storage constraints under 50%, 70% and 90% dependable inflow conditions The focus is the Maithon multi‐purpose reservoir system located at Maithon, a distance of 40.2 km from Dhanbad, the coal capital of India, in the State of Jharkhand. The study results indicate the derived policy is capable of producing maximum annual hydropower of 146,519.48 MWh/year for a 50% dependable inflow condition, 105,512.02 MWh/year for a 70% dependable inflow condition and 58,924.38 MWh/year for a 90% dependable inflow condition, compared to the existing hydropower generation of 129,428.4 MWh/year (average of last 10 years). A trade‐off between reservoir release water releases, mostly for meeting irrigation water needs and maximizing energy generation, was determined for use by various stakeholders and managers of reservoir operations.

Quantifying the potential impacts of land-use and climate change on hydropower reliability of Muzizi hydropower plant, Uganda

Abstract Ugandan rivers are being tapped as a resource for the generation of hydropower in addition to other uses. Studies on the reliability of these hydropower plants due to climate and land-use/land cover changes on the hydrology of these rivers are scanty. Therefore, this study aimed to model the impact of the changing climate and land-use/cover on hydropower reliability to aid proper planning and management. The hydropower reliability of Muzizi River catchment was determined from its past (1998–2010) and midcentury (2041–2060) discharge at 30 and 95% exceedance probability under Representative Concentration Pathways (RCPs) of 4.5 and 8.5, respectively. The past and projected hydropower were compared to determine how future climate and land-use changes will impact the discharge and hydropower reliability of Muzizi River catchment. Six LULC scenarios (deforestation, 31–20%; grassland, 19–3%; cropland, 50–77%; water bodies, 0.02–0.01%; settlement, 0.23–0.37%, and Barren land 0.055–0.046% between 2014 and 2060) and three downscaled Regional Climate Model (REMO and RCA4 for precipitation and RACMO22T for temperature from a pool of four CORDEX (Coordinated Regional Climate Downscaling Experiment) Africa RCMs) were examined. A calibrated SWAT simulation model was applied for the midcentury (2041–2060) period, and a potential change in hydropower energy in reference to mean daily flow (designflow ≥ 30% exceedance probability), firm flow (flow ≥ 95% exceedance probability), and mean annual flow was evaluated under the condition of altered runoff under RCP4.5 and RCP8.5 climate change scenarios for an average of REMO and RCA4 RCM. The future land use (2060) was projected using the MOLUSCE (Module for Land Use Change Evaluation) plugin in QGIS using CA-ANN. Three scenarios have been described in this study, including LULC change, climate change, and combined (climate and LULC change). The results suggest that there will be a significant increase in annual hydropower generation capacity (from 386.27 and 488.1 GWh to 867.82 and 862.53 GWh under RCP4.5 and RCP8.5, respectively) for the combined future effect of climate and land-use/cover changes. Energy utilities need to put in place mechanisms to effectively manage, operate, and maintain the hydropower plant amidst climate and land-use change impacts, to ensure reliability at all times.

Valuation of operational flexibility: A case study of Bonneville power administration

Real options theory is applied to quantify the value of operational flexibility intrinsic to the hydropower generation capacity from the perspective of US federal power marketing administrations. The option value in this model arises from the tension between the increase in current sales revenue and the increase in the exposure of future power shortages. Using Bonneville Power Administration as an example, we apply the proposed valuation framework, analyze the optimal management policy for Bonneville Power Administration and investigate the potential impacts of Wind Vision 2050.

Renewable energy systems based on micro-hydro and solar photovoltaic for rural areas: A case study in Yogyakarta, Indonesia

This paper presents renewable energy systems based on micro-hydro and solar photovoltaic for rural areas, with a case study in Yogyakarta, Indonesia. The Special Region of Yogyakarta, located on the island of Java, Indonesia, has a high potential for the development of renewable energy resources, especially hydropower and solar power. Many rural areas in Yogyakarta lack a supply of electricity. In this study, data on the potential for hydropower and solar power in rural regions of Yogyakarta are processed to determine the best capacity of hydroelectric and solar power plants. The extended particle swarm optimization (PSO) technique has been used to ensure optimal capacity optimization of this hybrid systems. The final result of this study is the most optimal of hydropower and solar power generation capacity based on the calculation of cost of capital, grid sales, cost of energy, and net present value.

Moving from Fossil Fuels to Electric Cooking: An Option for Clean Cooking Access in Nepal

Nepal has abundant hydropower potential and generation capacity under construction that should be able to meet the growing energy need of the country. Although access to electricity in the country is increasing, adoption and access to clean cooking facilities remains insignificant, as about 85% of the population still rely on solid fuels to meet their daily cooking needs. In this regard, energy generated from hydropower can play the dual role of providing access to modern energy as well as providing a clean cooking alternative that is clean and sustainable. Having realized this, the Ministry of Energy, Water Resources and Irrigation has issued a white paper (point 73) for the ‘Electric Stove in Every House’ Programme, which is expected to encourage the use of electric cooking. This gives an opportunity not only to make use of Nepal’s hydropower resources but also to reduce its dependence on imported fossil fuel. Our paper discusses the challenges and opportunities for introducing electricity in the cooking fuel mix in Nepal from the policy perspective. We draw upon the review of lessons learned from other countries including Ecuador, Bhutan and South Africa, to illustrate the potential pathways for the transition of fossil fuel-based products to electricity in Nepal. These countries have used a combination of approaches in including electricity in their cooking fuel mix, such as favourable electricity pricing, import tariff reductions in cooking appliances, and developing national policy and programmes to facilitate the integration of electricity in cooking fuel. These lessons from these countries are used to recommend pathways for moving from fossil fuel-based products to electricity in Nepal’s context.

The Effect of Precipitation on Hydropower Generation Capacity: A Perspective of Climate Change

Hydropower, which is the most extensively used renewable energy, is sensitive to the change of streamflow under the great impact of precipitation. According to the relationship between the hydropower station generation and local precipitation, the impact of precipitation on hydropower can be analyzed. In this paper, the GCM and RCM simulations in precipitation are compared firstly, and the high-resolution precipitation data are then calculated by stepwise clustering analysis (SCA) statistical downscaling method. Secondly, based on the hydropower potential (HP), the hydropower response model driven by precipitation (HRMDP) is established. Finally, the simulated generation of a hydropower station in Dadu River basin is used as a case to validate this proposed model. The results show that precipitation will increase by around 42% from May to August in study region, while it will decrease by 40 % in other months in RCP4.5. For different periods of reservoir scheduling, the precipitation will increase by about 40% in the Neutral I and Wet period, while it will decrease by around 30% in other periods, which will lead to the shortening of the peak period of hydropower generation and the peak value will be decreased. Correspondingly, the results show power generation will decrease by around 12% from June to December and increase by around 4% in the rest months. On the other hand, owing to the changes in precipitation, the future power generation will increase by 25% in Neutral I and decrease by 13.5% in other periods, but the total hydropower generation will remain.

Balancing fish-energy-cost tradeoffs through strategic basin-wide dam management

Dam management often involves tradeoffs among hydropower generation capacity, environmental impacts, and project costs. However, our understandings of such tradeoffs under a full range of dam management options remain limited, which hinders our ability to make sound and scientifically defensible dam management decisions. In order to assess the scope for theoretical tradeoffs, a dynamic model of hydropower production, important fish populations, and project costs was developed using the system dynamics modeling technique. Three dam management options investigated the likely outcomes from: dam removal, fishway installation (e.g., pool-and-weir, Denil, and fish lift), and no action. The model was applied to the Penobscot River located in Maine, United States as a proof of concept, where recent actions (i.e., dam removal and fishway construction) have been undertaken. We modeled theoretical influence of these actions on four significant sea-run fish (alewife Alosa pseudoharengus, American shad Alosa sapidissima, Atlantic salmon Salmo salar, and sea lamprey Petromyzon marinus) by developing an index of spawner population potential based on population models for each species. Optimal dam management solutions may maximize spawner population potential and energy production to 60-62% of maximum achievable values while limiting the project cost to US$17 million (44% of the maximum value). Our results demonstrate that basin-scale management strategies may increase the migratory fish restoration while preserving hydropower generation capacity. Diversification of management options (e.g., combination of fishway installations, dam removals, and generation capacity) may increase the efficacy of strategic fish-energy-cost tradeoffs.

Future hydropower generation prediction of large-scale reservoirs in the upper Yangtze River basin under climate change

Climate change, which impacts the spatial and temporal distribution of water resources, has a significant influence on the future hydropower generation. Studying the future evolution pattern of hydropower generation under climate change is of great significance for the medium- and long-term hydropower prediction. The objective of this paper is to predict the future hydropower generation of large-scale reservoir groups under climate change. The innovation of this paper is that the macro-scale distributed hydrological model combined with the optimal operation model of large-scale reservoirs was proposed for hydropower generation prediction. The established model considers the specific operation processes of large-scale reservoir groups, including 62 reservoirs in the case study. First, the Statistical Downscaling Model (SDSM) was built, and the evolution trend of future rainfall and temperature was predicted. Second, the macro-scale distributed Variable Infiltration Capacity (VIC) model was built to predict the future runoff. Finally, the optimal operation generation model of large-scale reservoir groups was established to predict the trends of hydropower generation under climate change. Results demonstrate that under RCP2.6 scenario, there is no significant increase or decrease trend of hydropower generation in the future. But under RCP4.5 and RCP8.5 scenarios, the hydropower generation shows a growing trend, and the increase trend under RCP8.5 scenario is more obvious than that under RCP4.5 scenario. Thus, the development of hydropower generation is sensitive to climate change. This study can provide a reference for the long-term prediction of hydropower generation capacity in the upper Yangtze River Basin.

Could future electric vehicle energy storage be used for hydropeaking mitigation? An eight-country viability analysis

Hydropower short-term response capability and operating flexibility are critical in some electricity systems, especially during peak demand periods. However, operational variability at hydro plants may originate relevant water flow fluctuations (i.e., hydropeaking) that cause severe alterations in stream ecosystem functionality. Such harmful consequences could be reduced if other energy storage were available.The increasing use of electric vehicles (EVs) has presented the application of their batteries for energy grid scale accumulation purposes. EV interaction with the grid and other renewable energy (RE) sources (primarily wind and solar) has been broadly studied. It seems, however, that EV energy storage allocation to mitigate hydropeaking impacts at regional or national scale remains unexplored. This article evaluates the possibility of using EV batteries to provide the system with additional storage capacity to support a more balanced hydropower operation.The analysis is performed for eight countries with diverse socioeconomic and technological environments. Initially, the coherency in the orders of magnitude between hydropower generation and energy storage capacity is evaluated by calculating the accumulation potential of the current passenger car parc in a hypothetical scenario in which the complete fleet is electrified and suited for vehicle-to-grid (V2G) interaction. After validating the feasibility of the proposal, a long-term analysis is performed using diverse energy, EV rates, and battery capacity forecasts gathered from reliable sources. The results indicate that a 50% PEV fleet using 300 Wh/kg batteries may provide stable storage capacity for average daily hydropower 2050 projections in China, Germany, Japan, Spain and the United States.

Managing dams for energy and fish tradeoffs: What does a win-win solution take?

Management activities to restore endangered fish species, such as dam removals, fishway installations, and periodic turbine shutdowns, usually decrease hydropower generation capacities at dams. Quantitative analysis of the tradeoffs between energy production and fish population recovery related to dam decision-making is still lacking. In this study, an integrated hydropower generation and age-structured fish population model was developed using a system dynamics modeling method to assess basin-scale energy-fish tradeoffs under eight dam management scenarios. This model ran across 150 years on a daily time step, applied to five hydroelectric dams located in the main stem of the Penobscot River, Maine. We used alewife (Alosa pseudoharengus) to be representative of the local diadromous fish populations to link projected hydropower production with theoretical influences on migratory fish populations on the model river system. Our results show that while the five dams can produce around 427 GWh/year of energy, without fishway installations they would contribute to a 90% reduction in the alewife spawner abundance. The effectiveness of fishway installations is largely influenced by the size of reopened habitat areas and the actual passage rate of the fishways. Homing to natal habitat has an insignificant effect on the growth of the simulated spawner abundance. Operating turbine shutdowns during alewives' peak downstream migration periods, in addition to other dam management strategies, can effectively increase the spawner abundance by 480–550% while also preserving 65% of the hydropower generation capacity. These data demonstrate that in a river system where active hydropower dams operate, a combination of dam management strategies at the basin scale can best balance the tradeoff between energy production and the potential for migratory fish population recovery.

Estimation of Sediment Deposition at Nausehri Reservoir by Using Multiple Linear Regression and Assessment of its Effect on Hydropower Generation Capacity

This article presents investigation of the inflow of sediments depending upon the stream flow, density and kinematic viscosity of water. The process involves Multiple Linear Regression (MLR) technique for estimation of sediment load and volume, by using UNISTAT software (Version 5.6). A general equation is developed for a specific flow rate while considering density and kinematic viscosity of water as other parameters. The developed equation can be applied in future for determining the sediment concentration when the flow rate is known. The daily stream flow and suspended sediment data belonging to the station Nausehri operated by the Water and Power Development Authority, Pakistan is used as case study. The results indicate that the dam site experiences a mean annual sediment load of 3.74mst. With this much incoming sediment load the reservoir life comes out to be 45 years when no flushing is done. The impact of this sediment deposition on hydro-electric energy generation is also determined, which shows a decrease of 113MW (12%) in the production capacity of the power plant over the life of the reservoir.

Eco-compensation standards for sustaining high flow events below hydropower plants

Abstract High flow events (including both the high flow pulses and floods) exert many critical ecological functions in riverine ecosystems and their elimination will lead to severe ecological degradation. However, common hydropower operations are only required to legally maintain the minimum environmental flows (e-flows). The extra release of high flow events will result in revenue loss of hydropower producers. In this research, we propose an approach to assessing the eco-compensation standard which is necessary to compensate the loss of hydropower producers and promote the release of high flows to downstream rivers. The scenario tree approach is adopted for the generation of possible scenarios of flows and electricity prices to deal with the uncertainties of the two factors in deregulated electricity markets. A stochastic linear programming method is proposed to determine the maximum mean annual revenues under two e-flow provision scenarios, i.e., only sustaining the minimum e-flows (scenario 1) and sustaining both the minimum e-flows and a specified number of high flow events (scenario 2). The revenue difference under the two e-flow scenarios is set as the eco-compensation standard. A case study in the Wangkuai reservoir, China, demonstrates that the eco-compensation standard is obviously influenced by the installed hydropower generation capacity (IHGC) and the number of high flow events planned to be released. Moreover, the greatest standards may be not corresponding to a very large IHGC.

A Review of Hydropower Projects in Nepal

Abstract Power generation using hydro resources offers sustainable, zero energy input cost, zero greenhouse gas emission, low operating and maintenance cost alternative to fossil fuel based power generation. Currently, nearly 17% of the world's total power generation is based on hydro resources and its share to renewable power generation is 70%. Although hydropower is produced in 150 countries, Nepal's economically feasible hydropower generation capacity is one of the highest. However, this huge hydropower potential is still untapped. By harnessing the hydro resources Nepal can meet its domestic demand, create a surplus for export and generate employment for its citizens. This paper reviews Nepal's current hydropower resources, projects, future plan and their impact on the economy.

The benefits of flexibility: The value of wind energy with hydropower

Several studies have shown that the revenue of wind power generators on spot markets (“market value”) diminishes with increasing deployment. This “value drop” is mostly observed in power markets that are dominated by thermal power plants, such as in Germany. This paper assesses the wind market value in power systems where hydroelectric stations with large reservoirs prevail, such as in Sweden. Due to their dispatch flexibility, such hydropower compensates for wind power output variability and thereby mitigates the wind power value drop. The market value of electricity from wind declines with penetration in both types of power systems, but it tends to decline at a slower rate if hydropower is present. This paper presents empirical evidence on the relevance of this effect derived from market data and numerical model results. Our results indicate that when moving from 0% to 30% wind penetration, hydropower mitigates the value drop by a third. As a result, 1 MWh of wind energy is worth 18% more in Sweden than in Germany. Sensitivity analyses indicate high robustness despite large parameter uncertainty: in 80% of all sensitivities, wind energy is valuable 12–29% more in Sweden than in Germany. The benefits of hydropower seem to level off at around 20% wind penetration. This suggests that the hydro flexibility is “exhausted” at this level. Low wind speed wind turbines, carbon pricing, and upgrades of hydropower generation capacity can lever the added value of hydro flexibility further. Not only is wind energy more valuable in the presence of hydropower, hydroelectricity also becomes more valuable if paired with wind power.