Power Production Assessment Research Articles

Economic assessment and optimization of low-carbon biomass-based power, methane, and methanol production

Fuel synthesis through CO2 hydrogenation is receiving much attention to decarbonizing the transport sector of future energy systems. In this study, an integrated system is proposed and investigated from a thermo-economic point of view to produce power and synthetic methane and methanol. The proposed system includes an externally fired gas turbine, Rankine cycle, organic Rankine cycle, proton exchange membrane electrolyzer, molten carbonate fuel cell and methane and methanol synthesis units. CO2 hydrogenated under three different scenarios to produce methane-only, methanol-only and dual-production assuming various operating loads of electrolyzer. The influence of the key parameters on the system performance is assessed via response surface method and finally, the system performance is optimized. Under the base conditions, overall exergy efficiency, levelized cost of electricity, methanol and methane is estimated to be 36.8 %, 37.6, 92.8 and 79.4 $/MWh, respectively. Under the optimized conditions for the methane-only scenario, the overall exergy efficiency, levelized cost of electricity and methane is found to be 34.8 %, 36.7 $/MWh and 77.3 $/MWh, respectively.

An adaptive approach-based ensemble for 1 day-ahead production prediction of solar PV systems

The world is becoming more reliant on renewable energy sources to satisfy its growing energy demand. The primary disadvantage of such sources is their significant uncertainty in power production. As appropriate energy production planning and scheduling necessitate a solid and confident assessment of renewable power production, the necessity for developing reliable prediction models grows by the day. This paper proposes an adaptive approach-based ensemble for 1-day ahead production prediction of solar Photovoltaic (PV) systems. Different ensembles of Artificial Neural Networks (ANNs) prediction models are established, whose architectures (number of the ANNs that comprise the ensembles) and configurations (number of hidden nodes required by the ANNs models of the ensembles) change adaptively at each hour h, h∈ [1, 24] of a day, for accommodating the hour seasonality in the solar PV data and, thus, enhancing the 1 day-ahead predictions accuracy. The suggested approach is tested on a 264 kW solar PV system installed at Applied Science Private University, Jordan. Its prediction performance is evaluated, particularly for different weather conditions (seasons) experienced by the concerned PV system, using standard performance metrics. Results show the effectiveness of the suggested approach in predicting solar PV power production and its superiority compared to another prediction approach of the literature that uses single ANNs at each hour h of the day. Specifically, for 1-day ahead prediction, the obtained enhanced accuracy, on average, was around 8%–10% on the test “unseen” datasets.

Power matrix and dynamic response of the hybrid Wavestar-DeepCwind platform under different diameters and regular wave conditions

Power production assessment usually carried out as a power matrix, is essential for the appraisal of wave energy converter (WEC) technologies. This article proposes the hybrid Wavestar-DeepCwind platform, which is composed of Wavestar WEC and a floating wind turbine to evaluate the power matrix under different regular wave conditions and different Wavestar diameters. Firstly, the effects of the Wavestar diameter and power take-off (PTO) damping coefficient on the absorbed power of a single Wavestar placed on the fixed point are investigated using the potential flow-based boundary element method (BEM). Secondly, considering the optimum PTO damping coefficient, the effect of Wavestar diameter on the total absorbed power was found. Finally, numerical simulation is extended for different wave periods and wave heights to estimate the total power matrix and the capture width ratio (CWR) matrix under different diameters. According to the numerical results, it is indicated that the maximum absorbed power and maximum CWR are obtained around the wave periods (T = 5s and T = 6s) for all wave heights (H = 1∼4m) and Wavestar diameters (D = 5–10m). The heave response of the DeepCwind and three Wavestars (WS1 (or WS3) and WS2) in frequency domains are presented and discussed at various conditions.

Wind power production from very large offshore wind farms

<h2>Summary</h2> We provide the first quantitative assessment of power production and wake generation from offshore wind energy lease areas along the U.S. east coast. Deploying 15-MW wind turbines, with spacing equal to the European average, yields electricity production of 116 TWh/year or 3% of current national supply. However, power production is reduced by one-third due to wakes caused by upwind wind turbines and wind farms. Under some flow conditions whole wind-farm wakes can extend up to 90 km downwind of the largest lease areas, and the frequency-weighted average area with a 5% velocity deficit is 2.6 times the footprint of the lease areas. Simulations including maritime corridors demonstrate reduction in the wake effects leading to power-efficiency gains and may offer contingent benefits. First-order scaling rules are developed that describe how "wake shadows" from large offshore wind farms scale with prevailing meteorology and wind turbine installed densities.

Economic and environmental estimated assessment of power production from municipal solid waste using anaerobic digestion and landfill gas technologies

Waste management has always been one of the main challenges of developing countries. So far, several methods have been proposed to manage municipal solid waste (MSW) and reduce its environmental impact. The purpose of this paper is to determine the amount of MSW generated in two different cities in Asia and to investigate the performance of both landfill gas and anaerobic digestion methods for electric power generation. Both Tehran and Beijing have a high rate of daily waste production and can be a good case study to examine the performance of both energy generations technologies from MSW. However, the use of such technologies requires more and more detailed studies in order to encourage private and government sector investors to use them. In addition, the use of alternative energy sources such as electricity from waste is inevitable due to the current problems in the field of energy. The assessment presented in this paper includes the amount of electricity generated in both technologies, economic feasibility based on Levelized Cost of Energy (LCOE) and Payback Time (PBT) calculations approaches, and environmental evaluation according to the global warming potential (GWP) under different three Scenarios. It was found that after a 20-year period, the amount of waste generated in regions of Beijing is 1.96% lower than in Tehran. The total electricity generated by anaerobic digestion technology is 45.2% and 41.9% higher than that of landfill gas project in Tehran and Beijing, respectively. In addition, on the average MSW management under scenarios 2 and 3 in the Tehran and Beijing could reduce GWP by 79.16 and 92.65%, respectively. The average PBT value for a 20-year period in Tehran is 1.1 and 0.67 years higher than in Beijing under landfill gas and anaerobic digestion technologies, respectively.

Finding synergy between renewables and coal: Flexible power and hydrogen production from advanced IGCC plants with integrated CO2 capture

Variable renewable energy (VRE) has seen rapid growth in recent years. However, VRE deployment requires a fleet of dispatchable power plants to supply electricity during periods with limited wind and sunlight. These plants will operate at reduced utilization rates that pose serious economic challenges. To address this challenge, this paper presents the techno-economic assessment of flexible power and hydrogen production from integrated gasification combined cycles (IGCC) employing the gas switching combustion (GSC) technology for CO2 capture and membrane assisted water gas shift (MAWGS) reactors for hydrogen production. Three GSC-MAWGS-IGCC plants are evaluated based on different gasification technologies: Shell, High Temperature Winkler, and GE. These advanced plants are compared to two benchmark IGCC plants, one without and one with CO2 capture. All plants utilize state-of-the-art H-class gas turbines and hot gas clean-up for maximum efficiency. Under baseload operation, the GSC plants returned CO2 avoidance costs in the range of 24.9–36.9 €/ton compared to 44.3 €/ton for the benchmark. However, the major advantage of these plants is evident in the more realistic mid-load scenario. Due to the ability to keep operating and sell hydrogen to the market during times of abundant wind and sun, the best GSC plants offer a 6–11%-point higher annual rate of return than the benchmark plant with CO2 capture. This large economic advantage shows that the flexible GSC plants are a promising option for balancing VRE, provided a market for the generated clean hydrogen exists.

Steam turbine efficiency assessment, first step towards sustainable electricity production

The main objective of actual energy policies around the world is the transition to renewable energy. EIA forecasts nearly 50% increase in world energy usage by 2050, which is hard to achieve using only renewable energy. For year 2019 the electricity production in EU relies mainly on conventional thermal (42.8 %) and nuclear energy sources (26.7%). The accelerated transition to electrical cars puts more pressure on energy producers. As a result, in order to match the ever-growing demand of electrical energy, the conventional thermal energy generation will play a key role, among them coal-based production. In order to meet the environmental goals and for sustainable production of electrical power, energy assessment of power production of coal-based power plants must be performed. The purpose of this paper is to perform an energy assessment of the electrical power production, focusing on a key component of this, the steam turbine. The performance characteristics of the turbine in condensing operation were determined. A proper efficiency of the turbine will have a significant impact on sustainable production of electricity.

Comparative assessment of the annual electricity and water production by concentrating solar power and desalination plants: A case study

The dual production of power and freshwater by the combination of Concentrating Solar Power (CSP) plants and desalination units, technology known as CSP + D, may help to solve the energy and water scarcity problems in arid and semi-arid regions. The lack of accurate annual analyses, crucial for the proper selection of the best CSP + D configuration, hampers the investment in this technology that has not been implemented on an industrial scale so far. This paper presents a simulation tool able to perform an annual assessment of power and freshwater production of CSP + D plants, based on a very accurate solar field model that uses time steps of 10 s. Three CSP + D configurations have been analyzed in two different locations, Abu Dhabi (UAE) and Almería (Spain). Two of the three CSP + D configurations consider the multi-effect distillation (MED) technology for freshwater production, in low-temperature and thermocompression modes. The latter also accounts for the water and electricity demands for the selection of the best coupling arrangement. The annual results of the CSP + MED systems have been finally compared with those obtained from the third configuration, a Reverse Osmosis (RO) unit connected to a CSP plant. Results obtained indicate that, in both locations, the configuration leading to maximum water and electricity productions is CSP + RO (26% more of freshwater in Almería and 10% more in Abu Dhabi). Only if the specific energy consumption of the RO process is above 5.4–5.6 kWh/m3, the most optimum configuration would be CSP + MED at low temperature.

Towards a unified formulation of time and frequency-domain models for point absorbers with single and double-body configuration

Point absorbers represent an attractive choice to harness the wave power potential, even if relevant technology is still in a pre-commercial phase and is not competitive enough, as regards other renewable sources. In this respect, in the last decade research activities focused on the design and optimization of the floating buoy, in order to increase the device efficiency and reduce the power production costs. Based on actual state of art, it is still necessary to develop a unified formulation for the hydrodynamic behaviour of point absorbers with single and double-body configuration. Hence, the first aim of current research is to develop a unified time-domain model for point absorbers with single and double-body configurations, focusing on the assessment of power production and the strength check of the tensioned line, connecting the floating buoy to a permanent magnet linear generator, lying on the seabed. Subsequently, a new formula for power production, based on frequency-domain analysis, is outlined to account for the heave motion restraint, exerted by the Power Take-Off unit, as well as for the partial overlapping between translator and stator. Current analysis is performed for a reference point absorber, deployed in the western Mediterranean Sea.

Validation of a CFD-based numerical wave tank model for the power production assessment of the wavestar ocean wave energy converter

CFD-based numerical wave tank (CNWT) models, are a useful tool for the analysis of wave energy converters (WECs). During the development of a CNWT, model validation is vital, to prove the accuracy of the numerical solution. This paper presents an extensive validation study of a CNWT model for the 1:5 scale Wavestar point-absorber device. The previous studies reported by Ransley et al. [1] and Windt et al. [2] are extended in this paper, by including cases in which the power-take off (PTO) system is included in the model. In this study, the PTO is represented as a linear spring-damper system, providing a good approximation to the full PTO dynamics. The spring stiffness and damping coefficients in the numerical PTO model are determined through a linear least squares fit of the experimental PTO position, velocity and force data. The numerical results for free surface elevation, PTO data (position, velocity, force), generated power and pressure on the WEC hull are shown to compare well with the experimental measurements.

Wind Farm Power Production Assessment: Introduction of a New Actuator Disc Method and Comparison with Existing Models in the Context of a Case Study

The aim of the present study is to perform a comparative analysis of two actuator disc methods (ACD) and two analytical wake models for wind farm power production assessment. To do so, wind turbine power production data from the Lillgrund offshore wind farm in Sweden is used. The measured power production for individual wind turbines is compared with results from simulations, done in the WindSim software, using two ACD methods (ACD (2008) and ACD (2016)) and two analytical wake models widely used within the wind industry (Jensen and Larsen wake models). It was found that the ACD (2016) method and the Larsen model outperform the other method and model in most cases. Furthermore, results from the ACD (2016) method show a clear improvement in the estimated power production in comparison to the ACD (2008) method. The Jensen method seems to overestimate the power deficit for all cases. The ACD (2016) method, despite its simplicity, can capture the power production within the given error margin although it tends to underestimate the power deficit.

A Compact 6-DoF Nonlinear Wave Energy Device Model for Power Assessment and Control Investigations

High accuracy at a low computational time is likely to be a fundamental trait for mathematical models for wave energy converters, in order to be effective tools for reliable motion prediction and power production assessment, device and controller design, and loads estimation. Wave energy converters are particularly prone to exhibit complex and nonlinear behaviors, which are difficult to be modeled efficiently. Highly nonlinear effects, related to nonlinear Froude–Krylov forces, are nonlinear coupling, instability, and parametric resonance, which may damage or improve the power production. It is therefore fundamental to be able to describe such nonlinearities, in order to assess their repercussion on the performance of the device, and eventually design the system in order to exploit them. This paper provides a computationally efficient, compact, and flexible modeling approach for describing nonlinear Froude–Krylov forces for axisymmetric wave energy devices, in 6-DoFs. Unlike other similar models, based on a mesh discretization of the geometry, the analytical formulation of the wetted surface allows the dynamical model to run almost in real time.

Life cycle environmental impact comparison of solid oxide fuel cells fueled by natural gas, hydrogen, ammonia and methanol for combined heat and power generation

This study aims to provide a comprehensive environmental life cycle assessment of heat and power production through solid oxide fuel cells (SOFCs) fueled by various chemical feeds namely; natural gas, hydrogen, ammonia and methanol. The life cycle assessment (LCA) includes the complete phases from raw material extraction or chemical fuel synthesis to consumption in the electrochemical reaction as a cradle-to-grave approach. The LCA study is performed using GaBi software, where the selected impact assessment methodology is ReCiPe 1.08. The selected environmental impact categories are climate change, fossil depletion, human toxicity, water depletion, particulate matter formation, and photochemical oxidant formation. The production pathways of the feed gases are selected based on the mature technologies as well as emerging water electrolysis via wind electricity. Natural gas is extracted from the wells and processed in the processing plant to be fed to SOFC. Hydrogen is generated by steam methane reforming method using the natural gas in the plant. Methanol is also produced by steam methane reforming and methanol synthesis reaction. Ammonia is synthesized using the hydrogen obtained from steam methane reforming and combined with nitrogen from air in a Haber-Bosch plant. Both hydrogen and ammonia are also produced via wind energy-driven decentralized electrolysis in order to emphasize the cleaner fuel production. The results of this study show that feeding SOFC systems with carbon-free fuels eliminates the greenhouse gas emissions during operation, however additional steps required for natural gas to hydrogen, ammonia and methanol conversion, make the complete process more environmentally problematic. However, if hydrogen and ammonia are produced from renewable sources such as wind-based electricity, the environmental impacts reduce significantly, yielding about 0.05 and 0.16 kg CO2 eq., respectively, per kWh electricity generation from SOFC.

A Low-Cost Motion Capture System for Small-Scale Wave Energy Device Tank Testing

The measurement of the motion of a small-scale wave energy device during wave tank tests is important for the evaluation of its response to waves and the assessment of power production. Usually, the motion of a small-scale wave energy converter (WEC) is measured using an optical motion tracking system with high precision and sampling rate. However, the cost for an optical motion tracking system can be considerably high and, therefore, the overall cost for tank testing is increased. This paper proposes a low-cost capture system composed of an inertial measurement unit and ultrasound sensors. The measurements from the ultrasound sensors are combined optimally with the measurements from the inertial measurement unit through an extended Kalman filter (EKF) in order to obtain an accurate estimation of the motion of a WEC.

Articulating parametric resonance for an OWC spar buoy in regular and irregular waves

Wave energy devices are designed, and controlled, to be extremely responsive to incoming wave excitation, hence, maximising power absorption. Due to the consequent large motion excursions, highly nonlinear behaviour is likely to occur, especially in relation to variations in wetted surface. Moreover, nonlinearities may induce parametric instability, or activate internal mechanisms for exchanging energy between different degrees of freedom (DoFs), usually affecting the overall efficiency of the device. Consequently, single-DoF linear models may produce overly optimistic power production predictions, and neglect important dynamics of the system. One highly nonlinear phenomenon, potentially detrimental to power absorption for several wave energy converters, is parametric roll/pitch; due to parametric excitation, part of the energy flow is internally diverted, from the axis where the power take-off is installed, to a secondary axis, generating parasitic motion. This paper proposes a computationally efficient multi-DoF nonlinear model, which can effectively describe nonlinear behaviour, such as parametric pitch and roll, and their impact on motion prediction, power production assessment, and optimal control parameters.

Analytical representation of nonlinear Froude-Krylov forces for 3-DoF point absorbing wave energy devices

Accurate and computationally efficient mathematical models are fundamental for designing, optimizing, and controlling wave energy converters. Many wave energy devices exhibit significant nonlinear behaviour over their full operational envelope, so nonlinear models may become indispensable.Froude-Krylov nonlinearities are of great importance in point absorbers but, in general, their calculation requires an often unacceptable increase in model complexity/computational time. However, for axisymmetric bodies, it is possible to describe the whole geometry analytically, thereby allowing faster calculation of nonlinear Froude-Krylov forces.In this paper, a convenient parametrization of axisymmetric body geometries is proposed, applicable to devices moving in surge, heave, and pitch. While, in general, Froude-Krylov integrals must be solved numerically, by assuming small pitch angles, it is possible to simplify the problem, and achieve a considerably faster algebraic solution. However, both nonlinear models compute in real-time.The framework presented in the paper offers flexibility in terms of computational and fidelity levels, while still representing important nonlinear phenomena such as parametric pitch instability. Models with lower computational requirements may be more suitable for repetitive calculations, such as real-time control, or long-term power production assessment, while higher fidelity models may be more appropriate for maximum load estimation, or short-term power production capability assessment.

Full scale behavior of a small size vertical axis wind turbine

Abstract This paper shows the on-going experimental campaign carried out over a small size vertical axis wind turbine in the facility of the Savona Harbor. Investigations mainly concern two issues: power production assessment and full-scale structural behavior. The first one highlights the importance of a deep knowledge of the local orography and of the wind characteristics (e.g., turbulence intensity); in the absence of reliable wind data it is impossible to properly estimate the performance of the system. The latter allows to identify the possible critical aspects of the structural system (e.g., in terms of resonance conditions) and to investigate the actual dynamic behavior (e.g., in terms of dissipative capacity), necessary for assessing the useful life. The paper points out how these two issues are closely related. Results obtained can provide indications suitable for improving future installations.

Thermodynamic assessment of zero-emission power, hydrogen and methanol production using captured CO2 from S-Graz oxy-fuel cycle and renewable hydrogen

Thermodynamic analysis of a novel combined system, including geothermal driven dual fluid organic Rankine cycle (ORC), S-Graz cycle, proton exchange membrane electrolyzer (PEME) and methanol synthesis unit (MSU) are carried out using energy and exergy principles. The presented system produces zero emission power and hydrogen using oxy-fuel combustion technology and splitting water into hydrogen and oxygen in the PEME, which consumes the dual fluid ORC produced power. Then, methanol production from captured CO2 and produced H2 is suggested to eliminate the captured CO2 from S-Graz cycle. The energy and exergy efficiencies and sustainability index of 14.7%, 42.43% and 1.737 are obtained for the presented cogeneration system, respectively. Also, results associated with the exergy destruction reveal that most of the destroyed exergy in the system is due to the dual fluid ORC in compare with the other units. Furthermore, it is observed that, within the dual fluid ORC, low pressure evaporator (LPE) is responsible for 33% of exergy destruction. Moreover, the results indicate that increasing higher pressure of the dual fluid ORC improves the system energetic and exergetic performance while an increment in geothermal hot water temperature leads to a reduction in system energy and exergy efficiencies.

Power production assessment for wave energy converters: Overcoming the perils of the power matrix

Wave energy converter power production assessment, usually carried out using a power matrix, is essential for the appraisal of new wave energy converter technologies and for the planning of specifi...

A Nonlinear Frequency-Domain Approach for Numerical Simulation of Wave Energy Converters

Nonlinear, analytical wave-energy converter (WEC) models are generally simulated through time-domain (TD) numerical integration. However, the relatively high computational requirements of TD integration are not compatible with applications where a large number of simulations are needed. Spectral domain (SD) linearization has also been proposed to take into account some nonlinear effects, while being much faster than TD integration. However, as explained in this paper, such SD models have limited accuracy, and cannot extend to the static nonlinear forces. In this paper, a nonlinear frequency-domain (NLFD) method is investigated for WEC simulation, using a projection of the dynamical equations onto a basis of trigonometric functions. A comparison with TD integration (second-order Runge$-$Kutta-RK2) and SD methods is provided, through theoretical considerations, and by means of numerical simulations based on two case studies. In the cases considered, the proposed NLFD method allows for significant computational savings compared to RK2 integration, without requiring any approximation for the radiation forces. NLFD thus shows promising potential for applications involving extensive WEC simulation, such as power production assessment, while preserving the WEC model accuracy. Although slower than SD, NLFD has significant benefits in terms of accuracy and range of applicability.