Wind Speed Difference Research Articles

Pengkondisi Sinyal RTD Presisi pada Terowongan Angin Indonesian Low-Speed Tunnel

The temperature of the Indonesian Low-Speed Tunnel (ILST) wind tunnel test section was measured using a Pt100-type Resistance Temperature Detector (RTD) sensor. With the upgrade of the Indonesian Low-Speed Tunnel - Data Acquisition and Reduction System (ILST-DARS) using Ethernet communication, an integrated RTD linearization circuit was designed with the Conditioning Unit (CU) Mk3 to replace the Newport 267B 16-bit parallel and DAS-Hub as the current RTD interface. In this research, the design of the signal conditioner uses the RTD_Linearization_v7.xls program from Texas Instruments, the LTspice simulator software, and the AMP01E precision instrumentation amplifier. Based on the calibration results in the range of 20 – 50 0C, this signal conditioner has an average deviation value of 0.38 0C (1.31%). In the wind tunnel speed variation testing with a range of 30 – 65 m/s, the RTD signal conditioner had an average deviation of 0.41 K (0.14%). The Repeatability Test procedure was carried out at a wind speed of 65 m/s with an angle of attack for the test model from -90 to 200 and data were collected 10 times at each angle. The average deviation of temperature against variations in the angle of attack of the test model in this procedure is 0.25 K (0.08%) and the average deviation of wind speed against variations in the angle of attack of the test model is 0.03 m/s (0.04%).

CORRELATION OF ATMOSPHERIC LABILITY INDEX TO VERTICAL WIND SHEAR AT I GUSTI NGURAH RAI AIRPORT

Wind shear is a condition that is detrimental to aircraft because it can cause the aircraft to experience lift, especially during take-off or landing, where wind shear can occur due to bad and unstable weather, so research on the correlation of the atmospheric lability index to wind shear is very important to prevent a plane crash. This research aims to determine the magnitude of the correlation of the atmospheric lability index to the vertical wind shear that occurs at I Gusti Ngurah Rai Airport, Bali. In this research, the Wind Profiler Radar (WPR) brand scintec LAP-3000 was used to obtain wind shear data in the form of wind direction and wind speed data then radiosonde to obtain atmospheric lability index data in the form of Lifted Index (LI), Total-Totals Index (TT), K-Index (KI), and Convective Available Potential Energy (CAPE) index values for each month in 2019-2020. Wind shear measurement was carried out at an altitude of 100-3000 m and data were taken on the difference in wind direction ≥ 60o and the difference in wind speed ≥ 10 knots. Meanwhile, measurement of the atmospheric lability index is carried out by a flying air balloon that has been equipped with a transmitter. All LI, TT, KI, and CAPE index value data and the number of wind shear events were analyzed with Pearson Product Moment correlation. The value of the correlation coefficient (r) between the LI, TT, KI, and CAPE indices was obtained for successive wind shear events of -0.786; 0,250; 0.738, and 0.713. These results show that the LI, KI, and CAPE index values can be used as a reference to predict wind shear events because they have a strong correlation, obtaining a correlation value between 0.60 to 0.79 compared to the TT index.

Analytical solution of advection diffusion equation in two dimensions using different shapes of wind speed and eddy diffusivity

The diffusion equation has been derived in two dimensions using two methods: variable separation and substituting. We compared the results from these solutions to the results from the Copenhagen experiment, taking into consideration the differences in wind speed and eddy diffusivity.

SHORT-TERM WIND SPEED FORECASTING USING DEEP VARIATIONAL LSTM

Wind speed and power at wind power stations affect the efficiency of a wind farm, so accurate wind forecasting, a nonlinear signal with high fluctuations, increases security and better efficiency than wind power. We are looking for wind speed for a wind farm in Iran. In this research, a combined neural network created from variational autoencoder (VAE), long-term, short-term memory (LSTM), and multilayer perceptron (MLP) for dimension Reduction and encoding is proposed for predicting short-term wind speeds. The data used in this research is related to the statistics of 10 minutes of wind speed in 10- meter, 30-meter, and 40-meter wind turbines, the standard deviation of wind speed, air temperature, and humidity. To compare the proposed model (V- LSTM-MLP), we implemented three deep neural network models, including Stacked Auto-Encoder (SAE), recurrent neural networks (Regular LSTM), and hybrid model Encoder-Decoder recurrent network (LSTM-Encoder-MLP) presented on this dataset. According to the RMSE statistical index, the proposed model is worth 0.1127 for a short time and performs better than other types on this dataset.

Dynamic soaring as a means to exceed the solar wind speed

A technique by which a spacecraft can interact with flows of ionized gas in space (the solar wind or interstellar medium) in order to be accelerated to velocities greater than the flow velocity is explored. Inspired by the dynamic soaring maneuvers performed by sea birds and gliders in which differences in wind speed are exploited to gain velocity, in the proposed technique a lift-generating spacecraft circles between regions of the heliosphere that have different wind speeds, gaining energy in the process without the use of propellant and only modest onboard power requirements. In the simplest analysis, the spacecraft motion can be modeled as a series of elastic collisions between regions of the medium moving at different speeds. More detailed models of the spacecraft trajectory are developed to predict the potential velocity gains and the maximum velocity that may be achieved in terms of the lift-to-drag ratio of the vehicle. A lift-generating mechanism is proposed in which power is extracted from the flow over the vehicle in the flight direction and then used to accelerate the surrounding medium in the transverse direction, generating lift (i.e., a force perpendicular to the flow). Large values of lift-to-drag ratio are shown to be possible in the case where a small transverse velocity is imparted over a large area of interaction. The requirement for a large interaction area in the extremely low density of the heliosphere precludes the use of a physical wing, but the use of plasma waves generated by a compact, directional antenna to impart momentum on the surrounding medium is feasible, with the excitation of R-waves, X-waves, Alfven waves, and magnetosonic waves appearing as promising candidates. A conceptual mission is defined in which dynamic soaring is performed on the termination shock of the heliosphere, enabling a spacecraft to reach speeds approaching 2% ofcwithin two and a half years of launch without the expenditure of propellant. The technique may comprise the first stage for a multistage mission to achieve true interstellar flight to other solar systems.

Impact of Field-Protective Forest Belts on the Microclimate of Agroforest Landscape in the Zone of Chestnut Soils of the Volgograd Region

Protective afforestation at the regional level is aimed at ensuring optimal agroecological conditions on agricultural land, including the regulation of microclimate on agricultural land. However, the issue of seasonal variability of microclimatic indicators in the zone of the forest shelterbelt and in different soil and climatic conditions is insufficiently studied. The research purpose is to determine the seasonal influence of aerodynamic parameters of the forest belt on the complex of microclimatic factors in the zone of chestnut soils of southern Russia. The research object is represented with agroforest landscapes of the Kachalinskoe experimental farm of the Ilovlinsky district of the Volgograd region. The study area is typical for this region in terms of soil cover and structure of protective forest plantations. The paper presents the results of study of the microclimate in the openwork-structure forest belt of a 30-year old. The ameliorative influence of the forest belt is determined by its height and construction. We have studied the microclimate indicators, such as wind speed, soil temperature and moisture, air temperature and humidity. We have carried out their instrumental measurements in the forest belt and in the adjacent territory at distances of 3H, 5H, 8H, 10H, 15H, 20H, 25H, 30H (H is the height of the stand in the forest belt) from the forest belt. The measurements were made once a season (summer, autumn, winter) in three-time intervals during the day. The research has shown that positive influence of forest belt on soil temperature in spring and autumn periods is traced up to 10–15H, in winter period there is no influence. The most distinct influence was noted in summer observations, so the average difference of temperatures in summer at 15H in the in the forest belt was 28%; in autumn, the same difference was 15%. The positive influence on soil moisture in the autumn period is most clearly traced, so the average difference in soil moisture indicators near the forest belt and agrolandscape is 18% and 2% in the summer period. The average temperature difference near the forest belt and 20H is only 4%, and 1% in the summer period. Effective reduction of wind speed occurs at 25–30H in the summer season, 15H in the autumn, and 15H in the winter periods. The difference in wind speed near the forest belt and average temperature in the agrolandscape is 52% in summer, 40% in fall, and 30% in winter. The results obtained are an attempt to assess the ameliorative impact of the forest belt on microclimatic indicators under conditions of regional climate change, and to make adjustments in the applied agricultural technologies for cultivation of crops in the inter-belt space.

SAR and ASCAT Tropical Cyclone Wind Speed Reconciliation

Wind speed reconciliation across different wind sources is critically needed for extending available satellite wind records in Tropical Cyclones. The deviations between wind references of extremes, such as the moored buoy data and dropsonde wind estimates for guidance on geophysical model function development, are one of the main causes of wind speed differences for wind products, for instance, the overestimation of Synthetic Aperture Radars (SARs) relative to ASCAT winds. The study proposes a new wind speed adjustment to achieve mutual adjustment between ASCAT CMOD7 winds and simultaneous SAR wind speeds. The so-called CMOD7D-v2 adjustment is constructed based on the statistical analysis of SAR and ASCAT Tropical Cyclone acquisitions between 2016 and 2021, showing a satisfactory performance in wind speed reconciliation for winds with speeds higher than 14 m/s. Furthermore, the error characteristics of the CMOD7D-v2 adjustment for Tropical Cyclone winds are analyzed using the Triple Collocation analysis technique. The analysis results show that the proposed wind adjustment can reduce ASCAT wind errors by around 16.0% when adjusting ASCAT winds to SAR wind speeds. In particular, when downscaling SAR winds, the improvement in ASCAT wind errors can be up to 42.3%, effectively alleviating wind speed differences across wind sources. Furthermore, to avoid the impacts of large footprints by ASCAT sensors, wind speeds retrieved from SAR VV signals (acting as a substitute for ASCAT winds) are adjusted accordingly and compared against SAR dual-polarized winds and collocated Stepped Frequency Microwave Radiometer (SFMR) observations. We find that the bias values of adjusted winds are lower than products from other adjustment schemes by around 5 m/s at the most extreme values. These promising results verify the plausibility of the CMOD7D-v2 adjustment, which is conducive to SAR and ASCAT wind speed comparisons and extreme wind analysis in Tropical Cyclone cases.

Comparison of GRUAN data products for Meisei iMS-100 and Vaisala RS92 radiosondes at Tateno, Japan

Abstract. A total of 99 dual soundings with Meisei iMS-100 radiosonde and Vaisala RS92 radiosondes were carried out at the Aerological Observatory of the Japan Meteorological Agency, known as Tateno (36.06∘ N, 140.13∘ E, 25.2 m; the World Meteorological Organization, WMO, station number 47646), from September 2017 to January 2020. Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) data products (GDPs) from both sets of radiosonde data for 59 flights were subsequently created using a documented processing programme along with the provision of optimal estimates for measurement uncertainty. Differences in radiosonde performance were then quantified using these GDPs. For daytime observations, the iMS-100 temperature is around 0.5 K cooler than RS92-GDP in the stratosphere, with significant differences in the upper troposphere and lower stratosphere in consideration of combined uncertainties. For nighttime observations, the difference is around −0.1 K, and data are mostly in agreement. For relative humidity (RH), iMS-100 is around 1 % RH–2 % RH higher in the troposphere and 1 % RH smaller in the stratosphere than RS92, but both GDPs are in agreement for most of the profile. The mean pressure difference is ≤0.1 hPa, the wind speed difference is from −0.04 to +0.14 m s−1, the wind direction difference is ≤6.4∘, and the root mean square vector difference (RMSVD) for wind is ≤1.04 m s−1.

Feasibility analysis using a porous media model to simulate the wind protection effect of windbreak forests

AbstractThe porous media model theory has been applied to the study of soil wind erosion, and the accuracy of simulation test results using the resistance source term instead of the windbreak geometry model has received much attention. A common shrub windbreak was used as the research object, and a porous media model with a similar shape was established to synthetically compare the wind tunnel experimental data with the results of computational fluid dynamics numerical simulations, analyze its feasibility for windbreak research instead of wind tunnel experiments, and try to elaborate the causes of errors arising from numerical simulations. The relative standard deviation of more than 80% of the sampling points in the porous media model and wind tunnel experimental results was less than 5%, and the wind speed difference at the maximum relative standard deviation was only 0.257 m s−1; the difference in wind speed variation was most obvious on the leeward side of the lower part of the vegetation canopy, but this error does not affect the wind speed recovery trend of the Caragana shrub/forest belt array. The combination of numerical simulations and wind tunnel experiments gives a reference for the accuracy of porous media models used to simulate plant wind protection.

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

Although coronal mass ejections (CMEs) resembling flux ropes generally expand self-similarly, deformations along their fronts have been reported in observations and simulations. We present evidence of one CME becoming deformed after a period of self-similar expansion in the corona. The event was observed by multiple white-light imagers on 2021 January 20–22. The change in shape is evident in observations from the heliospheric imagers from the Wide-Field Imager for Solar Probe Plus (WISPR), which observed this CME for ∼44 hr. We reconstruct the CME using forward-fitting models. In the first hours, observations are consistent with a self-similar expansion, but later on the front flattens, forming a dimple. Our interpretation is that the CME becomes deformed at ∼0.1 au owing to differences in the background solar wind speeds. The CME expands more at higher latitudes, where the background solar wind is faster. We consider other possible causes for deformations, such as loss of coherence and slow-mode shocks. The CME deformation seems to cause a time-of-arrival error of 16 hr at ∼0.5 au. The deformation is clear only in the WISPR observations; thus, it would have been missed by 1 au coronagraphs. Such deformations may help explain the time-of-arrival errors in events where only coronagraph observations are available.

Calculation and analysis of ampacity and stress of overhead transmission line

To ensure the safe operation of a transmission line, it is necessary to study the radial temperature rise and the stress and strain distribution of the transmission line under on-load state. A three-dimensional solid finite element model of reinforced aluminum conductor steel was established, and the temperature and stress distribution of the conductor were calculated. The effects of operating tension, wind speed, and radial temperature difference on the temperature and stress distribution were analyzed. The radial temperature difference increases about 1.40–3.16 °C with the rise of the mean temperature of the conductor. When the ambient temperature decreases from 20 to −40 °C, the mean temperature of the conductor decreases from 50.34 to −9.31 °C, and the external layer stress increases from 44.59 to 60.19 MPa. At the same time, the external layer stress of the conductor increases with the increase in wind speed and operating tension. The stress of the outermost aluminum conductor of the conductor under the radial temperature difference load increases with the rise in the temperature difference, and the stress of the inner aluminum conductor and the inner steel core decreases with the rise in the temperature difference.

Interagency discrepancies in tropical cyclone intensity estimates over the western North Pacific in recent years

AbstractThis study investigates interagency discrepancies among best‐track estimates of tropical cyclone (TC) intensity in the western North Pacific, provided by the Joint Typhoon Warning Center (JTWC), the China Meteorological Administration (CMA), and the Regional Specialized Meteorological Center (RSMC) Tokyo during 2013 to 2019. The results reveal evident differences in maximum wind speed (MSW) estimates, where linear systematic differences are significant. However, the Dvorak parameter (CI) numbers derived from the MSWs reported by the three agencies are internally consistent. Further analysis suggests that the remained CI discrepancies are related to differences in the estimation of intensity trends, initial intensities, and TC positions among these datasets. In addition, the CI estimates provided by the JTWC for TCs over the open ocean are generally higher than those reported by the CMA and RSMC. However, the estimates from CMA and RSMC tend to give higher TC intensities for the TCs in the mainland and coastal areas of China and Japan, respectively, than those over the open ocean with the same intensity in JTWC dataset. This pattern potentially reflects the extensive use of surface observations by these two agencies for landfalling and offshore TCs. These results may help the research community to get more accurate details about the TCs in WNP from the best track datasets of different agencies.

Analysis of Optical Turbulence over the South China Sea Using Balloon-Borne Microthermal Data and ERA5 Data

It is very useful for adaptive optics (AO) systems to have appropriate knowledge of optical turbulence. However, due to the limitations of space and time, it is difficult to obtain turbulence parameters, especially in the far sea area. In this paper, the characteristics of optical turbulence over the South China Sea are obtained by analyzing the meteorological data obtained from the field experiment of ocean optical parameters and the fifth set of reanalysis data of the European Centre for Medium-Range Weather Forecasts (ECMWF) for 10 years (2011–2020). Firstly, a new statistical model is proposed based on the measured data and the Hufnagel-Valley 5/7, which can well reconstruct the atmospheric turbulence characteristics of the South China Sea. Secondly, according to the comparison between the temperature and wind speed data in ERA5 data and microthermal measurement, the ERA5 data have good reliability, with the temperature deviation basically less than 1.5 K and the wind speed deviation basically less than 2 m∙s−1. Thirdly, the vertical distributions and seasonal behavior of the turbulence strength at the determined location are analyzed, which shows that the turbulence strength in the upper atmosphere is strongest in summer, followed by autumn and winter, and weakest in spring. Then, the distribution profile of the Richardson number provides us with the relative probability of the existence of optical turbulence. During summer and September, the instability of the atmosphere is significantly larger than other months and the extremely low intensity in April indicates the most stable condition in all months. Finally, the analysis results of turbulence parameter profiles for many years show that there is good consistency between different parameters.

Wind tunnel test and numerical study of a multi-sided wind tower with horizontal heat pipes

Passive ventilation such as wind towers can ventilate spaces by using regional pressure differences and the stack effect. Wind towers are often closed throughout the winter to prevent an increase in heating energy demand. Heat pipes can be installed to transfer heat from the outgoing to the incoming air, however the inclusion of heat recovery can incur a pressure drop that negatively impacts ventilation rates. Here it is shown that with an array of horizontally arranged heat pipes, ventilation rates of 0.1 m3/s are maintained at a 1 m/s inlet velocity. The incoming air temperature was raised by up to 2.8 °C, thereby increasing the operational window of the passive ventilation system. By mounting the heat pipes horizontally through the wind tower, direct heat transfer is facilitated between the inlet and outlet. The results demonstrate how a passive ventilation and heat recovery system is likely to operate in the winter months of a cooler climate according to the wind speed and temperature difference between the fresh and exhaust air. It is intended that this system will be further developed to provide both heating and cooling in the winter and summer respectively by installing a seasonal thermal loop.

Characterizing the spatial variations of wind velocity and turbulence intensity around a single Tamarix tree

Characterizing airflow and turbulence patterns around real vegetation is essential for predicting aeolian erosion. However, few studies have explored the airflow field around live plants. In this field study, airflow field and turbulence patterns were investigated around a single Tamarix tree. Wind speeds were monitored at 34 locations around the tree at the heights of z/h = 0.13 h, 0.5 h, 1.1 h, and 1.8 h (where h is the height of the tree) in a wind speed of 12.5 m s−1. The results showed that a half-ellipse deceleration zone formed downwind and full-ellipse acceleration zones on the sides of the tree. The largest turbulence intensity was observed at lower heights and in the leeside of the tree where wind speed was highest, and the smallest was found on the sides where wind speed accelerated. On the sides of the tree the structure of wind speed and turbulence profiles was similar and no significant differences (P < 0.001) in wind speeds were found between identical locations. The mean wind velocities downwind of the tree at 0.5 h–7 h and DR1-DR4 (at the right side of the tree edge) were significantly different to the approach flow (wind speeds at −7 h) but no statistical differences were observed between wind speeds in other locations and the approach flow. The values of Rc∆x, z (wind velocity reduction coefficient) were higher in the wake of the tree than upwind and on the sides of the tree indicating that the sheltering effect of the tree extended to the distance of seven times the height tree. This study represents an important investigation of the plant effect on airflow and the results can be used to inform Tamarix management and support parameterization of drag partition schemes to improve the accuracy of aeolian transport models in landscapes with Tamarix.

Long-Term Variability of Wind Speed and Direction in the Mediterranean Basin

In this work, the ERA5 reanalysis dataset, with its fine spatial and temporal resolution, is used to study the wind speed and direction characteristics in the Mediterranean basin from 1979 to 2020. Their variability, trend and mean values, as well as their association, are examined in the monthly, annual and interannual/decadal time scales. The long-term variability of the wind direction is assessed using the angular variance, while the mean annual and interannual variability are used for the wind speed. The most characteristic and constant flow systems appear in the Gulf of Lion (Mistral) and the Aegean Sea during the summer (Etesian winds). The mean annual variability maximizes in the northern part of the basin, while the western part appears to have the most variable wind directions, while the fastest increasing wind speeds appear in the southwestern Levantine sub-basin. The long-term linear trend for the mean, the 95th and 99th quantiles of annual wind speed and the number of occurrences of extreme wind events have been also assessed. For particular areas, there is an increasing tendency in both intensity and frequency of occurrence of extreme wind events. Τhe linear-circular correlation coefficient has been implemented in order to quantify the linear association between the wind direction and the wind speed. This parameter demonstrates higher annual values for the Mistral wind in the Gulf of Lion and the Etesian winds in the Aegean Sea during the summer. Finally, the comparison of the results of ERA5 with the results of ERA-Interim highlighted significant differences in the Mediterranean wind speed and direction characteristics.

A COMPARATIVE ASSESSMENT OF MACHINE LEARNING MODELS FOR PREDICTING WIND SPEED

Renewable energy is one of the most critical issues of continuously increasing electricity consumption which is becoming a desirable alternative to traditional methods of electricity generation such as coal or fossil fuels. This study aimed to develop, evaluate, and compare the performance of Linear multiple regression (MLR), support vector regression (SVR), Bagging and random forest (R.F.), and decision tree (CART) models in predicting wind speed in Southeastern Iran. The data used in this research is related to the statistics of 10 minutes of wind speed in 10-meter, 30-meter, and 40-meter wind turbines, the standard deviation of wind speed, air temperature, humidity, and amount of the Sun's radiation. The bagging and random forest model with an RMSE error of 0.0086 perform better than others in this dataset, while the MLR model with an RMSE error of 0.0407 has the worst.

The Impact of High-Resolution SRTM Topography and Corine Land Cover on Lightning Calculations in WRF

The goal of this study is to investigate the impact of high-resolution SRTM and Corine Land Cover on the number of cloud–ground lightning flashes and their spatial distribution simulated by a numerical weather-prediction model. Two lightning episodes were selected: (1) over a non-complex terrain and (2) over a complex terrain, the Alps. Significant discrepancies were found in the geographical distribution of the land-cover classes and also in the topography between Corine Land Cover and 30-arc seconds USGS. In general, the timing and the spatial distribution of Cloud-to-Ground (CG) lightning by the model were well-represented when compared to the observations. In general, more CG flashes were calculated by the simulation with USGS Land Cover and topography than the simulation with Corine Land Cover and SRTM topography. It appears that the differences in sensible and latent heat fluxes between the simulations were caused by the differences in land-cover classes. Moreover, differences in the vertical wind speeds, specific humidity, temperature and the convective available potential energy were found when compared to observations, resulting in the differences in cloud–ground lightning flashes between the simulation with the SRTM topography and Corine Land Cover and the simulation with the USGS Land Cover and topography. Using the high-resolution land cover and topography data may help to reduce uncertainties in CG lightning calculations by the model.

Power Curtailment Analysis of DC Series–Parallel Offshore Wind Farms

This paper analyzes one of the most important power capture challenges of the DC series–parallel collection system, called the power curtailment losses. The wind speed difference between the series-connected turbines causes over- and under-voltage conditions in the output voltage of the MVDC (medium-voltage DC) converters of the wind turbine. The power curtailment losses caused by the upper-voltage tolerance levels of the MVDC converters of the wind turbines are analyzed considering a redundancy-based upper-voltage limiting condition. This analysis emphasizes the importance of choosing suitable voltage tolerance levels for the MVDC converters of wind turbines based on the wind farm configuration. The annual energy curtailment losses are quantified and evaluated by a comparative case study performed on a DC series–parallel-connected wind farm rated at 200 MW with the redundancy-based upper-voltage limiting condition.

Reliability Evaluation of Nondispatchable Energy Sources in Generation Planning: A Wind Electrical System Case Study

Summary. Generation planning is an important aspect of the probabilistic production simulation (PPS) process for power systems. The inclusion of nondispatchable energy sources in the conventional system needs efficient algorithms for reliability evaluation. Moreover, it is crucial to represent the availability of nondispatchable energy sources with a suitable probability distribution function (PDF) that can be easily integrated with the conventional system. The present work extends the generation reliability to include nondispatchable energy sources in the reliability evaluation methodology. The wind electrical system (WS) is represented using a simple wind speed model based on the normal distribution function. The multistate wind speed model based on the mean and standard deviation of wind speed at a particular site is integrated with the conventional system for reliability study. The proposed fast Fourier transform (FFT)-based method eliminates extensive calculations encountered in the conventional approach due to cumbersome time-domain convolution. The efficacy of the methodology is validated with the case studies using the IEEE RTS-wind system with loss of load probability (LOLP) and expected energy not served (EENS) reliability indices.