• Energy Research

The integration of numerous intermittent renewable energy sources (IRESs) poses challenges to the power supply-demand balance due to the inherent intermittent and uncertain power outputs of IRESs, which requires higher operational flexibility of the power system. The deployment of flexible ramping products (FRPs) provides a new alternative to accommodate the high penetration of IRESs. Given this background, a bi-level risk-limiting real-time unit commitment/real-time economic dispatch model considering FRPs provided by different flexibility resources is proposed. In the proposed model, the objective is to maximize the social surplus while minimizing the operational risk, quantified using the concept of conditional value-at-risk (CVaR). Energy and ramping capabilities of conventional generating units during the start-up or shut-down processes are considered, while meeting the constraints including unit start-up/shut-down trajectories and ramping up/down rates in consecutive time periods. The Karush–Kuhn–Tucker (KKT) optimality conditions are then used to convert the bi-level programming problem into a single-level one, which can be directly solved after linearization. The modified IEEE 14-bus power system is employed to demonstrate the proposed method, and the role of FRPs in enhancing the system flexibility and improving the accommodation capability for IRESs is illustrated in some operation scenarios of the sample system. The impact of the confidence level in CVaR on the system operational flexibility is also investigated through case studies. Finally, a case study is conducted on a regional power system in Guangdong Province, China to demonstrate the potential of the proposed method for practical applications.

The present study investigated the effect of an additional short-duration HIIT program using boxing-specific techniques on activity during a simulated competition. Additionally, we investigated the impact on physical fitness, specifically aerobic performance and lower-body muscle power. Sixteen boxers were randomized into a control (n = 8) or experimental groups (n = 8). The experimental protocol consisted of 3 blocks of 5 repetitions of 30s all-out effort, with 6s recovery between repetitions and 1 min rest interval between blocks, conducted 3 days per week for 4 weeks. A two-way (group, two levels; moment, two levels) analysis of variance with repeated measurements in the second factor was used. For the experimental group, there was a change in body mass (ES = −0.13 (trivial)), body fat percentage (ES = −0.12 (trivial)), VO2max (ES = +0.42 (small)), CMJ (ES = +0.12 (trivial)), CMJ-left (ES = −0.11 (trivial)), CMJ-right (ES = +0.22 (trivial)), actions (ES = +0.68 (moderate)), time (ES = −0.29 (small)) and punches (ES = +0.56 (moderate)). For the control group, there was a change in body mass (ES = +0.04 (trivial)), body fat percentage (ES = −0.12 (trivial)), VO2max (ES = +0.11 (trivial)), CMJ (ES = −0.27 (small)), CMJ-left (ES = −0.39 (small)), CMJ-right (ES = +0.08 (trivial)), actions (ES = +0.08 (trivial)), time (ES = −0.65 (moderate)) and punches (ES = −0.57 (moderate)). The punches variable was significant concerning group-by-time interaction (F1,14 = 11.630; p = 0.004; n2 = 0.454). The present study indicated that the addition of a boxing-specific HIIT program is effective to increase the number of punches during a simulated match.

Heavy or intermittent rainfall can cause slopes to become unstable and erode, resulting in significant damage, loss of life, and destruction of property. Targeted management solutions are based on an analysis of slopes’ flow generation and sediment production patterns during periods of rainfall. This study used a fully granite backfill slope as its research subject and examined the features of slope erosion during intermittent rainfall. We examined the processes of slope flow generation and soil erosion during intermittent rain through indoor artificially simulated rainfall experiments. Three intermittent rainfall events with a 220 mm/h intensity were designed during the experiment. Each rainfall event lasted for 60 min, with an interval of 60 min between the events. By analyzing multiple rainfall events, this study reveals the patterns of runoff and sediment yield on different slopes in response to variations in rainfall intensity and slope gradient. The runoff volume on other slope surfaces exhibits a similar pattern in reaction to changes in rainfall events. As the frequency of rainfall events increases, the surface runoff tends to be higher. Additionally, with variations in slope steepness, the runoff volume generally follows an increasing trend. Notably, the slope with a 20° incline shows the smallest runoff volume. The sediment yield on different slope surfaces gradually increases as the slope increases. In particular, on a 20° slope, the sediment yield experiences a substantial increase, indicating that the impact of the slope on the sediment yield becomes more pronounced. In different rainfall events, the morphology of the slope changes due to the influence of gravity and hydraulics, resulting in oscillations in both the average runoff rate and sediment yield. Furthermore, as the slope steepens, the amplitude of these oscillations increases. The process of slope erosion involves three stages: raindrop splash erosion, runoff erosion, and collapse damage. The sequence of slope damage locations is as follows: footslope, mid-slope, and hilltop. For the backfilled slope of completely weathered granite, the artificial slope can be controlled to around 20°. Erosion on the slope mainly occurs after the formation of gullies, and slope management should focus on preventing gully formation before it happens.

Under the environmental crisis of global warming, more efforts are put in application of low carbon energy, especially low-carbon electricity. Development of wind generation is one potential solution to provide low-carbon electricity source. This paper researches operation of wind generation in a de-regulated power market. It develops bidding models under two schemes for variable wind generation to analyze the competition among generation companies (GENCOs) considering transmission constraints. The proposed method employs the supply function equilibrium (SFE) for modeling the bidding strategy of GENCOs. The bidding process is solved as a bi-level optimization problem. In the upper level, the profit of an individual GENCO is maximized; while in the lower level, the market clearing process of the independent system operator (ISO) is modeled to minimize the production cost. An intelligent search based on genetic algorithm and Monte Carlo simulation (MCS) is applied to obtain the solution. The PJM five-bus system and the IEEE 118-bus system are used for numerical studies. The results show when wind GENCOs play as strategic bidders to set the price, they can make significant profit uplifts as opposed to playing as a price taker, because the profit gain will outweigh the cost to cover wind uncertainty and reliability issues. However, this may result in an increase in total production cost and the profit of other units, which means consumers need to pay more. Thus, it is necessary to update the existing market architecture and structure considering these pros and cons in order to maintain a healthy competitive market.

Rosmarinus officinalis L. belongs to the Lamiaceae family and is cultivated worldwide due to its diverse uses as an ornamental evergreen shrub in gardening, as well as a food seasoning and a natural medicine. The present research was conducted to study the morphological traits of seven wild-grown rosemary populations in Greece, as well as the propagation of two selected populations with the most desirable ornamental characteristics, by the use of shoot cuttings and in vitro cultures. From the study of the morphological traits of the seven populations, those with interesting features were grown in the areas of Amaliada and Piperia and, thus, were chosen for studying their propagation. Rooting of the shoot cuttings was carried out during the four seasons of the year, using potassium salt Indole-3-butyric acid (K-IBA) at concentrations of 0.5 and 1 g·L−1, in various substrates under the intermittent mist or fog system. It was found that the shoot cuttings rooted easily in all four seasons, but there were better results for the population of ‘Piperia’ in autumn, with 1 g·L−1 K-IBA (80%), and ‘Amaliada’ in spring, with 0.5 g·L−1 K-IBA (82.5%), while higher rooting percentages were achieved in the fog system, on a substrate consisting of perlite and peat, in a ratio of 2:1 (85%). For the in vitro cultures, shoot tips excised from the two selected populations were successfully disinfested by pre-soaking in an antioxidant solution and then, by sterilizing them in 0.6% (w/v) NaOCl, followed by transferring them onto a Murashige and Skoog (MS) nutrient medium. ‘Amaliada’ cultures proved to be the most productive population (2.1 shoots per explant), with the highest shoot formation frequency (91.6%), when cultivated on the MS nutrient medium without plant growth regulators. For ‘Piperia’ cultures, the highest shoot formation frequency (66.6%) was achieved on the MS nutrient medium supplemented with 0.25 or 0.5 mg·L−1 6-Benzyloaminopurine (BAP) and 0.1 mg·L−1 Indole-3-acetic acid (IAA). Spontaneous root formation frequency was noticed on the MS nutrient medium, containing 0.5 mg·L−1 BAP and 0.1 mg·L−1 IAA, for both ‘Amaliada’ and ‘Piperia’ cultures (50% and 41.6%, respectively) in a single stage, with root lengths of 7.1 and 5.3 cm, respectively. Rosemary plantlets, with roots formed in vitro after transplanting them in soilless substrate, were acclimatized adequately in the greenhouse environment (~70%).

The rapid growth of distributed generator (DG) capacities has introduced additional controllable assets to improve the performance of distribution systems in terms of service restoration. Renewable DGs are of particular interest to utility companies, but the stochastic nature of intermittent renewable DGs could have a negative impact on the electric grid if they are not properly handled. In this study, we investigate distribution system service restoration using DGs as the primary power source, and we develop an effective approach to handle the uncertainty of renewable DGs under extreme conditions. The distribution system service restoration problem can be described as a mixed-integer second-order cone programming model by modifying the radial topology constraints and power flow equations. The uncertainty of renewable DGs will be modeled using a chance-constrained approach. Furthermore, the forecast errors and noises in real-time operation are solved using a novel model-free control algorithm that can automatically track the trajectory of real-time DG output. The proposed service restoration strategy and model-free control algorithm are validated using an IEEE 123-bus test system.

A successful deployment of power generation coming from variable renewable sources, such as wind and solar photovoltaic, strongly depends on the economic cost of system integration. This paper, in seeking to look beyond the impact of renewable generation on the evolution of the total economic costs associated with the operation of the electricity system, aims to estimate the sensitivity of balancing market requirements and costs to the variable and non-fully predictable nature of intermittent renewable generation. The estimations reported in this paper for the Spanish electricity system stress the importance of both attributes as well as power system flexibility when accounting for the cost of balancing services.