Continuous Energy Delivery Research Articles

Comprehensive analysis of thermophysical properties of a binary stearyl alcohol and benzamide eutectic phase change material and determination of thermal performance of a solar dryer integrated with phase change material

AbstractA thermal energy storage system must integrate with a solar thermal collector for continuous energy delivery. This article focuses on the identification, preparation, thermo‐physical characteristic studies, and experimental investigation of a novel eutectic hot storage material for solar dryer applications. The identified organic novel eutectic mixture comprises stearyl alcohol and benzamide (SA‐B) with a molar ratio of 70:30. From the differential scanning calorimetry analysis, the melting point and enthalpy of the developed eutectic mixture were found to be 54. 26°C and 157.45 kJ kg−1 respectively. The melting temperature of the eutectic phase‐change material (PCM) fits the drying application. The corrosion analysis test confirms that the prepared eutectic mixture is compact with stainless steel (SS 316) heat exchanger material. Further, the eutectic PCM were characterized using Fourier transform infrared spectroscopy and thermo‐gravimetric analysis, which confirms the material is chemically and thermally stable. The thermal reliability of the eutectic PCM was evaluated through 1000 thermal charge and discharge cycling. In addition, the thermal conductivity of the identified material was found to be 0.18 W m−1 K−1. Thus, the specified material ascertained its suitability for thermal application. Further, 5 kg of eutectic PCM‐filled rectangular heat exchanger was integrated into the solar dryer. The use of eutectic PCM extended the drying time by more than 4 h, which can be helpful to run continuously on intermittent solar days and in the evening after sunset. Hence, the prepared eutectic SA‐B material is irresistible for hot storage dryer application.

Fuzzy Logic Energy Management between Stand-alone PV Systems

Because of its environmental benefits, PV technology is widely used in several applications. It presents an alternative solution for isolated sites that does not dispose a grid connection. However, it has drawbacks, its intermittent character, due to its dependency on meteorological parameters such as the outside temperature and solar irradiation. The produced energy can be more or less than the load requirement. This paper presents an intelligent strategy management between photovoltaic station owners. It can be involved as follow between two customers: the photovoltaic installation production of the first customer is higher than its load requirement; however, the neighboring station has a lack of energy to cover its load. In this case, it brings energy from station 1 to cover the insufficiency and vice versa. The batteries intervene neither, if the required energy cannot be provided by the local and the neighbored stations, nor, to store the excess power. The dual standalone photovoltaic system was created using MATLAB Simulink environment. The proposed management algorithm is based on FLC. The Mamdani is one of the widely known fuzzy inference system. It ensures continuous energy delivery to the load while minimizing wasted power. The outcomes of the simulation demonstrate the previously mentioned controller effectiveness between standalone PV systems.

2050 LCOE (Levelized Cost of Energy) projection for a hybrid PV (photovoltaic)-CSP (concentrated solar power) plant in the Atacama Desert, Chile

This study calculates the LCOE (Levelized Cost of Energy) on the PSDA (Atacama Solar Platform) for a solar–solar energy mix with the objective of evaluate new options for continuous energy delivery. LCOE was calculated for three 50 MW (megawatt) power plants: A PV (photovoltaic), a CSP (concentrated solar power) plant with 15 h TES (thermal energy storage) and a hybrid PV-CSP plant constituted with 20 MWp of PV and 30 MW of CSP with 15 h TES. Calculations present two scenario projections (Blue Map and Roadmap) until 2050 for each type of plant. Due to the huge solar resource available in northern Chile, the PV-CSP hybrid plant results to be a feasible option for electricity generation, as well as being effectively able to meet electricity demand profile of the mining industry present in the area. This type of energy could mitigate long-term energy costs for the heavy mining activity, as well as the country CO2 emissions. Findings point out that PV-CSP plants are a feasible option able to contribute to the continuous delivery of sustainable electricity in northern Chile. Moreover, this option can also contribute towards electricity price stabilization, thus benefiting the mining industry, as well as reducing Chile's carbon footprint.

Microwave ablation energy delivery: influence of power pulsing on ablation results in an ex vivo and in vivo liver model.

The purpose of this study was to compare the impact of continuous and pulsed energy deliveries on microwave ablation growth and shape in unperfused and perfused liver models. A total of 15 kJ at 2.45 GHz was applied to ex vivo bovine liver using one of five delivery methods (n = 50 total, 10 per group): 25 W continuous for 10 min (25 W average), 50 W continuous for 5 min (50 W average), 100 W continuous for 2.5 min (100 W average), 100 W pulsed for 10 min (25 W average), and 100 W pulsed for 5 min (50 W average). A total of 30 kJ was applied to in vivo porcine livers (n = 35, 7 per group) using delivery methods similar to the ex vivo study, but with twice the total ablation time to offset heat loss to blood perfusion. Temperatures were monitored 5-20 mm from the ablation antenna, with values over 60 °C indicating acute cellular necrosis. Comparisons of ablation size and shape were made between experimental groups based on total energy delivery, average power applied, and peak power using ANOVA with post-hoc pairwise tests. No significant differences were noted in ablation sizes or circularities between pulsed and continuous groups in ex vivo tissue. Temperature data demonstrated more rapid heating in pulsed ablations, suggesting that pulsing may overcome blood perfusion and coagulate tissues more rapidly in vivo. Differences in ablation size and shape were noted in vivo despite equivalent energy delivery among all groups. Overall, the largest ablation volume in vivo was produced with 100 W continuous for 5 min (265.7 ± 208.1 cm(3)). At 25 W average, pulsed-power ablation volumes were larger than continuous-power ablations (67.4 ± 34.5 cm(3) versus 23.6 ± 26.5 cm(3), P = 0.43). Similarly, pulsed ablations produced significantly greater length (P ≤ 0.01), with increase in diameter (P = 0.09) and a slight decrease in circularity (P = 0.97). When comparing 50 W average power groups, moderate differences in size were noted (P ≥ 0.06) and pulsed ablations were again slightly more circular. Pulsed energy delivery created larger ablation zones at low average power compared to continuous energy delivery in the presence of blood perfusion. Shorter duty cycles appear to provide greater benefit when pulsing.

Forms of Energy Delivery during Cryo-cooled Radiofrequency Ablation for Optimization of the Ablation Result

Energy transfer from radiofrequency (RF) applicator to tissue is both precondition and limiting factor. The purpose of this ex vivo study was to examine the influence of form of energy delivery on ablation result during RF ablation with cryo-cooled applicators. One hundred eight ablations were performed in ex vivo bovine liver under continuous energy delivery (A), pulsed energy delivery with reduced current during ablation pause (B) and impedance-dependent energy delivery. Maximum ablation time was 20 min. Early termination of ablation in case of loss of conductivity. Optimal ablation parameters were assessed. Short axis diameter of the ablation zone and ablation duration were determined. Ablation results under mode A, B and C were compared with analysis of variance and Tukey-Kramer HSD test. Influence of ablation duration on short axis diameter was evaluated with regression analysis. Significantly largest short axis diameter (51.1 mm ± SD 2.3; p = 0.01) was reached with impedance-dependent energy delivery (pulsed: 46.1 mm ± SD 5.6; continuous: 44.4 mm ± SD 4.1). Significantly longest ablation duration (1061.6 s ± SD 42.4; p = 0.01) was reached with impedance-dependent energy delivery (pulsed: 815.7 s ± 41.3; continuous: 715.3 s ± SD 82.2). Linear correlation between ablation duration and short axis diameter was calculated (R = 0.7). Modification of energy delivery during RF ablation with cryo-cooled applicators improves energy transfer to tissue and enables larger ablation zones. • Impedance-dependent energy delivery prevents early termination in kryo-based RF-ablation,• Impedance-dependent energy delivery enables larger ablation zones than continuous energy delivery,• Reduced current during ablation pause does not improve ablation results.

Comparison between pulsed and continuous radiofrequency delivery

Potentials arising in the pulmonary veins (PV) have been proposed to be a trigger of atrial fibrillation. Percutaneously, the best results for curative treatment of atrial fibrillation have been achieved by segmental or circumferential isolation of the PV. The purpose of our study was to determine the feasibility of ostial pulmonary vein isolation and to compare continuous radiofrequency (RF) with pulsed RF concerning homogeneity and transmurality of produced lesions. In vivo tests were performed in seven anesthetized and ventilated pigs. Under fluoroscopy and guided by intracardiac electrograms each of the 28 pulmonary veins was targeted for circumferential isolation near its ostium. After the continuous energy application in one PV-ostium the catheter was placed into the next PV-ostium and the same procedure was repeated using pulsed energy. The ablations were performed with an octapolar circumferential ablation catheter, with either continuous RF energy delivery to each electrode for 120 s or pulsed energy delivery to four electrodes simultaneously with a 5 ms duty cycle. Lesion diameter was measured with a microcaliper and homogeneity classified from 1 (highest) to 4 (least). More homogeneous lesions were produced in significantly less time with pulsed rather than with continuous energy delivery. There were no significant differences in impedance or temperature of the electrodes. We did not observe tissue carbonization or "popping," pulmonary vein stenosis, pericardial effusion/perforation at any time. Ostial ablation of the PV with pulsed energy delivery proved feasible. It was the faster and more reliable method of creating linear circumferential lesions with a maximum amount of homogeneity and transmurality. We observed no elevated risk of PV stenosis during our experiments.

Prospective randomized comparison of pulsed and continuous energy delivery in catheter ablation of common atrial flutter Ali Erdogan, Joerg Carlsson, Alexander Berkowitsch, Britta Schulte, Joerg Neuzner, Heinz F. Pitschner. Kerckhoff Heart Center, Dept. of Cardiology, Bad Nauheim, Germany

Prospective randomized comparison of pulsed and continuous energy delivery in catheter ablation of common atrial flutter Ali Erdogan, Joerg Carlsson, Alexander Berkowitsch, Britta Schulte, Joerg Neuzner, Heinz F. Pitschner. Kerckhoff Heart Center, Dept. of Cardiology, Bad Nauheim, Germany

Comparison of Pulsed Versus Continuous Radiofrequency Energy Delivery: Diameter of Lesions Induced with Multipolar Ablation Catheter

The aim of this study was to compare the efficacy of pulsed versus continuous RF energy delivery via multipolar ablation catheters. In vitro tests were performed in endomyocardial preparations of fresh bovine hearts in a both of physiological saline solution (37 degrees C) at constant flow conditions (1.5 L/min). The catheters were applied to the endocardium at a constant pressure. Energy was delivered pulsed (to 4 electrodes simultaneously, 5-ms duty cycle) or continuously (to each electrode separately). In vivo experiments were performed under fluoroscopy in eight anesthetized pigs, guided by endocardial electrograms to place the catheters in 22 different intraatrial positions. Lesion volume was calculated from measurements of the lesion diameter with a microcaliper. The homogeneity of the lesions was classified from 1 (highest) to 4 (least). More homogeneous linear lesions were produced in significantly less time with pulsed than with continuous energy delivery. There were no differences in electrode temperature or impedance values in vitro and in vivo. The results in the in vitro experiments were reproducible in the intact animal experiments. Significantly larger and more homogeneous linear lesions were created more rapidly with pulsed than with continuous energy delivery.

Pulsing microwave energy: a method to create more uniform myocardial temperature gradients.

Microwave energy has been proposed as a possible technique to create large myocardial lesions. Achieving a uniform myocardial temperature gradient during microwave ablation may prevent excessive endocardial temperatures while maintaining temperatures at depth. The goal of the current study was to examine the ability of microwave (MW) pulsing to achieve a more uniform myocardial temperature gradient. Using an in-vitro ovine endocardial model, we measured tissue temperature at 0.5-mm, 2.0-mm, and 3.5-mm depths in a circulating saline bath. MW energy was delivered at 20 W at 915 MHz for 30 seconds. Pulse configurations of 1 second on-1 second off, 3 seconds on-3 seconds off, and 5 seconds on-5 seconds off, with 30 seconds of total MW time were compared with 30-seconds continuous. Maximum temperatures at 0.5 mm were significantly lower at 63.2 +/- 5.89 degrees C for the 1-second pulse compared with 83.5 +/- 7.31 degrees C for the continuous-energy delivery. Pulse configurations 3 seconds on-3 seconds off and 5 seconds on-5 seconds off also resulted in a significantly lower surface temperature than continuous-energy delivery. However, temperature at the 2.0-mm and 3.5-mm depth created by the pulsing delivery were similar to those achieved during continuous-energy delivery. Thus, microwave pulsing achieves a lower endocardial temperature and results in a more uniform temperature gradient. These techniques may prevent the excessive endocardial damage that may result in an increased risk of thrombus formation and embolization.