Adjustable Output Power Research Articles

Design optimization and off-design performance analysis of one-dimensional supercritical CO2 Brayton cycle

Supercritical carbon dioxide (SCO2) recompression Brayton cycle (RBC) is an encouraging technology for thermal power conversion and heat harvest for a wide range of heat sources due to its high-efficiency, low auxiliary power consumption, and compact size. However, most studies on its design and off-design performance analysis have been limited to the simple zero-dimensional component models without considering aerothermodynamics and ambient conditions. In this study, we developed a set of fully one-dimensional components models for SCO2 compressors, turbines, and heat exchangers, and, then, applied them to the multi-objective design optimization of a SCO2 cycle targeting a 50 MW net power output. The cycle off-design performance analysis methods and the control strategies were developed to countermeasure the performance degradation against the varying cooling water temperatures and part loads. The multi-objective cycle design optimization demonstrates that the cycle thermal efficiency and total product unit cost can be 0.476 and 11.652$/GJ, respectively, for the 50 MW SCO2 RBC cycle. The choke margin of the main compressor is 0.136 less than that of the re-compressor, and condensation can lead to a sharp decline in efficiency under high-flow conditions, causing the earlier onset of choking. The off-design performance analysis shows that the turbine inlet pressure control improves cycle efficiency below the design point of 317 K but does otherwise above the point. In contrast, inventory control strategies can maintain stable cycle efficiency and achieve adjustable net power output between 10 % and 110 %. The findings have the potential to advance further the commercial application of SCO2 cycles in high-temperature thermal energy systems.

Optimal sizing toolbox for energy generation and storage for a nuclear hybrid microgrid

Background In recent years, renewable energy sources, such as wind, have contributed to a decrease in grid stability. This has created the need for flexible and reliable back-up energy generation. Currently this role is fulfilled by natural gas-fired power plants that are able to quickly adjust power output based on present needs. Nuclear power presents an option for a clean and reliable alternative to these natural gas-fired power plants. However, nuclear power alone is unable to provide flexible enough power generation to fill this role. Instead, nuclear power plants must be combined with strategically sized energy storage systems to effectively complement the renewable power generation. Grids such as these are generally simulated using deterministic models which are unable to account for quickly fluctuating wind power generation. This in turn creates unsafe ramp rates for the nuclear power plant. Methods The approach taken in this paper utilizes a continuous-time stochastic model to simulate a grid with wind generation, nuclear power, and an energy storage system as the only energy sources. This paper focuses on this model and a development of a GUI to form a grid sizing toolbox. This toolbox was then demonstrated with an isolated microgrid using year-long wind and load data. Wind penetration, nuclear ramp rate limitations, and storage types were all varied to observe different scenarios and determine optimal storage sizing. Results There were several outcomes from this study that can inform grid planning. Nuclear power plant size trends downwards with greater wind power generation. However, high variability of wind power limits the size reduction. Nuclear capacity factor is between 41% to 57%, dropping further as wind penetration was increased. This highlights the difficulty of maintaining high utilization in these scenarios. Conclusions All storage types had similar performance in all categories except size, in which pumped hydroelectric and compressed air storage required smaller storage sizes.

Green hydrogen to tackle the power curtailment: Meteorological data-based capacity factor and techno-economic analysis

Hydrogen production through water electrolysis stands as a potential remedy for the problem of curtailment, which refers to the deliberate downward adjustment of output power below capacity for the purpose of balancing supply and demand. This study demonstrates how comprehensive system modeling can be used to a priori assess the economics of producing green hydrogen from curtailed renewable energy of solar and wind. A case study is presented to demonstrate how actual meteorological data are utilized to anticipate the quantity of renewable energy throughout the year, which in turn is used to estimate the capacity factor and LCOH (Levelized Cost of Hydrogen) of a renewable energy/water electrolysis system. The base case of a renewable energy source of 100 MW capacity coupled with a 20 MW hydrogen production system and 20 MW transmission to the grid shows an LCOH of 5.9 USD/kg with a capacity factor of 25%. Sensitivity analysis is carried out to examine the impact of electrolyser size and the composition of renewable energy source on its capacity factor and economic feasibility. The results demonstrate that the capacity factor of an electrolysis system is not directly proportional to the renewable energy capacity but depends on the its designed capacity as well as the climate pattern and the mix ratio between solar and wind energy. Though the effect of the electrolyser’s operating range is found insignificant in a part-load operation but not in an overload operation. In addition, the effects of the capital cost, system efficiency, and electricity price on LCOH are assessed.

Multi-objective optimal siting and sizing of BESS considering transient frequency deviation and post-disturbance line overload

With the development of renewable energy sources, more frequent and severe active power disturbances emerge in power systems, and jeopardize the frequency stability and line loading security. The battery energy storage system (BESS) is able to adjust output power flexibly, and an attractive solution to improve frequency dynamics and power flow distribution. This paper proposes a multi-objective optimal siting and sizing scheme for the BESS to arrest frequency excursion and mitigate line overload under major disturbances. First, an extended average system frequency model is developed to estimate the required transient frequency regulation capability (TFRC) for frequency stability, and the post-disturbance power flows. Then, taking the required TFRC and line capacity as constraints, a multi-objective optimization model is established to minimize the life cycle cost of the BESS and generation cost. Furthermore, based on the linear weighted method, big-M method, and multi-cut generalized Benders decomposition, the intractable optimization model is transformed into a master problem for investment decision making, and a set of subproblems accounting for normal operation, frequency stability and line loading security. Additionally, the master problem and subproblems are solved iteratively to determine the location and capacity of the BESS. Case studies are conducted to validate the proposed scheme, showing superior performance in improving frequency nadir and alleviating post-disturbance line overload.

Research on the Factors Influencing the Strength of Cyclists

Individual Time Trial (ITT) is a road bicycle race where cyclists race alone against the clock. To minimize the total time cost, cyclists need to focus on the output power. In this paper, we develop models to analyze the output power of cyclists determine how to adjust the output power at every position of the course. Firstly, this article collects the real data of cyclists, which is used to find the power profile related to power and duration. Reasonable expressions of different types of cyclists of different gender are also concluded. Secondly, this article considers the cyclists in competition as a constantly charged battery and discharged. FTP is the power at which cyclists can work steadily for a long time. Therefore, this article uses FTP to represent the recovery rate of cyclists approximately. There is two basis of our model. First, maintaining a steady speed is the key to reducing the total time loss in the time trial. The next basis of our model is to divide the course into three types: uphill, downhill, and sharp turn and do the force analysis. Then, this article builds up a model which tells the cyclists how to adjust output power in the whole time trial. Fatigue is also considered in our model. the model applies to two real Individual Time Trials and one course designed by us and draws the power-distance curve correspondingly. Finally, this article analyzes the potential impact of the wind. The wind will affect the cyclists' air resistance fA. The time cost at every part is calculated to determine the proposed model's accuracy. This article also analyzes the impact of improper power adjustment.

A KNN composite-based piezoelectric helix for ultrasonic transcutaneous energy harvesting

Ultrasonic energy harvesting has been developed as a promising power solution for implantable medical devices (IMDs) to perform tasks such as diagnosis, therapy, and monitoring. However, most current ultrasonic electronics use toxic lead-based piezoelectric materials (e.g., lead zirconate titanate) as core components and feature bulk or flat structures, representing common barriers to the development of future IMDs that should be eco-friendly and long-term fixation in the implanted position. Here, we present a KNN composite-based lead-free piezoelectric helix for ultrasonic transcutaneous energy harvesting. The device contains multilayer components (a matching layer, lead-free composites, a copper foil, and a Parylene-C film) to form a final self-supporting helix harvester, which can adapt to cylindrical objects (e.g., blood vessels) to maintain fixation. Nanodomain-induced high-performance (d33 ∼ 465 pC N−1) KNN ceramic was fabricated and further processed into 1–3 composites to enhance electromechanical coupling properties and mechanical flexibility. The developed prototype can be excited ultrasonically to generate adjustable power output up to ∼22.97 mW cm−2. The generated electricity was stored in capacitors and used to operate light-emitting diodes. Further ex vivo tests showed that the device is still sufficient to support wireless energy transfer through porcine tissues, demonstrating the great potential of the lead-free piezoelectric helix for IMDs.

Cooperative adaptive inertial control for PV and energy storage units with multiple constraints

Virtual synchronous generator (VSG) control for increasing inverter-based sources is characterized by attractive features such as supporting virtual inertia, flexible design, and enhancing frequency stability. However, the performance and status of each VSG unit lead to differences in the inertial support capabilities. This paper investigates a cooperative adaptive inertial control method for multiple photovoltaic and energy storage units (PV-ESUs) to improve system inertia distribution capability during transient events. The frequency discrimination of power disturbances is realized through filters, and the operating ranges of different types of energy storage devices are determined. For the coordination problem with each VSG unit under low-frequency disturbance. The coordination controller, which regulates virtual inertia values by using technique for order preference by similarity to ideal solution (TOPSIS) evaluation algorithm, is proposed to adaptively adjust the inertial output capability of each VSG unit and provide optimized dynamic frequency support to the grid. The state of charge (SOC) of energy storage, converter adjustable capacity, the maximum adjustable output power of the system per unit time, and other influence factors are considered as actual multiple operation constraints. Finally, the effectiveness and engineering application value of the proposed control strategy is verified by the hardware-in-the-loop (HIL) experimental test platform.

Modeling of Combined Lead Fast Reactor and Concentrating Solar Power Supercritical Carbon Dioxide Cycles to Demonstrate Feasibility, Efficiency Gains, and Cost Reductions

Solar power has innate issues with weather, grid demand and time of day, which can be mitigated through use of thermal energy storage for concentrating solar power (CSP). Nuclear reactors, including lead-cooled fast reactors (LFRs), can adjust power output according to demand; but with high fixed costs and low operating costs, there may not be sufficient economic incentive to make this worthwhile. We investigate potential synergies through coupling CSP and LFR together in a single supercritical CO2 Brayton cycle and/or using the same thermal energy storage. Combining these cycles allows for the LFR to thermally charge the salt storage in the CSP cycle during low-demand periods to be dispatched when grid demand increases. The LFR/CSP coupling into one cycle is modeled to find the preferred location of the LFR heat exchanger, CSP heat exchanger, sCO2-to-salt heat exchanger (C2S), turbines, and recuperators within the supercritical CO2 Brayton cycle. Three cycle configurations have been studied: two-cycle configuration, which uses CSP and LFR heat for dedicated turbocompressors, has the highest efficiencies but with less component synergies; a combined cycle with CSP and LFR heat sources in parallel is the simplest with the lowest efficiencies; and a combined cycle with separate high-temperature recuperators for both the CSP and LFR is a compromise between efficiency and component synergies. Additionally, four thermal energy storage charging techniques are studied: the turbine positioned before C2S, requiring a high LFR outlet temperature for viability; the turbine after the C2S, reducing turbine inlet temperature and therefore power; the turbine parallel to the C2S producing moderate efficiency; and a dedicated circulator loop. While all configurations have pros and cons, use of a single cycle offers component synergies with limited efficiency penalty. Using a turbine in parallel with the C2S heat exchanger is feasible but results in a low charging efficiency, while a dedicated circulator loop offers flexibility and near-perfect heat storage efficiency but increasing cost with additional cycle components.

Direct visualisation of bubble-particle interactions in presence of cavitation bubbles in an ultrasonic flotation cell

In this study, the role of cavitation bubbles in the bubble-particle interaction dynamics was investigated using high-speed imaging. A lab-scale conceptual flotation cell was designed involving an ultrasonic field with adjustable power output and a continuous liquid recirculation stream. Coarse size range hydrophobic glass Ballotini particles were suspended in the cell by the combined action of a confined vortex and turbulence created by periodic ultrasonic pulses. Ultrasonic pulses in the liquid medium led to the generation of numerous fine size range cavitation bubbles which were observed to form particle clusters. These particle clusters were observed attaching to relatively larger size carrier bubbles forming stable bubble-particles aggregates, which subsequently floated. It was noted that a favourable state of bubble-particle interactions was achievable to produce such stable bubble-particles aggregates by suitably controlling the input power and period of the applied ultrasonic pulse.

Photosensitizer accumulation in the bladder mucosa in chronic cystitis

Purpose . To study the accumulation of photosensitizer Photoditazine in the bladder mucous in chronic cystitis. Material and methods . 22 patients with chronic cystitis were taken into the study. The time of Photoditazine accumulation in the bladder mucous was determined with a multi-channel optical fiber spectroanalyzer («LESA-01-BIOSPEC»). Photodynamic therapy (PDT) was done with laser «ATKUS-2» having adjustable output power up to 2 W and wavelength 661 ± 0.03 nm. Results . The performed fluorescence spectroscopy has revealed that the maximal accumulation time of Photoditazine in the bladder mucous in chronic cystitis is 120–150 minutes. After laser exposure, by spectroscopy finings, fluorescence intensity decreases by 72.3% which indicates a pronounced photosensitizer excitation and an active photodynamic reaction. Conclusion . The optimal time for laser photodynamic therapy in chronic cystitis is 2–2.5 hours after photosensitizer injection. Spectroscopy findings after laser exposure demonstrate the effectiveness of photodynamic therapy in chronic cystitis.

Combined low voltage ride through and power smoothing control for DFIG/PMSG hybrid wind energy conversion system employing a SMES-based AC-DC unified power quality conditioner

An Interline AC-DC unified power quality conditioner (UPQC) protection device is proposed and designed based on superconducting magnetic energy storage (SMES) in this paper to improve low voltage ride through (LVRT) capacity and smooth output power for doubly fed induction generator (DFIG)/ permanent magnet synchronous generator (PMSG) hybrid wind energy conversion system (WECS). The AC side of the proposed UPQC is connected in series with the terminal of DFIG as a dynamic voltage restorer (DVR), and the DC side of the UPQC is connected in parallel with the DC bus of PMSG for DC bus voltage maintenance and output power adjustment. For a case verification, a 4.76-H/1760-A superconducting coil (SC) is designed as an energy storage device utilized in UPQC to carry out the energy conversion. Finally, the performances of the proposed protection scheme under the conditions of wind speed variation, three-phase-to-ground fault and two-phase-to-ground fault have been presented and analyzed via simulation, to verify the effectiveness of the proposed AC-DC UPQC in DFIG/PMSG hybrid WECS.

One produced three: A capacitor-battery integration strategy in a dual-carbon device

Electrochemical energy storage (EES) devices having both high power density and high energy density are highly desirable. Although metal-ion hybrid capacitors (MIHCs) integrating a battery-type anode and a capacitor-type cathode are wished to realize this target, state-of-the-art MIHCs just showed the compromise performance between high-power supercapacitors (SCs) and high-energy metal-ion batteries. Herein, we propose a new concept of “device-level integration” to realize the integration of SC, MIHC and dual-ion battery (DIB) in one device. By coupling a mixed and pre-potassiated activated carbon (AC)/graphite anode and another mixed AC/graphite cathode in a K+-based organic electrolyte, as-built device can exhibit three distinctly different energy storage behaviors including SC, MIHC and DIB by simply tuning the applied voltage window. Consequently, this device is able to achieve the maximum power density at 0–2.8 V and the maximum energy density at 0–5.0 V, and exhibits a good combination of high power density and high energy density at 0–4.0 V. This work may open a new avenue for building advanced EES devices with adjustable power and energy output characteristics.

Nanomaterial Coating on Micro-Hotplate By EHD Inkjet Printing with in-Site Infrared Laser Heating

Introduction EHD inkjet printing was applied in the fabrication of micro gas sensors recently [1-3]. In most cases, the evaporation of the ink solvent is slow, which makes thickness and uniformity of the film difficult to control. This work introduces an IR laser heating source to the EHD printing system of previous work [2], which accelerates the evaporation of the as-deposited ink solvent on the MHP, so that thick films and even columnar structures can be deposited without the use of special ink solvent.This paper reports a novel in-situ infrared (IR) laser aided electrohydrodynamic (EHD) inkjet printing technique which can deposit hierarchical micro/nano-structured gas-sensitive materials on micro-hotplate (MHP) for micro gas sensor fabrication. Gas-sensitive materials can be deposited quickly on an MHP to form flatten thin film, thick film, and 3D columnar structures. Method The diagram of the printing system is shown in Figure 1. An 808 nm IR laser source with adjustable output power is mounted on the EHD inkjet printing system, focusing at the printing spot with a diameter of about 1 mm. The freestanding MHP with metal electrodes embedded in SiO2 membrane can be heated up to 200oC in seconds by adsorption of the IR power. After EHD printing of the ink onto the 100 µm * 100 µm area of the MHP, the IR laser is turned on with optimized output power and time interval to heat the MHP to a temperature that the solvent evaporated rapidly and the dry gas-sensitive materials are uniformly covered on the surface of the MHP. By repeating the EHD printing and IR heating process, thickness of the film increases regularly and thick film can be prepared. In the preparation of columnar structure, by shrinking the amount of ink droplet and accelerating the IR heating, a tip appears on the surface of the deposited materials. The electric field intensity is larger at the tip since it shortened the distance to the needle, therefore, the electric force drives the ink droplet to deposit on the tip and the tip continues to grow, forming a 3D columnar structure. Results and Conclusions The temperature of the MHP changes with the power of the IR laser in a linear relationship (Figure 2). The flower-like tin oxide powder doped with 3 at% palladium was prepared as the hierarchical-structured gas-sensitive material with a hydrothermal method (Figure 3). The ink was prepared by mixing the powder, DI water and surfactant in a proper proportion, and it was EHD printed on the surface of the MHP (Figure 4). Without IR heating, the solvent did not evaporate completely even after 600 s at room temperature, making it not suitable to print again. By turning on the IR laser with 450 mW for 5 s, the ink was dried and uniform thin film with thickness dfilm<1 µm was coated on the MHP as shown in figure 5 (b). Repeat the printing-heating cycle for 4 times only took 100 s, and thick film of dfilm ≈ 40 µm was obtained as shown in Figure 5 (c). Figure 6 compares the power consumption of the MHP before and after printing, which shows that the MHP with thick gas sensitive film remains good thermal isolation property. The printed 3D columnar structure with height of about 120 µm is shown in figure 5 (d). Increasing the power of the laser can accelerate the evaporation. However, when the IR laser power is more than 500 mW, the droplet on the MHP boil violently and nanomaterials splashes all around.For the first time, the IR aided EHD printing allows the printing of flatten thick gas sensitive film composed of hierarchical-structured nanomaterial on MHP. Also, the technique can further be applied in fabrication of other MEMS devices.This work is supported by the Nature Science Foundation of China (61874018 and 61274076), the Fundamental Research Funds for the Central Universities, and the Nature Science Foundation of Liaoning (20180550923).

The Temperature Behavior of Microwave Absorption of Metal Oxide Powders When Heated by a 263-GHz Gyrotron Radiation

In this paper, the temperature dependence of microwave absorption in powders of various metal oxides was studied. The powders of aluminum oxide Al2O3, zinc oxide ZnO, tungsten trioxide WO3, and titanium dioxide TiO2 were the test substances. A subterahertz gyrotron setup with a frequency of 263 GHz and an adjustable output power level from watts to 1 kW was used as a radiation source. In the experiments, the samples of the powders were heated by the radiation of the gyrotron, and at the same time, the temperature of the sample was recorded and the power absorbed in the sample was measured by the calorimetric method. The measurements were carried out in a wide range of temperatures: from several tens up to 1200 °C. The results obtained may be of both fundamental and applied interest for researchers engaged in microwave heating of materials.

Joint Workload Scheduling and Energy Management for Green Data Centers Powered by Fuel Cells

The fuel cell is a promising power source for green data centers due to its high energy efficiency, low carbon emissions, and high reliability. However, because of the mechanical limitations related to fuel delivery, fuel cells are slow in adjusting power output when the energy demand quickly changes, which is called limited load following . Many recent work have studied to mitigate the limited load following by using energy storage to adjust energy supply, but achieves limited successes because of the constraint of energy storage size. In this paper, we address this challenge by changing both energy supply and demand, via joint workload scheduling and energy management. Specifically, we consider multiple geo-distributed data centers powered by both fuel cells and energy storage. An online algorithm has been proposed to minimize the gap between energy supply and demand by jointly managing the fuel cells output and migrating workloads among data centers. Simulations results based on real-world traces show that the proposed algorithms can achieve satisfactory performance.

Mechanical Unloading of the Respiratory System during 5km Cycling Time Trials in Hypoxia

In trained endurance athletes, the ability to defend arterial oxy-hemoglobin saturation (SaO2) during high intensity constant-workload exercise in moderate hypoxia depends in part on the ability to increase minute ventilation (V̇E). Previous data have shown, however, that despite the existence of a substantial amount of ventilatory reserve (V̇Eres) in some cyclists, V̇E surprisingly does not increase during 5km time trials (5kTT) in hypoxia, despite a significant decrease in both SaO2 and mean power output (PTT) from normoxia. PURPOSE: To determine the effect of reducing the work of breathing (Wb) on V̇E, breathlessness (RPB), and PTT during a 5kTT in hypoxia in highly trained cyclists. We hypothesized no change in RPB, while V̇E would increase with an attenuated decrement in SaO2 and PTT from normoxia. METHODS: Fourteen trained male cyclists (V̇O2max = 58.7 ± 4.7 ml·kg-1·min-1) performed a 5kTT under 3 conditions at sea level: ‘CON’ (FiO2 = 0.21), ‘HYP’ (FiO2 = 0.16), and ‘HYP+He’ (FiO2 = 0.16, with balance helium). Esophageal balloons were used to assess Wb in each condition. Inspiratory capacity maneuvers were performed at each km, and flow-volume loop analyses were used to assess the %EFL and V̇Eres. The modified Borg scale (0-10) was used to assess RPB at each km. RESULTS: Wb decreased from HYP to HYP+He by 30 ± 18% (p < 0.01). Despite a substantial V̇Eres throughout CON (52 ± 44 L·min-1), V̇E was not different between CON (117.4 ± 17.9 L·min-1) and HYP (124.8 ± 17.9 L·min-1) but increased during HYP+He (139.5 ± 22.0 L·min-1; p < 0.05). While SaO2 decreased from CON to HYP by 10 ± 1% (p < 0.01), SaO2 increased by 4 ± 1% from HYP to HYP+He (p < 0.01). PTT decreased from CON to HYP (-14.2%; p < 0.01) and increased from HYP to HYP+He (+5.5%; p < 0.01). When comparing HYP to HYP+He, a significant correlation was observed between ΔSaO2 and ΔPTT (r = 0.69; p < 0.05). RPB increased from CON (6.0 ± 2.0) to HYP (7.0 ± 2.0; p < 0.05) and was unchanged from HYP to HYP+He (6.6 ± 2.0). CONCLUSIONS: In moderate hypoxia, a low ventilatory reserve does not limit 5km time trial performance, where by design, individuals are free to adjust power output. The ability to utilize ventilatory reserve while remaining below a critical threshold of perceived breathlessness appears conducive to maintaining aerobic exercise performance in moderate hypoxia.

Deposition of SiOxCyHz Protective Coatings on Polymer Substrates in an Industrial-Scale PECVD Reactor

The deposition of protective coatings on aluminised polymer substrates by a plasma enhanced chemical vapour deposition PECVD technique in a plasma reactor with a volume of 5 m3 was studied. HMDSO was used as a precursor. Plasma was sustained in a capacitively coupled radiofrequency (RF) discharge powered by an RF generator operating at 40 kHz and having an adjustable output power up to 8 kW. Gaseous plasma was characterised by residual gas mass spectrometry and optical emission spectroscopy. Polymer samples with an average roughness of approximately 5 nm were mounted into the plasma reactor and subjected to a protocol for activation, metallisation and deposition of the protective coating. After depositing the protective coating, the samples were characterised by secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). The combination of various techniques for plasma and coating characterisation provided insight into the complex gas-phase and surface reactions upon deposition of the protective coatings in the industrial-size plasma reactor.

A universal solar simulator for focused and quasi-collimated beams

This paper presents a 70-kWe indoor solar simulator for concentrating and non-concentrating solar applications. The solar simulator consists of three major components: a lamp array, an optical integrator, and a collimating lens. The lamp array consists of seven radiation modules, each comprising a 10-kWe short-arc xenon lamp coupled to a custom-designed reflector with the shape of a truncated ellipsoid. The optical integrator and collimating lens are intended for homogenizing the energy flux distribution of light from the lamp arry and reducing the divergnce angle of light. The solar simulator can produce concentrated high-flux, medium-flux and non-concentrated quasi-collimated light with continuously adjustable power output. Within a 60 mm-diameter circular target on the focal plane, the measured peak and mean radiative fluxes are 9200 kW/m2 and 5100 kW/m2, respectively, and the corresponding radiative power is 14.45 kW. For a 4 m × 3 m rectangular area illuminated by quasi-collimated light, the measured radiative flux, half divergence angle, and uniformity of the light are 0.94 kW/m2, 1.3°, and 92%, respectively. At 27% of the rated power input of the solar simulator, a parabolic trough collector illuminated by the quasi-collimated light can reach 350 °C; at 93% of the rated power input, the focused radiation can melt tantalum (melting point 3017 °C). The solar simulator provides a universal research platform for a wide range of solar energy technologies, such as solar thermal, solar thermochemical, solar photovoltaics and photocatalysis (with a minor upgrade of the spectrum).

Safety of catheter-based radiofrequency renal denervation on branch renal arteries in a porcine model.

ObjectivesWe aimed to investigate the safety of radiofrequency (RF)‐renal denervation (RDN) on branch renal arteries (RAs) in a porcine model.BackgroundThe efficacy of RF‐RDN was enhanced by treatment of the branch RA, in addition to the main RA. However, there are concerns regarding the safety of RF‐RDN on branch RA because of their smaller diameter and proximity to the kidney.MethodsRF was delivered to 24 RA from 12 swine. A total of 8 RA from 4 swine were untreated. Treated RA were examined by angiography and histopathology at 7, 30, and 90 days. Serum creatinine concentration, biophysical parameters during RF delivery, and renal norepinephrine concentration were also assessed.ResultsAngiography revealed minimal late lumen loss and diameter stenosis in the main and branch RA at any time point. There was no change in serum creatinine after RF‐RDN. Histopathologically, no augmentation of medial damage or neointimal formation was found in branch RA compared with main RA. No or minimal damage to surrounding tissues including the kidneys, ureters, lymph nodes, and muscles was observed at any time point in both the main and branch RA. Equivalent electrode temperature in the main and branch RA was achieved by automatic adjustment of output power by the generator. The renal norepinephrine concentration was significantly lower in the treated group compared with the untreated group.ConclusionsRF‐RDN on branch RA was safe in a porcine model, with stenosis‐free healing of treated arteries and negligible kidney damage at 7, 30, and 90 days.

Research on Active Power Automatic Control Strategy of Wind Farm Energy Station Access System

Wind farms are included in the grid Automatic Generation Control (AGC) will help for power system control. In order to minimize the imbalance between the active output of wind farm and the reference value, a power automatic control strategy for wind farm was proposed in the paper, which is considered the dispatching of safe operation of grid and the number of start and stop of wind turbines. The wind turbines in the wind farm were divided into three different categories according to the output characteristics and operation state of the wind turbines. By combining with the energy storage control of wind farm, the selection of power regulation turbines was carried out while considering the constraints such as the climbing rate and the power distribution value of the wind turbines. the proposed method effectiveness was verified with simulation example analysis, which could take full account of the individual information of wind turbines and make the output power adjustment of wind farm reach the optimization effect both in economy and safety.