Output Power Profile Research Articles

Daily dynamic performance of a solar chimney power plant integrated by waste heat recovery

The numerical simulation of a large-scale hybrid SCPP (an additional waste heat source is connected to the collector-to-chimney transition section) is performed based on a transient model. The daily dynamic profiles of power output, mass flow rate of condensed water and temperature at a representative point for continuous 24 h are obtained, as well as the daily total electricity output and the power difference-to-average ratio (PDAR) defined as the ratio of the peak-valley difference of the daily power profile to the daily average. The effect of effective waste heat flux (EWHF) on the power output by changing the solar radiation intensity is evaluated. Results show that the incorporation of waste heat with enough high heat flux into SCPP causes clear enhancement of the power output. With the increase in the EWHF from 0 to 2 GW, the daily total electricity output increases by 119.99% and the PDAR drops from 1.61 to 0.8. Moreover, the PDAR is smaller for weaker solar radiation. This indicates that enough high waste heat flux helps to flatten the daily profile of the plant power output, especially for weak solar radiation. While low waste heat flux has little influence on the power output and the PDAR.

Determining the augmentation ratio and response behaviour of a Diffuser Augmented Wind Turbine (DAWT)

An experimental study was performed on a full-scale DAWT to understand its response behaviour to changes in wind speed fluctuations. A novel diffuser was designed from the results of previous numerical studies and was manufactured using lightweight materials. The resultant DAWT was made portable and tested in three wind directions. Wind speeds, wind directions and output power was recorded from both the bare wind turbine i.e. before it was applied with the diffuser and then the resultant DAWT. From experimental testing of the DAWT, wind speeds to the rotor were increased by 136% from 1.02 m/s to 2.41 m/s. The augmentation ratio was evaluated at 8.32 and the DAWT exhibited better responsive behaviour than the bare wind turbine in terms of matching the expected output power profile and a smaller response time.

Thermodynamic performance evaluation of a geothermal ORC power plant

This work presents a thermodynamic evaluation of an operating geothermal ORC power plant. The model is realized by using measured data of AFJET geothermal power plant which has 3MWe net power output capacity. Thermodynamic assessment of the system is conducted to see the energy and exergy efficiencies of each component, and the whole plant. Additionally, a parametric study is conducted to understand the effects of various operating conditions on the system performance. Different from previous studies, daily and annual net power output profile of the plant was investigated with considering ambient temperature fluctuations. Results revealed that net power output can drop as significant as 36% from winter to summer months. Also, between nighttime to daytime, the net power expectation may decrease by 5%. The exergy destruction rate of re-injection process constitutes the most significant part (38.1%) of the total exergy destruction of the plant. The conversion and exergy efficiencies of the system are calculated as 11.24% and 39.03%, respectively. Also, to enhance the performance of the plant, an internal heat recovery system is recommended. The analyses show that the implementation of an internal heat recovery system improves the energy and exergy efficiencies of the plant by 15%.

A New Design Approach to Mitigating the Effect of Parasitics in Capacitive Wireless Power Transfer Systems for Electric Vehicle Charging

This paper introduces a new design approach to mitigate the effect of parasitic capacitances and achieve high performance in large air-gap capacitive wireless power transfer (WPT) systems for electric vehicle (EV) charging. In a capacitive WPT system for EVs, the vehicle chassis and roadway introduce multiple parasitic capacitances that can overwhelm the coupling capacitance and severely degrade power transfer and efficiency. The proposed approach addresses this challenge by employing split-inductor matching networks, which allow the complex network of parasitic capacitances to be simplified into an equivalent four-capacitance model. The shunt capacitances of this model are directly utilized as the matching network capacitors, hence, absorbing the parasitic capacitances and eliminating the need for discrete high-voltage capacitors. A systematic procedure is developed to accurately measure the equivalent capacitances of the model, enabling the system’s performance to be reliably predicted. The proposed approach is used to design two 6.78–MHz 12-cm air-gap prototype capacitive WPT systems with capacitor-free matching networks. The first system transfers up to 590 W using 150-cm2 square coupling plates and achieves an efficiency of 88.4%. The second prototype system transfers up to 1217 W using 118-cm2 circular coupling plates, achieving a power transfer density of 51.6 kW/m2. The measured output power profiles of the two systems match well with their predicted counterparts, validating the proposed design approach.

Transient Gas Saturation in Porous Transport Layers of Polymer Electrolyte Membrane Electrolyzers

Intermittency of renewable energy sources, such as wind and solar, remains as a major barrier to the establishment of a sustainable energy infrastructure (1). Balancing the supply of intermittent energy with demand requires an energy storage technology capable of operating under dynamic conditions. Over the last decade, polymer electrolyte membrane (PEM) electrolyzers attracted much attention as the ideal energy storage technology for renewable energy generators (2). PEM electrolyzers are favorable due to their wide operating current density range (0.6 – 2.0 A/cm2) and rapid response to dynamic changes (3). However, PEM electrolyzers need to become significantly more efficient to become commercially-viable energy storage technology (4). A major source of inefficiency stems from the undesired accumulation of oxygen gas in the anode porous transport layers (PTLs), which leads to blockage of reaction sites and water transport pathways in the PTL (5). The overpotential associated with this effect is termed mass transport overpotential, and it can contribute up to 25% of the total overpotential (6). Furthermore, mass transport overpotential could increase exponentially at higher current densities (7). Despite the extensive studies on gas transport in the PTL over the last decade, the effect of dynamic operating condition on the transient gas distribution in the PTL remains unknown. Understanding the transient gas transport through the PTL is an important first step for coupling PEM electrolyzer systems with intermittent renewable energy sources. In this work, we studied gas transport through the PTL under dynamic operating conditions via in operando synchrotron X-ray imaging. Specifically, we used synchrotron X-ray imaging with high spatial (6.5 µm/pixel) and temporal (2.5 frames per second) resolution to quantify the change in gas volume in the PTL under changing current densities. We observed that the gas volume oscillated at a constant amplitude with a similar frequency over a series of repeating step currents (Fig. 1). We also operated the electrolyzer using a real output power profile acquired from a wind turbine. The results provide insights on the transient behaviour of gas distribution in the PTL of PEM electrolyzers coupled with renewable energy sources. References J. A. Turner, Science., 285, 5428 (1999).O. Schmidt, A. Gambhir, I. Staffell, A. Hawkes, J. Nelson and S. Few, Int J Hydrogen Energy., 42, 52 (2017).M. Carmo, D. L. Fritz, J. Mergel and D. Stolten, Int J Hydrogen Energy., 38, 12 (2013).C. K. Mittelsteadt, ECS Transactions., 69, 17 (2015).Ö F. Selamet, M. C. Acar, M. D. Mat and Y. Kaplan, Int.J.Energy Res., 37, 5 (2013).M. Suermann, T. J. Schmidt and F. N. Büchi, Electrochim.Acta., 211(2016).S. Sun, Y. Xiao, D. Liang, Z. Shao, H. Yu, M. Hou and B. Yi, RSC Adv., 5(2015). Figure 1

Macrobending SMS fiber-optic anemometer and flow sensor

Abstract We report a simple, high sensitivity, good resolution and low-cost fiber-optic anemometer and flow sensor based on reflective single mode-multimode-single mode structure bent by air flow. The dragging force on the multimode section causes it to bend resulting in multimodal interference (MMI) effects which are related to the fluid velocity and flow rate. Bending effects on the output power profile are investigated and numerical simulation combined with experimental data demonstrate that the output power intensity may increase or decrease with the rise of curvature, depending on MMI conditions and field deformation. The sensor behavior with air flow velocity is evaluated by spectral analysis using a variety of methods as wavelength shifting of a selected peak and output power intensity of selected wavelength and output power intensity of selected points. Experimental tests using air stream inside a wind tunnel provided a reliable dynamic range from 4 to 10 m/s. Peak sensitivities of 435.13 pm/(m/s) with resolution of 17.4 × 10−3 m/s for wavelength shifting and 2.62 dB/(m/s) for output power intensity are obtained. These results assure that the sensor can be effectively used in a wide variety of applications, such as anemometer and flow rate meter.

Integrative Sizing/Real-Time Energy Management of a Hybrid Supercapacitor/Undersea Energy Storage System for Grid Integration of Wave Energy Conversion Systems

Grid-connected operation of an offshore renewable energy source (RES), comprising a wave energy converter (WEC), a hybrid supercapacitor (SC)/undersea energy storage system (HESS), and a set of power electronics converters (PECs), is investigated. Since the HESS components feature distinctive power and energy characteristics, the effect of the operating point on their storage capacity must be considered. Thus, an integrative sizing and real-time energy management strategy (EMS) based on reinforcement learning (RL) is proposed. Effectiveness of the sizing approach is examined by comparing the power and energy capacity of the HESS components under the proposed method and when they are sized individually. A similar WEC output power profile is used and it is assumed that the storage components, as hybrid or individually, counteract the power fluctuations. To verify the adaptability of the RL-based EMS (RLEMS), different power profiles are used in the learning and testing phases. Real-time implementation feasibility is validated through real-time simulations. The obtained results confirm that the power and energy capacity of the HESS components are significantly reduced when EMS is considered in the sizing stage. Further, the WEC output power could be regulated by the RLEMS, even in the presence of serious imbalances between harvested and dispatched wave energies.

Structural Design of Partitioned Stator Doubly Salient Permanent Magnet Generator for Power Output Improvement

Partitioned stator doubly salient permanent magnet generators (PS-DSPGs) have been extensively used for electrical generation mainly due to their high reliability, high electromotive force (EMF), and high-power output. Therefore, we aim to improve the output power of a PS-DSPG by designing the optimal configuration of generator pole structure. Electrical characteristics including the magnetic flux linkage distribution, phase EMF, cogging torque, voltage regulation, and power output profile were characterized by using the finite element method. After optimizing the generator pole structure including the angle of air gap arc width, it was found that the proposed PS-DSPG with 18/15 (stator/rotor) pole structure with optimized air gap arc width could produce higher EMF of about 23.24% than a conventional structure because this structure has the suitable number of pole structures. Also, an analysis of voltage regulation and power output profiles under the loaded condition were carried out, and it was indicated that the PS-DSPG based on the suitable 18/15-pole structure could provide the best machine performance where the output power is 11.63% higher than the conventional structure. Hence, the proposed PS-DSPG with 18/15-pole structure can appropriately be utilized for electrical generation, especially in low-speed operated generator applications.

On-line power management for grid-connected solar chimney power plants with various heat storages

Integration with the grid is the general trend in the development of solar chimney power plant (SCPP). It is important to dispatch the electricity from the grid-connected SCPP in a proper manner. The power dispatching scheme would be changed by various heat storages which can control the power output profile of the SCPP. Optimal design of the heat storage in the SCPP aiming at minimizing the total electricity dispatched (TED) remains unknown. The governing equations regarding air flow and heat transfer are solved to realize 24-hour simulation of SCPP. The power dispatching scheme is then available based on the calculated power output profile and a specified load curve using the integration method. The influences of various heat storages and various solar radiation intensities on power dispatching are evaluated. Results show the water-filled systems perform better than natural grounds in reducing the TED generally. The TED can be a design index of the heat storage in the SCPP. The power dispatching schemes are classified into three categories according to various solar radiation intensities. The water-filled heat storage of 0.2 m in thickness performs the best in this paper.

Optimized light delivery probe using ball lenses for co-registered photoacoustic and ultrasound endo-cavity subsurface imaging

An optimized hand-held photoacoustic and ultrasound probe suitable for endo-cavity tumor subsurface imaging was designed and evaluated. Compared to previous designs, the prototype probe, consisting of four 1 mm multi-mode optical fibers attached with 1.5 mm diameter ball-shaped fiber tips sandwiched between a transvaginal ultrasound transducer and a custom-made sheath, demonstrated a higher light output and better beam homogeneity on tissue subsurface. The output power and fluence profile were simulated for different design parameters. A camera recorded fluence profiles through calibrated intralipid solution at various imaging depths. The light delivery efficiency was experimentally compared with and without the ball lenses, based on ex-vivo imaging of human colorectal cancer and in-vivo imaging of a palmar vein proximal to the human wrist. The simulations and experiments demonstrated that ball-shaped fiber tip design can achieve homogeneous fluence distribution on tissue subsurface with acceptable light output efficiency, suggesting its clinical potential for in-vivo endo-cavity imaging.

Core temperature up to 41.5ºC during the UCI Road Cycling World Championships in the heat

ObjectiveTo characterise the core temperature response and power output profile of elite male and female cyclists during the 2016 UCI Road World Championships. This may contribute to formulating environmental heat...

Optimal joint strategy of wind battery storage unit for smoothing and trading of wind power

Wind power is intermittent and causes problems to the operation of electric power systems. This leads to the need for flexible battery storage units to smooth the wind power output. However, the volatile profile of wind power output affects the operational performance of battery units. We propose here an optimisation model to define the optimal hourly commitment of a wind battery storage unit while also including relevant operational constraints for the battery and modelling its degradation. Results show that although the wind farm can have reduced revenue in the shorter-term because of these constraints, the revenue of the wind farm increases in the longer-term and the lifetime of the battery is also extended.

Flexible single-mode delivery of a high-power 2 μm pulsed laser using an antiresonant hollow-core fiber.

We demonstrate flexible single-mode transmission of a high average power 2µm nanosecond pulse using antiresonant hollow-core fibers (AR-HCFs). 39.1W average power is delivered using a coiled 1.7m AR-HCF, which is designed for single-mode guidance and good higher-order mode suppression. The effect of bending on the fiber output power and beam profile is also investigated. The Gaussian-like output beam profile is maintained up to a 7.5cm bending radius. This is the highest average power delivered by a flexible long HCF in this wavelength without the need for an enclosed controlled environment, to the best of our knowledge.

Protocol for Determining Ultraviolet Light Emitting Diode (UV-LED) Fluence for Microbial Inactivation Studies.

Determining fluence is essential to derive the inactivation kinetics of microorganisms and to design ultraviolet (UV) reactors for water disinfection. UV light emitting diodes (UV-LEDs) are emerging UV sources with various advantages compared to conventional UV lamps. Unlike conventional mercury lamps, no standard method is available to determine the average fluence of the UV-LEDs, and conventional methods used to determine the fluence for UV mercury lamps are not applicable to UV-LEDs due to the relatively low power output, polychromatic wavelength, and specific radiation profile of UV-LEDs. In this study, a method was developed to determine the average fluence inside a water suspension in a UV-LED experimental setup. In this method, the average fluence was estimated by measuring the irradiance at a few points for a collimated and uniform radiation on a Petri dish surface. New correction parameters were defined and proposed, and several of the existing parameters for determining the fluence of the UV mercury lamp apparatus were revised to measure and quantify the collimation and uniformity of the radiation. To study the effect of polychromatic output and radiation profile of the UV-LEDs, two UV-LEDs with peak wavelengths of 262 and 275 nm and different radiation profiles were selected as the representatives of typical UV-LEDs applied to microbial inactivation. The proper setup configuration for microorganism inactivation studies was also determined based on the defined correction factors.

Modeling and Sizing of an Undersea Energy Storage System

This paper presents modeling and sizing of an undersea energy storage system (USS). The USS, which is placed at the seabed, consists of a concrete sphere, a reversible pump-turbine unit, a permanent magnet synchronous machine, and a steel pipe through which water flows into/out of the sphere from/to the deep ocean. A novel mathematical model is derived to describe the governing equations of the USS operation. It is assumed that the USS operates in parallel with a direct-drive wave energy converter (DDWEC) and a novel sizing algorithm is developed to obtain the required USS capacity/size for regulating the DDWEC output power fluctuations during a designated period of time. In order to determine the DDWEC output power profile, wave spectrums are required. Real significant wave height and dominant wave period data, which are measured and collected by a buoy station in the Gulf of Maine, are used to generate wave profiles based on the modified two-parameter Pierson-Moskowitz spectrum. Eventually, Monte Carlo simulations with a thousand generated wave profiles are carried out to determine the optimal size of the USS for all possible scenarios. Furthermore, through promising results obtained from hardware-in-the-loop studies, the effective role of the USS in regulating the wave energy converter output power fluctuations is demonstrated.

A multi-point kinetics based MIMO-PI control of power in PWR reactors

Nodal dynamic modeling of a PWR reactor core has been carried out to provide a reliable basis for multivariable control of the load following operation. A Two- Input/ Two Output (TITO) plant is developed accordingly. The overall output power and the pertained axial offset are regulated concurrently within a multivariable PI control framework. To this end the analogous problem of power regulation in the upper and lower half cores is addressed. Control rod movement and boric acid concentration are set as the control inputs. Davison tuning strategy which takes into account the steady state gain matrix of the plant has been employed as an easily implementable approach to provide the intended PI parameters. The overall control strategy shows quite satisfactory tracking performance of the desired output power and flux tilt profiles while a safe level of the controlling signals is obtained.

CIGS Photovoltaics For The Urban Tropics

A study was done to compare the energy yield performance of CIGS versus MC-Si solar panels. Our studies show that the yield of both the panels are comparable, with a difference of only 0.7% with the MC-Si a bit higher. However that is within the limits of power tolerance for the panels and is not conclusive. A sunny day output power profile shows the CIGS panels have a significant advantage during the noon hours with a lower voltage drop and higher hourly specific yield. Our cost analysis of CIGS solar panels show that they are potentially cheaper than aluminum composite panel cladding (including system) and only slightly more expensive than ceramic tiles (panels only). Our analysis of the solar insolation (PSH) on east and west facing sidewalls shows they are about half the insolation on the roof. Although this increases the payback period, one would need to subtract the original potential cost of the façade that it has replaced. The use of PV panels also effectively creates a double skin façade structure and provides additional insulation to the building. This suggests that one could install BIPV solar as an alternative to the traditional building materials such as ceramics and aluminum composite panels at comparable costs.

Carrier Leakage Dynamics in Terahertz Quantum Cascade Lasers

We analyze the output power versus temperature characteristics of two GaAs/Al0.15Ga0.85As terahertz quantum cascade lasers (THz-QCLs) with maximum operating temperature $T_{max}=200$ and 177 K as well as of one GaAs/Al0.30Ga0.70As THz-QCL with $T_{max}=150$ K and identify the thermally-activated leakage paths responsible for the laser performance degradation as the temperature increases. We identify the specific carrier leakage path active in each THz-QCL structure and are able to reconstruct the output power versus temperature profile over the entire laser operation range. We find that using high barriers in the active region design virtually eliminates carrier leakage from the upper laser level into the continuum, opening a non-radiative scattering path from the upper into the lower laser level parallel to standard electron-LO-phonon emission. This effect, together with the reduced leakage from the lower laser level into the continuum in the high-barrier device, significantly contributes to the $T_{max}$ decrease from 177 to 150 K. We further show how electron leakage from the lower laser level into the continuum is enhanced in a GaAs/Al0.15Ga0.85As design with thin barriers, significantly improving the laser performance ( $T_{max}=200$ K). Finally, we propose future design strategies for highly temperature-insensitive THz-QCLs. Our approach offers a straightforward method to analyze and troubleshoot thermally-activated carrier leakage dynamics in THz-QCLs.

Power Smoothing Control of PMSG Based Wind Generation Using Supercapacitor Energy Storage System

AbstractThis paper proposes an efficient power smoothing control strategy for variable speed grid connected permanent magnet synchronous generator (PMSG) based wind turbine generator (WTG) with supercapacitor energy storage system (SCESS). As WTG installations are increasing, these systems generate a fluctuated output power as a result of varying wind speed and need to have a power smoothing capability to have a smooth output power profile. The optimal size of the SCESS is determined and a controller is proposed and implemented to continuously charge and discharge the SCESS to achieve its objectives. The SCESS is exploited to minimize the short term fluctuation to have a smooth power profile during normal operation. A bi-directional buck boost converter is used to integrate the SCESS with the system. Two back to back connected three level Neutral Point Clamped (NPC) converters are used for the power conversion. The control strategy and the system model have been developed for the NPCs, the buck boost converter and the variable speed WTG system. The Real Time Digital Simulator (RTDS) based results conducted on 2 MW/4 kV PMSG verify the effectiveness and superiority of the proposed controller.

Evaluation of effect of diurnal ambient temperature range on solar chimney power plant performance

This paper conducts numerical simulations of a large scale solar chimney power plant (SCPP, also called solar updraft power plant) based on an assumed expression of daily ambient temperature profile with a constant peak. It then evaluates the influence of the diurnal ambient temperature range (DATR) on the performance of the large scale SCPP. Results indicate that larger DATR accompanied by a bigger drop in ambient temperature at night increases the plant power output considerably during nighttime but decreases the power output during daytime noticeably. This is because larger DATR leads to more heat released from the thermal storage layer to produce more power during nighttime, and less heat for less power during daytime at a given solar radiation input. In this case, only a little increase in daily total power output but a significant drop in the daily power peak-to-valley ratio (PVR) are reasonable. It is also found that DATR acting as a meteorological resource for SCPPs is not as important as solar radiation, but as high humidity, in terms of enhancing the power potential of the plants. Compared to the humidity and solar radiation intensity, DATR is a good factor in smoothing daily profile of the plant power output.