Combined Output Power Research Articles

Parametric study and working fluid selection of the parallel type organic Rankine cycle and ejector heat pump combined cycle

To solve the problem of low thermal efficiency and single output form of the basic organic Rankine cycle, a parallel type organic Rankine cycle and ejector heat pump combined cycle is proposed. By deeply utilizing the energy of the low and medium temperature heat source, the system can provide different proportions of power and heating water according to users’ demands. Considering the factors of performance, environmental impacts, flammability, and turning point temperature, five working fluids are selected (i.e., R236ea, R123, R245fa, R365mfc, and R141b). Parametric analysis of the system is performed by constructing the thermodynamic model. Different operating modes of the system are defined according to different heating/power ratios. The results show that each working fluid has its optimal generator temperature to optimize the net power output efficiency. R236ea is more suitable for the system with a net power output efficiency of 6.58% and an exergy efficiency of 42.24%. Compared with the series type combined cycle, the parallel type combined cycle net power output increased by 5.08% and heating capacity increased by 20.71%. This paper can guide the efficient construction of low and medium temperature cogeneration systems.

Development of all-fiber coherent beam combining optical system toward higher output of the fiber laser

In this paper, the authors report that they have developed a low-noise and high gain all-fiber using a coherent beam combining (CBC) system. The CBC optical amplifier system has a feature in which only correlated signal light is combined; however, amplified spontaneous emission (ASE) is not added. Hence, the combined output power increases about twice the signal output power. On the other hand, the power of ASE does not change compared to a conventional amplifier. Thus, the gain and the noise figure can be improved compared to the conventional amplifier. In this research, because the excitation wavelength of erbium doped fiber amplifier is 1480 nm, the minimum value of the theoretical noise figure is 5 dB. As an example, the optical amplifier system proposed in this paper had the small-signal gain of 37.25 dB and the noise figure of 5.60 dB, whereas the conventional optical amplifier system had the small-signal gain of 34.26 dB and the noise figure of 7.44 dB. As a result, we successfully decreased the noise figure by 1.84 dB and increased the small-signal gain by 2.99 dB by using the all-fiber CBC optical amplifier system.

In-phase and out-of-phase pitch and roll oscillations of model wind turbines within uniform arrays

We experimentally explored the impact of in-phase and complete out-of-phase pitch and roll oscillations on the mean power output and the structure of the power fluctuations of turbines within 3×2 uniform arrays. The flow past selected configurations was also characterized with hotwire anemometry. The parameter space included combinations of three amplitudes and two frequencies of the turbine oscillations, and two turbine layouts; measurements with fixed units are also included for comparison. Results show that the structure of the flow past the wind-turbine arrays was significantly affected by the frequency of the tower oscillations. The turbines under in-phase pitching induced a signature that extended in the intermediate wake, which was measured up to 7 rotor diameters downwind of the last row of turbines. The roll oscillations produced an increase of the combined power output independent of the amplitude and frequency of the oscillations, where the complete out-of-phase motions resulted in larger values with a maximum at the largest amplitude of oscillations (β=20°) of over than 10%. Opposite behavior occurred with the turbines under pitching, which led to negligible changes or decrease of the combined power with a maximum reduction of ~10%. The spacing of the turbines substantially affected the power from the roll motions; however, this was not the case for the pitching. Finally, an inspection of the cross-correlation of the instantaneous power output of the turbines in the first and second rows revealed the strong modulation of the induced motions on the structure of the power fluctuations.

Multi-mode analysis of a CO2-based combined refrigeration and power cycle for engine waste heat recovery

To realize the adjustable allocation of refrigeration and power in a combined refrigeration and power cycle, this study proposes a multi-mode cycle using CO2 as the working fluid. A refrigerated truck is selected as the research objective, the refrigeration demand and power demands of which vary frequently with different transportation conditions. The proposed system is driven by the exhaust gas of the main diesel engine and can replace the original refrigerator and related small-scale diesel engine. Three operating modes can be realized for different energy demands: full refrigeration output, combined refrigeration and power output, and full power output. The results indicate that the proposed system exhibits considerable potential for energy saving and diversified energy supply capacity. Following optimization of the configuration and parameters, the proposed energy solution (engine + proposed system) under the mode of combined refrigeration and power output can achieve a 2.9% fuel saving and 4.8% power increase simultaneously versus the original energy solution (engine + refrigerator) under refrigeration condition, 3.4% fuel saving and 1.6% power increase simultaneously under freezing conditions. The fuel economy is correspondingly improved 7.4% and 4.9%. Moreover, the proposed method can provide greater refrigeration and power capacities under the full refrigeration output and full power output modes.

Combined cycle gas turbine power output prediction and data mining with optimized data matching algorithm

Electrical power output (PE) for a combined cycle gas turbine (CCGT) consisting of 9568 data records collected over a 6-year period is evaluated by the transparent open box (TOB) machine-learning method to provide accurate PE predictions and insight to prediction errors. The PE predictions derived by applying the TOB optimized data matching technique are more accurate than published predictions for the dataset from fifteen correlation-based, machine-learning algorithms. TOB achieves this high-accuracy using a tuning subset of < 150 (~ 1.5%) data records. Its accuracy is confirmed by testing the optimized solutions against all dataset records in 15 runs spread across five shuffled datasets. The dataset has a few extreme outliers associated with its four independent variables and these negatively impact the prediction accuracy of machine-learning methods. Through its transparency and forensic-like auditability of its calculations for individual data records, the TOB algorithm is able to mine the dataset to provide useful insight to the interactions of the outliers with other data records. This enables a filtered dataset (9533 records), excluding 35 carefully selected data records, to be customized to deliver much improved prediction accuracy (RMSE = 2.89 MW). Mining the dataset also reveals significant differences in prediction accuracy achieved for different sectors of the PE distribution. This insight identifies that prediction accuracy could be further improved by dividing the dataset into separately optimized subsets, three along its main PE trend plus a fourth, small subset consisting of the outliers. The TOB algorithm demonstrates its value as a machine-learning tool capable of generating accurate predictions and easily auditable data mining. It is well suited for CCGT efficiency and performance optimization.

Adsorptive removal of micropollutants from wastewater with floating-fixed-bed gasification char

The global detection of organic micropollutants (OMPs) in waterbodies and the search for low-cost alternatives to fossil activated carbon have fostered research on the application of modified biochars in complex wastewater treatment plant (WWTP) effluents. Gasification char – a promising prospect for adsorptive OMP removal – was obtained as by-product in a novel, multi-staged gasification process. The gasification system was designed for medium-scale energy production (530 kW combined heat and electrical power output) from spruce woodchips and relies on a floating-fixed-bed gasifier with a preceding pyrolysis step. The resulting floating-fixed-bed gasification char (FFBC) ‘as-is’ – i.e. without further modification – and a commercial powdered activated carbon (PAC) were used in adsorption, desorption and kinetic assays with pharmaceuticals, X-ray contrast media, and industrial chemicals, in order to test the suitability of FFBC as OMP adsorbent in different water matrices (spiked water and WWTP effluent). OMP levels were quantified via HPLC or HPLC-MS/MS and Langmuir and Freundlich isotherm fitting was performed. The characterization of FFBC showed a high C-content (91.43%), low ash-content, porous texture (ABET = 308.15 m2 g−1), and aromatic, heterogeneous structure (confirmed via FTIR) with basic character (pH = 9.50). For both tested adsorbents, high removal rates >90% of OMPs with high logD were found at an equivalent dosing of 60 mg l−1 FFBC ≈ 10 mg l−1 PAC, whereas X-ray contrast agents exhibited lower affinity. The governing removal mechanisms are hydrophobic and π-interactions, pore-size effects and – to a limited extent – hydrogen bond formation. Dissolved organic matter in WWTP effluent inhibits OMP adsorption, as observed in decreasing isotherm fitting parameters. The investigated bio-adsorbent – derived from renewable energy, regional supplies, and a process lean in the use of chemicals – could be an inexpensive alternative in adsorptive wastewater treatment.

Experimental and theoretical analysis of hybrid concentrated photovoltaic/thermal system using parabolic trough collector

In the current work, a hybrid concentrated photovoltaic thermal system was designed and coupled with a parabolic trough collector and investigated theoretically and experimentally for combined heat and power output. In the design, a photovoltaic module was mounted on a flat surface of parabolic trough absorber tube having semi cylindrical shape. A provision was made to cool photovoltaic panel from both the surfaces by flowing water through the absorber tube as well as the annulus of between absorber tube and glass cover. The model was developed using first law of the thermodynamics and then validated using experimental data generated through the fabricated setup. During the experimentation, the annulus flow rate was varied from 0.008 kg/s, 0.017 kg/s and 0.025 kg/s and inner flow rate was varied from 0.075 kg/s, 0.083 kg/s and 0.091 kg/s. The field testing results showed the mean overall efficiency of system obtained as 61.42%, 64.61% and 66.36% for inner tube flow rate of 0.075 kg/s, 0.083 kg/s and 0.091 kg/s respectively for annulus flow rate of 0.008 kg/s. The theoretical results of hybrid system obtained from the simulation are in good agreement with the experimental data. In the end environmental cost analysis was also carried out for the proposed system.

Control Strategy of the Pumped Storage Unit to Deal with the Fluctuation of Wind and Photovoltaic Power in Microgrid

With the development and utilization of distributed energy and microgrid, distributed energy storage has become a new development trend. However, small pumped storage units have the advantages of flexible engineering location, low investment, quick effect, low requirements on transmission lines, and a better solution to the peak load demand of the system. Therefore, it is more and more used in the microgrid, and it conducts joint dispatching with wind power, photovoltaic, and other clean energies. To solve the capacity problem of small pumped storage units within the microgrid, a new control strategy is proposed in this paper. Two pumped storage units are used for joint operations. Taking the smoothed combined output power of wind power, photovoltaic power, and pumped storage power as the target, and considering the limitations of transmission lines, the constraints of wind power and photovoltaic power fields as well as the restrictions of pumped storage power units and corresponding reservoirs are taken into account. In this paper, social particle swarm optimization (SPSO) with improved weight is used to calculate and solve the model. The effectiveness of the new control strategy is verified.

Design and Analysis of a Hybrid Solar and Vibration Energy Harvester

Abstract The performance of the small-scale stand-alone energy harvesters can be improved by implementing a hybrid energy harvesting technique. This paper aims at presenting the design and characterization of a hybrid energy harvester that can simultaneously harvest energy from mechanical vibration and solar radiation by combining piezoelectric, electromagnetic, electrostatic, and photovoltaic mechanisms. The hybrid device consists of a small high-efficiency solar panel and a bimorph PZT cantilever beam having a cylindrical tip magnet and two sets of capacitors (comb electrodes) attached on two sides of an ASTM 6061 T-6 Aluminum substrate. All the transducing sections of the configuration are interconnected by a smart hybrid electric circuit having a common optimum load resistance, an energy storage, and a microcontroller to generate and store combined power output when subjected to transverse vibration and solar radiation. The initial bias-voltage input required for the electrostatic mechanism is either obtained from the photovoltaic system or taken from the storage through the microcontroller. Results for the maximum power output are obtained at the fundamental resonance frequency of the vibrating cantilever beam. As the hybrid design allows a combined power harvesting method, more power is generated with better conversion efficiency than those obtained by stand-alone mechanisms. In addition to the power calculation, the study includes a stress and fatigue analysis of the cantilever beam using the finite element method to investigate the stress-life criteria of the hybrid structure.

Genetic Algorithm Approach to Design of Multi-Layer Perceptron for Combined Cycle Power Plant Electrical Power Output Estimation

In this paper a genetic algorithm (GA) approach to design of multi-layer perceptron (MLP) for combined cycle power plant power output estimation is presented. Dataset used in this research is a part of publicly available UCI Machine Learning Repository and it consists of 9568 data points (power plant operating regimes) that is divided on training dataset that consists of 7500 data points and testing dataset containing 2068 data points. Presented research was performed with aim of increasing regression performances of MLP in comparison to ones available in the literature by utilizing heuristic algorithm. The GA described in this paper is performed by using mutation and crossover procedures. These procedures are utilized for design of 20 different chromosomes in 50 different generations. MLP configurations that are designed with GA implementation are validated by using Bland - Altman (B-A) analysis. By utilizing GA, MLP with five hidden layers of 80,25,65,75 and 80 nodes, respectively, is designed. For aforementioned MLP, k - fold cross-validation is performed in order to examine its generalization performances. The Root Mean Square Error ( R M S E ) value achieved with aforementioned MLP is 4.305 , that is significantly lower in comparison with MLP presented in available literature, but still higher than several complex algorithms such as KStar and tree based algorithms.

An integrated heat recovery and storage system for a residential building

AbstractIn this article, a novel multigeneration system is proposed which can produce four useful outputs for a small residential building located in Ottawa, Ontario (Canada). The residential building has a total of six floors, 24 units, and houses ~96 residents. The system uses parabolic solar collectors to superheat steam, which then provides energy to the remainder of the cycle. During the nighttime or poor weather conditions, the system can still function effectively by using hot and cold molten salt storage tanks. The molten salt storage tanks contain mixtures of NaNO3 and KNO3, at 45% and 55%, respectively. The proposed system has an overall energetic and exergetic efficiencies of 43.33% and 60.55% during the heating process, and 38.42% and 70.87% during the cooling process, respectively. To effectively operate, the system must consume 2256 kW of solar energy. The high and low‐pressure turbines have a combined power output of 713.8 kW, at an isentropic efficiency of 90%. The heating and cooling loads output from the condenser and the evaporator were calculated to be 471.7 and 316 kW, respectively. The load produced from this system can adequately satisfy the peak load conditions. The cascade system added to the evaporator will enable it to act more effectively compared to the condenser in terms of the coefficient of performance (COP). Also, the desalination system is capable of meeting the daily water requirements of 654.12 m3/day, by consuming untreated water at a flow rate of 84.71 kg/s and releasing distilled water at 7.55 kg/s.

Integrating wind, photovoltaic, and large hydropower during the reservoir refilling period

Hydropower facilities are an ideal solution to complement the intermittent production of energy from wind and solar photovoltaic facilities in electric power systems. However, adding this task to the multiple diverse duties of a reservoir (e.g., flood mitigation, water supply, and power generation) poses a challenge related to pursuing multiple and sometimes conflicting objectives. This study proposes an approach for integrating hydro, wind, and photovoltaic power during a reservoir’s refill period. Specifically, this approach simultaneously minimizes the fluctuation in the combined power output of these three resources and maximizes their combined power generation while adhering to the target reservoir’s water levels. The proposed approach uses a multiobjective optimization model that prescribes a day-ahead optimal hourly operation for a hydropower facility in terms of spilled water, water stored in the reservoir, and water used for power generation, while meeting a daily target to refill the reservoir. The prescribed scheduling is then used as the input into a model that simulates the actual operations of the power system. This study focuses on a hydro-wind-photovoltaic system located in southwestern China, where the peak power generating capacity of the hydropower facility is ten percent larger than the combined installed capacity of the wind and solar power. The results show that by using the proposed model, the hydropower facility effectively smooths the fluctuations in the combined power output caused by variable wind and photovoltaic power and concurrently meets the reservoir replenishing targets under dry, moderate, or wet hydrologic scenarios. Furthermore, the trade-offs between power generation maximization and power fluctuation reduction were found to depend on two conditions: whether the reservoir is full, and whether the turbine is generating electricity at its maximum capacity. The hydro-wind-photovoltaic integration is more cost-effective when the reservoir is not full and the turbines are not generating electricity at their maximum capacity. When the reservoir is full, hydropower still has the ability to balance the wind and photovoltaic power without curtailment but tends to result in water spillage (22–402 m3/s) and reductions in electricity generation (0.1–11.4 GWh per day). The proposed method for scheduling operations allows hydropower facilities to complement wind and photovoltaic power output, while meeting the target water levels during the refill period.

Design/off-design performance simulation and discussion for the gas turbine combined cycle with inlet air heating

A novel method for the combined cycle retrofitted with compressor inlet air heating (HEAT) process is proposed in this work for part load performance improvement. The performance of the new cycle is researched with two regulations with HEAT and compared with another two strategies with compressor inlet guide vane (IGV). For the novel method, the compressor inlet air is preheated by part of the exhaust flue gas from the heat recovery steam generator. Moreover, comparation result indicates that the novel strategy with HEAT to maintain design turbine inlet temperature (T3) and then to keep turbine exhaust temperature (T4) at its maximum value (HEAT-T3-T4) is suggested for load arrangement. If being compared with the cycle using IGV control to maintain design T3 then keep extreme T4 (IGV-T3-T4), a maximum combined cycle efficiency increment as 1.7% pt. could be obtained by the cycle with HEAT-T3-T4. Both energy analysis and exergy analysis are given in this paper. The simulation results indicate that higher compressor outlet temperature (T2) decreases the extra exergy destruction during combustion, so that the performance of the cycle with HEAT is improved. Meanwhile the specific work of each cycle has also been presented. Furthermore the pressure loss affection of the compressor inlet air heat exchanger on the combined cycle performance is investigated in range of 0%–5%. Each 1% pressure loss is calculated to decrease 1.4% on the design power output, and 0.25% pt. on the combined cycle efficiency, which will weaken the performance improvement. To summarize, this paper proposes a novel method for the combined cycle power output adjustment to obviously improve its part load efficiency. This innovative solution has never been suggested before and it could be combined with other methods for better result.

A Compact Output Power Combiner for Broadband Doherty Power Amplifiers

A novel compact output power combiner for broadband Doherty Power Amplifiers is proposed in this paper. The proposed output power combiner avoids the use of quarter-wave impedance transformers as they are sizable and work over narrow bandwidths. Instead, the proposed combiner utilizes a distributed Brune Section to implement a compact broadband impedance inverter. The final area of the proposed output combiner is λ2/48. When compared to the conventional broadband Doherty structure, which has an approximate area of λ2/16, this structure offers an approximate size reduction of 67%. The proposed combiner is verified by using it in the design of a broadband Doherty power amplifier with an operating bandwidth of 1.7 GHz to 3.4 GHz. The saturated output power varies from 39.2 to 40.4 dBm with a peak power drain efficiency ranging from 58% to 66%. The drain efficiency at 6 dB Output Power Back-Off (OPBO) varies from 37.4% to 45% over an octave.

An X‐band single‐pull class A/B power amplifier in 0.18 μm CMOS

AbstractWe report a compact single‐pull X‐band power amplifier (PA) operating at the class AB utilizing on‐chip transformers in 0.18‐μm 1P6M CMOS technology. Designed X‐band PA includes the interstage matching network and the output power combiner by utilizing on‐chip transformers to achieve small area occupation with improved power added efficiency (PAE). A series RC network is employed between gate and drain of the MOS to provide stable operation with improved bandwidth. The designed PA measures the saturated output power of 18 dBm while the achieved power gain is 19.2 dB at 8 GHz. The output 1‐dB gain compression point (OP1dB) is 14.9 dBm, and the peak PAE is measured to be 22.6% under the supply of 1.8 V. The core chip size is 0.43 mm2 excluding the pads.

Economic Load Dispatch with Valve-point Effect Using Bacterial Foraging Algorithm

Fuel is the most cost component of thermal power generation. The output power of each plant should not exceed the needs of the consumer's load. Unoptimal generation between generating units can cause power losses along the transmission line so that the fuel drain is large enough. The purpose of this study was to determine the optimal power output combination of each generating unit and determine the minimum total fuel cost of the combined power output of the plant by taking into account the valve-point effect and the operational constraint (economic load dispatch). The Newton-Raphson method is used to calculate the transmission line power losses. In this research, Bacterial Foraging Algorithm (BFA) optimization method is proposed to solve the problem of economic load dispatch. This method uses natural selection of optimum global bacterium which has a good food search strategy in the fitness function. The effectiveness of BFAs is tested on IEEE 5 bus 3 generatorsystem and IEEE 30 bus 6 generator system. The results of this proposed method show the optimal value of both generating systems.

Detection and compensation of power imbalance, modulation strength, and bias drift in coherent IQ transmitter through digital filter.

A novel method to simultaneously detect power imbalance, modulation strength, and bias drift of coherent IQ transmitter during the initial power-up is presented. This is achieved by sweeping gain scaling factor of finite impulse filter in a digital domain and monitoring the combined output power. Furthermore, by dithering gain scaling factor of finite impulse filter, the power imbalance is measured with live traffic. Those impairments can be compensated accordingly. For example, the power imbalance is compensated through adjustment of gain setting of a radio frequency amplifier. This novel method works for multiple channels over C band, and the built-in photodiode of coherent transmitter provides sufficient accuracy.

Wind tunnel study on power output and yaw moments for two yaw-controlled model wind turbines

Abstract. In this experimental wind tunnel study the effects of intentional yaw misalignment on the power production and loads of a downstream turbine are investigated for full and partial wake overlap. Power, thrust force and yaw moment are measured on both the upstream and downstream turbine. The influence of inflow turbulence level and streamwise turbine separation distance are analyzed for full wake overlap. For partial wake overlap the concept of downstream turbine yawing for yaw moment mitigation is examined for different lateral offset positions. Results indicate that upstream turbine yaw misalignment is able to increase the combined power production of the two turbines for both partial and full wake overlap. For aligned turbine setups the combined power is increased between 3.5 % and 11 % depending on the inflow turbulence level and turbine separation distance. The increase in combined power is at the expense of increased yaw moments on both the upstream and downstream turbine. For partial wake overlap, yaw moments on the downstream turbine can be mitigated through upstream turbine yawing. Simultaneously, the combined power output of the turbine array is increased. A final test case demonstrates benefits for power and loads through downstream turbine yawing in partial wake overlap. Yaw moments can be decreased and the power increased by intentionally yawing the downstream turbine in the opposite direction.

Passively Q switched dual channel Tm:YLF laser by intracavity spectral beam combination with volume Bragg gratings.

A novel dual channel Tm:YLF laser system was developed where two degenerate laser cavities were coupled by spectrally beam combining their emission and by implementing a common output coupler. Under continuous wave running conditions, each channel's slope efficiency was greater than 45% and the maximum combined output power was 11 W. Passive Q-switching was achieved using an 80%, Cr:ZnSe saturable absorber. The output pulses had a maximum energy of 5.8 mJ and duration of 90 ns (~65 kW of peak power) at 5.7 W of absorbed pump power. Each channel showed less than 1 nm of spectral width with central wavelengths around 1880 nm and 1908 nm correspondingly. The system had adjustable spectral difference between the channels ranging from 5 to 20 nm which corresponds to 0.4 - 1.7 THz if the system is used for nonlinear difference frequency generation.

Incoherent beam combining of fiber lasers by an all-fiber 7 × 1 signal combiner at a power level of 14 kW.

We demonstrate an all-fiber 7 × 1 signal combiner with an output core diameter of 50 μm for high power incoherent beam combining of seven self-made Yb-doped single-mode fiber lasers around a wavelength of 1080 nm and output power of 2 kW. 14.1 kW combined output power is achieved with a total transmission efficiency of higher than 98.5% and a beam quality of M2 = 5.37, which is close to the theoretical results based on finite-difference beam propagation technique. To the best of our knowledge, this is the highest output power ever reported for all-fiber structure beam combining generation, which indicates the feasibility and potential of >10 kW high brightness incoherent beam combining based on an all-fiber signal combiner.