Amorphous silicon (a-Si) have a lower thermal coefficient, but the electrical performance is undermined by the fact of Staebler-Wronski (S-W) effect. Study on the effects of temperature on a-Si cells shows that a-Si cells can obtain higher electrical output at higher operating temperatures. This property makes a-Si cells more suitable for photovoltaic/thermal (PV/T) system where the operating temperature can easily reach higher level. At present, a-Si cells have attracted less attention in the PV/T application, but are promising photovoltaic (PV) materials for PV/T system. Research on the effects of temperature on a solo a-Si cell is already available, but the long-term impact on the a-Si PV/T system is still lacking. In a PV/T system, the operating temperature not only affects the electrical and thermal performance, but also the technical and thermodynamic reliability. To investigate the effect of temperature on the performance of a-Si PV/T system, long-term outdoor experiments of two identical a-Si PV/T systems operating at medium temperature (60°C) and low temperature (30°C) have been conducted from December 2017 to June 2019. At the initial phase of the long-test test, the electrical efficiency of the a-Si PV/T system operating at 30°C is 6.14%, which is much higher than that at 60°C (5.69%). During the long-term operation, both the electrical performances at 30°C and 60°C show an obvious download trend owing to the S-W effect. The initial difference in the electrical efficiency between 30°C and 60°C is 0.47%, while the gap eventually narrows to only 0.13%. In the past year and a half, the two a-Si PV/T systems operated stably without significant degradation in thermal and electrical performance. Through the long-term performance monitoring at different operation temperatures, it is demonstrated that a-Si cells are suitable for the PV/T application.
Accurate capacity estimation is of vital importance for lithium-ion battery management. In this paper, an adaptive battery capacity estimation method based on incremental capacity analysis (ICA) is proposed. First of all, the second-order central least squares method is employed to smooth the charging data and obtain the incremental capacity (IC) curve. Then some battery experiments, including the complete charging and partial charging, are designed and conducted. For the complete charging, the relationship between the features of IC curves and battery capacity fading is investigated. For the limitation of ICA on partial charging, the correction method considering the charging initial SOC and battery aging status is proposed. Finally, the algorithm framework of the adaptive capacity estimation based on ICA is put forward.
This article aims to develop a model predictive power source or mode control governing power management for Toyota Prius 2013 model, a Plugin power-split hybrid electric vehicle (HEV). The integrated powertrain control has been developed considering the engine torque, motor torque, generator torque and power source mode of the vehicle as control variables and wheel torque as system output. The driving pattern used in this work is by combining five popular driving cycles on which the developed model is applied it results into a 7.93 % improvement in fossil fuel economy. In certain situations, this improvement can be very high considering real time driving data, not strictly based on a driving cycle, and a studied case shows an improvement of 38.24%.
Microgrids and peer-to-peer (P2P) energy trading are important technical and market arrangements to deal with the challenges brought by the increasing penetration of distributed energy resources (DERs). In this paper, a P2P energy trading hierarchy was proposed for microgrids in distribution networks. Hierarchical P2P markets were established for facilitating the energy trading between prosumers and consumers. A two-stage matching method, including bilateral and pool-based matching, was proposed to match the generation and demand in the hierarchical P2P markets. An extended Mid-Market Rate (MMR) pricing method was further proposed for clearing the hierarchical P2P markets. The proposed hierarchy and matching and pricing methods were tested on a distribution network adapted from a practical network in Neath Port Talbot, Wales, UK. Simulation results demonstrate the operation of the proposed hierarchy, and indicate that the proposed hierarchy, with the proposed matching and pricing method, has the potential to bring greater social welfare compared to the conventional market paradigm.
In this work a hardware-in-the-loop simulator of a novel micro combined heat and power system is discussed and its potential presented. The plant under investigation consists of a concentrated Linear Fresnel Reflectors solar field, a 2kWe/18kWt Organic Rankine Cycle unit and an advanced latent heat thermal energy storage tank equipped with reversible heat pipes.
Because of the complexity of the integrated system, various control strategies are requested for its optimized operation. However, the evaluation of the different control logics and optimizations in real-time can be complex due to technical and reliability issues. Hence, a hardware-in-the-loop simulation framework based on Matlab/Simulink has been developed and validated to assess the dynamics operation of the different subsystems with varying control strategies and set-points. As an example of the validation procedure, the use of the simulator is illustrated by means of the switch among the different operation modes of the plant with varying ambient conditions. The scientific approach proposed can be extended to any function block of the developed controller.
Handling the variability of renewable energies is a key for power systems towards de-carbonization and sustainability, and hybrid power system (HPS) is a promising solution for enhancing power generation by aggregating various energy resources. Meanwhile, the development, implementation and influence of variable speed pumped storage technology has been increasing all over the world. In this paper, a preliminary study on dynamic performance of variable speed unit (VSU) for hybrid photovoltaic-pumped storage power system is conducted. The main method here is numerical simulation based on timescale of seconds, by adopting MATLAB/Simulink. First, a mathematical model of the HPS is established, and a VSPSP and a photovoltaic power system are included. Then, the dynamic performance of the VSU in the HPS is simulated and discussed based on a quantitative comparison between the VSPSP and the FSPSP. The focus is to assess the two aspects: combined power output of the HPS and actuator movement. The results demonstrate the capability and advantage of applying the VSPSP for balancing photovoltaic power variation. Meanwhile, there is no fundamental distinction between the VSU and the fixed-speed unit (FSU) for the regulation movements that indicates wear and tear, despite the physical process and mechanism of active power regulation are different for the two types of pumped storage unit. The model and results could provide understandings on the detailed dynamic behaviors of HPS with VSPSP and photovoltaic power systems, for further supporting the operation and performance evaluation of HPS with multiple renewable energies.
Zero emissions of waste gas and water from coal-fired power plants are one of the pathways for cleaner electricity production in China. It is expected to achieve low-cost zero discharge of flue gas desulfurization (FGD) wastewater by applying multi-effect distillation (MED) or multi-stage flash (MSF) technologies and matching different heat sources from the power plant. In the present work, four different integration schemes were proposed for FGD wastewater recovery by concentration and deep desalination. The thermo-economics of different schemes were analyzed in terms of gained output ratio (GOR) and energy cost. The results showed that the cost of auxiliary steam driven MED could be lowered by the integration of thermal vapor compression (TVC). The GOR of MED could be increased by 10%-100% while the energy cost was reduced by approximately 10%-50%. In contrast, the pump electricity consumption should be reduced when MED was driven by flue gas. Moreover, the MSF distillation had stronger adaptability to salt concentration than MED. The energy cost of flue gas driven MSF could be remarkably reduced by lowering the flash temperature difference.
The low-melting alloys composed of Sn, Bi, Pb, Cd, In, Ga and Sb show good application prospect in phase change heat sink and heat storage system. Thereby, a well understanding of the melting behaviors of low melting-alloys is crucial to design efficient thermal heat storage appliances or heat sinks. In this paper, a one-dimensional enthalpy-based model is established to explore the melting process of an alloy bar. As the results, the effect of mushy zone temperature range which can be reflected by phase change temperature interval and average phase change temperature is discussed on the motion of mushy zone. The results indicates that the increase of surface temperature is significantly delayed by the release of latent heat. Moreover, the duration of mushy zone gradually increases along the vertical direction, which attributes to the increase of thermal resistance. Reducing the average temperature of mushy zone instead of increasing the temperature interval is an effective way to improve the thermal performance of alloy. Specifically, the effective protection time increases 22% with the average temperature decreases from 70 to 50 oC. The calculated results provide theoretical guidance for selecting the working medium of the thermal heat storage appliances or heat sinks.
This paper proposed a new configuration of heat recovery cycle integrating PTES with ORC. A thermodynamic model was built to study the charging process of PTES. A parametric analysis has been conducted to evaluate the performance of the charging process. This paper defined the efficiency of the charging process of PTES with/without ORC. The isentropic efficiency of compressor/expander, the pressure ratio, and the designed temperature have been chosen to analyze the performance of the charging process. The proposed solution can be potentially used to improve the round-trip efficiency of PTES.
Winter heating, as a basic need of the public, takes great effects on living habits and living level. In Gannan Tibetan Autonomous Prefecture, winter is cold and winter heating lasts for 7 months. Passive solar building technology has been advocated and spread for energy-saving and living standard improving since 1970s. At present, coal and dry cow manure are usually burned in stove for heating and indoor comfort is still unknown for the passive solar building. Considering clean heating with solar energy, an active solar heating system was developed in a passive solar building with low temperature floor irradiator and water heating Kang and indoor comfort of a passive solar building with active solar heating was compared to that with stove heating by on-site experiments and PMV-PPD method. The experimental results show that, in a whole heating season, the indoor temperature of five sevenths days meet the Standard of GB50785-2012 and humidity always meets the Standard and the concentrations of CO, SO2, NO2, PM10, PM2.5 and CO2 are always below the Standard Values in GBT18883-2002 in the passive solar building with active solar heating, while in the passive solar building with stove heating, the indoor temperature usually does not meet the Standard and the concentrations of CO, SO2, NO2, CO2, PM2.5 and PM10 are always higher than that of the passive solar building with active solar heating and the concentrations of PM2.5 and PM10 are always higher than the Standard Values in GBT18883-2002. According to the evaluation of PMV-PPD index and IAQ index, active solar heating show more favorable performances than stove heating in a passive solar building. Hence, in cold Tibetan areas, it is promising for active solar heating to take the place of stove heating in aspects of energy-saving and indoor air quality improving.