In this work, the dynamic modelling of a system based on reversible solid oxide cell (rSOC) is developed so that it can be integrated with the grid for power balancing. The focus is on the compatibility with profiles of wind electricity production. In addition, the effect and challenges of such a dynamic operation on the system and stack itself are studied. Detailed operation strategies are defined during the switching process from one operational mode to another and are implemented on the dynamic process model. Simulation results show that when the rSOC system is operated in solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) modes alternatively, energy balancing can be continuously implemented. In this process the results show that rSOC system operates in the safe operating range and does not deviate from the system limits. This is due to the accurate strategies developed for the switching process. It is also observed from simulation results that the switching time significantly is influenced by the initial power of one operational mode and the final power of another operational mode.
With high oxygen content and cetane number, polyoxymethylene dimethyl ether 3 (PODE3) is favorable as a fuel to be used in internal combustion engines. In this study, PODE3/diesel/gasoline blends in a homogeneous charge compression ignition engine are numerically studied for the first time. The effects of fuel blend ratio as well as equivalence ratio (ER) are investigated. It is noticed that high temperature heat release depends largely on blend ratio. Furthermore, indicated thermal efficiency is observed to be better with higher ER and is generally higher with increased PODE3. As for emissions, higher ERs show trends of less CO and more NOx. Moreover, similar trends are seen when diesel addition to PODE3 is made comparison with gasoline addition to PODE3, potentially putting CO and NOx in a trade-off relationship.
A skeletal mechanism with 133 species and 877 reactions for MOD9D (one of the main unsaturated methyl esters in biodiesel fuels) is constructed by using decoupling methodology. The obtained skeletal mechanism consists of four parts: high temperature decomposition, low temperature oxidation, ester group reactions and detailed chemistry of small species. Extensive validations are firstly performed against available experimental data in shock-tube for autoignition delay. The predicted results by the skeletal mechanism matches well with the experiment results. The comparison has been conducted between the detailed mechanism and a semi-detailed mechanism. Good agreement or even better predictions at some initial conditions has been observed. Further validations are conducted against the experimental data of fuel species’ conversion rate and species concentration in PSR at varying initial temperatures. The results indicate that the developed skeletal mechanism is capable of predicting the combustion characteristics of MOD9D.
Vehicle to grid (V2G) is a technology which is receiving much attention as a method for achieving an efficient energy management system by connecting electric vehicles (EVs) to an electric power grid. In recent years, the amount of EV and renewable energy, such as photovoltaic (PV), increases rapidly. To make full use of energy, the relationship between self-consumption rate (SCR) of PV and EV penetration rate (EVPR) is a valuable issue. In addition, the stability of micro grid (MG) with different EVPR is also considered. This paper aims to find how the EVPR influence the stability of MG and SCR of PV. To achieve the main objective of this paper, a typical PV installed capacity is adopted and several scenarios with different EVPR are compared in MATLAB programming environment. The result shows that under a stable MG environment, with the growth of EVPR, remarkable increase occurs in both the stability of MG and SCR of PV. But there is an ultimate capacity for EV. Under ultimate capacity, stable load curve and fewer dump energy can be achieved simultaneously.
The objective of this work is to analyze two different solutions to the energy demand of the Tucuruí Locks. A photovoltaic power station is compared to a hybrid power generation system composed by photovoltaic and small hydraulic turbine, with pumped storage. The alternatives are discussed technically and economically: the annual energy costs of the scenarios are calculated based on the evolution of the expenses and the related energy payback time are found. The water resource is exploited responsibly, keeping balanced the volume of water in pumping and generating mode. The grid works as an intermediate storage and allows the operations with a single Pump As Turbine (PAT). The installation site is adjacent to the boat-lift structure of the Tucuruí dam. Its specific location lowers down the initial investment in favor of the hybrid system as the more viable alternative to the considered conditions.
Membrane distillation (MD) utilizes low-grade thermal energy and alternative energy to drive vapor transport through hydrophobic membrane pores for the application of water desalination, aroma compounds recovery, waste water treatment and concentration of thermo-sensitive solutions. In this work, to overcome commonly observed trade-off problems between thermal efficiency, water flux and water productivity, the simulation and optimization of a series of key objective parameters of MD were conducted by proposing a novel modeling approach. The heat and mass transfer across membrane is synchronously enhanced on account of the interaction effects of operational and module configuration variables to achieve a global optimization of MD.
PMSM is a heated research field in terms of the HEVs. In order to increase the efficiency and output characteristics of the PMSM, the design and modeling method which can design the PMSM according to its performance requirements is necessary. In this paper, a new modeling method for multi-field coupling dynamic analysis for PMSMs based on forward design theory is proposed and verified. In particular, given some performance parameters, stator and rotor structural parameters can be decided by electromagnetic load prefetching algorithm and maximum torque method. Besides, the mathematical model of the PMSM power losses achieves an evaluation of the motor output performance effectively. Simulation results compared with the PMSM experimental data show the proposed approach is valid.
The deep borehole heat exchanges (DBHEs) use a coaxial tube to obtain deep geothermal energy, avoiding the problem of groundwater corrosion and recharge, which have great application value. In this paper, a heat transfer model of a DBHE with a depth of 2000m and an outer diameter of 177.8mm is established by Fluent. The effects of various inlet temperature (5~20℃), inlet velocity (0.5~1m/s), thermal conductivity of rock (2.5~3.5W/(m·℃)) and geothermal gradient (0.035~0.045℃/m) on the heat transfer performance in a heating season are studied. The results show that the heat transfer performance of DBHEs decays with time. The rock temperature field is basically invariant outside the radius of 15m. Decreasing the inlet temperature, increasing the inlet velocity, increasing the thermal conductivity of the rock, and increasing the geothermal gradient can increase the heat extraction rate of DBHEs. Under the condition of constant geometric parameters, for every increase of 0.005℃/m in geothermal gradient, the heat extraction rate of the DBHE studied increases by an average of 22.76kW, and for every increase of 0.5W/(m·℃) in the thermal conductivity of the rock, it increases by an average of 26.44kW.
The safety issues of lithium-ion batteries, i.e. thermal runaway, have attracted abroad attention and become more critical with the increase of battery energy density. In this study, the thermal runaway behaviors of high-energy-density lithium-ion batteries with nickel-rich cathode are investigated considering the effects of cathode morphology and state of health. The results show that the safety behaviors of batteries with single crystal cathode is almost same as that with the poly crystal cathode. However, after cycling, the battery with single crystal showed worsen thermal stability after cycling at 45oC, as the onset temperature of thermal runaway decrease, while the battery with poly crystal cathode exhibited opposite changes.
In this paper, liquid-separation is attempted to plate condenser to improve the condensation of plate heat exchangers. Liquid-separation plate condenser (LPC) with two paths, three paths and four paths are proposed. The model exhibits good accuracy in predicting heat transfer coefficients (HTC). LPCs show superior performance to conventional plate condenser (CPC). There exists optimum configuration for each LPC, and they are selected for further study. It is found that the more paths LPC has, the higher HTC and heat load (Q) it would be. LPC with three paths and path length ratio (PLR) of 4:3:3 is recommended.