This paper conducts a numerical study on the characteristics of mean flow field of a combustor with triple swirlers with focus on the effect of turbulence models on the central recirculation zone (CRZ). By comparing numerical results with high-speed photography experiment, it is found that k-Îµ RNG model can better predict the flow field characteristics than k-Îµ realizable and k- Ï‰ SST model. the CRZ length and expansion angle obtained by k-Îµ RNG model are consistent with experiments, and k-Îµ Realizable model are relatively close to it, while k-Ï‰ SST model is quite different from the two others. The results predicted by k-Ï‰ SST have much higher backflow strength and pressure gradient. The study is of great significance to reasonably choice turbulent mode to predict swirling flow in a combustor.
In this paper, the temperature mathematical model and compressor model are established to study the effect of different charge/discharge rates on air conditioning energy consumption. The results show that as the charge/discharge multiplier increases, the air conditioning starts earlier and runs longer, and the energy consumption of the air conditioning system also increases. This method considers different charge/discharge rates of batteries and combines with the energy consumption analysis of air conditioning systems, which is of great value for improving the safety and efficient utilization of energy storage systems.
We analyze the structure of the wind-solar coupled hydrogen production system and optimized system architecture through performance comparison. To obtain the optimal architecture, we first compare the DC bus and AC bus systems to acquire an initial optimized system architecture, and secondly, we analyze the centralized and distributed structure of the system and compared them in five aspects: cost, reliability, system efficiency, stability, and control complexity. Finally, we verified the feasibility of the architecture by analyzing and calculating the performance of the system.
China has a vast territory and abundant offshore wind resources, which provides an environmental basis for the development of offshore floating wind turbine. The typical characteristics of the development of floating wind turbine are far-reaching sea and large-scale structure. The traditional controller cannot deal with the complex marine working conditions and the complexity of the wind turbine structure. For the floating wind turbine, the main control objectives are to stabilize the power output, reduce the load and stabilize the movement of the platform in six degrees of freedom. Therefore, this paper proposes a pitch controller based on the fast integral-type terminal sliding mode (FITS) method, and selects the 5 MW barge floating wind turbine of National Renewable Energy Laboratory (NREL) as the research object. Combined with OpenFAST /Matlab software, the simulation experiments are compared with the traditional baseline gain scheduling PI controller(GSPI) from three aspects: power stability, load shedding and platform motion performance. The simulation results show the effectiveness of the proposed scheme.
Due to the common intermittent characteristics of wind power generation and photovoltaic power generation and the complementary characteristics of power generation periods, the rational design of the operation energy scheduling strategy of the renewable energy hydrogen production system equipped with energy storage batteries is necessary and economical. In this paper, firstly, the off-grid DC bus architecture is optimally selected based on the study of the wind-solar storage coupled hydrogen production system, and the system model is established in Matlab/simulink environment. Secondly, considering the constraints such as equipment power leveling and service life, combined with the study of system optimization scheduling strategy, an economic optimization scheduling model is established with the goal of maximizing system revenue. Finally, we set up different working conditions for simulation analysis to verify the effectiveness and feasibility of the Simulink model and the economic optimization scheduling strategy of the wind-solar storage coupled off-grid hydrogen production system. This paper aims to provide ideas and methods for energy transition and renewable energy hydrogen production system to reduce costs and increase efficiency.
We assess alternative energy technologies for German single-family houses (i.e., hybrid gas heating with solar thermal energy, electric heat pumps, PV and BES systems) in terms of profitability and CO2 emissions. Under the status-quo regulatory framework, the energy transition in the heating sector is fostered through grants for replacing old heating systems, whereas PV generation is fostered by feed-in tariffs and indirect subsidies for self-consumption. We consider alternative regulatory scenarios with a more market-oriented approach, finding that a CO2-oriented reform of energy surcharges and taxes, as well as a reform of network charges, can support a more cost-efficient energy transition in the residential sector.
Energy transition as a response to climate change requires structural transformation in the industrial sector. While some industries have already gained the attention of research studies due to their high production and emissions levels, there is an obvious lack of analyses on small but energy intensive sectors such as casting industry. Herein, the aim of this paper is to fill this knowledge gap by implementing an environmental assessment of the cast iron and steel melting technologies. The carbon footprint of four main types of furnaces and their variants have been determined. Moreover, sensitivity analyses have been conducted to quantify the impact of energy sources and electricity-mix. The analyses show the major differences between the environmental performances of melting technologies. As the GHG emissions depend on the adopted technology linked with specific amounts and sources of energy, the current technologies are associated with high carbon footprints (especially cupola furnaces). Therefore, reaching carbon neutrality necessitates fundamental changes in terms of types of furnaces and related energy sources.
Energy system optimization models are widely used worldwide to assess the effectiveness of decarbonization strategies. The correct accounting of greenhouse gas emissions, mainly CO2, is crucial in this field. Sectorial emissions are typically computed using commodityï¿¾specific factors based on a given (static) fuel composition. For fuels generated by combining fossil and low-carbon commodities, however, the share of the lowï¿¾carbon component can change throughout the model time horizon. As an alternative to static accounting, this work proposes a dynamic accounting method for the emissions avoided thanks to the contribution of hydrogen, biofuels and synfuels. The static accounting method provides an overestimation of the emission levels compared to the proposed accounting method results, which then helps boost new low-carbon technologies in the future energy mix.
Densities of two binary (Helium + Neon) mixtures were measured along six isotherms in the temperature range from (100 to 233.15) K and at pressures of up to 10 MPa, using a low-temperature single-sinker magnetic suspension densimeter. The mixtures were prepared gravimetrically yielding molar Helium fractions of approximately 0.50 and 0.25, respectively. The measurements were carried out at T = (100, 120, 140, 170, 200, and 233.15) K in the homogenous gas region. In total, densities at 72 (T, p) state points were determined. The relative expanded combined uncertainties (k = 2) of the experimental densities were estimated to be within (0.023 and 0.055)%. The largest uncertainty contributions result from the weighing of the sinker and the composition of the prepared mixtures. The experimental results were compared with available experimental literature data as well as with a preliminary mixture model of Lemmon and with a fundamental equation of state of Tkaczuk et al.
In order to stabilize short-term fluctuations in the network frequency, flexibility is offered on balancing electricity markets. With the reformation of the German balancing markets and the opportunity to market secondary balancing energy independently of capacity, short-term flexibilities can now be traded more easily. In this paper, we describe a robust optimization problem for marketing balancing power in these markets. Starting from forecasts on acceptance probabilities and activation durations estimated from historical values, we compute price-quantity pairs that define bids placed on the reserve markets. We present a backtesting study over the period 04/2021 to 11/2021 and, thus, evaluate the potential of flexibility marketing on the secondary control markets.