Two-Stage Optimal Dispatching of Wind Power-Photovoltaic-Solar Thermal Combined System Considering Economic Optimality and Fairness

Aiming at the problems of large-scale wind and solar grid connection,how to ensure the economy of system operation and how to realize fair scheduling between new energy power stations,a two-stage optimal dispatching model of wind power-photovoltaic-solar thermal combined system considering economic optimality and fairness is proposed.Firstly,the first stage dispatching model takes the overall economy optimization of the system as the goal and the principle of maximizing the consumption of wind and solar output,obtains the optimal output value under the economic conditions of each new energy station,and then obtains the maximum consumption space of the new energy station.Secondly,based on the optimization results of the first stage,the second stage dispatching model uses the dispatching method of fuzzy comprehensive ranking priority to prioritize the new energy stations,and then makes a fair allocation to the dispatching of the wind and solar stations.Finally,the analysis of a specific example shows that themodel can take into account the fairness of active power distribution of new energy stations on the basis of ensuring the economy of system operation,make full use of the consumption space,and realize the medium and long-term fairness distribution of dispatching plan.

Optimal Scheduling Method of Cogeneration System with Heat Storage Device Based on Memetic Algorithm

Electric-heat coupling characteristics of a cogeneration system and the operating mode of fixing electricity with heat are the main reasons for wind abandonment during the heating season in the Three North area.To improve the wind-power absorption capacity and operating economy of the system,the structure of the system is improved by adding a heat storage device and an electric boiler.First,aiming at the minimum operating cost of the system,the optimal scheduling model of the cogeneration system,including a heat storage device and electric boiler,is constructed.Second,according to the characteristics of the problem,a cultural gene algorithm program is compiled to simulate the calculation example.Finally,through the system improvement,the comparison between the conditions before and after and the simulation solutions of similar algorithms prove the effectiveness of the proposed scheme.The simulation results show that adding the heat storage device and electric boiler to the scheduling optimization process not only improves the wind power consumption capacity of the cogeneration system but also reduces the operating cost of the system by significantly reducing the coal consumption of the unit and improving the economy of the system operation.The cultural gene algorithm framework has both the global evolution process of the population and the local search for the characteristics of the problem,which has a better optimization effect on the solution.

New generation traction power supply system and its key technologies for electrified railways

Unlike the traditional traction power supply system which enables the electrified railway traction sub- station to be connected to power grid in a way of phase rotation, a new generation traction power supply system without phase splits is proposed in this paper. Three key techniques used in this system have been discussed. First, a combined co-phase traction power supply system is applied at traction substations for compensating negative sequence current and eliminating phase splits at exits of substations; design method and procedure for this system are presented. Second, a new bilateral traction power supply technology is proposed to eliminate the phase split at section post and reduce the influence of equalizing current on the power grid. Meanwhile, power factor should be adjusted to ensure a proper voltage level of the traction network. Third, a seg- mental power supply technology of traction network is used to divide the power supply arms into several segments, and the synchronous measurement and control technology is applied to diagnose faults and their locations quickly and accurately. Thus, the fault impact can be limited to a min- imum degree. In addition, the economy and reliability of the new generation traction power supply system are analyzed.

Numerical Calculation of a 3000MWt MHD-steam Combined Cycel System with Tail Gasification

A numerical calculation of a 3000MWt MHD steam combined cycle system with tail gasification is described . The research scheme has been set up and the parameters of this system have been designed. Then the efficiency of the combined cycle system has been calculated which is up to 53.9%.

Diesel generator exhaust heat recovery fully-coupled with intake air heating for off-grid mining operations:An experimental,numerical,and analytical evaluation

The customarily discarded exhaust from the fossil fuel-based power plants of the off-grid mines holds the thermal potential to fulfill the heating requirement of the underground operation.This present research fills in an important research gap by investigating the coupling effect between a diesel exhaust heat recovery and an intake air heating system employed in a remote mine.An integrative approach comprising analytical,numerical,and experimental assessment has been adapted.The novel analytical model developed here establishes the reliability of the proposed mine heating system by providing comparative analysis between a coupled and a decoupled system.The effect of working fluid variation has been examined by the numerical analysis and the possible improvement has been identified.Experimental investigations present a demonstration of the successful lab-scale implementation of the concept and validate the numerical and analytical models developed.Successful deployment of the fully coupled mine heating system proposed here will assist the mining industry on its journey towards energy-efficient,and sustainable mining practices through nearly 70%reduction in fossil fuel consumption for heating intentions.

A New Cleaner Power Generation System Based on Self-Sustaining Supercritical Water Gasification of Coal

A new cleaner power generation system(IPGS) is proposed and investigated in this paper. Integrating combined cycle with supercritical water gasification of coal, the thermodynamic energy of the produced syngas is cascade utilized according to its temperature and pressure, both sensible and latent heat of the syngas can be recycled into the system, and thereby the net power efficiency can be about 6.4 percentage points higher than that of the traditional GE gasification based power plant(GEPP). The exergy analysis results show that the exergy efficiency of the proposed system reaches 52.45%, which is 13.94% higher than that of the GEPP, and the improvement in exergy efficiency of the proposed system mainly comes from the exergy destruction decline in the syngas energy recovery process, the condensation process and the syngas purification process. The syngas combustion process is the highest exergy destruction process with a value of 157.84 MW in the proposed system. Further performance improvement of the proposed system lies in the utilization process of syngas. Furthermore, system operation parameters have been examined on the coal mass fraction in the supercritical water gasifier(GF), the gasification temperature, and the gasification pressure. The parametric analysis shows that changes in coal concentration in the GF exert more influence on the exergy efficiency of the system compared with the other two parameters.

CO_(2)Plume Geothermal(CPG)Systems for Combined Heat and Power Production:an Evaluation of Various Plant Configurations

CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration economy.Petrothermal geothermal energy has a tremendous worldwide potential for decarbonising both the power and heating sectors.This paper investigates three potential CPG configurations for combined heating and power generation(CHP).The present work examines scenarios with reservoir depths of 4 km and 5 km,as well as required district heating system(DHS)supply temperatures of 70℃ and 90℃.The results reveal that a two-staged serial CHP concept eventuates in the highest achievable net power output.For a thermosiphon system,the relative net power reduction by the CHP option compared with a sole power generation system is significantly lower than for a pumped system.The net power reduction for pumped systems lies between 62.6%and 22.9%.For a thermosiphon system with a depth of 5 km and a required DHS supply temperature of 70℃,the achievable net power by the most beneficial CHP option is even 9.2%higher than for sole power generation systems.The second law efficiency for the sole power generation concepts are in a range between 33.0%and 43.0%.The second law efficiency can increase up to 63.0%in the case of a CHP application.Thus,the combined heat and power generation can significantly increase the overall second law efficiency of a CPG system.The evaluation of the achievable revenues demonstrates that a CHP application might improve the economic performance of both thermosiphon and pumped CPG systems.However,the minimum heat revenue required for compensating the power reduction increases with higher electricity revenues.In summary,the results of this work provide valuable insights for the potential development of CPG systems for CHP applications and their economic feasibility.

Performance of S-CO_2 Brayton Cycle and Organic Rankine Cycle(ORC) Combined System Considering the Diurnal Distribution of Solar Radiation

This paper researches the performance of a novel supercritical carbon dioxide(S-CO_2) Brayton cycle and organic Rankine cycle(ORC) combined system with a theoretical solar radiation diurnal distribution. The new system supplies all solar energy to a S-CO_2 Brayton cycle heater, where heat releasing from the S-CO_2 cooler is stored in the thermal storage system which is supplied to the ORC. Therefore, solar energy is kept at a high temperature, while at the same time the thermal storage system temperature is low. This paper builds a simple solar radiation diurnal distribution model. The maximum continuous working time, mass of thermal storage material, and parameter variations of the two cycles are simulated with the solar radiation diurnal distribution model. 10 organic fluids and 5 representative thermal storage materials are compared in this paper, with the mass and volume of these materials being shown. The longer the continuous working time is, the lower the system thermal efficiency is. The maximum continuous working time can reach 19.1 hours if the system provides a constant power output. At the same time, the system efficiency can be kept above 38% for most fluids.

Development of a Low Carbon Economy in Wuxi City

The development of a Low Carbon Economy is a vital instrument to encounter climate change and take into account the growing challenges of an increasing urbanization in China. Wuxi City in East China’s Jiangsu Province is starting to implement a Low Carbon City Plan for safeguarding a sustainable development of the city until 2020 and beyond. This paper aims at estimating the impact of the Low Carbon City plan for Wuxi’s energy demand and CO2-emissions until 2050. Using an econometric energy supply and demand model to estimate and forecast the Wuxi energy and CO2-balance aggregates until 2050, it compares a scenario without specific Low Carbon City measures to reduce sectoral CO2-intensities to a Low Carbon scenario implementing these measures according to the Low Carbon City Plan until 2020 and beyond. The decomposition of the Kaya-identity reveals that the increase of per capita income has the largest impact on the growth of CO2-emissions and the decrease of energy intensity of Gross Value Added the largest impact on the reduction of CO2-emissions in Wuxi. A decrease of population and CO2-intensity of Primary energy supply only have average contributions. The decrease of energy intensity of Gross Value Added is due to energy efficiency gains in the single economic sectors, but to a large extent due to structural changes of the economy away from energy intensive sectors such as iron and steel, chemical industry or cement industry towards the energy extensive service sectors. A growing residential sector also reduces the industrial share of energy demand. Only following the assumed national trend with a shift from CO2-intensive industries to a CO2-extensive service economy, the Low Carbon goal of a 50% reduction of CO2-intensity of Gross Value Added compared to 2005 cannot be reached in Wuxi. Specific sectoral CO2 -intensity goals have to be successfully observed by the economic sectors in Wuxi, especially by the industry. The promotion of combined heat and power generation also has to contribute to the specific activities in Wuxi.

Operation Strategy Analysis and Configuration Optimization of Solar CCHP System

This paper proposed a new type of combined cooling heating and power(CCHP)system,including the parabolic trough solar thermal(PTST)power generation and gas turbine power generation.The thermal energy storage subsystem in the PTST unit provides both thermal energy and electrical energy.Based on the life cycle method,the configuration optimization under eight operation strategies is studied with the economy,energy,and environment indicators.The eight operation strategies include FEL,FEL-EC,FEL-TES,FEL-TES&EC,FTL,FTL-EC,FTL-TES,and FTL-TES&EC.The feasibility of each strategy is verified by taking a residential building cluster as an example.The indicators under the optimal configuration of each strategy are compared with that of the separate production(SP)system.The results showed that the PTST-CCHP system improves the environment and energy performance by changing the ratio of thermal energy and electric energy.The environment and energy indicators of FEL-TES&EC are superior to those of FTL-TES&EC in summer,and the results are just the opposite in winter.The initial annual investment of the PTST-CCHP system is higher than that of the SP system,but its economic performance is better than that of the SP system with the increase of life-cycle.

Schedule for Reducing the Use of Peat and the Possibilities of Replacing It with Forest Chips in Energy Production in Finland

Between 2018 and 2020, an average of 15 TWh of energy peat was consumed in Finland. Energy peat is used in 260 boilers in Finland, which produce district heat and heat and steam for industry, as well as electricity as cogeneration (CHP) in connection with district heating and industrial heat production. Peat accounts for 3% - 5% of the energy sources used in Finland, but its importance has been greater in terms of security of supply. With current use in accordance with the 2018-2020 average, the emissions from peat are almost 6 Mt CO2 per year in Finland, which is 15% of emissions from the energy sector. In this study, the technical limitations related to peat burning, economic limitations related to the availability of biomass, and socio-economic limitations related to the regional economy are reviewed. By 2040, the technical minimum use of peat will fall to 2 TWh. The techno-economical potential may be even lower, but due to socio-economic objectives, peat production will not be completely ceased. The reduction in the minimum share assumes that old peat boilers are replaced with new biomass boilers or are alternatively replaced by other forms of heat production. Based on the biomass reserves, the current use of peat can be completely replaced by forest chips, but regional challenges may occur along the coast and in southern Finland. It is unlikely that the current demand for all peat will be fully replaced by biomass when part of CHP production is replaced by heat production alone and combustion with waste heat sources.

Compensating active power imbalances in power system with large-scale wind power penetration

Large-scale wind power penetration can affect the supply continuity in the power system.This is a matter of high priority to investigate,as more regulating reserves and specified control strategies for generation control are required in the future power system with even more high wind power penetration.This paper evaluates the impact of large-scale wind power integration on future power systems.An active power balance control methodology is used for compensating the power imbalances between the demand and the generation in real time,caused by wind power forecast errors.The methodology for the balance power control of future power systems with large-scale wind power integration is described and exemplified considering the generation and power exchange capacities in2020 for Danish power system.

Real-time impact of power balancing on power system operation with large scale integration of wind power

Highly wind power integrated power system requires continuous active power regulation to tackle the power imbalances resulting from the wind power forecast errors. The active power balance is maintained in real-time with the automatic generation control and also from the control room, where regulating power bids are activated manually. In this article, an algorithm is developed to simulate the activation of regulating power bids, as performed in the control room, during power imbalance between generation and load demand. In addition, the active power balance is also controlled through automatic generation control, where coordinated control strategy between combined heat and power plants and wind power plant enhances the secure power system operation. The developed algorithm emulating the control room response,to deal with real-time power imbalance, is applied and investigated on the future Danish power system model. The power system model takes the hour-ahead regulating power plan from power balancing model and the generation and power exchange capacities for the year 2020 into account.The real-time impact of power balancing in a highly wind power integrated power system is assessed and discussed by means of simulations for different possible scenarios.