natural gas system (IEGS), operating reserve and gas storage are both useful support to cope with contingencies in IEGS. This paper proposes a day-ahead SCUC model for the IEGS to schedule the operating reserve and gas storage simultaneously. The multi-state models for generating units and gas wells are firstly established. Based on the multi-state models, the expected unserved energy cost (EUEC) criterion is proposed based on probabilistic methods considering random failures of generating units and gas wells. Then, the EUEC criterion is incorporated into the day-ahead SCUC model, which is nonconvex and mathematically transformed into a solvable mixed integer linear programming (MILP) problem. The proposed model is studied using a 6-bus-6-node IEGS with natural gas storage.
There are already numerous small-scale solar energy collectors on the roofs of buildings in many cities in China, which are used to provide domestic hot water in most circumstances. However, these separated small-scale solar energy collectors usually do not work sufficiently as expected, particularly for fear of pipe freezing crack in severe cold winter. On the other hand, these distributed small-scale solar energy collectors would have very convenient access to local district heating system. Hence, the buildings can consume the thermal energy from local district heating system and simultaneously produce heat to local district heating system when the solar energy collectors on their roofs are available. Therefore, the buildings can become solar heat prosumers to local district heating system. In this study, a configuration on solar heat prosumers is proposed to integrate with a general district heating system. Then a thermo-hydraulic model is developed to simulate the energy performance of distributed small-scale solar heat prosumers in district heating system. The proposed model is validated in a real life case study in a north Chinses city. The simulation results showed that the solar energy penetration was about 13% of the total heat consumption in heating season of 120 days.
Path anxiety is a major problem for electric vehicles, and charging infrastructure is indispensable to solve this problem. How to guide an electric vehicle to the optimal charging facility is a problem worth studying. This paper proposes a charging user discount rebate and reservation priority strategy for large scale electric vehicles (EV) access. First of all, the response characteristics of EV users to the discounts and reservation strategies of charging stations are analyzed and the user satisfaction decision model including economic satisfaction and reservation satisfaction is established. Secondly, the charging station benefit model with the goal of maximizing the benefits of the charging station is established. Eventually, the effectiveness of the proposed model is verified by a simulation considering two types of charging stations. The simulation is solved by using genetic algorithms (GA) and the simulation results show that the strategy can effectively attract users to charge and improve the interest of the charging station, as well as improve user satisfaction.
In this paper, the peaking capability of the thermal power unit is maximized, and the wind power accommodation as much as possible. A mathematical model of in depth peak load cycling of the thermal power unit under the condition of wind power integration is proposed, and optimal operation of thermal power unit in depth peak load cycling. Based on the actual data of a provincial power grid in China, the economics of the thermal power unit in depth peak load cycling scheme under large-scale wind power integration are analyzed. The research results show that the adoption of thermal power unit in depth peak load cycling scheme can not only stabilize wind power fluctuation, solve the problem of wind power accommodation, but also save the generation cost of thermal power unit, making it feasible to ”depth peak load cycling and wind power accommodation”.
The evaporative cooling technique has gained growing attention for use in air conditioning systems. A hybrid evaporative pre-cooled air-conditioning system has been proposed. An indirect evaporative heat exchanger (IEHX) is adopted as a pre-cooling device before the conventional mechanical vapour compression unit. The present work aims to develop a numerical model for the IEHX to study the pre-cooling performance by using the room exhaust air as the working air. A computational model has been developed to investigate the heat and mass transfer in the indirect evaporative heat exchanger. It can be inferred that the evaporative pre-cooling unit is able to reduce the air temperature and condense water through the IEHX. Consequently, the hybrid evaporative pre-cooled air-conditioning system is able to achieve a potential energy saving due the pre-cooling effect and the improvement of the chiller’s efficiency.
Urban form is a significant factor affecting building energy consumption and district energy efficiency design and its effects are difficult to quantify. This study aims to explore the effects of various urban forms on energy consumption at the community scale.
In this work, different urban forms for non-residential and residential districts were analyzed based on the generic form of buildings in Shanghai in terms of their overall energy consumption. Detailed simulations were carried out to quantitatively evaluate the impact of urban form on heating and cooling energy demand. The effect of morphological parameters including both building typology and urban morphology were examined using a dynamic building energy simulation tool, EnergyPlus.
Energy consumption in cities can be a great environmental burden. Renewable energy and waste-to- energy technologies are promising methods to assist the transition of energy- and carbon-intensive urban environment towards low carbon cities. This study aims to investigate the economic and environmental feasibility of renewable energy and waste-to-energy technologies in cities for low carbon transition. Being a well-known city-state, Singapore is taken as an example for the case study. An optimization-based decision support framework is used to estimate the optimum energy mix that minimizes the greenhouse gas emissions of the urban energy system while meeting the energy demand of Singapore. It is found by incorporating solar PV and waste-to-energy facilities to the current natural gas dominating energy system, a 9-10% of renewable energy penetration is achievable in Singapore.
The current centralised, fossil fuel-reliant energy system is experiencing a gradual transition to a more decentralised system, particularly in cities where decentralised energy resources (DER) largely based on renewable sources can help alleviate chronic environmental problems. This transition gave rise to the concept that the pervasion of sensors, embedded systems and ubiquitous network connectivity in urban energy systems (UES) could enhance the overall quality of life through so-called “smart cities” and “smart grids.” A comprehensive analysis of recent reviews of EU-funded projects has elucidated a range of good practices, regarding stakeholder engagement, citizen participation, funding, technologies and demand-side management. Coupled with suitable modelling frameworks accurate analysis of synergies between generation assets, storage solutions and demand-side management (DSM) interventions is possible. Three dominant conceptual models have been identified: the energy hub, the microgrid and the virtual power plant. The technical characteristics can be transferred to the framework structure to be developed for optimising the energy system of the “Fiera del Levante” exhibition complex in the southern Italian city of Bari, which is characterized by a highly variable energy demand scenario. This paper describes the proposed methodology for this case study, which is strongly linked to the Technology Selection and Operation (TSO) model developed at Imperial College London.
High-temperature energy storage is very important for solar power systems with advanced thermal cycles. Manganese oxides are considerable materials for high temperature thermochemical energy storage (800-1000℃) due to the merits of low-cost and non-toxic. However, pure Mn2O3/Mn3O4 redox couple suffers low re-oxidation rate and poor cycling stability. Fe-doped Mn2O3 is expected to improve the reaction characteristics, by using a sol-gel synthesis method. The reversibility and cyclic stability are significantly enhanced by the adoption of Fe, verified by over 10 TGA experimental cycles. As to crystallographic analysis, tetragonal spinel and phases cubic spinel were detected in the reduced materials. Jacobsite (MnFe2O4) is regarded as the vital for the promotion, while (Mn0.8Fe0.2)2O3 exhibits good adaptability under different oxygen partial pressure. Lab-scaled honeycomb materials were investigated for over 100 reduction-oxidation cycles, with an average reaction ratio of 87.9%, which indicates an excellent cyclic stability of iron doped manganese oxides for solar thermochemical energy storage.
By means of the de Gennes model, the magnetocaloric characteristics of Gd-R (R= Dy, Er) alloys as well as Gd, which are materials for sustainable energy, are investigated and the related theoretical and experimental results are compared. The effects of Rdoped concentrations on the Curie temperature of Gd-R alloys are revealed. Furthermore, the dependencies of temperature of the heat capacities and adiabatic temperature changes of Gd, Gd0.95Dy0.05, and Gd0.95Er0.05 under 0 and 2T applied magnetic fields are analyzed and discussed. The calculated results shows that the Curie temperatures of these materials decrease with increasing R-doped concentration; the effect of magnetization/demagnetization on the adiabatic temperature change of Gd-R alloys is weak, but on the temperature at maximum adiabatic temperature change of Gd-R alloys is relatively evident. The calculation results in the present paper may provide some references for the parametric design of room temperature magnetic refrigerators that are energy conversion devices with environmental protection and energy saving.