The energy management strategy (EMS) plays an important role in the power system of hybrid-powered fuel cell vehicles in order to reduce hydrogen consumption and fuel cell performance degradation. This paper proposes a robust EMS based on the min-max game theory, where the EMS and the driver behavior are set as two virtual game players making decisions for opposite goals. First, a mathematical model of the hybrid-powered fuel cell vehicle is introduced, that include a transmission system, an ultracapacitor system, a fuel cell system, and the DC/DC converter. Then, a min- max game framework is constructed to describe the energy management problem of fuel cell/ultracapacitor hybrid-powered vehicle with uncertain environment. Finally, the high efficiency and robustness of the proposed strategy are validated by comparing it to the PID-based strategy in the dynamic driving condition.
This present study uses a panel of 24 countries over the period of 1990-2015 to analyze proposed determinants of energy consumption in Africa. The panel is categorized into LI, LMI and UMI African economies. Applying econometric tests and DCCE estimator through a specified DHPD model, issues of heterogeneity and cross-sectional reliance were considered. Our established findings indicated that, GDP, OP, URB, and POPg are potential drivers of EC when capital stock and labor are used as control variables. Further, with the exception of URB-EC, POPg-EC, POPg-GDP, and POPg-URB nexus whose direction of causality were common across country groups, variations occurred for the causalities amid GDP-EC, OP-EC, OP-GDP and URB-GDP nexus for the different income level groups. We therefore conclude that, factors unique to the various country groups in terms of income levels influence the causal affiliations between analyzed variables. Policy recommendation are briefly discussed.
Application of heat recovery units in building HVAC systems can significantly save the energy consumed by conditioning fresh air. The indirect evaporative cooler (IEC), used as a pre-cooling device for fresh air in the hot-humid area, recovers both latent and sensible energy from the exhaust air. In this paper, a year-around on-site performance test was carried out in a wet market located in Hong Kong. The energy performance of the two A/C systems with exhaust air heat recovery units was analyzed and compared: an IEC coupled to an AHU; a traditional heat recovery wheel (HRW) coupled to an AHU. The heat recovery of IEC and HRW were collected under typical summer operation conditions. The results show that the HRW has better dehumidification performance than IEC, but the IEC can largely reduce the fresh air temperature by handling the sensible cooling load. During the whole year, the difference in the total heat recovery between IEC and HRW is within 2%. In cooling seasons, the energy efficiency of the two systems with IEC and HRW for exhaust air heat recovery can be improved by 27.6% and 25.7% respectively.
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.