Abstract

With the development of sustainable concepts and zero-energy buildings, improving the energy efficiency of the overall operation phase of the building has an increasing impact on reducing energy consumption. Currently, most studies lack the analysis of key influencing factors of building energy efficiency evaluation, and thus cannot provide specific suggestions for the building energy efficiency. This paper aims to comprehensively evaluate the energy efficiency of the operation stage, which accounts for the largest proportion of the whole building life cycle, and conduct a sensitivity analysis on various subsystems and equipment of building energy systems to find the key factors and hurdles that affect the improvement of the energy efficiency. This work will provide specific suggestions for the energy performance diagnosis and renovation of existing buildings in China, and is of great significance to comprehensively evaluating high-consumption building equipment and improving the overall building quality.

Abstract

With the development of power density in motor, the cooling becomes more and more important. Heat pipe is a method to solve this issue. However, the performance of heat pipe is largely affected by the structure, the operating angle, and the cooling at condensation section. Therefore, this paper experimentally discusses its impact on heat pipe performance. Based on the experimental data, (artificial neural network) ANN model is established to predict the performance. Results showed that, when the operating angle of heat pipe was large than 45°, it can be well adopted for motor cooling; while for other operating angles, the performance would be largely changed. ANN model is suitable method for the prediction the performance of heat pipe. The average relative errors of evaporator temperature, heat load, and effective thermal conductivity 1.0%, 1.7% and 2.9%, respectively.

Abstract

This paper evaluates the feasibility of CO2 storage in depleted hydrocarbon reservoirs using 3-D seismic and well data with particular reference to the Niger Delta. CO2 sequestration is a fundamental measure for decreasing greenhouse gas emissions. Based on the papers reviewed, the presence of reservoir-seal pairs, traps, faults, lateral continuity of reservoir, appropriate reservoir depth, developed hydrocarbon fields, and availability of massive hydrocarbon fields indicates a high potential for CO2 sequestration in the Niger Delta. The paper concludes that the estimations of the injection rate and injection pressure are essential considerations for CO2 sequestration and highlights the challenges and opportunities of future research.

Abstract

With the development of data centers (DCs), traditional air cooling system was hard to meet cooling requirement. Single-phase immersion cooling system received more attention because of high performance and low energy consumption. However, the research for such technology is not enough. In this paper, the preferred heat sink is discussed, as well the coolant. Based on this, the heat sink is optimized according to different coolant. Results showed that, the performance of pin fin heat sink was better than that of micro-channel heat sink. Different coolants had different optimal fin spacing. The optimal fin spacing of FC3283 was 3 mm; for mineral oil and EC110, it was 5 mm. EC110 has the best performance in four coolants due to high thermal conductivity and low viscosity and density. The energy consumption can be reduced up to 0.22 W, compared to use mineral oil with 1 mm fin spacing.

Abstract

Open refrigerated display cabinet (ORDC) is widely used in supermarket. It is very convenient for customer to take package. Therefore, the package is not full in ORDC in most time. And the different package arrangement could directly affect ORDC performance. Therefore, this paper optimizes the ORDC and aims to find an optimal structure to meet all different package arrangements. By using the validated model, the windshield and airfoil were employed. Results showed the optimal windshield width, the distance of from evaporator to windshield, and the distance from airfoil structure to shelf edge were 70 mm, 210 mm, and 80 mm, respectively. Under different package arrangements, the average temperature only varied 0.8 °C and the energy consumption 9%. The results obtained in this paper could provide guidance to optimize ORDC.

Abstract

As an important component for tackling temporal variability of renewable energy sources, a BESS (Battery Energy Storage System) periodically produces control packets to realize conversion between DC battery energy and AC energy. The present paper proposes attacks to a BESS-integrated smart grid by selectively dropping the control packets according to the unique dynamics of DC-AC energy conversion process in a BESS. As the present attacks are able to distort the grid voltage and frequency far beyond the limits specified in IEEE standards 519, hence may have detrimental effects on electrical equipment in single-phase/three-phase smart grids. The analysis and simulation results show that the attacks are viable. Finally, the paper proposes countermeasures on the present attacks by protecting channel’s time-stamp and control signals.

Abstract

In order to further reduce the energy consumption of heat pump system in winter, a new type of photovoltaic driven storage constant temperature storage system is proposed in this paper. The results show that the temperature in the storage room can be stably maintained at -2.0 °C to 3.7 °C. The operating efficiency of the heat pump system can be maintained between 3.0 and 4.0, the average coefficient of performance (COP) of the system can reach 1.9, and the operating power of the system is 0 kW to 0.7 kW. The cumulative heat produced by the system reached 18.0 kW·h, and the average daily accumulative consumption of electricity was only 6.8 kW·h. The system can provide a design basis for energy-saving constant temperature storage.

Abstract

Aquaculture industry continues to grow globally as an increasing need for global food access and security. The corresponding operations for aquaculture are moving to farther offshore areas, pursuing greater productivity. Several new offshore aquaculture systems incorporating with ocean renewable energy sources, have emerged in recent years. However, the environmental and economic effects of these offshore aquaculture systems have not been systematically performed up to now. In this study, a wave powered offshore aquaculture platform, Penghu, was taken as a case study to evaluate the environmental and economic performance using life cycle assessment (LCA) and life cycle cost assessment (LCCA). Additionally, the energy performance of power system on the platform was also discussed. Results showed that the carbon footprint of the aquaculture platform was 2,307 t CO2-eq. The production operations on the platform achieved zero-carbon emissions, due to all production facilities were entirely powered by renewable energy. Additionally, the energy payback time of the power system was about 0.8 years. The energy payback ratio is 25.23. The LCCA analysis indicated that the profits from this new offshore aquaculture platform is substantial, although the total cost is much higher than that of the conventional system.

Abstract

Power system decarbonization is no longer debatable for achieving carbon neutrality in China. Guangdong-Hongkong-Macau (GHM) region faces significant challenges towards carbon neutrality due to its fossil-dominated energy structure. Here, we develop a new assessment model for determining optimal transition pathways for GHM power system under various decarbonization scenarios. We found that total system costs for CDR70, CDR85, and CDR100 scenarios are 619, 628, 653 billion USD. Moreover, offshore-wind, nuclear, and electricity import are of great importance for GHM low-carbon transition. Our proposed method is applicable to both regional and national energy system decarbonization.

Abstract

With over 50% of the world’s population dwelling in urban areas, responsible for 75% of global energy consumption and 70% of greenhouse gas emissions, there is a need to ensure that urban energy systems are sustainable. One way to achieve this is to develop efficient energy systems that utilize captured and stored CO2 as the working fluid. Also, the awareness of climate change and the environmental impact of human activities has necessitated research into using natural refrigerants and environmentally friendly nanoparticles in the heating, ventilation, and air conditioning (HVAC), process, chemical, nuclear, and energy sectors. Metallic and non-metallic nanoparticles have been studied extensively in the past few decades. Though they have improved the rate of heat energy transfer, the environmental impact assessment is questionable. The environmental impact of the common nanofluids necessitates the investigation of renewable bio-nanoparticles such as mango bark. The present study investigates the thermal and hydraulic characteristics of CO2-mango bark nanofluids for application in gas cooling. The Reynolds number of the nanofluid is varied between 100 and 1000; nanoparticle volume concentration is between 0.5 and 2.0%, and the inclination angle is -90o to +90o. The heat transfer coefficient and pressure difference show a significant relationship with the inclination angle, Reynolds number and nanoparticle volume concentration. However, the heat transfer enhancement due to the nanofluid is about 10%, and the inclination angle is up to 40%. The inclination angle of ±30o, ±45o, and ±60o consistently possess higher thermal and hydraulic characteristics.