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With the continuous deepening of China's rural construction and development, people's living conditions are improved day by day, while accompanied by energy and environment crisis issues. This paper mainly analyzes the energy consumption pattern and the indoor environment of rural households in China and discusses the energy-saving optimization strategies for improving the thermal environment of buildings. Questionnaire surveys and field surveys were conducted in three villages in Guanghan, China. The measurement results show that the annual indoor temperature range of the region in the summer is 15–31 °C and the relative humidity range is 34%-96%. The average indoor temperatures in summer and winter are 28 °C and 16 °C respectively. The indoor thermal environment of rural buildings is usually poor and cannot meet the requirements of Chinese standards. At the same time, the architectural design and energy consumption pattern of rural households are different from those in urban areas as countryside has unique characteristics. Finally, we put forward certain energy-saving improvement measures at the end of the article.

Renewable paper reusing plays a significant role in the sustainable environment under the background of the shortage in forest resources and the pollution from the paper industry. The conventional reusing stream of waste office paper appears to have low reusing rates while consuming massive amounts of energy in intermediate steps. In this study, we developed a novel portable renewable desktop paper reusing system based on font area detection and greyscale sensor. The proposed system consists of two main parts, namely, a greyscale sensor and font area detection model and a polishing mechanism. Acting as an ink mark detector for waste desktop paper, the greyscale sensor and font area detection model can detect the font in the waste desktop paper using an adaptive dynamic compensation schematic. The polishing mechanism will grind the font area of the wasted desktop paper, and this paper reusing processing is non-chemical, energy saving and environmentally friendly. The proposed system is demonstrated through simulations and experimental results, which show that the proposed renewable desktop paper reusing system is portable and is effective for reusing waste office paper in the office. An accuracy of 99.78% is demonstrated in the greyscale sensor and font area detection model, and the average reuse rate of one piece of paper is 2.52 times, verifying that the proposed portable system is effective and practical in renewable desktop paper reusing applications.

In this work, a series of nanoencapsulated phase change materials (NanoPCMs) with paraffin wax (PW) as core and melamine-formaldehyde (MF) as shell were synthesized by the in-situ polymerization method. The morphology, chemical structure and thermal properties of prepared NanoPCMs were characterized by scanning electron microscope, Fourier transform infrared, differential scanning calorimetry and thermogravimertic analyzer. The results show that the PW is successfully encapsulated in the MF without chemical interaction, and the NanoPCMs present regular spherical shape with the average diameter of 260–450 nm. The encapsulation efficiency of the NanoPCMs increases with the augment of the supplied amount of core material. The maximum encapsulation efficiency of the NanoPCMs can reach up to approximately 75%. The NanoPCMs can maintain excellent thermal reliability and stability after 2000 thermal cycling. The prepared NanoPCMs can be well applied in the latent heat thermal energy storage and thermal management systems due to their remarkable encapsulation efficiency and thermal properties enable them to.

Harvesting and storing energy is a key problem in some applications. Elastic energy storage technology has the advantages of wide-sources, simple structural principle, renewability, high effectiveness and environmental-friendliness. This paper elaborates the operational principles and technical properties and summarizes the applicability of elastic energy storage technology with spiral springs. Elastic energy storage using spiral spring can realize the balance between energy supply and demand in some applications. Continuous input–spontaneous output working style can provide simple energy sources for short-time energy supply, and provide strong moment impact and rapid start, or realize the energy conservation for reciprocating movement. Uniform output working style can realize energy output with uniform speed for timekeeping and load-driving. Random input working style can harvest and store random mechanical energy or convert small torque into a large moment to drive external loads. Finally, this paper proposes new researches and developments of elastic energy storage technology on new materials and structures, mechanical properties and structural dynamics analyses, design and control for new functions.

The effect of Cu content on the high temperature oxidation properties of the phase change material (PCM) Al-Cu-Si alloys was studied. The oxidation kinetics curves at 600℃ were achieved for Al-Cu-Si alloys with 35–55% Cu, which all follow the cubic law. With an increase in the Cu content from 35 to 55%, the weight gain decreases from 5.75 to 3 × 10−4 g/cm2 after 96 h isothermal oxidation. The oxidation rate also decreases with Cu content, the maximum and minimum rates are 1.52 and 0.32×10−5 g/cm2•h, a nearly 4 times difference. Oxidation does not change the phase composition of Al-Cu-Si alloys, but coarsens the microstructure. The latent heat and the starting temperature of phase change after 96 h oxidation at 600℃ have variations of less than 10% and 6℃, respectively, indicating that the Al-Cu-Si alloys have good thermal stability after high temperature oxidation.

The coupling and complexity of railway train / tunnel system are further aggravated by increasing train speed, which produces a series of aerodynamics problems, such as aerodynamic drag, slipstream, pressure wave and micro pressure wave. Aerodynamic effects of tunnels will result in a significant increase in train energy consumption, shorten life of railway train / tunnel system, and increase maintenance cost. This paper provides a review of aerodynamics of railway train / tunnel system. Challenges in railway train / tunnel system aerodynamics and their related factors are discussed firstly. Aerodynamic performance and flow field characteristics of trains in tunnels are presented. Relationship of aerodynamic effects and parameters of railway train / tunnel system, and the control methods for reducing aerodynamic effects in tunnels are explained. A traffic safety evaluation of the train in tunnels, such as vehicle body structure, passengers’ ear comfort, etc., is introduced and analysed. Finally, future outlooks and research topics are proposed.

Organic Rankine cycle (ORC) has been considered as one of the most promising technologies in industrial waste heat utilization and power generation. During the actual operation of ORC system, due to the fluctuation of cooling and heat sources, the system operates under off-design conditions in most cases. In this paper, thermodynamic model, heat transfer process description and power equipment model are established to evaluate the operating parameters of ORC for the off-design conditions. Evaporation temperature and condensation temperature are taken as independent parameters for the operation of ORC system. Genetic algorithm is adopted to optimize the independent parameters under the maximum net output power. The results show that the effect of optimizing independent parameters is to make the working fluid at the outlet of the preheater as close as possible to a saturated liquid state, and the working fluid at the inlet of the screw expander should be in a saturated gas state. With the optimal power output increasing by 19.1% for every 5 °C increase in hot water inlet temperature, 9.2% for every 20 kg/s increase in hot water mass flow rate, and 3.9% for every 1 °C decrease in cooling water temperature. The optimization method of off-design operating conditions has good system performance and good engineering application prospects.

Renewable energy technologies, particularly in electric vehicles (EVs), have received significant attention in recent years. The wasted energy in a vehicle's shock absorber can be converted into an alternative energy source by regenerative shock absorbers. In this paper, a high-efficiency regenerative shock absorber considering twin ball screws transmissions is proposed for application in range-extended electric vehicles. The proposed regenerative shock absorber can convert vibrational kinetic energy, which is traditionally dissipated as heat in suspension systems, into electricity. The proposed system is divided into four modules: suspension vibration input module, transmission module, generator module and power storage module. Induced by road roughness, the irregular linear oscillations of the suspension are transmitted to the suspension vibration input module. The reciprocating vibrations are converted into unidirectional rotation of the generator by a pair of ball screws, gears, and two overrun clutches in the transmission module. The utilisation of different screw pitches leads to different damping coefficients for upward and downward progress, enabling the shock absorber to fully utilise elastic elements to improve vehicle comfort when compressed and quickly absorb vibrations when stretched. The electricity produced by the generator is stored in supercapacitors to charge the battery and extend the range of EVs. The mechanical properties of the full-scaled fabricated prototype were studied by utilising a mechanical testing and sensing fixture. An average power output of 3.701 W in 1Hz-3 mm sinusoidal vibration input and a peak efficiency of 51.1% and average efficiency of 36.4% were achieved in a bench tests. The range can be approximately extended by 1 mile per 100 miles when EV is driving on the road of class B with a speed of 60 km/h, demonstrating that the proposed high-efficiency regenerative shock absorber is beneficial for harvesting renewable energy, and practical and significant for extending the range of EVs.