Energy Conservation Performance Research Articles

An Active and Passive Controllable Smart Glass Based on an Eco‐Friendly Aqueous Solution

AbstractA smart glass, based on an eco‐friendly aqueous solution, capable of controlling both transparency for privacy and the radiant energy flow for thermal insulation, is demonstrated. The transparency of the glass is self‐adaptive in response to the ambient environment and can also be electrically controlled on demand. The aqueous solution used in this study is composed of water and a non‐ionic surfactant used in the food industry. As the temperature of the aqueous solutions increases above the cloud point, the solution undergoes phase separation into a micelle‐rich phase and a micelle‐poor phase causing the incident light to be scattered by the micellar clusters. Good thermo‐responsive optical properties are achieved with ≈77% luminous transmittance, ≈90% haze, and ≈64% solar regulation. The proposed smart glass fabricated from a biocompatible aqueous solution would be eco‐friendly as well as exhibiting excellent energy conservation performance.

Optimal energy management strategy for dual-power coupling tractor based on the adaptive control technology.

Hybrid tractors (HT) are regarded as the efficient agricultural machine due to their energy conservation performance and faster torque response to deal with load fluctuations. However, the strategy to allocate the battery and fuel energy for demand power should be discussed. In this paper, an on-line management strategy of the HT is proposed to optimize the energy consumption of engine and motor and to reduce torque ripple for power units. A new architecture for replacing power shift and continuously variable transmission technology is proposed. Then, the modified equivalent consumption minimization strategy (ECMS) is used to optimize the torque distribution in which the equivalent factor is further calculated for the real-time process. Besides, the modification of ECMS in variable working conditions can effectively analyse the torque distribution between the motor and engine. The numerical test is implemented that the effectiveness of the proposed energy strategy is validated in plowing conditions. The consequences indicated that the proposed power distribution strategy can adaptively allocate the torque demand according to the fluctuation load. Comparing with the traditional rule-based strategy, the proposed strategy can reduce 6.2% of the energy, and decrease torque ripple with the proposed tractor architecture.

Influence of Rotational Speed on Isothermal Piston Compression System

An isothermal piston is a device that can achieve near-isothermal compression by enhancing the heat transfer area with a porous media. However, flow resistance between the porous media and the liquid is introduced, which cannot be neglected at a high operational speed. Thus, the influence of rotational speed on the isothermal piston compression system is analyzed in this study. A flow resistance mathematical model is established based on the face-centered cubic structure hypothesis. The energy conservation rate and efficiency of the isothermal piston are defined. The effect of rotational speed on resistance is discussed, and a comprehensive energy conservation performance assessment of the isothermal piston is analyzed. The results show that the increasing rate of the resistance work increases significantly proportional to the rotational speed, and the proportion of resistance work in the total work increases gradually and sharply. The total work including compression and resistance cannot be larger than the compression work under adiabatic conditions. The maximum rotational speed is 650 rpm.

Energy conservation performance of a solar thermal and seasonal thermal energy storage-based renewable energy convergence system for glass greenhouses

The utilization of renewable energy sources have gained significant attention in recent years for greenhouse that consumed lots of cooling and heating energy. This study investigated a solar thermal and seasonal thermal-based renewable energy convergence system. This system consists of a solar thermal system, tank- and borehole-type seasonal thermal energy storage, multi-source (i.e., air and water) heat pumps, and ground-source heat pumps. The detailed control logic of the proposed system was implemented, and the system was constructed in a test greenhouse at the Purme Yeoju Farm in South Korea. During the cooling season, the multi-source heat pumps were operated as air-source heat pumps, which showed a coefficient of performance (COP) only 0.5 less than that of the ground source heat pump. The efficiency of the solar thermal system was determined to be 36.6% throughout the investigation period, and the heat storage efficiency of the tank-type seasonal thermal energy storage was 75.7%. Consequently, the proposed system showed a COP of 2.9 during the heating season. The proposed system shows that over 70% of the operating energy can be saved, which is unachievable when using conventional electric heaters.

An efficient hybrid implicit time integration method with high accuracy for linear and nonlinear dynamics

In this work, an effective hybrid implicit method is proposed to analyze linear and nonlinear dynamic problems. The proposed hybrid method is a type of three sub-step method and is unconditionally stable. New method has multiple free parameters which can be employed to control accuracy and numerical dissipation. The new method can obtain controllable numerical dissipation which ranges from the non-dissipative case to the asymptotic annihilating case. Meanwhile, high computation accuracy than classical sub-step methods can be obtained. The new method can obtain the identical effective stiffness matrix for three sub-steps to save computational cost and internal storage for linear cases. Verified by numerical examples, the new method has simple calculation procedure, and is efficient for linear dynamics. Especially for nonlinear dynamics, the new method shows high solution accuracy and excellent energy conservation performance when compared with other methods.

Energy Conservation and Thermal Insulation Performance of Concrete Block Walls Incorporating Expanded Polystyrene Panels: Experimental and Simulation Study

Energy Conservation and Thermal Insulation Performance of Concrete Block Walls Incorporating Expanded Polystyrene Panels: Experimental and Simulation Study

Dynamic coupled heat transfer and energy conservation performance of multilayer glazing window filled with phase change material in summer day

Windows as indispensable for buildings play an important role in decreasing building energy consumption and improving indoor thermal comfort. However, the conventional windows made of the pure glazing units fail to meet the requirements of energy conservation for buildings due to poor thermal insulation. Recent researches found that the application of phase change materials (PCM) can improve the heat transfer performance of glazing unit and the PCM-filled glazing units have advantage in reducing building energy consumption and improving indoor thermal comfort. Therefore, the dynamic coupled heat transfer and energy conservation performance of PCM-filled multilayer glazing unit are investigated numerically in this work. A transient coupled heat transfer model considering conduction, phase change and solar radiation transfer in glazing unit is established, and the energy conservation performance is analyzed based on the heat transfer calculation. Results show that the PCM-filled multilayer glazing unit can significantly reduce energy consumption compared with pure glazing unit, and the energy saving rates are 14.55% for double glazing unit, 33.89% for triple glazing unit and 50.71% for four glazing unit, respectively. In addition, the effects of optical and thermal parameters of PCM on thermal performance of glazing units are investigated thoroughly. It is found that the PCM-filled multilayer glazing unit has advantages in thermal insulation which is good choice for transparent envelope in the building fields.

Energy Conservation Performance of a Solar Thermal and Seasonal Thermal Energy Storage Based Renewable Energy Convergence System for Greenhouses

Energy Conservation Performance of a Solar Thermal and Seasonal Thermal Energy Storage Based Renewable Energy Convergence System for Greenhouses

Optimising and investigating the effect of leaf area index, soil depth, and water content on energy conservation and pollutant reduction in green roof systems (case study: Mashhad City)

In this study, the effect of leaf area index, soil depth, and water content on the energy conservation and carbon emission was evaluated in building industry. For this purpose, firstly Design Builder software was employed to model a green roof on a 160 m2 building located in the cold and dry climate of Mashhad City in Iran. The results showed that energy conservation in the building has a direct relationship with the soil layer thickness (up to 40 cm) and an inverse relationship with the soil water content. A two-fold increase in the LAI improved energy conservation performance of the green roof by 14%. After estimating the effect of green roofs on pollutant emissions, it was found that the highest emission reduction would be related to NOx with the amount of 1,577.1 tons in warm seasons and 2,073 tons in cold seasons.

Earth Sheltered Housing; Design Concepts for Urban Ground-scrapers

The history of human housing portrays Earth sheltered homes as dwellings originally developed for shelter, warmth and security for the earliest human dwellers. These buildings which originated as subterranean dugouts have evolved into modern housing options over the years. Physical attributes of earth sheltered houses signifies a retreat from surrounding elements into secluded spaces bordered by earth-mass as building covering. Further studies reveal its thermal efficiency between seasons and energy conservation properties due to its thermal mass application. A review of typologies identifies various techniques of its design and construction across the globe. This paper looks at the existing construction typologies of earth sheltered housing from the traditional to modern applications. Four unique subterranean applications were studied which represented the major construction typologies. It further investigates the uniqueness in the design concepts of earth sheltered housing as models for future earth-contact housing needs based on the energy conservation and thermal performance of this category of housing. Earth contact characteristics of these types of houses makes for potential energy conservation in single unit earth sheltered homes; however, large scale concepts consequently possess the potentials for optimization of thermal and energy performance. Hence communal type concepts are presented as ideas for urban scale application of Earth sheltered housing.

パッシブタウンにおける集合住宅の省エネルギー性・住環境の研究 （第13報）住宅の昼光照明環境年間評価指標の検討

パッシブタウンにおける集合住宅の省エネルギー性・住環境の研究 （第13報）住宅の昼光照明環境年間評価指標の検討

HVAC Optimal Control with the Multistep-Actor Critic Algorithm in Large Action Spaces

We propose an optimization method, named as the Multistep-Actor Critic (MAC) algorithm, which uses the value-network and the action-network, where the action-network is based on the deep Q-network (DQN). The proposed method is intended to solve the problem of energy conservation optimization of heating, ventilating, and air-conditioning (HVAC) system in a large action space, principally for the cases with high computation and convergence time. The method employs the multistep action-network and search tree to generate the original state and then selects the optimal state based on the value-network for the original and the adjacent states. The results from the application of the MAC algorithm to a simulation problem on the TRNSYS system, where the simulation problem is referring to a real supertall building in Hong Kong, have shown that the proposed MAC algorithm balances control actions between different HVAC subsystems. Further, it substantially saves the computational time while maintaining a good energy conservation performance.

Liquid Thermo-Responsive Smart Window Derived from Hydrogel

Summary Buildings account for 40% of global energy consumption, while windows are the least energy-efficient part of buildings. Conventional smart windows only regulate solar transmission. For the first time, we developed high thermal energy storage thermo-responsive smart window (HTEST smart window) by trapping the hydrogel-derived liquid within glasses. The excellent thermo-responsive optical property (90% of luminous transmittance and 68.1% solar modulation) together with outstanding specific heat capacity of liquid gives the HTEST smart window excellent energy conservation performance. Simulations suggested that HTEST window can cut off 44.6% heating, ventilation, and air-conditioning (HVAC) energy consumption compared with the normal glass in Singapore. In outdoor demonstrations, the HTEST smart window showed promising energy-saving performance in summer daytime. Compared with conventional energy-saving glasses, which need expensive equipment, the thermo-responsive liquid-trapped structure offers a disruptive strategy of easy fabrication, good uniformity, and scalability, together with soundproof functionality that opens an avenue for energy-saving buildings and greenhouses.

Model-free optimal chiller loading method based on Q-learning

Chillers consume considerable energy in building HVAC systems, and the optimal operation of chillers is essential for energy conservation in buildings. This article proposes a model-free optimal chiller loading (OCL) method for optimizing chiller operation. Unlike model-based OCL methods, the proposed method does not require accurate chiller performance models as a priori knowledge. The proposed method is based on the Q-learning method, a classical reinforcement learning method. With the comprehensive coefficient of performance (COP) of chillers as the environmental feedback, the model-free loading controller can learn autonomously and optimize the chiller loading by adjusting the set points of the chilled water outlet temperature. A central chiller plant in an office building located in Shanghai is selected as a case system to investigate the energy conservation performance of the proposed method through simulations. The simulation results suggest that the proposed method can save 4.36% of chiller energy during the first cooling season compared to the baseline control, which is slightly inferior to the value for the model-based loading method (4.95%). Owing to its acceptable energy-saving capability, the proposed method can be applied to central chiller plants that lack a system model and historical data.

Boundary Identification for Traction Energy Conservation Capability of Urban Rail Timetables: A Case Study of the Beijing Batong Line

Energy conservation is attracting more attention to achieve a reduced lifecycle system cost level while enabling environmentally friendly characteristics. Conventional research mainly concentrates on energy-saving speed profiles, where the energy level evaluation of the timetable is usually considered separately. This paper integrates the train driving control optimization and the timetable characteristics by analyzing the achievable tractive energy conservation performance and the corresponding boundaries. A calculation method for energy efficient driving control solution is proposed based on the Bacterial Foraging Optimization (BFO) strategy, which is utilized to carry out batch processing with timetable. A boundary identification solution is proposed to detect the range of energy conservation capability by considering the relationships with average interstation speed and the passenger volume condition. A case study is presented using practical data of Beijing Metro Batong Line and two timetable schemes. The results illustrate that the proposed optimized energy efficient driving control approach is capable of saving tractive energy in comparison with the conventional traction calculation-based train operation solution. With the proposed boundary identification method, the capability space of the energy conservation profiles with respect to the energy reduction and energy saving rate is revealed. Moreover, analyses and discussions on effects from different passenger load conditions are given to both the weekday and weekend timetables. Results of this paper may assist the decision making of rail operators and engineers by enhancing the cost effectiveness and energy efficiency.

Model-free control method based on reinforcement learning for building cooling water systems: Validation by measured data-based simulation

In the domain of optimal control for building HVAC systems, the performance of model-based control has been widely investigated and validated. However, the performance of model-based control highly depends on an accurate system performance model and sufficient sensors, which are difficult to obtain for certain buildings. To tackle this problem, a model-free optimal control method based on reinforcement learning is proposed to control the building cooling water system. In the proposed method, the wet bulb temperature and system cooling load are taken as the states, the frequencies of fans and pumps are the actions, and the reward is the system COP (i.e., the comprehensive COP of chillers, cooling water pumps, and cooling towers). The proposed method is based on Q-learning. Validated with the measured data from a real central chilled water system, a three-month measured data-based simulation is conducted under the supervision of four types of controllers: basic controller, local feedback controller, model-based controller, and the proposed model-free controller. Compared with the basic controller, the model-free controller can conserve 11% of the system energy in the first applied cooling season, which is greater than that of the local feedback controller (7%) but less than that of the model-based controller (14%). Moreover, the energy saving rate of the model-free controller could reach 12% in the second applied cooling season, after which the energy saving rate gets stabilized. Although the energy conservation performance of the model-free controller is inferior to that of the model-based controller, the model-free controller requires less a priori knowledge and sensors, which makes it promising for application in buildings for which the lack of accurate system performance models or sensors is an obstacle. Moreover, the results suggest that for a central chilled water system with a designed peak cooling load close to 2000 kW, three months of learning during the cooling season is sufficient to develop a good model-free controller with an acceptable performance.

Insight of S, N co-doped graphene aerogel (double reduction)/cobalt (Ⅱ)-substituted α-Keggin-type polyoxometalate nanocomposites with synergistically enhanced impedance matching and energy conservation performance

Exploring new types of absorbing materials has always been the focus and hot spot of stealth research. As we all know, the best conductivity of absorbing materials is generally in the range of semiconductor. Polyoxometalate is a kind of metal oxygen cluster with semiconductor properties and a good electron acceptor, but there is little research on its absorption property. In this work, we synthesized S, N co-doped graphene aerogel (secondary reduction by ascorbic acid)/cobalt (Ⅱ)-substituted α-Keggin-type polyoxometalate (SNGA(Vc)/α-SiW11Co) nanocomposites through some facile routes. The graphene aerogel and polyoxometalate could analogously play the role of alkali and acid, respectively, attracting each other through electrostatic interaction, in addition to hydrogen bonding (N–H- … O, O–H- … O). By changing the types of element doped graphene aerogels and reduction degree, it could regulate the conductivity and affect the polarization relaxation capacity of SNGA(Vc)/α-SiW11Co nanocomposites. With a filling rate of 1:2.5 in paraffin matrix, the maximum reflection loss was up to −67.9 dB at 17.3 GHz and 1.6 mm. There was also another strong absorption peak value of −63.7 dB at 3.5 mm and 6.9 GHz. The absorption bandwidths with the RL value lower than −10 and −20 dB remarkably reached as strong as 14.1 and 13.4 GHz when the thickness range was 1.5–5 mm, respectively, meaning the super electromagnetic wave absorption ability of SNGA(Vc)/α-SiW11Co nanocomposites. This study demonstrates that the polyoxometalate composite materials can become a novel idea for designing high-efficiency electromagnetic wave absorbers.

Interstellar‐based topology control scheme for optimal clustering performance in WSN

SummaryClustering is one of the essential operations in wireless sensor network (WSN) to ensure organized data aggregation followed by energy efficiency. However, obtaining optimal clustering performance is yet an unsolved problem in WSN. Review of existing approaches towards cluster optimization shows that effective balance between energy efficiency and topology control is still missing. Therefore, the proposed system presents a unique topology control mechanism using a novel concept of interstellar orientation toward optimizing the clustering performance in WSN. Adopting an analytical research methodology, the proposed system introduces two interstellar‐based topology control system, which targets the maximum saving of resource consumption of the cluster head. The simulated outcome of the study shows that the proposed topology control system offers significant energy conservation performance in comparison to the existing hierarchical clustering scheme in WSN.

Investigation on the optical and energy performances of different kinds of monolithic aerogel glazing systems

Aerogel glazing system is an advanced energy-efficient glazing system designed to reduce the building energy consumption. However, there is no study focused on the energy performances of aerogel glazing systems filled with different aerogels. To analyse the energy performance, the solar extinction coefficient is an indispensable parameter, which is unknown yet. In this research, the solar extinction coefficient is calculated by Mie scattering and Monte Carlo method. The spectral distribution of solar irradiance is taken into account. The influences of porosity and nano-particle’s size are discussed. Then, the solar heat gain coefficients of different aerogel glazing systems versus incidence angle are calculated. Finally, a dynamic heat transfer model is used to simulate the energy performances of different aerogel glazing systems. A case study is carried out for Hong Kong. The results indicated that the porosity of monolithic aerogel has greater influence than the diameter, and the reciprocal effect between the porosity and the diameter is negligible. It is also figured that aerogel with small nano-particle and low porosity will lead to a better energy conservation performance in cooling dominated region.

パッシブタウンにおける集合住宅の省エネルギー性・住環境の研究 （第３報）居住者アンケート調査による温熱環境評価

パッシブタウンにおける集合住宅の省エネルギー性・住環境の研究 （第３報）居住者アンケート調査による温熱環境評価