Intelligent buildings have drawn considerable attention due to rapid progress in communication and information technologies. These buildings can utilize current and historical data, collected from ...occupancy detection and monitoring networks, to predict occupancy profiles and adjust heating, ventilating, and air conditioning (HVAC) operations accordingly. This adjustment aims to minimize the energy consumption of HVAC systems while maintaining an acceptable level of thermal comfort and indoor air quality. To provide a trade-off between these conflicting objectives, a variety of occupancy-based control strategies have been proposed in the literature. The present article aims to review the research works concerning occupancy-based control systems, classify them based on the integration of occupancy information with control systems and identify their strengths and limitations. Finally, research gaps in this field are discussed from different aspects, including performance evaluation metrics, control methods, occupancy models and buildings types. Future research directions are also proposed to fill the identified gaps.
•HVAC control systems are classified based on their integration with occupancy information.•Occupancy-based HVAC control systems are reviewed.•The limitations of occupancy models and control systems are discussed.•Research gaps are identified by reviewing occupancy-based control systems from different viewpoints.•Future research directions are proposed to fill the current gaps.
The drive to design modern low-environmental impact buildings with high-energy efficiency has led to an increase in unfired earth masonry studies reflecting the rising trend of earth used in passive ...buildings. This paper deals with the efficacy of incorporating biosourced earth in the building envelope. Firstly, the development and the hygro-thermo-mechanical characterization of earth blocks biosourced with local agro-aggregates (Alfa fibers and sawdust) were conducted. An aggregate-to-earth replacement ratio of 8 wt% was adopted. Mechanical tests show that earth blocks alone have a compressive strength of about 1.7 MPa. The hygrothermal tests reveal that biosourced blocks exhibit excellent hygrothermal properties, especially specimens with short Alfa fibers. A twofold decrease in the thermal conductivity value and a significant increase of the time lag and sorption capacities were achieved. The moisture buffering tests show that Alfa fibers improve the buffering capacity of earth from 1.9 to 2.3 g/(m2.%RH), leading the blocks to be classified as “Excellent” humidity regulators. Following the laboratory tests, and to overcome the low mechanical strength of earth, a double hollow brick wall integrating biosourced earth was studied. Building-scale benefits during summer were identified using a validated PMV-PPD model, implemented in EnergyPlus, based on real-time monitoring of an existing building. The findings show that the proposed wall increases thermal comfort by regulating indoor temperature and humidity, reducing 24.6% in dissatisfied occupants compared to typical walls. It is concluded that the use of earth presents a sustainable practice for constructing eco-efficient buildings with enhanced occupant satisfaction in hot regions.
•Bio-based earth blocks used for the design of modern eco-efficient building envelopes.•Sorption isotherms, moisture buffering values (MBV) and thermophysical properties were experimentally characterized.•Field assessment of summer thermal comfort of an existing office building was conducted.•Calibrated PMV-PPD-based model was implemented for simulating the occupant dissatisfaction in buildings.•Hybrid walls (adobe/red bricks) improve the occupant satisfaction in buildings in hot climates.
Zinc‐iodine batteries (Zn‐I2) are extremely attractive as the safe and cost‐effective scalable energy storage system in the stationary applications. However, the inefficient redox kinetics and ...“shuttling effect” of iodine species result in unsatisfactory energy efficiency and short cycle life, hindering their commercialization. In this work, Ni single atoms highly dispersed on carbon fibers is designed and synthesized as iodine anchoring sites and dual catalysts for Zn‐I2 batteries, and successfully inhibit the iodine species shuttling and boost dual reaction kinetics. Theoretical calculations indicate that the reinforced d‐p orbital hybridization and charge interaction between Ni single‐atoms and iodine species effectively enhance the confinement of iodine species. Ni single‐atoms also accelerate the iodine conversion reactions with tailored bonding structure of I─I bonds and reduced energy barrier for the dual conversion of iodine species. Consequently, the high‐rate performance (180 mAh g−1 at 3 A g−1), cycling stability (capacity retention of 74% after 5900 cycles) and high energy efficiency (90% at 3 A g−1) are achieved. The work provides an effective strategy for the development of iodine hosts with high catalytic activity for Zn‐I2 batteries.
Ni single atoms highly dispersed on carbon fibers is designed and synthesized as iodine anchoring sites and dual catalysts for Zn‐I2 batteries, and successfully inhibit the iodine species shuttling and boost dual reaction kinetics. Consequently, the high‐rate performance (180 mAh g−1 at 3 A g−1), cycling stability (capacity retention of 74% after 5900 cycles) and high energy efficiency (90% at 3 A g−1) are achieved.
Solar-driven water evaporation represents an environmentally benign method of water purification/desalination. However, the efficiency is limited by increased salt concentration and accumulation. ...Here, we propose an energy reutilizing strategy based on a bio-mimetic 3D structure. The spontaneously formed water film, with thickness inhomogeneity and temperature gradient, fully utilizes the input energy through Marangoni effect and results in localized salt crystallization. Solar-driven water evaporation rate of 2.63 kg m
h
, with energy efficiency of >96% under one sun illumination and under high salinity (25 wt% NaCl), and water collecting rate of 1.72 kg m
h
are achieved in purifying natural seawater in a closed system. The crystalized salt freely stands on the 3D evaporator and can be easily removed. Additionally, energy efficiency and water evaporation are not influenced by salt accumulation thanks to an expanded water film inside the salt, indicating the potential for sustainable and practical applications.
Heterogeneous networks provide flexible deployments for operators to improve spectrum efficiency and increase coverage. However, driven by new generation wireless devices, the exponential increase of ...data traffic has triggered new challenges of wireless networks to meet the green communications requirement. Therefore, energy-efficient design has emerged as a promising technique in heterogeneous networks. In this paper, we investigate the energy efficiency maximization problem for downlink transmissions by jointly considering user association and power allocation in a two-tier heterogeneous network with multiple small cells. We first consider a system model without the co-channel interference between small cells. The energy efficiency maximization problem is formulated under certain prescribed quality-of-service requirement and maximum power limit constraint. The original optimization problem is non-convex and NP-hard, and it involves integer programming. We first relax the formulate problem into a continuous one and decouple it into user association and power allocation subproblems. A gradient-based algorithm is used to solve the power allocation problem. Then, an iterative joint user association and power allocation algorithm is proposed to achieve the maximum energy efficiency. Moreover, we consider a more sophisticated system with the limited bandwidth resource, in which multiple small base stations require to share the same frequency band to serve users, and the co-channel interference is introduced. Inspired by the original Dinkelbach method, we use a lower bound approximation and the Lagrangian approach to derive a closed-form expression of power allocation, which reduces the computational complexity. Simulation results show that the proposed algorithms have improved energy efficiency when compared with other the existing schemes.
Mixed matrix membranes (MMMs) are one of the most promising solutions for energy-efficient gas separation. However, conventional MMM synthesis methods inevitably lead to poor filler-polymer ...interfacial compatibility, filler agglomeration, and limited loading. Herein, inspired by symbiotic relationships in nature, we designed a universal bottom-up method for in situ nanosized metal organic framework (MOF) assembly within polymer matrices. Consequently, our method eliminating the traditional postsynthetic step significantly enhanced MOF dispersion, interfacial compatibility, and loading to an unprecedented 67.2 wt % in synthesized MMMs. Utilizing experimental techniques and complementary density functional theory (DFT) simulation, we validated that these enhancements synergistically ameliorated CO
solubility, which was significantly different from other works where MOF typically promoted gas diffusion. Our approach simultaneously improves CO
permeability and selectivity, and superior carbon capture performance is maintained even during long-term tests; the mechanical strength is retained even with ultrahigh MOF loadings. This symbiosis-inspired de novo strategy can potentially pave the way for next-generation MMMs that can fully exploit the unique characteristics of both MOFs and matrices.
Environmental concerns and the rise in energy costs have heightened the focus on reducing CO2 emissions within the built environment. By concentrating on the office market in the UK, where a ...significant portion of a service-based economy operates, progress towards achieving emission reduction goals could be accelerated. Nevertheless, the speed at which this sector can enhance its environmental impact and whether individuals are willing to invest in energy-efficient measures and new energy-efficient buildings has remained uncertain. This paper investigates the influence of varying Energy Performance Certificate (EPC) ratings on the rental rates of office buildings in the UK, drawing on an extensive dataset spanning the years of 2011–2021. Our research seeks to determine whether there exists a willingness to pay for more energy-efficient office spaces by assessing whether there is a rental premium associated with office building with higher EPC ratings. Furthermore, we examine whether buildings failing to meet minimum energy efficiency standard (defined as EPC ratings of F and G) experience rental discounts. Our findings, which take into account heteroscedasticity and various disaggregations within the office market, consistently reveal a willingness to pay for energy-efficient office spaces.
Financial incentives or disincentives in the form of electricity tariffs can be used to encourage energy efficiency. In this paper, two simple tariffs aimed at residential consumers are reviewed: ...progressive tariffs (PTs), which penalise high consumption of electricity, and electricity saving feed-in tariffs (ESFITs), which provide incentives to reduce consumption of electricity. The effectiveness of these tariffs is quantified and compared using the price elasticity (for PT) and an incentive elasticity (for ESFIT). The results indicate that PTs are more effective in mobilising electricity saving than ESFITs and confirm biases in human decision-making (here loss aversion). While further research is necessary, we propose a tariff which would motivate consumers to reduce their consumption by offering both an incentive for reaching an energy saving goal and a disincentive for failing to reach this goal. The flexibility of such a tariff makes it a promising solution suitable for application in countries with a comparatively high household income and liberalised retail electricity market.
•Two types of tariffs for saving electricity are reviewed.•Their effectiveness is quantified using price elasticity or incentive elasticity.•We find tariffs with a penalty more effective than those providing an incentive.•A tariff which includes both incentives and penalties is proposed.
•Recent studies performed on use of nanofluids in electronics cooling are reviewed.•Directions for future research and challenges existing in this area are presented.•Employing nanofluids can ...considerably improve electronics cooling in the future.
With increase of heat generated by new electronic components, a combination of nanofluid characteristics and minichannel attributes has been introduced as a hot research topic. Development of such technology can result in further miniaturization of electronic equipment and also improve energy efficiency. In this article, the recent studies performed on use of nanofluids in electronics cooling are reviewed considering several aspects such as liquid block type, numerical approach, nanoparticle material, energy consumption, and second law of thermodynamics. Besides, some interesting aspects about employing nanofluids in cooling of electronic components are introduced. Furthermore, the opportunities for future studies as well as the challenges existing in this field are presented and discussed. It is found that applying nanofluids as novel coolants in different liquid blocks and heat pipes can considerably improve electronics cooling technology in the future.
Sustainability is a strategic choice for the transition to a green economy in China. Improving green total factor energy efficiency (GTFEE) is the key to realizing the dual targets of energy-saving ...and economic growth. This paper empirically tests the nonlinear effects of environmental regulation on technical innovation affecting GTFEE by using panel data of 271 prefecture-level cities in China from 2004 to 2019. Meanwhile, a system GMM approach is used to verify the channels through which technical innovation affects GTFEE. Finally, the spatial and temporal characteristics of technical innovation affecting GTFEE are analyzed from the perspective of environmental regulation. The empirical results are as follows: (1) Technical innovation can significantly improve GTFEE. However, this improvement effect is a threshold characteristic; when environmental regulation is above the threshold value, technical innovation has a greater improvement effect on GTFEE. (2) Besides directly influencing GTFEE, technical innovation can also indirectly influence GTFEE via channels such as economic growth effect, industrial structure upgrading effect, and foreign investment effect. Meanwhile, indirect influence channels also show environmental regulation heterogeneity. (3) The number of cities crossing the threshold of environmental regulation in China increases year by year, which helps technical innovation play a role in improving GTFEE. However, there are still a small number of cities that do not cross the threshold during the sample period, which should attract the attention of local governments.
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