Annual Energy Consumption Research Articles

Exergy analysis of a new spray cooling system-based PV/T and heat recovery with application in sow houses

The uncertain cooling effect and additional huge primary energy consumption caused by humidity regulation are currently the main problems of traditional environmental regulation systems in sow houses. In this study, a new spray cooling system is proposed based on PV/T and heat recovery in sow houses. Meanwhile, the mathematical models are established for its key equipment and their reliability is verified according to literature data. The results show that the maximum error is less than 14.5 % for the models. Based on the above models, the annual operation modes are determined for the new system. Specifically, its annual operation modes mainly include the cooling season, the heating season, the transitional spring and the transitional autumn. Meanwhile, the exergy loss and energy consumption are analyzed for the new system in four seasons through simulation. The results show that in the cooling and heating seasons, the exergy loss first decreases and then increases with the increase of spray power (SP) and mass flow rate of circulating water (MFRW). In the transition season, the exergy loss decreases with the increase of MFRW, while it first decreases and then increases with the increase of SP. However, the annual energy consumption increases with the increase of SP and MFRW. Aim at the minimum exergy loss of new system, its optimal control parameters are obtained in four seasons through optimization. Specifically, when the mass flow rate of supply air is the minimum ventilation rate required by sows, the optimal SP and MFRW are recommended as 40 kW and 12245 kg/h in the cooling and heating seasons, respectively. Meanwhile, they are recommended as 35 kW and 12245 kg/h in the transition season, respectively. The above research can provide guidance for the improvement of traditional spray cooling systems and the performance optimization of new system.

Techno-economic analysis of a novel retrofit solution for the domestic hot water system: A comparative study

The retrofit solution for domestic hot water (DHW) system in existing buildings requires to ensure the long-term energy security and efficiency as well as to minimise occupants’ disturbance, construction works and installation costs. In this regard, the present study performs a techno-economic evaluation on a novel retrofit solution for DHW production in a pilot building. The proposed solution appoints a substantial role to the thermal energy storage through a 2-pipe hot water network utilisable for both DHW and heating purposes. The first storage level is provided by a centralised buffer storage supplied by a PV-BESS-driven heat pump while the second level consists of decentralised modular tanks installed in each dwelling for the production and storage of hot water. Firstly, experimental thermal performance of the proposed decentralised storages is investigated. By developing a dynamic simulation code, the energy efficiency of the proposed solution is compared to that of the existing system in the pilot building as well to that of a typical centralised system as a benchmark solution. Finally, economic analysis of the retrofit solution is performed to address capital expenditures of the system, including purchasing and installation costs, as well as its life cycle cost (LCC). The obtained results indicate that the proposed system reduces the annual energy consumption for DHW production more than 7,200 kWh, with respect to the existing DHW system. Furthermore, it is shown that, in the proposed system, the fraction of thermal loss from piping network decreases by 31.5%, compared to a typical DHW centralised system. Economic assessment of the proposed solution implies that this system, in terms of both mechanical and electrical components, requires 13.7% lower initial investment than a typical centralised system. However, the cost of control systems in this system is higher since it is inherently a control-based system.

Analysis and Evaluation of Indoor Environment, Occupant Satisfaction, and Energy Consumption in General Hospital in China

Different functional areas within general hospitals have varying environmental requirements, with relatively high energy consumption. A comprehensive evaluation of the operational performance’s rationality is of great significance in hospitals’ energy conservation efforts. This study conducted an annual post-occupancy evaluation of a general hospital located in a hot summer and cold winter area in east of China. Two hundred and seventy-eight valid online satisfaction questionnaires, sixty valid point-to-point questionnaires, indoor environment data of each typical season, and energy consumption data were obtained. The overall indoor environment of the selected hospital met the standard requirements. The results showed that occupant satisfaction was influenced by gender, working hours, and length of stay. The annual energy consumption level of this building was 84.7 kWh/m2, which is significantly lower than that of other public general hospitals in China and general hospitals in developed countries. The energy consumption of the inpatient department was directly related to the hospital days, with an increase of 12.2 kWh/m2 for every 1000 additional hospital days. A new indoor environment quality (IEQ) model and a new comprehensive evaluation model for energy efficiency were established. Overall, the outpatient department exhibited superior performance compared to the inpatient department. These evaluation models can help owners and decision-makers in the identification of environmental performance in hospitals.

Evaluating Savings Potentials Using Energy Retrofitting Measures for a Residential Building in Jeddah, KSA

Residential buildings in the Kingdom of Saudi Arabia (KSA) contribute to nearly half of the overall electricity consumption in the building stock, highlighting their significant role in energy consumption. While an upgraded energy code has been established and enforced for new buildings, existing buildings continue to operate at the same level of energy consumption. Therefore, there is a need for further energy upgrades in existing buildings. This study evaluates the energy savings potential of various energy retrofitting measures for a case study in Jeddah, KSA. Data from previous studies and current practices were collected and analyzed. Different energy upgrade measures, such as windows replacement, wall insulation upgrade, roof insulation upgrade, and air conditioning unit replacement, were selected and evaluated using a digital simulation tool called Design-Builder. The simulation results were compared to understand the potential percentage of energy savings. The average annual energy consumption (AAEC) was used as the primary performance indicator to compare the energy savings among the scenarios. The results demonstrate significant reductions in energy consumption for the proposed scenarios. Furthermore, the study examined the significant impact of uncertainties, specifically, the infiltration rate and AC setback temperature, on AAEC. In conclusion, the proposed scenarios have the potential to achieve substantial energy savings, ranging from 25% to 66%, depending on the number of energy retrofitting interventions employed. The findings of this study can serve as a useful reference for similar energy retrofitting projects.

Process design and 4E analysis of different distillations of ethyl acetate/ethanol/cyclohexane separation based on extractive and pressure-swing properties

In this study, we proposed and compared extractive distillation, extractive pressure-swing distillation (EPSD), and pressure-swing distillation (PSD) techniques for the efficient separation of the ethyl acetate/ethanol/cyclohexane pressure-sensitive azeotropic mixture. Based on the influence of the extractant on the relative volatility and the analysis of the ternary phase diagram, dimethyl sulfoxide was selected as the extractant for extractive distillation. The pressure range for PSD was also determined. We employed the non-dominated sorting genetic algorithm II to optimize different processes, considering equipment and operation costs as the objective functions. After the multi-objective optimization, the decision solution was selected using the minimum distance method. A heat exchange network was also used to explore the energy-saving effects of different processes. The aforementioned processes were comprehensively evaluated based on economic, energy, environmental, and exergy analyses. The process results were correlated with the phase diagram based on the normal distance. The total annual cost, energy consumption, gas emissions, and energy loss of the improved processes decreased by more than 10%, 15%, 16%, and 3%, respectively, compared to those of the conventional process. Among the conventional and improved processes, EPSD and heat-integrated EPSD were identified as the best, respectively.

BUILDING ENVELOPE RETROFIT FOR ENERGY SAVINGS IN MALAYSIAN GOVERNMENT HIGH-RISE OFFICES: A CALIBRATED ENERGY SIMULATION

With over a third of global energy used for building construction and operation, an optimum design for building envelopes is essential to improve the energy performance of the existing buildings. This study revealed that typical government high-rise office buildings in Malaysia have an average Building Energy Intensity (BEI) of 161 kWh/m2/year before any upgrading works on the air-conditioning and mechanical ventilation (ACMV) systems were conducted. This value is higher than the recommended value in Green Building Index (GBI) for commercial office buildings (150 kWh/m2/year) and the Economic Planning Unit (EPU) standard for public buildings (140 kWh/m2/year). Therefore, this study employed a case study approach combined with calibrated computer simulation to determine the optimal building envelope retrofit strategies and identify the three levels of interventions (minor, moderate and major levels) with corresponding energy reduction. A validated model representing a typical existing government high-rise office building in Malaysia was chosen as the base case model for energy evaluation studies. The effectiveness of each level of intervention and its energy retrofit measures (ERMs) were evaluated compared to the actual electricity bills. The results showed that all levels of interventions provided between 4% to 7% savings in annual energy consumption. The proposed interventions demonstrated compliance with the BEI benchmark margins of the GBI and EPU standard, namely 116 kWh/m2/year (minor intervention level), 113 kWh/m2/year (moderate intervention level), and 110 kWh/m2/year (major intervention level).

Evaluation of energy efficient building envelope alternatives for sustainable cities

This study is aimed to create an exemplary project to present the contribution of the new buildings to energy savings when the residential buildings are transformed into green buildings. To create a sustainable built environment in residences, this study emphasizes that low-energy building strategies be combined with efficient and high-performance natural-sourced materials. Our findings show that using a natural-sourced material as the building envelope material has an impact on the use of primary energy and energy costs of the alternatives studied. In this study; In the case of replacing the building external wall components of an existing construction designed with internal insulation in the climatic conditions of Ankara, the change in energy performance has been investigated. The analysis was done with the help of BIM-based Revit Program and “Green buildings studio” where energy simulations were created. In the study, 54 different wall combinations were created by modeling combinations of different construction (porous, gas concrete, and pumice bricks), insulation (glass wool, rock wool, sheep wool, PUR, XPS, and EPS) and, roof (tile, asphalt shingle, and green roof) materials. When the outputs obtained from the analyzes were evaluated, the lowest energy consumption values were observed in the combination of pumice brick wall, green roof, and polyurethane insulation materials. In this scenario, the annual fuel consumption per square meter is determined as 30000.6 MJ/m2. On the other hand, the highest energy consumption values were observed in the combination of porous brick wall, tile roof and sheep wool insulation materials. In this scenario, the annual energy consumption per square meter is determined as 30026.6 MJ/m2. Although there are not high numerical differences between the findings, it has been observed that the results give consistent results with the thermal conductivity coefficients of the materials used in the combinations.

Light‐Driven Dinitrogen Activation with Transition Metal Complexes: Mechanisms and Applications†

Comprehensive SummaryThe Haber‐Bosch process, which is used for ammonia (NH3) synthesis, requires vast amounts of energy, accounting for approximately 1%—2% of the world's annual energy consumption. Therefore, researchers in both industry and academia are interested in developing sustainable and environmentally friendly methods for synthesizing nitrogenous compounds at ambient conditions using renewable energy sources such as visible light. While several examples of thermal activation of dinitrogen molecules have been demonstrated using various transition metals and ligand frameworks, the use of light to weaken or split the strong N—N bond has been less explored. This article presents an overview of molecular complexes capable of dinitrogen photocleavage and provides mechanistic insights into the photoactivation process through experimental and theoretical studies. We believe this review will provide readers with an in‐depth understanding of the current state‐of‐the‐art and future research perspectives, particularly in the use of visible light for dinitrogen activation and transformation.

Impact of energy conservation measures in residential buildings in very remote communities in Australia

This study investigated the impact of various energy conservation measures (ECMs) on total annual electricity consumption on a single level, two-bedroom residential building in an arid climate and in a very remote area of Australia. Base case scenario of annual energy consumption profiles of the building and its existing systems were modelled and simulated using DesignBuilder software, and the results were validated by on-site measured electricity data. Two categories of ECMs (major intervention and minor intervention) were investigated and analysed. The findings show that the total annual energy consumption of the case study building can be reduced by up to 44% (2 kWh/m2·yr) when compared against the base model and measured data if selected ECMs are implemented. Significant savings from implementing selected ECMs can help alleviate the cost-of-living pressure and stress currently experienced by many households on low incomes especially for residents of very remote communities in Australia.

Economic and environmental assessment of a green pavement recycling solution using foamed asphalt binder based on LCA and LCCA

Cold-in-place recycling with foamed asphalt binders (CIR-F) has been considered as an environmentally sustainable option for asphalt pavement maintenance due to the low mixing temperature and the reuse of up to 100% of existing asphalt materials. However, the quantitative assessment of its economic and environmental performance from a life cycle perspective has rarely been addressed in the literature. To fill in the gap, this study conducted cradle-to-laid life cycle assessment (LCA) and life cycle cost analysis (LCCA) to estimate the annual energy consumption, carbon emissions, and equivalent uniform annual cost (EUAC) of CIR-F and compared it with the traditional mill & fill (M&F). The considered life cycle stages include raw material production, construction, transportation, and work zone traffic management. The heat map visualization technique was employed to explore the influence of service life on the relative environmental and economic advantages of CIR-F. The results show that both economic and environmental impacts of CIR-F were significantly reduced compared to conventional M&F, with 66.45% less cost, 59.62% less energy consumption and 45.73% less carbon emissions. Reducing the service life of CIR-F will reduce, or even completely offset, its benefits over M&F. Assuming a service life of 15 years for conventional M&F, the service life of CIR-F needs to be greater than 8 years to maintain its environmental advantage. The results of this study provide a quantitative assessment of the economic and environmental benefits of CIR-F, providing evidence for its broader application.

Methodology for retrofitting energy in existing office buildings using building information modelling programs

Retrofitting existing buildings to raise energy efficiency is a highly important requirement, Because the problem of climate change has made the concept energy-saving an increasingly popular concept as a solution to this problem. Most of existing buildings are not sustainable and here is the problem, constructing new buildings are not Just enough to be energy efficient. Existing buildings consume approximately 60 % of global energy consumption. It’s easy to achieve low energy consumption through retrofits of existing buildings, The problem is to find such a program that helps in drawing, imagining, simulating, analyzing and documenting projects in a more accurate and easy way and in a short time, so the aim of this research is to develop a framework for the integration of BIM and retrofitting categories, This will be achieved by combining the most effective strategies of deep retrofitting that has resulted in annual energy consumption reduction by 68%. Suez Canal university office building was chosen as a case study. We noticed that using Revit program is easier and faster than the DesignBuilder program in simulating energy, but the Revit program needs to be developed. The retrofitting solutions proposed in this study can be used to achieve certification of LEED.

A hybrid machine learning approach for forecasting residential electricity consumption: A case study in Singapore

Ensuring effective forecasting of buildings' energy consumption is crucial in establishing a greater understanding and improvement of buildings' energy efficiency. In Singapore, domestic electricity usage in public residential buildings takes up a significant portion of the country's annual energy consumption. Having effective forecasting approaches is thus important in supporting relevant strategies and policy making. In this research, we proposed a hybrid approach that was based on a combination of building characteristics and urban landscape variables to predict residential housing electricity usage in Singapore. XGboost was also incorporated inside the hybrid approach as the preferred machine learning approach for energy consumption predictions. To demonstrate our proposed approach's predictive strength, the performance of our proposed hybrid machine learning approach was compared with two other models, Geographically Weighted Regression (GWR) model and the Random Forest (RF) model. Results showed that our proposed hybrid model had outperformed these abovementioned approaches with higher accuracy (r2 value of 0.9). The proposed approach had thus been effective in forecasting electricity consumption for public housing in Singapore, and it could also be utilised in other similar urban areas for future electricity consumption forecasting.

ICT Implications for a Pilot Water Treatment Plant Using Simulation Modeling

The current work is an illustration of an empirical investigation conducted on a pharmaceutical water treatment plant that subsequently proposes potential ICT implications for optimizing the plant’s conventional operating procedures and improving production efficiency. Typically, the pilot plant incorporates a standard infrastructure for maintaining quality and production goals. In the study, a schematic of the reverse osmosis section of the pilot treatment plant was developed. A mathematical modeling and process simulation approach was adopted to carry out the linear process investigation and validation of key performance parameters. The study’s findings reveal that the performance and lifecycle of the RO treatment unit are primarily determined via the structured pre-treatment filtering procedures, including critical parameters such as volumetric flowrate, solute concentrations, and differential pressure across the membrane. These operational parameters were also found to be instrumental in increasing plant production and improving equipment efficiency. Based on our results, the study proposes cost-effective ICT implications for plant managers through which pilot organization can substantially save on their annual water and energy consumption.

Investigating the heating and air conditioning provision capability of a supermarket to neighboring buildings: Field measurement analysis and economic evaluation

This study explores the capability of a supermarket to fulfill the thermal demands of neighboring buildings. The research combines field measurements analysis, obtained from a Swedish supermarket which covers the neighbors' thermal demands, with theoretical calculations, using thermodynamic models of the refrigeration system and the ground source thermal storage. In contrast to previous studies, this work is unique in its use of demonstrating a real-life built case study rather than only theoretical approach. Results demonstrate that integrating ground source storage in a supermarket can meet the thermal demands of neighboring buildings without requiring additional equipment. The refrigeration system accounts for 80% of the total heat demand, while the ground serves as a heat source for the rest. This approach results in 67% annual operating cost savings for the neighboring buildings. In addition, ground source subcooling provides 9% annual energy savings to supermarket's refrigeration system. By exporting heat to neighboring buildings, the proposed solution emits 90% less CO2 in Uppsala and 67% less in Stockholm compared to solutions in which the refrigeration system only meets the refrigeration demands. Summing up, the concept of utilizing supermarkets to meet thermal demands offers a more energy-efficient operation for both supermarkets and property owners while significantly reducing annual energy consumption and emissions.

Experimental investigation of an autonomous liquid-cooled uninterruptible power supply (UPS)

This paper presents a new liquid-cooling technology for uninterruptible power supply (UPS) units in which an air-cooling system is combined with an indirect water-cooling system based on direct-chip cooling. This cooling architecture provides more opportunities to use free cooling as the main or only cooling system for optimal data centres (DCs). An experimental investigation was conducted using a 600 kW SOCOMEC UPS to identify the thermal behaviour of the system. Five thermal hydraulic tests were conducted under different thermal conditions, flow rates, and room temperatures. A 20 K temperature difference profile was validated with a safe operation of all UPS electronic equipment with a water flow rate of 13 l/min and inlet water and air room temperatures of 32 and 40 °C, respectively, resulting in a thermal efficiency of 82.27%. The experiments suggest that a DC-facility water-inlet temperature up to 41 °C is acceptable for UPS units. The effects of decreasing the water flow rate and increasing the water and air room temperatures were also analysed. A decrease in inlet water and air temperatures from 41 °C to 32 °C and from 47 °C to 40 °C, respectively, increased the thermal efficiency by 8.64%. A decrease in water flow rate from 20 l/min to 13 l/min reduced the thermal efficiency by 7.7%. Furthermore, an energy performance analysis comparison was performed between air- and water-cooled UPS units at both the UPS and infrastructure levels. A case study of a 600 kW UPS in a data centre in Roubaix, north of France, was investigated. The liquid-cooled UPS reduced the total annual energy consumption of the cooling system by at least 85% compared with an air-cooled UPS.

Towards rural net-zero energy buildings through integration of photovoltaic systems within bio-based earth houses: Case study in Eastern Morocco

Off-grid rural electrification programs involving renewable energy provide effective ways to boost the availability of power in remote areas. Herein, the combination of local bio-based building materials with appropriate sizing of a photovoltaic (PV) system to achieve energy-efficient rural housing in developing countries is investigated. The study focused on the fabrication and laboratory testing of a building material incorporating plant fibers, followed by a feasibility analysis of an integrated stand-alone PV system. EnergyPlus software was used to assess the energy-saving potential of bio-based building envelopes, and Homer Pro software was used for techno-economic optimization. Using a case-study building, various configurations were evaluated in terms of levelized energy cost and net present cost. According to the experimental results, the inclusion of 8 wt% Alfa fibers in earth blocks led to a noteworthy enhancement in the thermal resistance and time lag of the building envelope. Specifically, the improvement ranged from 0.549 to 1.125 m2K/W and from 18.5–h to 23.2–h, respectively, compared to using earth alone. This improvement resulted in a substantial decrease in the building's annual energy consumption, with a reduction of 24.3% for heating and 26.7% for cooling. Furthermore, the techno-economic analysis revealed that the electricity provided by a PV-battery hybrid system was 100% renewable and emission-free, with an energy cost of approximately $0.218/kWh and a present net cost of $11,560.21 These findings indicated that combining available solar energy with locally produced bio-based construction materials could be a viable approach for achieving carbon neutrality and building energy-efficient ulta-low-cost rural housing.

Impact of Climate Change on the Heating Demand of Buildings. A District Level Approach

In the 21st century, the importance of energy generation and carbon emissions in developing countries is indisputable. In the whole wide world, the building stock is responsible for the two fifths of the total world annual energy consumption. Considering the predictions regarding future climate due to climate change, a good understanding on the energy use due to future climate is required. The aim of this study was to evaluate the impact of future weather in the heating demand and carbon emissions for a group of buildings at district level, focusing on an area of London in the United Kingdom. The methodological approach involved the use of geospatial data for the case study area, processed with Python and Anaconda through Jupyter notebook, generation of an archetype dataset with energy performance data and TABULA typology and the use of python embedded in QGIS to calculate the heating demand in the reference weather data, 2050 and 2100 in accordance to RCP4.5 and RCP 8.5 scenarios. A validated model was used for the district level heating demand calculation. On the one hand, the results suggest that a mitigation of carbon emissions under the RCP4.5 scenario will generate a small decrease on the heating demand at district level, so slightly similar levels of heating generation must continue to be provided using sustainable alternatives. On the other hand, following the RCP 8.5 scenario of carbon emission carrying on business as usual will create a significant reduction of heating demand due to the rise on temperature but with the consequent overheating in summer, which will shift the energy generation problem. The results suggest that adaptation of the energy generation must start shifting to cope with higher temperatures and a different requirement of delivered energy from heating to cooling due to the effect of climate change.

Investigating energy saving and climate mitigation potentials in cement production – A case study in Ethiopia

The cement industry is one of the most energy and emission-intensive sectors, accounting for approximately 7% of total-industrial energy use and 7% of global CO2 emissions. This study investigates the potential energy savings and CO2 abatement in the cement plants of Ethiopia. A Benchmarking and Energy Saving Tool for Cement is used to compare the energy use performance of the individual cement plants to best practices. The study reveals that all the surveyed plants are less efficient, with an average energy saving potential of 36% indicating a significant potential for energy efficiency improvement. Then, twenty-eight energy efficiency measures are identified and analyzed using a bottom-up energy conservation supply curve model. The results show that the cost-effective electrical energy and fuel-saving potentials of these measures are estimated to be 99 Gigawatt hours per year which is about 11.5% of the plants’ annual electrical energy consumption and, 2.7 Petajoules per year which is to be 12.5% of the plants’ annual fuel consumption, respectively. The cost-effective fuel measures have an annual average CO2 emission reduction potential of 254 kilo-tonnes per year which covers about 5% of the total CO2 emission. Sensitivity analysis is conducted using the key parameters that show some discrepancy in the base case results. This study could be used as a reference for policymakers to understand the potential for energy savings and CO2 abatement. It could also be used to design policies in improving energy efficiency in the cement sector.

Enhances of nearly zero-energy public buildings in regions with hot summers and cold winter

Nearly Zero-energy residential buildings have attracted widespread attention due to their superior energy-saving performance. In order to achieve a balance between energy production and demand in residential buildings, the application of renewable energy is essential. This paper optimizes typical zero-energy public buildings in hot summer and cold winter locales using the concepts of passive priority, active optimization, and 100% renewable energy supply guarantee. The importance of passive energy-saving techniques like heating, shading, and heat recovery; in accordance with local resource conditions; analysis of building renewable energy utilization systems like solar energy and air energy; and recommendation of the most technologically efficient building energy system. According to the simulation results, if the criteria for zero-energy buildings are met, the annual energy consumption index per unit area is 37.6 kWh/m2, and the 8.9 kW building photovoltaic system can generate 36.4 kWh/m2 of power annually.

Feasibility investigation on a novel rack-level cooling system for energy-saving retrofit of medium-and-small data centers

Conventional cooling systems in data centers generally adopt computer room air handlers, which have the local hotspot problem and substandard power usage effectiveness. The rack-level cooling system combined with mechanical refrigeration and free cooling is regarded as an effective solution. However, insufficient refrigerant supply and uneven refrigerant distribution problems often occur in the widely-used rack-level system based on backdoor evaporators. To overcome above mentioned shortcomings, a novel rack-level cooling system equipped with an assisted refrigerant pump for backdoor evaporators and a large-capacity reservoir is proposed. Then, the experimental studies are carried out to validate the cooling performance of the proposed system in a self-designed platform, and results indicate that the proposed system can supply sufficient refrigerant, which is beneficial for uniform refrigerant distribution. Finally, the feasibility is investigated for the energy-saving retrofit of the conventional cooling system in typical cities, and results indicate that the proposed system can save 54%, 49%, and 41% of annual energy consumption in Shenyang, Beijing, and Chengdu respectively, and the corresponding payback period is estimated at 4, 3.5, and 5 years. Because there is no electronic expansion valve installed in the inlet of every rack evaporator, it is noted that the outlet air temperature of the rack may not be controlled accurately when there is a large load difference among different racks.