Energy Performance Parameters Research Articles

Thermal performance analysis of corrugated plate solar air heater integrated with vortex generator

This research investigates the impact of vortex generators integrated with a corrugated absorber plate of solar air heater on the enhancement of heat transfer and thermal-hydraulic performance utilizing a 3D numerical model for Reynolds numbers varying from 7,000 to 25,000. Three different types of vortex generators (rectangular, trapezoidal, and delta) are investigated separately. Vortex generators in two pairs with various angles of attack of 15º, 30º, 45º, and 60º are mounted on the entrance section's upper wall of the domain of computation. The current numerical models are validated by comparisons with experimentally published data. The velocity vectors, turbulent kinetic energy, friction factor, Nusselt number, and thermal-hydraulic performance parameters are examined for the considered current cases considered. The numerical results demonstrate a significant impact of vortex generators on friction loss and transmission of heat. The values of thermal-hydraulic performance for utilizing a corrugated absorber plate integrated with vortex generators are found to be considerably higher than those for using a corrugated absorber plate alone. The highest value of the thermal-hydraulic performance parameter is 0.91 in the case of rectangular vortex generators at Re of 7000 and an angle of attack of 30º.

Optimal design of a renewable energy-driven polygeneration system: An application in the dairy industry

The world is experiencing an unprecedented transition towards a low-carbon and renewable-based energy system, driven by the imperatives of mitigating climate changes, building climate resilience and ensuring sustainable development. Recently, polygeneration systems based on renewable energies have emerged as a viable solution to support the energy transition since they can improve resource utilization and energy efficiency, thus reducing the dependency on fossil fuels and the environmental impacts on ecosystems.Renewable polygeneration systems can play a significant role in the decarbonization of the food processing industry due to its high thermal energy demand at low and medium temperature levels.This paper presents a detailed analysis of a renewable polygeneration system integrating solar, geothermal and biomass energies and able to produce electricity, heat and cold water. The novelty of this study is the analysis of polygeneration system configurations relying solely on renewable energies and the optimization of the strategy to control the energy exchange between power systems, storage facilities and utilities. Two system configurations based on different power technologies and control strategies are investigated and compared, considering as end-user a milk production process with hot and cold water requirements at different temperature levels and load profiles.To this end, a dynamic model in Matlab/Simulink has been developed to simulate the behaviour of the polygeneration system over time and evaluate its overall energy performance parameters. For each system configuration, the optimal operating strategy has been identified by maximizing the energy conversion efficiency and minimizing the unmet thermal and cooling loads. Simulation results highlighted that, compared to polygeneration systems relying only on fluctuating renewable energies, those including a backup heat source (i.e., a biomass boiler) were able to meet the thermal energy needs of larger and more complex milk production processes.

Sensitivity analysis and multi-objective optimization of the energy, exergy and thermo-economic performance of a Brayton supercritical CO2-ORC configurations

The following research compared some energy, exergetic and thermo-economic indicators of a supercritical CO2 simple Brayton cycle integrated with a simple organic Rankine cycle (SORC), and a regenerative organic Rankine cycle (RORC). A thermodynamic model was developed to determine the net power, thermal efficiency, the fuel consumption, and the exergy destruction of all the components of the system. Also, a thermo-economic model was developed to determine some economic indicators such as the levelized cost of energy (LCOE), the payback period (PBP) and specific investment cost (SIC). A sensitivity analysis was carried out to study the influence of the primary turbine inlet temperature (TIT), the high-pressure in the compressor (PHigh), the evaporator pinch point temperature difference (PPT), and the pressure ratio (Pr) on the indicators performance. Three different working fluids were selected in this study: acetone, toluene and cyclohexane. The results showed that cyclohexane had the best energy performance giving an efficiency of 48.02% for the RORC system. Besides, it presented the best thermo-economic results for the LCOE (0.26 USD/kWh), SIC (2626.75 USD/kWh), and a PBP (11.2 years). Finally, a multi-objective optimization was developed based on energy, exergy and thermo-economic performance parameters as objective functions to obtain a technical and economic feasible solution able to implement them in industrial applications.

Optimal planning and multi-criteria decision making for effective design and performance of hybrid microgrid integrated with energy management strategy

The dependence on fossil fuels for energy generation resulted in severe environmental challenges, triggering green transition. As a result, there has been massive uptake of renewable energy share in the energy sector, devising new ways of generating energy. Hybrid microgrids are one such system enabling green transition in the energy sector. However, they mostly face planning and feasibility-related challenges. Such challenges become more complex when consumer’s preferences on energy use patterns are considered. Hence, this paper considers designing a hybrid microgrid considering consumer-centric energy management options. A case study has been simulated considering the consumer’s preferences on energy use patterns using a hybrid optimization of multiple energy resources tool for understanding the techno-economic-environmental feasibility through which better planning of microgrid infrastructure can be made. The results include the hybrid microgrid system architecture, capacity size optimization, energy performance and cost parameters. The observed energy potential from the optimally planned hybrid microgrid satisfied the electrical energy requirements. It is observed that the energy management option strongly influences the hybrid microgrid system architecture, capacity size optimization, and cost. Based on the observed results, the best-worst method was implemented for decision-making over the system architecture selection considering multiple decisions over techno-economic and environmental aspects.

Experimental Energetic and Exergetic Performance of a Combined Solar Cooking and Thermal Energy Storage System

Most solar cookers usually perform a single task of solely cooking food during sunshine hours. Solar cookers coupled with thermal energy storage (TES) material for off-sunshine cooking are usually expensive and require complex engineering designs, and cannot be used for dual purposes, for example, solar water heating and cooking. In this paper, a solar cooker that can perform dual tasks of cooking as well as storing thermal energy to be used during off-sunshine periods is presented. The experimental setup is composed of a parabolic dish, a solar receiver coupled with a flat plate and an oil-circulating copper coil for charging and discharging a storage tank. The objective of the experiment is to evaluate the energy and exergy thermal performance parameters of the dual-purpose system during charging and discharging cycles. The effect of the flow rate and the mass of the load are investigated while using sunflower oil as both the heat transfer fluid and the storage material. Charging and discharging experiments are conducted using four different flow rates (2, 3, 4, 5 mL/s), and with different masses (0.5, 1, 1.5, 2.0 kg) with water and sunflower oil as the test loads. The charging results show that the average energy and exergy rates as well as their corresponding efficiencies increase with an increase in the charging flow rate. On the other hand, the increase in the mass load tends to decrease marginally the average charging energy and exergy rates for water, and their corresponding efficiencies. For sunflower oil, the average charging energy and exergy rates and efficiencies showed a more pronounced decrease with an increase in the mass. Water generally shows higher charging and discharging energy and exergy efficiencies compared to sunflower oil with an increase in the flow rate. For discharging results, the correlations between the energy and exergy thermal performance parameters with respect to the flow rate and the heating load are not well defined possibly due to different initial storage tank temperatures at the onset of discharging and the inefficient discharging process which needs to be optimized in future.

Electrification of a Class 8 Heavy-Duty Truck Considering Battery Pack Sizing and Cargo Capacity

The design and performance optimization of fully electric trucks constitute an integral goal of the transport sector to meet climate emergency measures and local air quality requirements. Most studies in the literature have determined the optimum pack size based on economic factors, without accounting for the details of pack behavior when varying the size. In this paper, the effect of battery pack sizing and cargo capacity of a class 8, 41-ton truck on its overall energy performance and technical parameters of its powertrain is investigated. For this purpose, the proposed electric truck is designed and mathematically modelled using AVL CRUISE M software. The second-order equivalent circuit model is developed to predict the battery packs’ parameters. The proposed battery pack model is extracted from experimental analysis on SONY VTC6 lithium-ion batteries performed in the lab. The weight changes due to adding the battery packs to the truck are also estimated and have been taken into account. The mathematical model of the powertrain is simulated in the long-haul driving cycle considering different cargo capacities and battery pack sizes. The results of this study revealed that the battery pack voltage reached its minimum value when the maximum cargo capacity was applied for the 399 kWh battery pack. In addition, increasing the occupied cargo capacity from 10% to 100% resulted in an increase in the regenerative brake energy of up to 9.87 kWh, while changing the battery size imposed minimal impacts on regenerative brake energy recovery as well as energy consumption.

Assessment of Energy Efficiency Measures’ Impact on Energy Performance in the Educational Building of Kazakh-German University in Almaty

As climate change concerns are rising rapidly, energy efficiency promotion and implementation could be sustainable solutions within energy transition. In this context, buildings, including educational ones, play an important role in reducing energy needs and promoting energy efficiency since they account for a significant share of the total energy consumption. As a case study for this research, the educational building of Kazakh-German University was selected. Following the national and international building standards, energy performance parameters were estimated. Current heat losses and performance have been estimated as baseline scenario settings. The impact of retrofitting measures on energy efficiency performance of the buildings under the four scenarios was calculated. Under the minor scenario, retrofitting interventions will lead to annual energy savings of 36.9 kWh/m2 and a 48% CO2 emission reduction, whereas under the major scenario, the annual energy savings will increase to 77.76 kWh/m2 and a nearly 82% CO2 emission reduction. The integration of a solar thermal system with capacity 400 kWh, assuming that the heat demand was reduced under the minor retrofitting scenario, can decrease heat energy consumption and CO2 emissions to 35%. As upfront costs of the energy efficiency measures are high, a carbon offset mechanism could facilitate the implementation of university building modernization.

Interactions between Seismic Safety and Energy Efficiency for Masonry Infill Walls: A Shift of the Paradigm

Currently, the upgrade of existing reinforced concrete (RC) buildings focuses only on energy retrofitting measures due to the current policies promoted in the scope of the European Green Deal. However, the structural deficiencies are not eliminated, leaving the building seriously unsafe despite the investment, particularly in seismic-prone regions. Moreover, the envelopes of existing RC buildings are responsible for their energy efficiency and seismic performance, but these two performance indicators are not usually correlated. They are frequently analyzed independently from each other. Based on this motivation, this research aimed to perform a holistic performance assessment of five different types of masonry infill walls (i.e., two non-strengthened walls, two walls with seismic strengthening, and one wall with energy strengthening). This performance assessment was performed in a three-step procedure: (i) energy performance assessment by analyzing the heat transfer coefficient of each wall type; (ii) seismic performance assessment by analyzing the out-of-plane seismic vulnerability; (iii) cost–benefit performance assessment. Therefore, a global analysis was performed, in which the different performance indicators (structural and energy) were evaluated. In addition, a state-of-the-art review regarding strengthening techniques (independent structural strengthening, independent energy strengthening, and combined structural plus energy strengthening) is provided. From this study, it was observed that the use of the external thermal insulation composite system reduced the heat transfer coefficient by about 77%. However, it reduced the wall strength capacity by about 9%. On the other hand, the use of textile-reinforced mortar improved the strength and deformation capacity by about 50% and 236%, but it did not sufficiently reduce the heat transfer coefficient. There is a need to combine both techniques to simultaneously improve the energy and structural energy performance parameters.

The Role of Local Aggregator in Delivering Energy Savings to Household Consumers

Energy communities, also known as renewable or citizen energy communities, can be a source of innovative aggregation solutions at the local level. The unleashed flexibility potential of households could provide self-balancing services for local energy communities or create new revenue streams for local flexibility aggregators. This paper proposes a methodology for the assessment of the energy savings potential of residential customers, factoring in local climatological conditions, energy consumption patterns, and building energy performance when the available input data are scarce. For baseline consumption modelling, the correlation between historical energy consumption data collected from a survey, building energy performance parameters, and the availability of flexibility assets was determined, taking into account the inconsistency between the quantity and quality of collected data from various consumers. For this purpose, a modelling approach using calculations for “Agent” buildings was used. In this way, each building user was assigned to a specific “Agent” with dedicated consumption characteristics for a flexibility asset. The capacities engaged in a flexibility programme were modelled according to the available flexibility assets, whilst the duration of a flexibility demand response (DR) event was considered a function of building energy performance characteristics, and consequently, activation strategies were applied. Additionally, several energy savings activation scenarios were modelled to interlink technical and behavioural constraints of household consumers. These constraints restrict the available flexibility, thus influencing the possibility of daily repetitions of a DR event and increasing savings with flexibility event activation. This model is intended to optimise flexibility assets provided by the end-users and, in this manner, deliver permanent energy savings, offering new business opportunities for aggregators or local energy communities. The novelty of this research is the recognition of an aggregator as a permanent energy savings provider, even if the obtained savings are very conservative per individual flexibility asset. Nevertheless, if properly aggregated and identified, the obtained savings could create novel business opportunities for a local aggregator.

EXPERIMENTAL EVALUATION OF A CASCADE REFRIGERATION SYSTEM USING R-134a AND R-404a

Cascade refrigeration system is an attractive technology for low-temperature requirement, allowing operation under these conditions with positive suction pressures and a moderate condensation pressure at ambient temperature. This work describes a performance analysis of a cascade refrigeration prototype equipped with hermetic compressors working with R-134a and R-404a as refrigerants, thermally connected by a tube-in-tube-type cascade-condenser. Energy flows and performance parameters were evaluated under different evaporating temperature conditions of the low temperature cycle (LTC). The results showed an increase in energy efficiency ratio (EER) and coefficients of performance (COP) of cascade system as well as of each cycle with the increase of LTC evaporating temperature, even with a simultaneous increase of temperature difference in cascade-condenser.

ENERGY EFFICIENCY OF AGRICULTURAL TRACTORS EQUIPPED WITH CONTINUOUSLY VARIABLE AND FULL POWERSHIFT TRANSMISSION SYSTEMS

The efficiency of agricultural tractor transmission has been improved over the years, with new concepts such as Continuously Variable Transmission (CVT) and Full Powershift (FPS) evolving in advanced technologies. Both options seek to offer the farmer greater operational results with lower energy expenditure, necessitating studies to assess the effectiveness of these technologies and define the best choice for each purpose. The objective of this work was to evaluate the energy efficiency of two tractors equipped with CVT and FPS transmissions. For this, a strip experiment was conducted in a randomized block design, that analyzed, in addition to CVT and FPS transmissions, target velocities of 4, 6, 8 and 10 km h-1. Operational energy performance parameters were evaluated, such as slippage index, engine rotation, operational velocity, fuel consumption, power available and efficiency on the drawbar, turbo pressure and temperatures of air intake and exhaust gas. Based on the results obtained, the tractor with FPS transmission was more energy efficient in most of the analyzed parameters, requiring 16.31% less in hourly fuel consumption, and providing 16.29% more in the traction bar yield, however, with lower operational velocity compared to the tractor with CVT transmission.

Transforming a Historic Public Office Building in the Centre of Rome into nZEB: Limits and Potentials

According to the last census of 2019, about two million Italian buildings are more than 100 years old. Building energy retrofitting involves a diverse mix of influencing factors, depending on history, intended use, and construction techniques. This paper aims to assess the energy needs of a historic building by evaluating the variability of climatic conditions and internal loads, as well as the thermal capacity of the building envelope. The energy analysis was conducted using dynamic simulation systems (TRNSYS). The purpose of the study is to provide an analysis of the current energy conditions of the building to identify the main critical issues and suggest the most suitable interventions to be implemented. All the transformations were conducted to meet the nZEB requirements and evaluate technical and economic feasibility, compatibility with architectural and landscape constraints, and large-scale replicability. Specifically, to reach the proposed targets, a 36 kWp PV system was implemented for an area of 210 m2, in addition to the Air Handling Unit (AHU) already present. The profit index is above the unit, and it yields a time range between three and four years. Therefore, fully respecting the energy performance parameters required by the Italian legislation, the study demonstrated the unattainability of the nZEB class for a listed building.

Neural Network and Theoretical Model for the Prediction of the Energy Performance Indicators of a Centrifugal Pump

Currently, an improvement in the energy performance of energy equipment and processes is required due to the high global energy consumption and polluting emissions. Centrifugal pumps have been extensively implemented in several processes for fluid transportation. Due to the above, in this research, a methodology is proposed. A backpropagation neural network and a theoretical model are used together to predict energy performance parameters such as real head, power consumption, and efficiency. The neural network is built based on different geometric and operational parameters. The results obtained show that the proposed neural network allows predicting the real head, the power consumption, and the efficiency parameters with a maximum error of 0.26%, 2.27%, and 0.15%, which is a precision similar to the one obtained in methodologies such as computational fluid mechanics. The inclusion of the theoretical model in the neuronal network makes it possible to reduce the error within the energy performance prediction of the turbomachinery. In general, an increase in the maximum error of 34.61%, 61.67%, and 126.67% has been observed for the real head, the power consumption, and the efficiency when the theoretical model is not considered. In general, the use of the proposed neural network allows predicting with high precision and rapidly energy performance parameters such as real head, power consumption, and efficiency, which results in a methodology with the potential to be used in optimization processes in centrifugal pumps.

Four-component high-strength polymineral binders

The use of composite binders instead of cement with the use of highly effective types of mineral raw materials, which has gone through the path of multi-stage natural activation due to deep geological processes, is a promising direction of modern construction materials science. The paper is devoted to the development of a resource-saving technology for obtaining high-strength composite binders for energy-efficient construction. The significance of this study is to focus on expanding the raw material base of polymineral binders at the expense of technogenic and substandard materials. The work is aimed at studying the nature of the joint interaction of alumina, silicate and carbonate components from natural and technogenic raw materials, taking into account its genesis in the processes of structure formation of multicomponent hardening systems. The novelty of the work lies in the establishment of regularities for the regulation of the structure and properties of the composite binders with powdered mineral modifiers. Comprehensive researches of natural raw materials included the study of its energy performance and particle sizes parameters after grinding. The synthesized polymineral binders were compared in terms of heat of hydration, rheological and physical–mechanical properties, as well as their microstructure. The developed modified cementitious pastes have a water-binding ratio of no more than 0.3; compressive strength of 81 MPa, flexural strength of 12 MPa. Accordingly, the cement composites have great potential for use in civil engineering.

A review of recent advances in adsorption desalination technologies

Adsorption-based desalination (AD) is an emerging concept to co-generate distilled fresh water and cooling applications. The present study is aimed to provide a comprehensive review of the adsorption desalination systems and subsequent hybridization with known conventional cycles such as the multiple-effect AD (MED), solar regenerable, integrated evaporator-condenser cascaded, and ejector integrated systems. The systems are investigated for energy consumption, productivity enhancement, and performance parameters, including production cost, daily water production, and performance coefficient. Comprehensive economic aspects, future challenges, and future progress of the technologies are discussed accordingly to pave researchers' paths for technological innovation. Traditional AD systems can produce specific daily water production of 25 kg per kg of adsorbent. The solar adsorption desalination-cooling (ADC) showed a promising specific cooling power of 112 W/kg along with a COP of 0.45. Furthermore, for a hybrid MEDAD cycle, the gain output ratio (GOR) and performance ratio (PR) is found to be 40%, along with an augmented water production rate from 60% to two folds. The AD technology could manage the high salinity feed water with the production of low salinity water with a reasonable cost of US$0.2/m3.

Development and experimental analysis of a novel dual-mode counter-flow evaporative cooling device

The recent energy demand for cooling increases rapidly, which has forced researchers to think about the technological shift. Evaporative cooling is an eco-friendly option, uses much less energy. Direct evaporative coolers are used worldwide and effective for arid climates. Regenerative evaporative coolers can cool up to dew point without adding moisture to the supply air. The dual-mode evaporative cooler is a novel idea that can operate in both regenerative and direct modes. In this work, the testing unit of this novel cooler is fabricated and experimentally investigated in both direct and regenerative modes. The important operating parameters (extraction ratio, inlet air temperature, inlet air velocity, inlet air specific humidity, water flow rate and water inlet temperature) are varied to get their effect on energy and environmental performance parameters (supply air temperature, cooling capacity, dew-point effectiveness, COP and CO2 emission). Technical comparison with conventional vapor compression air-conditioner is presented as well. The water inlet temperature affects regenerative mode more as compared to direct mode. The high water flow rate decreases the COP sharply in both modes. Comparison shows that direct mode can be used for higher cooling capacity (lower carbon emission) and COP while regenerative mode can be used for higher effectiveness.

Energy performance and loss analysis of 100 kWp grid-connected rooftop solar photovoltaic system

In the present work, simulation and energy analysis of a grid-tied 100 kWp solar photovoltaic power plant mounted on an institute's building rooftop in Bhopal city of India are carried out. The present study provides insight into the solar power plant's performance linked to the medium range grid under actual operating conditions in Central India. It is observed that the standard performance ratio and the capacity factor of the plant are 80.72% and 19.27% respectively. The average monthly energy produced is highest in April and lowest in July. Simulation results using different simulation tools have been compared and are shown to be in near agreement with the real calculated values. This plant set-up is expected to gain profit after a period of 5.9 years with a capacity to mitigate 136 tons of CO2 emission annually. Practical application: This study estimates the energy output, system losses and performance parameters for a 100 kWp rooftop grid connected solar photovoltaic system. This helps to check the feasibility of such a system at this location. Also the payback period and reduction in carbon footprint are calculated to highlight the economic and environmental benefits. This would attract public interest for installation of more such plants on rooftops of buildings in the near future.

Energetic and exergetic performance comparison of three solar cookers for developing countries

Three different domestic solar cookers are compared experimentally during water heating experiments using different loads. The solar cookers experimentally tested using energy and exergy thermal performance parameters are: a solar box cooker without a reflector, a solar box cooker with a reflector and a parabolic dish solar cooker. The rate of heat losses is more detrimental to the performance of the parabolic solar cooker since the cooking vessel is exposed more to the ambient weather conditions. Heat losses seem to have little effect on the performance of the solar box cookers. The solar box cooker with the reflector shows the highest average energy efficiencies, which increase with the water heating load. The parabolic solar cooker shows the lowest average energy efficiencies with the lower loads, which increase to be higher than those of the solar box cooker without the reflector at the higher loads. The solar box cooker with the reflector shows the highest average energy and exergy efficiency values, which are not dependent on the water load. The parabolic dish solar cooker shows average exergy efficiencies, which increase with the water heating load. The greatest cooking potential in terms of the speed of cooking is shown by parabolic dish solar cooker. The best overall thermal performance is shown with the solar box cooker with a reflector, but its cooking speed is rather slow when compared to the parabolic dish solar cooker. The solar box cooker without the reflector shows the worst thermal performance in most of the tested parameters except for the heat losses where it shows the lowest heat loss factors for all the experimental tests.

A study on the relationship between energy performance and IEQ parameters in school buildings

Over the last decades, strong focus has been placed on the energy efficiency of buildings; not least school buildings. Energy performance (EP) of buildings is nowadays in principle described by one single indicator based on purchased energy in kWh/year.m2. Another important building performance aspect is the indoor environmental quality. This study’s overarching goal is to identify school buildings with a good balance between energy performance and indoor environment. Thus, this paper investigates possible correlations between information given in energy performance certificates (EPCs/e.g. energy use, year of construction, type of ventilation) and measured indoor environmental parameters. The work comprises investigation of approximately 20 school buildings with different ventilation systems in Gothenburg. In-situ investigations of the buildings’ properties and ventilation systems were conducted. Indoor environmental parameters were recorded during one week in each classroom. In this paper, indoor temperature, absolute humidity added indoors and CO2 concentration data are compared with the corresponding school’s energy performance data and ventilation type. Results suggest that mechanically ventilated buildings have clearer relationships between energy performance, building indicators and measured indoor environment. For buildings such as naturally ventilated, the relationships are usually weak, and the values spread over much wider ranges.

An assessment of biomass torrefaction severity indexes

Previous studies have quantified the efficiency of biomass torrefaction processes by proposing severity indexes to discuss the variability of thermally modified biomass properties. However, comparisons of the accuracy and applicability of those indexes are few in the literature. To fill that gap, this study sought to assess five indexes usually applied in some torrefaction studies: weight loss, index of torrefaction, torrefaction severity index, severity factor, and torrefaction severity factor. These indexes were compared to characterize torrefaction under different conditions, and their accuracy in evaluating, correlating and predicting the physical, chemical and energetical properties of torrefied eucalyptus. As a result, the five evaluated indexes presented R2 > 0.84 andp-values ≤ 0.05 when evaluating basic properties. For all five indexes, there was a statistical significance when evaluating energy performance and R2 > 0.81. The three yield property-based indexes were more effective in predicting torrefied product properties and energy performance parameters. The two operating condition-based indexes were more effective in analyzing solid product properties than devolatilization. This work provided insight into which index is more appropriate for research and industrial applications.