Integrated Approach for Energy Conservation and Efficiency Enhancement of Cooling and Air Conditions in Industrial Operations: A Sustainable Design for Yemen

When they were first conceived, solar cooling systems were designed to be cost-effective and environmentally safe alternatives for the majority of the developing nations that are characterised by their hot climates in contrast with the traditional air conditioning systems powered by electricity that is produced from fossil fuel resources. Nevertheless, developments in photovoltaic (PV) and air-conditioning technologies have impacted on the prospects of solar cooling systems. This study examined two different options: a coupled PV and air conditioner system and a solar cooling system (absorption chillers where thermal energy is provided by solar collectors) for a specific developing country located in the Eastern Mediterranean region whose climate is hot and dry (Jordan). The cooling system comprised a pair of cooled multistage compression, both of which were 700 kW, while the PV system’s size was 2.1 MWp, the utility grid connection was a 0.4 kV 50 Hz net meter (2 m) and it was anticipated that 3300 MWh/year would be generated. The solar cooling system operated at a maximum coefficient of performance (COP) of 0.79 and had an actual recorded COP of 0.32 on the site; when the electricity tariff of $0.1/kWh was considered, the respective levelised cost of energy (LCOE) values were $0.9/kWh and $2.35/kWh respectively. The findings indicate that the initial costs for the solar thermal cooling system and the PV system were approximately $3.150M and $3M, respectively. The current value of future cash payments when discounts of 6% per year were applied to the payments for the combination of PV and air conditioning was about $9,745,000, whereas the solar thermal cooling system will not reach the breakeven point at negative $1,730,000. It is clear the absorption chiller did not display economic feasibility, whereas the value for the coupled PV and air-conditioning systems was under $0.05/kWh. In addition to the extensive maintenance needs, the reduced COP and the practicality and feasibility of the solar thermal cooling systems mean these kinds of technologies are under significant pressure to remain competitive when faced with the development of new air conditioning and PV technologies.

The variable refrigerant flow (VRF) air conditioning systems have been widely used to home air conditioner. The VRF system can provide variable refrigerant flow by changing the speed of compressor for energy saving and more comfortable air conditions. Recent years, the energy saving technique for central air condition system becomes important, and the inverter applied as variable frequency drive control the speed of compressor motor technologies have been applied to central air conditioning systems. The central air conditioning system with the inverter compressor (ICCACS) providing variable refrigerant flow becomes an important solution for energy saving. This study built the central air conditioning systems dynamic model with operation data. The appropriate refrigerant flow is calculated by refrigerating capacity. A PI controller is designed to control the speed of compressor for keeping the temperature of chilled water in command temperature. The energy consumption is investigated under transient and steady processes.

This study presents a comprehensive analysis of the energy efficiency and sustainability of Variable Refrigerant Flow (VRF) systems in university buildings during the winter season, offering significant contributions to the field. A novel methodology is introduced to accurately assess the real Seasonal Coefficient of Performance (SCOP) of VRF systems, benchmarked against conventional Heating, Ventilation, and Air Conditioning (HVAC) technologies, such as natural gas-fueled boiler systems. The findings demonstrate outstanding seasonal energy performance, with the VRF system achieving a SCOP of 5.349, resulting in substantial energy savings and enhanced sustainability. Key outcomes include a 67% reduction in primary energy consumption and a 79% decrease in greenhouse gas emissions per square meter when compared to traditional boiler systems. Furthermore, VRF systems meet 83% of the building’s energy demand through renewable energy sources, exceeding the regulatory SCOP threshold of 2.5. These results underscore the transformative potential of VRF systems in achieving nearly Zero-Energy Building (nZEB) objectives, illustrating their ability to exceed stringent sustainability standards. The research emphasizes the strategic importance of adopting advanced HVAC solutions, particularly in regions with high heating demands, such as those characterized by continental climates. VRF systems emerge as a superior alternative, optimizing energy consumption while significantly reducing the environmental footprint of buildings. By contributing to global sustainable development and climate change mitigation efforts, this study advocates for the widespread adoption of VRF systems, positioning them as a critical component in the transition toward a sustainable, zero-energy building future.

Variable Refrigerant Flow (VRF) systems are becoming increasingly popular in commercial and residential buildings due to their flexibility and efficiency. Building design and operational parameters play an important role in the process of predicting cooling loads, and these variables contain a variety of uncertainties that must be taken into account when seeking to obtain a reliable prediction. It is common practice to oversize the Heating, Ventilation, and Air Conditioning (HVAC) system installed in a building in order to reduce uncertainties in its performance. However, oversizing is undesirable due to additional capital and operating costs, inefficient space utilization, and excessive emissions of greenhouse gases. This study provided a comprehensive literature review on previous uncertainly analysis studies from six perspectives: classification of uncertainty factors, sensitivity analysis methods, building energy model for uncertainty analysis, sampling method, the most effective parameter, and distribution of uncertainty parameters., and then developed a framework to investigate the effects of uncertainty of operational and design parameters on annual cooling load, total energy consumption, HVAC electricity use per conditioned floor area, VRF system cost, and the cooling-to-total electricity consumption ratio (R) in residential buildings equipped with VRF systems located in the Middle East (ME) region (Kuwait City, Tehran, and Istanbul). Artificial Neural Network (ANN) model was also developed to predict output parameters in residential building. Latin Hypercube Sampling (LHS) simulation was also applied to generate near-random samples of uncertainty parameter values from a multidimensional distribution. It should be mentioned that a correlation was derived in this study to predict VRF cost. The study evaluated thirteen uncertainty parameters related to building characteristics, occupants, building energy systems, VRF variables, and lighting conditions. Several methods were used to evaluate the effects of input uncertainty parameters on the output variables, namely, the Standardized Regression Coefficient (SRC), Partial Correlation Coefficient (PCC), and Spearman Rank Correlation Coefficient (SRCC) or Pearson Product-Moment Correlation Coefficient (PPMCC). The results indicated that VRF cost and HVAC electricity use per area have a greater coefficient of variation compared with other output parameters. The density distribution of output parameters indicated that uncertainty parameters had the greatest impact on output parameters in Kuwait (hyper arid climate), whereas in Istanbul (humid subtropical climate), they were the least. Among the variables examined in the Sensitivity Analysis (SA), cooling setpoint had the greatest impact on residential building energy consumption in ME climates. Finally, this paper highlights emerging trends and offers recommendations for advancing future research in the realm of building energy uncertainty analysis.

Feasibility assessment of adopting distributed solar photovoltaics and phase change materials in multifamily residential buildings

Abnormal energy identification of variable refrigerant flow air-conditioning systems based on data mining techniques

Experimental evaluation and simulation of a variable refrigerant- flow (VRF) air-conditioning system with outdoor air processing unit

Integrating solar PV systems for energy efficiency in portable cabins: A case study in Kuwait

Variable refrigerant flow (VRF) air conditioning system has developed into multi-module outdoor units with inverter compressor installed in each module, in which the compressor operating frequencies are undetermined. In this paper, the performance of VRF air conditioning system with two parallel outdoor units is studied, and the capacity allocation strategy for parallel outdoor units is proposed. Firstly, models including compressor, heat exchanger, expansion valve and VRF air conditioning system with multi-module outdoor units were described mathematically. Then, the VRF air conditioning system with two parallel outdoor units operating in a certain frequency range were simulated in nominal cooling condition, in the cases of two identical parallel outdoor units and two different parallel outdoor units. The results indicate that a highest efficiency can be achieved at the frequency ratio region of 0.9~1.0 in the case of identical parallel outdoor units, while the most efficient frequency ratio region is 1.1~1.3 in the case of different parallel outdoor units. Finally, a capacity allocation strategy of compressor speed synchronization for multi-module outdoor units is proposed from the aspect of highest efficiency of VRF air conditioning system.

Net-zero energy homes (NZEHs) have been studied widely from different perspectives to provide realistic and practical solutions. Among various approaches to enable NZEH designs, energy-efficient heating, ventilation, and air-conditioning (HVAC) systems play a key role in providing thermal comfort and good air quality in a cost- and energy-efficient manner. This study proposes a NZEH design using photovoltaic (PV)-based distributed energy generation and multi-functional variable refrigerant flow (VRF) systems with electric and thermal energy storage systems. Simulation-based NZEH performance evaluation is conducted based on case studies under various US climate conditions. To develop a validated NZEH simulation model, the net-zero energy residential test facility (NZERTF) constructed by the US National Institute of Standards and Technology (NIST) is used for benchmarking the NZEH reference model. Changes in monthly energy consumption and on-site power generation before and after the VRF application are analyzed to capture the potential impact of the VRF system application for the NZEH design. This study shows that the alternative NZEH design with the proposed VRF and electric and thermal energy storage systems can achieve around 13% through 32% of cooling energy reductions under different US climate conditions. With the proposed VRF system, the savings potential of domestic hot water energy consumption is significant up to 90% reduction compared to the original NZEH before the proposed VRF and energy storage systems were considered.

The growing demand for the primary energy and the associated environmental issues globally, have led to the progress in energy conservative approaches in the recent years. From the standpoint of confronting the energy challenges in buildings, the development of energy efficient systems and energy conservative technologies is becoming increasingly important for satisfying the end-user requirements. In the class of highly energy efficient systems, the variable refrigerant flow (VRF) or the variable refrigerant volume (VRV) system has been developed to meet out the cooling and heating requirements in buildings. VRF/VRV system, basically operate through the modulation of the refrigerant flow according to the energy demand in buildings. In recent years, the amalgamation of control systems in heating, ventilation, air conditioning and refrigeration (HVAC&R) research has provided the impetus for the development of VRF systems with enhanced energy efficiency and energy savings potential for building applications. This chapter primarily aims at reviewing the potential research studies emphasizing the importance of VRF cooling and heating systems dedicated for achieving enhanced energy efficiency and energy conservation in buildings. In the spectrum of VRF systems, the technical revelations pertaining to the refrigerant flow characteristics, single-loop and multi-loop units and combined/hybrid VRF systems with advanced intelligent controllers have been reviewed from a variety of research studies reported in the literature. Furthermore, the roles of key governing aspects which greatly influences the operational performance and feasibility of the VRF/VRV systems integration for modern buildings have been addressed and signified.

Comparative analysis of the energy efficiency of air-conditioner and variable refrigerant flow systems in residential buildings in the Yangtze River region

The integration of photovoltaic (PV) systems in buildings shows several advantages compared to conventional PV power plants. The main objectives of the present study are the quantitative evaluation of the benefits of building-integrated PV systems over their entire life-cycle and the identification of best solutions to maximize their energy efficiency and CO2 mitigation potential. In order to achieve these objectives, a simplified life-cycle analysis (LCA) has been carried out. Firstly, a number of existing applications have been studied. Secondly, a parametric analysis of possible improvements in the balance-of-system (BOS) has been developed. Finally, the two steps have been combined with the analysis of crystalline silicon technologies. Results are reported in terms of several indicators: energy pay-back time, CO2 yield and specific CO2 emissions. The indicators show that the integration of PV systems in buildings clearly increases the environmental benefits of present PV technology. These benefits will further increase with future PV technologies. Future optimized PV roof-integrated systems are expected to have an energy pay-back time of around 1·5 years (1 year with heat recovery) and to save during their lifetime more than 20 times the amount of CO2 emitted during their manufacturing (34 times with heat recovery). © 1998 John Wiley & Sons, Ltd.

The integration of photovoltaic (PV) systems in buildings shows several advantages compared to conventional PV power plants. The main objectives of the present study are the quantitative evaluation of the benefits of building-integrated PV systems over their entire life-cycle and the identification of best solutions to maximize their energy efficiency and CO2 mitigation potential. In order to achieve these objectives, a simplified life-cycle analysis (LCA) has been carried out. Firstly, a number of existing applications have been studied. Secondly, a parametric analysis of possible improvements in the balance-of-system (BOS) has been developed. Finally, the two steps have been combined with the analysis of crystalline silicon technologies. Results are reported in terms of several indicators: energy pay-back time, CO2 yield and specific CO2 emissions. The indicators show that the integration of PV systems in buildings clearly increases the environmental benefits of present PV technology. These benefits will further increase with future PV technologies. Future optimized PV roof-integrated systems are expected to have an energy pay-back time of around 1·5 years (1 year with heat recovery) and to save during their lifetime more than 20 times the amount of CO2 emitted during their manufacturing (34 times with heat recovery). © 1998 John Wiley & Sons, Ltd.

Improved solar milk chilling system using variable refrigerant flow technology (VRF)