Absorption Refrigeration System Research Articles

ABSORPTION REFRIGERATION SYSTEMS FOR WASTE HEAT RECOVERY AT THE SILICATE INDUSTRY

The glass, ceramic and cement plants are energy intensive industrial systems, releasing high amounts of greenhouse gases. The dissipation of the waste heat reduces their profitability, energy and ecological efficiency. The absorption refrigeration systems are successful solutions for the recovery of thermal energy at different temperature levels to obtain useful cooling and heating powers for technological needs, and for air conditioning of administrative and industrial buildings. Although the absorption units in a heat pump and refrigeration cycle are currently used in building and industrial systems, they have not yet penetrated widely into the silicate factories. This paper discusses possibilities for the applications of basic types of absorption cycles at heat pump and refrigeration modes to utilize waste energy at different temperature levels in glass, ceramic and cement plants. The examined variants are demonstrated via examples, diagrams and analyses of the possible energy saving.

Design of a hybrid solar and biomass-based energy system integrated with near-zero energy building: Techno-environment investigation and multicriteria optimization

The current research aims to meet the energy needs of a group of residential buildings in Norway with the least amount of carbon dioxide emission and the greatest amount of renewable energy. The supply side based on the renewable renewable-based energy system is planned and scaled using the real-time data use of domestic hot water (DHW), heating and electricity necessary for the buildings. PVT panels are used in the hybrid solar and biomass-based energy systems to produce both the DHW requirements and the electricity production. The digester is used with the heat pump, which generates heat. A double-effect absorption refrigeration system is also utilized to provide the necessary cooling requirements. On the supply side, the management of the heat streams and the redirection of flows are done using a rule-based regulating system. The whole plant's size is supplied, and the dynamic energy simulation is run. The primary deciding criteria for heating the buildings are the costs of electricity and biomass. The whole system is then optimized depending on operating circumstances, and the outcomes are compared to the design point. PVT may be used to create more than 80% of the yearly DHW. Furthermore, summertime radiation accounts for 64.8% of cooling output since it is more intense and may be converted into cooling energy. Digester/CC also contributes 66.55% of the building's heating, showing that the designers should rely on biomass as wintertime energy costs are higher. The parametric study demonstrates that increasing PVT time and tank capacity has varied effects on efficiency and emissions. Also, On winter days, there was a significant drop in renewable energy generation from summer to autumn, from 82.7 MWh to 28.52 MWh. The optimization results show that at the TOPSIS point, the total cost, efficiency, and emission index are 9.73 $/hr, 36.8%, and 7.75kg/MWh, respectively.

Evaluation of the Interconnection of a Biomethane Microturbine in an Absorption Refrigeration System

This article evaluates the performance and environmental impact of a combined system of natural gas microturbine and absorption refrigeration system. The objective of the study is to evaluate the interconnection of a biomethane microturbine in an absorption refrigeration system. The study applies energy and exergy balances to each component of the system, using EES software for the simulation. The microturbine is a Capstone C600s model with a nominal power of 600 kW, and the absorption chiller is a single-stage LiBr-H2O system with a cooling capacity of 680.7 kW. The results show that the microturbine achieves a thermal efficiency of 34%, an exergetic efficiency of 86%, and a net power output of 585.4 kW. At the same time the absorption chiller has a coefficient of performance (COP) of 0.7 and 680.7 kW with generator water temperature inlet of 100 °C. On the other hand, this study identifies the most efficient points of interconnection between the two systems. The combined system reduces the CO2 equivalent emissions by 700 to 900 tons/year compared to conventional systems. The behaviour of the interconnection heat exchanger is also evaluated using Computed Fluid Dynamics. The investigation concludes that the interconnection of a natural gas microturbine and an absorption refrigeration system is a promising alternative that can optimize both technical and economic aspects of energy generation and utilization, while mitigating environmental problems.

Review of Magnetization Impacts on Vapor Absorption Refrigeration Systems

Amidst the ongoing maintainable energy revolution, reducing energy consumption in vapor absorption refrigeration system (VARS) has become a critical application part. Over the past several decades, extensive research has been devoted to these systems. This study presents a thorough classification and review of the existing literature on magnetized refrigeration systems, specifically focusing on VARS. The paper explores the effects of magnetic fields on fluid flow interactions, categorizing the research into Electro-Hydrodynamics (EHD) and Magneto-Hydrodynamics (MHD). It highlights the distinctive impacts of magnetic fields on the thermophysical properties of electrically conducting fluids. Additionally, the article delves into the fundamental mechanisms behind the influence of magnetization on these properties. The review encompasses experimental studies conducted over the last two decades regarding the effects of magnetization on VARS.

Economic and technical optimization of a tri-generation setup integrating a partial evaporation Rankine cycle with an ejector-based refrigeration system using different solar collectors

Three collector types, namely parabolic trough solar collector (PTSC), linear Fresnel collector (LFC), and dish collector, are employed to drive a tri-generation configuration composed of a partial evaporation Rankine cycle (PERC), a hot water production unit (HWPU), and a cascade ejector-based compression refrigeration system (ECRS) for electricity, cooling, and heating production. The ECRS is integrated with the topping PERC through an absorption refrigeration system (ARS). Moreover, the collector is indirectly connected to the system by a storage tank to increase the operating hours of the system. The performance of the system is evaluated by thermodynamic and economic analysis. The three-objective optimization result is a testament to the fact that utilizing PTSC brings about the best performance of the system. The system exergy efficiency (ηex) in the case of PTSC is 8.1 % and 24.9 % higher than in the case of LFC and dish collector, respectively. The economic performance of the system in the case of PTSC is superior to that of the dish collector. Furthermore, the PTSC case results in a relatively similar economic performance to the LFC case. The system produces power, cooling, and heating at rates of 200.8 kW, 564.9 kW, and 795.7 kW in the optimum case of utilizing PTSC, respectively. Moreover, ηex, total cost rate (C˙tot), and specific cost of tri-generation (ctri) are obtained as 11.48 %, 204.7 $h−1, and 44.91 $GJ−1, correspondingly. The results indicate that ηex of the proposed layout in the case of PTSC is superior to a comparable tri-generation configuration introduced in the field by 2.78 % points.

Efficient waste heat utilization in high-temperature proton exchange membrane fuel cell bus through integration of lithium bromide absorption refrigeration

Compression-type air-conditioning heat pump systems used in high-temperature proton exchange membrane fuel cell (HT-PEMFC) buses significantly increase the vehicle's hydrogen consumption. This study introduces a lithium bromide (LiBr) absorption refrigeration air-conditioning system into a fuel cell bus, aiming to convert the high-quality waste heat produced by the HT-PEMFC into cooling and heating capabilities for balancing the temperature within the vehicle cabin and recover waste heat. Modeling and co-simulation of the HT-PEMFC, LiBr absorption refrigeration system, vehicle thermal model, and compression-type air-conditioning heat pump system were conducted using MATLAB/Simulink. The simulation results indicate that, compared with the traditional compression-type air-conditioning heat pump system, the LiBr absorption refrigeration system can save 6.13–18.17 % of hydrogen and improve the electrical energy and exergy efficiencies by 3.58–10.74 % and 3.74–11.22 %, respectively, under different driving scenarios. Using the LiBr absorption refrigeration system significantly enhances the vehicle's overall fuel utilization efficiency and driving range.

A data-and-knowledge-driven WNN modeling approach for the absorption refrigeration system

Given that the cooling capacity of the absorption refrigeration system depends on both the heat supply and the operating conditions, a data-and-knowledge-driven Wavelet Neural Network (WNN) modeling approach is proposed based on the analysis of its working principle and the coupling relationship between variables. This approach utilizes the Simple Particle Swarm Optimization (SPSO) algorithm instead of the gradient descent method to search the network parameters of WNN, which makes up for the defects of the gradient descent method that is easy to fall into the local optimum. Furthermore, the inequality constraints of energy and temperature are integrated into the loss function of model training as prior knowledge, and the model’s parameters are trained using experimental data, which reduces the training burden of the model and the model’s dependence on the training data, and increases the network’s interpretability and the model’s robustness. The experimental results show that the prediction accuracy and generalization of the WNN model are improved after replacing the optimization algorithm and incorporating the physical knowledge under the same working conditions, and its RMSE and MAE are reduced by 2.08% and 1.63%, respectively, compared with the original WNN model.

Performance analysis of sub-cooled transcritical CO2 refrigeration system using vapour absorption refrigeration system and dew point evaporative cooling

Shifting towards natural refrigerants is expected to reduce the environmental damage in terms of refrigerants leaks, as they have zero ozone depletion potential as well as minimal global warming potential. A CO2 transcritical cycle is analysed thermodynamically in this study. Further, to improve the performance of the CO2 system, a vapour absorption refrigeration system (driven by the heat available at the exit of the compressor) has been integrated with it. Also, to counter the effects of hot climatic conditions, in Indian context, a dew point evaporative cooling system is further utilized to take up the heat from the gas-cooler. A thermodynamic and economic study of the proposed integrated system is performed. The effect of various performance parameters; such as ambient dry bulb temperature, relative humidity, evaporator temperature has been studied on the overall performance of the system. Compared to the base case, the coefficient of performance is improved in the range of 40%–270 %, for the hybrid systems, under the different climatic conditions. Moreover, the proposed system provided a low-cost performance of about 0.024 $/kWh, as compared to the base case consumption of about 0.05 $/kWh.

Numerical analysis of multistage ultrasonic atomization enhanced ammonia-water falling film absorption

The absorption refrigeration system is a widely used system that utilizes waste heat and is environmentally friendly. However, many current systems still suffer from challenges such as large volume, and high initial investment. Meanwhile, optimizing the absorber is crucial for enhancing system performance as it is one of the main components. In this study, a novel absorber model is proposed and its influencing factors of performance are comprehensively analyzed. In this model, the traditional falling film absorber is divided into multiple stages, with an ultrasonic atomizer (UA) installed in each stage to enhance absorption. In each stage, falling film and atomization absorption occur simultaneously, and their outputs are combined and weighted at the exit to maintain continuous droplet absorption, effectively utilizing the entire absorber volume. In this process, the vapor–liquid contact area is increased through atomization, and simultaneously, generated heat is removed by the cooling water during mixing. As a result, the absorber’s absorption capacity increases, and the outlet solution temperature decreases. The results demonstrate that compared to the traditional falling film absorber, the proposed absorber, when divided into two stages with a droplet diameter of 50 μm and an atomization rate x = 0.7, shows a 60.64 % increase in ammonia absorbed rate. Additionally, compared to double-stage absorber, triple-stage absorber increases the ammonia absorption by 9.52 %. As the number of stages increased, the strengthening effect persisted, albeit with a gradually diminishing rate of increase. Scaling up to ten stages results in a 152.63 % absorption rate increase and a size optimization of 60.43 %. In this paper, multi-stage ultrasonic atomization is innovatively introduced into the falling film absorber, which enhances ammonia absorption and reduces the volume of the absorber. Additionally, the multi-stage atomization offers an innovative method to improve the droplet absorption process.

Research on Energy-Saving Control Strategies for Single-Effect Absorption Refrigeration Systems

The automatic control device is a critical component of absorption refrigeration systems. Its functional enhancement can reduce operating costs, improve energy efficiency, and ensure long-term stable unit operation. Given that absorption refrigeration systems operate under various dynamic conditions, the rational design of control strategies is particularly important. This study analyzes the influence of changes in the cooling water and heat source water flow rates on the outlet temperature of chilled water in the unit based on the open-loop response characteristics of absorption refrigeration systems. It proposes a dual-loop energy-saving control strategy for single-effect hot water lithium bromide absorption refrigeration systems based on the setpoint comprehensive optimization algorithm. Considering the multiple variables, strong coupling, large inertia, long time delay, and nonlinear characteristics of absorption refrigeration systems, as well as the difficulties in modeling these systems, this study applies a model-free adaptive control algorithm to the system’s control. It derives both SISO and MIMO model-free control algorithms with time-delay components. Through simulations comparing MFAC, improved MFAC, and traditional PID control, the dual-loop energy-saving control strategy is demonstrated to effectively reduce system heat consumption by approximately 20%, decrease power consumption by about 10%, and enhance the system’s SCOP by approximately 19.3%.

Development and assessment of an integrated multigenerational energy system with cobalt-chlorine hydrogen generation cycle

This study aims to develop and assess a new multigeneration system where nuclear heat is utilized as the energy source. The multigeneration system is further designed to generate power, cooling, freshwater and hydrogen. In the present multigeneration system, five main subsystems, including high-temperature gas-cooled pebble bed nuclear reactors, a Rankine cycle, a cobalt-chlorine thermochemical cycle, a multi-effect desalination system and an ammonia-water absorption refrigeration system are integrated for synchronized operation. The analyses of the present system are carried out with the approaches of energy and exergy. This integrated system uses a total of 1000 MW thermal energy that is obtained from four units of high-temperature gas-cooled pebble bed nuclear reactor. Using all the thermal energy that comes from the nuclear reactors, a total of 346.99 MW of electricity, a total of 1.59 MW of cooling, a total of 384.67 kg/s of freshwater, and a total of 0.25 kg/s of hydrogen are produced. The energetic and exergetic performance coefficients of the ammonia-water absorption refrigeration system are 0.74 and 0.83, respectively. While the energy efficiency for the overall system is calculated as 37.83%, the exergy efficiency is found to be higher as 46.32% with the multiple useful outputs which help exergetically improve the overall system.

Assessment of a solar-powered trigeneration plant integrated with thermal energy storage using phase change materials

This study presents a comprehensive thermodynamic assessment of a trigeneration plant producing electricity, fresh water through multi-effect desalination (MED), and cooling through an absorption refrigeration cycle. The MED and absorption refrigeration systems utilize the rejected heat from the power cycle, driven by concentrated solar power (CSP). Situated in Qatar, the present system leverages the abundant solar irradiance to optimize the efficiency of electricity generation, water desalination, and cooling. The design features parabolic trough collectors with synthetic oil as the heat transfer fluid, direct thermal storage, and a Rankine steam turbine cycle with three turbine stages. The system also incorporates phase change materials (PCMs) based thermal energy storage (TES) to improve the system performance and offset the mismatch between demand and supply. The present system evaluation is based on energy and exergy analyses, while the Aspen Plus is used to simulate the power production and desalination operations, providing detailed insights into its efficiency and potential for large-scale implementation. The proposed system operates with an energy efficiency of 56.72 % and an exergy efficiency of 31.24 %, respectively.

Parametric Based Techno‐Economic Evaluation for a Solar Thermal‐PV Integrated Multi‐Commodity Storage Facility

ABSTRACTPostharvest losses and spoilage of agricultural products are a major problem for tropical countries, and it is even more challenging for countries encountering fluctuating power shortages, such as Pakistan. Therefore, this study focused on the energy and economic analysis of cold storage to store three products (potatoes, pomegranates, and potatoes) according to the season and storage span throughout the year. The cooling load of the cold store was supported by a LiBr‐H2O vapor absorption and vapor compression refrigeration system to maintain the desired temperature for each product during cold storage. A solar thermal PV system is installed to operate cold storage refrigeration systems. Cold storage performance was analyzed by developing thermal models of integrated systems using the ambient conditions of Lahore, Pakistan. A parametric study was also conducted to analyze the impact of various working parameters on integrated system performance, and it was found that the maximum peak cooling load of 91 kW inside cold storage is attributed to pomegranates owing to high ambient conditions during its loading month. The product loading rate significantly affects the cooling load of cold storage and varies directly with it, as observed for an increase in the product loading rate from 0 to 50 000 kg/day cooling load also increases from 34 to 87 kW. To meet the thermal demand of the generator of the vapor absorption system, parabolic troughs were installed to operate cold storage, and it was found that a minimum of four PTC were needed to support the peak cooling load at the maximum product loading rate and minimum DNI value. To meet the electrical demand of cold storage electrical equipment and the compressor of the vapor compression system, solar photovoltaic panels were installed, and it was found that a minimum of 618 panels was required at a minimum tilted radiation value. To validate the viability of proposed design system economic analysis was also conducted which revealed a payback period of 12 years for Kinnow and potatoes and 16 years for pomegranates.

Thermodynamic characteristics of a novel solar single and double effect absorption refrigeration cycle

Solar absorption refrigeration systems provide one of the economical options for air conditioning. In order to reduce the complexity and economic cost, a more advanced solar single-double-effect switching system is proposed. The innovation of this system is that it replaces the single-effect and high-pressure generators in previously developed single-double-effect switching system with a specific generator. The optimal heat source switching temperature of the new system was determined by the genetic algorithm to be 125.5 °C. Compared with the original single-double-effect switching system, the average coefficient of performance of the system is increased by 8.6 %, and the fluctuation of refrigeration capacity during the switching period is reduced by 48 %. The new solar single-double-effect switching system is investigated based on thermodynamic characteristics, energy, exergy, and economy aspects. The results showed that heat exchangers of the system have strong coupling. The cooling water temperature has a greater impact on the performance of the dual-effect mode. In the single-effect mode, the special-pressure generator has the largest exergy destruction (39 %), while in the double-effect mode, the absorber has the largest exergy destruction (41 %). Besides, the economic analysis demonstrated that the new system is economically viable with a payback period of 9.33 years.

Enhancing thermodynamic performance with an advanced combined power and refrigeration cycle with dual LNG cold energy utilization

Utilizing waste heat to drive thermodynamic systems is imperative for improving energy efficiency, thereby improving sustainability. A combined cooling and power systems (CCP) utilizes heat from a temperature source to deliver both power and cooling. However, CCP systems utilizing LNG cold energy suffers from low second law efficiency due to significant temperature differences. To address this, an “Advanced Power and Cooling with LNG Utilization (ACPLU)” system is proposed, integrating a cascaded transcritical carbon dioxide (TCO2)-LNG cycle with an Organic Rankine cycle (ORC) for improved power generation and an absorption refrigeration system (ARS) for simultaneous cooling. This study evaluates the second law efficiency, net work output, and exergy destruction performance through a sensitivity analysis, optimizing variables such as heat source temperature, superheater temperature difference, ORC and CO2 turbine inlet and condenser pressures, evaporator temperature, and pinch point temperatures of heat exchangers and generator. Compared to previous studies on CCP systems, the ACPLU shows a superior performance, with a second law efficiency of 27.3 % and a net work output of 11.76 MW. Cyclopentane as an ORC working fluid resulted in the highest second law efficiency of 29.06 % and net work output of 12.27 MW. Parametric analysis suggested that heat source temperature significantly impacts net power output. The exergy analysis concluded that a high-pressure ratio and good thermal match between the heat exchangers enhance overall performance. Utilizing artificial neural network (ANN) to produce a multiple-input-multiple-output (MIMO) objective function and performing multi-objective optimization (MOO) using genetic algorithm (GA), an improved second law efficiency and net power output by 28.11 % and 14.16 MW respectively, with pentane as the working fluid, is demonstrated. An average cost rate of 9.121 $/GJ was observed through a thermo-economic analysis. The ACPLU system is promising for medium temperature waste heat recovery, such as, pharmaceutical manufacturing plants.

Energy, exergy, economic, and environmental compromising performance of dual-stage evaporation-ammonia hybrid compression–absorption refrigeration system for the cooling supply of keto-benzene dewaxing process

Absorption refrigeration systems driven by low-temperature waste heat is one way to achieve “carbon neutrality”. Meanwhile, the keto-benzene dewaxing equipment needs cooling capacity of 5 MW which refrigeration temperature of –10 °C and –25 °C. This paper researches the feasibility of DSE-AHCARS (Dual-stage Evaporation-Ammonia Hybrid Compression-Absorption Refrigeration System) replacing the vapor compression refrigeration system for keto-benzene dewaxing process based on 4E (Energy, Exergy, Economic, and Environmental) analysis. At the primary and secondary stage evaporation temperature of 0 and –23 °C, COP reaches the maximum value of 0.85. However, COP-Electricity reaches the minimum value of 8.1. When the secondary stage refrigeration temperature is –23 °C, CO2 emission increases from 1150 t·a–1 to 3600 t·a–1, and Life Cycle Climate Performance increases from 3.29×104 tons to 7.7×104 tons with the primary stage refrigeration temperature is –15 °C to 0 °C. As well as matching three parameters to ensure the 4E compromising performance by the multi-objective optimization. To guarantee the Life Cycle Climate Performance is less than 5.5×104 tons, the payback period is less than 2 yr, and COP is greater than 0.6 at the optimal operation ranges that refrigeration temperature difference between primary stage and secondary stage is within 20 °C. The power of DSE-AHCARS was reduced by 77% compared with the vapor compression refrigeration system. Therefore, the DSE-AHCARS can reduce CO2 emissions by about 6250 t·a–1 and save 1.2×105 tons of CO2 in the Life Cycle Climate Performance term. This result shows that the DSE-AHCARS can completely replace the vapor compression refrigeration system.

Performance Evaluation of Novel Advanced Recompression Absorption Refrigeration Systems Equipped with Ejector and Vapor Injection Technology

The absorption refrigeration cycle (ARC) faces challenges considering its decreased working pressure and COP. By integrating Recompression technology (RAC) into ARC, these issues are partly addressed. To address these inefficiencies, in this study, ejector and vapor injection techniques are incorporated into refrigerant side of the RAC cycle, resulting in the development of advanced systems: Refrigerant ejector enhanced recompression absorption cycle (RE-RAC) and Vapor injection enhanced recompression absorption cycle (VI-RAC). Key metrics assessed are 1st and 2nd law efficiency, system exergy destruction rate, compressor load, and generator heat requirements. Conclusively, under analogous operating conditions, RE-RAC and VI-RAC demonstrate a substantial improvement in COP, achieving 76 % and 63 % enhancements, respectively, over the standard RAC system. Compared to the conventional solution ejector-based SE-RAC, these systems show performance increases of 28 % and 19 %, respectively. The findings also highlight the sensitivity of these systems to parameters such as generator temperature and pressure, evaporator temperature, absorber temperature, evaporator recovery and normal pressure ratio. At higher evaporator temperature and lower generator temperature, the performance of these systems as well as enhancement of RE-RAC over VI-RAC is higher observed. The optimal value of generator pressure and recovery pressure ratio for maximum efficiency and minimum total exergy destruction rate is also dependent upon these. At a generator temperature of 67 °C and an evaporator temperature of 8 °C, RE-RAC exhibits a 35 % higher COP compared to VI-RAC. However, at −10 °C evaporator temperature, changes in external generator heat input and compressor work reduce the COP enhancement to 5 %.

Innovative research on hybrid absorption refrigeration system with complementary solar energy and waste heat

Innovative research on hybrid absorption refrigeration system with complementary solar energy and waste heat

Game theoretic approach for the synthesis and optimization of economically optimal coalitions in integrated renewable energy and polygeneration networks

This study presents the generation of an integrated resource network that encompasses a bioenergy supply chain and a polygeneration hub. The resource network is designed using a superstructure that comprises 3 layers. The first layer is a supply chain network of seasonally available renewable and non-renewable energy sources and is connected to the second layer by a transport system comprised of rail, road, and pipeline. The second layer, which is the polygeneration hub, comprises a boiler to produce high-pressure steam, steam turbines for generating power, a multi-effect evaporation system for desalinating salt-water and an absorption refrigeration system to produce chilled water. The option of connecting the boiler to a solar-thermal and heat storage subnetwork for feedwater pre-heating is included in the second layer. Piping and electrical cables connect the polygeneration layer to the third layer, which comprises industrial heat demand, represented by heat exchanger network, and electrical power demand. The model is applied to a case study in which the subnetworks in the overall integrated superstructure layers are considered as individual players in an industrial symbioses network with the possibility to be in a cooperative game. The objective function of the model, which is represented as a mixed integer nonlinear programming model, involves the minimization of the summation of the players' marginal contribution, with equal weighting applied for each player, to the coalition's total annual cost. The result obtained involves preference for a coalition among participating subnetworks that include combined heat and power, multi-effect evaporation, and heat exchanger network.

Hybrid air conditioning and seawater desalination system assisted by solar energy: thermoeconomic investigation and optimization

The demand for freshwater has become progressively critical due to population growth and water scarcity. The current work investigates the energetic performance of a hybrid absorption refrigeration and desalination system. A parametric study for the system operating conditions has been performed to get the optimal conditions. Also, economic analysis and a multi-objective optimization method are used with the aim of maximizing the energy utilization factor of the system and minimizing total costs. The specific cost of desalinated water from the multi-objective optimization is calculated as (1.728 Cent/L) with the greatest energy utilization factor of (2.214). It turns out that, the system performs optimum at condensation and generation temperatures of 30 and 65 °C respectively, with resultant COP and GOR of 0.84 and 1.37. Using the optimum conditions, TRNSYS has been used to investigate the transient performance of the system for Marsa–Matrouh City in Egypt. The cooling and freshwater demands are 10 kW and 24 L/h. It was concluded that the input energy required to run the hybrid system decreased by about 65% less than that required for separate systems. With the assistance of solar energy, it became clear that the energy required was 60% less than the hybrid system as well.