Life Cycle Climate Performance Research Articles

Internal Heat Exchanger Influence in Operational Cost and Environmental Impact of an Experimental Installation Using Low GWP Refrigerant for HVAC Conditions

The use of an internal heat exchanger in vapor compression refrigeration systems of one stage is a common practice because it helps to increase the cooling capacity in the evaporator. Furthermore, the use of refrigerants with low global warming potential is becoming more frequent due to environmental regulations worldwide. Thus, this paper presents an evaluation of the improvement produced by the inclusion of an internal heat exchanger cycle (IHXC) in an experimental installation from the viewpoint of exergy, economic and environmental through to exergy, exergoeconomics, and Specific Life Cycle Climate Performance (SLCCP) studies. The tests were conducted using R1234ze(E) as a replacement alternative to R134a in three evaporating temperature conditions: 4 °C, 9 °C, and 14 °C. Comparisons were made considering R134a in BRC mode versus R1234ze(E) in BRC and IHXC modes. Results show that a lower environmental impact is produced by an evaporating temperature of 14 °C with a reduction in SLCCP of 13.3% using IHXC and R1234ze(E). Moreover, the highest increase in exergy efficiency was observed for an evaporating temperature of 4 °C, with this increase being 9%, while the lowest increase in the total cost rate was observed for the same evaporating temperature, being 12.3% and 21.2% for BRC and IHXC modes using R1234ze(E), respectively.

Economic and environmental analysis of ground source heat pump system according to operation methods

A ground source heat pump (GSHP) system can achieve high energy performance than conventional air source heat pump system by using annual stable underground temperature. However, the GSHP system can occurred soil thermal imbalance when the system is used for a long-term operation. Therefore, in order to prevent soil thermal imbalance, increasing the spacing and depth of boreholes and combining GSHP system with auxiliary heat sources are used. However, these methods require large sites and high initial investment. This study proposes an intermittent operation as an alternative to minimize the imbalance by altering the GSHP system. A numerical simulation model that can simultaneously analyze mass and heat transfer in soils was used to accurately analyze the performance of the GSHP system. In addition, the economic analysis and life cycle climate performance (LCCP) were compared based on the numerical analysis results of the GSHP system. Consequently, an appropriate operation method for the system is proposed by comprehensively considering the analysis results for the performance, economics, and environmental impact of the GSHP system according to the operation method. The numerical analysis of the GSHP system showed that the intermittent operation method increased the heat exchange rate of the GSHP system by 15%, compared to the continuous operation method, and the borehole center temperature was higher by 0.8 °C when the system operation concluded. Moreover, the economic analysis results showed that the intermittent operation method could reduce the total cost by up to 18.7% (1,921 USD) compared to the continuous operation method because it can dramatically reduce the initial investment cost. However, as the result of the LCCP analysis for three months, the total emissions increased by up to 11.8% (793 kg CO2e) because the intermittent operation method has a higher energy consumption of the heat pump than the continuous operation method.

Comparative Analysis on the Life Cycle Climate Performance of Ground Source Heat Pump Using Alternative Refrigerants

Comparative Analysis on the Life Cycle Climate Performance of Ground Source Heat Pump Using Alternative Refrigerants

Life Cycle Climate Performance Evaluation of Electric Vehicle Thermal Management System Under Chinese Climate and Driving Condition

Life Cycle Climate Performance Evaluation of Electric Vehicle Thermal Management System Under Chinese Climate and Driving Condition

Performance, economic and environmental assessment of solar cooling systems under various climates

Solar cooling systems are gaining more attention as eco-friendly cooling technology, which could be an alternative to the conventional vapor compression cooling one to meet the growing demand of space cooling. This paper proposes the investigation of different solar cooling systems, namely: solar absorption, solar adsorption, photovoltaic and photovoltaic thermal cooling systems on the basis of performance, economic and environmental aspects. The main objective is to identify the most favorable system depending on climate condition and solar fraction. Moreover, a numerical simulation is performed on EnergyPlus software to determine the cooling loads of a typical office building for air-conditioning purpose. Performance, economic and environmental analyses are carried out in terms of key indicators, such as solar coefficient of performance (SCOP), levelized cost of cooling (LCOC), discounted payback period (DPP), and life cycle climate performance (LCCP).The results showed that the increase of solar fraction impacts positively the economic and environmental indicators, since this could reduce the LCOC, DPP and LCCP values. Besides, the photovoltaic thermal cooling system exhibits the better performance in all climate conditions with SCOP values ranging from 36% to 52%, depending on climate. Furthermore, the economic findings revealed that the lowest values of LCOC are acquired by using photovoltaic cooling system; varying within the range of 0.056–0.25 €/kWhc, depending on climate. While the lowest DPP values are observed in regions with high solar irradiation using photovoltaic cooling system. Moreover, solar adsorption cooling system was found to be the most environmentally-friendly since it exhibits the lowest LCCP value. In addition, it was found that the increase of ambient temperature and solar radiation results in higher SCOP and lower LCOC and DPP values, especially for solar absorption and solar adsorption cooling systems. The current work is expected to serve as a reference for engineers and designers to select the suitable solar cooling system to be installed according to the target location and solar fraction.

Techno-economic and environmental analysis of low-GWP alternative refrigerants in cold storage unit under year-round working conditions

The impact of refrigerants with high global warming potential (GWP) on climate change necessitates the use of alternative refrigerants in cold storage systems. Designed cold storage units using low-GWP alternative refrigerants to R404A, i.e., R407A and R407F, are experimentally studied respectively in this study under year-round working conditions (ambient temperature of 32, 25, 15 and 5 °C). The year-round performance of the units in terms of energy saving and safety under three super-heating degrees (SHs) are also investigated. In each working condition, the performance of cold storage unit using R404A, R407A and R407F is compared in terms of the cooling capacity, energy efficiency ratio, sub-cooling degree, condensing temperature, evaporating temperature and discharge temperature (Td). The results show that the annual energy effect ratio of the unit with R407A and R407F is higher than that of R404A, however the Td of R407F is at an unfavorable level for safety at high ambient temperatures. The annual power consumption, life-cycle cost, total equivalent warming impact and life cycle climate performance of R407A are lower than those of R404A by 2.5%, 2.2%, 7.9% and 7.9%, respectively, and those of R407F are lower than those of R404A by 4.6%, 4.2%, 11% and 14.5%, respectively, indicating R407F is a better low-GWP alternative refrigerant for cold storage systems.

Performance assessment of an R32 commercial heat pump water heater in different climates

This study evaluates the performance of a heat pump water heater (HPWH) that uses low-global warming refrigerant in several climatic conditions. The performance assessment methodology adopted was based on the development and validation of a numerical simulator for the assessment of the performance of HPWH. The validation was achieved with dedicated experiments with a commercial R32 HPWH based on considerations of different climatic conditions, such as tropical climates, and summer, interim, and winter seasons, representative of temperate climates. The recorded deviations between the experimental and simulation for several system characterization were below 3%. The different climatic conditions were represented in terms of air temperature, humidity, and inlet water temperature. The influences of the climate on the system characterization is discussed based on experiments and simulations and based on the assessments of the temperature achievement, power consumption, P–h diagram, heating capacity, COP, and life-cycle climate performance (LCCP). The assessment results show that the system operation in the representative condition of a tropical climate yields the highest COP (approximately equal to 5.4) and according to the LCCP assessment, the lowest CO2 emissions.

A comprehensive review of life cycle climate performance (LCCP) for air conditioning systems

Life Cycle Climate Performance (LCCP) is a widely accepted metric to evaluate the carbon footprint of air conditioning (AC) systems “from cradle to grave.” This paper: (1) reviews the invention and evolution of LCCP, including a comprehensive timeline and bibliography; (2) documents the successful application of LCCP in the replacement of HFC-410A with HFC-32 in room air conditioners; (3) compares the conceptual frameworks and the operational approaches; and 4) reflects on the drawbacks of current LCCP research and points out possible future work. The major policy-relevant findings are: 1. The indirect emissions caused by energy consumption is 70 to 80 percent of the LCCP of AC systems in most countries but will decline in importance as electric power supply shifts rapidly from fossil fuel to renewable energy sources, which have near-zero carbon intensity; 2. The embodied greenhouse gas (GHG) emissions in refrigerant manufacture are, in most cases, negligible but the physical and chemical properties are crucial for system optimization for low carbon footprint; 3. The LCCP metric can be used for multiple purposes such as refrigerant selection and AC system architecture optimization; and 4. Data limitations in material manufacturing and the carbon intensity of electric power are the most significant challenges. Finally, this paper describes a variety of methods to fill in data gaps, including the correction factor method , the data-driven method , and the database searching method . The next-generation LCCP will be an enhanced evaluation process considering local climate, heat islands, and local power supply characteristics.

Comprehensive investigations on Life Cycle Climate Performance of unitary air-conditioners

Life Cycle Climate Performance (LCCP) evaluation of air conditioning systems helps to mitigate the carbon emissions from the rapidly expanding air conditioning systems. Nevertheless, different counties have different system evaluation standards, weather conditions, grid emission factors, and material carbon emission coefficients. Furthermore, new R-410A alternatives like R-466A were rarely discussed. Besides, some researchers used the weather station data instead of onsite weather data. However, the weather data collected from the UMDCP campus and the College Park airport in the USA were different up to 5 °C due to the heat island effect. This paper used a unitary air conditioner as a case study and compared the LCCP calculation results for 11 cities worldwide for five different refrigerants. As excellent candidates for replacing R-410A from the LCCP perspective, R-32, R-290, R-452B, and R-466A are considered in this study. Then, the results using field test data and weather station data were compared. In conclusion, annual energy consumption is a significant factor in high-emission-factor countries. In some low-emission-factor countries, the LCCP can be decreased by up to 60% by using R-290. The differences between the actual inlet air temperature to the outdoor unit and local weather station measured temperature can result in up to an 8% difference in LCCP. For future work, more works on futuristic assumptions for grid emission factors and variable speed systems are needed while considering the expansion of renewable energies and energy efficient variable speed systems.

Thermal-economic-environmental analysis on household refrigerator using a variable displacement compressor and low-GWP refrigerants

Abstract Variable displacement compressor technology can achieve high steady-state efficiency, non-start/off operation thus high seasonal efficiency and capacity modulation. A comprehensive thermal-economic-environmental analysis of a household refrigerator with variable displacement compressor using three refrigerants (R134a, R152a and R1234yf) was presented using CoP and normalized CoP, set-up and running cost and Life Cycle Climate Performance, respectively. The results indicate that with the application of variable displacement technology, the compressor stroke can be tuned in response to heat load so that the power consumption is reduced thus the running cost and CO2 emissions. When the compressor stroke using R134a drops from 13 mm to 10 mm, the power consumption, total cost and life cycle CO2 emissions decrease by 86.3%, 56.7% and 59.9%, respectively. Running cost accounts for 89% of the total cost while indirect emissions accounts for 98% of the total CO2 emissions. Replacement of R134a by R152a will decrease the CoP by 10% but also reduce the cost and CO2 emissions by 5% and 8.6% respectively. This is comparable to increasing the R134a system CoP by 0.9. It is indicated that by adopting variable displacement technology, more CO2 emissions could be reduced given that part load represents over 80% of operating hours for refrigerators.

Environmental effect evaluation of refrigerator cycle with life cycle climate performance

In this study, a method to evaluate the environmental effects of household refrigerators is newly developed in terms of life cycle climate performance (LCCP). The energy consumption model of the refrigerator is developed with three types of typical single evaporator refrigerators. The operation ratio of the evaporators, which is critical for calculating the energy consumption of dual evaporator refrigerators, is determined using experimental results of serial, bypass, and parallel-circuit cycle refrigerators. The LCCP results show that the system performance and equipment manufacturing emissions are dominant factors in lifetime CO2 emissions. Therefore, energy- and material-related factors, such as refrigerator cycle options, refrigerator material, insulation, and power sources, are primarily investigated. For cycle options, CO2 emissions can be reduced by 14.7% using a two-stage cycle. For condenser materials, CO2 emissions can be reduced by 2% to 2.5% using aluminum instead of steel. For insulation, the total emissions can be reduced by up to 7.7% by applying vacuum insulation panels on each side of the refrigerator. When 20% renewable energy is supplied, the total emissions are expected to be reduced by 13% in the baseline, 19.9% in the parallel-circuit cycle, and 26% in the two-stage cycle.

The life cycle climate performance evaluation of low-GWP refrigerants for domestic heat pumps

Abstract Domestic heat pumps constitute a significant part of the global heat pump industry. R401A offers excellent performance with no influence on the ozone depletion and has been a dominant refrigerant in most domestic heat pumps. However, R410A has a significant impact on the climate due to its high global warming potential (GWP). Thus, the heat pump industry has been focusing on the development of R410A substitutes. Pure refrigerant alternates, such as HFC32, and the blends mixed with low-GWP refrigerants, such as HFO1234yf and HFO1234ze(E), are widely reported. Besides the direct impact of refrigerants (which is estimated as GWP), domestic heat pumps indirectly affect the environment from the energy consumption and manufacturing processes. Hence the life cycle climate performance (LCCP) analysis accounts for all emissions through the lifetime of a heat pump. This article reports the LCCP evaluation of various low-GWP refrigerants for R410A replacement on domestic heat pumps. Six refrigerants, i.e., HFC32, binary blends of HFC32 and HFO1234yf (with GWP values of 300, 200 and 150), and HFC32 and HFO1234ze(E) with GWP values of 300 and 200, were compared against R410A. The performance data of these refrigerants from the experimental heat pump facility were utilized to evaluate the LCCP. Among the selected refrigerants, the binary blend of HFC32/HFO1234ze(E) with GWP 300 shows the lowest LCCP. Low-GWP refrigerants would become more competitive than R410A when CO2 emission from energy generations can be reduced by the optimization of the system or the usage of renewable energy.

Seasonal energy performance characteristics of novel ejector-expansion air conditioners with low-GWP refrigerants

The objective of this study is to investigate the seasonal performance characteristics of novel ejector-expansion air conditioners (EEACs) with low global warming potential refrigerants. A simplified simulation model for EEACs is developed and validated using measured data. Using a simulation model, the coefficient of performance, cooling seasonal performance factor, and life cycle climate performance of the EEACs employing low global warming potential refrigerants are analyzed at various operating conditions and modes. In addition, the climatic effects on the cooling seasonal performance factors and life cycle climate performances of the EEACs are evaluated at four different weather conditions. The EEAC with R290 exhibits the cooling seasonal performance factor and total CO2 emissions that are 22% higher and 23.3% lower, respectively, than those of the baseline air conditioner with R410A. In general, R290 is the best working fluid for EEACs in terms of the seasonal performance and lifetime environmental factor.

R134a'ya Alternatif Bir Soğutucu Akışkan (R513A) Kullanan Buhar Sıkıştırmalı Soğutma Sistemlerinin Enerji ve Çevresel Analizi

Küresel ısınma Dünya gündeminin ana konularından birisidir. Dolayısıyla, soğutucu akışkanların çevresel etkilerini azaltmak için birçok çalışma ve düzenleme yapılmaktadır. Çevre dostu soğutucu akışkanların kullanılması soğutucu akışkanların çevre üzerinde olumsuz etkisinin azaltılması için gereklidir. Düşük küresel ısınma potansiyeline (GWP) sahip HFC/HFO soğutucu akışkan karışımları HFC soğutucu akışkanların yerini aldığı düşünülmekte ve son zamanlarda ticari olarak üretilmektedirler. Bu çalışmada, R134a ve R513A soğutucu akışkanlarının performansları teorik olarak incelenmiştir. Ayrıca soğutucu akışkanların çevresel etki değerlendirilmesi yaşamsal döngü iklim performansına (LCCP) göre incelenmiştir. Soğutucu akışkanların enerji performansları farklı evaporatör (-15 ile 2.5 oC arasında) ve kondenser (30 ve 35 oC) sıcaklıkları için yapılmıştır. Evaportaör sıcaklığı -15 oC ve kondenser sıcaklığı 30 oC iken R134a ve R513A’nın COP değerleri sırasıyla 3.87 ve 3.77’dir. Aynı kondenser sıcaklığı için evaporatör sıcaklığı 2.5 oC olduğunda R134a ve R513A’nın COP değerleri sırasıyla 7.28 ve 7.16 olmaktadır. Dolaysıyla R134a ve R513A’nın COP değerlerinin hemen hemen benzer olduğu söylenebilir. R513A’nın GWP oranı R134a’nın yaklaşık yarısı kadardır. Dolayısıyla R513A R134a’dan %56 oranında daha az direkt emisyon (DE) değerine sahip olduğu görülmüştür. Her iki soğutucu akışkanın toplam emisyon değerinin büyük bir çoğunluğu (R134a için %94.98, R513A için %96.77) sistemin enerji tüketiminden kaynaklanmaktadır. R513A soğutucu akışkanın yanıcılık özelliğinin yoktur ayrıca doğrudan R134a ile çalışan sistemde herhangi bir değişiklik yapmadan kullanılabilir. R513A yukarıda saydığımız özelliklerden dolayı R134a’ya alternatif olarak kullanılabilir.

Assessment of heat pump with carbon dioxide/low-global warming potential working fluid mixture for drying process: Energy and emissions saving potential

Drying is one energy-intensive process in the industry. Heat pump system for drying process by employing carbon dioxide/low-global warming potential working fluid mixture is proposed and compared with traditional boiler drying systems. A life cycle thermodynamic and environmental evaluation model is developed to assess the energy consumption, gaseous and particulate matter emissions saving potential by using the new heat pump drying solutions. With the help of carbon dioxide/low-global warming potential working fluid mixtures, the coefficient of performance of heat pump dryer is obviously enhanced and the discharge pressure is reduced. The highest coefficient of performance of 4.29 is achieved by using carbon dioxide/R32 under the mass fraction of 0.1/0.9, which is increased by 7.42% in contrast to pure carbon dioxide. The specific moisture extraction rate is improved and the primary energy consumption throughout the lifetime is dramatically reduced. The life cycle climate performance is also reduced and the equivalent carbon dioxide emissions from energy consumption are the dominant category. Carbon dioxide-based mixture heat pump dryer can also reduce the pollutant emissions. Compared with natural gas-fired boiler system, oxynitride emissions are decreased by 81.66%, and particulate matter emissions are less than a quarter of the electric boiler. Carbon dioxide/low-global warming potential working fluid mixtures with low or medium-temperature glide, and high-temperature glide carbon dioxide/low-global warming potential working fluid mixtures with extremely low (~0.1) or very high (~0.9) carbon dioxide mass concentrations are recommended. The heat pump dryer charged with carbon dioxide/low-global warming potential working fluid mixtures is a promising solution to substitute traditional boilers for energy-saving and environmentally-friendly industrial drying.

Investigation of using R134a, R1234yf and R513A as refrigerant in a heat pump

Various studies and arrangements have been made in recent years to reduce the effect of refrigerants used in cooling and heating systems on climate change. Environmentally friendly refrigerants with low global warming potential are required to reduce the negative impact of air-conditioning systems on climate change. HFO and HFC/HFO refrigerant mixtures (such as R513A) are thought to replace HFC refrigerants and are also commercially produced recently. In this study, R134a, R1234yf and R513A refrigerants have been investigated theoretically and experimentally under the same operating conditions. Refrigerants were tested at the same evaporator (− 10 °C, − 5 °C and 0 °C) and condenser (35 °C) temperatures. In addition, life cycle climate performance assessment analyses of refrigerants were performed. It is found that when the evaporator temperature is − 10 °C and − 5 °C, R513A has a higher COPHP than R134a. However, R513A has a lower COPHP than R134a at 0 °C the evaporator temperature. R1234yf has a high COPHP compared to R134a at the − 10 °C evaporator temperature while it has a low COPHP at − 5 °C and 0 °C evaporator temperatures. R513A and R1234yf refrigerants have 14.45% and 17.16% less emissions than R134a, respectively.

Life cycle energy, emissions and cost evaluation of CO2 air source heat pump system to replace traditional heating methods for residential heating in China: System configurations

Heat pump is an efficient method to substitute traditional boilers for cleaner space heating. A new configuration of CO2 heat pump system integrated with vapor injection and dedicated mechanical subcooling (VIDMS) is proposed, and compared with five configurations of CO2 heat pump system and three traditional heating methods. The life cycle model of energy consumption, pollutant emissions, and economic performance is developed. Assessment is conducted by taking seven typical cities located in different climate regions of China as scenarios. Coefficient of performance (COP) of VIDMS system is superior to other transcritical CO2 systems, and the COP is enhanced more notably in the case of severe cold or cold regions. The COP reaches up to 2.13 at the low ambient temperature of −20 °C, 36.51% higher than the baseline (BASE) CO2 system. The primary energy consumption (PEC) of the other five CO2 systems and coal-fired boiler (CFB) can decrease by 4.15–18.26% and 19.27%, respectively, when VIDMS is adopted. Moreover, the PEC reduction is more prominent when used in severe cold region. Life cycle climate performance (LCCP) decreases significantly by employing VIDMS compared with other transcritical CO2 systems and traditional heating methods. CO2 emissions can be reduced by 13.81–23.20% and 16.56–34.31% in contrast to BASE and CFB, respectively. Furthermore, the gaseous (NOx and SO2) and particulate matter (PM2.5 and PM10) emissions also decrease. Life cycle cost (LCC) by using VIDMS is much lower than the other transcritical CO2 systems. The payback period is reduced from 5.58 to 3.55 years if the price of electricity and CO2 compressor are both reduced by 20%. The new proposed VIDMS is a more promising CO2 heat pump solution to replace traditional heating methods.

Integrated supermarket refrigeration for very high ambient temperature

This paper analytically investigates and compares the performance of a proposed ‘all-natural’ NH3/CO2 cascaded booster system to a conventional R404A direct expansion system as well as to an ‘all-CO2’ system with multi-ejector unit and flooded evaporator. Performance comparison is made based on the annual combined COP and Life Cycle Climate Performance (LCCP) for operation in selected cities of Middle East and India. Our results show that in extreme warm climate, the energy efficiency of the proposed configuration exceeds that of all-CO2 configuration by a maximum of about 12.23% and the total emissions are lower by up to 11.20%. However, the all-CO2 multi ejector system performs better in cold and mild warm climate. In the NH3/CO2 cascade, the high temperature NH3 system can be designed to be isolated from the accessible locations of the supermarket. The work presented is expected to help adoption of natural refrigerants such as CO2 and NH3 for commercial application in extreme warm climate conditions prevailing in many cities of Middle East and India.

Experimental study on R-22, R-427A, R-161 and R-290 in air-source heat pump for space heating at low ambient temperatures

To help reduce the warming impacts, this study evaluates the drop-in performances of R-427A, R-161 and R-290 in R-22 air source heat pump with EVI (Economized Vapor Injection). The results show that the IPLV(H) of R-161 and R-290 arises 5∼8% relative to R-22 with EVI on. A reversal occurs between R-290 and the baseline with EVI on, making the IPLV(H) of R-290 superior to that of R-22 by 3.6∼5.2% from worse performance with EVI off. At -20/41 °C condition, the capacity and COP of R-290 increase by 38% and 19%, respectively. Considering COP and discharge temperatures, R-290 is better-performed to replace R-22 in high pressure ratio conditions. Based on LCCP (Life Cycle Climate Performance) model, 11% of the equivalent CO2 emission can be reduced by using R-161 and R-290. However, the discharge temperature of R-161 is high in the high pressure ratio condition. R-290 is the most synthetically beneficial alternative.

Analysis of two-phase injection heat pump using artificial neural network considering APF and LCCP under various weather conditions

The objective of this study is to optimize the performance of a two-phase injection (TPI) heat pump considering annual performance factor (APF) and life cycle climate performance (LCCP). The performances of non-injection (NI), vapor injection (VI), and TPI heat pumps are measured under various outdoor temperatures. Based on the measured data, artificial neural network models for the NI, VI, and TPI heat pumps are developed to predict the performance indexes during cooling and heating seasons. As a result, the TPI heat pump shows higher heating capacity than the NI and VI heat pumps with a lower compressor discharge temperature in cold weather conditions. Therefore, the application of the TPI has a merit on reducing the size of the heat pump due to its lower back-up heater loss and over-capacity penalty. When the objective function maximizes the APF for system optimization in three climate regions, the TPI heat pump shows a 1.4–2.7% higher APF than the NI heat pump, and a 11.1%–18.1% smaller optimum rated heating capacity.