Chiller Research Articles

A Bayesian-interference approach to quantify degradation parameters in a water-cooled variable speed screw compressor chiller

Abstract Variable-speed screw chillers can provide effective capacity modulations in commercial buildings to reduce energy consumption, match the load requirements, and contribute to lower equivalent carbon emissions. However, variable-speed operation can also yield to degradation phenomena inside the compressor. Assessing the real-time health status of chillers and detecting anomalies are important aspects to ensure long-term operation and improve reliability. To this end, an automated accelerated life test (ALT) procedure was developed and applied to a 513 kW (145.9 RT) water-cooled variable-speed screw chiller in a laboratory test facility to experimental assess performance degradation over time. After every 1,000 operating hours of ALT, steady-state performance tests at 30%, 50%, 75% and 100% load were conducted according to AHRI Standard 550/590. Additional operating conditions were included while conducting the tests to provide a more complete assessment of the degradation trends compared to the initially measured baseline. The experimental data set was then used to quantify the performance degradation based on the impact on the screw compressor operation. A Bayesian-inference identification approach has been developed to identify changes of sensitive parameters that statistically provide evidence for the likelihood of a performance degradation of the compressor. The information was used to implement the parameters in a dynamic model which was used to perform studies to predict the degradations of a chiller. The outcomes of this study help to improve the maintenance schedule of a compressor and even the whole chiller so that the system can be operated more economically and unplanned downtime can be minimized.

Design, optimization, and performance analysis of a solar-wind powered compression chiller with built-in energy storage system for sustainable cooling in remote areas

This study aims to develop a sustainable cooling solution for refrigeration in remote areas, utilizing solely wind and solar power. Ensuring that the power generated aligns with consumption throughout the day is a critical challenge. The investigation centers on the integration of an energy storage and a compression cooling cycle to attain the desired objective. This system integrates refrigerant storage on both the evaporator and condenser sides. The storage tanks' volume is variable by time and should be adjusted automatically. The sustainability of the cooling capacity depends on the amount of input power and the type of refrigerant. Moreover, additional heat is extracted to produce hot water. The analysis includes the coefficient of performance, exergy efficiency, cooling capacity, total heating capacity, and environmental impacts for six refrigerants R134a, R22, R717, R125, R500, and R407c. The system is configured to offer a cooling capacity of 15 kW while maintaining a temperature difference of 38K. The best performance is achieved using R717 as the refrigerant with a coefficient of performance of 5.26, an exergy efficiency of 36 %, and a payback period of 2.267 in Sabzevar. Furthermore, R717 does not contribute to ozone depletion or global warming.

Comparative analysis of energy efficiency for three heating and cooling supply schemes in a region with hot summers and cold winters in a chemical industrial park

Building energy consumption in China accounts for 45% of the total national energy consumption, with air conditioning energy consumption representing approximately two-thirds of that. Therefore, energy efficiency in buildings is of utmost importance. This study focuses on a chemical industrial park located along the Fujiang River and compares three heating and cooling supply schemes: the river water source heat pump system, which utilizes river water as the heat source and heat sink; the water cooling unit and boiler system, which uses water-cooled electric compression chillers for cooling and an oil-fired boiler system for heating; and the split air conditioning and gas water heater scheme, which relies on refrigerants such as fluorine-containing compounds for cooling and a gas water heater for heating. By calculating the energy consumption of the above three schemes and conducting a comparative analysis, it is found that the river water source heat pump system exhibits significantly higher energy efficiency throughout the year compared to the water cooling unit and boiler system and the split air conditioning and gas water heater scheme. This highlights the notable energy efficiency advantage of the river water source heat pump system.

Design and optimization of a geothermal absorption cooling system in a tropical climate

The electricity required for air conditioning is soaring worldwide. Absorption chillers represent an alternative to classical vapor compression systems, using heat instead of electricity. However, absorption chillers powered by renewable geothermal heat have received little attention so far. This paper introduces a system using a hot geothermal fluid (typically in the range of 80–110 °C) to produce cooling through a single-effect absorption chiller, and Domestic Hot Water (DHW) through a heat exchanger. It considers a hotel located in Martinique, a French Caribbean island. The electric consumption of every subsystem has been thoroughly estimated. The originality of this paper is twice: i) the system is modelled in TRNSYS software considering dynamic conditions, ii) the system undergoes surrogate modelling and multi-objective optimization to minimize both the cost and the CO2 content of the delivered thermal energy. Several scenarios are considered, depending upon the geothermal temperature, mass flow rate, well remoteness, and demand size. The studied system appears to be systematically more expensive than a combination of a classical vapor compression chiller and a boiler for DHW. However, it can significantly decrease the CO2 content of the provided energy, especially in an island where most electricity is generated from fossil fuels. The proximity of the geothermal well and the use of the warm water leaving the absorption generator (here for DHW production) appear to be key factors for system relevance, along with a hotter geothermal fluid (e.g., 110 °C instead of 80 °C).

Energy and exergy analysis with environment benefit of the underground cooling system of the chiller plant

Using an underground heat exchanger as an alternative to a wet cooling tower can offer several benefits, particularly in terms of energy efficiency and environmental impact. Heat exchangers and cooling towers are chosen depending on various factors, such as the application size, local climate conditions, and economics. The purpose of this study is to compare the use of an underground heat exchanger with a wet cooling tower for cooling purposes. The underground heat exchanger and wet cooling tower provide cooled water for vapor compression chillers. The comparison is conducted on technical, economic, and environmental grounds. Research has been conducted in the Mashhad region, where water resources are limited and cooling demands are high during the summer. In this context, Ferdowsi University of Mashhad is selected as a case study. Energy and water consumption are calculated and compared by simulating and modeling both methods of producing cooled water and the refrigeration cycle. However, improving the alternative mode's exergy efficiency was discussed for all system components. The findings reveal that using the underground heat exchanger results in a 14% reduction in energy consumption and eliminates water consumption. The current water-cooled compression chillers consume approximately 1.95 cubic meters of water per square meter of the building daily.

Absorption Chiller Efficiency Increasing at Waste Heat Recovery of Cogen-eration Plants using a Vapor Compression Chiller as a Backup Cold Source

Cooling efficiency in a trigeneration cycles is one of the most frequently problems. A single-stage hot water absorption chiller is a universal solution for the gas engine waste heat utilization. How-ever, trigeneration centers exploitation experience shows the need for a more detailed technical and economic analysis to achieve maximum efficiency of the three-generation cycle. The purpose of this article is to substantiate the use of two-stage absorption cycles increasing the utilization rate of waste gas heat. The study presents the results of assessing the efficiency of using energy resources on the example of a three-generation center with more than 14 years of exploitation experience, including two single-stage absorption chillers (Q0= 0.65 MW each) and a chiller with a screw compressor (Q0= 0.8 MW). A comparison of actual energy consumption with designed indicators was carried out. The influ-ence of external and internal factors on the efficiency of heat recovery from a gas engine in single-stage absorption refrigeration machines with a water-heated generator is considered. The dependence of the change in the average annual cooling coefficient during the calendar year was obtained. Based on the study, proposals were formulated to improve the energy efficiency of refrigeration supply, giving an increase in refrigeration capacity of 6.1% with a commensurate reduction in the load on the screw chiller. The option of using a combined two-stage cycle chiller (type 2) under similar operating conditions showed a COP=1.43, which provides savings of 67.45 MWh of electricity or 5.4%, on an annualized basis (assuming only waste heat is used). Additional advantages of such a cycle include increased accu-racy and stability of maintaining the water temperature at the absorption chiller evaporator due to more flexible adjustment of the temperature of the lithium bromide solution in the high-temperature generator.

Zero energy building optimization for a residential complex with a new optimized cogeneration system for electricity, cooling, heating and freshwater production

In this research, a multi-generation system was proposed to meet the energy consumption of a 120-unit zero-energy residential complex with 100 m2 and 2 bedrooms in Sydney, Australia. To meet the heating and cooling demand of the residential complex, a compression chiller was used, and electrical energy was provided using the system's production power. The main goal of this research is to define a zero-energy building by providing the energy consumption of a residential complex with a solar system. Building Energy Optimization (BEopt) Software has been used for the process of simulating the residential complex and extracting the required load of the residential complex. The design of the load supply system of the residential complex was done using EES thermodynamic software. In this research, a large number of inputs have been used in different scenarios to optimize the residential complex, and the tool used in this research by all the modes introduced as inputs turns the problem into a multi-objective optimization problem. The results of the investigation of the residential complex showed that the amount of electricity consumption, heating, and cooling of the residential complex during the year is 36728, 133123, and 17,902 kWh, respectively. Also, by optimizing the energy consumption of the residential complex, it is possible to reduce CO2 emissions and prevent the increase in environmental pollution. The optimal results showed that the system in its most optimal state can reach an exergy efficiency of 25.18 % and a system cost rate of 46.6 $/h. The performance of the system in the city of Sydney showed that the system can produce 166,164 kWh of electricity, 467,945 kWh of heating, and 183,370 kWh of cooling in one year. Comparing the results of residential complex consumption load and system production showed that the proposed system can easily provide the residential complex consumption load throughout the year.

Optimization and assessment of solar-assisted cooling systems: A multicriteria framework and comparative study

In the current context of global warming, where district cooling systems are increasingly burdening power grids worldwide, it is important to design and operate alternative systems that are not only environmentally friendly, but also cost effective for sustainable energy transition. This paper investigates the potential of two, previously unexplored, solar cooling systems while considering economic and environmental criteria: a Solar Thermal and Electrical Cooling System (STECS) that relies solely on solar energy, offering a significant environmental advantage, and a Hybrid Solar Cooling System (HSCS) that combines a compression chiller and an absorption chiller for improved efficiency. First, novel Mixed-Integer Linear Programming models are proposed to aid in generating cost-effective designs and operations for each of STECS and HSCS. Second, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is adapted to evaluate both systems and benchmark them against conventional cooling systems previously studied in the literature. The proposed framework allows decision makers to assess the potential of these systems using three criteria; namely, cost, carbon dioxide emissions, and noise levels, which are crucial for ensuring the social acceptance of district cooling technologies worldwide. A computational study is presented to show the practical relevance of the proposed framework using real-demand data obtained from an educational district in the State of Qatar. Results show that the integration of solar energy into conventional cooling systems has the potential to significantly reduce the annual total net cost by 61%, CO2 emissions by 60%, and noise levels by 53%, on average. Additionally, the benchmark results demonstrate that the zero-carbon dioxide emissions solar cooling system achieves the highest overall performance score when all criteria are considered together.

Optimal design and operation of the hybrid absorption-compression chiller plants - Energy and economic analysis

A hybrid network integrating absorption and compression chillers is a suitable solution to respond to the variable cooling demand in a large-scale chiller plant, in regions with multiple energy sources. However, the design and control challenges of such networks remain uncharted, lacking a comprehensive approach. This study presents a general procedure for designing a hybrid chiller network for a building with an arbitrary annual cooling demand distribution. The procedure determines the optimal configuration considering the different capacity ratios of absorption to compression chillers, chiller numbers, and arrangements. Utilizing the Particle Swarm Optimization algorithm, the optimal chiller loading distribution is found for each configuration. Life cycle cost analysis aids in selecting the optimal configuration. Simulations conducted in TRNSYS, reveal that optimal energy and economic choices depend on the natural gas and electricity price ratio. The best energy performance occurs at a low capacity ratio, while the economic trend varies with capacity ratio for different price ratios. The potential reduction in life cycle cost associated with the configuration, when compared to the full absorption baseline and the full compression baseline, can reach up to 7,210,000 $ (72.6%) and 724,000 $ (24.5%), respectively. From an environmental perspective, compared to the full absorption baseline and the full compression baseline, hybrid chiller configurations reduce the CO2 emissions for up to 899 tons (68.8%) and 52 tons (11.3%), respectively.

Electrochemical cell power generation systems for socially important facilities

There is an estimation of application of power installations in a mode of trigeneration: with gas at the input, and with electric power, heat and cold at the output, functioning in an automatic mode, positive and negative sides of their use are considered. Cogeneration systems based on gas turbine with compression or absorption chillers, satisfying consumers in electric, heat and cooling energy in a building or a group of buildings, are considered. The use of trigeneration systems allows efficient utilization of heat for heating in winter and for air conditioning and process needs in summer, for example, use of cold for freezers in hospitals. At the same time, there is no reduction in efficiency throughout the year. The trigeneration technology is an excellent alternative to conventional power plants with a large amount of electrical energy and allows the use of absorption chillers in case of high cost or shortage of electricity. Such units consume less electricity compared to compressor units and require lower costs. At the same time, the use of absorption refrigeration machines (ARM) is totally justified when operating in the mode of a mini-CHP, which produces heat in winter (as cold is not needed or is needed only in small amounts), and in summer there is no need for it, but there is a need for cold. The payback period of such a system is relatively low, the net present value is high, and the profitability index is usually greater than one. Cold storage contributes to the economic viability of a trigeneration system. Since the payback period does not take into account the time factor of investment, the net present value or, better yet, the profitability index should be used. A trigeneration system consists of several units with different service lives and different investment results.

Design and Operation Optimization of a Nuclear Heat-Driven District Cooling System

Carbon-free thermally driven district cooling systems (DCS) can effectively mitigate the excessive electricity consumption and carbon emissions associated with the cooling sector. This study proposes a DCS that employs nuclear heat as the primary energy source. The system comprises three main subsystems: heat station, heat transmission, and cooling station. A heat-only small modular reactor called Teplator, gas boilers, and heat storage are considered to supply the heat required to drive absorption chillers; cold storage and compression chillers are the supplementary units. The technoeconomic aspects of the system are formulated, and an algorithm is developed to determine the optimal design and operation. The method is examined for supplying a typical cooling demand profile with a peak of 2050 MWc. The resulting optimized design includes 11 nuclear plants (150 MWt each), 20 000 MWth heat storage, and 1.9 m diameter heat supply/return pipes. Absorption chillers with a total capacity of 1424 MWc are determined, covering 92% of the total cooling demand, and 244 MWc of compression chillers and 20 000 MWch of cold storage are found to cover the peak and enhance the load following. This system saved 69% of the electricity consumption and carbon emissions and 34% of the costs compared with an electric-based scenario.

Water Adsorption Dynamics on Metal-Organic Framework MOF-801: Comparative Study of Loose and Glued Grains, and Coatings.

Adsorption heat transformation and storage (AHTS) is an environmentally benign and energy-saving alternative to common compression chillers and heat pumps. The low specific power (SP) of adsorption systems is a key drawback that hinders their broader dissemination. The optimization of adsorption dynamics is a prerequisite for SP enhancement. In this work, we studied the dynamics of water vapor adsorption on MOF-801-a promising adsorbent for AHTS. For the first time, two configurations of compact MOF-801 bed, namely, grains glued to the surface of a metal support and thin adsorbent coatings, are prepared, and their porous structure is characterized. The water adsorption dynamics is compared with a common loose grains configuration. The main findings are: (a) the binder can both accelerate and decelerate the water adsorption, and its chemical nature is subject to careful selection; (b) at the initial time, heat transfer between the support and adsorbent bed controls the adsorption rate, and, at a longer time, mass transfer starts to affect it; (c) polyvinylpyrrolidone, bentonite, thermal grease, and hydroxyethylcellulose increase the heat transfer coefficients and accelerate adsorption; polyvinyl alcohol and polyaniline slow it down; and (d) for the coatings prepared with polyvinylpyrrolidone, an SP of 1.6-5.1 kW/kg can be achieved, which is about twice that for the loose grains. The new configurations can be recommended for effective but expensive adsorbents such as MOFs, and their implementation will contribute to the further spread of AHTS technology.

ANN-based procedure to obtain the optimal design and operation of the compression chiller network – Energy, economic and environmental analysis

ANN-based procedure to obtain the optimal design and operation of the compression chiller network – Energy, economic and environmental analysis

Benchmarking metal-organic framework coatings from Large-Temperature-Jump experiments: Learning from trade-offs in mean powers versus characteristic times

Adsorption chillers can substitute the electric energy demand of conventional compression chillers with low-temperature heat. The efficiency and power density of adsorption chillers depend on their adsorbent and refrigerant, which form the working pair. Novel working pairs are therefore actively developed and characterized in dynamic small-scale experiments using a characteristic time constant. However, this evaluation by only few characteristic time constants, does not resolve the trade-off between efficiency and power density of adsorption chillers and novel materials are challenging to compare due to varying size, shape, and density. To fill these gaps, we investigate the trade-off between efficiency and power density by quantifying all characteristic time constants and transferring them to specific mean powers. We perform Large-Temperature-Jump experiments with water as the refrigerant on the two metal–organic frameworks CAU–10–H and aluminum fumarate for a chilling/recooling/regeneration temperature triple of 10/30/80 °C. We compare the metal–organic frameworks’ specific mean powers to the commercially available RD type silica gels Siogel and SG123. Siogel performed best in terms of area-specific mean powers with a maximum value of 3.2 kW/m². For low time constants up to 20% relative loading, corresponding to high power density but lower efficiency, Siogel also provided the highest volume-specific mean power at 8.1 MW/m³. CAU–10–H had the highest mass- and volume-specific mean powers at 19.0–19.9 kW/kg and 7.2–8.6 MW/m3 for characteristic time constants of 35% relative loading and higher. Aluminum fumarate and SG123 showed low specific mean powers for all chosen characteristic time constants. The results show that studying specific mean powers is a useful tool to benchmark adsorption working pairs as they would perform in an adsorption chiller, regardless of mass, shape, or density.

Impact of recovery cycles on the cascade hybrid adsorption-vapor compression chillers

This study analyzed a cascade-type hybrid adsorption-vapor compression chiller. This chiller is a combination of an adsorption chiller and a vapor compression chiller, where the amount of energy absorbed in the evaporator of the adsorption chiller is equal to the heat rejected in the condenser of the vapor compression chiller. The study examined three distinct recovery schemes: heat recovery, mass recovery, and a combined heat-mass recovery approach, applied to the hybrid chiller to assess their effect on the chiller's performance and potential energy savings. The study used MATLAB and CoolProp for mathematical modeling, and the model closely aligned with earlier research. The study found that implementing mass recovery significantly improved energy efficiency and coefficient of performance compared to the basic cascade hybrid system. However, heat recovery had a negative impact on the hybrid chiller. Additionally, the study proposed an optimal duration for mass recovery in the hybrid cascade system. This research offers valuable insights into the advantages of using hybrid chiller systems and emphasizes the significance of incorporating heat and mass recovery in their design and functioning.

Reduced CO2 footprint of buildings in agro-industrial communities in Qatar with improved insulation standards and solar cooling

Food production in arid countries like Qatar is strongly linked to water and energy resources to grow plants or rear cattle in a protected and controlled environment. The high energy demand for air conditioning in agro-industrial communities leads to significant CO2 emissions. In a case-study on buildings that are typical in the agro-industrial sector, the reduction potential for these emissions is investigated. Therefore, greenhouses and community buildings with an insulation according to the Passivhaus standard and solar cooling with photovoltaic driven compression chillers are compared to conventional buildings.An innovative solar cooling system is developed: Power is generated in hybrid photovoltaic / thermal collectors to enhance the electric efficiency of the photovoltaic cells and to deliver heat for food processing or other purposes at a high temperature level. A compression chiller model is designed, that is based on the experimentally determined performance of the refrigeration cycle for the harsh operating conditions in Qatar. Different refrigerants are compared regarding their cycle performance and Global Warming Potential.A result of the study at hand is that greenhouses are very well suited for solar cooling since their cooling load is nearly congruent to photovoltaic power generation due to their low thermal inertia and radiative cooling during the night.The case study reveals that an insulation according to the Passivhaus standard combined with the proposed solar cooling system reduces the CO2 emissions caused by the air conditioning of greenhouses by 98% and of residential buildings by 94.7% compared to conventional buildings and air conditioning systems.

Energy-efficient indirect evaporative cooler design framework: An experimental and numerical study

A remarkable surge in cooling demand is observed in the last decades. Currently, the cooling market is dominated by mechanical vapor compression chillers which are energy intensive and use harmful chemical refrigerants. Therefore, the current focus of the current research in cooling is the development of unconventional, sustainable cooling systems. In this regard, indirect evaporative coolers have shown significant potential (particularly under hot-dry climates) with high energy efficiency, low cost, water-based sustainable operation, and benign emissions. However, these systems are in the development stage and have not yet been fully commercialized because of certain design challenges. An innovative indirect evaporative cooler is proposed, fabricated, and experimentally tested in this study. Particularly, the study is focused on the development of heat transfer coefficient correlation for the system for commercial-scale design and expansion. This is because the earlier available correlation is based on simple airflow between parallel plates assumption and does not incorporate the effect of the evaporative potential of the system resulting in under/over-estimation of the heat transfer characteristics. The results showed that the proposed system achieved a temperature drop of 20 °C, a cooling capacity of around 180 W, and an overall heat transfer coefficient of up to 30 W/m2K. Moreover, the study presents an experiment-regression-based heat transfer coefficient correlation that satisfactorily captures the effect of outdoor air temperature and airflow rate ratio which are critical in the design of evaporative coolers. The proposed correlation showed a high (±5%) with experimental data thus making it suitable for the future design of IEC systems over assorted operating scenarios.

Experimental Study of the Heat Flow and Energy Consumption during Liquid Cooling Due to Radiative Heat Transfer in Winter

Radiation cooling is a passive energy saving cooling technology. The process of cooling heat transfer liquid due to the combined effect of night radiative cooling and convection of air at negative temperatures (in winter) is studied. The radiator used for cooling was built into the roof of the building. Its radiating plate was made of a steel sheet coated with zinc oxide. In it, heat dissipation was carried out both from the upper and lower sides of the radiating plate. The experimental values of the heat flux ranged from 20 to 80 W·m−2 at a temperature difference between heat transfer liquid and air from 5 to 15 °C and ambient air temperature from −17 to +5 °C. The correctness of the model for calculating the heat flux in winter conditions was confirmed. A theoretical calculation showed that, in winter, the heat flux removed by the radiator will be 15% less than the heat flux in summer. The amount of heat transferred per watt of electrical power of the refrigeration unit reached 8 W·W−1. To keep the refrigeration unit with radiative heat transfer more efficient than in a conventional vapor compression chiller, the heat transfer liquid temperature should be 6 °C above the atmospheric temperature air. The results of the study show that radiative cooling can be used in winter and may be useful for the development of energy-efficient cooling systems for various purposes (air conditioning, industrial cooling systems and fruit storage chambers).

Investigation of the cascade type of hybrid adsorption-vapor compression chiller

A numerical analysis was performed on a hybrid cooling system consisting of an adsorption chiller (ADC) and a vapor compression chiller (VCC) operating in a cascade mode. The system was evaluated for its overall performance and energy savings compared to standalone ADC or VCC cooling systems. The ADC utilizes an RD silica gel/water working pair, while the VCC uses R410A refrigerant. The cooling strategy involves the ADC providing cooling for loads up to 10 kW, with the VCC supporting the ADC when cooling loads exceed 10 kW, up to 15 kW. MATLAB and Refprop were used to model the system, and the results were consistent with prior research. The study examined the effects of adsorption cycle time, hot water temperature, cold water temperature, adsorbent particle size, and intermediate mass flow rate. Additionally, the performance of different adsorbents, including CaCl2 bound to mesoporous silica (SWS-1L) and Ferro-aluminophosphate (FAM-Z01), was compared to RD silica gel. The hybrid system reduced compressor work by 94.57% and 97.69% compared to conventional VCC when the hot water temperature was set to 90 °C, and cold water temperature was set to 26 °C, respectively. The hybrid system achieved the highest energy savings and overall coefficient of performance, with SWS-1L achieving a 91.37% energy savings and a 6.71 coefficient of performance. Therefore, the cascade-type hybrid cooling system is a superior alternative, particularly for cooling loads ranging from 10 kW to 23 kW, offering significant energy savings compared to conventional VCC systems.

Comparison of Space Cooling Systems from Energy and Economic Perspectives for a Future City District in Sweden

In this study, the performance of different cooling technologies from energy and economic perspectives were evaluated for six different prototype residential Nearly Zero Energy Buildings (NZEBs) within a planned future city district in central Sweden. This was carried out by assessing the primary energy number and life cycle cost analysis (LCCA) for each building model and cooling technology. Projected future climate file representing the 2050s (mid-term future) was employed. Three cooling technologies (district cooling, compression chillers coupled/uncoupled with photovoltaic (PV) systems, and absorption chillers) were evaluated. Based on the results obtained from primary energy number and LCCA, compression chillers with PV systems appeared to be favorable as this technology depicted the least value for primary energy use and LCCA. Compared to compression chillers alone, the primary energy number and the life cycle cost were reduced by 13%, on average. Moreover, the district cooling system was found to be an agreeable choice for buildings with large floor areas from an economic perspective. Apart from these, absorption chillers, utilizing environmentally sustainable district heating, displayed the highest primary energy use and life cycle cost which made them the least favorable choice. However, the reoccurring operational cost from the LCCA was about 60 and 50% of the total life cycle cost for district cooling and absorption chillers, respectively, while this value corresponds to 80% for the compression chillers, showing the high net present value for this technology but sensitive to future electricity prices.