Chill Units Research Articles

Chill unit models for predicting dormancy completion of floral buds in apple and sweet cherry

Temperature-controlled experiments were conducted to determine the relative contribution of temperatures to dormancy completion of floral buds in ‘Gala’ apple (Malus domestica Borkh.) and ‘Sweetheart’ sweet cherry (Prunus avium L.). Shoots were collected right before chill inception, and exposed continuously to seven different temperatures in the range of −2°C and 16.8°C for 1320 hours. Chilling requirements were determined on sequential field samples from plots of days to bud break against sampling date. Temperature-response curves, which were best fit in a four parameter logistic nonlinear regression, indicated that optimum chilling temperatures were between −2°C and 5.5°C for ‘Gala’ and between −2°C and 7°C for ‘Sweetheart’, with no chilling effect above 13°C in both species. The derived chill unit models predicted that chill unit accumulations required for dormancy completion averaged 921 for ‘Gala’ and 740 for ‘Sweetheart’ over the three year period. The year-to-year variation in ‘Gala’ apple was smaller with our ‘Gala’ model than with the ‘Utah’ model (14% vs 23.5% coefficients of variation), while similar to each other in ‘Sweetheart’ sweet cherry.

Improved Energy Performance of Air-Cooled Liquid Chillers with Innovative Condensing-Coil Configurations

The purpose of this study was to develop mathematical models for air-cooled chillers and their components using innovative varied row configurations as a parameter analysis model followed by a simulation of actual operational performance. In this manner, we were able to observe the increase in performance of air-cooled chillers and the energy transfer efficiency of individual components. This study found that the innovative varied row configuration (Type C) can increase the COP of air-cooled chiller by 6.7% over that of traditional condensing-coil configuration (Type A) with an increase in total irreversibility and the irreversibility of the condenser of 8.4% and 4.1%, respectively; Type C can increase the COP of air-cooled chiller by 3.3% over that of the best condensing-coil configuration (Type B) with an increase in total irreversibility and the irreversibility of the condenser of 1.6% and 4.6%, respectively. We believe that the results of this research can provide an important basis of reference for future design of air-cooled chiller units.

Identification of chilling and heat requirements of cherry trees—a statistical approach

Most trees from temperate climates require the accumulation of winter chill and subsequent heat during their dormant phase to resume growth and initiate flowering in the following spring. Global warming could reduce chill and hence hamper the cultivation of high-chill species such as cherries. Yet determining chilling and heat requirements requires large-scale controlled-forcing experiments, and estimates are thus often unavailable. Where long-term phenology datasets exist, partial least squares (PLS) regression can be used as an alternative, to determine climatic requirements statistically. Bloom dates of cherry cv. ‘Schneiders späte Knorpelkirsche’ trees in Klein-Altendorf, Germany, from 24 growing seasons were correlated with 11-day running means of daily mean temperature. Based on the output of the PLS regression, five candidate chilling periods ranging in length from 17 to 102 days, and one forcing phase of 66 days were delineated. Among three common chill models used to quantify chill, the Dynamic Model showed the lowest variation in chill, indicating that it may be more accurate than the Utah and Chilling Hours Models. Based on the longest candidate chilling phase with the earliest starting date, cv. ‘Schneiders späte Knorpelkirsche’ cherries at Bonn exhibited a chilling requirement of 68.6 ± 5.7 chill portions (or 1,375 ± 178 chilling hours or 1,410 ± 238 Utah chill units) and a heat requirement of 3,473 ± 1,236 growing degree hours. Closer investigation of the distinct chilling phases detected by PLS regression could contribute to our understanding of dormancy processes and thus help fruit and nut growers identify suitable tree cultivars for a future in which static climatic conditions can no longer be assumed. All procedures used in this study were bundled in an R package (‘chillR’) and are provided as Supplementary materials. The procedure was also applied to leaf emergence dates of walnut (cv. ‘Payne’) at Davis, California.Electronic supplementary materialThe online version of this article (doi:10.1007/s00484-012-0594-y) contains supplementary material, which is available to authorized users.

BREEDING LOW-CHILL PEACHES IN SUBTROPICAL QUEENSLAND

The low-chill peach (Prunus persica (L.) Batsch) breeding program at Maroochy Research Station, Nambour, Queensland was initiated in 1996 in response to industry requests for new peach and nectarine cultivars adapted to subtropical Australia. The program aims to develop a range of high quality peach and nectarine cultivars with both melting and non-melting flesh, with chilling requirements of 100 to 400 chill units (CU) but an emphasis on 150 CU or less. The program's breeding strategies have included collection and evaluation of germplasm from Australia, Europe, America and Asia, hybridisation with the industry standard 'Tropic Beauty' peach, inter-crossing of subtropical and temperate parents and incorporation of non melting flesh. Fruit characteristics being selected are large size, high flavour, firm flesh and early ripening. Important tree characteristics being selected are low chilling requirement, moderate crop load and compact tree habit. Over 20,000 seedlings have been produced and 53 selections propagated for second stage evaluation. Three peach and two nectarine selections have been released for large scale evaluation from 2006 to 2009.

Chilling requirement for breaking dormancy and flowering in Paeonia lactiflora ‘Taebaek’ and ‘Mulsurae’

Dormant rootstocks of Paeonia lactiflora ‘Taebaek’ and ‘Mulsurae’ (native Korean cultivars) were stored at three chilling temperatures (constant 0, 5, or 10°C) for different durations (0, 3, 6, 9, or 12 weeks) to determine the chilling requirements for dormancy breaking and flowering. For both cultivars, percent sprouting, numbers of shoots and flowers, and height during flowering increased as the plants were exposed to lower chilling temperatures or longer chilling durations, whereas the time required for sprouting gradually decreased as the duration of the chilling treatment increased. However, there were no significant differences in these parameters between the two cultivars when they were chilled for 9 weeks or more. A chilling treatment at 0°C for 6 weeks [1,008 hours chill unit (CU)] produced more number of shoots and flowers and required fewer days to achieve sprouting and flowering than at 5°C for 6 weeks (706 hours CU). Temperatures of 5°C and 10°C afforded only 70% and 40%, respectively, when compared to a cumulative chill unit at 0°C. ‘Taebaek’ required more chilling to sprout consistently and achieve its potential shoot numbers than ‘Mulsurae’. Chilling for 6 weeks at 0 and 9 weeks at 5°C (1,058 hours CU) were necessary to break dormancy and to induce flowering in P. lactiflora ‘Taebaek’ and ‘Mulsurae’, respectively.

Dormancy release and flowering of Paeonia lactiflora ‘Taebaek’ by natural cumulative chilling and GA3 treatment

Dormancy breaking and flowering of Paeonia lactiflora ‘Taebaek’ were controlled by natural cumulative chilling and GA3 treatments according to the transfer date in the central region of Suwon, Korea. Shoot emergence and flowering did not occur throughout the experimental period when dormant rootstocks were transferred to a glasshouse between September 10 and October 29, in which the natural cumulative chill (NCU) unit was nearly 0 h. The number of days from the transfer date to sprouting and flowering was shortened as the transfer date was delayed. All the plants flowered normally with shoot growth when they were transferred after December 31 (1,222 h NCU). All dormant buds that were treated with GA3 sprouted, regardless of transfer date, but failed to flower due to shoot blasting and flower bud abortion when they were transferred between September 10 (0 h NCU) and November 12 (185 h NCU). Shoot blasting was 38% when they were transferred on November 26 (429 h NCU). When GA3 was applied to the plants after December 17 (876 h NCU), they flowered without blasting. Plant height and stem diameter were not affected by GA3 treatment. GA3 treatment decreased the number of days to sprouting and flowering, and increased the number of flowers, irrespective of insufficient chilling accumulation, as compared to 1,222 h NCU on December 31. According to the above results, at least 1,222 h NCU could be recommended as a practical forcing method for dormancy release, subsequent growth, and normal flowering of dormant P. lactiflora ‘Taebaek’ in a temperate climate region. The GA3 treatment played an important role in breaking dormancy and significantly increased the percentage of sprouting, accelerated the days to sprouting and promoted the flowering of P. lactiflora ‘Taebaek’ when the plants had undergone insufficient chilling accumulation.

Experimental study of an air-cooled thermal management system for high capacity lithium–titanate batteries

Lithium–titanate batteries have become an attractive option for battery electric vehicles and hybrid electric vehicles. In order to maintain safe operating temperatures, these batteries must be actively cooled during operation. Liquid-cooled systems typically employed for this purpose are inefficient due to the parasitic power consumed by the on-board chiller unit and the coolant pump. A more efficient option would be to circulate ambient air through the battery bank and directly reject the heat to the ambient. We designed and fabricated such an air-cooled thermal management system employing metal-foam based heat exchanger plates for sufficient heat removal capacity. Experiments were conducted with Altairnano's 50 Ah cells over a range of charge-discharge cycle currents at two air flow rates. It was found that an airflow of 1100 mls−1 per cell restricts the temperature rise of the coolant air to less than 10 °C over ambient even for 200 A charge-discharge cycles. Furthermore, it was shown that the power required to drive the air through the heat exchanger was less than a conventional liquid-cooled thermal management system. The results indicate that air-cooled systems can be an effective and efficient method for the thermal management of automotive battery packs.

Mathematical model for estimation of the three-dimensional unsteady temperature variation in chilled packaging units

A mathematical model for heat transfer from surrounding environment to a single food package is developed. A simplified analytical solution for three-dimensional (3D) unsteady temperature distribution in the food package with rectangular geometry taking into account the ambient temperature is obtained. The model is developed to be used as an efficient tool for estimating the effects of temperature abuse on the food product inside a single packaging unit. The food product is considered to be a homogenous solid body. The packaging material and air inside the package are modeled using an effective heat transfer coefficient. The developed model is validated by a comparison with experimental results obtained for fresh haddock fillets in expanded polystyrene (EPS) boxes exposed to temperature abuse and by comparison with numerical results obtained by the commercial software FLUENT. A satisfactory agreement was obtained between the experimental and numerical results.

Flower development and effects of a cold treatment and a supplemental gibberellic acid application on flowering of Helleborus niger and Helleborus x ericsmithii

The increased horticultural interest in Helleborus requires the development of techniques for flowering control. Therefore, we have determined flower initiation and differentiation under natural conditions for Helleborus niger L. and the hybrid Helleborus x ericsmithii B. Mathew. Once flower primordia were present in the underground buds of the plants, the effect of a cold treatment (336, 504 or 672 chilling units (CU)) and a supplemental gibberellic acid (GA3) application (500mgL−1) on pre-cooled plants was examined. The cold treatment resulted in a progressive decrease of the time to flower. Moreover, when pre-cooled plants received a supplemental GA3 application early flowering was further enhanced and these plants had a higher number of flowers with longer flower stems and larger flowers.

A framework of the requirements for the management of a nuclear fuel cycle facility

This study introduces a system that can confirm whether all requirements are satisfied, by systematically managing from the highest design requirements to the requirements for the lowest unit devices of the PRIDE facility through mutual relationships, and effectively traces the influences of the requirement changes. To carry out the technology traceability based on pyroprocess facility design data and research data, we need a database system that can manage an extensive amount of data. This paper explains the procedure of developing a pyroprocess system engineering framework and data schema established for this. To confirm whether the technology traceability is carried out within a reliable boundary based on the top requirements, system requirements, sub system requirements, and component requirements of the derived PRIDE system, an experiment was done with an Ar (Argon) cooling system as a target. As a result of verifying the validity of the technology traceability with the sample data input, it was confirmed that, when pyroprocess separation is designed in an Inert (Ar) gas atmosphere, from the top requirements of the pyroprocess, to the capacity and electricity of the Chiller unit, which is the unit process device composed of an Ar cooling system, and down to the requirements for the type, can be effectively traced.

Impact of climate change on apple crop in Himachal Pradesh

The study examines the impact of climate change in recent years on apple shift to higher altitude in Himachal Pradesh based on climate information and farmers perceptions. It is evident that temperature in apple growing regions of Himachal Pradesh showed increasing trends whereas precipitation showed decreasing trends. The temperature trends in apple growing regions of Kullu and Shimla indicated 1.8 to 4.1 0C rise in past two decades which reflected in decrease of chill units (CU) hours accumulations. The annual snow fall decreasing rate of 36.8 mm with decreasing trends of snowfall during early winters (October & December) and late winters (March and April) clearly indicated the shrinking winter period in high hills. The CU hours showed decreasing trends upto 2400 meter above mean sea level (amsl) from Bajaura in district, Kullu at 1221 m amsl to Sarbo in district Kinnaur at 2400 m amsl. The Dhundi station situated at 2700 m amsl showed increasing trend of chill unit at the rate of 25.0 CUs per year. The increasing trends of chill units at 2700 m amsl suggested that area is becoming suitable for apple cultivation in higher altitude. These findings have also been supported by the farmers’ perceptions which clearly reflected that apple cultivation is expanding to higher altitude in Lahaul and Spitti and Kinnaur. The average landuse per farm in Lahual and Spitti showed more than two percent shift towards apple cultivation but it showed reverse trend in other apple growing regions of Himachal Pradesh. The income of the farmers increased more than 10 percent in district Lahual and Spitti whereas it showed a decrease of more than 27 percent in Kullu and Shimla districts from fruits in recent decade compared to 1995. The data on area under apple cultivation also compounded statement that apple cultivation is expanding in Lahaul and Spitti in recent decade. The climate change has demonstrated its impact of decreasing productivity of apple crop in recent years.

Chilling requirement for dormancy release of variegated Solomon’s seal

Dormancy release of variegated Solomon’s seal (Polygonatum odoratum Druce var. pluriflorum Ohwi for. variegatum Y.N.Lee) was studied by varying the transferring date from the field to greenhouse and by cold storage in order to identify their precise chilling requirement. Bud emergence and flowering did not occur throughout the experiment when dormant rhizomes were transferred until a calendar date November 22, 2009, in which natural cumulative chill unit (NCU) was 75 h. Days to sprouting, flowering, and flower abscission were shortened with delayed transferring dates. Percent sprouting and flowering showed an increasing tendency since rhizomes were transferred on December 7 (= 241 h NCU), but emergence date was not uniform. However, uniform percent sprouting was maintained since rhizomes were transferred on December 22 (= 492 h NCU). No or 1 week of cold storage at 0 or 5°C did not induce sprouting, which meant bud dormancy was not released when rhizomes were stored ≤ 1 week. When they were stored for more 2 weeks at 0 or 5°C, percent sprouting was increased to ≥ 91% in the heated greenhouse. Cumulative chill unit (CCU) was 336 h at 0°C and 225 h at 5°C. However, bud emergence date after 2 weeks of cold storage was not uniform at both storage temperatures, whereas bud emergence after 4 weeks of cold storage at 0°C was more uniform than that at 5°C. Therefore, at least 492 h NCU, 4 weeks of cold storage at 0°C (= 672 h CCU), or 6 weeks at 5°C (= 675 h CCU) is recommended for forcing and normal growth afterward of variegated Solomon’s seal.

Thermodynamic simulation of condensation heat recovery characteristics of a single stage centrifugal chiller in a hotel

A thermodynamic simulation study has been carried out for a single stage centrifugal chiller in this paper. The cooling capacity of the chiller unit is about 1750 kW. The chiller unit has been set and tested, and the work refrigerant is R22. A heat exchanger has been set between outlet of the compressor and the condenser for sanitary hot water supplying. Then the chiller unit is a kind of combined system that can provide sanitary hot water supplying and air conditioning simultaneously. A thermodynamic simulation model of the combined system has been established with the system simulation toolbox Simulink. Performance of the components and the combined system of the chiller unit has been studied over a wide range of operating conditions. The potential energy and fuel cost saving associated with the use of the proposed combined system for a typical hotel in south China has been estimated. It is showed that the combined system of the chiller unit is very useful in hotel buildings. And the thermodynamic simulation model of the combined system is significance for the optimization of parameters of the chiller unit such as condensation and evaporation temperature, mass flow of the sanitary hot water and size of hot water storage tank.

The Energy Saving Operation Design for Large Multi-Chiller System

The large multi-chiller system is commonly used in the semiconductor factories and electronics factories, it is one of the department consumed a great deal of energy in factory. Therefore, it is worthwhile to design the chilled water system operation. In this paper, a design methodology is developed for multi-chiller system in which chiller units consist of different cooling capacities chiller that run in parallel. The optimal integrity scheme can be obtained using the MINLP method which minimizes the system energy consumption within a future time period. Instead of a lag scheme used in the general method, this forecasting scheme provide a integral optimal schemes within a future time period and offers the operating reference for operators.

Study on Operation and Control of Large Multi-Chiller System

In semiconductor factories and electronics factories, a large multi-chiller system is needed to satisfy strict cooling load requirements. In order to save energy, it is worthwhile to design the chilled water system operation. In this paper, a design methodology is developed for multi-chiller system in which chiller units consist of different cooling capacities chiller that run in parallel. The optimal design problem can be expressed as a mixed integer nonlinear programming (MINLP) which minimizes the system energy consumption within a future time period. In order to solve this complex problem, the two-stage strategy is employed to divide the problem into a scheduling stage and an operating stage. Instead of a lag scheme obtained with general method, this forecasting scheme consists of a series of optimal scheme at each sub-time period and can offer operating reference for operator. The effectiveness of the proposed method is illustrated by an industrial case

An experimental study of pool boiling and falling film vaporization on horizontal tubes in R-245fa

This study investigates heat transfer performance on horizontal copper tubes in refrigerant R-245fa, having zero ozone-depleting potential. Pool boiling and falling film vaporization experiments were conducted at saturation temperatures of 5 °C (a typical saturation temperature of evaporators in commercial chiller units) and 20 °C, while heat fluxes varied from 4.5 to 48.5 kW/m 2 . A smooth tube, a fin tube of 0.4 mm fin height, 60 FPI (Fins Per Inch), and a new boiling enhanced tube (mesh tube) were tested. Falling film vaporization heat transfer coefficient of the fin tube is greater than that in pool boiling, but the opposite results were found for the mesh tube. The mesh tube yielded up to 5 and 7 fold heat transfer enhancement in falling film vaporization and pool boiling, respectively. Under the same test conditions, R-245fa resulted in slightly higher heat transfer coefficients than R-123. New correlations of falling film vaporization on smooth tubes with and without boiling are proposed. The falling film evaporation (non-boiling) correlation predicted the data within ±16%. The falling film vaporization correlation accounting for nucleate boiling predicted heat transfer coefficients with ±20% uncertainty for data of smooth tube in the range of Re f = 115–372, Bo F = 0.044–0.473, We F = 0.000165–0.00168 and Pr f = 6.26–7.15. ► Pool boiling and falling film vaporization performance were tested in R-245fa. ► A smooth tube, a fin tube, and a new boiling enhanced (mesh) tube were tested. ► Mesh tube yielded 5 fold enhancement in falling film evaporation, 7 fold in boiling. ► The proposed correlations predicted the boiling\non-boiling data within ±16%\20%.

CLIMATE CHANGE IN THE WESTERN CAPE OF SOUTH AFRICA: TRENDS, PROJECTIONS AND IMPLICATIONS FOR CHILL UNIT ACCUMULATION

The Western Cape region of South Africa, a major producer of deciduous fruit, has been identified as highly vulnerable to climate change. Climatic trends were analysed on a monthly basis for 12 rural meteorological stations across the region for the period 1967 to 2007. Significant warming trends were found for midto late-summer and end-winter to spring for daily minimum temperature (Tmin), and for mid-summer, autumn and spring for daily maximum temperature (Tmax). Chill unit accumulation has decreased significantly, particularly in autumn. Air temperatures are predicted to increase by a further 1-2°C within the next 30 years, together with decreasing rainfall especially in autumn/winter. An analysis of possible impacts of regional projections of climate change on deciduous fruit production was conducted, with the emphasis on chilling accumulation and dormancy in apples. The warmer or otherwise more marginal production areas, and high chill cultivars are likely to be the first to experience negative impacts of warming. INTRODUCTION Global climate change is occurring as evidenced by warming of average air and ocean temperatures, melting of snow and ice, and rising sea level (IPCC, 2007). Mediterranean-climate regions worldwide have been identified as highly vulnerable to climate change (Baldocchi and Wong, 2006), including the Western Cape region of South Africa (Midgley et al., 2005). Climate projections for fruit regions for 2030-2040 include warming by 1-2°C, reductions in frontal autumn and winter rainfall, and a contraction of the winter season (Hewitson et al., 2005). Apples are generally grown under conditions of insufficient winter chilling; this necessitates the use of chemical rest-breaking treatments to achieve satisfactory budburst, fruit set, yield, and fruit quality (Cook and Jacobs, 2000). In the event of climate warming, we expect that accumulation of chill hours will decrease, eventually reaching a critical threshold at which apple production would no longer be commercially sustainable in currently marginal areas. However, the rate of decline in chill hours could vary intra-seasonally, with different phenological results, and between colder and warmer production areas. We set out to analyze recent historical regional-scale changes in temperature and chill accumulation, predicted reductions in chill accumulation with future warming, and implications for fruit production, particularly apples. MATERIALS AND METHODS Recent Historical Temperature and Chill Unit Trends in the Western Cape Quality-controlled data for twelve meteorological stations throughout the Western Cape of South Africa (Fig. 1) were obtained from the division AgroMet of the Institute for Soil, Climate and Water, Agricultural Research Council, South Africa, for the period 1967-2007. The stations are spread throughout the climatically divergent fruit-growing regions. Daily minimum (Tmin) and maximum (Tmax) air temperatures, and monthly means of Tmin and Tmax were used. Langkloof Experimental Farm was excluded due to closure in Proc. IX IS on Orchard Systems

The response of Corylus avellana L. phenology to rising temperature in north-eastern Slovenia

Knowledge of plant-weather relationships can improve crop management, resulting in higher quality and more stable crop yields. The annual timing of spring phenophases in mid-latitudes is largely a response to temperature, and reflects the thermal conditions of previous months. The effect of air temperature on the variability of hazelnut (Corylus avellana L.) phenophases (leafing, flowering) was investigated. Meteorological and phenological data for five cultivars were analysed over the periods 1969-1979 (P1) and 1994-2007 (P2) in Maribor, Slovenia. Phenological data series were correlated strongly to the temperature of the preceding months (R(2): 0.64-0.98) and better correlated to daily maximum and mean temperatures than to daily minimum temperatures. About 75% of phenophases displayed a tendency towards earlier appearance and a shorter flowering duration during P2, which could be explained by the significant temperature changes (+0.3°C/decade) from December to April between 1969 and 2007. An increase in air temperature of 1°C caused an acceleration in leafing by 2.5-3.9 days, with flowering showing higher sensitivity since a 1°C increase promoted male flowering by 7.0-8.8 days and female flowering by 6.3-8.9 days. The average rate of phenological change per degree of warming (days earlier per +1°C) did not differ significantly between P1 and P2. An estimation of chilling accumulation under field conditions during 1993-2009, between 1 November and 28 February, showed that all four of these months contributed approximately similar amounts of accumulated chilling units. The growing degree days (GDD) to flowering were calculated by an estimated base temperature of 2°C and 1 January as a starting date, given the most accurate calculations. In general, thermal requirements were greater in P2 than in P1, although this difference was not significant. Longer-time series data extended to other agricultural and wild plants would be helpful in tracking possible future changes in phenological responses to local climate.

Spread of Pseudomonas fluorescens Due to Contaminated Drinking Water in a Bone Marrow Transplant Unit

Pseudomonas infections are an important cause of morbidity and mortality in immunocompromised patients. We present here data for the spread of Pseudomonas fluorescens caused by a contaminated drinking water dispenser in a bone marrow transplant unit. Over a 1-month period we observed a sharp increase in the isolation of P. fluorescens from weekly pharyngeal surveillance swabs. Environmental samples were taken from a variety of water sources throughout the unit. These samples were cultured on cetrimide agar medium, and isolates were epidemiologically characterized by antibiotic susceptibility patterns and molecular typing methods. Nine patients became colonized with P. fluorescens, and six out of the nine developed febrile neutropenia. P. fluorescens was cultured after the filtration of 100 ml of drinking water from one of two stand-alone chiller units supplying cooled bottled water to the bone marrow transplant unit. All other environmental samples were negative. There were no further cases of P. fluorescens colonization after the contaminated dispenser was removed. Molecular typing showed that all P. fluorescens isolates were identical by both random amplification of polymorphic DNA PCR and pulsed-field gel electrophoresis. We recommend that such bottled water supplies not be used in high-risk areas or be subject to regular microbiological monitoring.

Integration of trigeneration in an indirect cascade refrigeration system in supermarkets

This article presents an energy and economic analysis of a trigeneration configuration for supermarket applications. The energy system in a supermarket is relatively complex, because it includes lighting, air conditioning, cabinets, refrigeration system, etc. A trigeneration system could be used to simultaneously satisfy heating, refrigeration and electricity demands in supermarkets. More specifically, this article studies the integration of a trigeneration system and an indirect refrigeration cascade compression system in a supermarket in Barcelona. The trigeneration system consists of a cogeneration engine and an ammonia/water absorption chiller unit. The results of simulating energy usage, life cycle costs and CO2 emissions have been compared with a conventional indirect refrigeration cascade compression system for the supermarket studied. Several trigeneration configurations have been studied. They all show a payback time of less than 6 years but the profitability of the investment depends strongly on the ratio between the prices of natural gas and electricity. This study shows that this novel trigeneration system is economically feasible and environmentally more viable than conventional supermarket systems.