Experimental results on a solar desiccant and evaporative cooling system equipped with wet heat exchangers

An innovative solar assisted desiccant and evaporative cooling (DEC) system for building air conditioning has been installed at the Solar Laboratory of the University of Palermo. In this system, air-to-air packaged wet heat exchangers are used to maximise the exploitation of the evaporative cooling potential associated with the exhaust air stream. Results obtained are very positive, showing that DEC systems can benefit from the use of wet heat exchangers to efficiently cool the air stream after the adsorption process in the desiccant wheel, without any change in moisture conten

NEW DEC OPEN CYCLE FOR AIR CONDITIONING BASED ON FIXED COOLED ADSORPTION BEDS AND WET HEAT EXCHANGERS

In this work, a new solar Desiccant Evaporative Cooling (DEC) concept is presented. In the proposed system, two fixed packed desiccant beds of silica gel, operating in a batch process, are used as an alternative solution to the common adsorption rotor for dehumidifying outside air. As well known, adsorption heat due to water condensation considerably reduces the dehumidification capacity of the desiccant material, causing inefficiencies in performance. The aim of the work is to overcome the mentioned intrinsic thermodynamic limit of the adsorption rotor technology. The proposed core component is a fin and tube heat exchanger, commonly used in several air conditioning applications, wherein the spaces between the fins are filled with silica gel grains. Therefore, the adsorption material is cooled through a water loop in connection with a cooling tower. An important feature of the system is the adsorption storage capacity, this is due to the high amount of desiccant material available. An indirect cooling process of the air is then realized by means of two wet evaporative heat exchangers connected in series, with continuous humidification of the secondary side. The thermodynamic cycle is first presented and simulation results are shown and discussed. Possible applications may concern compact roof-top units as well as common AHUs

Innovative Compact Solar Air Conditioner based on Fixed and Cooled Adsorption Beds and Wet Heat Exchangers

Abstract In this work, a new all-in-one compact solar air conditioner concept is presented. The system is mainly based on a new DEC process which utilises fixed and cooled adsorption beds operating in a batch process and two wet heat exchangers. The proposed innovative adsorption bed is a fin and tube heat exchanger commonly used in the air conditioning sector, wherein the spaces between the fins are filled with silica gel grains. The main feature of this component is to allow simultaneous dehumidification and cooling of air. Furthermore, since the component hosts a considerable amount of adsorption material, solar energy can be efficiently stored in the desiccant media in terms of accumulated adsorption capacity. This potential can be used when regeneration heat is not available, strongly reducing the need for thermal storage in the solar loop. The indirect evaporative cooling process, operated downstream to the dehumidification, is realized by two wet plate heat exchangers connected in series. The process can be operated at relatively low temperature, allowing supply air temperature to the room of about 20 °C. A prototype of the compact solar air conditioner specifically developed for residential application is presented. The main features of the system as well as the thermodynamic cycle are first described. Monitoring results are presented by means of most commonly used performance indicators showing several advantages which can be obtained using the proposed solution

Serum creatine kinase isoenzymes in children with osteogenesis imperfecta

This study evaluates serum creatine kinase isoenzyme activity in children with osteogenesis imperfecta to determine its usefulness as a biochemical marker during treatment with bisphosphonate. The changes of creatine kinase (CK) isoenzyme activity during and after discontinuation therapy were observed. These results could be useful in addressing over-treatment risk prevention. Introduction The brain isoenzyme of creatine kinase (CKbb) is highly expressed in mature osteoclasts during osteoclastogenesis, thus plays an important role in bone resorption. We previously identified high serum CKbb levels in 18 children with osteogenesis imperfect (OI) type 1 treated for 1 year with bisphosphonate (neridronate). In the present study, serum CK isoenzymes were evaluated in the same children with continuous versus discontinued neridronate treatment over a further 2-year follow-up period. Methods This study included 18 children with OI type 1, 12 with continued (group A) and 6 with ceased (group B) neridronate treatment. Auxological data, serum biochemical markers of bone metabolism, bone mineral density z-score, and serum total CK and isoenzyme activities were determined in both groups. Results Serum CKbb was progressively and significantly increased in group A (p < 0.004) but rapidly decreased to undetectable levels in group B. In both groups, the cardiac muscle creatine kinase isoenzyme (CKmb) showed a marked decrease, while serum C-terminal telopeptide (CTx) levels were almost unchanged. Conclusions This study provides evidence of the cumulative effect of neridronate administration in increasing serum CKbb levels and the reversible effect after its discontinuation. This approach could be employed for verifying the usefulness of serum CKbb as a biochemical marker in patients receiving prolonged bisphosphonate treatment. Moreover, the decreased serum CKmb levels suggest a systemic effect of these drugs

ADVANCED SOLAR ASSISTED DESICCANT AND EVAPORATIVE COOLING SYSTEM EQUIPPED WITH WET HEAT EXCHANGERS

This work concerns an innovative solar assisted desiccant and evaporative cooling (DEC) system for building air conditioning. In this system, air-to-air packaged wet heat exchangers are used to maximise the exploitation of the evaporative cooling potential associated with the exhaust air stream. The thermodynamic cycle is first theoretically described, and then an example of a real application is shown. The system presented is an experimental DEC system originally installed at the beginning of 2008 at the Solar Laboratory of the University of Palermo and recently modified and updated. These modifications have been implemented with the aim to foster some problems related to the conventional indirect evaporative process and to increase the overall performance of the process. Different energy performance figures, such as thermal and electrical COP, are presented and discussed. The obtained results are very positive, showing that DEC systems can benefit from the use of wet heat exchangers to efficiently cool the air stream after the adsorption process in the desiccant wheel without any change in moisture content

Energy performance evaluation of a demo solar desiccant cooling system with heat recovery for the regeneration of the adsorption material

Since July 2008, a Solar Desiccant Evaporative Cooling (DEC) system has been operating as a test plant at the solar laboratory of the Dipartimento di Energia (ex DREAM) of the University of Palermo. The system is composed of an air handling unit (AHU) designed for ventilation of the laboratory coupled with a radiant ceiling that provides most of the required sensible cooling/heating energy. Flat plate collectors deliver part of the regeneration heat of the desiccant wheel during the summertime and are used for space heating during the wintertime.The system was designed for high humidity loads because of the typical climate conditions at the site and the need to support a radiant ceiling for sensible cooling. A hybrid configuration was chosen that uses two auxiliary cooling coils fed by a conventional compression chiller. One coil is used for pre-dehumidification. The other coil controls the air temperature if the desired supply temperature cannot be reached through indirect evaporative cooling alone. A specific feature of the system is the use of the heat rejected by the chiller to preheat regeneration airflow.The plant was monitored continuously after installation and start up phases were completed. This paper presents instantaneous, daily and monthly energy performance indicators for five summer months and three winter months. Monthly results are also presented and elaborated upon according to a monitoring procedure developed in the framework of the International Energy Agency (IEA) Task 38 " Solar Air Conditioning and Refrigeration" of the Solar Heating and Cooling Programme. Seasonal performance indicators such as electric and thermal COP and primary energy savings for cooling and heating operation are presented. It was found that about half of the total cooling energy delivered by the AHU was covered by the DEC process. Primary energy savings in summer, in comparison to a conventional AHU, came up to nearly 50%.The recovery of the heat rejected by the refrigerator was found as a good solution, permitting to reduce solar collector area in the design phase.Finally, main issues arisen from plant monitoring and possible solutions to enhance its energy performances are discussed

Second generation of freescoo Solar DEC prototypes for residential applications

Freescoo is an innovative all-in-one compact solar Desiccant Evaporative Cooling (DEC) air conditioner concept. Results of the first prototype developed were presented at SHC Conference last year. Now a second generation of freescoo prototypes for applications in residential and small office buildings have been installed in Italy at ENEA Casaccia and at UNIPA. The thermodynamic cycle is based on the use of fixed and cooled adsorption beds and advanced evaporative cooling concepts. The adsorption bed, which is a fin and tube heat exchanger packed with silica gel grains, allows simultaneous dehumidification and cooling of the process air. The indirect evaporative cooling process, operated downstream to the dehumidification, is realized using an optimized configuration with two wet plate heat exchangers connected in series. Low wet bulb temperatures reached on the secondary flow, allow supply air temperatures to the room below 20°C. Systems are designed also for stand-alone operation thanks to a battery accumulator and PV cells installed. No auxiliary device is used for cold production. The main features of the second generation prototype system are first discussed, as well as some optimizations carried out from the first to the second generation prototype. Results are related both to field monitoring data. Performance indicators such EER and thermal COP, maximum cooling power achieved, stand alone operation data and control issues are presented and discussed

Monitoring Results and Energy Performances Evaluation of Freescoo Solar DEC Systems

This work addresses the energy saving performances of some solar Desiccant and Evaporative Cooling (DEC) systems working with the freescoo technology. The innovative freescoo concept is based on the use two fixed and cooled adsorption beds and advanced indirect evaporative cooling processes. The main feature of this new adsorption bed concept is to allow the simultaneous dehumidification and cooling of air. The systems analyzed have been installed in Italy last here and results based on field monitoring data are here presented. A description of the monitored systems and comparisons between the energy performances based on the main performance indicators such as EER, thermal COP, cooling power, off grid operation data are shown

Life cycle performance assessment of small solar thermal cooling systems and conventional plants assisted with photovoltaics

Starting from the results of a Life Cycle Assessment of small solar assisted heat driven chillers, the application of such methodology has been extended to systems with a conventional compression chiller assisted by a photovoltaic plant (PV). This study aims to provide a comprehensive compared investigation of these two families of solar assisted cooling systems (with solar thermal or PV). Results indicate that, in many cases, the systems with the PV grid connected plant performed best. In addition, two more configurations were investigated to further define the PV assisted systems, which minimise their interaction with the grid through the use of electricity storages. These systems performed worse than the PV grid connected systems and the solar thermal assisted systems in nearly all the analysed cases. 2013 Elsevier Ltd. All rights reserved

Life Cycle Assessment Performance Comparison of Small Solar Thermal Cooling Systems with Conventional Plants Assisted with Photovoltaics

Abstract Life Cycle Assessment (LCA) allows for the consideration of energy consumption and environmental impacts associated with all the stages of a product's life, from the cradle to the grave . Starting from the results obtained in the IEA SHC Task 38 framework for the LCA of small solar assisted heat driven chillers, the application of such methodology has been extended to systems with a conventional compression chiller assisted by a photovoltaic plant. This study aims to provide a more comprehensive investigation through a comparison of these two families of solar assisted cooling systems (with solar thermal or PV), which is an important topic for studies concerning the research of effective and environmentally friendly systems that exploit solar radiation for cooling and heating purposes. In hot climates, the systems with the PV grid connected plant performed best. Anyway, a comparison of this system with the other systems is not meaningful because the strength of the solar thermal H/C system is the ability to reduce the dependence from the electric grid and to avoid peaks, overloads and power quality variations. Thus, two more configurations were investigated to further define the PV assisted systems, which minimise their interaction with the grid through the use of electricity storages. These systems performed worse than the PV grid connected systems and the solar thermal assisted systems in nearly all the analysed cases