The Most Recent Development of Desiccant Cooling

Peter Novak School of Technologies and Systems, Novo mesto, Slovenia The Most Recent Development of Desiccant Cooling Review pa per UDC: 620.97:621.57 Desiccant cool ing is be com ing more and more im por tant to pre vent ex po nen - tial rise of elec tric ity con sump tion for air con di tion ing sys tems (ACS). Grow ing use of ACS is ex pected be cause of global warm ing. Us ing stan dard re frig er a tion equip ment and pop u lar split ACS the elec tric ity con sump tion will go up. There are two pos si bil i ties: to pro duce more elec tric ity from re new able, to cover the grow ing de mand or change the cool ing tech nol ogy. To com pete with high ef fi - ciency elec tri cal driven re frig er a tion sys tems a new break trough is needed in old desiccant and ad sorp tion cool ing sys tems. Us ing the so lar or waste en ergy as driv ing force of these sys tems we are fac ing also with the cold stor age prob lems. In the pa per the over view on re cent de vel op ment in these fields in USA and Eu - rope is pre sent ing. Key words: re new able en ergy, desiccant, cool ing, equip ment, sys tems In tro duc tion Room air-conditioning (RAC) is groov ing with the stan dard of pop u la tions, groov ing out door tem per a ture, and sink ing prices for the equip ment. Se rial pro duc tion of RAC units split, multi-split, cen tral ized chilled wa ter tech nol ogy are used ev ery where, de pend ing on the cli mate and build ing ther mal qual ity. The num ber of sold units of RAC has al most lin ear growth in last 10 years ap proach ing in 2008 50 mil lion units per year. Many negative impacts on electricity consumption, urban degradation and CFC emis sions have been de tected. In or der to limit these neg a tive im pacts, new en vi ron men - tally sound con cepts of cool ing for ap pli ca tion in the small ca pac ity range are of par tic u lar importance. The use of ther mal driven cool ing sys tem (ab sorp tion, sorp tion desiccant, open or close cy cles) can be a pos si ble so lu tion among oth ers. Ac cord ing to the EU de ci - Au thor's e-mail: pe ter.novak@energotech.si 31

sion to use more re new able en ergy sources, the so lar as sisted cool ing is be com ing more im por tant. The ad di tion of desiccant com po nents to an HVAC sys tem di rectly re moves the wa ter va por (la tent heat) from the air, over com ing in her ent dehumidification lim i ta - tions of cool ing coils. Desiccants en able in de pend ent con trol of tem per a ture and hu mid - ity, im prov ing HVAC sys tem ef fi ciency by free ing di rect ex pan sion cool ing com po nents to run at more ef fi cient op er at ing points. They can pro vide free re heat and also con trol hu mid ity in the shoul der sea sons when cool ing coils are in ef fec tive and al low in door mois ture to per sist. Desiccant cool ing sys tems can be in te grated with new evap o ra tive heat re jec tion com po nents that not use CFC and HCFC re frig er ant, which are cur rently banned and re stricted. The use of desiccant and other ther mally re gen er ated sorbents in build ings can also im prove, and in some cases, elim i nate air borne par ti cles and gases that cause sick-build ing syn drome, dust mites, and over all dis com fort in build ing en vi ron - ment [1]. In cor po rat ing desiccant com po nents as an in te gral part of onsite power, heat - ing, and cool ing equip ment will save en ergy and im prove the per for mance of the en tire energy delivery system (CHP). In most oc ca sions the cool ing load and so lar gains oc cur at more or less the same time. Use of so lar en ergy in desiccant sys tems is ob vi ously. The IEA Tasks 25 and now 38 So lar AC and Re frig er a tion wants to con trib ute to the pro cess for an accelerated market introduction of solar air-conditioning and refrigeration. Thermally driven technology is of particular interest in case of application where solar collector can con trib ute to the heat ing and cool ing and can be used year around. Pres ent state-of-the- -art of so lar cool ing tech nol ogy is still in its in fants phase. In fig. 1 the world wide dis tri bu - tion of the cool ing power as sisted by so lar en ergy con firm this con clu sion (Sparber 2007, [2]). High ef fi cient and low cost RAC have the big ad van tage of heat trans fer by phase change, us ing rel a tively small amount of exergy (elec tric ity in av er age 1 kw for 4 kw of cooling power). So lar heat for ther mally driven cool ing pro cess has to en able chilled wa ter or con di tioned air to the build ing. Dif fer ent tech nol o gies are avail able for heat sup ply, stor - age, and heat re jec tion (fig. 2). All need to be op ti mized and cost ef fec tive. 32 Fig ure 1. World wide dis tri bu tion of the cool ing power as sisted by so lar en ergy (Sparber 2007, [2])

Fig ure 2. So lar heat can be used for ther mally driven cool ing pro cess for build ings AC on dif fer ent ways Principles Desiccant cool ing sys tems are very old tech nol ogy in the past with any com pet i - tive advantage to the compressor cooling systems. The basic principles and materials pair are known for de cades. No break through was achieved in last five years. The types of sorp tion ma te ri als used as a ba sis for desiccant sys tems in clude the fol low ing: sil ica gel; lith ium chlo ride (liq uid or dry), highly cor ro sive; lith ium bro mide, cor ro sive; ac ti vated alu mina; ti ta nium sil i cate; mo lec u lar sieve (zeolites, etc.); poly mer desiccants membranes. Huge ma te rial re search and de vel op ment is needed to im prove the ther mal and ad sorp tion char ac ter is tics of dif fer ent pairs (wa ter in open and closed cy cles and dif fer ent other heat transfer medium (methanol, ethanol, etc.). Ex pec ta tions to in clude the new achieve ments in ma te rial sci ence us ing the nanotechnologies for de sign a new sorp tion pairs are great. Look ing on equip ment and sys tem site, we still have only stan dard old five tech nol o gies or con fig u ra tions: liq uid spray tow ers, solid packed tow ers, ro tat ing hor i - zon tal bed, mul ti ple ver ti cal bed, ro tat ing desiccant wheels and poly mer desiccant mem - branes. For each of that equip ment we can find some ad van tages and dis ad van tages. Liq uid spray tow ers This type of tow ers are based on liq uid desiccant. Liq uid desiccant sys tems have a num ber of fea tures that make them uniquely prom is ing. They can make ef fec tive use of low tem per a ture waste heat that other tech nol o gies can t, like cool ing wa ter from en gine gen er a tor sets, and pro ton-ex change mem brane fuel cells. Pro cess air passes trough a desiccant spray in a con di tioner mod ule. In re gen er a tion pro cess the out side air passes trough a warm desiccant spray in a re gen er a tion mod ule. There are some ad - van tages as: large air flow ca pac ity, mod u lar de sign, pro vides mi cro bi o log i cal de con - tam i na tion, re duce re- gen er a tion air re quire ment, en ergy stor age ca pa bil ity (hold ing tanks can be used to pro vide ex cess ca pac ity), desiccant qual ity can be eas ily mon i tored 33

Conditioner Regenerator and ad justed, no pos si bil i ties of cross leak age of air streams, air tem per a ture, and hu mid ity are con trolled si mul ta - neously. But there is also disadvantage to main tain the low hu mid ity at loads with small sen si ble com po nent (fig. 3). Solid packed tow ers Fig ure 3. Liq uid spray tow ers Fig ure 4(a). Solid packed tow ers Based on solid desiccant. Pro cess air passes trough a tower filled with solid desiccant and re gen er a tion air passes trough the sec ond tower with solid desiccant. Tow ers al ter nate be tween per - form ing the pro cess. Air path are chang - ing be tween two tow ers. Ad van tage is to be able achiev ing very low dew points. Dis ad van tages are: out put con di tions vary with level of mois ture trapped, air ve loc - ity is crit i cal for op ti mal per for mance, large pres sure drop (fig. 4). Special solution is integrated compact two chambers adsorption desiccant chiller with in te grated HEX-s in adsorber and desorber, figs. 4(a) and 4(b). In fig. 5 the ex per i men tally achieved COP for dif fer ent work ing pairs and fir ing wa ter tem per a ture is pre sented (GBU Ad sorp tion Chiller, 1996). Fig ure 4(b). Com pact two cham ber desiccant chiller design Fig ure 5. Vari a tion of COP with the variation of firing water temperature and different working pair 34

Rotating horizontal bed They are based on solid desiccant. Pro cess air passes trough per fo rated trays where the desiccant is held. The trays ro tate trough pro cess air path and regeneration air path. Ad van tages of de - sign are: mod u lar de sign, con stant out let mois ture level, high air flow ca pac ity ca - pa bil ity, lower first costs, and sim ple de - sign. Dis ad van tages: desiccant set tling in trays, air leak age be tween pro cess air and re gen er a tion air within the trays (fig. 6). Fig ure 6. Ro tat ing desiccant wheel Mul ti ple ver ti cal beds They are based on solid desiccant. Desiccant is held by stacked per fo rated trays that the air passes trough. For re - gen er a tion pro cess part of stacked per fo - rated trays is used. This is a com bi na tion of packed tow ers and ro tat ing bed de sign trough the use of a ro tat ing car ou sel of many tow ers. Ad van tages are: con stant out let mois ture level, high per for mance, low dew points. Dis ad van tages are: com - plex mechanical system, increased main - te nance, higher first costs (fig. 7). Fig ure 7. Mul ti ple ver ti cal beds Rotating desiccant wheel Desiccant wheel are based on solid desiccant. Pro cess air passes trough hex - agonal or sinusoidal shaped passages of the wheel. Part of the wheel is used as re - gen er a tor. Desiccant is im preg nated into semi-ce ramic struc tures that re sem ble a honeycomb. Ad van tages are: light weight and po rous struc ture, low pres sure drop across the wheel, low dew points, high ca - pac ity, and sim ple sys tem. Dis ad vantage: higher first costs (fig. 8). Figure 8. Rotating desiccant whell 35

Poly mer desiccant mem branes In PEM fuel cells re search on mem branes is in par al lel re search ori ented also to pro duce a desiccant mem brane ca pa ble of trans fer ring mois ture nearly as well as met als trans fer heat. These mem branes re tain the mois ture trans port abil i ties of their fuel cells coun ter part but don t re quire their unique elec tri cal prop er ties, so they are more straight for ward to pro duce. Some in sti tute and in dus try are pre par ing the coun ter flow plate heat exchanger that re cover more than 75% of the heat and mois ture from waste heat en ergy flow. This can be a re place ment for heat-only re cov ery de vice and per forms as well as ro tary exchanger, but with out mov ing parts. This novel poly mer is unique in its abil ity to at tract, trans port, and re ject wa ter va por while re main ing im per me able to other gas mol e cules. They can be used also as con tain ment of liq uid desiccant and shows great prom ise in de vices that uti lize the pow er ful dry ing abil ity of ionic salt so lu tion, while re - sist ing their cor ro sive ef fect and com pletely elim i nat ing the pos si bil ity of their en train - ment into the de hu mid i fied air stream [3]. Thermodinamics of desiccant sys tems The COP is de fined as the use ful cold pro duc tion per unit of driv ing heat: COP = Q cold Q heat (1) The first and sec ond law of ther mo dy nam ics ap plied to the ba sic pro cess of a ther mally driven chiller lead to ex pres sion for the max i mum pos si ble COP id in which COP is only de pend ent of three tem per a ture lev els: COP id T T C H T T H M T M T C (2) where the tem per a tures are: T C cold source (use ful cool ing tem per a ture), T H driv ing heat temperature, and T M in ter me di ate level heat re jec tion tem per a ture. The COP cal cu lated ac cord ing to eq. 2 gives the up per ther mo dy namic limit, which can never be achieved in prac tice. In fig. 9 the ideal and real COP as func tion of the driving temperature for most common heat driving cooling technologies for selected T C and T M are pre sented. It is ev i dent that ad sorp tion sys tems can be op er ated with some what lower tem per a tures than sin gle ef fect ab sorp tion, but they achieve also lower COP val ues. The in flu ence of both on the COP at con stant Carnot efficiency factor (CEF) is pre sented in fig. 10. CEF is the quo tient be tween real COP r and ideal COP id at the same con di tions: x Car not = COP r /COP id (3) 36

Fig ure 9. COP Curves of sorp tion chill ers and the up per ther mo dy nam ics limit (ideal) ac cord ing to eq. 2 for T C = 9 C and T M = 28 C (Henning, [4]) Fig ure 10. Real COP at CEF 0.3 for different cooling water outlet (T C ) and heat rejection temperature (T M ) at T H = 60 C The CEF lies in the range of 0.3 to 0.4 for com mon sys tem on the mar ket (fig. 11). It can be in creased by dif fer ent mea sures (ef fec tive heat trans fer, in creased heat re - covery, etc.). For a given ap pli ca tion (AHU for AC, chilled beams, fan coils) the chilled wa ter tem per a ture T C is de fined. Cli ma tic con di tions de fined the heat re jec tion tem per a ture T M. The tem per a ture dif fer ence DT be tween these two tem per a tures is called the use ful tem per a ture drop (in some lit er a ture tem per a tures lift): DT = T M T C (4) Necessary driving temperature T H for given tem per a ture drop DT can be cal cu - lated on the base of pre vi ous equa tions: TC T T TH (5) COP T 1 C Carnot Fig ure 11. Car not ef fi ciency fac tor vs. use ful temperature drop (lift) Dt for com mer cial avail able ther mally driven wa ter chill ers (Henning, [4]) 37

In the case we will use the so lar en ergy as the driv ing heat; in the fig. 12 (a) the so - lar col lec tor tem per a ture are plot ted against use ful tem per a ture drop (lift) for two dif fer - ent val ues of COP (0.7 and 1.1) and CEF (0.3 and 0.4). Figure 12(a). Required heat source temperature for different COP/REF combinations as func tion of the use ful DT, typ i cal so lar col lec tor tech nol o gies are in di cated (Henning, [4]) Real col lec tor ef fi ciency at given driv ing tem per a ture and most com mon heat driven tech nol o gies are pre sented in fig. 12(b). For desiccant cool ing any type of sollar col lec tors can be used with very high ef fi ciency be tween 55 to 70% at work ing point. Dry desiccant sys tems On the left side of fig. 13 is pre sented a typ i cal so lar as sisted desiccant sys tem and on the right side the desiccant cy cle psychometrics. In door air (5) is hu mid i fied to (6), re - heated in heat re cov ery wheel to (7), and heated by aux il iary heater (gas, waste heat or so - lar en ergy to (8). Pass ing the hu mid i fier take out the mois ture and leave the sys tem with the state (9). Out door hu mid air (1) passes first the dehu mid i fier where the desiccant re - moves moister from the air, which re lease heat and raises the air tem per a ture to (2). The air is then cooled in heat re cov ery wheel (3) and on the end adi a batic hu mid i fied near to the sat u ra tion point (4). The prin ci ple is very old and is be com ing im por tant again in last years be cause the sys tem is work ing with out ozone de plet ing re frig er ant and elec tric ity. In such one sys tem the la tent and sen si ble heat are han dled more ef fi ciently than in va por com pres sion sys tem, be cause the com po nent can be op ti mized to in de pend ently re move these sep a rate loads. Op ti mi za tion of the heat trans fer in heat re cov ery wheel and 38

Fig ure 12(b). Ef fi ciency of dif fer ent so lar col lec tors at 800 W/m 2 used as en ergy source for heat driv ing cool ing sys tem Curve des ig na tions on the pic ture are used for: (a) sin gle glazed flat plate with AR; (b) evacuated tube collector; (c) CPC flat plate col lec tor with tef lon foil; (d) flat plate col lec - tor with dou ble AR glaz ing and in ert glass fill ing; (e) small par a bolic trough (only direct irradiation of 600 W/m 2 ) moisture transfer in dehumidifier wheel is go ing on for many years, but the suc cess is lim - ited. New approach using new technologies in material-engineering (nano-technologies, molecular technologies, etc.) is needed to make this sys tem en ergy and costs ef fi cient. Because conventional vapor compression cooling systems are not designed to handle temperature and humidity separately, oversized compressors are often installed to de hu mid ify the in com ing air. Desiccant AC sys tems can be ap plied in dif fer ent modes. Fig ure 13. Typ i cal desiccant sys tem and his psychometrics 39

In many cases the stan dard ar range ment of two wheels, be cause of ir re vers ibil ity s, can not sat isfy the re quired in door con di tions. If the de hu mid i fied and cooled air dew point is too high, ad di tional cool ing is nec es sary (mostly with va por com pres sion sys tems). To solve this prob lem the pat ented so lu tion with pri mary air di vi sion in two streams is pro - posed (Archibald, DES-EVAP [9]). Sys tem is pre sented in the fig. 14. To achieve the point D with lower dew point, ad di tional cool ing from point C to C is needed. The so lu - tion is to use part of dried and cooled out door air in in di rect adi a batic cooler in stalled in pri mary air stream. If this prin ci ple is ap plied with so lar air col lec tors in te grated in the roof, very ef fi cient and sim ple sys tem, mostly for sin gle homes can be build. Fig ure 14. So lar as sisted DES-EVAP desiccant cycles with additional indirect evaporative cooler (Archibald, pat ented, [9]) in sys tem with re gen er a tion heat from so lar roof (air so lar col lec tors and waste heat used also for do mes tic hot wa ter) The next in no va tion on desiccant sys tems in last years is also the pro posal of Dai et al. [10]. To make so lar as sisted desiccant sys tem more ef fi cient, or better to say, ap pli ca - ble for the stan dard flat plate so lar col lec tors, they pro pose two stage cool ing sys tem. Scheme of such sys tem and psychometrics is shown in fig. 15. Ex per i men tal re sults con firm high COP of the sys tem, near to 1.0 with driv ing so lar heat tem per a tures un der 80 C. COP of so lar sys tem is ap proach ing 0.5, which is one of the high est. Liq uid desiccant sys tems As we have men tioned be fore, the liq uid desiccant sys tems, many times des ig - nated as ad sorp tion sys tem (USA, Eu rope) are in many ap pli ca tion more con ve nient. Many new con cept and heat trans fer so lu tion has been de vel oped in last years. Those, hav ing com mer cial or near com mer cial ap pli ca tion will be dis cussed in the pa per. 40

Fig ure 15. Two stage so lar driven desiccant sys tem (Dai et al., [10]) Liquid desiccant conditioner and regenerator are traditionally implemented as adi a batic beds of con tact me dia that are highly flooded with desiccant. The pos si bil ity of drop let car ry over into sup ply air and con nected cor ro sion in ducts or even in AC rooms has lim ited the use/sale of these sys tems. To pre vent drop let car ry over a spe cial low flood - ing rates heat exchanger was de vel oped with si mul ta neous heat and mass ex change. This is ac com plished by us ing the walls of par al lel-plate plas tic heat exchanger as the air/desiccant con tact sur face. Com pared to ex ist ing solid and liq uid desiccant sys tsems, the low-flow tech nol ogy is more com pact, has sig nif i cantly lower pres sure drop, and does not dump heat back onto the build ing s cen tral air con di tioner. Test con firm the high sen si ble and la tent ef fec tive ness of the con di tioner, the high COP of the re gen er a tor, and the op er a tion of both com po nents with out drop let of desiccant car ry over. The figs. 16 and 17 shows the de sign and ex per i men tal re sults. Fig ure 16. Op er a tion of the low-flow liq uid desiccant air con di tioner (left), re gen er a tor (mid dle), cross-sec tion of plas tic plate (2.5 305 mm) with wick 0.5 mm for equal dis tri bu tion of desiccant over the HEX sur face (next), and con di tioner (right ~10.000 m 3 /h), (Lowenstein et al., [14]) 41

Fig ure 17. Wa ter re moval and COP of a low flow re gen er a tor (left) and per for mance of the low flow regenerator with heat recuperation (right), (Lowenstein et al., [14]) Sim i lar re search is go ing on in Ger many [16]. De signed sim i lar HEX/ /con di - tioner with ex per i men tal val i da tion of sim u la tion re sults are shown on fig. 18. New desiccant exchanger de sign with packed desiccant has been tested in CEA-INES by Demasles et al. [17]. Us ing this type of conditioner authors pro - posed also the so lar cool ing scheme with two al ter nat - ing round HEX (figs. 19 and 20). Compact adsorbtion liq uid desiccant chill ers has been de vel oped in In dia and Ger many. First for ag - ricultural product cooling Figure 18. Protype of novel HEX/regenerator (Krause et al., [16]) Fig ure 19. Spe cial HEX with desiccant sil ica gel par ti cles be tween finned sur face 42

Fig ure 20. So lar desiccant cool ing in stal la tion sheme with in te grated HEX-H (Demasles et al. [17]) and sec ond for AC. The first one is in the figs. 4 and 5, the sec ond de sign is shown in fig. 21, left. Very in ter est ing is the HEX de sign us ing sil ica-gel coated HEX sur face, (fig. 21, right). Sorp tion with metal hy dride Two dif fer ent metal hy dride are cou pled in spe cial re ac tion beds for hy dro gen ex change. The metal hy dride has to be cho sen to match the re quired tem per a ture bound - ary con di tion for the cool ing sys tem. Con clu sions Fig ure 21. In ter nal con struction of desiccant adsorption chiller (right) and sil ica-gel coated tube and fin ab sorber HEX Driv ing heat source for the desiccant sys tems can be: any waste heat with T > 50 C and solar energy. Driving temperature strongly depend on required cooling temperature. 43

Figure 22. Hydrogen exchange between two coupled reaction beds (Lindner et al., Murthy, [21, 22]) Heat rejection temperature (T M ) has great in flu ence on COP. Dry sys tems are les con ve - nient for heat ex change as wet sys tem. All-air sys tems with desiccant wheels are ap pro pri - ate for so lar air sys tems if de signed for low flow, low pres sure drop. Liq uid desiccant sys tems are more com pact, en able some stor age ca pac ity. Stor age is un solved prob lem in all low exergy cool ing sys tems. All air sys tems are not ap pro pri ate for the stor age, ex cept the stor age in the build ing mass or on driv ing heat stor age (so lar wa ter stor age). Sys tems with liq uid desiccant have the ad van tage to store the strong so lu tion at room tem per a ture with no loss as long as needed. Stor age vol umes are large and ex pen sive. Un til now there is no com pet i tive so lu tion to the ice stor age. The metal hy dride is chal lenge, but the tem per a - ture range is over 100 C and re search is needed to find the prac ti cal so lu tions. Heats driv - ing desiccant cool ing sys tem are in fast de vel op ment. Dry, mostly ro tary wheels, sys tem, are on the mar ket. Com pet i tive ness with com pres sor driven cool ing sys tem is not yet achieved. Sys - tems are bulky and not re li able as the com pres sor sys tems. Heat trans fer in all air sys tems is low, HEX are large. Liq uid desiccant sys tem (low flow and sim i lar) with stor age pos si - bilities are appropriate for all tipe of driv ing heat (so lar and waste heat) and shows some ad van tages against wheels sys tem. En ergy ef fi ciency of new desiccant sys tems for low exergy cool ing can be higher as stan dard ab sorp tion sys tem. There is no so lu tion yet for re place ment of small room air con di tioner RAC split sys tems. Only large, cen tral ized ven ti la tion and AC sys tem can be the place for use of dry or liq uid desiccant sys tem in near fu ture (es pe cially in low en ergy build ings). Ref er ences [1] ***, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Condi - tion ing, 2007, Tarragona, Spain 44

[2] Sparber, W., et al., Overwiew on World Wide In stalled So lar Cool ing Sys tems, OTTI In tro - duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 76 [3] ***, IEA Task 38, http://www.iea.org [4] Henning, H. M., Morgenstern, A., Solar Air-Conditioning and Refrigeration Collaborative Work in Task 38 of the IEA So lar Heat ing & Cool ing Programme, OTTI In tro duc tion, Pro - ceed ings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 15 [5] Henning, H. M., et al., Thermodynamic Analysis of Sollar Ther mally Driven Cold Pro duc tion, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 42 [6] ***, US Army Constr. Eng. Re search Lab., Desiccant Cool ing Tecnology, Re source Guide, 2000 [7] ***, NREL Dis trib uted Ther mal En ergy Technologies, www.enrel.gov. [8] Singh, J., Desiccant Cool ing, AIE Pvt. Ltd., In dia [9] Archibbald, J., A New Desiccant Evap o ra tive Cool ing Cy cle..., Am. So lar Roof ing Co. ASHRAE Trans ac tion 2005, 2006 [10] Dai, Y., et al., De vel op ment of a Novel Two-Stage So lar Dessiccant Cool ing Sys tem Driven by So lar Air Col lec tor, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference So lar Air-Con di tion ing, 2007, Tarragona, Spain, No. 21 [11] Höfker, G. et al., Desiccant Cool ing with So lar En ergy, Ph. D. the sis, Uni ver sity of Leicester, Leicester, UK, 2001 [12] Hess, S., Application of Medium Temperature Collectors for Solar Air-Conditioning, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 31 [13] Olliveti, G. et al., En ergy Per for mances of a Plant Us ing an Ad sorp tion..., OTTI In tro duc - tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 57 [14] Lowenstein, A., A Zero Car ry over Liq uid-desiccant Air Con di tioner for So lar Ap pli ca tions, ASME/SOLAR06, 2006, Den ver, Col., USA [15] ***, AIL Researh: OA6000 A Liq uid-desiccant Ded i cated Outdoor Air Sys tem, http://www.air.com [16] Krause, M., Validation and Comparison of Absorber and Regenerator..., OTTI In tro duc - tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 94 [17] Demasles, H., et al., Numerical and Experimental Studies of a Novel Absorber Heat Exchanger for Desiccant So lar Air Con di tion ing, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 17 [18] Mittelbach, W., Büttner, T., Com pact Ad sorp tion Chill ers with Coated Adsorber Heat Exchanger, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Con di tion ing, 2007, Tarragona, Spain, No. 125 [19] Mand, S., et al., De vel op ment of an Ad vanced So lar-hy brid Adsorbtion Cool ing, Tata En - ergy Re search In sti tute, New Delhi, 1997 [20] Linder, M., et al., Sorp tion Air-Con di tion ing Sys tem Based on Metal Hy drides, OTTI In tro - duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 89 [21] Murthy Srinivasa, S., Metal Hy dride Based Cool ing Sys tems with Hy dro gen as Work ing Fluid, OTTI In tro duc tion, Proceedings on CD, 2 nd International Conference Solar Air-Conditioning, 2007, Tarragona, Spain, No. 124 45

Apstrakt Pe ter NOVAK Visoka {kola za tehnologije i sisteme, Novo Mesto, Slovenija Najnovija dostignu}a u razvoju sorpcionog hla ewa Sorpciono hla ewe postaje sve va`nije u spre~avawu eksponencijalnog porasta potro{we elektri~ne energije u sistemima za klimatizaciju. Zbog globalnog zagrevawa se o~ekuje porast kori{}ewa sistema za klimatizaciju. Kori{}ewe standardne rashladne opreme i popularnih split-sistema za klimatizaciju }e uzrokovati porast potro{we energije. Postoje dve mogu}nosti: proizvesti vi{e elektri~ne energije iz obnovqivih izvora da bi se pokrila pove}ana potra`wa ili promeniti tehnologiju hla ewa. Zbog konkurencije visoko-efikasnih elektri~nih rashladnih sistema, potreban je novi napredak u razvoju starih sorpcionih i adsorpcionih rashladnih sistema. Kori{}ewem energije Sunca ili otpada kao pogonske sile ovih sistema, tako e se suo~avamo sa problemima skladi{tewa rashladne energije. U ovom radu je prikazan pregled skora{weg razvoja u ovim oblastima u SAD i Evropi. Kqu~ne re~i: obnovqiva energija, sorpcija, hla ewe, oprema, sistemi Elektronska adresa autora: pe ter.novak@energotech.si Pa per sub mit ted: Feb ru ary 20, 2010 Pa per ac cepted: March 8, 2010 46