A.K. Lalzad*, I.W. Eames**, P. Panayiotou***, G. Maidment* and T.G. Karayiannis*
* School of Engineering Systems and Design, South Bank University, 103 Borough Road, London SE 1 OAA,
** Institute of Building Technology, University of Nottingham, University Park, Nottingham, NG7 2RD,
*** Dept. of Mechanical Engineering, University of Sheffield

The availability of fresh water is imperative for the development of every country. The cost of purchasing, operating and maintaining conventional desalination plants is beyond the reach of many developing countries. Hence, there is an urgent demand for new methods of water production in order to satisfy current needs. Suitable plants for these countries must be of low capital and operating costs, simple in operation and maintenance and make use of a non-conventional energy input source, at satisfactory efficiency levels.
This paper presents an innovative solar energy driven distillation system working at low pressure. The novelty of the process lies in the reduction of the pressure due to the height of the evaporator which is 10m, allowing a much reduced grade of energy required to operate the cycle. In a real plant, solar energy can be utilised, thus eliminating the need for conventional thermal energy input. The use of low-grade solar energy for desalination processes is likely to play an increasingly important part in the production of drinking water and in places where high insolation is available and conventional energy sources are prohibitively expensive.

S. Halliday⁽¹⁾, C.B. Beggs⁽²⁾ and P.A. Sleigh^(2)
(1) GAIA Research, The Monastery, 2 Hart Street Lane, Edinburgh, EH1 3RG, UK
⁽²⁾ School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK

The desiccant cooling cycle is a novel open heat driven cycle which can be used both to cool and dehumidify air. Being a heat driven cycle, desiccant cooling affords an opportunity to utilise heat which might otherwise be wasted. It can therefore be coupled to solar collectors to produce a cooling system which, in theory, should be extremely environmentally friendly. This paper discusses the feasibility of using solar energy to power the desiccant cooling cycle and also presents the results of a recent study, in which a solar desiccant cooling model is used to evaluate a theoretical installation located in the southeast of England. The paper demonstrates that solar powered desiccant cooling is a feasible solution for cooling and heating buildings in the United Kingdom (UK).

F. Buchter¹, C. Hildbrand¹, Ph. Dind¹, and M. Pons^2
1 Laboratoire d'Énergétique Solaire, EIVD (HES-SO), 1, route de Cheseaux, CH-1400 Yverdon-les-Bains, Switzerland
² C.N.R.S.-L.I.M.S.I., BP 133, F-91403 Orsay cedex, France

An adsorptive solar refrigerator has been built and tested in September 2000 in Yverdon-les-Bains, Switzerland. The adsorption pair is silicagel + water. The machine does not contain any moving part, it does not consume any mechanical energy apart from experimental purposes and it is relatively easy to manufacture. The adsorber is altogether the solar collector (flat-plate, 2m², double glazed), the condenser is air-cooled (natural convection) and the evaporator contains 38 litres of water that can freeze into ice. This ice is a cold storage for the cabinet (320 litres). Elements such as valves and graduated bottle are installed only for experimental purposes. Experimental measurements are presented and analysed. Performances of the machine are very promising with a solar cooling COP_s near 0.19. This value is larger than the ones obtained by former solar-powered refrigerators (0.10-0.12) despite some restrictive effects in the evaporation connected with the use of water as refrigerant and cold storage (such effects can be reduced with better design of the evaporator). Moreover, an energy balance of the solar collector shows that the collector efficiency (0.41) is larger than the values (0.3-0.35) published by former experiments.

Keywords : Solar energy, silicagel, water, adsorption, cooling, experiment, double glazed flat-plate solar collector.

Résumé :
Un réfrigérateur solaire à adsorption fut construit et testé durant le mois de septembre 2000 à Yverdon-les-Bains en Suisse. Le couple d'adsorption utilisé est : gel de silice + eau. Le système ne possède aucune pièce en mouvement, ne consomme pas d'énergie mécanique (excepté pour les mesures expérimentales) et est relativement simple de conception. Le système est composé d'un collecteur solaire (capteur plan de 2m², avec double-vitrage) faisant office d'adsorbeur, d'un condenseur à air (convection naturelle) et d'un évaporateur contenant 38 litres d'eau, eau susceptible de geler à l'intérieur de l'évaporateur. Cette glace est un stock de froid pour l'enceinte frigorifique (320 litres). Des vannes et un réservoir gradué sont installés pour l'expérimentation. Les données expérimentales sont présentées et analysées. Les performances du système sont très prometteuses, avec un COP solaire brut atteignant 0,19. Cette valeur est supérieure à celles atteintes par d'autres systèmes de réfrigération solaire (0,10-0,12), ceci en dépit des contraintes liées à la prise en glace de l'eau à l'intérieur de l'évaporateur. De plus, un bilan énergétique du capteur solaire montre que le rendement de captation (0,41) est supérieur aux valeurs (0,3-0,35) obtenues par de précédentes expérimentations.

A. Mortal¹ and L. Roriz² and L. Mendes^2
1 Escola Superior de Tecnologia, EST, 8000-117 Faro, Portugal
² Instituto Superior Técnico, IST, 1049-001 Lisboa, Portugal

This paper presents the simulation of the performance of a small scale water-ammonia absorption heat-pump using solar energy as heat source. The heat-pump is currently being tested at IST and the results show that the system can be used for ambient cooling providing comfort conditions although additional equipment is necessary.

L.L. Vasiliev, D.A. Mishkinis, A.A. Antukh, L.L. Vasiliev Jr.
Luikov Heat & Mass Transfer Institute,
P. Brovka, 15, 220072, Minsk, Belarus

The general goal of this paper is to present the results of an investigation of a new environmentally friendly refrigerator. In this design a physical adsorption and chemical reactions are used simultaneously for a heat and cold generation. A solar refrigerator is made of a solar collector, adsorbed natural gas vessel (ANG), and compact, portable refrigeration system, which consists of two small adsorbers with heat pipe heat recovery system. An active carbon fiber "Busofit" saturated with different salts (CaCl₂, BaCl₂, NiCl₂) is used as a sorbent bed and ammonia is used as a working fluid. The main particularity of this refrigerator is consumption of solar energy with methane gas burner as a back-up.
The system management consists only in actuating the special type valves to change the direction of the heating circuit and water valves to change the water cooling circuit.
The goal of this work is the experimental determination of the main refrigerator parameters using solar/gas high temperature source of energy and air/water as a low temperature source of energy to cool and heat air/water.