CONCENTRATING SOLAR THERMAL COLLECTORS FOR COOLING OF BUILDINGS: AN ASSESSMENT FOR GREECE

Transcription

1 CONCENTRATING SOLAR THERMAL COLLECTORS FOR COOLING OF BUILDINGS: AN ASSESSMENT FOR GREECE Vassiliki DROSOU, Elli KYRIAKI, Argiro DIMOUDI, Agis M. PAPADOPOULOS

2 Concentrated solar thermal (CST) systems principles CST use a combination of mirrors or lenses to concentrate direct beam solar irradiation to produce heat, electricity or fuels. CST use only direct sunlight (DNI, Direct Normal Irradiance), i.e. the fraction of solar radiation that is not reflected by clouds, fumes and dust in the atmosphere and reaches the Earth's surface as a parallel beam. CST reach medium ( C) and high level temperatures (> C), depending on the technology used and the application needs.

3 Concentrated solar thermal (CST) technologies

4 Solar cooling principles Solar cooling technology is based on the use of solar thermal energy for producing cold water in the appropriate temperature level for space cooling purposes. The cooling needs of a building coincide with high solar radiation. The main advantages of solar cooling systems are: - the avoidance of using conventional resources, - the use of environmentally friendly working fluids, - their ability to be installed as stand-alone systems or in combination with conventional cooling systems, - their contribution to electricity consumption stability of a country / energy security / reduction of conventional sources consumption / CO 2 emissions. Commercial solar cooling systems can be classified into "closed systems" which have solar chillers providing cold water for the air conditioning of a building and "open systems" (air), based on the technology of evaporative cooling and dehumidification (DEC: Desiccant Evaporative Cooling).

5 Schematic diagram of a "closed" solar cooling system A typical solar cooling system consists of the solar field, the ab- or adsorption chiller, the thermal storage, the secondary hydraulic equipment (cooling tower, pumps, heat exchangers, piping, valves) and the control system.

6 Building envelope s energy performance characteristics Α typical residential building which consists of three floors and a basement, built in 1997, with a total heated area of 400m 2.

7 Energy performance characteristics 35 typical residential buildings Solar Village 3, Athens, Greece, 1990

8 Buildings cooling needs, with respect to location 255 CDD 24 o C 368 CDD 24 o C 415 CDD 24 o C

9 CST collector technical characteristics

10 CST solar field technical characteristics

11 Solar chiller technical characteristics Broad two-stage steam solar chiller, model BYS100, Nominal cooling capacity 1.163kW.

12 Simulation results Cooling capacity versus DNI Thessaloniki Athens Heraklion

13 Simulation results Thermal energy output versus cooling energy Thessaloniki Athens Heraklion

14 Simulation results & comparison of simulated and published results Case A: simulation study Case B: published results, SAC with flat plate

15 Conclusions Solar cooling can become a promising solution for the clean, energy thrifty and sustainable air-conditioning of urban buildings CST collectors use can yield significantly higher useful thermal output than flat plate collectors CST allow the use of two-stage sorption systems that operates with a significantly higher COP than the single stage. CST systems can be beneficial, when it come to utilizing a given, limited, available area of installation (eg the building s flat roof) for low and medium temperatures. CST systems have to be part of an integrated whole solar approach, covering space heating and cooling and also hot water production.

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