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Research Papers

# The AQUASOL System: Solar Collector Field Efficiency and Solar-Only Mode Performance

[+] Author and Article Information
Julián Blanco, Diego Alarcón, Elena Guillén, Wolfgang Gernjak

CIEMAT-Plataforma Solar de Almería. Carretera de Senes s/n P.O. Box 22, 04200 Tabernas (Almeria), Spainjulian.blanco@psa.es

J. Sol. Energy Eng 133(1), 011009 (Jan 28, 2011) (6 pages) doi:10.1115/1.4003291 History: Received September 28, 2008; Revised December 03, 2010; Published January 28, 2011; Online January 28, 2011

## Abstract

Water scarcity is a global problem that will be of capital importance during the first half of this century, when seawater desalination will often be the only way to achieve sustainable development. Despite significant energy efficiency improvements during recent years, seawater desalination is still an intensive energy consumer; therefore, in the current instability of oil prices and environmental requirements, the sustainability of this technological solution inevitably passes through continued improvement of energy efficiency of the physical processes involved, as well as the use of renewable energy resources such as solar energy. In 2006, the “Enhanced Zero Discharge Seawater Desalination Using Hybrid Solar Technology” Project (AQUASOL) concluded with the erection of a complete solar desalination facility at the Plataforma Solar de Almeria (Spain) for the main purpose of developing an improved-cost, energy-efficient multi-effect distillation (MED) solar desalination technology. The system was designed to make the following three desalination operating modes feasible: (a) solar-only: the energy to the first distillation effect comes exclusively from thermal energy from the solar collector field, (b) fossil-only: a double-effect absorption heat pump powered by gas supplies all of the heat required by the distillation plant, and (c) hybrid: the energy comes from both the heat pump and the solar field. In this paper, solar-only mode system performance is presented and discussed. Optimum working conditions achieved in the solar-only mode were in the range of $64–67°C$ of MED first cell inlet temperature, which implies specific thermal energy consumption from around $58 kW hth/m3$ to $62 kW hth/m3$ and a performance ratio of 11.1–10.4, respectively.

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## Figures

Figure 1

Configuration of AQUASOL seawater desalination system

Figure 2

500 m2 stationary CPC AQUASOL solar collector field

Figure 3

Theoretical solar collector field efficiency on different test dates using global solar irradiance measured at the same inclination as the collector field

Figure 4

Measured solar collector field efficiency on different test dates using global solar irradiance measured at the same inclination as the collector field and net thermal energy transferred to the thermal storage tanks

Figure 5

Mean solar collector field efficiency

Figure 6

Front view of the PSA desalination building with the two thermal storage tanks (left) and front view of the PSA MED Plant (right)

Figure 7

Power provided by the solar collector field and MED plant consumption (left axis) on Jun. 25, 2007. Global solar radiation (35 deg inclination over horizontal) is also shown (right axis).

Figure 8

Distillate production from the PSA MED Plant at different seawater feed rates (5–9 m3/h) and different inlet temperatures of hot water from thermal storage tanks (solar energy input)

Figure 9

Performance ratio of the Plataforma Solar MED Plant over first cell inlet temperature (from thermal storage) and linear fit of experimental data

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