Technology International Incorporated 0f Virginia
Kara Establishmnet

Design of a Small Solar-Powered Desalination System

CUSTOMER:  Kara Establishment, Mecca, Saudi Arabia

STARTING DATE: May 1981

DURATION: 3 months

AMOUNT: $150,000

PROJECT MANAGER: Dr. Abdo A. Husseiny

OTHER KEY PERSONNEL: Dr. Ali M. El-Nashar - Dr. B. H. Thrasher

TECHNICAL MONITOR: Mr. Tareq Osman Al-Kasabi, KARA

PUBLICATIONS/REPORTS:

Bowman, T. E., El-Nashar, Ali M., Thrasher, B. H., and Husseiny, Abdo A. (1981).  Design of a Small Solar-Powered Desalination System.  Desalination, 39, 71.

Turnage, Janet J., and Husseiny, Abdo A. (1981).  Assessment of the Market Potential for Small Solar Powered Desalination Plants. Desalination, 39, 43.

SUMMARY

A design was provided for a solar/thermal system configured to power a reverse osmosis (RO) desalination unit to produce 7000 gallons of fresh water in an eight hour period.  A field of line-focus tracking solar collectors is used to heat a high pressure liquid-vapor water storage tank supplying two compound reciprocating steam engines, one direct-connected to the RO high-pressure pump and the other to an electric generator for auxiliary power.  An auxiliary heating loop with an oil fired boiler is also used to supply the steam engines.

The system operates in either all-solar, all-oil, or mixed solar/oil modes.  Primary operating mode is assumed to be a mixed solar/oil mode in which the oil-fired boiler is used only to prevent shutdown of the RO system during the course of a partly sunny day.  In this mode, the RO system does not come on line in the morning until the solar collector field has brought the high-pressure storage tank to a point near maximum operating pressure.  Thereafter, the oil-fired boiler comes on automatically whenever the storage tank is drawn down to a pressure near minimum full-power operation (due to inadequate or intermittent insolation) and remains on, supplying the steam engines, until the solar collectors have again brought the storage tank to the high-pressure cutoff.

In the all-solar mode, the system continues to operate at reduced power as storage tank pressure drops below the point at which the oil-fired boiler would otherwise come on.  A portion of the RO system is shut down to maintain pressure in the remainder.  The all-oil mode is used whenever fresh water is required during non-sunny periods, or to increase fresh water production in sunny periods.