The king of Libya’s favorite palace is in Robruk, a town of around 5,000 people at the edge of the Libyan Desert on the Mediterranean shore. Rainfall there is less than five inches annually; there are no surface streams or lakes. The well water is heavily laden with salt, and the king’s private supply of potable water is brought in by truck from another of his palaces some 200 miles away. For sanitary purposes the people of Tobruk use piped water from wells with a saline content of about 3,000 ppm. They drink brackish water hauled in by truck from Bardia, about 75 miles distant. The water they drink analyzes 1,100 ppm—more than twice as salty than is considered tolerable in this country, and it costs $14 a thousand gallons, as compared with an average cost under 25 cents a thousand gallons over most of the United States.
The king has considered supplying Tobruk’s water needs by a 200-mile pipeline from near the source of his own supply. But that would cost over $5 million, an expenditure beyond economic justification for only 5,000 beneficiaries. So last December, in response to a request from the ICA, George O.G. Löf went to Libya to explore the possibilities of solar distillation or other alternatives.
The British foreign aid program in Libya has also been concerned with this problem, and within the last few months it has been responsible for the installation of an electrodialysis system for desalinizing 5,000 gallons of the salty well water per day. A hospital now being built under United States auspices will install a similar plant. Partly because of high-priced power—around 8 ½ cents a kilowatt-hour—the operating costs by this process will come to around $2 per 1,000 gallons of demineralized power.
Construction costs for solar distillation are higher, but operating costs are lower. The main requirements are a lot of spare ground and a lot of sun. Libya has both. Labor for digging, basin-type pools for solar distillation costs less than a dollar a day, and sunpower is free. The costs of thus obtaining sweet water will be compared with those of electrodialysis at Tobruk, and with corresponding costs of solar-stills lately projected at a pilot plant by the Battelle Institute (for the Department of the Interior) near Daytona Beach, Florida.
Here, three such stills are nearing completion. Two are 2,500 square feet in area and the third is a “farm-size” unit, 500 square feet. The larger stills are expected to provide about 250 gallons of distilled water on sunny days, and the smaller one about 50. The sun warms the salty waters in black-bottomed ponds or basins covered with glass or a transparent film-plastic. The evaporated moisture runs down into troughs which carry it to storage.
Electric power at Tobruk is currently produced by five 250 h.p. diesels. The fuel bill for this runs high and is no slight factor in the heavy net import requirements of Libya and its million people. A solar still can desalt sea water quite as readily as brackish well water, with no increase in minimum operating costs. Given these conditions, the prospects for producing potable water economically by sun-power in parched lands such as Libya appear nearly within reach.
A version of this article appeared in print in the May 1959 issue of Resources magazine.
