UTILIZATION OF SOLAR ENERGY ACKEEMANN. 



161 



some volatile fluid such as ammonium hydrate, ether, or sulphur 

 dioxide, the vapor being used to drive an engine. 



Willsie thinks he was the first to propose this two-fluid method for 

 the utilization of solar energy, and, so far as the author knows, his 

 claim is correct. Their first sun-heat absorber was built at Olney, 

 111., and consisted of: 



A shallow wooden tank tightly covered with a double layer of window glass. 

 The sides and bottom were insulated by inclosed air spaces filled with hay. 

 The tank was lined with tar paper, well pitched, to hold water to the depth of 

 3 inches. Although the weather was cold and raw, even for October, with occa- 

 sional clouds, the thermometer in the water showed temperatures higher than 

 were needed to operate a sulphur dioxide engine. 



The next solar heater was built at Hardyville, Ariz. Sand was used for 

 insulation. Three tests for the amount of heat gave these average results in 

 December : 



An estimate showed that 50 per cent of the heat reaching the glass was 

 absorbed into the water. 



In 1903 some further heater tests were made, patent applications filed, and to 

 carry on experiments on a more extensive scale the Willsie Sun Power Co. 

 was incorporated. 



In the spring of 1904 a complete sun-power plant was built at St. Louis. 

 In this installation a 6 horsepower engine was operated by ammonia. The 

 heater consisted of a shallow wooden basin coated with asphalt and divided 

 by strips into troughs. It was covered by two layers of window glass and 

 insulated at the sides and bottom by double air spaces. Each trough of the 

 heater formed a compartment. The troughs w^ere inclined so that a thin layer 

 of water flowed from one trough to the next. In this heater was collected and 

 absorbed into the water from the sun's rays 211,500 heat units per hour at 

 noon, or 377 heat units per hour per square foot of glass exposed to the sun. 

 As, according to accepted solar observations, about 440^ heat units per hour 

 reached a square foot of glass, this heater was showing the surprising efficiency 

 of 85 per cent, and collecting nearly twice as much solar heat per square foot 

 per hour as did the apparatus of Ericsson. Of the lost heat I estimated that 40 

 heat units were reflected and absorbed by the glass and that 23 heat units were 

 radiated. On cloudy days the water could be heated by burning fuel. A de- 

 scription of this plant appeared in a St. Louis paper and in a New York paper, 

 but, so far as I know, it has not been mentioned in any technical publication. 



It was then decided to build a sun-power plant on the desert, and some land 

 about a mile from The Needles, Cal., was purchased for a site. 



iNo; only 299. Note: 0.70X1.93=1.352 calories per square-centimeter-minute=299 

 B. t. u. per square-foot-hour. 



18618°— SM 1915 11 



