195 



Mr. SHUMAN : Of course, that is what is always desired. I 

 believe every steam engineer, if he could, would go in for 

 electricity. But turning heat into electricity is a costly thing, 

 and it does not pay. We have done it by putting up a plant 

 with little thermopiles, which -turned the sun's heat directly 

 into electricity, and every heater might be so constructed. But 

 when we attempt to do that every square foot of surface costs 

 about 10 sterling, which is, of course, out of the question 

 altogether. We have to keep down to a matter of 2s. or 35. 

 per square foot. 



Mr. A. S. E. ACKERMANN : Mr. Chairman and Gentlemen 

 I have been greatly pleased to be associated, in conjunction 

 with my colleague, Mr. C. T. Walrond, with the interesting 

 work of Mr. Shuman and his enterprising clients, the Sun 

 Power Company, the directors of which are to be congratulated 

 for the plucky manner in which they have spent large sums of 

 their own money in the experiments. When I first heard in 

 June, 1910, of water being boiled by the unconcentrated 

 radiation of the sun I was very incredulous, but on arriving 

 in Tacony, a suburb of Philadelphia, I found that the small 

 sun heat absorber (consisting of a lamellar boiler in a flat box 

 with a cover formed of two sheets of glass with a i-in. air 

 space between them) was, in fact, boiling water without any 

 concentration by mirrors or lenses or any other means. The 

 maximum temperature which I registered under the second 

 layer of glass was 250 F. 



There were practically no mechanical difficulties in con- 

 nection with the utilization of solar energy; it was merely a 

 question of either reducing the cost of construction of the 

 plant, or of increasing its output per square foot of radiation 

 collected. The improvement effected by the design of the 

 Egyptian plant compared with that at Tacony was that 

 the former gave 33 per cent, more steam than did the latter. 

 Part of this was no doubt due to the improved climatic con- 

 ditions in Egypt, but it was equally certain that part was due 

 to the improved design, for on comparing the atmospheric 

 conditions which obtained during the Tacony trials with those 

 which obtained during the Egyptian trials, the difference was 

 found 1 to be small. 



Another important improvement in connection with the 

 Egyptian plant was that the output of steam was much more 

 nearly constant than that of the Tacony plant, and was more 

 constant than was expected. This was due to the fact that 

 the number of solar rays caught in the morning and evening 

 was the same as that caught at mid-day, the only difference 

 being that in the morning and evening the radiation passed 

 through a thicker layer of atmosphere. For irrigation purposes, 



