MISCELLANEOUS SUBJECTS 469 



sun-power collection pay, however, requires much thought 

 in designing on the compromise lines so necessary to 

 follow in a battleship design. 



You may ask : What will our sun-power plant do when 

 there is no sun ? Of course, when the source of our 

 supply of power is cut off we cannot get it; but we can 

 do what is done in a great many other lines, and that 

 is, store it in an already well-tried and simple manner. 

 During the day we will heat large quantities of water 

 to the boiling point and store this in large tanks, properly 

 insulated from the atmosphere. From this boiling water 

 we will draw during the night or during a rainy day low- 

 pressure steam, and with this run our engine, which is 

 so constructed that it will run economically at 4 Ib. 

 absolute. In other words, as the condenser draws on the 

 boiling water in the tank through the engine the heat 

 contained in the boiling water will generate low-pressure 

 steam, and this steam will run the engine. There is 

 nothing new in the art of using low-pressure steam 

 generated from water which has been brought to the 

 boiling-point by extraneous means. It is a very practical 

 and successful method of storing power in the tropics, 

 where this power is produced from a source which is 

 entirely free of all cost. 



It will occur to you that sun-power plants occupy an 

 enormous amount of room per horse-power. This is quite 

 true; but in the locations where we are suggesting their 

 use land is very cheap indeed, and the amount of room 

 occupied is not a great disadvantage. 



Sun-power collecting may be called " power farming/' 

 and may be compared to growing coal. If coal to run 

 a 5O-h.p. engine perpetually could be grown without any 

 expense whatever on an acre of adjacent ground, then 

 this acre of ground would be exceedingly valuable in the 

 tropics with coal prices at from 2 to 3 per ton. Hot- 

 houses to produce equal net values would have to cover 

 many times larger areas, and still hot-houses do pay even 

 where land is very expensive. 



The cost of upkeep is an important factor. The heat 

 absorbers are made of reinforced concrete for the founda- 

 tions, steel for the framework, cast-iron for the boilers, 

 and glass for the mirrors and boiler covering all 



