380 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913, 



The by-products would sell for — 



Ammonia sulphate, at f 12 per toil-- . _ £4,560 



Tar, 15s. per ton 180 



Value of gas not included. 



Credit per annum 4,740 



Leaving a net profit of £4,740 less f4,025=£715 per annum. 



The net cost of energy, assuming interest and depreciation on station at 10 

 per cent, is £4,947 less £715=f4,232. 



This is equal to 0.047 per brake horsepower hour, or 0.070 per kilowatt-hour. 



The net cost of energy, assuming interest and depreciation on station at 6i 

 per cent, is £3,892 less f715=f3,177. 



This is equal to 0.035 per brake horsepower hour, or 0.052 per kilowatt-hour. 



This 0.052 is for 300 days of 24 hours, but for the full number of 

 hours in a year it becomes 0.043d. per kilowatt-hour, or 31s. per 

 kilowatt-year. If this can be done with 1,000-horsepower gas en- 

 gines, then there is considerable hope for the future when the internal 

 combustion prime mover is made in as large sizes and as cheaply 

 as steam turbines. 



At the present moment, so far as fuel power stations are concerned, 

 the position appears to be as follows: 



For large prime movers of, say, 6,000 kilowatts and over the steam 

 turbine is in an unassailable position. It is true that the large 

 gas engine has been made in units of several thousand horsepower, 

 but on account of its slow speed and its cycle of operations the size 

 for a given power is very large as compared with a steam turbine. 

 Its weight and price are greater, and the cost of foundations and 

 housing accommodation very much greater. 



The gas turbine, or the gas plus steam turbine, would solve the 

 space difficulty, but although much has been written on the theory, 

 and some work has been done experimentally, this form of prime 

 mover is still in the air. 



As regards the production of steam and of gas for the above- 

 mentioned prime movers, it must be admitted that the method of 

 burning coal on fire grates is less efficient than making gas from the 

 coal and recovering the ammonia, etc. Also it is necessary to admit 

 that there are mechanical limitations to the sizes of ordinary steam 

 boilers as at present constructed. 



On the other hand, gas producer and engine plants can not yet be 

 considered altogether satisfactory, because the gas is so variable in 

 quality. When steam is generated there is no doubt about the 

 product. 



With gas, on the other hand, there is no absolute certainty as to 

 what its quality will be. It depends on the coal, on the condition of 

 the apparatus, on the attention given by the workmen. If attempts 

 are made to increase the yield of the ammonia, then the gas is likely 

 to be poor, and if the gas is of good quality, then the by-products 

 are apt to fall off. 



