| British thermal units. | Per cent. | |
| Loss by friction | 138 | 1.1 |
| Loss in exhaust | 7,513 | 60.1 |
| Loss in pipes and auxiliaries | 275 | 2.2 |
| Loss in boiler | 1,000 | 8.0 |
| Loss in stack | 1,987 | 15.9 |
| Loss in ashes | 300 | 2.4 |
| Total losses | 11,213 | 89.7 |
| Energy utilized | 1,287 | 10.3 |
| 12,500 | 100.0 |
Mr. Stott further presents a table showing the thermal efficiency of producer-gas plants, concerning which he says:
The following heat balance is believed to represent the best results obtained in Europe and the United States up to date in the formation and utilization of producer gas.
Average losses in a producer-gas plant in the conversion of 1 pound of coal, containing 12,500 British thermal units, into electricity.
| British thermal units. | Per cent. | |
| Loss in gas producer and auxiliaries | 2,500 | 20.0 |
| Loss in cooling water in jackets | 2,375 | 19.0 |
| Loss in exhaust gases | 3,750 | 30.0 |
| Loss in engine friction | 813 | 6.5 |
| Loss in electric generator | 62 | .5 |
| Total losses | 9,500 | 76.0 |
| Converted into electric energy | 3,000 | 24.0 |
| 12,500 | 100.0 |
The thermal efficiency of such plants, as given by different writers, runs as high as 33, 36, and 38.5 per cent, and for some plants figures as extravagant as “above 40” are boldly published. Although the present aim has been to give the figures for a producer-gas plant that may compare favorably with those of the steam plant of the Interborough Company, an effort has been made to keep well
within obtainable efficiencies. Attention is also directed to the fact that the producer-gas plant considered should be large enough to compare favorably with the steam plant. This precludes comparisons with suction plants, which are relatively small but give higher proportional efficiencies than the larger pressure and down-draft plants, for these require more or less auxiliary apparatus.
Mr. Stott seems ready to accept a thermal efficiency of 24 per cent for the best producer-gas plants for comparison with 10.3 per cent efficiency for his steam plant, but a careful study of the problem has led to a more conservative estimate for the producer-gas plant, namely, 21.5 per cent.
The tables just given show the comparative efficiencies reached in plants of the best type, both steam and producer-gas, but these are seldom realized in common practice. The results obtained in the government plant at St. Louis are probably more nearly representative of the ordinary type of apparatus. These results are as follows: