The problems of the supply of different fuels, and its implications for the future

INSIDE A POWER STATION: the Carville Power Station, showing the Parsons Turbine-Alternator sets.

WE have repeatedly noticed how the steam engine, the oil engine, and the gas engine have effected a transformation of the habits and customs of the world, and we have seen that each and all of these are merely contrivances for utilising the heat produced by burning fuel. The great problem for all nations in the coming years is the supply of fuel, for upon it depends not merely their chances of growth, of increasing prosperity, and the happiness which ought to accompany it, but their very existence. We shall see in this chapter how it is that every nation which desires to make the most of the useful things which lie beneath the soil or grow upon its surface, will have to pay attention first of all to the supply of fuel, and to economy in its use.

The Coal Question

What is coal? A geologist will tell you that it is a black rock, combustible or capable of being burnt, found in the ground at varying depths in layers of variable thickness. Some “seams”, as they are called, may be no more than a few inches between the incombustible rock above and the incombustible rock below; while others may be 30 feet. Frequently a lump will show distinctly the trace of a leaf, like that of a fern. Others are shaped like branches of trees, while forms like huge tree stumps are found standing vertically in the seams. These and other facts show that it has a vegetable origin — that it is, in fact, composed almost entirely of trees and plants that flourished thousands of years ago, before the vast overlying rocks had been deposited upon them. Of the actual structure — leaf and fruit and stem and branch — few traces remain, and coal is, for the most part, formless. It is not crystalline; it shows no evidence of having been melted or even partially burnt. By some process, the nature of which we can only conjecture, the plants of the carboniferous age have been changed from what is in many respects an unsatisfactory fuel into one more compact, and containing less moisture and ash.

Since plants grow only under the influence of the light and heat of the sun, the world’s coalfields contain the stored-up energy of the sun’s activities thousands or tens of thousands of years ago. In the engines and boilers of to-day we are using again some of the energy which, in the form of light and heat, enabled the plants of long ago to store up carbon, which is the principal constituent of all forms of fuel. Coal has, therefore, been called, picturesquely, preserved sunshine, and the term is not inappropriate because by suitable means water can be boiled and steam produced by the direct rays of the sun.

The process of coal formation, however, stopped long ago. Nowhere, in no part of the earth where the explorer has yet trod or the prospector searched, is coal being produced. In a few places peat is growing, but it is inferior to coal as a fuel and is being formed in so few places that there is no hope of it ever rendering the same service as coal. So far as scientific men can tell, the quantity of coal in the world is limited; no more is being produced, and when the known fields are worked out other forms of fuel, if there are any, will have to be used, or the world will be a cold and dreary place indeed. Save for water there may be no source of power left. The hum and buzz of the factory will be hushed, and the great blast furnaces will fall to pieces — a few perhaps remaining like decayed monuments standing amid a scene of desolation and recalling a greatness that has passed away.

To no people in the world is the supply of coal of more importance than it is to those who live in the British Isles. Their commanding position in manufactures and commerce is built upon rich coalfields, which are slowly but surely becoming exhausted. Before the eighteenth century coal was hardly ever used as a fuel. Charcoal was employed in the manufacture of iron until 1739, and the badly constructed grates rendered timber the only possible domestic fuel. Then the improvements in the manufacture of iron, the steam engine, and the inventions of new textile machinery led to an enormous increase in its consumption. For at least a hundred years we continued to use coal without any thought as to how long it would last. Not until 1857, when Professor Edward Hull published his book on The Coal-Fields of Great Britain, did anyone attempt to calculate the amount available, and it was three years later when the powerful voice of Professor William Stanley Jevons was raised in warning through his publication The Coal Question. Ultimately the Government appointed a Royal Commission, which reported in 1870 that the probable amount was 146,480 million tons. And as the amount raised in that year was only 110 million tons there appeared to be sufficient to last 4,000 years.

TITLE PAGE OF JEVONS’ The Coal Question, first published in 1860.

But the amount raised annually did not stop at 110 million tons. Factories and workshops increased and multiplied; ships became larger, swifter, and more numerous. The population of the towns grew rapidly while, relatively, the population of the country declined. The demand for food exceeded, to a greater and greater extent, the home supply. More and more food had to be imported, and for many of our imports we had to pay directly or indirectly in coal. Consequently the amount raised annually increased as shown in the following table:

1871 . . . 110 million tons

1898 . . . 202 million tons

1899 . . . 220 million tons.

The 4,000 years of possible duration was now reduced to 2,000 years, and there was still no sign of the demand for coal abating. In 1901 another Royal Commission on coal supplied was appointed. They reported in 1905, and came to the conclusion that there was still a store of 140,000 million tons — a result which confirmed the opinion of the Commission which sat thirty years before. They recommended economy; but they did not realise how rapidly the amount raised annually was to increase as the new century wore on. Look at the following figures:

1903 . . . 230 million tons

1911 . . . 243 million tons

1912 . . . 260 million tons

1913 . . . 287 million tons.

In ten years the amount increased by nearly 60 million tons per annum — more than was raised altogether in 1861. If the rate remains constant the duration of 4,000 years in 1870 had fallen to 500 in 1913, and in the absence of some scientific discovery which shall render coal unnecessary, all the industrial activity of Great Britain will be extinguished before 2400. If the rate continues to increase, the land will, under the same conditions, be desolate by 2050, within the lives possibly of the great grandchildren of those who read this.

When you consider this spectacle of a great nation humbled to the dust, its industries decayed, its people forced to emigrate, its towns deserted and in ruins, you will ask, “Is there no means of averting this calamity, or at least of postponing it until scientific discovery shall have shown how to produce power in other ways?” There is. But only a small portion of it lies within the scope of this article. Not a pound of coal should be burnt unnecessarily. But in order to effect this there should be only large engines under men who understand how to get the most out of them. The boilers, steam-pipes, and cylinders of a small engine have larger surfaces in proportion to their volumes than large engines, and they waste more heat even under the most skilful management. An engine working only part time is less efficient than one working full time, and a man that cannot fully employ an engine should not be allowed to have one. He should purchase electrical power or gas power from a large source of supply, such as through a power station or supplier of gas.

The average amount of coal used per horse-power per hour in this country is 5 lb. or 6 lb., yet the great turbine built by Messrs. C. A. Parsons & Company for Chicago, requires less than 1 lb. If the consumption of the average engine is 5 lb. to 6 lb. the consumption of many must be much higher. As about 80 million tons of coal per annum are used for producing power, a reduction of the average consumption to, say, 3 lb. would save about 30 million tons per annum. And at 10s. a ton at the pit mouth this would amount to £15,000,000 a year. Just think, too, of the reduction of wear and tear on the railways, and the saving of wages which are now merely paid for moving stuff which ought not to need moving. If the men engaged in this, and the colliers who would also be liberated, went on the land, more food would be produced at home, we should import less, and we need not export 76 million tons of coal as we did in 1913. We are not so well off that we can afford to let it go unnecessarily. Germany has more than we have, and is raising it at half the rate. We are exhausting our supplies more rapidly than any other country in Europe.

Advantages of the Gas Engine

But there are other methods of economising, even in the production of power. Where large engines are impossible and electricity cannot easily be obtained, it is more economical to convert coal into gas in a gas producer, and to use the gas in gas engines than to burn coal under a boiler. It has not hitherto been possible to make gas engines large enough to compete with steam turbines for large powers, and for generating electricity they are not quite so suitable, but for all other purposes up to 1,000 horse-power they are effective and economical. Moreover, the bye-products which can be collected from the producer are valuable in industry and agriculture, so that a double purpose is served by their use.

The advantage of the gas engine, as an engine, lies mainly in the following facts:

(a) The heat is produced in the cylinder, just where it is converted into work. There is no loss, therefore, by radiation from the surface of boilers and long lengths of piping.

(b) When air and gas are mixed in proper proportions the combustion is rapid and perfect. There are no unburnt particles like those which pour out of the tops of factory chimneys, which not only represent waste in a direct sense, but lead to an unnecessary expenditure of soap and water, and cast a black pall over every manufacturing town.

(c) The stand-by losses are small. Very little coal is used when the engine is not drawing gas from the producer, and when the engine is needed it can be started up in a few minutes, while some time is required to get up steam in boilers.

These advantages were so clear, even in 1880, that the total replacement of steam by gas within fifty years was prophesied by eminent engineers. What they did not foresee, however, was the difficulty of building very large gas engines, the invention of the turbine with its economy of steam and its evenness of effort, and the need for this evenness of effort in driving electrical machinery. Moreover, the enormous growth in the demand for power destroyed real competition even for small sizes, and kept engineers busy making both classes of engine. The cheapness of coal and the small proportion which the cost of power bears to the cost of manufacture, also prevented manufacturers from exerting themselves in the direction of economy.

Gas can, of course, be burnt in other ways than in the cylinder of an engine. It is used very extensively, not only for domestic heating, but also for furnaces in the factory. But until recently attempts to use it for raising steam have not been very successful. The amount of heat obtainable from any fuel is proportional to the weight burnt, and gases are so light in comparison with solids that they require a large furnace. The fierce flame playing directly upon the plates is also objectionable because it leads to overheating. But within the last two years a new process has been devised which is interesting because it has arisen out of investigations in pure science, and because it enables a greater proportion of the heat produced by the burning fuel to be communicated to the water in the boiler.

In order to understand this invention let us consider two facts. Two gases, such as hydrogen, coal gas, or producer gas, or Mond gas, or blast-furnace gas, and air or oxygen, can be exploded by means of a flame, or a spark, or a hot wire, but a certain temperature is necessary to effect this. Slow combustion, however, goes on at temperatures below that at which explosion takes place, and the rate at which this slow combustion goes on depends upon the nature of the surface of the vessel in which the gases are enclosed, or upon the presence of certain substances in the mixture. In the presence of certain (generally porous) substances, combination may be so rapid on the surface of the material that the heat produced causes explosion. The first fact, then, is that certain substances promote extremely rapid combustion.

The second fact is best illustrated by an ordinary Bunsen burner, or a gas stove, or any gas burner in which some air is mixed with the gas before burning. In these burners the air openings are always so proportioned that the air which enters at the base is insufficient for complete combustion, the remainder being obtained by the flame from the atmosphere above the burner. If the air holes be stopped up gradually, the mixture becomes more and more nearly in the correct proportion for an explosion. The flame grows smaller, a sharply defined inner blue cone makes its appearance, and, finally, the flame “strikes back”, producing an ordinary luminous gas flame starting from the small orifice through which the gas enters. Before this occurs the velocity of the gases passing out of the burner has always been at least as great as the rate at which the flame tends to pass down the tube. When it does occur, when the flame “strikes back”, the velocity of combustion exceeds the velocity with which mixture flows upward. An explosion has not occurred, but the rate of combustion has been greatly increased.

Now, Professor William Arthur Bone found that if he closed the end of a tube with a disc of porous material something like fireclay, passed an explosive mixture of gases into the open end, and applied a light at the other, combustion went on in the pores of the disc, causing it to glow brightly. This was a case of surface action. The gases will not pass through the disc rapidly enough in either direction to allow of a flame on the outside, or an explosion inside, but combustion proceeds rapidly just within the surface of the material itself.

WASTE HEAT BOILER manufactured by the Bonecourt Waste Heat Boiler Company.

As a result of this discovery we have the Bonecourt Boiler which shows one of several forms the apparatus takes. The boiler is fitted with tubes, 6 inches in diameter, and each tube is packed with blocks of special material upon the surface of which the mixed gases burn. The combustion takes place mainly in the first third of the length of the tube, and so much heat is abstracted from the gases by the material with which the tube is packed in the last two-thirds, that the temperature at the point of exit is only 30° higher than that of the steam in the boiler. More than 92 per cent, of the total heat produced is communicated to the water, as compared with 75 per cent, in the case of the best type of ordinary boiler, and it can be made in sizes to compete with the largest of them. The Bonecourt Boiler Company, moreover, claim that it occupies less than one-ninth of the space required by Lancashire boilers evaporating the same quantity of water per hour, though this does not allow for the space required if producers had to be installed. A single tube only 6 inches in diameter will burn over 900 cubic feet of town’s gas per hour and produce 400 lb. of steam from and at 212° F. in the same time.

The saving, as compared with ordinary boilers, depends upon the nature of the fuel used. Town gas is generally expensive, gas from blast furnaces and coke ovens is cheap and would otherwise run to waste, and Mond gas is cheap if the bye-products are recovered. So that there are many cases in which the full advantage of 15 per cent, to 18 per cent, in the efficiency of these boilers would be gained. It is not possible, however, for manufacturers to scrap their plant every time an improvement is placed on the market, and these boilers will be more readily adopted in iron and steel works which have an ample supply of blast furnace and coke oven gas available.

Oil and Petroleum

Whenever this question of the supply of fuel is raised people ask at once, “What about oil?” The medium oil engine, the petrol engine, and the Diesel engine are so familiar that the mind at once travels to the possibility of securing power without using boilers or gas producers at all, and few people other than engineers, chemists, and geologists have any idea of the magnitude of the oil supply or to what extent it is comparable with that of coal. The broad facts of the case, however, can be put very briefly. The total production of oil in the world, in 1913, was 57 million tons — 30 millions in the United States, 10 millions in Russia, and the rest in Roumania, Persia, Mexico, and the Far East. On the other hand, the production of coal in Great Britain alone in the same year was 287 million tons. The world’s production of coal is probably about 1,000 million tons, and there seems no reason to believe that oil will ever be able to provide for more than one-twentieth of the world’s power.

But when we speak of oil in this way we refer to petroleum, which is obtained by sinking wells into layers of earth far below the surface, which are saturated with it. Frequently this is under pressure, so that when the borehole reaches the oil it is forced up in a fountain. Hundreds of thousands of barrels a day are obtained from “gushers” without the trouble of pumping. But oilfields seem to be more quickly worked out than coalfields, so that active exploration for fresh fields has to be carried on if the supply is to be kept up.

So far as those fuels which are derived from petroleum are concerned, the gradually rising prices will put a limit to their use, and the people in the countries in which they occur will have an advantage over those in the countries to which they have to be conveyed. Manufactures must, as a rule, be carried on in close proximity to the source of raw material or fuel, and if we in Great Britain had to import fuel our export trade would dwindle to insignificant proportions. Our greatest need of oil is for the Navy, unless that era of certain peace which is the hope of so many people shall begin in earnest. The submarine depends upon the Diesel engine, and the fastest vessels of other types are wholly or partially dependent upon oil fuel for raising steam. An adequate supply for the protection of our trade and the defence of the Empire will, ere long, be obtainable from British Colonies and Dependencies, but it is unlikely that this will be sufficiently plentiful or cheap to be used in providing power for manufactures. For this we shall have to rely upon the bountiful but not inexhaustible provision of Nature beneath our own soil.

Now while there is no vast natural store of liquid fuel in Great Britain, it does not follow that since we cannot get all we want from other countries we must go seriously short. For many years oil has been obtained by distilling certain shales in Scotland, and some, at present of inferior quality, is obtainable from certain clays in England. Again, benzol obtained from coal tar can be used in place of petrol in the smaller internal combustion engines. There are also Diesel engines running quite satisfactorily on the heavier oils obtained from tar. So that by distilling some of our coal we can provide the amount of gaseous and liquid fuels we require. Since not only fuel in its different forms, but many other substances essential to manufacture, are obtainable from coal, it is clear that one of the great problems of the future for this country is to secure that coal shall be burnt or distilled in just those proportions which satisfy our various needs, and that the processes should be carried on in such a way that not a pound of the precious rock is wasted.

We are not doing this now, because few people know the facts or understand the principles involved. It is nobody’s business to see that fuel is not wasted, and everybody plays for his own hand. And yet the action of a few thousand people and the prejudices or ignorance or indifference of a few million are hurrying the whole nation towards industrial bankruptcy. Within the next hundred years — perhaps even sooner — matters to which no one will listen today will, in all probability, overshadow in their magnitude and their menace every other topic of human interest.

Let us now take a rather wider view of the fuel question and look at it as it affects the world and its distant future. The same process of exhaustion which has gone on and is going on in Great Britain will be repeated in other lands. They may learn from our experience, but the process of exhaustion, though slower, is inevitable. Are the resources of human knowledge equally limited? Has man struggled all these years to master Nature only to be beaten in the end? When he has swept bare the forests, won the last seam of coal, drained the last oilfield of its precious liquid, will he then be reduced to his former dependence upon the sun for light and warmth, and upon muscle and nerve for things of use and beauty which are not found ready made? By no means. So long as the sun shines, and the wind blows, and the rain falls he can wring a sustenance from the soil and hold at bay the savagery which would otherwise enfold him. But for this he must have power. How, then, is he to obtain it?

The exact way in which petroleum has been formed in Nature’s vast manufactory is not fully understood, but all solid fuel is of vegetable origin. So long as plants will grow there will be a source of fuel.

Other Sources of Fuel

It does not follow, however, that it will be of timber. Forest trees are of slow growth, and half the world devoted to forestry would fail to keep the factories of the other half going. But all plants contain cellulose, which they build up out of the carbon dioxide and moisture of the air. When cellulose is fermented it forms ultimately sugar as one of its products; when sugar is fermented it forms alcohol; and alcohol can, be used as a fuel for internal combustion engines. Probably the most suitable substance to grow for this purpose would be beet, because the plant itself in the course of its growth produces a large quantity of sugar and shortens the process which would be necessary if cellulose were the starting point.

But it is very doubtful whether the demand for power could be wholly met in this way, though it is a striking fact that before the Great War the beer and wine produced annually in the world contained about 5 million tons of alcohol. It would be curious indeed if what a man takes to warm his interior should prove to be more valuable for warming his exterior; and still more curious if the motor cyclist of the future should stop at a wayside inn to beg a glass of water for himself and purchase a drink for his engine!

It may be, indeed, that water will ultimately turn out to be the salvation of both. Dame Nature is not so bad a mother, after all, for in many parts of the earth she has provided a source of power which is inexhaustible — a source which may be a little capricious and uncertain, but which, so long as the sun shines and the wind blows and the rain falls will never fail. For under the influence of the sun the air takes up moisture from the great oceans, and the wind carries it towards the land. Local variations of temperature arising from atmospheric circulation cause some of this to be thrown out as rain on land and sea alike; but the main precipitation occurs when the moist winds blow over mountain ranges.

Here, in regions of lower atmospheric pressure, the air expands, and, in expanding, cools. And as the quantity of water vapour that air can carry depends upon the temperature, the seaward slopes of mountain ranges are bathed with moisture.

The rain which falls upon the land becomes separated, generally speaking, into three portions. The first sinks deeply into the earth’s crust, forming underground waters which feed springs and wells, and often form the source of streams and rivers. The second remains for a time on the surface and is re-evaporated directly or through the breathing of plants. The third runs off the surface, feeds streamlet and river, and finally reaches the sea.

It is a wonderful fact, that in this great cycle there is no waste. The water circulates continuously from sea to air and down to earth, and back again to air or sea. It is the third portion of which man makes use to produce power. He builds great walls or dams across the valleys, and prevents the water running away until it has paid toll. From these reservoirs he conducts it through pipes or channels to water wheels or turbines, so that in falling from a higher to a lower level it may do the work of which he stands in need. A cubic foot of water weighs 62·5 lb., and leaving friction out of account, every cubic foot falling from a height of 10 feet will perform 625 ft.-lb. of work. This work may be used to drive dynamos, and the electric current generated may be used for heat and light and power as well as for processes of manufacture which cannot be dealt with here.

Just as the sun enabled the plants of bygone ages to grow, and in this way provided us with vast stores of coal, so the same sun furnishes another means by which man can increase his power and lighten toil.

But while the special conditions which were necessary to the formation of coal have long since passed away, the conveyance of water from sea level to high ground seems likely to go on as long as the earth remains habitable by man. It is a wonderful world, and though perhaps some of what has been written in this chapter has little to do with engines, you will see how important the matter is, and will agree that the engineer who cannot see beyond the whirling wheels and moving rods of his machine is not worthy of the name. For his work is merely one small division of that intellectual struggle by which the human race has risen from savagery to civilisation. Nations rise and fall because human nature is frail and men are prone to error.

But from the first crude efforts in the far distant past the control over natural forces has been gradually widened and extended. Let us who to-day enjoy the fruits of ten thousand years of strenuous endeavour honour the memory of the pioneers, and the gigantic forces which they have brought under our control. Above all, let us realise that our debt to the past and our obligations to the future lay upon us the duty of guarding those gifts which Nature has bestowed upon us, and of exercising economy in their use.

You can read more on “The Gas Engine”, “The Story of Gas Production” and “The Story of Oil” on this website.