498
12
17. We now pass to the annual generating and engineering charges. These are calculated at 100 per cent. load factor for one set of machines, a figure which would not, of course, be reached at once, and they do not include charges payable in the case of a private company but not by the State, namely, insurance, local rates and taxes. They include, for a generation of 6,579,000 units per annum, coal (at 248. 3d. per ton in England), waste, water, stores, labour, repairs, and maintenance, interest on capital at 6 per cent., and depreciation, the life of the plant being taken at fifteen years and that of the buildings at thirty years. For the above, the annual cost of the power plant would be £21,024. In respect of the rest of the system, interest, maintenance and depreciation would amount to, say, £26,000. There is also to be added the coat of the engineering staff which, with establishment charges, would be £5,780. regards the Indian station, we have ascertained that the cost of fuel would be practically the same as in England, but we deem it necessary to add 33 per cent. in respect of the other costs of generation and the cost of the engineering staff.
As
There remain the operating charges, and these would be in England £15,750 and in India £21,000.
The following figures summarise the foregoing :-
English Station-
£
Generating costs
21,024
Interest, maintenance and depreciation in respect of rest of system (say)
26,000
Engineering staff
5,780
Operating costs
15,750
68,554
Indian Station—
Generating costs
26.000
Interest, &c., as above..
30,000
7,700
2,000
Engineering staff as above, plus 33 per cent.
Interest and depreciation in respect of residences Operating costa
:::::
21,000
86,700
To summarise, the costs of one pair of 500-kilowatt arc stations working between England and India, as nearly as it is possible to estimate them, would be as follows:-
Capital cost Annual cost
£
615,000
165,000
18. In view of the provision in the near future of a supply of electrical energy generated in bulk at capital power stations, it might naturally be thought that current for a wireless station might be purchased more economically than it could be generated. This is only the case within narrow limits. We have the highest authority for saying that unless the wireless station were situated within a very short distance, say, five or six miles, of the bulk station, electricity independently generated at the wireless telegraph station at a high annual load factor would be cheaper than current purchased, though this is dependent on the locality and the cost of fuel delivered there. This would especially be true of a station equipped with arc transmissiou, for the reason that an are requires direct or continuous current at a tension of about 1,000 volts, whereas every bulk station produces, and will produce, high tension alternating current. Current from a Government bulk station must, therefore, when received at an arc station, be transformed down to a voltage suitable for driving rotary couverters, which in turn will generate the current required for the arc. Thus an arc sub-station would have to be equipped with a transformer and rotary converter, in duplicate.
Moreover, to secure maximum efficiency, a transmitting wireless station demands a situation conforming to certain geological and topographical conditions, and it might not be possible to find these within a few miles of a bulk generating station. In case, however, this should prove possible-and this is a matter we proposed to refer for decision to a sub-committee, had time permitted it will be of interest to consider what economies, if any, would result in the case of the main home station.
The figures for a 500-kilowatt are station purchasing its energy are as follows:--
Capital cost-
Sub-station for 500-kilowatt arcs, erected complete, comprising two 750-kilowatt rotary converters (6,600 volts A.C to 1,250 volts D.C.); two 750 K.V.A. transformiere (11,000/0,600 volts); buildings; A.C. and D.C. switchgear; contingencies at 10 per cent.; and 5 miles overhead transmission line in duplicate Generating cost-
Comprising 7,690,000 units purchased, wages, repairs and main-
tenance, interest on capital, and depreciation
£
37,605
27,282
13
For one station of this power and type, therefore, the capital cost, if current were purchased, would be £37,605, against £68,525 if current were generated locally, a decrease of £25,920; and the annual generating cost £27,282, against £21,024, an increase of £6,258. The possibility of effecting even this saving in capital expenditure, a considerable increase of annual generating cost, depends entirely upon whether a suitable site for wireless transmission could be found within a few miles of a bulk generating station and on the local facilities for delivering coal, &c., and the possibility would apply only to the home station. Taking everything into consideration, this method presents no appreciable advantage.
19. In examining a 4,000 miles service it must farther be emphasised that the above pair of stations would be but one link in a chain, except as regards traffic between England and India only, and to the payment of ita expenses only a proportional part of the revenue from each paying word from all other regions could be allocated. Traffic estimates will be considered in detail later. It will suffice to say here that we see little or no prospect that under such conditions a self-supporting Imperial service could be established.
In conclusion, we believe it to be impossible to feel sure that the above-mentioned power would actually afford a satisfactory commercial service. One company offering to supply these 500-kilowatt arcs names 4,800 miles as the maximum range of au all-year service, and although they specify 100 words a minute as the available speed, we doubt whether such a performance will be reached for some time to come. There would be grave danger that the history of long-range transmission might repeat itself, and that, the service proving unsatisfactory, a proposal to "smash through" by the use of higher power would once more follow.
For many reasons, therefore, we regard it as essential to seek a different solution of the problem.
20. We pasa now to consideration of the 2,000 mile class of distances, that in transmission, between the Imperial distances specified, by 2-step, instead of by 1-step performance.
Under these conditions the arc system would not be proposed. We have already (section 11 (d) given reasons for the belief that valve transmission can be relied upon to cover this range; it lends itself far better to the development of high-speed working; it would not be liable to international restriction because of its production of interfering waves; it is susceptible of the sharpest tuning, admitting of the practical use of a larger number of contiguous wave-lengths; it can safely be installed in remote stations, requiring for repair in case of breakdown only ordinary experience of electrical machinery; its wave-lengths can readily be changed as desired; most important of all, its employment would beyond question be along the lines of future wireless development, for example, the development already in view of the use of wireless telephony over long distances; and it would evade the risk that expensive machinery might within a few years be rendered obsolete by the advance of radio-telegraphic science. There remains, again, the vital question of cost.
21. It has already been suggested that since a valve aerial power of 24 kilowatts has given good communication for military purposes over 2,000 miles even with inefficient reception, it may confidentally be expected that a similar power of 120 kilowatts would afford a satisfactory commercial service over 2,239 miles, the Great Circle distance between Oxford and Cairo, and indeed further. This demands a supply of 248 kilowatts at the power terminals. We take, first, the cost of a station to generate this power-
Two 300-kilowatt turbine alternators, 3-phase, 50 cycle, -3,000 volts between phases; three water-tube boilers with anperheatera, economisers, &c.; buildings, steam, feed and circulating pipework; bigh and low tension switchgear; pumps and coal-handling plant; and contingencies at 10 per cent, erected complete
£
34,843
The aerial system in this case would consist of six guyed steel masts, 656 feet high, since for half the range of the 1-step system a smaller number of lower masts would suffice, and the cost of these, with aerial and earth connection, would be £62,500.
An estimate for the cost of the valve system complete has been furnished to us by the Naval Signal School. This includes the necessary valves, transformers, hand-keys, auxiliary circuits, condensers, frame-works, instruments and aerial tuning coil. For the production of an aerial power of 120 kilowatts (under certain conditions,
T