_Working Expenses and Maintenance of 10,000-Light,
or 600-Kilowatt, Plant._
-------------------------------+-----------------------------------+
| Direct Alternating |
| Transformer System. |
-------------------------------+-----------------+-----------------+
_Materials_— | £ _s._ _d._ | £ _s._ _d._ |
Coals: 4,380 tons at 17_s._ | 3,723 0 0 | |
” 2,550 ” 17_s._ | · · | |
Oil, water, and petty stores: | | |
1,500 hours at 7_s._ 6_d._ | | |
7,250 hours at 1_s._ | 925 0 0 | |
1,400 hours at 5_s._ | · · | |
Total cost of material +-----------------+ 4,648 0 0 |
| | |
_Labour_— | | |
2 foreman drivers at 45_s._; | | |
6 drivers at 30_s._; | | |
9 firemen at 24_s._; | | |
sundry labour | 1,388 8 0 | |
| | |
1 foreman driver at 45_s._; | | |
2 drivers at 30_s._; | | |
3 firemen at 24_s._; | | |
sundry labour | | |
| | |
_Salaries_— | | |
1 chief at £500; | | |
2 assistants at £200 each; | | |
4 clerks at £80 each | 1,220 0 0 | |
| | |
1 chief at £500; | | |
1 assistant at £200; | | |
4 clerks at £80 each | · · | |
+-----------------+ 2,608 8 0 |
_Maintenance of Plant_— | | |
Motive power and dynamos: | | |
10 per cent. on £18,010 | 1,801 0 0 | |
10 per cent. on £13,400 | · · | |
Buildings and fittings: | | |
5 per cent. on £11,000 | 550 0 0 | |
5 per cent. on £8,000 | · · | |
Transformers: | | |
10 per cent. on £7,500 | 750 0 0 | |
Accumulators: | | |
15 per cent. on £9,600 | · · | |
Mains: | | |
7½ per cent. on £20,430 | 1,532 5 0 | |
2½ per cent. on £26,262 | · · | |
Regulating gear: | | |
10 per cent. on £500 | 50 0 0 | |
10 per cent. on £2,500 | · · | |
+-----------------+ 4,683 5 0 |
| +-----------------+
| |11,939 13 0 |
| +-----------------+
2,100 units × 365 days | | |
= 766,500 units. | | |
Cost per unit | · · | 3·75_d._ |
====================================================================
| Continuous Battery |
| Transformer System. |
-------------------------------+-----------------+-----------------+
_Materials_— | £ _s._ _d._ | £ _s._ _d._ |
Coals: 4,380 tons at 17_s._ | · · | |
” 2,550 ” 17_s._ | 2,167 0 0 | |
Oil, water, and petty stores: | | |
1,500 hours at 7_s._ 6_d._ | | |
7,250 hours at 1_s._ | · · | |
1,400 hours at 5_s._ | 350 0 0 | |
Total cost of material +-----------------+ 2,517 0 0 |
| | |
_Labour_— | | |
2 foreman drivers at 45_s._; | | |
6 drivers at 30_s._; | | |
9 firemen at 24_s._; | | |
sundry labour | | |
| | |
1 foreman driver at 45_s._; | | |
2 drivers at 30_s._; | | |
3 firemen at 24_s._; | | |
sundry labour | 975 0 0 | |
| | |
_Salaries_— | | |
1 chief at £500; | | |
2 assistants at £200 each; | | |
4 clerks at £80 each | · · | |
| | |
1 chief at £500; | | |
1 assistant at £200; | | |
4 clerks at £80 each | 1,020 0 0 | |
+-----------------+ 1,995 0 0 |
_Maintenance of Plant_— | | |
Motive power and dynamos: | | |
10 per cent. on £18,010 | · · | |
10 per cent. on £13,400 | 1,340 0 0 | |
Buildings and fittings: | | |
5 per cent. on £11,000 | · · | |
5 per cent. on £8,000 | 400 0 0 | |
Transformers: | | |
10 per cent. on £7,500 | · · | |
Accumulators: | | |
15 per cent. on £9,600 | 1,440 0 0 | |
Mains: | | |
7½ per cent. on £20,430 | · · | |
2½ per cent. on £26,262 | 656 10 0 | |
Regulating gear: | | |
10 per cent. on £500 | · · | |
10 per cent. on £2,500 | 250 0 0 | |
+-----------------+ 4,086 10 0 |
+ +-----------------+
| | 8,598 10 0 |
+ +-----------------+
2,100 units × 365 days | | |
= 766,500 units. | | |
Cost per unit | · · | 2·7_d._ |
-------------------------------+-----------------+-----------------+
With the exception of the amount allowed for depreciation of the
accumulators, which time alone can show to be correct, the expenses
may be said to be over rather than under-estimated; the 15 per cent.
depreciation given in Table IV. is under what has hitherto been found
necessary to allow for the renewal of the plates of a secondary battery.
If the mean of the two results in Table IV. are taken, the working cost
per Board of Trade Unit will be 3·22_d._, which shows that with both
systems, after making due allowance for interest on capital, directors’
fees, bad debts, and other sundries omitted by Mr. Crompton, there is a
probability of a very fair return on the capital expenditure, and the
prospect of a handsome dividend for an electric lighting company who
can sell electricity at the average price of 7_d._ per Unit.
* * * * *
The cost of maintaining and working electric lighting plant at
private installations is usually much in excess of a supply from a
central-station; but where the installation is over 500 lights, the
difference is not very great.
The working cost at the Athenæum Club of 387 lamps for the past year is
given as follows:—
£ _s. d._
Gas for gas-engine 446 7 10
Oil ” ” 71 3 8
Water ” ” 35 0 0
Wages 175 2 1
Sundries 30 3 0
Maintenance of lamps, etc. 98 4 1
Repairs 103 1 1
—————
£959 1 9
—————
Average cost of lighting by gas and oil for previous years, for
two-thirds number of lights £840.
At the Naval and Military Club, 420 lights cost £821 18_s._ for the
same period, a steam-engine being used instead of a gas-engine.
The annual report of the cost of the electric light at the South
Kensington Museum shows that in a larger installation, consisting both
of arc and incandescent lamps, the annual cost of the latter is much
less than in either of the clubs mentioned. At the Museum there are 860
16 candle-power lamps, working 655½ hours per annum, or 562,387 lamp
hours; the total cost for working last year was £386, which includes
£66 for repairs of engines, boilers, dynamos, and maintenance of lamps;
but rent, interest on capital, depreciation of plant, and management
is not included. The light is used only three evenings a week, so that
the wages of the attendants are proportionately in excess of what they
would be in a central-station.
* * * * *
The cost of arc lighting for street purposes may be estimated from the
following tenders. At Taunton the local electric light company offered
to extend the lighting of streets from 29 to 60 arc lamps of 1,200
candle-power nominal on the Thomson-Houston system, at the following
rate:—
Per annum.
£ _s. d._
Burning on average of 6 hours per night each lamp 17 7 6
7 ” ” 18 12 6
8 ” ” 19 17 6
The posts and supports to be provided and fixed by the company, or, if
the town council found the same, the company would allow a deduction at
the rate of 5 per cent. per annum upon the outlay made by the council.
The lamps are usually about 400 feet apart.
The actual cost of operating arc lights on this system is given in the
following detailed expenses of a six hours’ run of a 50-light plant for
the street lighting of an American city:—
2,600 lb. Ind. nut and slack coal, at $1·30 per ton $1·69
Engineer, one night, at $50·00 per month 1·67
Superintendent or electrician, one night, at $50·00
per month 1·67
Trimmer, one day, at $40·00 per month 1·33
48 pairs of carbons, at $18·50 per month 89
Waste, &c., at $20·00 per year 05
Water rent, at $40·00 per year 11
Half-pint cylinder oil, at 60c. per gallon 04
One pint engine and dynamo oil, at 50c. per gallon 06
One day repairs on machine and lamps, including
globes, at $120·00 per year 33
One day taxes on 50-light plant, assessed at $5,000,
at 2¼ per cent. 31
One day interest on 50-light plant ($10,000), at 6 per
cent. 1·67
—————
Making a total of $9·82
10½_d._ or 20·45 cents. per lamp. £15 10_s._ per annum.
If, in addition to the 50 street lights, 33 other arc lights are
maintained, the total cost is reduced for a six hours’ run to $13·25,
or £2 15_s._ 2_d._ for the 83 lights, 8_d._ or 15·96 cents per lamp,
£12 3_s._ 4_d._ per annum.
Table V. has been calculated by M. Decker, of Nuremburg, and gives
the comparative cost of working 150 lamps by electricity and by gas.
The gas price (1) is that paid in Paris, namely, 6_s._ 9_d._ per 1000
cubic feet; column (2) is the price usually taken commercially, which
includes the fixed charges. The price of electricity is given: 1st,
when a steam-engine is available; 2nd, when it is necessary to lay down
a special engine; 3rd, when a gas-engine is used the gas is charged at
a trifle over the price in column (1).