WASTE HEAT FROM THE DIESEL .sx AN engineer has been defined as a man who can do for one shilling what any fool could do for two .sx Certainly the power engineer's office is to get the utmost service out of a pound of fuel , and the recovery of the heat rejected during a thermodynamic cycle is a problem worthy of his skill .sx The steam engineer has already found a solution by using exhaust steam for process work , but the oil-engine superintendent seems reluctant to tie his engines thermally to the rest of his plant .sx This is unfortunate , for although the oil engine is more efficient than the steam turbine , it still loses some 30 per cent .sx of its heat to the exhaust and upwards of 20 per cent .sx to the cooling water ; these losses are worth re-covering .sx In a discussion of this kind the Still engine immediately comes to mind , but unfortunately this design his not been widely applied .sx However , the Still cycle is not the only method by which the waste heat can be recovered , and the power station , factory , hotel , or department store offers numerous opportunities for using .sx this heat .sx For a straight power plant the Buechi system of supercharging by an exhaust-gas turbine materially raises both the rating tool the efficiency of an engine .sx we have already described an installation of this type , and an article on the system from the pen of its inventor .sx appears elsewhere in this issue .sx In an industrial or commercial establishment it is often possible to connect the oil engine into the establishment heating services .sx Here , of course , is a case for the exhaust-gas boiler .sx These boilers are quite frequently used , although we doubt whether engineers are always fully alive to their adaptability .sx For instance , by the aid of the exhaust-gas boiler the diesel engine is able to .sx enter the power-process field .sx Truly , the arrangement is more circumscribed than the back-pressure or pass-out turbine .sx but where the steam quantity required is relatively small not more than 1 lb .sx per B.H.P. hour the arrangement is practicable .sx Then again , the exhaust-gas boiler can be used for heading the establishment , and for this purpose it may supply either hot water or .sx stem .sx If the establishment is large relative to the power requirements , additional independently fired boilers will be required ; the exhaust-gas boilers may either work in parallel with these , or they may supply the independent boilers with hot feed .sx An alternative service is to supply hot water for toilet and general utility purposes .sx The building-heating systems mentioned so far use either water or steams .sx Hot-air systems could also be supplied from the diesel-engine exhaust , and this is , in fact , being done in the United States .sx The exhaust is delivered to a conduction-type air heater , and the heatedair supplied to the usual system of ducts .sx Compared with the exhaust-gas boiler the air heater will be bulky ; on the other hand the air heater can be arranged for supplementary oil firing , so that additional heaters will not be required for periods when the exhaust is insufficient for the load .sx Contamination of the air may be feared , but in the conduction-type heater there is no contact between the air and the gases , and by placing the air fan on the inlet side of the heater , leakage of the gas into the air will be prevented .sx The recovery of heat from the cooling water is not as simple as it sounds , due to precautions which must often be taken to prevent scaling .sx Water treatment may be necessary , in which case it is wise to conserve the water unless it can later be used for boiler feed .sx It is also common practice to keep the exit temperature low to prevent scaling , and in many plants to continue to circulate the cooling water until the engine is cold .sx Subject to these limitations uses can be suggested for the hot cooling water .sx With the usual exit temperature of about 120 F. the water would be hot enough for the general hot-water supply .sx Where applicable , a sound arrangement appears to be to use a proportion of the cooling water as hot feed for an exhaust-gas boiler .sx Probably enough has been said to show the adaptability of the diesel engine to general heating service .sx There remains the question of flexibility .sx Establishment requirements have an obstinate habit of refusing to balance their heating and power requirements according to the heat balance of the prime mover , and with a heating plant there are wide seasonal variations .sx The plant should be flexibly co-ordinated , and the possibility retained for reverting to independent operation .sx THE DAMNATION OF D.C. .sx Herbert Faulkner Voices a Protest .sx THE present wholesale condemnation of D.C. working is overdone .sx Some engineers seem to imagine it a tribute to the genius of Ferranti to declare that D.C. working was always a mistake .sx Even some of the older pioneers speak of their D.C. work almost apologetically .sx This attitude is ridiculous ; it ignores the fact that the three-wire D.C. system in conjunction with batteries not only established confidence in the public as to the re-liability of electricity , but , by earning really good dividends , brought money into the supply business when the large A.C. systems were failing to make ends meet .sx Extensive electricity supply systems were neither technically nor commercially practicable in the days when district after district equipped itself with a three-wire D.C. supply , achieved lower costs than the alternating stations , and gave a more reliable and cheaper supply of energy .sx Official records of costs per unit show that right up to 1909 , and even later , pride of place for low generating costs was held by small three-wire and battery supplies against much larger concerns run on the A.C. system .sx Two such towns , Present and Rotherham , were in those days quite insignificant in size and output , but they beat the country for low working costs more than once .sx Down to 1907 lighting constituted the greatest demand , and the three-wire and battery station , with its night shift run from batteries , its steam side shut down as soon as uneconomical loading conditions were reached , and the generating sets run at or near to economical load when in service , gave long hours of good steaming conditions and great reliability .sx In addition a keen eye could be kept on valve setting and tuning up the plant generally , by allowing a plant down for a few hours whilst adjustments were made , the battery helping the system out .sx In the A.C. stations of those days , one had to run a set all night to supply a few lamps ; and the conditions were such that uneconomical steam running was unavoidable for most of the 24 hours .sx The writer well remembers one plant running all day , through a Sunday , with 2 amps .sx on its 6,600-volt system and a 5,000-kW .sx set in service .sx That concern lost money year after year until the war , and warned investors off the electric supply field ; nor was it the only example of such conditions .sx During all these years the best paying electric supply concerns were situated in the West End , and were supplying direct current through three-wire systems and batteries .sx In 1898 , when power at Id .sx a unit was still but a vague dream , the electric tramway demand came along , and changed the prospects of many a city electricity supply It offered an 18-hour load every day , 60 per cent .sx of which was between 6 p.m. and 6 a.m. , which was thereevery week-end and public holiday , and when the shops and works were shut down .sx The traction supply turned many an electricity department from being anxiety into a paying concern , for the supply was non-competitive and always at a high rate .sx This traction supply brought down the costs on the general supply , and made the use of motors possible for many auxiliary jobs .sx 'I'hese motors in their turn again improved matters until power could be offered at three farthings a unit about 1909 or 1910 .sx Even then electrical energy had a tough fight against the cheap coal then available and the first-class mill engines of the Corliss and drop-valve type used in the industrial districts .sx In those times the steam turbine had a day-to-day consumption of 18 lb .sx of steam per unit or more .sx Thus , whilst steam turbines could not give their modern splendid performances , coal was very cheap to quite small users , and the selling of energy for power a difficult matter .sx It was undoubtedly the direct-current motor , aided by the traction supply , which pioneered the power supply field , for a reliable and efficient induction motor was not available at the time , whilst most A.C. supplies were single or , at the most , two-phase .sx Indeed , between 1898 and 1902 , many single-phase supplies changed over to three-wire D.C. and battery supply , and so made their systems pay for the first time .sx When three-phase systems were really established , and the induction motor available , the D.C. motor had paved the way in the electrical industry .sx Even then it was many years before the A.C. supplies paid to anything like the same extent as the D.C. systems .sx That D.C. for general supply work over a large city is out of date is not denied .sx What is protested against is the slighting of the pioneer work of many early power-station engineers who , when the A.C. systems were losing money , rallied electric supply on the three-wire D.C. basis , showed electricity was reliable and convenient , and , later on , cheap for other purposes than lighting .sx These men , when the limit of the D.C. system was reached , developed A.C. systems in a thorough and workmanlike manner .sx MINIATURE REMOTE CONTROL OF LARGE SWITCHGEAR EQUIPMENTS .sx THE system of remote control of extra-high-pressure switchgear which is in use in this country is perfectly satisfactory when the gear is in the same building as the control panels or in a building adjacent .sx When the switchgear is of the outdoor variety , the limitations of the usual system of control begin to become apparent , and the necessarily long leads between instrument trans-formers and control militate against accuracy of measurement .sx Cases have occurred in the United States where it has been found very desirable to locate control gear at considerable distances from hydro-electric power stations , and in the case of the Holland generating station of the New Jersey Power & Light Co. a system of remote control has been devised which is suitable for distances of the order of one mile .sx When it is desired to control generating plant from distances of this order , the problem resolves itself into two parts , concerned respectively with control operations and with instrument indications .sx For the control operations , apparatus similar in many respects to the now familiar supervisory control gear has been used .sx The actual control switches energise relays of the telephone pattern and the control voltage is 48 , this being the highest for which standard telephone gear is suitable .sx Suitable interposing relays are used between the telephone relays and the main contactors and trip coils for oil circuit breaker closing and opening .sx The control voltage of 48 is used for the operation of indicating lamps .sx The indication of voltage gives rise to few difficulties .sx The secondary voltage used is 55 , this lower value being adopted as a telephone cable is used to transmit control and instrument currents .sx Indicating voltmeters are of a special sensitive pattern so that the relatively high resistance of the connecting wires between the instruments and the voltage transformers does not impair the accuracy to any appreciable extent .sx The plugging arrangements at the control point are such that voltmeter and synchroscope indications cannot be obtained simultaneously , neither can a circuit breaker of a generator be closed till the sy-nchroscope plug is inserted in the jack corresponding to this machine .sx For the remote indication of current , special current transformers were developed having a ratio of 5 to 0.1. The primaries of these transformers are connected in the secondary circuits of the main current transformers at the power station , and the secondaries , giving a ratedfull-load current of 100 milliamperes , are connected by means of the cores of the control cable to the ammeters at the control point .sx