The International Steam Pages
"Supercharging" the Traditional Fireless Steam Locomotive
The ideas presented in this brief paper include input from other fireless steam locomotive enthusiasts. Gary Litzkow in the USA has been researching a variety of appropriate low-melting point metals that may hold enough energy in the latent heat of fusion, to extend the operating range of the traditional fireless locomotive. Steam power enthusiast Michael Bahls from Germany suggested that geothermal energy would be a desirable source by which to replenish the energy supply of fireless locomotives. Ian Bull (UK) and Thomas Wagner (Germany) provided information regarding an early generation of failed fireless steam locomotives that used heat of fusion technology. This information can provide a guide by which to research a more reliable fireless locomotive concept.
In 1992, Scientific American dedicated an entire magazine issue to energy. The articles on solar energy revealed that the sun was supplying the earth with over 16,000-times the amount of energy per day, that mankind was consuming. Solar thermal panelling can be used as a means to re-energise a fireless steam locomotive. By 1992, the cost of solar thermal energy conversion in arid, tropical geographic regions was already becoming cost competitive with more tradition fossil fuel energy conversion technologies. Solar thermal energy conversion has so far demonstrated that it incurs higher energy conversion efficiencies, lower capital costs and longer life expectancies than solar-photovoltaic technology. Several recent developments in the world of energy offer some future hope to the fireless steam concept.
There is high incentive to reduce atmospheric carbon emissions worldwide, including in non-Kyoto Accord signatory countries like the USA, where some astounding advances in atmospheric carbon emissions reduction is presently underway. The Clean Coal Technologies people are researching an idea to transfer carbon dioxide from ocean-side coal-fired power stations directly into ocean water, which happens to be the world's largest repository of carbon dioxide. Several other industries that use coal may be located within close proximity to such power stations, gaining access to having their carbon dioxide emissions sent into the ocean as well. Fireless steam locomotives may be among the range of transportation vehicles that could have their energy supply replenished this way, being recharged on steam raised by boiling ocean water (in coastal regions). The remaining concentrated brine may be used as a thermal energy storage medium.
Competing rechargeable locomotive concepts would include concepts operating on battery power, compressed air (inluding liquid nitrogen), as well as hydrogen PEM fuel-cell technology, all receiving electric power from thermal power station in certain geographic locations. Thermal power stations typically deliver 40% efficiency from the coal bunker (natural gas inlet) to the electrical power line. Batteries typically return 50% of the energy to recharge them, while electric motors deliver 81% part-load efficiency and 91% full-load efficiency ...... giving an overall 16%-efficiency from thermal power station to the drive axle. Fuel cell vehicles typically return 30% - 35% of the electrical energy needed to produce the hydrogen, yielding an overall efficiency of 12% - 14% from thermal power station to drive axle. A fireless loco can recharge on thermal energy at an effectiveness of up to 95%, while direct-drive steam expanders capable of operating at 16% - 20% do exist, making the fireless steam loco very competitive in terms of its energy usage from a thermal power station.
A traditional fireless locomotive stores hot saturated water in its pressure vessel. If the pressure vessel hold the saturated water at 250-psi (401-deg F), the enthalpy of the saturated liquid is 376.1-Btu/lb, yet the enthalpy of the saturated steam is 1201.1-Btu/lb. The liquid in the vessel has to release 825-Btu/lb to transform liquid to vapour in order for the fireless steam locomotive to operate. During the heyday of fireless steam operation, Dr. Gilli who worked for the Henschel group, developed a high-pressure fireless locomotive that held saturated liquid at 1000-psi (545-def F) in the pressure vessel. The liquid has an enthalpy of 550-Btu/lb while the vapour has an enthalpy of 1192.9-Btu/lb, transferring 650-Btu/lb from the liquid to facilitate the transformation. Saturated water typically has a heat capacity of 1.1-Btu/lb-deg-F. The transfer of thermal energy from liquid to release vapour causes a considerable energy drain in the pressure vessel.
Borrowing from the research of Gary Litzkow, it would be possible to reduce this energy drain by using thermal energy from an insulated tank of molten aluminium (aluminum in the USA) and replenish a portion the thermal energy that is lost in the accumulator or pressure vessel of the traditional fireless locomotive. This would serve to extend the operating range of locomotive. The aluminum melts at 645-degrees C (1193-deg F), has a latent heat of fusion of 170-Btu/lb and can be function an infinite number of cycles of re-heating and deep-cycle draining. To supercharge the pressure vessel with thermal energy from the molten aluminium, the aluminium would be carried in a separate insulated tank containing a heat exchanger to superheat steam, as well as several heat pipes to reheated/re-melt the aluminium.
Due to the corrosive nature of molten aluminium, the storage tank, the heat exchanger (superheater tube) and the heat pipes would need to be made from nickel stainless steel. The interior of the storage tank could be coated with silicon-nitride, an inert modern ceramic which maintains its mechanical properties up to 1400-deg C/2550-deg F, besides having exceptional thermal shock properties. The superheater could be encased in carbon fibre for tensile strenghtening, since this chemically inert material can withstand extreme temperatures. The heat pipes would most likely contain sodium, which melts at 205-deg F and is able to transfer heat from an external source (gas combustion or intense solar thermal energy transmitted through artificial sapphire fibre-optic lines). Material like zirconium-oxide, which is has a very low coefficient of thermal conductivity, could form part of the insulation of the tank containing the molten metal. Multiple layers of vacuum insulation would be needed to reduce thermal energy loss from both the tank containing the molten metal, as well as the pressure vessel containing the saturated water.
Using pure molten aluminium as a means of thermal energy storage may avoid the "caking" problem that occured on a European fireless steam commuter locomotive that used sodium hydroxide (NaOH) as thermal energy storage material. Sodium Hydroxide has a relatively low level of thermal conductivity, while the sodium - oxygen bond is a relatively weak bond with a propensity to dissociate at high temperatures, a characteristic which have comprimised the performance of the NaOH fireless locomotive. Aluminium's relatively low cost and ease of availability contributes to its attractiveness for use as a thermal energy storage material, having a relatively high level of thermal conductivity (249-Watts/metre-deg C at 400-deg C) at high temperature. In mobile operation such as in a fireless locomotive, molten aluminium has the potential to offer a higher level of performance and greater reliability as a thermal energy storage compound, than molten sodium-hydroxide.
New and future development of high-strength, high-temperature, corrosion-resistant ceramic materials may allow for compounds like lithium carbonate [Li2CO3], which melts at 723-deg C /1334-deg F with 224 - 260-Btu/lb latent heat of fusion, to be used as a thermal energy storage/"supercharging" medium. Other possible compounds may include Li3AlF6 with a heat of fusion of 229-Btu/lb. Suitable materials for use with lower pressure (250 - 300-psi) and lower temperature (401-deg F - 418-deg F) accumulators would include Li2BeF4 (Lithium Fluoroberyllate) which melts at 472-deg C/882-deg F with 190-Btu/lb heat of fusion, or LiOH (Lithium Hydroxide) which melts at 462-deg C/864-deg F with 186-Btu/lb heat of fusion. Adding this compound to aluminium would yield Li3AlO3, a small amount of which could lower the melting point of either pure aluminium or of Li3AlF6. Metallic oxides and other metal compounds having higher melting temperatures can be mixed, lowering their melting points and allowing for their use in thermal energy storage applications. Research into the possible polymerization of aluminium is presently underway in the laborataries of several aluminium producers. It is possible that several of the new compounds may havle properties that could make then quite desirable as thermal energy storage material.
In a modified high-pressure fireless locomotive (1000-psi /68.5-bar; 544.5-deg F/ 285-deg C), saturated steam would leave the pressure vessel through a throttle valve and be superheated in the heat exchanger located in the tank of molten aluminum. The steam temperature could rise from 544.5-deg F to between 600-deg F to well over 1000-deg F, depending on the effectiveness of the superheater/heat exchanger equipment. If the superheated steam temperature is near 600 - 650-deg F, the superheated steam would go directly to the steam engine, to provide propulsion. If the superheated steam temperature rises over 800-deg F, the steam could then be flowed through a second heat exchanger located inside the pressure vessel. This heat exchanger needs to be designed so as to enable the superheated steam inside the tube to drop to 600 - 650-deg F (remaining in the superheated range), while supplying thermal energy to the saturated liquid in the pressure vessel. To convert the saturated liquid to saturated steam at 1000-psi requires a transfer of 650-Btu/lb from the liquid. Thermal energy transferred the tank of molten metal to the pressure vessel could partially compensate for this energy depletion, by delivering 250 - 300-Btu/lb at a higher temperature. This energy transfer would both maintain higher temperature and higher pressure levels in the saturated liquid in the pressure vessel, extending the operating range of the fireless steam locomotive.
The superheated steam (that dropped from 800 - 1,000-deg F to 650-deg F) would be expanded in the steam engine. Whether or not this steam would be re-superheated by the molten metal depends on the effectiveness of possible heat exchangers and the type of expander being used. If oil-lubricated pistons are being used, a steam inlet temperature of 600 - 650-deg F would suffice, while ceramic engines like the German-built Spilling oil-free steam piston engines (or a similiar engine from Enginion) allow for re-superheating to over 1000-deg F. The use of the tank of molten metal also allows re-superheated compound expansion to be used on fireless steam locos, however, for optimal efficiency to be realised, the high-pressure and low-pressure cylinders need to be properly synchronised. Past experience has shown that at short cut-offs on the high-pressure cylinders, the low-pressure cylinders travelled mainly as passengers on most unsynchronised compound expansion (Mallet) steam locomotives.
A well-designed ceramic uniflow steam piston engine operating at high inlet pressures (1000-psi) has already shown that the concept can deliver higher levels of thermal efficiency than most compound expansion conventional cylinder designs, when steam leakage between the silicon-carbide piston rings and silicon-nitride cylinder walls can be kept to a minimum. In a 90-degree Vee-2 layout, this type of engine could drive the traction wheels directly (in a manner similiar to the Henschel V-8 steam loco), or be frame-mounted driving through splined double-jointed driveshafts into the power inputs of monomotor trucks/bogies. Dr. John Sharpe (UK) researched a compound expansion steam engine concept where the LP cylinder exhaust would energise the turbine of a turbocharger, which would drive the turbo-compressor and re-compress HP cylinder exhaust steam prior to it being re-superheated for expansion in the LP cylinder.
A short compound expansion (uniflow) steam engine can be built so that its end profile would resemble the end profile of the Volkswagen "W-8" engine. This concept would combined the Vee-engine concept that Honda developed for their V-2 "Shadow" series motorcycle engines. Honda was able to counterbalance the primary vibration of a 45-degree V-2 engine, using a crank-mounted counterweight, something previously only possible on a 90-degree Vee-engine. Honda split the crank throws, using the formula "Vee-angle + 1/2 crank split angle = 90-degrees". On their 45-degrees V-2 engine, Honda uses a 90-degree split between crank throws, resulting in one cylinder being 135-degees out of phase with its companion. In a synchronized (reheat) compound 4-cylinder engine, the two HP cylinders operate at 90-degrees out of phase, while the two LP cylinders trail by 45-degrees. Combining the Honda and Volkswagen Vee engine concepts, a 135-degree V-4 engine is possible. The four cylinders can be set 45-degrees apart from each other. The two HP cylinders would be spaced 90-degrees apart, as would the two LP cylinders, but trailing by 45-degrees (#1 HP at 0-degrees, #1 LP at 45-degrees, #2 HP at 90-degrees, #2LP at 135-degrees). The HP cylinders would operate on one crank thrown, while the two LP cylinders would operate on the companion crank throw that split at 90-degrees, identical to the Honda concept. This short engine can be frame mounted (transverse crank), driving directly into the input of an existing "monomotor" truck/bogie.
Extending the operating range of fireless steam power would also involve the use of improved, more efficient steam engine technology. In Russia, research engineer Victor Gorodnyanskiy has researched a very unique design of oil-free ceramic steam piston engine that can use steam at 650-deg C (1200-deg F) and that by his calculations, could operate at 30% -35% efficiency range. In the USA, the Turboflux company has been researching a small single-pass turbine engine (500-Kw to 1,000-Kw) that could theoretically operate at a 25%-35% thermal efficiency level, including using superheated steam. In locomotive operation, a (costly) electric transmission would have to be used with this engine to transmit power to the drive wheels. Numerous designs of positive-displacement rotary engines, including a few that can operate on superheated steam and at high levels of thermal efficiency, have appeared in the USA (Western Locomotive Group, Boise, Idaho, and also the Henry Engine group), Canada (Group Quasiturbine) as well as several companies in Europe.
To reduce the recharge time of fireless steam locomotives, thermal energy may be stored in insulated stationary thermal tanks. This would be applicable in hot, arid regions where solar thermal energy would be cost competitive against other energy sources. A low cost thermal storage medium would be mixture of aluminium oxide (Al2O3) , silicon dioxide (SiO2) and water, in a 1:2:2 ratio (Al2O3 2SiO2 2H2O) and which melts at 425-deg C or 797-deg F. Heat stored in this compound could be used to raise steam (boiled from ocean water in arid coastal areas), which would be injected into the fireless locomotive's accumulator (pressure vessel) through a perforated pipe, during thermal re-charging. Other low-cost thermal storage materials include a variety of salts (including NaCl), which may be used at stationary thermal stations. The locomotive-mounted tanks of molten metal would either be designed to hold enough energy so as to allow for longer journeys, or thermal recharging of such tanks may be done by a variety of means such as combustion of gas, or by focusing direct concentrated solar thermal energy being focused on to the heat pipes (via fibre-optic cables carrying infrared light).
The use of thermal supercharging of the pressure vessel could theoretically enable the operating range of the traditional fireless steam locomotive to be extended to 50 - 100-miles, while operating at a moderate rate of speed. Such characteristics would be suitable for use in a variety of services on small, tropical island nations. Fireless steam locomotives may also be used in tourist and excursion passenger train services, as well as in short line and branch line operations in both developed as well as in developing nations, where they may operate in regional service. Their energy, operating and maintenance costs would be very competitive and be well below the levels of numerous other locomotive designs. To enable operation in arid regions with a limited supply of water, a Ranotor condensor may be used to recover spent steam, storing it in a water tank car.
Future fireless steam railway traction sourcing sloar energy, will face competition from other electrically-based technologies. Battery powered locomotives can be recharged from solar photo-voltaic technology (converting the UV spectrum at 9% to 26% efficiency). Photo-voltaic technology is at present more costly per kilowatt and has a shorter optimal operating life expectancy than solar thermal technology. Deep-cycle batteries have typical optimal operating life expectancies of 1,000-deep drain cycles, whereas solar thermal storage technology can endure over 1,000,000-deep drain cycles. Repeated full power operation on fuel cells (both PEM and also solid-oxide or SOFC) also reduces life expectancy. Batteries will typically return 50% of the power originally stored in them, while at part-load operation, electric motor efficiency drops from 91% to 80% (overall efficiency 3.6% -10.4% from PV panel to traction/drive-axle in battery locomotive). In city transit bus operation involving PEM fuel cell buses, the typical published energy efficiency is 30% - 35% (overall efficiency 2.7% - 9.1% from the sun to drive-axle for a fuel cell locomotive).
In terms of capital cost, long term operating cost, service life expectancy, replacement costs of componentry and overall energy efficiency, modern fireless steam power would be very competitive against other oil-free technologies. Solar thermal technology can raise superheated steam from the infrared spectrum at an effectiveness of near 80%. If a uniflow steam engine can deliver 18%-efficiency at part load (Ted Pritchard achieved over 19% in a steam-powered road vehicle in Australia), with 85% of the stored thermal energy retained for use, a fireless steam locomotive could achieve an overall efficiency of over 12% (from the sun to the drive axle). Nevertheless, the concept of future fireless steam traction will remain a research concept for now.
Harry Valentine, Transportation Researcher, firstname.lastname@example.org
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