Reply #18: Solar Train

[aztc]

I was thinking about how a steam locomotive could be converted to use solar thermal energy to replace or supplement other fuels to provide the heat and found the following two articles by Harry Valentine that seem to indicate all of the major technical issues have been solved for decades. Imagine if we spent a fraction of what we are spending on war to develop a transit system based on these ideas!

Tim

Researching a GPCS-Accumulator Steam Locomotive

The hybrid-accumulator steam locomotive idea described in this article is based on input provided by Michael Bahls (Germany) and Robert Ellsworth (USA).

A GPCS-accumulator locomotive would combine the advantages of a fireless steam locomotive with features of a conventional steam locomotive. It would borrow technology from both, combining the high-pressure (1000-psia) accumulator of a fireless locomotive with a GPCS (gas producer combustion system) firebox. Water in the locomotive’s accumulator (filled to 75% to 80% capacity) would be heated by injecting pressurised superheated steam into the water through a perforated pipe located near the bottom of the accumulator, a practice pioneered on classical fireless steam locomotives. Water would be heated to the operating temperature and pressure levels (1000-psia at 544-deg F). GPCS-accumulator locomotives would have their water supply replenished and be thermally recharged at industrial sites where high-pressure steam is available and where other types of fireless steam locomotives are recharged.

To maximise power output and operating duration, the locomotive would need to be built to the operating railway’s maximum right-of-way clearance dimensions. Several world railway systems allow railcars are built to a length of 85-ft (between couplers) and a width of 10′6″, on 60-ft truck/bogie centres. On such a railway right-of-way, the locomotive accumulator may be built to an inside diameter of 7-ft and interior length of 65-ft (10′6″ exterior diameter and 70-ft exterior length), yielding a volume of 2500-cu.ft and holding 90,000-lb of saturated water at 1,000-psia at 80% capacity. The front end of the locomotive could be extend by using a tapered section (containing the driving cab) with the coupler mounted on an extended bogie/truck. The non-tapered end would house the GPCS firebox and be semi-permanently coupled to a fuel tender unit. The locomotive would measure 95-ft to 100-ft from front-end coupler to tender. A driving cab could also be located either on the tender, allowing bi-directional operation.

Prior to the GPCS-accumulator locomotive entering or re-entering service, the accumulator would be filled to 75% volume with hot, pressurised saturated water. It would be further heated with superheated steam to a volume of 80%, a temperature of 544-deg F and 1,000-psia pressure. This would provide one-third of the locomotive’s required total thermal energy, which could be supplied from such sources as concentrated solar energy or heat-pumped geothermal energy. While in operation, the locomotive would be able to combust various forms of low cost, clean burning, low heat content (5,000 to 9,000-Btu/lb) biomass, including bio-fuel pellets, poultry litter (eg: Thetford Power Station, UK) or even bagasse carried in a semi-permanently coupled tender unit. Automatic fuel feed (stoking) using an auger screw mechanism would transfer fuel into the GPCS firebox, located on the locomotive section. Combustion ash could be transferred by a smaller auger into a holding pan located under the tender. During service lay-overs, the ash pan would be emptied (biomass ash is a fertilizer).

When the locomotive is in service, steam leaving the accumulator through the steam dome would be superheated to 1200-deg F in the GPCS firebox, then flow into a heat exchange pipe located inside the accumulator at its lower level. Saturated water at 1,000-psia and 544-deg F has an enthalpy of 542.6-Btu/lb in the liquid state. For this liquid to flash into steam, it would need to draw 650.4-Btu/lb from the remaining saturated liquid. The steam in the steam line would replenish this heat by making 4 to 5 successive passes through the firebox (for re-superheating) and lower level of the accumulator. This heat exchange steam line would allow 650-Btu/lb to be added to the saturated water, maintaining optimal accumulator temperature and pressure levels. The 6th re-superheat would occur prior to the steam being expanded in the steam engine, with a possible 7th re-superheat being used for compound expansion . A variety of positive-displacement single and compound expansion steam engine designs may be located close to the GPCS firebox, directly driving the axles.

More here:
http://fuelandfiber.com/Athena/bb/viewtopic.php?t=44