| Estimating Energy for Blister Steel Production David Dietzler, 2007 A carburizing box about 5m x 5m x 1m containing almost 200 tons of iron with walls of cast basalt about 0.5 to 1 meter think and a layer of packed regolith one meter thick surrounded by a braced steel jacket about one inch thick will require a lot of energy to heat the iron up to 1000 C. However, the insulating properties of regolith will reduce energy demands to keep the iron hot for seven days as it absorbs carbon. Only crude estimates can be made here. Q = (200,000,000 gr.)(1000 deg.)(0.450 j/gr. K) = 9E10 j = 25,000 kW./hrs. If ten hours is taken to heat up the iron then 2500 kW of power is needed that can come from 25,000 square meters (160m x 160m) of solar panels generating 100 w/m^2. This does not take into account the efficiency (or inefficiency) of induction heating or thermal losses from the box. Q = (k * t * A * T)/ L If k for regolith is 0.01 W/mK t = 604,800 seconds (7 days) A = 70 square meters L= one meter Q = 117.6 kWhrs. Heat conduction through one meter of regolith. A 0.7 kW power source could supply the necessary energy for 7 days. The problem is complicated by the fact that the carburizing box rests on highly insulating regolith that will reduce heat loss in that direction. The lid will probably have a thinner layer of insulating regolith. The weight stress on the box will not be very great in lunar gravity. Heat that is conducted thru the cast basalt or ceramic blocks will move slowly through the packed regolith insulating then heat up the steel jacket. The steel will radiate heat into the vacuum according to: P = e * b * A * (T^4 – Tinf^4) The shiny steel will have low emissivity and temps of the lunar day might rise to over 120 C. I can only conclude that substantial amounts of energy will be needed to heat up 200 tons of iron but very little energy will be needed to keep the iron hot as it converts to steel if the carburizing box is well insulated. Initially, smaller amounts of steel will be produced during lunar dayspan until silicon solar panels farms are built on the Moon to supply more power. Once one 5mx5mx1m box is heated up only 7 square meters of solar panels rated at 100w/m^2 will be needed to keep it hot and the large solar panel farm can be used to heat up another box. |
 |