At 11:02 PM 4/18/5, Stephen A. Lawrence wrote: >Horace Heffner wrote: > >>The vast majority of the hoped for 200 MW power then has to be from the >>bouyancy due to the difference in ambient temperature (and thus column >>bouyancy) between the base and the exit of the flue. This sounds like it >>needs some checking. [ ... ] The use of base >>solar collectors is now looking almost entirely irrelevant. >> >> >I didn't check your numbers but this conclusion _must_ be wrong. > >Sanity check: > >Under stable atmospheric conditions the temperature drop with increase >in altitude is greater than or equal to do the drop which results from >adiabatic expansion of a parcel of air as the air rises.
Yes, you're right. I forgot to compensate for heat lost to expansion. I assumed a constant temperature up the flue after priming. The surface temperture would have to be elevated, due to warm soil or a greenhouse, to get any bouyancy after priming. It is still curious that ideal overhead sun conditions for 20 km^2 would collect 20,000 MW, yet the solar tower with 20 km^2 only generates 200 MW. Assuming a loss of 75 percent due to sun angle and night, there is still an average of 5,000 MW, so the solar tower efficiency in capturing this is only 4 percent. It seems I must have some other mistake as well. I would think the tower would be capable of a higher efficiency. Assuming a higher efficiency can be or is obtained, it would be very handy to piggyback a nuclear or coal power plant into the deal, and use the tower to generate electricity using the waste heat. Also curious is the fact that heat pumps can operate at a COP of 5. If a tower were 30 percent efficient, then it could mechanically drive its own heat pumps. Regards, Horace Heffner
