--- "R.C.Macaulay" wrote: > "An open pond with a "foam blanket" to cover the CO2 works. Interesting that many small towns have waste water treating plants that are nothing more than a series of ponds located in steps where the first pond gravity flows into the next lowest earthen pond and so on. These "lagoon" systems could provide an ideal site for green machines. Task...find a better way of producing huge quantities of CO2 ... is there a way?"
Well - not sure "huge" is the correct description when you are directly recycling the exhaust from a gen-set on a continuous basis. The plant operator will need some additional source of carbon, to make up for the expected shortfall. But how much, percentage-wise, is an important open question. Assuming that a turbine gen-set returns all the waste heat and CO2 from combustion to the Algae ponds immediately, then the situation will resolve to how much CO2 is lost there, due to admixture with the atmosphere before the algae use it. The amount of CO2 already in the air will NOT contribute noticeably- there is simply too little concentration to matter. CO2 is of course much denser than air but totally miscible over time, so the foam blanket would be a key feature - but it may provide enough of a necessary "delay," so that the CO2 is almost completely converted by the algae, before it can mix. If you have ever watched bacteria 'double' under a microscope, the growth rate is mind-boggling. Of course, only the best strains need to be used, and bio-engineering may eventually provide even more than the bonanza which nature now gives us. Along with careful metering of CO2 and proper 'plumbing', the intrinsic shortfall could end up at only 5-15% CO2 which is lost, and most of that would be in bad weather (high winds). This is a major unknown. Here is the way the dynamics of the system might work, using a modification of the Aquafuel (carbon reforming) process. First, here is an old page from JNL on how the basic system works in a small experiment. Some of the underlying old patents are mentioned. http://jlnlabs.online.fr/bingofuel/html/aquagen.htm I would envision a slightly different approach where the electrodes themselves are NOT rapidly consumable. But in which a carbon-rich "goo" (algae with some added coal dust or sawdust) is pumped through porous electrodes (tungsten?), to create the same effect as if they were consumed - as in the simple experiment above. In summary, in addition to the algae 'scum' which is continually skimmed and dewatered, some additional percentage carbon needs to be added to make the system fully 'perpetual'. This added carbon could be Ag-waste or coal dust. The goo-mix is then continually pumped through the electrodes to reform the mixture into carbon monoxide and hydrogen, which is then ported to the turbine. It is then immediately recycled and very close to carbon neutral. Bottom line: there are strains of algae which when 'force-fed' CO2 will convert solar energy to biomass at an astounding efficiency- which blows away the best solar cells, and at a tiny fraction of the cost. But-- with grater complexity in a working system. Some of the electrical output must be returned to the bio-reformer of course; and that parasitic loss is the second looming 'unknown' factor. If it is not substantial, then this is a fabulous implementation. If too much current is required to accomplish the reforming, then of course the huge amount of cheap solar energy which is collected by the algae will not be enough to make the system economical enough to supplant burning coal without exhaust recycling. This is the kind of complex concept which cannot be easily modeled by computer, and begs for a prototype system, based on the optimum pond size for a single pond. It seems to me now, after tossing around all the alternatives for a few months, and looking at the proposals and comparative strengths and weaknesses, that a central pivot, circular pond would be best (~40,000 ft^2, about an acre). The 'racetrack' or other rectangular configurations have too many negatives. It is far cheaper to harvest the algae from still water than to try to create a continuous flow. The visual image of central pivot farm irrigation comes to mind, but in this case the "arm" is both the skimmer and part of the CO2-return plumbing. The beauty of this kind of system is that the skimmed algae, after very slight treatment, can be immediately reburned. Thus, we have the quasi-perpetuality. Of course, this is simply 'assisted-solar-conversion' on the bottom line. It is possible that any individual carbon atom, if it could tell its own story, gets burned and reconverted into biomass as often as 2-4 times a day in the summer months. The net inventory of CO2 is not enormously large but there is still toxicity and risk of suffocation, so precautions will need to be taken. Jones
