Last edited by Liberty4life; 03-06-2012 at 07:40 PM.
Remember humans are people too.
FUEL ETHANOL PRODUCTION AT HOME (*)
It's actually fairly easy to build a reflux still to make 180+ proof ethanol in a single pass, and that's what I recommend for anyone who is dead set on doing this. Sure, a cheap pot still is great to get your feet wet, but anyone serious about producing their own ethanol fuel has to use a reflux still. The process is very simple, and I can explain it here. Note that while I have made my own wine for many years, I have never distilled it. However, I've done research on the process and I have an engineering background. Basically, you mix your sugar source in the proper concentration with water, then pasteurize it to kill bacteria and undesirable yeasts. Add your yeast and let it ferment to completion (usually a week or so). Now you're ready to use the still. The still is a pot with a reflux column. This column is simply a tall vertical pipe loaded with small rocks or marbles. The pot is insulated against heat loss. The column is not normally insulated, or it is weakly insulated. Now, a mixture of alcohol and water boils below 212F. As the vapors rise through the packing (i.e. the rocks) they continually condense and re-vaporize on the surface of the rocks (note that the heat lost from the column allows this, and the heat loss rate is important here - the best way to determine the proper rate is through experimentation). In effect, the column provides multiple distillations without using any extra energy or time inputs on your part. The most important element in the process is to keep the temperature at the top of the column within a very narrow range. The temperature you want is just above the boiling point for ethanol which is about 173F. The vapors enter the condenser immediately after they leave the top of the column, then you just collect the liquid ethanol.
Yes, it's that easy.
* This discussion is relevant to this thread because saturated steam at or near atmospheric pressure (such as the steam exhausted from a steam engine) is an excellent source of heat for a fuel ethanol still. The steam can be passed through a copper heat exchanger placed in the pot of the still. A bit of tweaking would find the ideal parameters to allow for fully automated operation (without fancy schmancy electronic equipment because the temperature of the heat exchanger is set at a constant 212F). The boiling point of an aqueous ethanol solution is less than 212F, but the boiling point of the solution will rise and approach 212F as ethanol is removed. This will lower the temperature difference between the heat exchanger and the solution. So, the evaporation rate of the solution will also fall. However, the heat loss rate from the column will not fall. What will happen is as follows: some ethanol will condense before it reaches the top of the column as latent heat is lost from the alcohol vapors. While this will lower the overall efficiency of the system somewhat, it doesn't matter because you're using essentially free heat from the steam engine exhaust (besides, you still get most of the heat from the steam exiting the heat exchanger in the pot since most of it is not condensing there, and you can still harvest the heat from the column and ethanol condenser if you want to). The ethanol production rate falls as the distillation progresses, but the proof of the ethanol if anything will go up under these conditions. Now, once the vast majority of the ethanol has been removed from the solution, you will get virtually no evaporation (since the boiling point of the solution is now near 212F => no temperature difference => no heat transfer). So, in principle, it's possible for such a system to operate unattended, yield high proof ethanol, and with no dedicated control system... and purely mechanical. NOTE: The exhaust from a small steam system can be easily maintained at a temperature higher than 212F through various means, and keeping the temperature higher than 212F can ensure all ethanol is harvested from the solution. As long as a small steam system is operated at a constant output, then the still can be configured for this output to allow for a fully automated operation by sizing the column properly to allow for a sufficient heat loss rate to minimize carryover of water.
In general, this is economically viable only if you have a source of inexpensive fermentable sugars, and if you use a cheap source of heat for the distillation. For example, using electricity to power the still is not economical unless you put to use the heat thrown off the still (do the math, you'll see). On that note, anyone who wanted to the do this optimally should collect the heat from the ethanol condenser for heating applications (say, water heating). Hell, you could even put the still in a corner of a room when electric heat is used and use a fan to blow the heat around the room - this way you would catch ALL the heat. So, in principle, if someone uses electricity for heating, then using electricity to power a still could be done with all of the heat thrown off the still harvested for heating applications. Essentially, this would be like powering the still for free.
A good video: http://www.youtube.com/watch?v=DR7qIMMxH6Q
ADDENDUM: Adding zeolite to the aqueous ethanol solution that leaves the still can remove most of the water to achieve a 97-99% ethanol solution. This can then be blended with gasoline up to 50% and used to fuel modern automobiles directly. See Steven Harris as www.imakemygas.com. NOTE: It may be that silica gel (crystal cat litter) will work in lieu of zeolite.
ADDENDUM: Warning Not to Use E15 In Modern Cars (NOTE: It's hard to know what the truth is here since there are so many conflicting positions from "experts", but people should know both sides of the issue).
Last edited by buenijo; 03-06-2013 at 04:44 PM.
"There seems to be some perverse human characteristic that likes to make easy things difficult." - Warren Buffett
I'm toying with an idea that I'll share on this thread since it involves steam. I remain convinced that a modernized piston steam engine with good thermal efficiency and fueled by biomass would be an ideal off grid power plant. However, until these become available I will consider other options.
One of the main benefits of a piston steam engine is the ability to operate at very low power for extended periods while providing heat in a convenient package. Steam is an excellent heat transfer medium. So, I considered, why not devise a simple biomass fueled steam generator for heating applications? Furthermore, since my recent research shows that charcoal gasifiers can power very small engines cleanly and with impressive energy density, then how about a system that chars wood chips at a controlled rate and combusts the pyrolysis gases to generate steam on demand? The charcoal produced from the system can then be stored for use as required in fueling small engines.
I'll describe a basic configuration. Particulate biomass like wood chips is gravity fed through a vertical pipe section. A hopper is connected to the top. A lower section of the pipe is surrounded by a combustion chamber fueled by pyrolysis gases generated from the heated wood chips. The idea is that the rate at which pyrolysis occurs is directly proportional to the rate at which the biomass feeds through the system. So, it's possible to control the rate of steam generation as a function of the speed of the motor that drives an auger to pull charcoal that accumulates at the bottom of the pipe. A steam generator tubing coil is placed above the combustion chamber in the annular space between the pipe and exterior shroud used to form the combustion chamber. The draft draws air into the base of the system to cool the lower pipe (and charcoal within) and combust the pyrolysis gases escaping from a ring of holes in the inner pipe at the base of the combustion chamber. These hot combustion gases pass over the steam generator coil before heating the hopper that contains the fuel (thereby drying and/or preheating the fuel before it enters the pipe).
The steam generated is sent through an insulated line to a high point in the system, then distributed to various heating applications. This is controlled in two ways. First, each load has a valve to control flow. Second, the final pass of the steam/condensate is through an insulated water storage tank. The temperature of the water in this tank is used as a control for the charcoal auger.
POTENTIAL PROBLEMS: It's likely that tar vapors generated during heating will condense throughout the system and generate a real mess inside the system. I don't consider this to be a serious problem by itself. However, it might cause some problems like fuel bridging if the tar accumulates and gums up the wood chips. I doubt a sufficiently large diameter feed tube would see this problem. Just in case I would suggest an 8" diameter feed tube for initial testing and large wood chips and chunks that don't present so much surface area for tar to condense.
ADDENDUM: My research suggests that the yield from an efficient charcoaling process should be higher than I originally reported. It should be possible for the charcoal produced from such a process to contain about 40% of the energy in the wood. I had originally reported 1/3.
Last edited by buenijo; 05-01-2013 at 12:32 AM.
"There seems to be some perverse human characteristic that likes to make easy things difficult." - Warren Buffett
This is a continuation of the previous post. The system I described there is rather sophisticated, but I do not believe it would be inherently difficult to build after the prototyping were completed. Building a biomass fueled steam generator for heating applications (w/o the charcoaling system) would be a lot simpler. In that case, it's possible to use small pieces of rough cut firewood stacked onto a grate. The system burns at a low rate in updraft fashion to generate smoke continually that is combusted separately for heating a steam generator. The smoke is pulled out of the side of the unit by the draft generated by a flue placed next to the unit (I've seen such a system, and it works well). NOTE: The fuel hopper is closed at the top, air enters at the base of the fuel hopper via a grate, and exhaust gases leave at the top of the flue. The output is controlled by positioning a damper on the flue.
I've considered a simple mechanical thermostat by allowing the flue to be actuated by connecting a cable to an automatic window opener (see one example here: http://www.amazon.com/RIGA-Auto-Open...+Window+Opener). The idea here is that the window opener can be placed in a central location in the home to monitor temperature, and position the damper accordingly. Using a steam radiator with some size and thermal mass seems like a good idea. NOTE: Something like this might be devised to generate a lot of charcoal if the grate were configured to allow large pieces of charred wood to fall down into a collection chamber. The benefit of this approach is that the wood does not have to be chipped, and no auger is required.
ADDENDUM: For those who have never heard of a rocket heater or rocket mass heater, then you should look into it. The best single resource is the permies.com forums. See an article here: http://www.richsoil.com/rocket-stove-mass-heater.jsp . It's possible to incorporate a steam generating system into this design. Normally the outside surface of the barrel must be open to the air to cool the combustion gases. This is what drives flow in the system. However, it's possible to insulate the outside of the barrel and provide a means to cool the combustion gases by placing a steam generator tubing coil around the outside top of the fire tube. I believe this can generate a strong draft even in a small system. This kind of system can be devised to burn at a low continual rate and controlled by the means discussed before. Furthermore, the top of the barrel of a rocket mass heater or the top of the barrel in this configuration can double as a cooking surface. In this case the top of the barrel could be insulated with a lid or insert that can be removed for cooking when desired.
Last edited by buenijo; 01-07-2013 at 11:07 PM.
"There seems to be some perverse human characteristic that likes to make easy things difficult." - Warren Buffett
See this study on steam jet cooling: http://www.crses.sun.ac.za/files/res...r/aj_meyer.pdf .
I am reconsidering yet again this configuration as an off grid space cooling system. One of the main things that has me reconsidering is my reading the results of several studies using water as the working fluid and with boiler temperatures of 250F or less. This will allow the exhaust from a steam engine to power the a/c system. So, the steam engine exhaust can either heat or cool the home. Furthermore, the furnace exhaust can heat water via thermosiphon, and and hour or two of tapping the steam exhaust can pasteurize all the water require each day. It seems a properly configured small steam system can be unmatched with respect to overall efficiency when all the energy is put to optimal use. Of course, I've made this argument all along.
Last edited by buenijo; 01-23-2013 at 07:23 PM.
I've come across some studies on desiccant evaporative cooling recently. The skinny on those is that certain desiccants like some grades of silica gel have been shown to be regenerated (i.e. dried) using heated air with surprisingly low temperatures. I've seen good results from 130-170F. The lower the temperature the higher is the required air flow rate which should be expected. The exhaust from a small steam engine can easily provide these temperatures, and the air flow rate required would not be high. Also, a small steam engine designed for a continual low output as I've argued for can be used to drive a blower fan mechanically off the engine flywheel. This blower fan can be used not for drying the desiccant, but for sending air through the desiccant beds, duct work, and the wet pad required (the evaporative cooling system). Using mechanical energy directly from the engine avoids serious energy conversion losses seen in the alternator, battery, inverter, and blower motor.
Also, I've considered what seems a fascinating approach to devising a continual desiccant evaporative cooling system. Well, it's fascinating to me at least. The only commercial systems I know of are the desiccant "wheels". These contain the desiccant in large flat discs or wheels that slowly rotate to reposition the desiccant material relative to the duct work. This allows heated air to dry out desiccant, then the dry desiccant rotates to another duct where air from the home can be dried before the air is sent through a wet pad for evaporative cooling. There are other systems like a heat regenerative wheel. While this is clever, it seems more difficult to build something like this than the following approach. What I propose is placing two separate desiccant beds in line with the duct work. One is heated and the other is used for drying. Small augers driven by a low power gearmotor continually transfer desiccant material between the two beds. So, silica gel beads are transferred slowly from the heated bed closest to the heat source up to the air drying bed while the beads at the bottom of the air drying bed are slowly transferred to the top of the heated bed. This solves the problem of having to devise a batch system that operates intermittently. In this configuration a small electric motor driven blower fan sends air at a low rate through a heater to continually send heated air through the heated bed, and this warm moist air is expelled to ambient. It should be efficient because there is wet and relatively cool material continually introduced to the top of the heated bed where the heated air is exhausted, so this newly deposited desiccant picks up the tail end of the heated air. Similarly, the air from the home is forced through the other desiccant bed such that the air passes last through the desiccant material recently sent from the heated bed. So, it gets exposed to the driest desiccant. Note also that the auger tube that transfers the desiccant from the heated bed to the drying bed doubles as a heat exchanger to cool the heated desiccant before it enters the drying bed, and since the augers operate at a low continual rate there is plenty of time for cooling there. Also, as described in other posts, the water adsorption process generates heat, so the air passing through the drying bed must pass through a lot of duct work to dissipate this heat before it moves through the wet pad and back into the home.
Last edited by buenijo; 01-23-2013 at 07:30 PM.
Another approach to desiccant evaporative cooling has distinct advantages to using a solid desiccant like silica gel. A concentrated aqueous solution of calcium chloride can be used as a desiccant. The great advantage to this approach when used with a steam system is that a steam heat exchanger can be used to regenerate the solution directly through distillation. In this approach the concentrated solution is pumped and cooled before being sprayed into ducting through which air passes. The solution dries the air in the process, and the now dilute solution drains back to the regenerator to be reheated by the steam heat exchanger in a closed loop. As with other evaporative cooling systems, the now dry air passes through a wet pad for cooling before it reenters the home. Also, the desiccant may be sprayed onto the top of a bed of packing that provides a very large surface area with air passed through the bed from bottom to top. There are various packing shapes that may be used, but clean rocks of an appropriate size to prevent restricting air flow may suffice. This configuration with the flow rate of desiccant high enough to ensure the packing is constantly wetted by the desiccant should ensure intimate contact with the air as it moves through the packing, and this should achieve a good drying effect.
NOTE: BTW, it should be possible to use atomizing nozzles with high pressure pumps to spray these liquids for better results. In particular, sending the water through such nozzles seems a good idea to do away with the wet pad in a traditional evaporative cooler, and this should reduce the fan load considerably. The low liquid flow rates can allow these pumps to have low energy consumption. I suspect the desiccant flow rate is far too high to send through a pressure pump, so either a low pressure spray or send the desiccant flowing/dripping over packing material.
NOTE: I mentioned this in another post, but it's relevant here. In principle it is possible to devise an air drying system that requires no blower fans. It seems this approach might be more promising for a modest and genuinely off grid home. This approach is based on the fact that calcium chloride and other desiccants increase in temperature rather dramatically as they absorb water vapor. The air would be heated in the process, and this might be used to drive a convective air flow. So, imagine you have an insulated barrel filled with packing material (rocks, wood chips,... watever works best) over which the strong calcium chloride solution is dripped or sprayed to cover the entire material and drain to the bottom. The bottom of the vessel is connected to ducting from the home. As the solution absorbs water vapor from the air, then it's temperature rises. This vessel and a tall section of wide duct work on top of the vessel is well insulated. It may be that enough warm air will accumulate in the vessel and duct to induce a pressure difference and drive air flow at a sufficient rate for good results. Some things that can improve results include good insulation, low obstruction to air flow, and a tall and wide column of warm air. The top of the insulated duct is connected to uninsulated duct, and perhaps multiple parallel sections of such duct to provide cooling of the air before it returns to the home. As before, the solution that collects at the bottom of the vessel drains to a heater where it is regenerated. The steam given off from the solution during generation is used in heating applications, and it may be that the steam can be routed through a copper heat exchanger in the base of the insulated duct on the drying vessel to heat the air more aggressively and provide better air flow. If so, then the cooling duct work might need to be enlarged. I'm not interested in the engineering right now, these are just ideas for consideration. Anyway, when the steam returns to liquid state and cooled, then it is this distilled water that is used for evaporative cooling in the home. I like the idea of using a low volume high pressure water pump to send the water through atomizing nozzles in the home to avoid using blower fans.
Last edited by buenijo; 02-24-2013 at 12:43 PM.
Sanden is manufacturing scroll automotive compressors with belt drive. I believe these might make good expanders for use in organic rankine cycle engines. Unfortunately, the temperature of the waste heat from this kind of system is too low for use in many applications. Anyway, I think this is something worth trying. Please note it's necessary to remove the reed valve at the compressor discharge, and that the hot pressurized refrigerant vapor is then applied to the compressor discharge to operate the scroll in the direction opposite that it moves when used as a compressor (well, in theory anyway).
NOTE: Here is one small company working to develop this idea: http://www.eneftech.com/en/technology.php#turbine .
Last edited by buenijo; 04-10-2013 at 05:23 PM.
Looks like Mr. Desai is now making steam engines by modifying AIR-COOLED DIESEL ENGINES. Based on the photos, it looks like he is mounting double-acting steam cylinders and valve assemblies to existing Diesel engines using the stock engine piston/cylinder as a crosshead. Looks like the quality of his steam engines just went up.
ADDENDUM: Price for a 2.5 HP engine including shipping costs is $1500. It seems to be a very robust design. It weighs 200 lbs, is about 30" tall, and the base is roughly 18" x 18". The bore is 2.48", and the stroke is 3.15". Based on these dimensions, the engine should put out more than 3 HP at 150 psi steam and 500 rpm. It's got a very long cutoff which is not good for efficiency, but it will provide a lot of power at low pressures and speeds. Best case for net efficiency here is about 4%. The best this engine could do under optimal conditions with a shortened cutoff is probably 6% net efficiency, and at that point it might be worth it... 4% is just too damn low. To reach the higher efficiency a smaller eccentric would have to be fabricated and the position of the eccentric on the shaft would have to be altered to get a steam cutoff of 25-33% of stroke. The steam quality would have to be high, and thermal losses from the boiler and all other places would have to be minimized with good insulation and other means. Getting 8% net efficiency is possible by using two engines in a compound configuration and bumping up the pressure to about 200 psig. Unfortunately, small scale steam power really needs serious upgrading before it can be practical. Without it, I must advise against it. Use a wood gasifier if power from biomass is desired. However, if you really can put the heat from a steam engine to use, then it can be a practical option.
Last edited by buenijo; 04-27-2013 at 09:53 PM.