Ok lets go over what real world expections are with any gasifier technology.
First a gasifier (reguardless if its charcoal or wood fueled or who made it) is not a direct replacement for gasoline, LP or NG. Wood gas energy densities will constantly fluxuate this is due to a number of reasons. This energy density can range from 30% on up to 70% of gasoline energy density. It is not equal: not by a long shot!!. So if you are going into this with this belief you will be disapointed. A gasifier is running on a solid fuel; not a liquid or gas and is limited to what any gasifier can flow. A wood gasifier's reaction process will release moisture that is filled with sticky tar. This migrates into the fuel in the hopper. The fuel then becomes sticky and will stick to itself and the walls of the hopper. As this fuel migrates into the reactor it can then fuse together creating a bridge. Fuel in the hearth then burns out creating a void. Bridge breaks and raw unprocessed fuel then drops into the later stages of the process. Gas energy density plumets and tar is the result. Then this process starts all over again. Charcoal units can also bridge but are not as likely and tar is still not an issue. A gasifier has what we call a turn down ratio. This is the opperating range of the gasifier, so it is important the gasifier is correctly sized to the application. ( One size does not fit all ) There is a limit to how small of a load you can pull on the gasifier and a top limit you can pull on the gasifier. Too low of a load the gasifier will cool and the reactions slow down producing weak gas and tar will not be cracked. Too high the reactor can get too hot and simply burn out the chamber. There is only so much fuel that can be in the reactor at one time and fuel flows can only supliment the reactor so fast. So it is very important when running a generator that you never ever apply a load that it can not continuously sustain. This is because once the RPM's dive it may not be able to recover and a vicouse cycle will begin as the reaction process will contineu to crash.
Stationary systems without an opperator can only sustain the minimum gas energy density. As flows oscilate there will be a low point in those oscilations and if the load is beyond what the generator can sustain that vicouse cycle will begin. So you must load the machine no more than what the generator can sustain at these lower outputs. Even though at times it maybe able to pull twice this loading. A typical 450cc power generator can sustain a 1700 to 2500 watt load. Depending on fuel, what gasifier is used and other variables. Nothing in gasification is linear! < keep that in mind. Also note there is no such thing as a " set it and forget it " gasifier. They must be constantly monitored and you may need to interviene and make adjustments. It is the nature of the beast. Automation can help alieviate this but even it is not 100%. However, charcoal systems as they have free flowing hearths; will self sustain FAR better than wood fueled gasifier systems. Even if the wood gasifier is fully automated it still wil not self sustain as well as a non automated charcoal unit.
Intermittent loading: This is where you maybe running outdoor equipment like an electric log splitter or a small wood chipper; like I have demonstated on our Youtube channel. In this use, you can achieve the higher outputs as the loading is intermitent. You let the engine gasifier system rev up and you apply the load and you can typically achieve that 70% or even higher output. Then you drop the load and let it rev back up and you are ready to go again. Since you are there then you can make adjustments on the fly to optimize the perfromance.
Also a gasifier does not determin your power output or run time. This is determined by the generator or engine your are running. The gasifier is just the fuel source and nothing more. I get asked this all the time " How long will the hopper last? " Gee I dont know; are you trying to run a Frieght Train or Yugo?? That's like asking how far a gallon of gasoline is going to go. Are you driving a Honda Civic or a Chevy Suburban?? A power generator can only output so much on any syngas fuel from any gasifier designed to run it. Rule of thumb is to cut its rating by 50% and expect fluxuations in either direction. Net kW/hour rule of thumb is 3 lbs per kW/hour or 3 gallons of fuel per kW/hour produced. This is reguardless of the engine displacement. Just bare in mind some engine are more efiicient that others. So for instance the VFX-14 has a 30 gallon hopper. 30 / 3 = 10 kW/hours net energy output. The run time ( how fast the engine eats that fuel ) That is determined by the engine size not the gasifier. a 1 ltr engine running at 1800 rpms is going to take much longer than a 2.5 ltr engine running at 1800 rpms. But reguardless of the engine size the "net energy output" Or net kW/hours per the hopper load will be the same reguardless of the size of engine. Just the time it takes to get there. Make sense? Good! I knew you would get it :)
Quick NOTE: When off grid your battery bank has a C rating. So oversizing a unit beyond what your batteries rating will reduce efficiency. Size the system according to your charging loads.
Ok now running a gasifier as a primary power mover. This dont work! For one it is very inefficient to run a generator like this off grid requardless of fuel. A running generator reguardless of the load is eating fuel you are wasting fuel just powering light loads like lights and then the accational appliance loads. A small battery bank to run lights and light loads will be far more efficient and will make your life much easier. You then only need to run the generator for a few hours a day. Charge your batteries and then let the inverter manage that power you created. You dont need to break the bank on a battery system. If just for the occasional power outages you can get a cheap inverter and run lead acid batteries. However, if you are planning long term you really need to get LifePo4 batteries. They are actually cheaper because with lead acid only 50% of the amp hour rating is actually usable. So you will need twice the lead acid batteries to achieve the single rating of one LifePo4 battery. This stuff is not expensive anymore you dont have to spend a fortune here. Additionally if you are running for power, but are not in proximity of the gasifier; Well then there is no one there to optimize its opperation. So power output will constantly be all over the place its just not a good solution for this.
Engine stalling, yes its going to happen its a gasifier not a fuel tank. Its just the nature of the beast; again charcoal far more stable and this is much less likely to happen.
Now for Tar!! Aaaarrghh!! There is NO such thing as a tar free gasifier period!! No gasifier (not even charcoal) is exempt from producing tar and there never will be. If it can happen it will. Follow directions and guidelines and this will be less likely to occure and once again it is very unlikely this will ever happen with a charcoal gasifier. But it is possible. Use engine grade fuel and learn what engine grade fuel is. Wet fuel does not work, best advice is forget what others claim and dry the fuel to zero moisture content. Never use a wood gasifier on engines bellow 1000cc it simply does not work. You might get lucky a few runs but eventually you are going to tar up your engine I promise you that. Ive been there and done all this. It is not dificult to run a gasifier; however, it is a learning process that can only be taught by doing. NO book is going to teach you this, you can read all you want and that is good. But in the end you are only going to do the real learning by actually doing it. Dont spend money on books, there are forums like this one and the "Drive On Wood" forum. This is where real people with real world experience will aid you in building a successful unit for free. All you have to do is join and create your build thread. "Joe Blows First Gasifier Attempt" example.
I live and breath this, this is what I do for a living and I do it everyday and been doing so for the last 12 years. Thats a LOT of time to absorb knowledge plus we developed very advanced systems during those years. It does me no good to sell anyone a product that does not meet expectations. So Im laying it all out here. As long as you dont have expectations this is going to replace conventional fuels and understand the limitations this will be a good technology for you. If you add solar to this for off grid, this is a very practical use system. But DO NOT follow others that dont tell the full truth. These guys are just trying to make a buck and you will be disapointed when those machines dont meet your expectations.