Water Subsystem

19 Mar

FIRST_Robotics_Competition_(logo)Last week I went to a STEM Expo put on by First State Robotics in Wilmington, DE.  STEM is a national campaign for I believe Science, Technology, Engineering, and Mathematics and trying to get those subjects better coverage in the school system.  First State Robotics is the nonprofit organization started around spreading the word of US FIRST robotics programs throughout the State of Delaware.  I used to be a coach/engineering mentor for a local FRC team (Go MOE!), who founded First State Robotics.  FIRST is a great organization by the way for getting school age kids interested in and excited about careers in Science and engineering.  I wish it existed when I was in High School, and I can’t wait until my kids are old enough to begin participating in the program.  OK, so what does any of this have to do with the water subsystem in ROAM?  Excellent question, I’m still getting to that.  The STEM Expo included a showing of a documentary called Slingshot, which is about visionary inventor, Dean Kamen, the founder of FIRST and inventor of the Segway, and his new invention called the Slingshot which is a water purification system.

segwayKamen only tries to tackle the hard problems.  And one of the biggest problems facing the world this century is the global water crisis.  They mention that 50% of all disease world wide can be attributed to a lack of fresh drinking water.  People in developing worlds spend the majority of their time in a day, finding and bringing drinking water home to their families every day.  And often even that water is still full of all sorts of pollutants, viruses, bacteria, etc and continues to be the number one cause of death and illness in the developing world.  His company Deka has designed and built small scale water purification through distillation systems that are capable of removing anything from a water source and ending with 100% medical grade pure water on the outlet.  Their small scale system is designed to run through over 100 gallons per day with very little energy cost, and require little to no maintenance.  They’re partnering with the CocaCola company to help distribute and install these systems in villages and towns throughout the developing world to try to eliminate this impending global water crisis.  It’s a very admirable goal, and made for a great documentary (speaking as someone who was already a big fanboy of Dean Kamen)

 Now imagine this device which they are trying to mass produce as cheaply as possible for use in purifying water using little to no energy, and the size of a small dorm size minifridge.  That would be a perfect centerpiece to the water subsystem on ROAM.  Purification through Distillation basically means they take the incoming waterstream and boil it off.  Then immediately capture the resultant steam at 100C and recondense that stream into pure medical grade water.  dean-kamen_7071They play games with energy efficiency by using the incoming water stream as a heat exchanger to cool the distilled water, and also steal some heat from the distlled stream to preheat the incoming material.  But at the end of the day, that’s what you have, is just a simple distillery.  What it means though is you can have any type of water supply imaginable on the incoming stream, and the outgoing stream will still be 100% pure.

Since any water stream will do, this means you could 100% recycle all grey water on board and distill it.  The water system then could be an incoming holding tank with a strainer to catch debris and the like with a fill either from a hose outlet, or a portable pump which could be used to collect water from any source, like a stream, puddle, or well.  Here’s an example of a system that Expo user jrhetts built for his FUSO based rig.  This holding tank is then called the “dirty” water tank.  The dirty water tank is also collecting waste water from the nominal grey water systems in the rig.  This would include the shower drain, sink drains from washing hands and washing dishes, clothes washer outlet, and dishwasher outlet.  Those streams would go through the same strainer to collect food bits or other large solids from collecting into dirty tank.  But otherwise, simply fill up the dirty tanks.  A third stream into this dirty tank is roof rain water collection.  This idea is stolen from Bliss Mobil. They keep their roof recessed which can act as a catch basin for rain water which is then collected back to their grey water tank and then recycled with their water filter system.  This same concept applies draining roof water into the dirty water tank with some strainer system again for catching leaves and other debris from getting into the tank.  When their is sufficient water in the dirty tank, and a sufficiently low level in the clean tank, then the onboard Slingshot purifier can run and convert and distill the dirty water to clean water in the clean water holding tank. All of the water systems on board then are plumbed with this clean purified water.

rv-thermo-top-c-200Now to get hot water from the system, I am anticipating using some type of Diesel fired boiler unit, similar to a a Webasto Isotemp unit with a diesel hydronic Thermotop unit. (pictured)  The Thermotop will serve multiple purposes. #1) Use the truck’s main diesel fuel tank to preheat the engine coolant loop.  This is beneficial on really cold mornings or high altitudes when the truck doesn’t really want to turn over as it’s simply too cold.  With this unit preheating the coolant line, the block warms up and allows the engine to come alive easier and more responsive.  Also allowing the cabin heaters to deliver heat faster to the cabin of the truck through warmer quicker engine coolant.  #2) The thermotop can heat the engine’s coolant lines when the truck’s not running.  The main reason to do this would be to generate hot water without the main engine on by circulating that heated engine coolant through the coils of the Webasto Isotemp boiler/calorifer.  Which leads to the Isotemp.  It’s main reason for being is an insulated tank which can apply heat to the contents of that tank.  It can do this in multiple ways, the first is an electric immersion heater, which would only really be used hooked up to shore power or if the diesel wasn’t working properly.  The second means is from an internal coil of tubing in the tank which is plumbed through the truck’s main coolant line.  This means that if the truck is running as we’re driving to a destination, hot coolant from the engine can be routed through the unit to heat up the tank.  And then even better, as just mentioned, if the engine isn’t running, the Thermotop unit can still be employed to heat the coolant line and thereby the water in the 20 gallon tank of the Webasto Isotemp Basic 75 Double Coil.  In addition, with a ready supply of hot water, then options can be explored for hydronic cabin heaters through finned radiators throughout the rig, or even in floor tubing for radiant floor heat.  Other uses for the hot water would be the shower, kitchen sink, bathroom sink, clothes washer, and dishwasher appliances.

sr-operationThe final part of the water subsystem then would be what to do with the toilet.  As I mentioned in the utilities overview post, I really like the idea of the ecojohn incinerating toilets.  It seems like a good idea to inceinerate the waste so that you don’t have to worry about emptying it.  However, in practice their main unit seems more survival grade than something I would want in my house.  The whole auger system to transfer your waste to the burn chamber just seems to scream utilitarian and with no water I can’t iimagine how that would not stink and be a disaster to clean and god forbid something breaks.  Now that being said, now check out their sewage incinerator series.  With this sytem, you can use any head unit you want in the actual bathroom.  So imagine a nice porcelain low flow vacuflush marine toilet with a built in macerator (like a Dometic Sealand Masterflush) which would look and feel like a residential unit while having the macerating feature to pulverize the waste stream, and low flow for not requiring much volume to deal with.  This toilet then would flow into the WC5-Mini Incinerating tank. waste-combustion-sewage When the tank gets to a certain fill level, the system begins a diesel fired* incineration cycle and completely burns off all waste from the tank and you’re left with periodic maintenance of shoveling out clean ash after several cycles.  This could then replace the tradional RV black water tanks and also replace the typical RV dump station trips required for a standard RV.  We’re recycling the grey water, and burning the black water!

* -Currently the WC5 is available as diesel fired, but it is much larger than the Mini.  But the mini is only listed as propane powered on their website.  As reasons mentioned in previous posts, I think it is very valuable to go with all diesel or electric powered appliances, and no Propane.  Last year the Mini wasn’t even listed on their website, so I have hopes that I can convince them should the need arise to make a diesel mini.  🙂

I think the step of eliminating the traditional RV dump station is a requirement for convenience of international travel.  As soon as you leave US, Canada, and Western Europe there is no longer an infrastructure to support regular waste water dumping.  As a result, many manufacturers use THetford Cassette style toilets.  These give the advantage of alse eliminating the black water tank, but you still need to (frequently) carry or wheel the cassette to a traditional toilet somewhere.  Which sounds like a pretty nasty job I would like to try to avoid and I would be willing to pay a price and space premium for making it closer to a more traditional residential “Flush and Forget” style system.  I think the closer I get to a residential style comparison the more like my 4 travelling companions are going to be willing to come with me!  🙂

Next up – Electrical subsystem.