Solar Power isn't Feasible!

Solar Power isn't Feasible!
This cartoon was on the cover of the book "SolarGas" by David Hoye. It echoes the Sharp Solar slogan "Last time I checked nobody owned the sun!"

Thursday, August 1, 2013

Designing with the other 90%: New tools for meeting our millenium goals through biogas!

  I have just returned  from a very productive and enjoyable time in Shenzhen China (about an hour inland from Hong Kong)  with the Puxin Technology company.   The most wonderful result for our Solar CITIES Solutions biogas initiative  is that they actually  designed a new biogas system specifically to help us meet our needs in Rio de Janeiro and other locations around the world where we face uncertain terrain conditions and have to dig and prepare with shovels and hand tools.  Talk about "Design with and for the other 90%"!

This felicitous offer on the part of Puxin inventor and CEO Dr. Jianan Wang, lead engineer Mr. Jong and CAD designer Jeremy Wong came when we found that the standard 10m3 system molds we ordered and were about to ship for our builds this year with Architecture for Humanity at the school in Niteroi and with Catalytic Communities in the favelas of Rio  would be very very difficult to use if we wanted to  create smaller (shorter stature) systems (6 and 4 cubic meters) in the field where ground conditions don't permit installation of a full size 10m3 digester. 

Culhane simulates building conditions in Rio and discusses possible difficulties with Puxin founder and inventor Dr. Jianan Wang

It is recognized that in some situations one set of 10m3 molds can also be used to build a 6 cubic meter system if you simply don't use the bottom ring of plates.  But when I was doing the training I  discovered that what is true on paper and a few field trials  is not always what you get when you are in the real world and out of the lab or factory or idealized setting, and I wanted to be sure I wouldn't arrive in Rio only to find that "for want of a nail the shoe was lost".  It turned out that getting a single ring of plates to form the perfect circle necessary to complete the dome for a 6 cubic meter system  is almost impossible if you don't have a way to draw a perfect circle on level ground and don't have  a team of people surrounding the molds  able to kick them into shape from outside to form the circle with proper tolerances. 

I had been assured  that making a 6 cubic meter digester with the top half of the 10m3 system was possible but I said, "I trust you on that, but I'm the guy who has to make all this work in locations where the proper tools and support are lacking, and we learned a lot from our experiences in the Phillipines and Israel about what can go wrong.  So if you don't mind,  let me pretend this week here in China that I am actually in Rio at the school site, in a 1.5 meter deep mud pit on uneven ground where it is impossible to draw a good circle, with a tiny team of workers and no ability to intervene from the outside".  I had learned in graduate school in Urban Planning the famous adage "The map is not the territory" and that ground truth varies wildly from even the most tolerant schematics and the best laid plans of mice and men.

Solar CITIES' Culhane explains the problems they will have with the current system in Rio if they try to use the existing plates to make a shorter 6m3 system.

 When we ran this kind of a training  simulation on the warehouse floor without using the perfect circle they had inscribed there, and disallowing anybody to help from outside the mold assembly,  we found it absolutely impossible to get the molds together in the end.  We would pull and shove and bang and twist and lift and wiggle, but tiny differences in curvature without the reinforcement of a bottom ring of molds, overlapping so the curvature of one ring reinforced the gap of the other ring, added up to a situation where the last of the mold plates simply would not fit. Where the dome plates connected to the top ring we had a gap of almost 8 cm.

Chief Puxin Engineer Mr. Jong calculates what will be needed to redesign the system so the same molds can be used for three different sized biodigesters.

The gap that results when a single ring is used with no way to enforce good curvature.

For the six cubic meter system, if an outer mold is used, one needs both outer molds as the lower one alone is too short.

 The inventor and his chief engineer came over to discuss this with me and we determined that in fact nobody had ever built the 6 cubic meter system under the difficult conditions I would be facing in Brazil.  Normally a site will be prepared with a tractor and backloader and leveled and one can inscribe the circle on the floor and there is plenty of room for builders to surround the molds from the outside and kick it into form.  But in our case in Brazil we have very little space to work in, can't use the outer molds at all and there is certainly no room for people to stand outside the diameter of the tank molds. Also we have to dig by hand with shovels in rocky terrain where we can only go down at most 1.5 meters and since the digesters need to be completely buried so that a small playground can be built above the digesters we need the flexibility of deciding in the field, once we have dug as deep as we can, whether we can build a 6m3 system or need to go even smaller to 4 cubic meters. And that option isn't available from the standard Puxin family molds to begin with.

The site we are building on in Niteroi, Brazil: The green area to the left is the only space we have to build three digesters, one to treat the kitchen wastes from the building on the far left top and two to treat the sewage from the bathrooms in the building on the bottom right. Since we can only dig down at most 1.5 meters and must cover the digesters with dirt and grass to create a playground area, being able to have flexible height possibilities is critical.

A top view schematic of the site in Niteroi Brazil gives a good idea of the contraints.

Photograph of the Architecture for Humanity site in Niteroi where we will build the 4 or 6 cubic meter Puxins.  The exact location is shown in the picture on the right, to the left of the existing building which is where the molds will be stored until the systems are built. Subsequently that building will be taken down and the school building constructed in its place.

 I explained that the costs and difficulties of importing molds (especially with exorbitant shipping fees and import fees and possible demurrage) meant we could only make one order, and that most non-profit organizations would be in our situation and could not order more than one set of molds. The fact that we never know how deep we can dig in so many locations  meant we would have to determine at each site if we had the space for a 4, 6 or 10 cubic meter digester.   Puxin does sell a dedicated 4 cubic meter mold set but it is too small for most of our builds so even though we might need it for one of the locations in which we are working  for our Brazil project, it wouldn't be the right allocation of our limited funds. Puxin advertises that the 10 can be reconfigured to make a 6 but they said, "we caution against it in your situation  because  we haven't had the experiences you are describing up until now as we've only had a couple of clients who decided to build the 6 cubic meter variant. We wouldn't recommend deviating from the normal 10m3 configuration under the kinds of circumstances you will encounter in the field , for the reasons you discovered in your simulation training... without a conforming ring made of two opposing mold plates, it is very difficult to get the tolerances right " 

In light of this we sat down and discussed all the environments Solar CITIES Solutions works in, the difficulties we encounter in the field; the lack of machinery or electricity in many of our project areas  and how we most often  have to improvise and do things with hand tools.

 I mentioned that Insinkerator engineers had helped us respond to these challenges by creating a bicycle powered food grinder for the places without electricity and then asked, "what could we come up with so that we could order a single set of molds to be shipped to a remote location that could be used to accommodate any kind of terrain and size constraints."

Puxin's visionary  inventor, Dr. Jianan Wang, said, "we are happy to redesign our system so it can be used by people like you. We want to make our systems the best in the world for developing countries and for helping the poor.  Most of our business is actually the 100, 200 and 300 cubic meter industrial or institutional systems while the 10 m3 and smaller are something I invented to help the world, not for business. Anyway, my philosophy for inventing the Puxin system was that we make biogas as inexpensive and easy as possible, something everybody can do.  We want to stop the problems associated with wastes and pollution. I've always felt that if we can get to a time when everybody is turning wastes into biogas and fertilizer because it is so easy and the market becomes saturated and there is no more business for companies like ours, then we would consider that a success.  We would simply go into another business. This is not about the money, this is a social good, something we are obliged to do to make people's lives better, like the invention of penicillin.  So I want to learn from the experiences of non-governmental  organizations like yours and figure out what the field challenges are so we can make it as easy as possible for the poor to get biogas" 

With that said  Dr. Wang  set to work with his designers and engineers as we walked around the 6m3 mold we were having trouble assembling, discussing the pros and cons of different solutions.  I lay on my back with a hammer simulating what it would be like to be inside the digester at 4m3 and 6m3 as it was being built underground in Brazil and  based on the length of my arms and how easy it or hard it would be to get the screws and bolts and hooks and plates in place, they took measurements.   The most important thing was to have a conforming ring to force the circle into shape. I suggested that that ring be made of a section of the top portion that already had the angle for afixing the existing top dome plates and they liked that.

We finally  hit upon a solution where a single shallow ring at the top of about 10 cm height keeps the circular form and allows the bottom rings to be used individually or stacked, giving us the possibility to reliably build three different sized systems out of one set of molds in the toughest field conditions!

This was one of the great things about being in China, a country where rapid retooling and creative manufacturing are part of everyday life.   They said that getting the factory to retool to produce this special Solar CITIES Solutions ready system would only add another week or two to the order, but since we were looking at an early to mid September delivery anyway because of shipping logistics (ships leave Shenzhen for Brazil only once a week, on Tuesdays, and we'd missed one of those boats already; it takes 25 days from China to the port of Santos, and there all 20 foot containers like those the Puxin comes in must await consolidation into 40 foot containers before making the additional 5 day journey into Rio)  and we don't want anything to go wrong since we have one shot at this, the President of Puxin thus determined that  reinventing his product for the type of application environment we are facing  was the only to way to go. He said he  wants to make sure that Puxin's reputation as provider of the best, easiest to use and least expensive biogas systems in the world benefits from  the focus we and other non profit organizations are making toward helping communities in extreme situations and in turn benefits the world.

CAD Designer Jeremy Wong and Chief Engineer Mr. Jong model the new Puxin design for Solar CITIES.

A very satisfactory result indeed!  I've attached the CAD 3D drawings they just sent.  This, in combination with the bicycle powered food grinder Insinkerator corporation created for our mission , will make for a very nice story of companies supporting our millennium goals with targeted innovation -- a true design for and with the "other 90%"!


 In the new Puxin design, instead of having two vertical plates to work with, we now have three. Whereas in the old design the bottom of the two plates was 50 cm tall with a flat top to allow the 77 cm tall top  plate to stand on top of it, with the top plate having an angled surface for adhering the 80 cm long, 29 cm high dome plates, now both the bottom plate, which is slightly smaller than 50 cm, and the top plate, which is smaller than 77 cm, now have flat surfaces on top.  The bottom and top plates have the flat top surface so that a new ring of approximately 10 cm can be adhered to either the bottom or top plates. This new ring has the angled surface for attaching to the usual 80 cm long, 29 cm high dome plates.

Now, thanks to the Puxin inventor and engineers truly designing with and for us, the other 90%,  Puxin users can now  use the same set of molds to create 4 cubic meter, 6 cubic meter and 10 cubic meter systems! 

 Above we see two of the 16 triangle pieces that form the top dome. 15 of them are  80 cm long with apex of the triangle being 25 cm and the wide base part 53 cm.  The 16th is cut into two pieces (shown on left) with a section about 10 cm being the last section to go in.  Unless the molds underneath are almost perfectly circular this thin final piece simply won't go in. This is why one needs two sets of plates, stacked like bricks overlapping, to hold the curvature.
Above the triangular pieces we see the 4 neck rings -- the bottom neck ring which binds the triangular pieces on the left and the 4 wider neck rings for the top of the neck. These, and the neck pieces are identical to what we had in the previous design.

 Above we see the new bottom plates for constructing the 4m3 digester. The top conforming ring has ot yet been put on.

 Here above we see the new "middle plates" used for constructing the 6m3 digester. Again, the top conforming ring has not been put on.

 Here we see all the plates assembled to make the normal 10m3 digester. You can see the bottom plates used for the 4m3 on the bottom and the middle plates, used for the 6m3 digester placed on top but rotated so that the gaps of one ring are covered by the curvature of the other, similar to the way bricks are laid.  On top we see the new top ring with its angle lip.  It is also placed so that its gaps cover non gap surfaces, imbricating for curvature reinforcement.

The above picture shows the new 4m3 digester possibility, witht he bottom plates covered by the top conforming ring, the dome plates attached and the neck ring assembled.

The above picture is a partial assembly of the 6m3 configuration.  Without the new top ring one gets to a point where the very last dome piece simply won't fit because of losses in curvature.

 Above we see the 6m3 system with neck ring ready for the neck to be placed upon it.  Note the "gap plates" and how they are in different locations.  The major difference between the new design build and the old design build is that we no longer imbricate the dome plates with the top ring -- in this case, because the curvature is held by the two rings of the vertical plates, we can assemble each dome plate with its associated top ring plate. This, Dr. Wang explained, makes it easier to preassemble sections of the top dome outside of the working pit and should simplify a build when it is hard to get inside the tank comfortably, as with the very shallow 4m3 builds.

 The above picture shows the 6m3 mold with neck rings.

 The above picture shows the full 10m3 molds assembled. with bottom neck ring.
 The above model shows the full 10 cubic meter mold assembled with both neck rings (but without the neck which is not shown but which is the same as the original Puxin model. Note that the original neck molds, which are used to make the hydraulic pressure gas holder system,  can be used with almost any sized Puxin -- not just 4, 6 or 10 m3 but even 100, 200 or 300 m3 systems.  This unique design allows one cubic meter of gas to accumulate and pressurizes it under 1 ton of water pressure (the weight of the 1000 liters of water displaced when the fiberglass gas holder is full of biogas) which then can send it to the storage balloon or other gas holders. An elegant and simple design indeed!

We at Solar CITIES Solutions are excited to be the first to field test this new improved Puxin system that was created specifically for organizations like ours, and look forward to sharing the results with the world community.

If you want to be part of that community, come and join us in our facebook group: Solar CITIES Biogas Innoventors and Practitioners

We look forward to continuing the journey and are deeply grateful to Puxin for designing for and with the other 90% and to Insinkerator for sponsoring the training trip to China and the builds we are doing in Brazil.  Xie Xie, Muito Obrigado!

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