Hey everyone! I thought I’d take some time this month to talk about one of the main projects that I’ve been working on since we arrived here. I’ll try not to get too technical… I’m thinking about adding a section to our website where I can write about the more technical aspects of the work that we’re doing (and possibly get feedback/ideas to improve what we’re doing). In the meantime, hopefully this will give you a decent idea of the kind of work that I’m doing.
The bulk of my work since arriving in Uganda has been on the solar kiln prototype. This project came out of a need from the EMI workshop: dry lumber. When you buy lumber here, it typically comes quite wet (like the tree was just cut down). As wood dries it shrink and warps, so if you make anything from wood that isn’t fully dried, it’ll likely be ruined in a matter of months as that wood continues to dry. It’s difficult (and significantly more expensive) for our workshop to source well-dried lumber, so the solution has just been to air dry it ourselves. That essentially just means stacking the wood outside, putting a tarp over the stack when it rains, and periodically rotating the stack so that it dries evenly.
A couple of workshop workers stacking a recent delivery of lumber. Our prototype can’t keep up with the demand from the workshop.
There are two main problems with this:
1. Time: It takes 4-6+ months for the wood to dry and be useable. This has led to the workshop occasionally being delayed in completing their projects simply because they don’t have any wood that is ready to use. This means that the ministries that we are serving are delayed in getting the tables, doors, cabinets, etc. that they need.
2. Labor: Periodically rotating the wood stack takes a considerable amount of labor every few weeks. That’s pulling people away from the work that we want them to be doing and adding cost to the projects.
The speed up this whole process and minimize labor, the obvious
answer is a kiln. Most commercial lumber kilns are essentially just large ovens
that can dry wood in a matter of hours or days (you don’t want to dry wood too
fast because that can lead to cracking and other issues). In order to minimize
cost and environmental impact, we have opted to make a solar powered kiln.
The prototype kiln right after it was first built in October
Long term, the goal of the kiln is to be built into the upper section of the workshop. It will be able to hold long pieces of wood and be able to handle the entire throughput of the EMI workshop. If possible, it would great if it could even exceed what we need which would enable EMI to sell the extra wood and add a revenue stream for our workshop. In order to start tackling this project, we decided to make a smaller prototype in order to prove out the concept and work through as many bugs in the system before making major alterations to the workshop building.
Wood stack inside the kiln. The gray thing is a DIY hot-wire anemometer that we’re using to determine the air speed through the wood stack.
The prototype kiln is essentially a small wooden building with a clear roof. Solar heat goes through the clear roof and is absorbed by a solar collector (essentially just a large piece of plywood that’s painted black). The wood is stacked inside beneath the solar collector. There are 3 fans that help circulate the air throughout the kiln and get the heat from the solar collector down into the stack of wood. We also have vents on the side of the kiln that we can open or close in order to let the humid air out of the kiln as needed.
R&D Intern Jordan Dale spent a lot of his time in the kiln
Almost everything that I’ve described was completed before I was coming into work full time. Shout out to Daniel (head of the EMI R&D department) and Ivan, who was our intern during our fall term. The kiln was built in October, and we’ve been using it to dry wood ever since. With the first batch of very wet wood, we were able to cut the drying time down from 6 months to about 6 weeks. It’s already had a huge impact for our workshop and enabled them to meet several deadlines that wouldn’t have been possible without the kiln (or would have led to an increased price for the ministry that we’re working on).
So where do we go from here? That’s what I’ve been working on for the past few months (and will continue to work on). We have to main things that we are trying to achieve: optimization and automation.
I’ve spent a lot of time at the kiln debugging the various controllers and data collectors
There are 2 things that we want to optimize: speed and cost. Obviously, we want to be able to dry the lumber as quickly as possible. We have several ways that we are looking at speeding everything up. The first are the vents: by opening and closing the vents at optimal times, we can let the humidity out of the kiln while keeping as much hot air in as possible. It’s a big balancing act: if the vents are open, the moisture can escape, but it also lets out all of the heat that we’re trapping. If we can figure out the best times/conditions to open the vents, we can potentially speed up the drying process considerably.
I also spent far too much time under the kiln installing strain gauges into the frame so that we can measure the weight of the wood stack in order to determine moisture content
We are also looking at other alterations that we can make to the kiln: adding insulation to the walls, additional fans, optimized wood stacking configurations, etc. I’ve been working on a thermodynamic model that we can use to predict conditions in the kiln, which will allow us to quickly (and cheaply) test out the impact of changing different design parameters. We’re currently in the process of collecting data from the prototype kiln (we’ve installed 68 temperature sensors throughout the kiln) so that I can tune the model to meet actual data. Then we can play around with the impact of changing any of those parameter.
The other aspect that we’re looking at optimizing is the cost to run the kiln. The only real cost to the kiln are the fans. Each fan uses about 100W, which doesn’t sound like much, but when they’re running for weeks straight, that electrical cost can add up. Anything that we can do to reduce the time that the fans are on will make a noticeable impact to the cost of the running the kiln. So we’re also going to be using the model to help us determine when we can turn off the fans without impacting the drying time. We’ll then test out various control modes to actually see if it can make a difference.
I’ve also made data collectors and boxes to hold these electronics. This box was made on our 3D printer.
This is a prototype solder board for a data collector that is recording temperature and strain gauge data. Not the most beautiful bit of soldering, but it works!
The final aspect that really needs work is automation. Our desire is for the kiln to run without any extra labor or oversight. The vents will be controlled by motors that will open and close the vents as needed. The fans will be controlled by a microcontroller and be able to shut off when needed and also switch direction. And users will be notified automatically when the wood is dry so that the workshop will know when they can use the wood. It’s a big task that I’m excited to start working on.
One of the coolest aspects of this projects is being able to see the ways that God has prepared me for my work with EMI. This is essentially a big thermodynamics and aerodynamics problem. At my previous job in aerospace, I actually did quite a bit of work that involved very similar analysis. When we decided to join EMI, it seemed like this was a complete 180 for my line of work. But time and time again, I’ve seen that God was using my time in the aerospace industry to prepare me for what I’m doing now. I really feel that God has been using this project to remind me that He has us here for a reason and specifically prepared me for this role.
I’ll keep you updated as this project progresses – keep an eye out for a “Projects” tab on our website where we’ll be sharing details on projects that we’re working on!
Pray With Us
We are so grateful for your prayers and support! Please join us in prayer and praise for the following:
Hannah will be leading a project trip in June! Please be praying for her as she continues to figure out all of the logistics for this trip. She’s still working on finding a civil engineer to join the trip– if you want to find out more (and possibly apply to join the trip), here’s the link: https://emiworld.org/trips/343
Hannah’s parents are coming to visit in June! We’re super excited to have them here. They will be bringing Radar (our dog), which is also very exciting for us. Please be praying for safe travels (especially for Radar) and for all the various logistics to go smoothly. Also be praying for us over the coming month as we (especially Hannah) have a lot to do between busy work schedules and getting our house ready for guests.
We have a new set of interns that arrived last week! 3 are from the US/Canada and 2 are from Uganda. Please be praying for them as they settle into EMI and that they would have a productive, enjoyable time while they’re here.
Stay Connected
Each year, EMI’s people complete over 100 development projects which serve the poor and proclaim the Gospel of Jesus Christ. To keep these design services affordable for Christian ministries, professionals like the Arensen’s on EMI’s staff are responsible for raising their own salaries. We are so grateful for God’s provision through the generosity of donors. Would you prayerfully consider partnering with the great things God is doing through the Arensen’s ministry at EMI?