In this limited content series from Ashley Rosen, you'll explore best practices for designing enclosures for communication network equipment, and learn how airflow and temperatures inform effective enclosure design.
Today, we're sharing Ashley's interview with Techlink's Juan Swart, who shares his expertise on the challenges he's faced with different enclosures in the field.
You can also now download the best practices booklet exploring Ashley's work to design an effective conservation tech enclosure based on the lessons learned by enclosure experts.
Enclosure Expert Interview: Juan Swart
Juan Swart is the Operations Manager at Techlink. He has experience and expertise in power auditing, installation and maintenance, renewable energy, and power factor correction. He has worked with World Wildlife Fund to provide enclosures for several of their conservation initiatives.
Read on to learn more about Juan's lessons learned through his experiences with enclosures used in the field.
Could you tell me more about yourself and your work with Techlink? How long you've worked there and what type of projects you work on?
I was born in Zambia, and I've traveled quite a bit around. We were based in Dubai for 10 years, and I learned a lot there. I was a vocational education director and was a technical director for Briggs and Stratton. IThat was the headquarters for Africa, Middle East and South Asia, so I was in a position where I was able to actually travel extensively all over. And a lot of the work that I had was working with OEMs for the design and building of equipment, for example, like generators. The company would provide an engine and then I would work with the OEM in India, for example, or Germany or whatever the case may be. I gained quite a bit of experience and managed to see quite a few different countries and different applications.
"Whatever you design, you've got to design it in such a way that it's not going to take a rocket scientist to sort it out if there's a problem. "
That put me in quite a strong position to be where we are now with Techlink. We deal now in all electrical based disciplines. We've expanded to doing generators; we design generator systems so customers may have an existing system that can be upgraded, or we may have multiple units that work in synchronization together to provide whatever the application may be. So we're sort of consultants in a lot of ways, but we see that through with the technical application. We actually install the product and modify it if we need to so that the customer has a finished product. We do the planning, the consultation, the implication, the installation, the whole lot.
And in Africa, that is an issue because you can't just call in an expert to come and look at something. Qualified, skilled, technical labor technicians are very, very rare. Whatever you design, you've got to design it in such a way that it's not going to take a rocket scientist to sort it out if there's a problem.
Could we talk more about your work with enclosure fabrication?
Sure. We work with quite a few customers. We had a lot of experience with it in Dubai. We were building generators and generators, had airflow issues, and you had multiple sources of heat generation. With solar, we found that in Africa - and I suppose generally anywhere in the world, really - there's always a shortage of space within a home to actually install an inverter system: the inverter, the batteries, wires, little boxes, and all sorts of things. In the early days, some people actually wanted to install it in the lounge because it was a talking point. Now, things have changed, and nobody wants that to be seen. So you want to hide it somewhere in your home. In the home market, there is nowhere to hide this equipment other than in a utility room or a garage, so we started building cabinets that were suitable for outdoor use. The cabinets would actually bolt onto the side of the residential building. We also applied that idea to shops in a shopping center, factories, office blocks, and even agriculture.
So we would manufacture a cabinet where everything is stored in batteries and used with an inverter. When charging, the inverters generate heat, and the batteries themselves generate heat. To address the heat generation, we went through a lot of different alternatives. We found that the best solution was to use natural thermal movement. As the air heats up, it automatically displaces, and it draws cool air in. We found that that was more reliable, easier to build, and more predictable.
"It's only when there's a catastrophic failure that we become aware of it."
When we did use fans, a big problem was that the equipment would not warn you that the fan has stopped working. We tried putting in sensors so that we could monitor the temperature. Initially, we would just have an alarm go off, but there was not always someone present to hear the alarm.
There's a lot of evolving taking place. We will be using communications tech so we can monitor on a daily basis. We can log the performance of the unit-- that really is a very big deal because we can anticipate the deterioration of the batteries or any other issues. There are unpredictables that come in, which is usually your wildlife, because these cabinets are very often in remote areas. Some of our customers are six hundred miles away, and no one visits the site more than once a month. So you can't just pop in for a weekend; we have to be able to monitor. If a bird makes its nest in the ventilation shaft for the fan, the fan stops working, and the equipment overheats. If we don't have monitoring systems, then we don't know anything. Then it's a knee jerk reaction to go and try and fix the problem rather than preempting the problem.
What would you say are some of the biggest challenges in enclosure design, and what strategies have you used to address them?
On some applications, the problem was getting the equipment to the site. For a project two or three years ago, the station was on an island on a freshwater lake. The lake is not populated. It's actually pretty wild. So on any one day, you won't see anyone on the lake. The lake must be 50, 60 kilometers. It's very difficult to actually get anywhere unless you've got a boat. Once we get to the island, the water levels fluctuate enormously. To keep the equipment safe, it is set up on the top of the hill, which could be a kilometer away from the water's edge. Now you have to carry batteries with a carrier cabinet. There is not even a path-- you have to pick everything up and carry it through the bush and the wildlife and the spiders and the mud and whatever else.
One thing we learned from that was to try and modularize the cabinets so that they are very small, easy to handle, very easy to pack into the back of a pickup truck or onto a boat or even a canoe. This is critical because you don't know what you're going to have to depend on and you don't know what facilities are available. In Africa, usually there's none, so you have to do everything manually.
We don't really have like DHL or UPS in this country. Anything you want to move around, you've got to physically move it around yourself. There are some carriers that will move it for you, but they are exorbitantly expensive. It is so expensive that the transport can cost you more than the value of the goods. So this is another issue that you have in Africa. By making the cabinets smaller, we can actually transport them ourselves with our vehicles available to us or a rental. The same would go for the equipment that's going to go into the cabinets.
Material Choice and Paint:
We make the cabinets out of steel because it's widely available, strong, and cheap. Aluminum is a nice material to work with because it's light. But in Africa, it's very expensive. If you had something manufactured in the United States and then you brought it out here to Africa, that's fine. But to make it locally, aluminum is out of the question because you cannot find the aluminum in the form that is needed. The only extrusions you can get are similar to what they use for windows and sliding doors, and those extrusions are not necessarily what you're looking for when you want to make a cabinet. We don't use sliding mechanisms at all - we use the traditional swing door.
Because the cabinets are steel, they are susceptible to rust. We couldn't find anybody to premanufacture them for us. We would build a steel frame out of tubbing, one inch by two inch tubing or one inch by inch tubing. Then we would clad that with one millimeter steel plates. We found one millimeter steel sides were stiff enough to look presentable and also to offer enough security for it so that it's not that easy to get access. If someone comes with a full blown ax, they can hack their way into it quite easily. To prevent that, you would probably have to go to four or five millimeter steel plate, which will obviously increase the price, but more importantly, it'll increase the weight and the cost of the manufacture. Even then, all it's going to do is delay them. Even with five millimeter plates, someone can work their way through. So where do we draw the line on how strong we make our little safe? We settled on one millimeter steel plate for all the reasons considered.
And then we would treat that with a primer and then we would paint it, obviously. We didn't use a standard paint or an enamel or something along that line - we actually used a water based product. It's almost like a paste, and the paint we use is specifically made for the side of a building. It's ultraviolet protected, and it goes on quite thick. And it has a slightly rough texture, which actually sort of makes it blend in to the bush better and gives it a matte finish rather than a glossy, shiny finish. Because the paint is quite thick, it's resistant to abrasion. It acts (very slightly) as an insulator. So if the sun shines on it because of its thickness, it does limit the heat absorption through to the steel. And it's very long lasting; if a little bit of rust does get started in a particular spot, the rust will only travel as far as it can actually have access to the atmosphere. As soon as it gets to where this paint is, it halts. It doesn't actually run in behind it. Whereas, if we use the normal paint or an enamel or a gloss, that rust will eat in behind the paint. So we get a better life span out of it.
We use expanded metal in our cabinets and buy it pre-galvanized. The steel sheets we use are what they call cold-rolled, meaning there's no oxide level on it. In fact, it comes with a very thin layer of oil on it. It's a little bit more expensive, but it comes pretreated to prevent rust. So we just clean that off and apply our primer directly on it. The fine gauze or fine mesh we use behind the expanded metal, you get it available in a stainless steel version or a treated steel where it's very solvent, it's very reflective in color --where it doesn't rust. We try and use those wherever we can, but it's not that available. So we have to resort to a normal steel one that has got a coating on it. It's like a paint coating. And they do last maybe five or six years, seven years - but then things do have to be relooked at. Even that gauze, if you get the more expensive one, then you're going to have a lifetime product.
On the doors, we used to use hinges that you could buy off the shelf in Africa for two swing doors. If you needed to work on it, you could actually open up the full length and breadth of the cabinet, so it's easy access in and out. You don't want to try and get into too narrow a doorway.
We found that if you buy hinges off the shelf, premade hinges, they were not very robust, and they did rust, and they failed. They weren't that strong. Like a door hinge, for example, it may seem strong in the house on your door, but in the open they don't work that well. So we got what they call bullet hinges, which is basically a two part hinge two seams with a pillar in between them. One sleeve is welded to the cabinet. Another sleeve is inverted, and it's welded to the door. The top is closed off, so you don't have water ingress in there to promote rust. Before we assemble the hinge on the door, we actually pull it apart, and we put some grease in there. We then put the hinge together, and tack and weld it on, so that grease is permanently inside there. They're physically quite strong. On a smaller cabinet, we put two hinges, but on a bigger cabinet we will actually put three hinges just to increase the security. We try to make the doors so that, when they're closed, they're recessed slightly into the cabinet so it's not easy to get in a crowbar or something.
The other problem that you've got is security when you have solar panels and batteries. We need to build a cabinet that is thief-proof. But to make it completely safe, the cost would be exorbitant. For example, your steel cabinet would have to be made out of one inch thick steel plate. If you have a cabinet made out of that material and that's 1 meter wide and 1.5 meters tall, the cabinet's going to weigh 600 lbs and be way too heavy to move. There's a trade off in the security where you have a deterrent rather than something that is 100% foolproof. If you have a determined thief, and he comes with an angle grinder or a cutting disk, he can cut into anything, even a 1 inch thick steel plate. He has that ability because he's got time on his hands. If you've got a cabinet, and it's in the bush, and there's nobody there for literally miles around, and nobody's coming for another month to check up on the equipment, the thief has enough time to do whatever he wants. When you add batteries to the steel cabinet, it becomes too heavy for one or two people to move. So we make it heavy enough for them not to be able to move it easily, but not too heavy that it prevents us from moving the cabinet into position through bush, animals, water, mud, whatever else is going to come across our way. And then obviously, the size of the cabinet is now also reduced to size, but not too small.
We found that spoke locks that were flush mounted didn't really work in practice because the keys would get lost. What we do now is, instead of having a recessed lock, we just put on a normal padlock. That way, we can break the lock if we have to. And if someone is going to come there, and they are able to break the padlock, you're not going to stop them anyway. This is an example of the tradeoffs in security.
Smart Design for Airflow and Waterproofing:
We take into account the prevailing winds. We will make a ventilation slot along the top of the cabinet, on the one side facing the wind only, and then we'll try and position that downwind of the prevailing wind. We lift the base of the cabinet off the ground at least 150 millimeters or about six inches so that it can actually draw in air underneath. As the equipment heats up, it'll expel out the top and draw fresh air in at the bottom.
You have to try and anticipate rainfall. Often, when you do have a storm, the rain will come in sideways. You don't want to have too many open apertures where water can come in. It's another reason why we only have the ventilation on the one side of the cabinet and the bottom.
We did think of putting in what we would call a Durata box in the marine environment. Basically you would have a baffle so the driving rain would hit the baffle and run down rather than through the cabinet. But the baffle offered too much of a hindrance to ventilation. As a trade off, we used a fine mesh on the ventilation. We used an expanded metal, which is like a diamond shaped wire mesh. It's quite strong and acted as the physical barrier to stop anybody from putting their hand through the openings for the ventilation. Then on the inside of that, we would put a steel mesh called mosquito gauze that's small enough to prevent virtually all insects except some ants from getting through. The expanded metal and the fine mesh also catch any rain droplets and break it up into a mist that will run down the side of the cabinet. Some may get inside the cabinet and run down, but because the cabinet is open at the bottom as well, any water will just drain out at the bottom of the cabinet. There might be some fine mist spray that gets onto the equipment, but generally that's not enough to form droplets that actually run down the equipment.
The coldest temperature we'll go down to will be about zero in winter, for maybe three to five hours at night and maybe five or six nights in the year. Down in the grass, we find that freezing is not a problem. Maximum temperature can go up to 48, which is quite high.
Some of the equipment likes to run hot, so you really need to have a good ventilation system for that. In the cabinets, we position the batteries at the bottom because of the weight; hopefully that makes it less likely to topple over. We do use concrete to cement our solar panels and our cabinets so they are very rigid and are not going to move easily. The equipment we tend to position at midpoint in the height of the cabinet. We like to leave a bit of a space above the equipment so that there is a thermal flow. If the equipment is too close to the roof of the cabinet, then the heat hasn't got anywhere to move easily. Especially if there's no wind - if there's no air movement whatsoever. In winter, there is usually a breeze during the day, which is nice, but not in summer. So we need to have that little bit of a gap.
The other problem that you have is growth. Wherever these cabinets are positioned, within a year or two, there is a lot of grass. The grass can grow six foot tall in places. Most species of grass will be four or five foot high, which is almost my shoulder height. Yeah. So it can quickly offer a restriction to airflow. Then you have vines that grow and other small plants that will grow up. So you need to try and get up above that as much as possible within reason. We try to make a schedule with the guys who do come and do an inspection so that we can keep it clear around the cabinet. If they can keep it clear, it tends to keep away the insects and the small animals as well. If it's an open area, they're less likely to move right across the area because they're exposed and vulnerable to predators.
One of the problems that we encountered was that the cabinet would overheat when the sun was coming in at about a 45 degree angle. It would catch the side of the cabinet and then create quite a high temperature inside. The natural cooling system would work, but we found that it would unnecessarily load it. You don't want to unnecessarily heat your cabinet. One of the ways to get around that was erecting our solar panels and lifting them high enough so the cabinet could fit underneath, offering a sufficient shade so that we didn't have that excessive heat buildup. Working with the solar panels made a big difference, to the point where we actually haven't had any failures or issues at all.
What we do in the cabinet is place a board where all the equipment would be mounted, and the board would be away from the wall. What we eventually ended up doing is taking the board out altogether and replacing it with the expanded metal. Air can travel through it, and it makes it very easy for the installation of the components because there are thousands of little holes. You just have to have a handful of nuts and bolts and then you can mount anything on it. That really made a big difference when we went down that route. The plus was that it allowed airflow laterally as well, not just vertically.
Strategy for Preventing Sinking:
On some of our installations, we've actually put what we call a lip channel, which is like a U-shaped length of channel that's sort of rounded up, and it's got a flat lip. And then we will extend that longer than the cabinet and place that on the ground. Two off the cabinet legs will be on one piece of channel and the two other legs will be on another. This is needed when the cabinet is directly on bare ground so that none of the legs sink if the ground becomes soft after lots of rain. Where we can, we prefer to actually extend the legs to be quite long and cement them in. We have a t-piece at the base of the leg of about two or three inches. Then we actually encompass that in cement. It adds weight to the cabinet and holds it down, but it also prevents the cabinet from moving.
"Keep it simple and basic rather than fancy."
We also place an Earth rod. We Earth all the cabinets, along with our solar cabinet, our solar panels, and the frame. Obviously we follow all of the electrical procedures for solar panels and the wiring code, even though it's in the bush, and there's no inspector going to come anywhere near it. We still follow that code because there's a reason they have that. So we put in a spike, and then we go one beyond that and actually excavate a hole. We try and dig the hole at least two meters deep, even three meters, if we can. If the soil and the geology underneath allows us, we dig as deep as we can. And then we have a very long, very thick piece of copper cable that we will throw in. That cable will come out and be on the Earth of the equipment. And then we'll bury it again.
Are there any other words of advice you have for those looking to make their own enclosures?
People tend to add unnecessary features, like displays. Try and stay away from that. It's counterintuitive, I know. But you've got to hold back because where it's going is a really harsh environment. Any feature that you put in there has to be robust; otherwise, that feature will fail. So you've got to really think about that.
Thanks to Juan Swart for sharing his expertise with us.
To learn more about this topic, download the best practices booklet exploring Ashley's work to design an effective conservation tech enclosure based on the lessons learned by enclosure experts.
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