This is Part 2 of the “Running your Picarro GasScouter and eosAC Off-Grid” blog post. In Part 1 we estimated the amount of solar and battery power we will need to run our Picarro GasScouter and eosAC system. In Part 2 we’ll show you how to make an enclosure for your system and keep it safe from the elements.
We’re also going to be talking about electrical work in this post and want to remind folks that they should consult a qualified electrician when building their system. This blog post does not constitute professional electrical advice nor does Eosense take responsibility for any damage to gas analyzers or other equipment being powered.
Building the Enclosure
In the first blog post of this series we went through the calculations for the solar and battery power we need to deploy the Picarro GasScouter in the field with the eosAC automated soil flux chamber system. We can’t leave all of this expensive (and electrically charged) equipment in the field without hiding it away from the elements. The easiest thing for most people to get a hold of will be a rubber/plastic garden tool shed, which can be found at most local hardware stores. The critical consideration is to make sure it has inside dimensions of at least 51 cm depth by 115 cm width by 60 cm height (approx. 20″x45″x24″); this should allow enough space for your batteries, Picarro GasScouter and eosMX-P multiplexer to fit comfortably inside.
We bought a plastic tool shed from the local hardware store, assembled it and used a hole saw to make two holes in the side of the shed to allow the eosAC tubing and cables to pass from the shed out to their field location. Since the edges of the shed are sharp after cutting, two small sections of PVC pipe were glued (without elegance) into the holes using outdoor caulking.
This was really all that was required for us to ready the enclosure for field use. We poked around to make sure the enclosure was likely to exclude the elements adequately (no gaping holes in the seams where parts fit together) and that it would be secure enough (given our field site) with a padlock to prevent anyone from easily getting to the equipment. When making your enclosure you’ll obviously need to consider the local weather and other environmental factors of the field site, so you may need to add extra caulking, weather stripping or other similar hardware in order to make the enclosure tight enough to keep your equipment safe. Now on to wiring!
Wiring the Enclosure for Solar & Batteries
We used a ProStar-30 solar charge controller in our enclosure to ensure that the solar panels are charging the batteries properly. The two large (15 gauge wire) cables on the left will go to the solar panels, the yellow cable (also 15 gauge wire) will connect to the batteries and lastly the two grey wires with connectors are meant to go to the GasScouter and eosMX-P. Most hardware stores will sell cabling like we’re using in their electrical or lighting sections. Alternatively, a good quality outdoor extension cord will provide about the right wire gauge for this application (although its a shame to chop off the ends if you don’t have to).
When connecting the various components (batteries, solar and equipment) to the charge controller the recommended order is.
- Connect batteries
- Connect solar
- Connect load (equipment)
In order to make a good connection on the batteries, a few battery terminal clamps were bought from our local automotive store. These clamps are appropriately sized for the battery terminals, and also have a user adjustable clamp on the back where we can insert and clamp down on the wires from the charge controller. Eosense’s Electrical Engineering Manager Darren Wall points out that when using multiple batteries they ideally should be attached with a special configuration to equalize the wear (charging/discharging) on each individual battery. Shown below is an example illustration of the connection for 3 batteries.
Next we connected the solar panels to the charge controller. Since our panels were in full sun during deployment we connected both positive leads to the solar panels first, and then the two negative leads. If we had connected the solar panels one at a time we would have had one live cable after connecting the first one – making for a dangerous situation when connecting panel number two.
Finally we plugged the two custom cables into the GasScouter and eosMX-P and powered on the system! Everything looks like it’s humming along smoothly. Stay tuned for our next blog post, where we’ll talk about the the system performance and show some preliminary results from our study of carbon dioxide and methane fluxes from the constructed wetlands at the Dalhousie University Bio-Environmental Engineering Centre.