Firstly, I’d check out the Big Tricky Questions doc, as we cover this answer to a degree there.
In terms of the cost of your solution specifically, we can’t suggest a budget, as this should be part of your considerations based on what you feel is appropriate to meet the design brief.
As a suggestion I will make is to consider the flexibility that this mobile power supply could bring; not all homelands or ranger stations are occupied continuously, with where people reside changing through the course of the year. Let’s assume that the alternative to your mobile system is 2 or 3 other systems that are static and don’t produce any benefit when those sites aren’t occupied. This means you’ve got an installed asset, with all of its upfront costs, but your only yielding the ROI when you’re occupying the site. What is the cost of those two systems? For the same or less amount of investment, could a mobile array effectively service two locations?
Some things for you to consider 🙂
Also, we’ve answered a similar queries to this elsewhere in the mobile power supply question threads, so I’d look through there also.
Hope this helps,