It's twenty minutes in the future, and farmers across the 'big countries' (USA, Australia, etc) are facing a new scourge: light poachers. Every summer hordes of self-driving trucks crash into fields and deploy vast photovoltaic cloths over the nice flat, clear ground, covering up to several acres of cropland each. The cloths capture the solar radiation to the detriment of the crops growing underneath, and the power (up to several megawatts on a 'good day') is collected by the trucks, and... what?
What can my poachers profitably do with up to ten megawatts of free electricity within a volume the size of a shipping container, to either store the electricity to be utilised later, or manufacture something that can be subsequently sold? The factory will have no external connections of any sort other than power in and air in/out, so any raw materials will have to form part of the payload (it would be reasonable for them to need to be un/re-loaded up to once a day).
I'll handwave the economic implausibility of the capital cost of these automated factories, or the fact that there are plenty of 'legal' places where such a thing could be set up without trespass. I'd like to avoid the obvious answer of "mine bitcoins", or other virtual commodities, and have the factories produce a physical, tangible product.