Ashley, I worked for the National Renewable Energy Labratory in Golden, CO, USA several years ago. They were doing lots of work with linked open data and energy -- you might find some good information there (http://www.nrel.gov/)
As for time series data, I think that there was a group at the Digital Enterprise Research Institute that was using data cube schema to do time series, but I could be misremembering that. Finally, as to changing the object of a triple that is possible if you use an rdf:Seq (Seq.set() ) or rdf:RDFList (RDFList.replace()). However, that may throw a wrench into your schema plans. The most common way is to simply delete and insert (or insert and delete). I can't think of a reason not to put the data into Jena.
