@superjuly,
Yes - it's tagging.
Although I think you can also ask for an email update, but I'd have to figure out how, as I never do that.
A lot of people don't like tagging but it is being used more and more on the internet, and once I got over being clamfloogled, I love it.
You can tag any thread. If I were you, I'd tag it Wind Farms. That may or may not replace any tags that are already connected to the thread, but if you then look up top and go to My Tags, you'll see Wind Farm, and can click on it and find this thread.
Alternately, you can go to the top right hand little window and type in wind farm (given you remember the subject of a thread you liked), and it'll show up.. usually. The search system is still in "awaiting fixing" mode.
Or, you can look a little lower to the right and simple put a tag in the box for SEARCH TAGS.. perhaps, say, ecology, or energy resources.
Some of us are trying to tag old threads to make access easier by category.