is it true that you have 8000 visitors a month? which one of your site has 8000 visitors a month i've checked your nevadarenewableenergy sites and i can't analyze your traffic since on alexa it display me no data ranking for your sites. and that sites has only 1 page... wow, have to say that it is hard to earn with adsense if you only have 1 page. try to update your content daily with original content.
8000 visits a month and no income? What is your source of traffic? Would it be possible for us to take a look at your site and maybe offer some guidence to enable you to capitalize on your traffic more then you are doing so right now? I do not know if you have heard of them but we have used http://www.conductor.com/linking-solution/publishers/monetizing-unused-inventory on a few client sites and they have resulted in a good stable income stream. you can run it along side adsense or other ads.
Its very hard to say you need x traffic for x revenue as payout for keywords is very different. But If you are getting 100 visits a day you should be making some money, if you aren't then you should take a look at your site and try to improve your ad clicks, perhaps you should consider other ways of generating income from the site.