Now is not the time to be asking if it is a lucrative field for your degree. If you go on to get a masters, that is another matter.
Most profitable alternative energy companies have as their founders the engineers they rely upon, so you may just end up firing the resumes to the standard multinational firms. I do not mean to sound negative about this, but this is something you really should have planned out when you were a freshman.
This is not to say you do not have useful background- If you did well with thermo-dynamics, you could try connecting with Modine, or you could even try develop your own inexpensive raw material, be it thermal exchange tubing, unit heat exchangers, etc. If you had a background in Aerodynamics, Vestas, or any of dozens of companies around the globe might be worth looking at. It helps if you can speak a foreign language. If you can speak Mandarin, you might find a sales job or troubleshooter here or abroad for a Chinese interest.
As broad a field as the entire of what qualifies as "alternative energy"- it is very competitive and cut throuat- but it is that way due to the rather specific nature of the items in and of themselves that comprise the vast field and the sheer bulk of "almost fits" applying . At the same time, if you had minored in electrical engineering, or soils engineering, or materials, you might need to follow that aspect as well. Your willingness to travel will also have a good deal of bearing on how lucrative a prospective employee you might be.
You might consider, if you did get an EE minor, go to http://www.digikey.com, take a look at the companies that are on their line card, Even though they are electronics in nature, there are mechanical design aspects in most all of those items within their catalog as well.
And don't be afraid to take a risk on your own initive and ability- if you have an idea in mind; pursue it.