A solar powered fan for your attic is a good choice if switching completely to solar power is not feasible. The fan will have a temperature sensitive gauge and switch itself on when necessary. This will remove heat and lower the cost of cooling. It's also solar powered, so you don't have to pay to power it.
Fresnel Lenses are amazing solar heating and cooking tools but there are some very common misconceptions. http://greenpowerscience.com.