We will never be able to move through space at faster than the speed of light. It doesn't matter how much energy is used or how long you accelerate something for it will never go faster than the speed of light.
Lets say you get on a space ship and start acceleration at 1g for 1 year. You then stop accelerating, the speed of your space ship relative to your ship is still 0, and light moving away from your ship is still moving at the speed of light. Your speed with respect to your starting point is some fraction of the speed of light. You could repeat this as many times you like you will never be moving faster than the speed of light in any frame of reference.
Lets say I am on earth and I see a space ship moving away from me in one direction at .6c, and I see another space ship moving away from me in the opposite direction at .6c also. You think to yourself they are moving at 1.2c with respect to each other, but you would be incorrect. to get the correct speed relative to each other you would use
http://en.wikipedia.org/wiki/Velocity-addition_formula So you would get 1.2/(1+.6*.6) = .88c
If we are able to accelerate to close to the speed of light relative to earth we will be able to explore the galaxy and universe. On the earth a huge amount of time may pass but on the space ship it may only be a year or two.
Or if we are able to manipulate space it's self we may be able to get around going through space faster than light.