Wow! Great series of images.
All three are very different from one another, not only in color, but also in composition. Your first image uses shapes and lines to create it’s visual message. Your second image focuses more on communicating power through the use of vertical and diagonal lines. Your last image uses negative space and a limited color palette to tell its story.
It’s incredible that you haven’t touched any of these images in PhotoShop. The saturation levels in your last image are incredibly dramatic. The vibrant greens and oranges jump right out of the composition.
Your first image uses gradients of white, green, red and blue for its composition and the lines in the photograph really engage your audience. The image is almost maze like because of your perspective and the shapes created. I really appreciate that you turned your camera upwards. Changing is one of the easiest ways to experiment with composition and also one of the most underused techniques.
Your second image is the most monochromatic but no less interesting than the rest. What I love about this image is how you’ve used the pipes coming out the lower right corner as a sort of “leading line” drawing your audience’s eyes into the photograph. You can use anything as a leading line and it’s nice to see your experimenting with this.
Roads are also very common leading lines:
http://static.desktopnexus.com/wallpapers/29180-bigthumbnail.jpg
But you’re right about the ventilation. It’s a little distracting.
Your last image is beautiful. Although you’ve broken the rule of the rule of thirds by placing your object dead center, it works because the foliage creates an uneven sense of balance which ensures your image doesn’t come across as boring. It’s very engaging and dramatic.
Overall, great work!