How can we design and implement the most effective industrial energy efficiency projects?

Energy efficiency is one of the smartest avenues for industries to start contributing not just to sustainability but also to their bottom lines, as many industrial efficiency projects have payback periods as low as one year! While many industries worldwide have indeed embarked on energy efficiency projects in the recent past, there's vast scope for energy efficiency projects in more industries and more industrial processes. So this is as good a time as any to throw open the challenge: What are the best technologies, solutions and practices that can dramatically enhance energy efficiency in industries?