One of the most fascinating things I’ve learned about recently is the engineering behind the US Strategic Petroleum Reserve. Here are the key requirements it’s designed to meet: Store hundreds of millions of barrels of crude oil for long periods of time to respond to disruptions in petroleum supplies . Keep the oil secure against attacks by our adversaries. This is an especially hard challenge because petroleum has this tendency to light on fire, so a huge concentration of it is especially difficult to keep safe. Release oil quickly so it can reach the market during a supply disruption. Keep maintenance costs low and last for decades. The actual solution, like many great engineering solutions, is incredibly elegant and simple. But before we talk about it, let’s start with how you might go about solving this: The naive solution: External floating roof tanks Enbridge tank farm, Cushing, Oklahoma, April 2010. Photo: roy.luck , CC BY 2.0 .…