During past wars, the US, and many other countries often created War Bonds in order to help finance the war effort. This is not much different.
We currently have a situation where a lot of money is needed to help finance the development and/or improvement of non-polluting energy sources. The oil companies are already getting billions of dollars of government support but there are those in congress who would eagerly stop similar moneys going into non-petroleum energy. Rather than fight them, let's just maneuver around them. A bond is not a tax, rather, bonds are purchased at one value and after a set amount of time increases to the face value of the bond. In this case they are people's support in moneys and belief that there are a variety of ways to power America.