The mere existence of the boat may prove its point, but it also highlights some major-league problems with sun power. Firstly, it cost $26 million to build. Secondly, it isn’t exactly fast, especially when you compare its projected 32-month circumnavigation with the world record of 48 days, seven hours — set by a sailboat, for gosh sakes. Thirdly, Planet Solar was designed for a very specific purpose and won’t serve any other functions very well. You’re not going to use this boat, or one like it, for day cruising, running to the fishing grounds or tubing and water skiing.