Preheat the oven to 275°. Line a baking sheet with foil and lightly oil the foil. In a small saucepan, combine the orange zest with the water and sugar and bring to a boil. Simmer over moderate heat until syrupy, about 10 minutes. Drain the zest. Spread the strips out on the baking sheet and bake for about 45 minutes, or until dry but not browned. Let cool completely, then grind to a powder in a spice grinder.