Heat olive oil in heavy medium saucepan over medium-high heat. Add onion and sauté until golden, about 5 minutes. Add chili powder and stir 1 minute. Add water and sweet potato cubes. Cover pan; reduce heat to medium and simmer until potato is almost tender, about 10 minutes. Add tomatoes with their juices and beans. Simmer uncovered until chili thickens and potato is very tender, about 10 minutes. Mix in cilantro and orange peel. Season to taste with salt and pepper and serve.
Serves 3 or 4, and easily doubles