1. Burch, J.et al., 2006. Pipe freeze prevention for passive solar water heaters using a room-air natural convection loop.Conference paper: NREL/CP-550-39722, 1–6
2. Duffie, J. A. and Beckman, W. A. 1991.Solar engineering of thermal processes, 2, 3–92. New York: J. Wiley and Sons.