A scientist is performing an experiment and wants it to run on a combined photovoltaic and solar thermal system. The sunlight around his laboratory provides an average power density of 300 W/m2 for 6 hours each day. His experiment demands energy for a heater to convert 1500L of water to steam at 150℃ every day. The initial temperature of the water is 20℃. How many solar panels will he need to buy?