ReNew reader Clive Heckenburg explains how clever solar panel placement has helped keep his roof cool.
I live in Brisbane and had a 4560 watt solar PV system installed late October 2011 on a roof facing north/north-west. It consists of 24 x 190w, Trina TSM – 190DC01A panels with a SPH 50 5000 watt inverter.
As an aside, the panels were placed landscape covering nearly the whole north/north-west roof. The purpose of this was two-fold, generating as much power as possible for the area and reducing the heat radiated from the roof into the ceiling cavity, with the panels acting like a safari roof. Since the panels have been installed the temperature difference between rooflines, when the sun is directly overhead is about 7°C, being 38°C for the roof under the panels and 43°C for the exposed roof.
Temperatures were measured in the ceiling cavity using an infrared thermometer, when the room temperature is below 26°C. Vents are still to be placed in the gable ends of the ceiling cavity to aid cross ventilation. So hopefully the house should be a bit cooler in the afternoons and evenings. So far this (mild) summer, we have not needed to use fans in what is usually an extremely hot room.
Uncertain output
Unfortunately I do not seem to be achieving the maximum benefit: output so far is averaging 20kWh per day. Output starts from as early as 5am and stops around 6pm. The problem is from around 9.30am to 3pm the output does not change significantly, staying in the mid 3000s.
Other systems I am familiar with have a definite peak as the sun moves overhead. One observation is that on overcast days, when there’s a sunny break in the cloud, output will jump between high 4000s to early 5000s for a few seconds, then down to as low as a few hundred before rising to mid 3000s. Returning to mid to high 2000s once the sun is again blocked by cloud cover.
This entry was posted on Tuesday, January 10th, 2012 at 2:44 pm