Is north orientation best for me?

The Renewable Energy Testing Initiative (RETI), located at Brisbane Technology Park in Queensland, is an independent, real-time, in-field solar testing and monitoring facility. The facility features a large, unshaded testing field in conditions representative of the typical climate experienced in Australian communities. One of the driving forces behind the inception of RETI was to show the general consumer the benefits of installing solar PV onto residential houses and to also better understand how solar panels perform in different scenarios and conditions.

It is for this reason one of the first test parameters set up at the RETI test field was the addition of solar panels installed at different orientations (north, south, east and west) to really understand the performance of solar systems facing different directions.

Most people, including some design installers, are reluctant to put solar panels on east- or west-facing roofs as they fear that they may be losing too much power production and increasing their return on investment too much. However, RETI has produced some surprising results in the difference in performance between different orientated panels.

According to results recorded at the facility on 26 October 2012, the last time Brisbane received a cloudless sky for the entire day, the difference in power production between a north-, east- or west-facing solar system is not as significant as one would first think. Even south-facing panels produced a surprising amount of power.

The difference in power production between north and east was only 420 Wh (6%), with north producing 7.269 kWh and east producing 6.849 kWh for the day. The next best performer was the west panels producing 6.540 kWh for the day and as expected the southern panels produced the least amount of power at 6.069 kWh. North-, east- and west-facing panels all surpassed the Clean Energy Council Guidelines of 6.3 kWh based on 4.2 peak sun hours for Brisbane.

It is evident from these figures that based on purely kWh produced, the preferred orientation for installing solar systems is the northern aspect, followed by the east then the west. The increased performance of the eastern solar panels over the western panels can largely be attributed to the cooler conditions received by the eastern panels in the morning, left over from the cool nighttime period. The result of the temperature of the panels can also be seen in the instantaneous peaks of the different orientations. North peaks the highest but is closely followed by the eastern panels then the western panels.

Australia has recently gone through a boom period for rooftop solar in Australia, pushed largely by the generous feed-in tariff established to help kickstart the solar industry. The result of which helped create a huge demand in rooftop solar and it was economically viable to sell as much of the electricity back to the grid.

Now that the feed-in tariffs have been heavily reduced, perhaps it doesn’t make as much economic sense to sell as much electricity back to the grid, but rather use the electricity generated by the solar system to run the most power-intensive appliances in the home. For most households, the peak energy usage time is usually in the morning. Therefore, in this scenario, it may make sense to have an eastern-facing system.

With new challenges facing the solar PV industry, we cannot simply face panels north and hope for the best but the focus needs to be put back on the design of the solar system tailored around the lifestyles of the homeowner, along with better education for the consumer regarding their power usage.

*Daryl Wilson is the developer of the Renewable Energy Testing Initiative (RETI). He has been involved in the solar power, engineering and telecommunications industries for over 20 years and is the owner of solar installation and design company Energy Wise Group. He identified that Australasia and the Southern Hemisphere was lacking any real solar power field testing information so he decided to invest in the RETI facility. It was developed in consultation with solar design engineers, electrical engineers and solar installers and now has test and monitoring equipment for in-field solar testing. www.reti.com.au.