A recent claim in the mainstream press has suggested that we would all be better off orientating solar PV panels towards the West instead of South. The conclusion of this argument would be the many millions of pounds spent on installing solar PV which faces South have not been invested wisely.
In fact, it was claimed that all installations in the northern hemisphere would be better off orientated to the West! So can this be right, or is it just another misinformed anti-green remark?
It isn’t too difficult to separate the wheat from the chaff in this case and see that this is just another sensationalistic headline to further undermine our understanding of renewable technologies. I can just hear the anti-green brigade now, “unproven technology, etc” so I thought I would nip it in the bud.
The study in question, which actually looked at the peak demand on the electricity grid versus the generated electricity from solar PV, was based in Austin, Texas. The research was based on a group of just 50 homes in the hottest peak summer months. Texas of course has a very different climate to our own and the biggest strain on their electricity grid is from air conditioning units used to cool homes and businesses, particularly in the late afternoon.
Therefore, if you want to generate your own electricity and have greater likelihood of using it yourself, it makes sense to face your panels towards the westerly afternoon sun when you need more electricity.
The points raised by the researchers do have some validity. This idea is already adopted by the more advanced installers here in the UK, where PV arrays are often split and faced both East and West to ensure the electricity is generated at the time the consumer most needs it.
This is of course relevant to people with constant daytime loads, such as offices or businesses that open in daylight hours, and cold stores in particular. For this type of customer, the opportunity to use their own free electricity instead of buying at peak-times is very attractive. The return on investment can be a very healthy 15-20%, and it also reduces the strain on the grid at peak times.
Just to be clear though, the argument that all solar panels should face West just doesn’t hold water here in the UK.
The Texas study found that West facing arrays generated 2% more than South facing arrays in the Summer but this is largely due to the fact that solar PV cells lose efficiency at very high temperatures, no doubt experienced in Texas but not a problem we face here in the UK.
A South-facing array will always generate more electricity here in our climate, but it does mean that you achieve peak generation in the middle of the day. If you generate more than you need and you end up exporting, then you get paid for export at about 5.5p. Irrespective of when you generate the electricity and whether you export or use it, you will be paid under the governments Feed in Tariff (FiT) incentive scheme for all the power your panels produce.
So to get the best financial return, you have to be savvy and decide whether you just want to harvest the sun to achieve a peak output for the FiT or ROC incentive scheme, or whether you are trying to offset your electricity load. A well-designed system will differentiate between the two and be designed to that strategy.
So are the panels better off just facing West? No, of course not, as long as the sun keeps rising in the East and sweeps through the South to the West.
Julian Patrick is an experienced electrical and mechanical engineer with a background in lecturing in solar PV and training in Germany. Julian established Freewatt in 2008 based near his former home in Stow, near Lincoln. The company has installed 5MW of solar at hundreds of locations including Co-op stores, The Epic Centre, fire stations and schools across the county.