A new study “The energetic implications of introducing lithium-ion batteries into distributed photovoltaic systems” just released April 09 sheds new light on how much useful energy a solar system will produce over its life compared to the energy required to extract all the raw materials, process them then manufacture ship and install the final product as a working system. The study also looks at batteries.
The study from is already seriously out-of-date, for the input data it uses a 2013 study which itself uses energy input data from a study about solar panels and systems from 2011 at that time mono crystalline and poly crystalline solar panels were 14.1% efficient. In a standard residential format panel of 1.7x1.0m (approx) that would be a 250W panel Today Longi has just hit a Mono-PERC efficiency record of 24.06% for a production sized cell. This means that we are going to see 370W commodity priced panels within the next 12-24 months. That’s 150% the output of what the study was using in 2011 or an energy saving (not counting all the other savings which go even further) of 33%.
That would then take the estimate in the paper of EROEI 29 meaning the panel makes 29 times its energy back in the better locations and 14 times in the worst locations over its life. We could expect using the latest panels in better locations that this would go up to in excess of 40 times.
The good news batteries are improving solar panels are improving to a point where commodity priced solar roofs will be the next thing to play out across the world.