Solar panels in a field in Germany Design Pics / Alamy
Double-sided solar panels that tilt based on the sun’s position could boost the amount of energy collected. The two approaches existed independently before, but researchers have now looked at the effects of combining them.
Carlos Rodríguez-Gallegos at the Solar Energy Research Institute of Singapore and his colleagues found that double-sided solar panels that track the sun would produce 35 per cent more energy and reduce the average cost of electricity by 16 per cent.
The goal for any solar panel is to absorb as much energy from the sun as possible, says Rodríguez-Gallegos. At present, solar panels around the world are predominantly installed with a fixed orientation, and absorb light only from one side.
The advantage of using two-sided solar panels is that they can also absorb energy that is reflected by the ground onto their rear side, says Rodríguez-Gallegos.
Two types of sun-tracking solar panels exist. Single-axis trackers follow the sun over the course of a day, moving from east to west. Dual-axis trackers also follow the sun over the course of a year, changing position according to the seasons, because the sun’s elevation is higher in summer and lower in winter.
In their analysis, the team calculated the global energy generated by a variety of combinations of different solar panel set-ups.
They analysed global weather data from NASA’s orbiting Clouds and the Earth’s Radiant Energy System instrument and then estimated the total energy generated in different set-ups. The team found that double-sided panels would produce 35 per cent more energy when combined with single-axis trackers, and 40 per cent more in combination with dual-axis trackers.
The group also factored in the costs involved in the materials, construction and maintenance of these solar panels, which differs between countries.
Combining double-sided panels with single-axis trackers would reduce the levelised cost of electricity – an indicator of how much a consumer pays per kilowatt hour of solar energy produced – the most, by 16 per cent for the majority of the world, says the team.
MyPenWroteThis on June 6th, 2020 at 17:10 UTC »
For visibility I'll move this comment to the main thread. This was a response to u/bostwickenator's comment about whether bifacial panels are really worth it.
Finally something I know about. I've been working in renewable energy for a few years including both grid scale and distributed scale solar and wind project development.
You're right to wonder whats the point. Bifacial solar panels are a pretty niche technology. The biggest limiting factor isn't actually cost or space, but the albedo, or reflectivity of the surface below the panel. This headline makes it sound like you just slap some solar cells on the bottom and you increase production but it entirely depends on the surface below it.
Dirt, for example, is a terrible reflective surface. Youre unlikely to get more than a couple percent increase in production if youre lucky. A large rooftop however, painted white during installation, might actually work. Residential rooftop youre obviously size constrained but a giant amazon warehouse lets you spread the panels out to prevent shading, and the sunlight that gets through has a better chance of reflecting onto the bifacial surface.
You are right that many ground mounted grid-scale sites arent space constrained but thats not always the case. Developing in much of California, for example, often means site constraints due to limited land. But even in the case that you have no limitations, it might be cheaper to install bifacial panels.
Solar installations are fairly simple compared to most other energy resources, but they still have a lot of necessary infrastructure. Each panel needs a seperate rack which is a big part of cost on a per watt basis. Every line of panels also needs it's own string inverter and wiring. (You can use one large inverter for the whole site but then if it goes down you lose all production.) Every additional line of panels means more installation time, more land lease payments, possibly more land owners you need to appease. All these costs are minimized by installing bifacial panels, because you've significantly increased production with only an increase in your module cost.
Single axis trackers are definitely more commonly used. They're only usable for ground mount sites but can increase project yield from 1,700 kwh/kw to 2,300 kwh/kw. My company uses SAT racking whenever possible. It's almost always worth it.
Bifacial panels are relatively new but they aren't necessarily changing the game. They're definitely more useful if you have complete control of the site and a surface with a strong albedo effect.
PrinceHumperTinkTink on June 6th, 2020 at 16:32 UTC »
I never even thought of that.
bostwickenator on June 6th, 2020 at 15:25 UTC »
If they only increase efficiency by 35% using both these technologies isn't it more sensible to simply take that backwards facing material and just make a second panel. This nets you 100% gains even without expensive steering equipment. Most solar installations at grid scale aren't space constrained and most domestic installations are roof mounted so they can't be double sided.
Edit: It looks like they are talking about cells where they are doping both sides of a single wafer. The article doesn't mention it and the paper just says bifacial but that seems to be the meaning
Edit2: Many TIL below, good discussion!