Contents
Introduction
Efficiency of Solar Power
Multi-Junction/Tandem Cells
Thin-Film Cells
Perovskite and Bifacial Cells
Solar Panels In Space
Concluding Remarks
Bitesize Edition
We’re back diving into the world of energy and electricity production. We’ll begin diving into solar power generation today with a discussion on exciting, innovative solar cells such as multi-junction cells, perovskites, and quantum dot solar cells.
Interestingly, as I’ve discussed for previous electricity and energy production methods, using methods that are best suited to our environments ensures we’re gaining the maximum efficiency possible. With solar panels, the potential for a journey into space would change the game. Find out more below.
Introduction
After a few weeks off, it's time to return to the future of energy.
We’ll begin to explore electricity production through solar power, the process which converts the sun’s energy into electrical energy.
There are many characteristics to explore regarding these energy or electricity production methods we’ve discussed beforehand, so we’ll begin by discussing the efficiency of solar power.
Efficiency of Solar Power
In terms of solar panels, efficiency refers to how much energy from the sun’s rays is converted into useful electrical energy. Solar panels also produce heat energy, which is wasted energy. Typical efficiencies from multiple sources are quoted as 15-20% for monocrystalline solar panels. Monocrystalline panels are made from single silicon crystals and offer higher efficiency at a higher price than polycrystalline solar panels made of multiple silicon crystals.
The Shockley-Queisser limit denotes that the single solar cell efficiency limit is 33.7%. This only applies to solar cells with a single p-n junction, which refers to the boundary between two types of semiconductor materials.
Many innovators in the solar industry are working on improving these efficiencies, considering the materials used, solar cell design, and the environment in which they are utilized. As discussed when I deep-dived into wind power, taking advantage of our environment is of vital importance in our clean energy transition. Solar panels in the winter in Scandinavia wouldn’t be too useful, because it is dark. All the time.
Multi-Junction/Tandem Cells
Multi-junction cells, or Tandem Solar Cells, include multiple layers that absorb different wavelengths of sunlight. This has seen efficiencies rise to as high as 45%. Theoretically, more junctions absorbing photons increases maximum efficiency.
An interesting section of multi-junction cell research comes from the third and fifth columns in the periodic table, namely gallium indium phosphate (GaInP), gallium indium arsenide (GaInAs), and gallium arsenide (GaAs). Three-junction cells using these semiconductor materials have reached over 45% efficiency.
Multijunction cells are also being used as a basis for deeper exploration using alternative materials, such as organic solar cells, copper indium gallium selenide (CIGS) solar cells, and Cadmium Telluride (CdTe) cells.
Thin Film Cells
Thin-film solar cells place thin layers of semiconductor material onto glass, plastic, or metal, for example. The advantage of thin-film solar is less material is used and the manufacturing process is easier, reducing production costs. However, thin-film tech cells such as CIGS and CdTe currently have lower efficiencies than traditional single-cell silicon-based cells.
Perovskite and Bifacial Cells
We also have Perovskite Solar Cells and Bifacial Solar Panels.
Perovskite is a calcium titanium oxide mineral with the formula CaTiO3. Solar panels using Perovskite use the mineral in the active layer. Back in 2009, these panels demonstrated a 3% efficiency level. This has reached over 25% today. The challenges to Perovskite cells are decomposition when reacting with moisture and oxygen, and limited operational lifetimes limiting economic scalability potential.
Another interesting development is bifacial solar cells, which generate electricity on both the front and rear of the panel. This works using reflection from surrounding surfaces, which works to improve efficiency. However, costs increase with having two-sided cells which will use more materials and are dependent on environmental conditions, this increased cost of manufacture may not be justified in efficiency gains. Also, installation is more difficult since you can’t just install the panel onto a flat surface like traditional one-sided panels. Both sides need to receive as much sunlight as possible.
A final developing panel type is quantum dot solar cells. These currently struggle to keep up with alternative cells in terms of efficiency, reaching 18.1% as of 2022 data. Theoretically, the efficiency of quantum dot solar cells can reach around 66%.
Solar Panels In Space
Finally, the importance of the environment is pivotal in solar panels and the direction the industry is moving in. When we send our solar panels space-bound, there is no atmosphere diluting the sun’s rays. This can lead to space-based solar panels generating multiples more power than their earth-based counterparts. Currently, solar panels in space are used to power satellites and the International Space Station. The difficulty is beaming the power down to Earth. Perhaps development in the use of lasers or microwave beams could aid this pursuit. In fact, in June last year, the California Institute of Technology claimed to have beamed electricity from space-based solar panels back down to Earth using microwave beams.
However, these space-based panels would degrade eight times faster than those on Earth, so more durable materials would need to be used, such as gallium arsenide (GaAs). However, gallium arsenide is more difficult to source than silicon at 17 parts per million. Sounds like we need to start some asteroid mining!
The scenario of solar panels in space will also have geopolitical effects. We’ve seen satellite warfare in recent years, with Russia sending one satellite to grab another and throw it out of orbit and blowing up another in 2021. Yes, satellites with arms grabbing onto other satellites. We’ve also seen visual impairment tactics such as lasers used against satellites. There’s potential that solar panels in space would be subject to similar attacks, just as we see infrastructure attacks on pipelines or cyber attacks on transmission grids back here on Earth.
Concluding Remarks
I was also going to discuss the environmental impact, affordability, and scalability of solar power today, but I seemingly had too much fun discussing newly developing solar panels and their efficiencies. More on the characteristics I didn’t get to discuss next week.
Thanks for reading! If you want more then subscribe on Substack for these posts directly to your email inbox. I research history, geopolitics, and financial markets to understand the world and the people around us. If any of my work helps you be more prepared and ease your mind, that’s great. If you like what you read please share with others.
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Sources:
https://www.sciencedirect.com/science/article/abs/pii/S1364032115012149
https://www.greenmatch.co.uk/blog/2014/11/how-efficient-are-solar-panels
https://www.researchgate.net/figure/Basic-diagram-of-Phtovoltaic-solar-cell_fig1_323354575
https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit
https://www.energy.gov/eere/solar/multijunction-iii-v-photovoltaics-research
https://en.wikipedia.org/wiki/Copper_indium_gallium_selenide_solar_cell
https://www.sharp.eu/solar-energy/learn-about-solar-panels/monocrystalline-solar-panels
Great stuff here, I’ve got article coming out on fusion this weekend. The energy mix of the future is bright! (No pun intended 😎)