How did solar get cheap?
Phase 1: 1950-1990s - NASA
Solar was invented in the US by Bell labs and pretty much only used by NASA who needed something very lightweight to power their space assets.
Phase 2: 2000 - Energiewind
The German government passed a law where it guaranteed that if you put solar panels on your roof the German government would pay you a high feed in tariff. Demand exploded.
Phase 3: 2005 - 2015 - China
In Europe German manufacturers could not meet their demand at home and Chinese entrepreneurs saw this fixed arbitrage opportunity and went all in. Chinese companies like Suntech took on huge government loans and built vast factories. Spain and Italy joined Germany with solar subsidies. Because of the price fixing in Europe the market arbitrage held as the solar cell manufacturing output in China exploded.
Phase 4 2015-2025 - Swanson’s Law
Once the big Chinese gigafactories were built, Swanson’s Law kicked in. This is the learning curve where manufacturers compound marginal gains and accumulate 1,000s of solutions to solved problems.
1. Ingots, originally they grew small Si crystals this was a slow batch process. Later they used continuous Czochralski pulling where you refill the crucible whilst the machine is still running. Saving hours of cooldown per batch. They also learnt how to grow huge single crystals that were 2-3 meters long.
2. Wafers, originally they sliced the crystals into wafers using saws. This was slow and turned 40% of the Si crystal into sawdust (kerf loss). The fix was diamond wire cutting, the wire was razor sharp, fast, much thinner than the saw, easier to keep clean and far less wasteful (4% kerf loss). Wafer costs plummeted.
3. Cells, you have to print silver lines on the back of the wafer to collect electricity. Over 15 years silver printing resolution improved and silver use was reduced by 70% whilst also blocking less sunlight. The mirror backing used to be aluminium which captured some solar energy as heat and was lost, so they added a dielectric passivation layer that captured more photons and improved cell conversion efficiency without changing materials.
4. Modules, engineers realised that by laser cutting panels in half they reduced electrical resistance in the cells. This means the panel runs cooler and produces more power.
Bifacial modules then emerged, instead of plastic backing. Panels were made with glass front and back, this means panels also collect energy bouncing from the ground below the panel which again boosts the panel output in operation.
These gains all compound to make the panels 90% cheaper over the course of 10 years.
Chinese manufacturers are now looking at perovskites as a paradigm switch. It’s essentially a superior crystal to silicon for absorbing light. You can make them from liquid chemistry and you can print them.
Silicon is great at capturing red and IR light perovskites can be tuned for blue spectrum.
You can then go tandem and pair both silicon and perovskites in the same modules.
Now panels are cheap, because they’re simple things to make. They cost around $0.10/watt ex factory. A solar installation costs around $3.00/watt and the panels themselves are now a very small part of the cost of a solar installation which is dominated by land, labour and structures.
Much of industry is like this. If you can consolidate manufacturing under one roof, you learn all the improvement opportunities much faster, because you just see more stuff.
