Solar power is one of the most promising solutions to reduce global fossil fuel usage. Environmental benefits and long-term cost savings for users have led to increased adoption in the commercial and consumer energy sectors, making solar energy technology's future very bright.
Improved Photovoltaic Cell Efficiency
The most common solar energy harvesting technology relies on photovoltaic (PV) solar cells to turn energy from the sun into electricity. The sun provides a specific amount of energy per surface area―roughly 1000W/m^2―which PV cells harvest and turn into electricity. As with any physical interaction, this process's efficiency impacts the amount of energy it can turn into electricity. Ultimately, the PV cells and solar panels' efficiency are limited by the physical characteristics of the materials that make up those panels. For example, the theoretical maximum efficiency of a silicon-wafer based PV solar panel is 30%―according to the Shockley Queisser Efficiency Limit―meaning that a 'perfect' one square meter solar panel could produce 300 watts of electricity.
The current commercialized PV market is dominated by wafer-based photovoltaic technology, which relies on materials like crystalline silicon or gallium arsenide, each of which has a theoretical maximum efficiency. Silicon-cell PV systems dominate the PV market with over 90% of current market share, even though gallium arsenide is more efficient at harvesting energy on a per-area basis.
Second-generation PV technology relies on thin-film cell technology, which consists of materials like cadmium telluride, hydrogenated amorphous silicon, and copper idiom gallium (di)selenide cells, which can reach efficiency levels of over 20%. The cost of thin-film cell PV has limited its commercialization, but the process will likely further penetrate the PV market in the next few years. As was true with the initially expensive wafer-based silicon PV solutions, thin-film cell PV technology will likely become more affordable and cost effective as the solar energy harvesting market expands.
Third-generation materials, such as perovskite, are the PV technology of the future. Perovskite PV technology is still in its infancy, but it may be the next large step towards systemic efficiency increases. Perovskite absorbs light across all visible wavelengths and is relatively easy to fabricate, as opposed to older PV module technologies. Third-generation PV technologies may soon be able to blend cost-effectiveness with efficiency. Perovskite offers the following characteristics:
· Semi-transparency
· More adaptable form factors
· Increased physical flexibility
Solar Panel Construction Optimization
Material efficiency plays a significant role in PV solar productiveness, but small tweaks to solar panel construction have increased overall system efficiencies by nearly two percent. Here are a few of these tweaks:
· Eliminating a black back sheet behind the solar cell reduces the overall temperature of the solar panel. This change makes the semiconductor wafer more efficient, since a warm silicon-wafer is less efficient at conducting electricity.
· Adding a reflective material behind the solar cell reflects photons from the sun back through the semiconductor wafer, essentially increasing the probability of photon interaction within the solar cell (and ultimately producing more electricity).
· Optimizing orientation and circuitry between solar cells can also improve overall system efficiency of PV solar panels.
These construction optimizations are generally proprietary and differ between solar companies, which explains the slight variation in panel efficiencies when we compare solar panels. As of 2020, the most efficient commercially available solar panel can harvest 22.6% of the energy it is exposed to by the sun. In July 2017, US scientists developed a prototype solar cell capable of achieving 44.5% efficiency. While this prototype was nearly twice as productive as its commercially available counterpart, production costs prove prohibitive at this point.
Solar Panel Cost Reduction
Perhaps the largest recent improvement in commercially available PV technology is its reduction in cost. The cost effectiveness and abundance of silicon wafers in other industries―such as consumer electronics―and continual optimization of silicon wafer manufacturing processes have significantly accelerated PV technology's affordability. As the PV market expands and the design requirement for more efficient solar panels grows, the current cost-prohibitive, uber-efficient solutions will be able to compete with the currently pervasive silicon PV systems.
The cost of a silicon-based solar module (per each single solar panel) has also dropped by 89% in the last decade. In 1977, PV cells cost $77 per watt of electricity they produced; today, solar energy systems cost roughly $0.13 per watt. However, these numbers are almost entirely exclusive to first-generation PV technology. Silicon wafer-based PV panel systems are continually getting better, but more efficient systems will eventually win out. However, there are currently no commercialized systems that can compete with the cost of silicon PV systems.
PV Inverter Efficiency & Solar Power Storage
Other PV solar system optimizations have caught recent wind as well, helping increase PV solar systems' overall efficiency. Solar panel inverters convert the solar panel grid's DC energy to AC, which can reduce efficiency. Recent breakthroughs in wide-bandgap power electronics have significantly improved the inverters' efficiency (and physical size). Additionally, battery technology improvements have enabled solar energy storage systems―such as the Tesla Powerwall―to store harvested electricity more efficiently than ever before.
Conclusion: Solar Industry is Primed for Growth
Photovoltaic solar energy harvesting is gearing up for widespread adoption at a rapid rate. Reductions in manufacturing costs and increases in electrical productivity per panel are also making solar panel systems available to more consumers. The solar power industry is primed for widespread adoption and unprecedented growth.