Is It Really Just About Who Is Cheapest?

In a market where all we seem to hear is price, price, price, isn't it time we started to talk about the differences between the modules, the manufacturers, the distributors and the installers? In a market where we are not all the same why is price seemingly the most important question? Let's change this soon for the benefit of the industry and its clients.  If we can help the end users to understand the differences and varied choices out there; would the quote always have to be the cheapest or would quality, warranty, service and performance become more involved when deciding what and who to use for your renewable energy solution for the coming 25 years?

It takes on average 8.33 minutes for the sun's energy to reach the Earth. What we do with this energy is entirely up to us. At 8.33 solar we manufacture high quality and high efficiency solar photovoltaic (PV) modules that convert the sun's energy into useful electricity for residential and commercial power needs. PV modules convert the sun's energy into electricity without the use of moving parts, generation of noise and pollutants or other waste material, which makes PV modules a safe; robust, reliable and long lasting source of clean energy. In addition, PV technology - together with other renewable energy technologies - help tackle the global warming issue and contributes to the green economy. While useful lifetime of PV modules spans up to 25-30 years, initial PV module power degrades over time resulting in lower power output. The PV module power degradation is mainly attributed to the so-called light induced degradation effect. The LID effect occurs when PV cells are exposed to light for extended period of time or injected with minority carriers. The LID effect is particularly prevalent in boron doped Czochralski silicon with high oxygen content which is used to produce mono-crystalline PV cells and modules. Multi-crystalline silicon crystals "“ used to produce multi-crystalline solar cells and modules "“ also have oxygen and use B doping. Reducing or eliminating the LID effect can increase PV module lifetime power output, therefore generating more energy and benefits to end users. 8.33 Solar gallium doped mono crystalline silicon PV modules exhibit lower LID effect and generates more power during their useful lifetime than boron doped mono-crystalline and multi crystalline PV modules.

Light induced degradation

Mono crystalline silicon used in the terrestrial PV industry is grown using Czochralski method as boron doped material. Chunks of pure silicon are melted in a graphite crucible, a small seed of silicon is then brought into contact with the surface of the melt to start crystallisation. Molten silicon solidifies at the interface between seed and melt as the seed is slowly withdrawn. An ingot begins to grow both vertically and laterally. Czochralski grown silicon ingots are used to manufacture wafers and high efficiency Laser Grooved Buried Contact (LGBC) mono crystalline solar cells which are then used to produce PV modules. Despite high efficiencies using LGBC technology the solar cells suffer from light induced degradation effect.

Light induced degradation has been shown to correlate with boron and interstitial oxygen. In particular, the degradation effect is due to the formation of a boron-oxygen complex when both oxygen and boron are present in the material. This can be attributed to a drawback of Czochralski silicon growth process - silicon is contained in liquid form in a crucible during growth and as a result impurities from the crucible are incorporated. In the growing silicon crystal, oxygen and carbon are the most significant contaminants.  By reducing or substituting boron dopant for other materials such as gallium or phosphorus or eliminating oxygen from the Czochralski gown silicon material the light induced degradation has been shown to be significantly attenuated. While eliminating oxygen from the Czochralski grown silicon is an expensive proposition for industrial PV cell and module manufacturing, at 8.33 Solar we dedicated our research and development efforts to substitute boron dopant with alternative gallium dopant.

Benefits of gallium doped

Doping Czochraski grown silicon with gallium instead of boron has the benefit of attenuating the light induced degradation effect which significantly reduces efficiency and power degradation. This is mainly due to larger gallium covalent atom radius (122pm) than boron covalent atom radius (84pm). Larger gallium covalent atom radius prevents the formation of gallium-oxygen compound in the silicon lattice, which in turn is why gallium doping does not produce a metastable compound and exhibits significantly lower light induced degradation effect. Figure 1 illustrates expected 8.33 Solar boron doped and gallium doped PV module power degradation over 25 year horizon.

Boron doped mono crystalline PV modules are expected to degrade on average at 0.897% per year while gallium doped mono crystalline PV modules are expected to degrade on average at 0.422% per year. Therefore, 8.33 Solar gallium doped mono crystalline PV modules offer customers industry leading power output guarantees: minimum 95% within 12 years and minimum 95% within 25 years of the initial nominal peak power. Industry standard is minimum 90% within 10 years and minimum 80% within 25 years. Reduced efficiency degradation ensures that gallium doped PV modules to produce higher power output over their useful lifetime than conventional boron doped mono crystalline and multi crystalline PV modules. 8.33 Solar gallium doped mono crystalline PV modules are expected to produce on average 6.5-10% more power over their useful 25 year lifetime. More power means more energy yield and better return on investment for our customers.

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