People looking to invest in solar are less concerned with the “first cost” of a residential PV system than the “total cost” over time. In fact, surveys say most consumers are willing to pay more for better long-term payback.
While generation capacity is important, understanding module efficiency is critical to ensuring the right technology is chosen.
Explaining the “total cost” and performance of the system over time can lead to higher revenue and a better installation.
It is often overlooked in home installations, but it is vitally important to the efficiency and long-term reliability of a solar module – its cells.
Broadly speaking, there are three main types of cell architecture: N-type, P-type, and Hetero-junction (HTJ).
Type P is the most common and accounts for about 80% of the world’s cell capacity. P-type PERCs have been widely used because they are generally less expensive to manufacture and faster to scale.
However, there are some drawbacks to its use in residential or domestic applications, such as the P-type’s susceptibility to Light Induced Degradation (LID), which is why users see permissible degradation in the first year on most devices. 3% modules.
Type N and HTJ modules allow higher conversion efficiency than type P and, due to their different technology, do not experience LID. The first year degradation of these modules is typically less than 2%.
Another noteworthy technical difference is that N-type and HTJ cells are inherently bifacial without any additional steps in the process.
This means that their conversion efficiency is typically higher than that of P-type cells, even when assembled in modules with white backsheets. White backsheets allow some light transmission and can produce measurable energy yield on the back of N-type cells, which means the kW/kWh conversion efficiency is higher than that of PERC-type modules. P.
Higher conversion efficiency translates into higher energy production and performance throughout the life of the system.
The last important point to consider is to consider how the cell is designed to remove the energy generated by the cell from outside the cell. A high number of bars and back contact cells are less susceptible to further energy loss if exposed to microcracks, since the percentage of the cell that does not generate energy from this microcrack is minimized. This, along with the physical and chemical properties, helps justify the guaranteed lower degradation rates of N-type and HTJ modules.
The two main drivers of economic performance due to long-term value are the module’s output (usually reflected in its kW/kWh conversion ratio) and its long-term degradation characteristics.
While typical P-type PERCs have a permitted degradation rate of 0.7% per year, N-types will have a guaranteed degradation rate of around 0.33%. Although those percentage fractions may seem inconsequential, they add up over time. For example, in year 25, a 0.7% degradation rate guarantee has a system operating at 80% of its rated capacity, while LG’s guarantee structure, for example, is 90%. .
Is the size better?
As manufacturers introduce 66-cell (or 132-cell equivalent) PV panels that take up more space than traditional 60-cell modules, it’s important to look beyond the nameplate rating.
Check the efficiency of the modules and, more importantly, make sure that you are using the correct dimensions when designing an installation together.
The other critical factor to consider is rack compatibility and balance of system (BOS).
If the installer fabricates or has to modify the rack on site due to module size, the savings can quickly be offset by increased installation time, BoS costs, or if you have to install with higher performance microinverters or optimizers, which are designed for these higher power modules.
The difference that a higher DC capacity of a module does not necessarily translate into a more efficient system, or even long-term performance. Using the value in kWh of the energy generated throughout the life of the system is the great equalizer because that is how you really understand what will offset your electricity bill (which is what you are looking for).
Solar system experts play a vital role not only in the installation of photovoltaic systems, but also in educating consumers about the benefits of solar energy. The average homeowner will not understand the reasons N-type cells are better than P-type or the trade-offs between efficiency and capacity. All you need is for your expert installer to tell you that he is making the best long-term investment.