In simple terms, the efficiency of a photovoltaic module can be described as the conversion rate from sunlight to electricity. Typical PV module efficiencies are in the range of 15% to 20%, while the most efficient PV modules on the market are a little over 22% efficient. Some laboratory prototypes have reached efficiency values above 40 percent, but they are still prohibitively expensive and unavailable for commercial use.
The efficiency of a photovoltaic module describes how much sunlight is converted into electricity. For example, if a panel with 20% efficiency is placed under 1000 watts of sunlight, it will produce 200 watt-hours of electricity per hour.
If PV modules of different brands are all exposed to the same sunlight, the PV module with the highest efficiency will generate the largest amount of electricity (Kwh) per day.
1. Why is the efficiency so low?
The efficiency of PV modules is often misunderstood. Natural gas power plants are over 50% efficient, and solar panels appear to be very inefficient at 20%. However, if you can realize these, you may be able to understand:
Natural gas, fossil fuels, etc. all release capacity under controlled conditions, and reduce energy loss as much as possible, and convert work into electricity.
The photovoltaic module converts a part of the light into electricity when the sunlight normally shines on the surface of the module. Some wavelengths of sunlight do not have power generation capacity or power generation capacity is very low, and some infrared light has better heat generation effect, and heat generation will affect the photoelectric conversion efficiency. So what PV modules can do is absorb as much light as possible, but cannot use all of it.
In addition, thermal power must purchase fossil fuels, which produce emissions when burned, while the sunlight that allows PV modules to operate is free and clean.
Photovoltaic modules are often criticized for being inefficient, and a 1,000-watt module, with a conversion efficiency of 20%, seems to be wasting 800 watts. However, consider that before there were no PV modules, we wasted all 1000 watts of sunlight!
It would be true to say that PV modules derive their power from abundant resources that would otherwise be wasted. Moreover, compared with the amount of resources, the resources of fossil fuels are limited, and mining requires costs, and all inefficiencies will lead to waste of fuel, operating expenses and more greenhouse gases.
Even if the conversion efficiency of photovoltaic modules is only about 20%, the resource of its denominator sunlight is unlimited, and the only limitation is that the floor space may be larger, so scientists are trying to improve efficiency and save costs as much as possible.
Even if the PV modules are at the lower end of the efficiency class, it does not affect the use of solar energy. In practice, lower conversion efficiencies often mean that solar systems require cheaper investments and potentially shorter payback periods. Higher efficiency usually means more advanced technology, and therefore comes with higher prices. In this case, you have to make sure that the extra savings can make up for the extra cost. The PV modules that achieve the highest ROI and shortest payback period are not necessarily the most efficient.
2. How to calculate the efficiency of PV modules?
The efficiency of PV modules is calculated through a set of Standard Test Conditions (STC), which are used throughout the solar industry. They were tested under laboratory conditions with a light source of 1,000 watts per square meter and a PV module surface temperature of 25°C. Likewise, the test light source must fully simulate sunlight propagating through the atmosphere.
When installing PV modules in homes and businesses, field conditions differ from ideal laboratory conditions. As a result, the actual efficiencies obtained by PV modules differ from laboratory efficiencies. However, standard efficiency ratings are useful for comparing PV modules under the same conditions.
PV modules can also be tested under other conditions called NOCT, which represent the nominal operating temperature of the cell. These conditions are designed to simulate typical project sites, and the NOCT efficiency test takes into account factors ignored in the STC test. However, keep in mind that both are reference values for panel efficiency. To understand the exact performance a solar panel can achieve in your home, you must obtain a professional design based on an on-site evaluation.
In addition, the CQC photovoltaic module leader certification also stipulates the level of energy efficiency products. The calculation of the conversion efficiency of the module is different from the conversion efficiency of the battery, because the module contains some redundant areas other than the cell, such as the frame and the gap between the cells. Wait. The efficiency rating of this product can be known from the CQC PV Module Leader Certificate.
3. You can also increase the power generation efficiency of your modules
With the development of solar cell manufacturing technology, photovoltaic modules have become more efficient. This factor is beyond the control of homeowners and businesses using components. However, smart design decisions can also improve the efficiency of solar systems.
The angular efficiency loss of PV modules is a very important factor in the design process. The orientation of PV modules affects the power generation efficiency, and if they are placed in the best position, the best inclination, it will increase the power generation:
Photovoltaic modules that receive sunlight from the front generate more power than those that receive sunlight diagonally. Ideally, components should have an orientation that maximizes efficiency in direct sunlight.
Solar companies use a variety of software solutions to calculate the angle of PV modules for maximum efficiency. If you live in the northern hemisphere, south-facing roofs usually get the most sunlight, excluding the shading factor of obstructions. For countries in the southern hemisphere, a north-facing roof is best.
Ground-mounted PV modules have more flexibility in orientation, allowing the bracket to be adjusted accordingly by calculating the exact angle that maximizes power generation from the orientation of the bracket and the tracking performance of the bracket.
It is very important to cooperate with a qualified solar EPC company, it is important to choose the right product and check its product certification, because the quality of installation is as important as the quality of PV modules.