Solar in Fresno and the greater Central Valley has been a hot topic. So you’re ready to invest in a solar system but now you want to understand what you are about to buy. The largest and most expensive component of a solar system are the solar electric panels; also known in the industry as photovoltaic (pv) modules. To help you determine which solar panels are right for your business, this article will provide you with a basic understanding of the different types of solar panels available and a list of key considerations.
Types of Solar Panels
There are three primary types of solar pv panels available:
Monocrystalline panels (monos) are made from a single crystal rod of silicon. This silicon rod is sliced into thin wafers to form the solar cell.
- Good power-to-size ratio.
- Outstanding performance in cooler conditions.
- Some leading units now have over 18% conversion efficiency.
- Previously the most commonly used technology in the world, with over 50 years of technological development.
- Excellent life span / longevity. Usually come with a 25yr warranty.
Polycrystalline panels (polys) are made from multiple silicon crystals. These solar cells are formed when molten silicon is poured into a mold to form an ingot. Once cooled, the ingot of silicon is sliced into wafers to form the solar cell.
- Good efficiency.
- Generally speaking, marginally less expensive to produce than monocrystalline.
- Slightly better performance in hotter conditions (lower heat derating coefficient)
- Excellent life span / longevity. Usually come with 25yr warranty.
Note: Monocrystalline solar panels are not necessarily better or more efficient than polycrystalline.
Thin-film panels are usually made out of amorphous-silicon alloys that are deposited in thin layers onto a glass or metal backing material called a substrate. Unlike monocrystalline and polycrystalline modules, many thin-film modules are flexible and as a result can be used in different applications.
- Lowest efficiency.
- Expected lifespan is less than crystalline panels.
- Optimal efficiency in hot weather, less effective in cooler conditions.
- 3-6 month ‘breaking in’ period where long term output is exceeded.
- Requires 2-3 times more panels and surface area for same output as crystalline.
Comparing Solar Panels
When looking for solar energy panels, there are a couple of key factors to consider:
Manufacturer warranty: Today there is fierce competition between manufacturers. This brings more and more parity in the cost of panels. So beyond price there’s quality of construction and warranty. When choosing a panel, we also look at the manufacturer’s history and longevity because their warranty is only good if they’re still in business.
The specification: To us the specifications carry the least amount of weight but none the less do help determine the quality of the panel. The first measurement to look at is the rated power at STC. This is simply a measurement of how much power, measured in watts (W), that the solar panel will generate under a set of conditions called Standard Test Conditions (STC). The standard test conditions are:
- 1,000 watts per square meter of solar irradiance
- Solar panel temperature of 77 degrees F (or 25 degrees C)
The second measurement is the solar panel efficiency which is simply the ratio of output power to input power. For example, if the solar panel receives 1,000 watts per square meter of sunlight, and it produces 100 watts of output power, it has an efficiency of 10%. Most solar panels will have an efficiency rating between 10% and 19%. Usually, the higher the efficiency the more expensive the solar panel will be. The higher the efficiency the more power will be generated in a given area. Certain manufacturers tout their superior efficiency and claim higher outputs, this is not necessarily true. It simply means higher output per square foot. In certain circumstances where roof space is at a premium the cost of the highly efficient panels is justified, but in most cases it is not.
These rating will give you a fair comparison but keep in mind that in the real world the actual output of your solar system will be determined by more important factors. For example: the direction and angle the panels are facing, shading, the temperature, and the inverter(s) specified.
Cost/production: The ultimate measurement of a system’s efficiency, taking the above factors in to account, is the systems annual kWh production. Taking the cost of the system and dividing it by the estimated annual kWh production will show you who is offering the best bang for your buck. To insure that the estimated production is accurate, your proposal should include worksheets from the California Solar Initiative (CSI). These will show you exactly how the estimate was calculated.