Solar panels collect radiation from the sun and actively convert the energy from the sunlight into an electrical Direct Current (DC) charge. When light hits the solar or photovoltaic (PV) cells inside solar modules, it activates the electrons on solar panel surfaces. The energy generated from photons striking the surface of the solar panels prompts electrons to jump from one atom to the next, creating an electrical chain reaction in the form of a DC charge, from which metal contacts in the solar cell can generate electricity.
A typical solar PV module comprised of solar cells is an aluminum-framed, glass coated panel that is approximately three feet by five feet. It produces 120 to 300 Watts peak (Wp) of direct current (DC) power. The more solar cells in a solar module and the higher the quality of the solar cells, the more total electrical output the solar panel can produce.
2. Are there different types of PV modules?
There are three types of PV: crystalline silicon, thin film and building integrated PV (BIPV). The solar cells inside the PV modules are the heart of the whole PV system. There are a variety of semiconductor materials and manufacturing processes used, but they share the basic concept of stringing together PV cells and – except in the case of some BIPV products – covering them with glass and encasing them in aluminum.
Crystalline Silicon – Monocrystalline (cSi) and multicrystalline silicon (mcSi) solar PV is the predominant technology that has been steadily improving over the last 50 years. Typical crystalline silicon modules efficiencies range from 12% to 18% and have warranties from 20 to 25 years.
Thin film – this is a broad range of technologies that is gaining market interest. Thin film technologies are those that have a very thin layer of semiconductor material deposited on a thin substrate. They are typically referred to by their chemical composition, and the most common ones are Copper Indium Gallium Selenide (CIGS), Cadmium Telluride (CdTe), and Amorphous Silicon (aSi). Efficiencies are typically 4-10% and warranties are 20-25 years. Some reports show that thin film modules degrade at a faster rate than crystalline modules, but since they have not been field-tested for as long, we must rely upon manufacturer claims and warranties.
Building Integrated PV – Building Integrated PV (BIPV) materials are roofing shingles, roofing membranes, windows, skylights, and awnings that are both an integral part of a building and produce electricity. BIPV products utilize either crystalline or thin film technology (or a combination) encased in a common product form factor (such as a roofing shingle).
3. Can you explain the different module ratings?
Standard Test Conditions (STC) DC watts is the nameplate rating of a solar module. STC watts are the electricity produced under controlled conditions.
Performance Test Conditions (PTC) DC watts is the rating of a module in real-world conditions as determined by the California Energy Commission.
The California Energy Commission (CEC) AC watts is the total PTC DC of solar modules factoring in inverter efficiency. The AC watt measurement conveys how much useable electricity comes out of the system. This is the number that available rebates are based on.
Real AC production will be the actual performance of the module after the inverter converts DC to AC.
4. How does grid-connected solar power work?
Solar panels convert sunlight into electricity via the photovoltaic process.
Power conditioning equipment converts the electricity from the panels to utility-grade alternating current.
The meter measures net power usage, turning backwards when the system generates more power than is needed.
The utility grid supplies supplemental power when demand exceeds the solar power system’s output and absorbs excess when the system output exceeds demand.
The customer electrical load draws power from the solar power system and/or the utility grid.
5. What types of installations are there? Which do you offer?
While PV systems have historically been designed for rooftops to minimize the allocation of otherwise useful space, the desire for larger systems and ancillary benefits are driving innovative design configurations. The following three locations are now common.
Rooftop – Still the most common system built, rooftop-mounted systems are fairly inexpensive. PV can be installed on any type of roof, but some roofing types, such as standing seam, are easier than others. Design considerations include penetrations or ballasting that is suggested or mandated by wind and seismic codes and the age of the roof. When considering installing a PV system that may operate in that location for 10-40 years, it is important to consider the age, warranty, and general condition of the roof.
Ground-Mounted – Ground mounted systems are typical in areas where land is not as much of a premium, where the system host can allocate the property for 10-40 years, for larger systems, and for typical single axis tracking systems. While this mounting type can often be the cheapest for large systems, the geotechnical requirements due to the results of soil analysis, the grading of the terrain, and the distance (for trenching) to the meter are the primary sources of increased cost.
Carport or Canopy – These types of systems produce power above a parking lot or garage and have the added benefit of shading the cars underneath (or other location, such as a picnic area). This mounting type has been developed into many designs, with the more aesthetic designs and installations in more challenging locations leading to higher costs. Due to the necessary size of the steel or aluminum structure, carports are typically the most expensive mounting type. A key source of value in a PV project can often be the inclusion of carport/canopy costs (and associated tax benefits).
6. How do EI Solutions installations differ from those of other system integrators?
EI Solutions (EIS) provides unique, customized solutions to our customers. As the smart choice in solar we provide an exhaustive assessment and design process to ensure that each and every solar project we build provides the maximum benefit to our customers. EI Solutions has one of the most experienced teams in the industry providing the highest level of expertise and project management.
7. How do you estimate system output? And where does this data come from?
We use the industry standard US National Renewable Energy Lab PV Watts solar estimation tool. It is an independently tested and validated tool that uses 30 years of climate and PV system data taken from different systems and a variety of angles.
8. What will be my system’s reliability?
EIS system reliability is close to 99%. EIS uses its web-based system to monitor solar power systems, and to respond quickly with assistance if needed.
9. How is energy production impacted by cloudy weather in my area?
EIS uses a National Renewable Energy Lab 30-year data set and other tools to estimate solar production in your specific location. The data set accounts for cloudy weather, dust, agricultural activity, etc.
10. What will my system really produce in kW and kWh over a year?
Your maximum system output in kW will usually be slightly less than the Alternating Current (AC) rating of the system due to electrical losses associated with:
Running wire from the array to your meter.
The minute differences in voltage and current between each PV module.
Dust, dirt, or any other unintentional covering that prevents the module from getting 100% of the sun’s rays.
11. What happens if my system produces more electricity than I need?
Under current incentive programs you are not compensated for producing excess electricity. We design systems not to exceed a company’s historical usage, taking into account any known near-term new load requirements.
Some municipal utilities offer "net metering", which offers account credit or payment for every kWh of electricity that is not consumed and is instead exported back to the grid. Municipal utilities vary in their net metering policies, and we will be happy to assist you in determining which policies apply to you.
12. How long do solar power systems last?
Under the sun’s ray, all solar panels degrade over time. The same sunlight that provides photons also provides more destructive ultraviolet and infrared waves, which eventually cause the panels to degrade physically. In addition, solar panels are also exposed to destructive weather elements, which can also seriously affect efficiency. Solar power systems have a design lifespan of 30+ years and crystalline and thin film modules are typically guaranteed under warranty for 20-25 years. Some reports show that thin film modules degrade at a faster rate than crystalline modules, but since they have not been field tested for as long, we must rely upon manufacturer claims and warranties.