Most frequently asked questions
What is photovoltaic (PV)?
Photovoltaic (PV); is the process of direct conversion of photons of sunlight into electricity. The equipment required for this process has no moving parts and as a result requires minimal maintenance. In addition, the electricity is generated with no emissions and no noise.
What is a PV cell?
PV cell is the smallest semiconductor element within a photovoltaic module to perform the immediate conversion of light into electrical energy (DC voltage and current). A PV cell consists of two or more thin layers of semiconducting material, most commonly silicon. When the cell is exposed to light, electrical charges are generated and this con be conducted away by metal contacts as direct current (DC). The electrical output from a single cell is small, therefore multiple cells are connected together to provide a more useful output. Cells connected in this way encapsulated (usually behind glass) to form a weatherproof module or panel.
What is a solar module?
A solar modules or panels are series of solar cells wired together into strings and enclosed in self-contained glass units for harsh weather protection.
What is a PV array?
An array is an interconnected system of PV modules that function as a single electricity-producing unit.
What are the most common types of solar panels and their differences?
Monocrystalline – Polycrystalline – Amorphous
Monocrystalline Silicon: The most efficient, long lasting, and expensive solar panels are made with Monocrystalline cells. These solar cells use very pure silicon and involve a complicated crystal growth process. Long silicon rods are produced which are cut into slices of .2 -.4 mm thick discs or wafers which are then processed into individual cells that are wired together in the solar panel. They are effectively a slice from a crystal. This is the most efficient of the photovoltaic (PV) technologies. The principle advantage of monocrystalline cells are their higher PV conversion efficiencies, typically around 15-18%. In appearance they will have a smooth texture, dark blue or black color and you will be able to see the thickness of the slice. They are mounted in a rigid protective frame.
Polycrystalline Silicon: sometimes called multicrystalline panels are made from cells cut from an ingot of melted recrystallised silicon which is simpler to manufacture therefore a less cost. However, they tend to have a lesser PV conversion efficiency, with averages around 12% (approx. 20% less than monocrystalline panels). They have a striking shattered glass appearance and need to be mounted in a rigid frame.
Amorphous Silicon: Also known as “thin film” panels are not really crystals, but a thin layer of finely powdered silicon (amorphous silicon) or other photovoltaic material deposited on a base material such as metal, glass or plastic to create the solar sheet. These Amorphous solar panels cost less, but their energy efficiency is also much less so therefore more square footage is required to produce the same amount of power as a crystalline solar panel. They are less efficient with typical conversion of around 6% (approx. 60% less than monocrystalline). A characteristic of amorphous solar cells is that their power output reduces over time, particularly during the first few months, after which they stable. They do not have a long-range order
Do the solar panels store energy?
No, the solar panels only provide electrical power; they do not have the ability to hold that power. They can be used to recharge batteries that can be connected directly to power a device.
Do solar panels loose efficiency over time?
Yes, but keeping the panels clean from leaves, dirt and dust will maximize the efficiency. SUNPOWER2GO panels have a guarantee for 25 years with a warranty efficiency output of 90% for the first 10 years and 80% for 25 years.
What maintenance is required on the solar panel?
There is typically little or no maintenance required but they benefit from a non-abrasive cleansing agent. You may consider periodic inspection to ensure the panels remain clear of leaves, dirt, etc. Simply rinse them off (do not spray water on the panels when they are very hot). In winter applications brush the snow off with a broom or snow rake to utilize the maximum efficiency.
What are the possible problems with solar panels and how can I prevent them?
Solar panel failure is most often caused by water damage to the panel, sealant, or connections. To prevent damage or failure, mount the panel carefully. Be sure not to fix it horizontally, which encourages water collection in the frame. Also, allow for a sufficient air gap beneath the panel. Keeping your panel dry and clean will ensure efficient, maximum output.
Are solar electric systems safe?
Yes. Solar cells are mostly silicon, the primary component of sand. There is no exhaust and no toxic materials to leak out of the system. Energy created through solar electric systems produces no pollutants.
Are the panels fragile?
No. While high quality panels are made of tempered glass, they are quite strong. They pass hail tests, and are regularly installed in Arctic and Antarctic conditions.
How long do the solar panels last?
Monocrystalline panels are known to last 40 years or longer. Clean Energy Strategies warrantees the solar panel for three years from manufactures defects and workmanship, and guarantees the performance warranty of 90% for 10 and 80% for 25 years. Solar panels are designed to withstand hail, severe wind and weather conditions assuming proper installation.
Does solar power work in cloudy weather?
Solar panels do generate electricity in cloudy weather although their output is diminished. In general, the output varies linearly down to about 10% of the normal full sun intensity. Since flat plate solar panels respond to a 180-degree window, they do not need direct sun and can even generate 50-70% of their rated output under a bright overcast. A dark overcast might correspond to only 5-10% of full sun intensity, so output could be diminished proportionately.
Do solar panels work in cold weather?
Yes, very well in fact. Contrary to most people’s intuitions, solar panels actually generate more power at lower temperatures, other facts being equal. This is because solar panels are really electronic devices and generate electricity from light not heat. Like most electronic devices, solar panels operate more efficiently at cooler temperature. In temperature climates, solar panels will generate less energy in the winter that in the summer, but this is due to the shorter days, lower sun angles and greater cloud cover, not the cooler temperature. Operating temperature ranges are -40^C to +85^C.
What happens if the solar panels are covered by snow?
Some sunlight will penetrate several inches of snow, causing the panels to warm and eventually melt the snow. Spraying the panels with water from a garden hose can speed things along. On a single story roof, a snow rake can be the best option to remove most of the snow allowing the panel to melt the remainder quickly; we suggest using a model with a rubber squeegee blade attached to the end of it.
How do solar panels stand up to hail, wind, hurricanes etc?
Solar panels themselves are built using tempered glass for durability and safety and are designed to withstand hail and high winds. Depending on the wind-load requirements in your area, heavier mounting hardware may be required.
Do the panels need to face south?
South is best, but panels installed facing east or west still generate a very high percentage of possible power. Panels installed facing north provide the least amount of energy.
What angle should the panel be installed at?
Panels will catch the maximum sunlight, and therefore have the maximum output, when they are perpendicular (right angles) to the sun at solar noon (the most energy-rich time of day). The best year-round angle for your modules is approximately equal to your latitude. Because the angle of the sun changes seasonally, you may want to adjust the angle +15% for winter and -15% for summer from your latitude. The average latitude for Minnesota is approximately 45 degrees.
Can I use equipment directly from solar panels?
Yes. Solar panels will directly power equipment such as fans and pumps as long as the load is accounted for correctly. Equipment load that is greater that the output of the solar panel will weaken equipment efficiency, as overcast or cloudy days reduce output. Equipment that requires a more stable voltage should pair solar power with a battery backup.
Do I need a battery?
The battery is your energy reservoir. It stores up electrons until they are needed to run something. If batteries are routinely allowed to overcharge, their life expectancy will be reduced dramatically therefore a charge controller is recommended. For every 1.0 amp hour you remove or use from a battery, it is necessary to pump about 1.2 amp hours back into it to bring the battery back to the same state of charge.
What is a charge controller and do I need one?
Charge controllers prolong the life of the batteries. The main function is to prevent battery overcharging. It will sense the battery voltage, and reduce or stop the charging current when the voltage gets high enough. This is especially critical with sealed batteries that do not allow replacement of the water that is lost during over charging. For this very reason it is important to have a charge controller on any system that is over 5 watts. The SUNPOWER2GO controller also prevents reverse-current flow at night.
What is reverse-current flow?
Reverse-current flow is the tiny amount of electricity that can flow backwards through PV modules at night, discharging the battery. The SUNPOWER2GO controller has blocking diode to prevent the solar panel from discharging the battery.
What is a blocking diode?
A blocking diode connects to the cable and prevents the solar panel from discharging the battery in the absence of sunlight. For example, a boat battery will not act as an impedance load on a solar panel because of reverse blocking diodes that prevent nighttime battery discharging.