Solar Panels

A solar panel (also solar module, photovoltaic module or photovoltaic panel) is a packaged, connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications.

Because a single solar panel can produce only a limited amount of power, many installations contain several panels. A photovoltaic system typically includes an array of solar panels, an inverter, and sometimes a battery and interconnection wiring.

Theory And Construction

Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The structural (load carrying) member of a module can either be the top layer or the back layer. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. The conducting wires that take the current off the panels may contain silver, copper or other non-magnetic conductive transition metals.

The cells must be connected electrically to one another and to the rest of the system. Cells must also be protected from mechanical damage and moisture. Most solar panels are rigid, but semi-flexible ones are available, based on thin-film cells.

Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability.

Separate diodes may be needed to avoid reverse currents, in case of partial or total shading, and at night. The p-n junctions of mono-crystalline silicon cells may have adequate reverse current characteristics that these are not necessary. Reverse currents waste power and can also lead to overheating of shaded cells. Solar cells become less efficient at higher temperatures and installers try to provide good ventilation behind solar panels.[1]

Some recent solar panel designs include concentrators in which light is focused by lenses or mirrors onto an array of smaller cells. This enables the use of cells with a high cost per unit area (such as gallium arsenide) in a cost-effective way.[citation needed]

Depending on construction, photovoltaic panels can produce electricity from a range of frequencies of light, but usually cannot cover the entire solar range (specifically, ultraviolet, infrared and low or diffused light). Hence much of the incident sunlight energy is wasted by solar panels, and they can give far higher efficiencies if illuminated with monochromatic light. Therefore, another design concept is to split the light into different wavelength ranges and direct the beams onto different cells tuned to those ranges.[2] This has been projected to be capable of raising efficiency by 50%.

Currently the best achieved sunlight conversion rate (solar panel efficiency) is around 21% in commercial products,[3] typically lower than the efficiencies of their cells in isolation. The energy density of a solar panel is the efficiency described in terms of peak power output per unit of surface area, commonly expressed in units of watts per square foot (W/ft2). The most efficient mass-produced solar panels have energy density values of greater than 13 W/ft2 (140 W/m2).

Crystalline Silicon Modules

Most solar modules are currently produced from silicon photovoltaic cells. These are typically categorized as monocrystalline or polycrystalline modules.

Thin-Film Modules

Third generation solar cells are advanced thin-film cells. They produce high-efficiency conversion at low cost.

Rigid Thin-Film Modules

In rigid thin film modules, the cell and the module are manufactured in the same production line.

The cell is created on a glass substrate or superstrate, and the electrical connections are created in situ, a so called “monolithic integration”. The substrate or superstrate is laminated with an encapsulant to a front or back sheet, usually another sheet of glass.

The main cell technologies in this category are CdTe, or a-Si, or a-Si+uc-Si tandem, or CIGS (or variant). Amorphous silicon has a sunlight conversion rate of 6-12%.

Flexible Thin-Film Modules

Flexible thin film cells and modules are created on the same production line by depositing the photoactive layer and other necessary layers on a flexible substrate.

If the substrate is an insulator (e.g. polyester or polyimide film) then monolithic integration can be used.

If it is a conductor then another technique for electrical connection must be used.

The cells are assembled into modules by laminating them to a transparent colourless fluoropolymer on the front side (typically ETFE or FEP) and a polymer suitable for bonding to the final substrate on the other side. The only commercially available (in MW quantities) flexible module uses amorphous silicon triple junction (from Unisolar).

So-called inverted metamorphic (IMM) multijunction solar cells made on compound-semiconductor technology are just becoming commercialized in July 2008. The University of Michigan‘s solar car that won the North American Solar Challenge in July 2008 used IMM thin-film flexible solar cells.

The requirements for residential and commercial are different in that the residential needs are simple and can be packaged so that as solar cell technology progresses, the other base line equipment such as the battery, inverter and voltage sensing transfer switch still need to be compacted and unitized for residential use. Commercial use, depending on the size of the service will be limited in the photovoltaic cell arena, and more complex parabolic reflectors and solar concentrators are becoming the dominant technology.

The global flexible and thin-film photovoltaic (PV) market, despite caution in the overall PV industry, is expected to experience a CAGR of over 35% to 2019, surpassing 32 GW according to a major new study by IntertechPira.[4]

How to choose solar panels for your home

There are a number of solar panels on sale in the market nowadays. It is important to choose the right one for one’s home. A number of things should be considered to ensure the right solar panel is chosen and installed in the house.

The first thing one should assess before buying a solar panel is the amount of energy that is needed to power all the equipment that is used in the house. Once the exact electricity requirements have been ascertained, then an appropriate solar panel can be chosen. The size of the solar panel is usually dependent on the average power consumption figures and the amount of sunlight received by the house.



The Best Suited Caribbean Solar Panels

Are all solar panels the same?

Solar panels may all look the same to the untrained eye, but in truth each solar panel offers a trade-off between efficiency, cost and durability. There are three main types of solar panels on the market today:

Monocrystalline: These black panels are the most efficient at converting sunlight into electricity – converting about 18%. They also are the most expensive of the three types of solar panels. Monocrystalline panels have a lifespan of 30 or more years.

Polycrystalline: These blue panels are the most commonly used panel today. They are slightly less efficient at converting sunlight to electricity than Monocrystalline panels – converting about 15% – but they are also less expensive. They do however put out more power in low light. Polycrystalline panels have a comparable lifespan to Monocrystalline panels of 30 years.

Amorphous: A purple color, though they are the most expensive, these flexible panels, peal and stick are the least efficient at converting sunlight to electricity and they have a shorter lifespan (5 years or less) than Crystalline solar panels. Unlike crystalline silicon whose atoms are arranged in a very orderly fashion, the atoms in amorphous or thin film solar panels are not arranged in any specific pattern and in fact contain many structural and bonding defects. Amorphous solar panels are made by utilizing a vapor deposition process not unlike spraying the silicon which deposits a microscopic thin layer of doped silicon onto a glass substrate. Although thin film is less costly to manufacture than mono or poly crystalline technology they do suffer from several drawbacks, among them are a much lower efficiency. While mono and poly crystalline solar technologies typically produce power in the 12 to 18 percent efficiency range, thin film technology’s efficiency range from 6 to 9 percent. Another drawback with Amorphous technology is an anomaly known as the Staebler-Wronski effect whereby the conversion efficiency of Amorphous solar panels has the tendency to degrade causing a drop in output of up to 20% when it is first exposed to sunlight.And at peak of the day sunlight they Over heat causing a drop in power.These are simply not time tested. We do not recommend these as they can’t take the heat generated by the intense sun here in the Caribbean. They are more suited for colder climates.Most of our partners do not install amorphous panels. We feel we can’t sell what we would not use on our own homes.

Comments are closed.