SOLAR ENERGTY

When people think about alternative or renewable energy, the first image they keep in mind is often large blue or black solar panels on roofs, or portable highway signs equipped with small panels. These solar panels, also known as photovoltaic (PV) modules, convert sunlight into electricity and have been the basis of renewable energy for decades.

PV is traditionally used in areas where there is no practical source of electricity but where there is abundant sunlight. Solar panels are often used for off-grid applications, such as powering cabins, RVs, boats, and small electronic devices in locations where grid service is unavailable. Recently, "grid-interactive" solar electrical systems have become more common as a cost-effective way to integrate solar power into our daily lives. We can now utilize available solar energy while still relying on a secure electrical grid..

A photovoltaic (PV) module, or solar electric panel, is the smallest replaceable unit in a PV string. The module is an integrated unit that provides support for numerous PV cells that are electrically linked and protected from the elements. The electrical output of the module depends on the size and number of cells, their electrical connectivity, and the environmental conditions to which the module is exposed. Solar panels come in many forms and sizes and can be made from various materials. However, the most commonly used module is a "glass plate sandwich" containing 36 PV cells connected in series to produce enough voltage to charge a 12V battery. The purpose of this structure is to provide a rigid package that protects intercellular connections from the environment. Positive (+) and negative (-) connectors are located on the back of the junction box. Modules can feature an individual metal frame or be protected with a rubber seal, designed for integration into a larger mounting system that holds multiple modules together.

The MPPT (Maximum Power Point Tracking) type of solar charge controller is specifically designed to ensure that your solar panel operates at its maximum power point. Using this type of solar charge controller can increase charging efficiency by as much as 30%.

PV modules are highly sensitive to shading. Unlike solar thermal panels, which can tolerate partial shade, many brands of PV modules cannot even tolerate the shadow of a leafless branch. Obstacles that create shadows can be defined as soft or hard sources. If a tree branch, roof vent, chimney, or other element creates a shadow from a distance, the shadow is diffuse or scattered. These soft sources significantly reduce the amount of light reaching the cells within the module. Hard sources are defined as those that completely block light from the cell, such as leaves, bird droppings, or debris sitting directly on the glass. If even a single cell is covered by a hard shadow, the voltage of that module will drop to half its value as the bypass diodes activate to protect the system.

Partial shading on cells can reduce the power output of a solar electric panel by 50%. When an entire cell is shaded, it can act as a consumer of the energy produced by the rest of the cells; in this case, the module activates its internal protection. The module will redirect power around the affected series string. If even one cell in a series is shaded (as seen on the right), it will likely cause the module to reduce its power output to half of its full potential value. Furthermore, if a row of cells along the bottom of the module is completely shaded (as seen in the image above), the output power can drop to zero. The best way to maintain peak output is to avoid all shading whenever possible.

Solar panels should have durable connectors on the module. These connectors must be firm and the wiring method simple, while still providing a secure electrical connection. Most modules have sealed junction boxes to protect these links. Field testing shows that PV cells and the interconnections within the module rarely fail. Most problems occur in the module's junction box, where the inter-module connections are made. These can often be repaired on-site without replacing the entire module. Before purchasing a solar panel, inspect the junction box to ensure it is easy to access. Are the terminals robust, and is there space to connect a bypass diode? Is the junction box of high quality?

It is also critical to ensure that modules are mounted correctly and that all connectors and wires are well-protected from the weather and potential physical damage. Improper installation can lead to performance degradation and serious safety issues, including fire risks. Always adhere to the manufacturer’s instructions, as well as local building and electrical regulations, during the installation of solar panels.