Solar panels, or modules, are the heart of any solar power system because they convert sunlight to electric energy.
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Solar panels, or modules, are the heart of any solar power system. Solar panels that convert sunlight to electric energy are referred to as photovoltaic panels (PV for short). The PV panels collect sunlight and turn it into direct current (DC) power. This current is created when photons hit the panel and cause electrons in the silicon to be excited. These excited electrons are conducted out of the solar panels and are transmitted to a DC to AC inverter for interconnection to the public utility grid. Alternatively, this electric energy can be stored in batteries for off-grid applications.
While a number of photovoltaic materials exist and have been tried over the years, the globally dominant and commercially cost viable solar module is made out of crystalline silicon. There are a handful of niche lower efficiency thin-film modules still on the market, but the two main types of silicon PV panels are monocrystaline and multicrystaline. Their names derive from the different processes that are used to make the silicon PV cells in the panels. Monocrystaline panels use silicon with a single crystalline structure (like a diamond), whereas the multicrystaline panels use silicon with grain boundaries between crystalline structures in various orientations reducing the conductive properties of the material. Monocrystalline cells have been traditionally more efficient, but also more expensive to produce. This gap is closing quickly.
More recently, PV manufacturers have been rapidly innovating on PV panel design beyond the cells. Some notable advances include incorporating smart electronics directly into each module to improve uptime and performance. Also, improvements for installers and integrators are coming in the form of improved ease of use and lower material cost of racking systems that easily mount panels to rooftops and other.
‘Smart modules’ are one important innovation that incorporates DC optimizers into the junction box of the module. This allows the owner of the PV system to monitor (and optimize) the performance of each individual panel. Traditionally, the performance of the weakest PV panel limits the performance of all other modules electrically connected to it in standard systems. Like the weakest link in a chain, the underperformance of one panel can drag down all the others. With smart modules, it is possible decouple each modules’ performance individually for maximum energy harvest. Panels with smart electronics also allow designers to build systems with longer strings of panels reducing BOS costs.
Manufacturers are also replacing the standard backsheet with a second layer of heat-strengthened glass that better protects solar panels from the elements, leading to longer life and better performance. These dual-glass panels provide better performance in extreme heat, humidity and other harsh conditions. The second sheet of glass also makes panels highly resistant to fire, whereas backsheet material is fairly prone to fire risk. Moreover, standard silicon panels’ cells can suffer from microcracks and blacklines due to the lack of protection provided by plastic backsheets.
As the industry matures, panel manufacturers are focused on developing panels that make solar more competitive with conventional energy sources. his is being accomplished by lowering panel costs, installation costs and improving the efficiency of the product so more energy is produced per unit of cost. There is still significant low-hanging fruit for cost reduction of PV systems, beyond just increasing cell and panel efficiency. As these innovations progress and bring the cost of going solar to par with traditional energy sources, the solar will become a viable and preferred energy source in more and more locations around the world.