Photovoltaic SystemsIn order to benefit from the electricity generated in solar modules, either by consuming it instantly on the premises or by feeding it into the grid, the module must be wired up with a few other electrical components. The exact combination depends on the size of the installation and whether it is connected to the grid or not. |
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Grid-connected, small-scale installationInverterIn a small-scale, most likely residential, installation, the pv- module has to be connected to an inverter. The purpose of an inverter is to
In small-scale installations the AC output from the inverter is a 2-phase AC, which is common in households. The inverter output can be connected to the grid via a meter. Maximum Power Point Tracker (MPP)As described, the mpp- tracker ensures that the module operates at its maximum power point at all times. Most inverters also include the maxium power point tracker (mpp).Where crystalline modules are used, partial shading of the entire roof (for instance caused by a tree or a chimney), the module will only generate as much current as its weakest string. In this instance, each string should have its own mpp- tracker to boos efficiency of the system. Surge ProtectionSome inverters may also provide surge protection. However, this may not be enough if the wires between the solar module and the inverter are longer than 10m, when additional surge protection devices ought to be considered. |
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Grid-connected, large-scale installation
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Off-grid, hybrid renewable systemWhy Hybrid?In a hybride system, several renewable energy sources are used in tandem. By doing so, the variability of a single source (i.e. wind or sun beam) can be softened. This is especially true in the Northern hemisphere where there is evidence of a inverse correlation between wind and sunshine. That is, on days with high wind speeds, there is probably less sunshine and vice versa.Why Off-grid?On small islands or in other remote areas, a grid connection is often not feasible. To avoid wasting surplus energy from the renewable sources (which would otherwise be fed back to the grid), a battery may be used for storage. In times when energy demand exceeds the supply from renewable energy sources, the battery may be discharged. As a last resort a diesel engine must be employed if supply is to be guaranteed.A controller should be utilised to balance charging / discharging of the battery and starting / stopping of the diesel engine. Despite the complexity of these systems, they can be economically viable for remote areas where diesel fuel is very costly due to high transport costs. The sizes of each component however, need to be considered very carefully. |