Feature: Renewable


Dummy load resistors transfer excess energy into heat and release it into environment to prevent the solar panels from overloading


become increasingly popular, which use tracking systems to tilt and shiſt the angle of the panel as the day goes by, to best match the Sun’s position. Te tracking systems can be used with ground-mounted solar panels, such as solar farms for large-scale commercial or utility projects. Panel movements can be pre-programmed based on astronomic predictions, or they can use solar radiation sensors to detect and react to the Sun’s position in real time. Te tracking system can be single- or


dual-axis. Single-axis systems move the panels through only one plane, east to west to track sun rise and set, or from north to south to account for seasonal variations in the Sun’s angle. Dual-axis systems can move in more than one plane, making them bidirectional. Additionally, wind turbines are much


larger nowadays. One example is the 9.6MW turbine from Danish producer, MHI Vestas, which can power more than 8,000 homes. Power storage is increasingly possible, and many companies have partnered with battery producers to store extra power for later use.


Keeping technology turning Although embracing renewables is great for the environment, it does face some challenges. Each source of renewable energy is dependent on the environment around it, meaning that production can suddenly soar and require the system to be capable of dealing with a sudden influx of power. For example, wind turbines are generally connected to the distribution network through step-up transformers. When these are energised, large inrush currents occur, causing overvoltages on the distribution network, likely damaging equipment upstream. Issues like these can be remedied by


using technologies such as pre-insertion resistors (PIRs) in the circuits. PIRs, like


The water-cooled Cressall EV2 is seen as an environmentally-friendly option


those offered by Cressall Resistors, are a three-phase resistor, insulated for the full system voltage, typically 33kV, and fitted with isolating devices, as required. Teir high thermal mass allows them to absorb energy from large inrushes whilst still being compact enough to fit efficiently in a transformer substation. Power problems also extend to solar


energy. For example, when installing new solar panels or disconnecting existing installations from the grid for maintenance, the panels continue generating electricity. As a result, discharging this excess energy must be prioritised to prevent damage occurring to the solar panel system. Resistors play a crucial role in safely dispersing this excess energy. Dummy load resistors convert the


excess energy into heat and release it into the environment to prevent the solar panel from overloading. Te solar tracking systems described here also require braking systems to


ensure they are at the correct angle. For this reason Cressall also provides dynamic braking systems that can help maintain that the panels stop moving when required, by dissipating excess power generated by the decelerating motor. Tis ensures the panel doesn’t overshoot its movement and land in a sub-optimal orientation to the Sun.


Pause from burning fuels Te UK’s current coal-free reign may not last forever – at least not yet – but the pause from burning fossil fuels certainly marks a brighter future. As renewable resources form an increasing part of our energy mix, it will be ever more essential to ensure that the technologies that power them and those that manage the power support the nation’s net zero goal. Te growth in the efficiency of these


technologies means that adopting renewables is becoming more achievable than ever. As these technologies develop, so too will the resistors that integrate into the current power network.


www.electronicsworld.co.uk February 2021 33


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