COMMERCIAL FEATURE Active cooling for maximum yields A s beneficial as intense solar irradiation is for the photovoltaic industry, rising heat places heavier demands on central inverters used to produce clean current for millions of people in the hotter areas of the globe. They are not only required to work at the highest efficiency possible but are also expected to function reliably and faultlessly for the duration of operation. Here, cooling systems play an important role. There is a high risk – due to overheating – that sensitive components within the inverter will begin to behave differently leading to their eventual break- down. Anything from short-term failures to a complete system standstill bringing about high losses in yield are only some of the consequences faced by PV power plant operators and investors in photovoltaic projects. An intelligent and reliable cooling system is a decisive factor when it comes to investments in central inverters, especially in regions characterized by extreme ambient conditions. For example, in the varying climate regions of South Africa fine dust particles stirred up by sand storms place an additional burden, apart from the effects of the extremely high temperatures, on the central inverters in PV power plants. Millions of people in South Africa, for example, benefit from the PV energy source. 3 000 hours of sun per year and PV yields of up to 2 100 kilowatts per kilowatt of nominal plant power are achieved. Active cooling ‘An intelligent cooling concept is the key to optimal central inverter operation,’ says Hilton Hunkin, technical sales support engineer at SMA South Africa explains. ‘This requires, apart from the optimal spatial organization of all components, an efficient and properly dimensioned cooling system. Our Sunny Central inverters function at temperatures of up to 50 o C at nominal power – and full energy yield – based on the innovative cooling concept OptiCool ® and clever An intelligent cooling concept is the key to optimal central inverter operation spatial design. Even at temperatures of between 50 o C and 62 o C Sunny Central inverters continue to feed in but at the same time reduce the feed-in capacity according to temperature for self-protection. At 55 o C a Sunny Central continues to feed in 50% of its nominal power.’ In addition, Hunkin points out that SMA central inverters operating with optimal cooling can even yield a nominal power of 110% at temperatures of up to 25 o C during continuous operation. Fresh air is drawn in through the ventilation grids on the top front of the Sunny Central. The air passes the cooling-fan and the heat producing stacks and the sine wave filter choke stuck out in the air duct. The warm air leaves the inverter through a low- maintenance grid filter. 38 Sensitive temperature management Cooling requirements can be adjusted at any time through well-planned temperature management which reacts quickly and sensitively to temperature changes using numerous temperature sensors on the inside of the central inverter. This prevents the occurrence of failures and losses in yield. The inverter’s temperature management is therefore important for a smooth operation. Even at an efficiency of 98% some waste heat is ESI AFRICA ISSUE 3 2014