ENERGYHARVESTING
The evolution of PV solar power architectures
One reason rooftop PV solar installations are underperforming in terms of energy harvesting is because conventional architectures for DC strings are not as efficient as required. Paul Engle, CEO of Enecsys discusses a potential solution that could improve efficiency and drive an increased adoption of solar electric technology.
electricity, typically with a peak output up to 250 Watts. With suitable control circuits, they can be used to charge a battery – which also generates DC, or to power DC devices. However, by far the largest market for PV solar installations is so-called “grid connect” applications. Here, the DC generated by solar modules is converted to alternating current (AC) for direct connection to the AC power grid. When solar power is not generated, for instance at night, the grid provides power for the user. When the solar installation is generating power, the user can power electrical appliances with it and any excess is sold back to the power company that supplies the grid.
P
Conventional PV solar architecture
In conventional PV solar installations, modules are connected in series, like a daisy chain, to form a “string”. A central inverter converts the high voltage DC output of the string to AC for connection to the grid. Figure 1 shows the arrangement.
Installation is complex and expensive for these conventional systems, requiring specialist skills and safety procedures due to the high DC voltages and currents that are developed. These can reach up to 900V at 5A – lethal if touched. In systems using DC strings, maximum energy harvesting occurs only when every module is matched exactly for technical performance and the same amount of solar radiation reaches each solar cell in every
hotovoltaic modules, or panels, produce direct current (DC)
module. In real world conditions these requirements are often not met and the system performs below its potential, often dramatically so.
Shading from any source such as tree branches or even something as small as an antenna or vent pipe can dramatically reduce the energy produced from string systems.
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www.solar-pv-management.com Issue II 2010
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