| By :
Aaron Dicks
Copyright (c) 2010 Aaron Dicks Systems with fitted sensors, with movement capability can ensure energy yield increases are much higher than that of fixed PV systems. The yield from tracked PV Systems can be 50 per cent higher than any fixed horizontal system due to the adjusted angle of incidence during summer months, and up to 300% higher in winter months. However, the majority of energy gains when using tracked photovoltaic systems are those during the summer. Total energy yield is higher during summer months than during winter months, not only is this due to the angle of the earth's surface and the sun, but also due to a higher proportion of cloudy days being during the winter. There is a variety of PV systems that are capable of tracking the sun. The main differential component is whether the system is single or dual-axis. Single-axis tracking is not as complex as dual-axis tracking and requires less technology. Dual axis tracking moves across two axes to follow the sun's incoming radiation at an optimum alignment, so always brings higher yields. Because of the technological differences between the two technologies, dual-axis tracking costs are higher than single axis tracking. In most situations, single-axis tracking is sufficient for achieving a good return on investment. Tracker systems follow either daily or annual paths - annual path tracking is the easiest to implement, as it involves adjusting the tilt angle of the array at relatively large intervals of time. This may need to be carried out manually depending on the particular array. In Europe, dual-axis tracking systems can provide an annual yield 30 per cent higher than a comparative fixed system(Zentrum fur Sonnenenergie- und Wasserstoff-Forschung), and a single axis tracking system can provide yields with gains 20 per cent over a similar fixed install. The costs involved with installing an advanced tracking system over a traditional fixed system are that they require a strong mounting system that can withstand storm conditions and that they must use either an electric motor or a thermo-hydraulic control system. If a tracking system fails, the Photovoltaic modules may be left positioned in a position where high yield from the suns radiation is impossible. If the problem remains unfixed, the array string's generation output will remain at a lower level of output. Historically, these systems yield would not match up to the return of investment expected for the higher start-up costs of a system. In regions where there is a beneficial feed-in tariff, single axis tracker systems can provide the additional yield needed to make the return on investment appealing to commercial land owners. Building integrated PV is a much preferred option within the United Kingdom - utilising wall and roof space to provide clean green energy for the building to offset carbon emissions. The feed-in tariff in the UK currently stands at 41.3 pence per kilowatt hour generated.
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