Lyon Infrastructure

S CHOICE BETWEEN THE TWO GREAT CLASSES OF PV TECHNOLOGIES

One of the ways of integrating photovoltaics into buildings is to incorporate it into facades, that is, onto walls or windows, which usually means – unless particular geometries such as “venetian blinds” or “sawtooth” are adopted – installation of modules vertically , and therefore with reduced access to solar radiation, which is all the more effective in producing energy the more it hits the modules perpendicular to their surface. Therefore, the use on facades is partly justified by aesthetic reasons and partly by the possibility of exploiting large surfaces, which partly compensates for the lower efficiency compared to the roof in energy production. The use of photovoltaics in skylights or for the construction of entire glass roofs (e.g. of gyms, shopping centers, etc.), on the other hand, represents above all an intelligent way of combining an economical (as efficient) use of photovoltaic technology with the possibility of creating structures with a fascinating designnte.

The most suitable photovoltaic technologies, from the point of view of the efficiency / price ratio, for integration into a building depend on numerous factors, starting with the location and orientation of the building. On a facade, for example, the expensive crystalline modules(on a traditional opaque support or embedded in glass) may be preferable to other solutions only if the building in question has a southern orientation (more or less 45 ° ). If the building does not have such an orientation, their use should be limited to the roof. The thin film, made with silicon cells or based on other semiconductor materials – including the innovative “organic cells” – is a technology that allows you to maximize the efficiency / price ratio in many situations: it is ideal for exploiting large surfaces, such as facades and roofs of commercial or industrial buildings, as well as for hot climates, where the performance of crystalline silicon declines by 5% every 10 ° of temperature above 25 ° C.

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HOW AN INTEGRATED PV SYSTEM IS MADE IN A BUILDING

A complete system includes the following components: (1) photovoltaic modules , which can be crystalline or thin film , transparent, semi-transparent or opaque; (2) an inverter , which converts the direct current (DC) supplied by the modules into alternating current, or AC; (3) all support and mounting hardware, wiring, fuses, etc. the classic “networked” type (used to take advantage of state incentives and that immense natural accumulator that is the national electricity grid), but is an isolated system ( stand-alone), there are the following additional components: (4) a battery pack to store the electricity produced; (5) a charge controller , which regulates the energy that enters and leaves the batteries; (6) a possible “backup” generator system – such as eg. a diesel generator – which starts automatically when the main one cannot operate due to the absence of the sun or is unable to meet the energy demand.

Designing a building that integrates a photovoltaic system requires taking into account various factors, including: the use of the building, its location and orientation; the needs and objectives to be achieved in terms of aesthetics, energy, heat, lighting; the peculiarities and indications of the various photovoltaic technologies and related materials, etc. In parallel, other possible measures to improve energy efficiency must be considered

of the building, of which the photovoltaic electricity generation system is only one component. Usually, a photovoltaic system is sized on the basis of objective constraints, such as eg. the space available and the budget. However, in the case of integrated photovoltaics in new buildings, it is not necessary to look at the initial cost of the system but at the “real” one, which takes into account both the savings in construction materials and workforce and the higher value of the building deriving from the electricity produced in the life cycle of the plant itself.

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