BUILDING INTEGRATED PV

Building Integrated Photovoltaics (BIPV) is one of the fastest growing segments of the photovoltaic industry. When PV panels are integrated into a building during construction, the incremental costs of the system are reduced while the building owner is provided with tangible, cost-saving advantages such as significantly reduced demand for peak electricity, reduced transmission losses and the ability of back-up power.

Solar modules are made of a single glass sheet. These sheets can be produced in several colours enabling the panels to look like an integral part of a building's exterior. In addition, translucent or patterned panels which offer an aesthetic effect. Finally a new generation of transparent modules can be offered which can be used as electricity generating windows.

In the developing world, BIPV installations are the most desirable. This is because BIPV doesn't use any extra space and because the material savings from replacing ordinary construction material with BIPV substantially reduces the cost of the installed PV system and thus the cost of PV electricity.

BIPV best demonstrates the multi-functionality of PV. BIPV gives buildings the opportunity to become more self-sufficient by allowing them to generate their own electricity rather than merely consume energy. PV integrated into a building can, as a second function, provide shade, insulation and help to control the interior climate. There is no issue in terms of image as the panels are considerably attractive features.

Thin-film PV modules are more suitable for BIPV. Crystalline silicon modules not only lack the aesthetic and physical properties required for BIPV installations but their significantly higher cost per area makes them uneconomical for project managers. The financial incentives offered by many governments, low incremental costs and the highly desirable return on investment is creating a surge in demand for BIPV products.

In the case of facade or roof systems the photovoltaic system can be added to the building after it was built. These low powered systems of up to some 10 Kw are usually integrated into the south facade. Facade integrated photovoltaic systems could consist of different transparent module types, such as crystalline and micro-perforated amorphous transparent modules. In such case a part of natural light is transferred into the building through the modules.

Solar cells are available in different colours; therefore, there is no limitation for imagination of the architect or the designer. We can say that such constructed buildings give the term architecture a completely new meaning. Roof-integrated photovoltaic systems are integrated into the roof; the roof is covered with transparent photovoltaic modules, or they are added to the roof later. Such systems are added to a flat roof or on a tilted roof usually only if the building is small. It is possible to use tiles, which integrate solar cells.

Photovoltaic systems could be used for shadowing, where photovoltaic modules serve as Venetian blinders. In some of such cases photovoltaic modules tilt angle could be adjusted manually or automatically allowing for shadowing the building and/or photovoltaic module efficiency optimization. Such systems are also known as "Shadow-Voltaic" systems. The best results and efficiency can be reached with systems that are tightly integrated into the passive solar buildings. However, the use of active solar systems is an additional possibility. This is where the modules are partially transmitting allowing natural light to penetrate the building. Undoubtedly, such systems challenge even the best of architects.

High level of expertise is required for successful BIPV systems planning, not only in regards to architecture, but also to civil and photovoltaic engineering. The projects realised in the past show that successful BIPV systems designing is based heavily on technical experience and knowledge.