Kathe Hermstad, m. arch,

SINTEF Civil and Environmental Engineering, department of architecture and building technology, 7465 Trondheim, Norway, Web: www. sintef. no Phone: (+47) 40454620

Introduction:

Smartbuild is a six-year strategic research program performed in collaboration by SINTEF and the Norwegian University of Science and Technology, NTNU. This paper is based on the work of sub-task 2.4 — "Building Integrated Photovoltaics". The intention of this sub-task is to strengthen Norwegian research, education, and industry within the BIPV field. The long term aim of the project is developing new BIPV concepts, both for new use of present product lines and for development of new products.

The paper summarizes the first phase of the project. An analysis of trends in office building design and implications for photovoltaics is followed by a presentation of the office building “Pynten” in Oslo. The building forms the platform for evaluating different PV concepts.

Office building design trends and photovoltaics

Successful green buildings have relatively low life-cycle costs, provide healthy, safe, and inspiring work environments and communicate a valuable philosophy. Many companies insist on and pay well for facilities in such buildings, which give the building owners an advantage in the real estate market. Along with all its technological and environmental advantages, photovoltaics (PV) can be one of the most expressive technological solutions in terms of flaunting an environmentally conscious building profile, an asset that helps promoting the buildings to prospective tenants.

In the increasingly competitive and global markets, companies spend much effort on their image. The modern, holistic company profile is comprised by its physical, aesthetical, and cultural capital. The two latter are becoming progressively more important, as they can transform and relate to the market with more ease, and thus better communicate a company’s values. Many companies change locations on a regular basis, as an incentive for corporate culture change or as a part of restructuring. Thus they need a range of facilities that support their environmental profile or technology that can transform the physical profile of new locations with a poor environmental profile. This nomadic corporate culture is likely to embrace technology for retrofitting that has a relatively short payback time or can be transferred to new locations/sold as a second hand product. PV systems still have relatively long payback periods, but increasing production is lowering prices. Simpler systems for retrofitting, with "click-on” features and long lifetimes, make them feasible for moving or reselling.

Today’s companies need facilities that sustain their core activities, and support activities are increasingly outsourced to make the companies more focused and agile.

The shift of companies from building owner to building user is a step in this direction and has given new structures in office buildings in terms of technical infrastructure and the service organisation. Micro-urbanism, with building sectors referred to as neighbourhoods, streets, squares, and public facilities, is one example of the new internal structuring. The common areas are often used to express a building’s “green” profile, and larger installations often appear here. This separation between “public” and “private” is often
elaborated in the fagade. The openness of the public domain is often articulated with large glass surfaces, which again create a need for shading. Photovoltaics (PV) are often used as solar protection in arrays playing with daylight through shadow patterns, colour, and materiality. Although PV is presently a relatively expensive material, its value can extend beyond power production. Building integration and symbiosis with building service is lowering the excessive cost of PV to more acceptable levels. The perception of what building integration comprises, widens constantly.

Although the aesthetics of architecture is interpreted in relation to its use, the exterior and interior of large buildings have complex relations and, to some extent, become separate projects. The built structure and underlying service facilities is designed to adapt to its content and not vice versa, as work methods, users, owners, and the exterior environment is constantly changing. A building may be redefined and restructured several times during its lifetime and modern commercial rental buildings usually maintain their initial internal structure for only 5-10 years. The concept of honest facades thus becomes somewhat hollow in a lifetime perspective. This makes way for new structures that incorporate change as an elementary function and aesthetical ideal. Interactivity, mobility, and layers along with new materials and technology meet in future facades. pV is a natural part of this development, and the material still faces many unexplored conceptual opportunities.

Space planning has evolved from the rigid structural grids and the transformable "typical plan” to modules of complex geometry, often in three dimensions, that create unexpected interior and exterior environments. The move towards more chaotic space structures evolves from aspirations to stimulate creativity and knowledge flow in the organisation through random social interaction. Large structures are necessarily depending on modularity, and the new, more complex modules can introduce natural breaks between work zones for these activities. This can also introduce new aesthetical themes for facades and interiors, as different demands in terms of fagade integrated service for the interiors form new design parameters. The hype towards complex module geometry and three­dimensional surfaces offer many challenges to the PV-industry that mainly produce flat, rectangular modules.

Modern office building envelopes have tasks beyond climatic protection, and provide an increasing number of services to the interior climate. The active envelope changes its properties according to interior preferences and exterior conditions. It supplies fresh air, regulates temperature and lighting, and generates electricity. This organic understanding of the facades is supported by technology increasingly inspired by nature. With a holistic understanding of the service facilities, the bi-products earlier regarded as problems become valuable resources. An example is the excess heat from PV that should be transported away to maintain high power production in the cells.

Safety is becoming increasingly important in office and industry facilities, and buildings are becoming more and more automated with electronic security measures. The buildings are becoming more and more dependant of a minimum access to power to maintain its basic safety operations. The attention on security of basic energy supply is increased through a number of recent electric blackouts in large urban areas several places in the world. In this context, PV stands out as an elegant solution to sustaining security measures.

The presently most successful PV products for office buildings are modules for roof mounting and PV integrated in glazing for atriums, skylights and in double facades. PV has often been given tasks of shading and of enhancing natural air flows through their temperature accumulation. PV has also been successfully integrated in walls, although this
is demanding in the modern more fragmented expressions of office buildings. Some fixed solar shading devices with PV integrated in glazing have become popular for public zones, and some of these products offer certain mobility within the module for better adjustment to the sun. The first mobile elements are out in the market now, and integration with control systems may offer a new control dimension to the work place and dynamical facades. The mobile elements can further become part of the heating and ventilation system and integrate intelligent fagade structures further. In the future, new technology like organic PV opens for a number of new product opportunities.