Building integrated concentrating solar systems - Solar Energy Sciences and Engineering Applications - page 547

function (BASE) in a manner such that their visual impact is kept low and poor inte-
gration is minimized. This constrains the placement to the roof top (flat or inclined).
Within the roof integration, the tilted configuration maximizes annual efficiency; how-
ever, overheating problems may occur in the warmest seasons. In these cases proper
system dimensioning must be performed taking into account both the heat demand
and overheating possibilities.
BIST systems on the façade, at present, are practically non-existent because the
main use of thermal collectors to date has been to provide heat, with no or minimum
involvement in the building environment and envelope. In this way, installation of the
solar panel in the most visible part of the building requires more attention than simply
to cover a technical function. At this point a balance becomes necessary, sometimes
pitting architecture and engineering against each other - in other words, a conflict
between efficiency and aesthetics.
To state how to increase the architectural quality of BIST, a clear definition of a
successful integration must be established. In this sense, Munari Probst and Roecker
(2007) conducted a survey of how architects and engineers perceive integration quality.
The authors inferred a set of guidelines synthesizing the criteria highlighted in the
survey:

1 The use of the solar energy system as a construction element (facade cladding, roof

covering, etc.) facilitates the work of integration design. Certainly, the “logic'' of
the building design is easier to follow when the architect has to balance fewer
elements which fulfil more functions.

2 The position as well as the dimensions of the collector field should be evaluated

by considering the building as a whole (important issues are: energy production
goals, formal integration needs, etc). Another option is the use of dummy elements
(non-active elements with a similar appearance).

3 The choice of colours and materials for the system should match with colours and

materials characterizing building and context. The initial choice of technology is
fundamental because it imposes the material of the external-visible-system layer
(glass, metal, plastic, etc). In the frame of the chosen technology, material treat-
ments (surface colour, texture) offered by the various available products can be
considered.

4 Module size and shape should be chosen by taking into consideration building and

facade/roof composition grids (or vice versa). The proposed jointing types should
also be considered while choosing the product (different jointing types differently
underline the modular grid of the system in relation to the building).

The criteria and guidelines imply that the designer should have knowledge of the
existing technologies and available products in order to make the right choice (of prod-
ucts and technologies) to realize a successful building integration. Nevertheless, the
above-mentioned integration requirements are difficult to achieve because the currently
available collectors on the market have been developed with insufficient awareness of
building integration aspects (Munari Probst et al., 2005). In order to properly design
collectors oriented to their integration in buildings, a methodology has been defined by
Munari Probst and Roecker (2007). Figure 17.1.1 shows the different steps involved
in designing the collector: integration, efficiency, users' preferences and feasibility - all
need to be taken into account to cover all points of view.