Optical performance of vertical heliostat fields integrated in building façades for concentrating solar energy uses

• A novel configuration of vertical heliostat field for integration in building façades is described and optically assessed.
• Sizing and receiver location are optimized with regard to cosine, shadowing, blocking and interception factors.
• Influence of heliostat spacing and building typology are evaluated.
• Comparative assessment vertical versus horizontal heliostat fields is carried out.

One way for integrating concentrating solar energy systems based on central receiver technology in metropolitan areas consists of using building façades as frame for installing a heliostat reflector field that reflects radiation coming from the sun towards a common area where receiver is located. This work analyzes the optical performance of vertical solar field concept. It provides the effect of several geometric parameters such as receiver height, separation between heliostat edges, and different building typologies on the hourly and annual optical efficiency along the year including the contribution of different optical efficiency factors such as shadowing, blocking, cosine, and spillage.The optical efficiency of a vertical heliostat field was found to be mainly controlled by shadowing, cosine and spillage factors. The field reaches the maximum overall optical efficiency during spring and winter at noon time and the minimum ones during the summer season mainly due to shadowing factor. Results obtained for best configurations are comparable to those ones reached by traditional horizontal field arrangements, what supports the feasibility of the vertical heliostats field concept as a CSP building integrated facility.