Facade solar thermal collector represents a new element in building design and also in old buildings retrofit. Facade solar system performance and its interaction with the building were investigated through the computer simulation. System and building were processed together, collector absorber was thermally coupled to building envelope.

The simulation has shown that facade solar collector should have area increased by approx. 30 % to achieve the same solar fraction (usually 60 %) as conventional roof solar collector with 45° slope. Further increase in solar fraction above 70 % leads to required area comparable with roof collectors, but with less stagnation periods and lower amount of energy which cannot be utilized than with roof collectors.

Building behaviour is not strongly affected by facade collector when sufficient insulation layer is present. Facade collectors in investigated configuration (panel, brick wall) slightly improve the thermal protection of building in winter season, but for higher thermal insulation levels the heat gains are negligible. Application of facade solar collector affects the indoor comfort in building in reasonable range. Inside temperatures increase not higher than 1 K in all configurations (wall type, facade collector area), integrated comfort parameter PPD has even better values for higher facade collector area applied. This results form the fact that facade collector operation partially helps in cooling the facade.

Heat from absorber is efficiently removed during the day extremes and collector stagnation is at low level for facade collector. The gains through window effect the inside temperature variation much more than facade collector.

Absorber temperature affects particularly the first layer in the envelope construction, next layers are at moderate temperatures. Temperature in the wall varies according to indoor conditions and practically is not affected by facade collector. The only risk potential is concentrated in the insulation layer adjacent to collector.

Further research in the area of solar collectors integrated directly into facade should be orientated to building processes — topics as water vapour transport, thermal bridges, absorber mounting etc should be satisfactorily solved to spread the technology.

Interesting area of facade collector application is in the solar systems for combined DHW and space heating (combi-systems). In these systems, area of solar collector field is higher and summer gains can cause problems, if no summer “heat consumer” is available (swimming pool, dryer, etc). Facade integrated collector could represent a very efficient solution.

References

[1] Matuska, T.: Transparent thermal insulation and their use in solar applications. PhD. thesis, Czech Technical University. Prague 2003.

[2] Matuska, T., Sourek, B.: Fagade solar collectors. Conference on Dynamic Analysis and Modelling Techniques for Energy in Buildings (DAME-BC). Ispra, 2003.

[3] McAdams, W. H.: Heat Transmission, 3rd edition. McGraw-Hill, New York. pp. 249. 1954.

[4] Sparrow, E. M., Tien, K. K.: Forced convection at an inclined and yawed square plate — application to solar collectors. ASME Journal of Heat Transfer, Vol. 99, 1977, pp. 507­512.

[5] Sparrow, E. M., Lau, S. C.: Effect of adiabatic co-planar extension surfaces on wind — related solar collector heat transfer coefficients. ASME Journal of Heat Transfer, Vol. 103, 1981, pp. 268-271.

[6] TRNSYS v.15 Manual, Solar Energy Laboratory, University of Wisconsin, 2000.

[7] Rockendorf, G., Janssen, S.: Facade integrated solar collectors. Solar World Congress, Jerusalem 1999.