Efficiency of a solar collector system for the public building depending on its location

Abstract

Due to a technologic progress, a growth in the renewable energy markets including a high number of manufactures coming to being, the Renewable Energy Sources (RES) are both a tool for mitigating climate changes and investments that can provide direct economic profits and reduce a political or economic dependence resulting from import of fossil fuels. One of the many key solutions toward fulfilling the global increasing demand for energy and reduction of CO₂ emissions is applying solar technologies. This paper presents the results of the analysis conducted for a small public office building located in Bialystok (Poland), where solar collectors were considered as the RES for domestic hot water (DHW) system, on the understanding that existing oil boiler would be an additional source. Low values of recommended water consumption in office buildings resulted in a low energy demand. However, concerning a potential of all office governmental buildings in Poland, it would be possible to reduce CO₂ emission by 17,248 tonnes. In the comprehensive analysis, the same building in two more locations (Cordoba (Spain) and Kaunas (Lithuania)) was considered using simulation tools delivered within the framework of VIPSKILLS project as well as EnegyPlus software. The results allow to compare the mean monthly efficiency of systems or number of collectors necessary to deliver similar amount of solar energy.

Keywords: Beam radiation; Efficiency; Simulation; Solar collectors; Renewable energy; DHW; Solar system.

Fig. 1

Analyzed office building (photo by D.A.Krawczyk)

Fig. 2

Share of energy sources for DHW in governmental buildings in Poland (source: own elaboration based on CSES GUS 2015)

Fig. 3

Changes of network water temperature during a year in Cordoba, Bialystok, and Kaunas (source: own elaboration)

Fig. 4

Scheme of the solar collector system: P_cw, pump; NWP_c, expansion vessel; C, collector; KO, boiler; SPW, water tank; Z_k, cut-off valve; Z_s, blow-off valve; ZB_c, safety valve; ZM, control valve; Od, air valve; T, thermometer (source: own elaboration)

Fig. 5

Solar heating system connection diagram set in calculations (source: own elaboration)

Fig. 6

Global monthly radiation on horizontal area in Bialystok, Cordoba, and Kaunas (source: own elaboration)

Fig. 7

Monthly energy demand for DHW in Bialystok, Cordoba, and Kaunas (source: own elaboration)

Fig. 8

Variation of energy gathered from the system with one solar collector (source: own elaboration)

Fig. 9

Contribution of beam and diffuse radiation in a total balance (source: own elaboration based on Krawczyk et al.

Fig. 10

Location of collectors on the roof (own elaboration)

Fig. 11

Variation of mean water tank temperature (source: own elaboration)

Fig. 12

Variation of energy demand gathered from auxiliary water tank (source: own elaboration)

Fig. 13

Mean total efficiency of the system (source: own elaboration)