Dynamic analysis of solar hot water system operation

Provedena je analiza podsustava proizvodnje toplinske energije referentne jednoobiteljske kuće na području grada Zagreba pri dvije razine potrebne godišnje toplinske energije za grijanje ( 70 i 20 kWh/m2). U tu svrhu razvijen je u programskom paketu TRNSYS dinamički model analiziranog sustava. Dodatno, ispitana su tri proračuna različitih kompleksnosti razvijena temeljem normi HRN EN 15316-5:2017 i HRN EN 15316-4-3:2017. Pri korištenim referentnim parametrima sustava, količina prikupljene sunčeve energije približno je jednaka kod obje razine toplinskog opterećenja, a ostatak potrebne toplinske energije daje pomoćni grijač. Odstupanja rezultata satne metode sa stratifikacijom temperature u spremniku minimalna su u odnosu na rezultate simulacije dinamičkim modelom zbog čega ona može biti prikladna zamjena za dinamički model. Odstupanja mjesečne i pojednostavljene satne metode nešto su veća pri čemu je mjesečna metoda zbog jednostavnosti uporabe prikladna za grube procjene rada sustava na godišnjoj razini. Dnevna raspodjela potrošnje PTV-a ima zanemariv utjecaj na prikupljenu toplinsku energiju solarnog sustava i pomoćnog grijača, dok porast potrebne energije za PTV dovodi do porasta prikupljene sunčeve energije, ali i energije pomoćnog grijača. Povećanje koeficijenta izmjenjivača topline solarnog kruga i smanjenje postavne temperature i regulacijskog raspona pomoćnog grijača uzrokuje povećanje učinkovitosti solarnog sustava i smanjenje potrebne energije pomoćnog grijača, dok povećanje volumena spremnika uzrokuje rast učinkovitosti solarnog sustava, ali i povećane potrebe za energijom pomoćnog grijača zbog većih toplinskih gubitaka spremnika.The analysis of a heat generation subsystem in a benchmark single family dwelling located in Zagreb area was conducted at two levels of annual space heating requirements (70 and 20 kWh/m2). For this purpose, a dynamic system model was developed in the TRNSYS software. Additionally, three different calculation procedures based on European standards HRN EN 15316-5:2017 and HRN EN 15316-4-3:2017 were examined. For the reference system parameters, accumulated solar energy at both levels of heat load were approximately equal, while the difference of required energy was submitted by the back-up heater. Hourly calculation method with a stratified storage tank can be a suitable replacement for the dynamic system model, as deviations of its results were insignificant compared to dynamic model results. Deviations of simplified hourly and monthly methods were comparatively larger, although due to its simplicity of use, monthly method results can be used as a rough estimate of annual system performance. Daily DHW consumption profile had negligible effect on accumulated solar and back-up energy, while the rise of annual DHW energy requirements was compensated by both the solar collector and back-up heater additional energy contribution. Decrease of back-up heater setpoint temperature and control temperature range, as well as increase of a solar loop heat exchanger coefficient caused an increase of solar system efficiency and decrease of required back-up energy, while the increase of a storage tank volume caused an increase of both the solar system efficiency and required back-up energy due to the bigger storage tank heat losses