Simulation of operation of high temperature latent heat storage

Primjena spremnika latentne topline u elektranama s koncentriranim sunčevim zračenjem osigurava visoku gustoću pohranjene energije. S druge strane, niska toplinska provodnost solarnih soli, kao medija pohrane topline, predstavlja svojevrstan tehnološki nedostatak. Jedan od načina rješavanja tog problema je smještanje spomenutih soli u kapsule raznih oblika i veličina. U ovome radu, korištenjem računalnog paketa Matlab, napravljen je pojednostavljeni model solarne termoelektrane snage 50 MW. U sklopu njega matematički je modeliran sustav s 4 paralelna visoko-temperaturna spremnika latentne topline sa sferičnim kapsulama. Unutrašnjost spremnika i kapsula prostorno je diskretizirana, pri čemu je u obzir uzet utjecaj promjene volumena šupljine u samim kapsulama. Za medij fazne pretvorbe razmatrani su kalijev nitrat (KNO3) i kalijev hidroksid (KOH) te njihova kombinacija. Iterativnim metodama određen je optimalni volumen spremnika i dana je usporedba kapsula vanjskog promjera 1, 3 i 5 cm. Prikazani su međusobni utjecaji dinamičkih značajki komponenata postrojenja, te su na temelju istih izneseni zaključci.The application of latent heat thermal energy storage in concentrated solar power plants provides a stored energy of a high density. On the other hand, the low thermal conductivity of solar salts as a storage medium is their main technological disadvantage. One way to solve this problem is by placing aforementioned salts in the capsules of various shapes and sizes. In this paper, a simplified model of a 50 MW solar thermal power plant was constructed using a Matlab software. Within said model, a system of 4 parallel high-temperature latent heat storage tanks with spherical capsules was modeled mathematically. The tank and capsules are spatially discretized, taking into account the influence of the volumetric change of capsule internal void. Potassium nitrate (KNO3), potassium hydroxide (KOH) and their combination were considered for the phase change material. The optimal volume of the tank was determined by iterative methods and a comparison of capsules with an outer diameter of 1, 3 and 5 cm was given. The conclusions were derived from the interactions of the dynamic performance within the plant components