Eksergoekonomska optimizacija sistema daljinskega hlajenja

V doktorskem delu so predstavljeni rezultati teoretične in eksperimentalne analize sistema daljinskega hlajenja. Razvili smo splošen eksergoekonomski model, ki omogoča optimalno izbiro komponent pri zasnovi sistema daljinskega hlajenja ter možnost optimizacije delovanja obstoječih sistemov daljinskega hlajenja. Delo obravnava več načinov proizvodnje hladu: z električno gnanimi kompresorskimi hladilniki ter z eno- ali dvostopenjskimi absorpcijskimi hladilniki, ki so gnani s toploto. Ciljna funkcija optimizacije je minimalni strošek rabe eksergije. Model je zgrajen na osnovi eksergoekonomskega pristopa, ki vključuje celotno verigo sistema daljinskega hlajenja, od proizvodnje hladu, distribucije, do končne rabe. Energijski produkt, torej hlad, je vrednoten glede na potrebno vloženo eksergijo ob upoštevanju minimalnih investicijskih, obratovalnih in vzdrževalnih stroškov proizvodnje in distribucije hladu. Opravljena je analiza vpliva pomembnejših parametrov zasnove in obratovanja sistema daljinskega hlajenja na eksergoekonomske kriterije vrednotenja distribucije hladu. Model je bil uporabljen na že obstoječem sistemu daljinskega hlajenja, kjer je stanje distribucijske mreže eksperimentalno določeno na podlagi metode prekinjenega obratovanja cevovoda. Rezultati analiz kažejo, da sistemi daljinskega hlajenja ob zadostni gostoti potreb po hladu, ustrezni zasnovi in optimizaciji obratovalnih parametrov ter pri nizkih cenah električne energije in eksergije toplote, omogočajo dober energijski izkoristek in nizke stroške ter posledično nizke cene končnega produkta. Kadar ti pogoji niso izpolnjeni, se njihove prednosti hitro zmanjšajo. In this thesis the results of theoretical and experimental analysis of a district cooling system are presented. The general exergoeconomic model of a district cooling system was developed. This model enables the optimal selection of components in the design of a district cooling system as well as the optimization of an existing district cooling system. Different types of the cold production were analysed in this work: cold production by electrically driven compressor chillers and one- or two-stage heat driven absorption chillers, respectively. The target function of the exergoeconomic optimization is the minimum cost of the exergy of cold. The model is based on the exergoeconomic approach where the entire chain of a district cooling system, cold production, distribution and consumption of cold, is included. The energy product, i.e. cold, is validated according to the input exergy, considering the minimum investment, operating and maintenance costs of production, distribution and consumption of cold. The effect of the key design and operation parameters of a district cooling system on the exergoeconomic evaluation criteria of cold supply was evaluated. The model was tested on the existing district cooling system. There, the parameters of the distribution network have been experimentally determined. This was performed by interrupting the operation of a district cooling system and observing the temperature increase in the pipeline due the heat gains. This work reveals, that for district cooling systems with a relatively high cooling demand, an appropriate system design and the optimization, as well as the low prices of electricity and heat, enable good utilization and low price of final product. If these conditions are not fulfilled, the advantages of district cooling systems are reduced.