This document presents the energy analysis and simulation of central solar heating plants with seasonal storage (CSHPSS) designed for covering a part of residential heat demand required for SpaceHeating (SH) and Domestic Hot Water (DHW) oriented to reduce the consumption of fossil fuels.The main objectives of this thesis are to simulate and analyse in POLYSUN software a defined systemof CHSPSS already built in TRNSYS, in order to compare the results of both programs and to analyse and simulate these systems in different cities of Spain. In carrying out the objectives, some limitations have been found. Ones of these are the limitations of POLYSUN program, which have forced to reduce the number of housings.

The document starts with a revision of the state of art, in which it is shown the number of plants in Europe and specially, in Sweden and Spain observing the differences between them, for example, Spain has not any CSHPSS plant and Sweden was the first country of building one. In addition, in the theory section, it has been studied the main elements of these plants, such as different types of solar collectors and seasonal storages, and different simulation programs commercially available for the simulation and analysis of this type of plants. According to this, POLYSUN program is more intuitiveand user-friendly in some extent than TRNSYS, but its applications are more specific and more appropriate for small district heating systems.

Steps followed for obtaining the analysed system and main characteristics of it have been explained.These steps have been used to analyse the results of POLYSUN and to compare results betweenTRNSYS and POLYSUN. According to the obtained results, it can be remarked that the results obtained from POLYSUN are coherent, with the exception of Space Heating demand, which is calculated by the program and has a very important difference between the calculated value and the Space Heating demand introduced by the user. When comparing with TRNSYS, it has been observed that POLYSUN‘s boilers have a high thermal losses and low efficiency and POLYSUN’s pumps have high energy consumption and thermal losses.