Simulation and design of an innovative system with optimal combination of renewable energy sources to cover heating, cooling and domestic hot water demand in buildings

In recent years, due to the rapid development of human activities, energy demand and consumption has been increasing steadily. Reduction of fossil fuel reserves combined with environmental pollution highlights the significance of this problem and makes renewable energy sources more important than ever. As the consumption of tertiary building sector occupies a very important part of the overall energy demand, systems that combine renewable sources are among the most promising solutions for this issue. In this respect, coupling of Photovoltaic-thermal (PV/T) collectors with a heat pump configuration is a modern alternative that replaces traditional heating means such as oil boilers.

In this diploma thesis, an innovative renewable-energy based system is designed and examined for covering heating, cooling and domestic hot water demand in a small complex of apartments located in Athens, Greece. This system follows an alternative configuration of a dual stage multisource (air and water) heat pump combined with PV/T collectors. The selection of heat pump arrangement results after comparing a big variety of possible configurations witch are thermodynamically modeled in EES (Engineering Equation Solver). The final choice of heat pump is optimized as far as some parameters are concerned and is dimensioned according to the requirements of the installation. The energy produced by the collectors can be either used directly for covering thermal needs or stored in a buffer tank for supplying the heat pump with low temperature heat. By doing so, all solar radiation is exploitable and the heat pump operates with an elevated performance for a longer period during the day. Moreover, the way that solar heat is exploited by the system as well as the selection of input source (water or air) in heat pump’s evaporator are optimization objectives during the computational simulation. The same configuration is also used in summer, when cooling is required by reversing heat pump’s cycle. This system, is further developed by introducing a suitable geothermal heat exchanger which adds an additional renewable energy source, increasing significantly the installation’s performance. Finally, the aim of this examined system is to meet 100% of all thermal needs with an optimal combination of renewable sources and minimizing electricity consumption.

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