Dynamic simulation and economic analysis of a combined solar thermal and pellet heating system for domestic hot water production in a traditional Hammam

Abstract The combination of solar heating systems and low emission biomass boilers provides the opportunity to produce domestic hot water in large applications (multi-family houses, public sector, hotels, schools, etc) without the use of non-renewable energy. However, such systems are not yet widespread in Morocco, since traditional wood-fired boilers are still extensively used for water heating purposes in various applications. Therefore, the objective of this work is to evaluate the thermal performance and economic viability of a combined solar thermal and pellet heating system for hot water supply, designed for a public bathhouse under the climatic conditions of Marrakech, Morocco. Moreover, this paper presents the first small-size parabolic trough collectors installation designed for covering part of the hot water requirements in Morocco. In addition, the potential benefits of using such a system are discussed. The dynamic simulations were performed using models developed using TRNSYS 18 energy simulation software. Furthermore, we examined the effect of different system configurations on the thermal performance of the combined solar thermal and pellet heating system. The performance indicators such as solar fraction, solar system efficiency, collector efficiency and primary energy savings, are used for comparing the energy savings and the performance of these different heating systems. Besides, the life cycle cost method was carried out for the financial analysis by comparing the annual life cycle savings for the combined solar thermal and pellet heating against the conventional system (only biomass). The results presented in the current study indicate that adding solar thermal collectors to the biomass system is economically favorable. The lowest life cycle cost of the combined system was obtained with a collector area of 288 m2, which resulted in a solar fraction of 58%. In addition, an annual life-cycle savings of 5,593 € can be achieved compared to biomass boiler system taken as a reference. Moreover, up to 234 tons of CO2 emissions have been avoided through the use of the combined system. Environmentally, this system can be an attractive option for Morocco where wood energy is widely used for the production of hot water in traditional Hammams. The use of such combined solar and biomass systems may result in significant energy savings and CO2 emission reductions as well as limited deforestation in Morocco.