Domestic hot water consumption vs. solar thermal energy storage: The optimum size of the storage tank

Abstract

Many efforts have been made in order to adequate the production of a solar thermal collector field to the consumption of domestic hot water of the inhabitants of a building. In that sense, much has been achieved in different domains: research agencies, government policies and manufacturers. However, most of the design rules of the solar plants are based on steady state models, whereas solar irradiance, consumption and thermal accumulation are inherently transient processes. As a result of this lack of physical accuracy, thermal storage tanks are sometimes left to be as large as the designer decides without any aforementioned precise recommendation. This can be a problem if solar thermal systems are meant to be implemented in nowadays buildings, where there is a shortage of space. In addition to that, an excessive storage volume could not result more efficient in many residential applications, but costly, extreme in space consumption and in some cases too heavy. A proprietary transient simulation program has been developed and validated with a detailed measurement campaign in an experimental facility. In situ environmental data have been obtained through a whole year of operation. They have been gathered at intervals of 10 min for a solar plant of 50 m 2 with a storage tank of 3 m 3 , including the equipment for domestic hot water production of a typical apartment building. This program has been used to obtain the design and dimensioning criteria of DHW solar plants under daily transient conditions throughout a year and more specifically the size of the storage tank for a multi storey apartment building. Comparison of the simulation results with the current Spanish regulation applicable, "Código Técnico de la Edificación" (CTE 2006), offers fruitful details and establishes solar facilities dimensioning criteria.

A New System to Estimate and Reduce Electrical Energy Consumption of Domestic Hot Water in Spain

“…Annual average domestic hot water (DHW) energy consumption per house in different regions from Spain [3]. Recent research made by Rodriguez-Hidalgo [4] shows that DHW consumption depends not only on the geographical situation, but also on people's habits, the time of year, and the purpose of the building. Differences shown in Table 2 could be caused by inlet temperature of cold water or other parameters.…”

Solar Water Heating

“…Several different estimates are found in the literature. For example, Rodriguez-Hidalgo et al (2012) have reported on a study of the hot water use of 215 inhabitants. The average water draw for each hour is shown in Figure 10.…”

GIS-Based Planning and Modeling for Renewable Energy: Challenges and Future Research Avenues

“…Hot water consumption further depends on people's habits, the time of the year, the building type, the building usage and also on the inhabitants' specific lifestyle, etc. [40]. However, such dependencies can vary spatially, as well as temporally, or they tend to cluster in space and time.…”