Profitability Variations of a Solar System with an Evacuated Tube Collector According to Schedules and Frequency of Hot Water Demand

Abstract

The use of solar water heating systems with evacuated tube collectors has been experiencing a rapid growth in recent years. Times when there is demand for hot water, the days of use and the volumes demanded may determine the profitability of these systems, even within the same city. Therefore, this paper characterizes the behavior of a solar system with active circulation with the objective of determining the profitability variations according to the timing and schedule of demand. Through a simplified methodology based on regression equations, calculated for each hour of the day based on data from an experimental facility, the useful energy is estimated from the time and frequency of the demand for hot water at 60 °C. The analysis of the potential profitability of the system in more than 1000 scenarios analyzed shows huge differences depending on the number of days when the water is demanded, the time when demand occurs, the irradiation and the average price of energy. In cities with high irradiation and high energy prices, the system could be profitable even in homes where it is used only on weekends. The study of profitability in a building of 10 homes shows that by applying an average European household’s profile for hot water demand, levels close to full potential would be reached; for this, it is necessary to optimize the collection surface.

Keywords

• active solar water-heating system
• evacuated-tube collector
• hot water
• schedule of demand
• profitability