A Standard-Based Method to Simulate the Behavior of Thermal Solar Systems with a Stratified Storage Tank

Abstract

Thermal solar systems are interesting solutions to reduce CO 2 emissions and gradually promote the use of renewable sources. However, sizing such systems and analysing their behavior are still challenging issues, especially for the trade-off between useful solar energy maximization and stagnation risk minimization. The new EPB (Energy Performance of Buildings) standard EN 15316-4-3:2017 offers several methods to evaluate the performance of a forced circulation solar system. One of them is a dynamic hourly method that must be used together with EN 15316-5:2017 for the simulation of the stratified storage tank connected with the solar loop. In this work, such dynamic hourly method is extended to provide more realistic predictions. In particular, modeling of the pump operation due to solar fluid temperature exceeding a set threshold, or due to low temperature differential between solar field and storage tank, is introduced as an on–off control. The implemented code is applied to a case study of solar system for the preparation of domestic hot water and the impact of different design parameters is evaluated. The model predicts a higher risk of overtemperature lock-out or stagnation when the solar field surface is increased, the storage volume is reduced and water consumption is set to zero to simulate summer vacation periods. Finally, a simple modulating control with a time step of a few seconds to a few minutes is introduced, quantitatively showing the resulting benefits in terms of useful solar energy increase, back-up operation savings and reduced auxiliary energy use.

A Novel Dynamic Approach to Cost-Optimal Energy Performance Calculations of a Solar Hot Water System in an nZEB Multi-Apartment Building

“…This model, based on the operative temperature, is used to calculate product-specific values of setpoint variations, which are then used in heat loss calculations instead of tabulated values. Piana et al [23] have shown that EN 15316-4-3:2017 and EN 15316-5:2017 can successfully be applied in the design process of a solar thermal system. In their work, a non-invasive solar loop pump control model, allowing the quantification of the risk of stagnation resulting from increased solar field areas or decreased storage volume, is added to the standard framework.…”

“…The reviewed studies usually deal with individual modules [22][23][24][25], but there were no studies found in which the overall calculation was performed with the goal of finding a cost-optimal solution. Hence, the main novelty of this study is in demonstrating the applicability and reliability of the overall complex and comprehensive calculation procedure, based on the new EPB standards for assessing the energy performance of a building.…”

Impact of Air Density Variation on a Simulated Earth-to-Air Heat Exchanger’s Performance

“…However, although they offer great possibilities, their use requires specialised knowledge and experience. Hence, there is also a need for methods simpler but accurate enough to perform annual simulations with hourly time steps required by current standards and provide reasonable time resolution for thermal phenomena, occupation schedules, weather data and calculation accuracy [29][30][31], especially in terms of energy certification of buildings.…”

Dynamic Approach to Evaluate the Effect of Reducing District Heating Temperature on Indoor Thermal Comfort

“…The main tool for decarbonization is the integration of renewable energy sources (RES), but this is a challenging task, mainly because of their variability in space and time. Solar energy, for instance, is an abundant source at most European latitudes, but it requires reliable tools to evaluate both the actual energy potential [18] and the correct sizing and operation of the system [19]. The mismatch between demand and supply is usually overcome through flexible-oriented solutions, like the installation of thermal energy storages (TES) [20]).…”