Cooling operation guidelines of thermally activated building system considering the condensation risk in hot and humid climate

One of the promising methods to reduce the peak load of a building is through the use of a Thermally Activated Building System (TABS), which uses the concrete structure as a thermal storage system. Owing to the large cooled surface of a TABS, the asynchronous characteristics of the TABS may cause a high risk of condensation. Previous research proposed to maintain the supply water temperature above the indoor dew point temperature or used sophisticated methods by optimizing the control algorithms with predictive models. However, in reality, the HVAC operators often stop operating TABS for a certain period of time when the outdoor humidity becomes significantly high based on their experiences. This study suggests simple guidelines in operator's level to increase the practical use of TABS by considering the condensation risk in hot and humid climate. Therefore, the weather conditions and the TABS system characteristics were analyzed and possible simple solutions for avoiding condensation were proposed. The possible condensation risk was evaluated with the building simulation and considering the infiltration was found to be the key factor for preventing condensation. During an unoccupied period, the HVAC system did not operate and humidity accumulated in the room. In most cases, the condensation risk became the highest before the day started. Due to the limitations on controlling the TABS and HVAC system, possible solutions as stopping the TABS operation in advance to raise the surface temperature of TABS and operating the HVAC couple of hours ahead for removing the humidity were evaluated. As a result, a separate strategy could not solve problems of occurring the condensation when the outdoor conditions maintained at high humidity with low air temperatures. In order to apply both strategies, the cooling operation guidelines with a simple calculation of indoor dewpoint temperature were proposed and could prevent the condensation at all times.