Ultraviolet germicidal irradiation (UVGI) is employed to purify the microbes in airflows and on solid surfaces. When air containing bacilli moves through an air-conditioning system with UVGI, the airflow is exposed to radiation during its residence time. The radiation is affected by the location of the UV lamp in the airflow. To determine better installation conditions, the dependence of the sterilization effect on such installation conditions needs to be analyzed. In the present study, guidelines are proposed to determine the installation location based on the concept of the age of air. A numerical simulation is performed to validate the guidelines. In general, the airflow inside the air-conditioning system is not uniform although a heat exchanger equalizes the pressure. Hence, the residence time of the air varies depending on the stream lines. If the UV lamp is installed on a stream line that has a long residence time, the airflow on the stream line can be exposed to more UV intensity; however, the airflow on other stream lines with shorter residence times will accordingly be at a disadvantage. Therefore, the lamp needs to be installed on the stream line with the shortest residence time inside the system to increase the level of sterilization. Even if the average amount of UV dose of the entire airflow is high, the minimum value may be low depending on the non-uniformity of the airflow. The minimum value should be increased to assure a good sterilization effect. A numerical simulation of UV radiation coupled with fluid dynamics was performed for a simplified model of a fan-coil unit and two realistic models. The residence time was analyzed to determine the location of the lamp installation. The results of the UV dose D were compared between the proposed and conventional lamp locations. The proposed lamp location resulted in a D value that is 10–100% higher than that for the conventional lamp location. This indicates the validity of the proposed guideline to determine the UV lamp location.

We developed an open-cycle type adsorbent thermal storage system with HAS-Clay to utilize low-temperature waste heat. The demonstration tests were performed no a stationary type and an offline heat transportation type after the development of systems and materials, such as the durability of HAS-Clay. In the offline heat transportation type, the thermal storage tank charged in the co-generation system was transported by the tractor-trailer and used to heat up water and air in a swimming center. It was evaluated as an absorption-based heat storage system through three seasons: summer, interphase, and winter. The test data indicated a regenerating efficiency of 90% or more. The charge/discharge characteristics of the system were also evaluated. In addition, by comparing the test data with the numerical analysis model on the charge/discharge operations, it was confirmed that the numerical analysis model can be used as a design tool.

Variable air volume (VAV), variable water volume (VWV) control, and CO₂ concentration control are expected to contribute to energy conservation in heating ventilating and air conditioning (HVAC) systems, and various attempts have been made to quantify their energy-saving effects. In the case of VAV and VWV control, studies have not yet set detailed control parameters or considered the control behavior of a system under various operating conditions, including intermediate periods. Although CO₂ concentration control has been studied through actual measurements and simulations, issues remain in the experimental conditions and calculation conditions of the simulation. In general, VAV control, VWV control, and CO₂ concentration control combine various control logics to control the thermal environment and air quality of the room, and many detailed control parameters are incorporated, such as the integration time in the demand airflow calculation equation, and the proportional gain of PI control. In contrast, these control logics are designed by assuming the maximum load, and they may not be able to achieve proper control in some operating conditions such as low load during the intermediate periods. In our previous paper, we developed a simulation program that modeled the physical model, equipment model, and control logic in as detailed a manner as possible for a HVAC system and building envelope and quantified the energy-saving effect of both VAV and VWV control. Therefore, in this study, we use the same system simulation program as in the previous study and aim to investigate the effect of changing the detailed control parameters on the energy-saving effect and control behavior of VAV, VWV, and CO₂ concentration control. At this time, not only the energy consumption but also the controllability of the room temperature was also considered. First, we calculated the annual impact of the parameter changes, and then we analyzed the characteristics and control behavior on a monthly basis and on a representative day. The target parameters are related to the demand airflow calculation equation, supply air temperature control, damper opening control, supply fan frequency control, exhaust fan, chilled/hot water pump, bypass valve control, and CO₂ concentration control. In this study, a system simulation in which the physical model and control logic are constructed in as much detail as possible was performed, which enabled case studies for the detailed control parameters, and their influence could be calculated at the system level. When analyzed on a monthly basis, the effect of changing the parameters on the energy consumption and controllability was small in the intermediate period when the heat load was small; however, the effect was more observable in winter and summer when the load was large. It was also shown that the change in the proportional gain of the damper opening PI control also affected the air supply fan frequency and air temperature control. It was confirmed that a single parameter change can affect the entire system. Understanding the effect of parameter changes on the system behavior will be an important knowledge for data analysis and system design of VAV/VWV systems.

Earth-to-air heat exchangers (EAHEs) utilize the heat capacity of soil to pre-cool or pre-heat outside air. However, condensation can build up within an EAHE, and can potentially lead to air pollution. It is necessary to optimize the control of EAHE in the operational phase. In this study, we focused on reinforcement learning (RL) control. In our previous study, we proposed a Deep Q-Network (DQN) based control method and showed its effectiveness as an operational control for EAHEs. DQN is a value-based algorithm that learns the value function Q to find the policies. In contrast, a policy-based algorithm learns policies directly, without learning a value function. However, the operation control of an EAHE using a policy-based algorithm has not been examined. The purpose of this study is to establish the optimal control rules for an EAHE using proximal policy optimization (PPO), which is a policy-based RL algorithm. First, we define the control problem for RL using the environment estimated by a long-term performance prediction method of EAHE based on CFD. Then, we implement PPO. We verify the effectiveness of PPO by comparing random control with DDQN. The following results were obtained. 1) The number of learning iterations required to converge was about 200 for PPO and 150 for DDQN. At the end of the study, the sum of rewards was about -2,000 for DDQN and -1,500 for PPO. 2) Compared with random control and DDQN, PPO achieved the highest control performance in both energy saving and condensation control.

The advantages of a 20-ft container construction include their convenience for transportation, rapid assembly, and low costs. In recent years, containers have been used in various applications, including medical testing, mobile offices, business showrooms, restaurant and dining, and industrial purposes. These applications have contributed to the increasingly diverse requirements for indoor ventilation and positive or negative pressure. To explore the relationship between the negative pressure generation effectiveness and air change rate of low-airflow simple fans in a 20-ft container construction, the experiment was conducted under the conditions of an air change rate of 6–12 T/h and that the container construction did not contain hazardous exhaust gases, hence not using any high-efficiency particulate absorbing filter. The lowest standard for pressure difference was employed (-2.0 Pa). The experimental results revealed that to achieve the minimum pressure difference requirement of -2.0 Pa, the air change rate must be 8 T/h or higher in completely closed rooms and 10 T/h or higher in rooms with an open grille. Moreover, to achieve the negative pressure requirement of -10 Pa, the air change rate must be 18 T/h or higher in completely closed rooms and 30 T/h or higher in rooms with an open grille. Finally, the negative pressure generation effectiveness of a fan decreases with distance; therefore, a fan should be positioned close to the center of a room.