Impact of Micro-Meteorological Changes on Plant Performance due to the Construction and Operation of an Energy Plant

Micro-meteorology, which focuses on the lower atmosphere closer to the surface and at finer scales, significantly impacts energy plants regarding site selection, design, and operation. In liquefied natural gas (LNG) plants, it is necessary to remove a substantial amount of heat during the liquefaction process. As part of the heat removal system, many hundreds of air-cooled heat exchangers (ACHEs) are utilized and are typically mounted on a central pipe rack in a train configuration. For a typical LNG plant with two trains, the air-cooled heat exchangers (ACHEs) located in an area measuring 500 m x 500 m can discharge approximately 40,000 to 60,000 m³/s of air, carrying between 1,000 and 1,800 MW of heat, which corresponds to a heat intensity of 4 to 8 kW/m². In contrast, the regional heat intensity in Tokyo is approximately 50 W/m², making the heat intensity in the LNG plant about 80 to 160 times greater. Additionally, tree removal and land surface alteration are commonly conducted over an area of 2 km x 2 km for construction in forested regions. This suggests that the construction and operation of the LNG plant can significantly impact the micro-meteorology of the surrounding area. However, LNG plants are typically designed without considering the impacts of construction and operation, which can lead to performance levels that fall below design expectations. The effects of plant construction and operation may manifest as changes in local temperature, humidity, and wind patterns. Ambient temperature is a critical design factor for the ACHEs. Depending on the liquefaction process, a 1°C increase in temperature can reduce LNG production by 1 to 5%. If local ambient temperature increases after the plant construction and operation, the performance of the LNG plant may deteriorate directly, or additional energy may be required to produce the same amount of LNG. Humidity also has a direct impact on combustion equipment and the emission of environmental pollutants. High humidity levels may cause incomplete combustion, thereby decreasing combustion efficiency. Wind direction plays a crucial role in determining the orientation of the train of heat exchangers in the LNG plant. Particularly for multi-train configurations, crosswinds can result in significant hot air recirculation (HAR), a phenomenon wherein hot air from the ACHEs flows back into their intake or into the intake of other equipment, such as gas turbines. Once HAR occurs, it can reduce LNG production by 20%, leading to millions of dollars in losses each month. Furthermore, wind speed affects the airflow of ACHEs, with higher wind speeds potentially reducing the airflow rate.

This study aims to elucidate the mechanisms and extent of the impact resulting from the construction and operation of energy plants on micro-meteorology at the construction site. This will be achieved using the Multi-scale Simulator for the Geoenvironment (MSSG), a multi-scale atmosphere-ocean coupled model developed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the Institute of Science in Tokyo, and Waseda University. The simulation compares micro-meteorological data before and after plant construction and operation, considering land surface changes and artificial heat release under the climatic backgrounds of both tropical and cold regions.

The study demonstrates that ambient temperatures at the construction site increase due to land surface changes and artificial heat release. Additionally, it is found that wind directions change due to tree removal. Countermeasures for reducing the impact are considered.