The cooling energy consumption takes up a significant portion of the total energy consumption of many applications, such as data centers, commercial and residential buildings, and process cooling. Free cooling is a very effective solution for reducing power consumption of cooling systems: it can take effect when the ambient temperature drops just a degree below the process return water temperature, and this is a major benefit for energy saving.
Lightstream Freecool operates in the mechanical cooling mode when the ambient temperature is high; in the partial free cooling mode when the temperature difference between return water and ambient air is as low as 1°C; and in full free cooling mode when the ambient temperature falls below the return water temperature of about 4°C. Raising the water temperatures when possible will also extend free cooling time.
In mixed and full free cooling modes, the chiller capacity is regulated by mixing valves (either 3-way or 2-way motorized valves) and by reducing fan speed, thus further reducing the power consumption of a chiller. In addition, the variable speed control of the fans allows the load to be precisely matched to cooling duty. The transition between the cooling modes is assured by the chiller control system which constantly measures the outdoor temperature.
When the chilled water plant comprises several free cooling chillers, the sequence management system can be used to achieve optimal energy efficiency.
In contrast to convenient air-cooled chillers, free cooling chillers have expanded operating scope and can function at very low ambient temperature conditions.