Economizers

An economizer is a device or control system designed to recover energy or reduce energy consumption by using energy that would otherwise be wasted. In HVAC and industrial settings, economizers optimize the use of outside energy sources or exhaust heat to lessen the need for mechanical cooling, heating, or electric power.

In buildings, the most common form is the air-side economizer. This system uses dampers to regulate outdoor air intake and can supplement or replace mechanical cooling when outdoor conditions are favorable. Controls may base decisions on dry-bulb temperature or enthalpy to maintain comfort while reducing compressor run time. Benefits include lower energy use and reduced peak electrical demand. Potential drawbacks involve humidity control, indoor air quality, and mechanical faults such as stuck dampers or faulty sensors.

Water-side economizers operate by circulating cooling water from a cooling tower or another source to air-handling coils, thereby achieving cooling without running chillers under suitable outdoor conditions. They are common in large buildings, data centers, and industrial facilities where significant cooling loads exist. While they can offer substantial energy savings, they require adequate water treatment, corrosion control, and reliable hydraulic design.

Boiler economizers, located in the path of flue gases, recover heat from exhaust to preheat boiler feedwater. This improves boiler efficiency by raising feedwater temperature before it enters the boiler, reducing fuel consumption and emissions. They are widely used in steam plants, refineries, and power generation.

In power and process industries, economizers may also refer to feedwater or turbine exhaust economizers integrated into larger energy recovery systems. Effectiveness depends on climate, system design, maintenance, and control strategies. Properly configured economizers can yield meaningful energy savings but require careful integration with other controls and safety considerations.