Heat and energy recovery systems recover useful energy in one of several forms for use in a related or unrelated process system. This energy can be recaptured from heat, flow, pressure, and/or gases. There are three main applications for heat and energy recovery systems: commercial, industrial and residential. Commercial systems are designed for use in office buildings, retail complexes, hotels, and apartments. Industrial heat and energy recovery systems are designed for industrial applications such as material handling and processing. Residential systems are available from a variety of suppliers. 

There are many different types of heat and energy recovery systems. Choices include air to air, air to fluid, fluid to air, and fluid to fluid heat exchangers. Air to air devices extract heat from one air process stream and apply it to another. By contrast, air to fluid products extract heat from the air and apply to a liquid process stream. Fluid to air heat exchangers work in the opposite way, extracting heat from a liquid process stream and applying it to the air. Fluid to fluid heat exchangers are also available. These heat and energy recovery systems may use boiler tubes, finned tubes, brazed plates and/or coaxial plates. 

Heat and energy recovery systems include products for heat energy recovery, pressure energy recovery, biogas recovery, and process gas recovery. Products for heat energy recovery are designed to recover usable heat from a process system. Products for pressure energy are designed to recover usable pressure. Air preheaters are used to heat air in a process stream before entry to a final application. Biogas recovery equipment is used to recover gas produced by the biological breakdown of organic matter. Biogas is comprised primary of nitrogen, hydrogen, carbon monoxide, carbon dioxide, and methane. Process gas recovery systems are used with various process gases in industrial applications. 

Types of heat and energy recovery systems include exhaust / flue heat recovery devices, heat recovery ventilators (HRV), energy recovery ventilators (ERV), steam recovery systems, vapor recovery systems (VRS), and products for wastewater heat recovery. Heat recovery ventilators (HRV) and energy recovery ventilators (ERV) use warm, outgoing air to preheat fresh, incoming air in HVAC systems. Energy recovery ventilators (ERV) are heat and energy recovery systems consist of a heat exchanger and a ductwork-based or wall-mounted ventilation system. Heat recovery ventilators (HRV) are similar to ERVs, but use an air-to-air heat exchanger to introduce fresh air from the outside. HRVs may also regulate humidity.