Nothing should go to waste, and heat is no exception. Heat recovery devices capture thermal energy and use it for space conditioning and water heating. This helps improve energy efficiency and reduce operating costs. Don’t rush in, however. Heat recovery systems are not right for every application. A careful evaluation is necessary to determine whether it’s the best fit for your facility.

Ventilation systems

Ventilation systems bring in fresh air to replace conditioned air that is exhausted. In winter, a substantial amount of heat is wasted when warm air goes outside. Heat recovery ventilation (HRV) devices capture that heat and transfer it to cold incoming supply air, reducing heating costs.

HRV devices come in many types, including flat plate, rotary heat and energy (enthalpy) wheels and heat pipe air-to-air heat exchangers. All require outdoor air intake and exhaust ducts.

When HRV devices are integrated into a heating, ventilating, and air conditioning (HVAC) system, the resulting heat recovery allows for the installation of smaller HVAC equipment, reducing investment and operating costs.

Heat sourcing

Recovering heat from one area of a building, such as the kitchen or laundry, and delivering it to other areas is a great way to increase energy efficiency and building comfort. Heat pumps are particularly suited for removing heat from a heat source (air, water or process fluid) and making it available for other uses. For example, heat pumps can remove excess heat from laundry facilities (increasing comfort and productivity) and use it to heat water in other areas. Energy wheels are also used to recover kitchen or laundry waste heat.

Water heating

Water heating is a good application for high-temperature heat recovery, since temperature requirements are higher than those needed for space heating. Using recovered thermal energy to heat or preheat water is cost-effective in facilities with significant hot water needs, such as laundries, restaurants and hotels. Shell and tube heat exchangers are commonly used in these applications. They transfer heat between two physically separated fluids; one flows through the shell, the other through the tubes.

Facilities with steam systems can recover heat from hot condensate as it transfers to atmospheric pressure in the condensate receiver. A heat exchanger is installed in the condensate return, where it transfers heat to cold make-up water as it circulates into the hot water tank.

Combined heat and power

Combined heat and power (CHP) provides on-site generation of electricity and heat recovery for space conditioning or water heating. Drivers include combustion turbines, reciprocating engines, fuel cells, or microturbines. A heat exchanger typically transfers exhaust heat to a waste heat boiler.

Benefits of CHP systems include increased energy efficiency, improved power reliability and reduced environmental impact. CHP has been used successfully in a variety of commercial applications, such as hospitals, hotels, casinos and large office buildings.

Despite their benefits, CHP systems typically require a significant upfront investment and may not be cost effective in every situation. When evaluating a CHP installation, or any heat recovery technology, carefully consider your energy needs, the application, the installation costs and the potential return on investment.