Commonly, an air-to-air heat recovery ventilator is a device that transfers energy from one side to the other between two air sources with differing temperatures. In other words, it is built on recycling waste heat from exhaust air to warm incoming air before it enters the interior. 

A typical heat recovery system in residential structures consists of a heat exchanger core, extractor fans, a fresh air input, and a separate polluted air exhaust outlet. It can potentially recover 60–95% of waste energy, which is encouraging. 

The heat pipe heat recovery system has greater potential when combined with other sustainable technologies, such as thermoelectric (TE) modules and solar energy systems, due to its advantages, which include easy fabrication and maintenance, a lack of cross-contamination, and higher thermal conductivity. 

The conventional heat pipe comprises two closed tubes containing a working fluid.

As passive heat recovery systems rely on temperature variations between indoor and outside air streams, exhaust heat cannot be collected in its entirety. Several researchers have developed a unique TE heat pump recovery method to counteract this shortcoming of conventional heat recovery. 

Since traditional vapor compression heat pump systems face problems with refrigerants being detrimental to the environment, having moving parts, being noisy, and requiring labor-intensive maintenance, there has been increased interest in applying TE heat pumps for air conditioning and freezers. 

The TE module is a solid-state heat pump device that employs the Peltier effect, pumping heat from one side to the other to produce cold and hot sides with direct current traveling via TE materials. 

The TE module’s tiny size, lightweight, absence of moving parts, reversibility, ease of installation, long lifespan, and eco-friendliness make it a promising alternative to conventional vapor compression systems in some applications. 

The Peltier effect-based TE module could transform electrical energy into a temperature difference and function as a cooler/heater. The characteristics of the TE material, the low-voltage DC power source, and the operating environment will heavily influence the temperature differential. The Seebeck effect allows the TE module to convert thermal energy from a temperature gap into electrical energy. 

The Seebeck effect-based TE module could function as a power generator. The commercial TE modules on the market have been tailored for different temperature ranges based on their applications.  The thermoelectric cooler (TEC) module (Peltier effect) is optimized for temperatures close to room temperature, whereas the thermoelectric generator (TEG) module (Seebeck effect) is optimized for higher temperatures. 

TEG module semiconductor elements are larger than TEC module semiconductor elements.

In recent decades, TE cooling technology has permeated people’s daily lives and has made a noticeable advance. In addition to the military, aerospace, industrial, scientific, and commercial applications, TE modules are commonly used as a cooler/heater in applications such as PC processors, portable food and beverage storage, temperature-controlled vehicle seats, and TE air conditioners.

In conclusion, the TE heat pump approach has several advantages over competing technologies:

  • Without any moving components, durable, and with a lengthy lifespan
  • Tiny size, compact design, low weight, and straightforward installation without orientation restrictions
  • Environmentally friendly, require no chlorofluorocarbons
  • A requirement for low-voltage DC power operation, which would be met by photovoltaic (PV) solar cells, fuel cells, and automobile DC electric sources, and for convenient management
  • Entirely reversible by simply switching the DC power supply’s direction and is not significantly constrained by the operational environment, especially in harsh and sensitive environments

Researchers have undertaken substantial work demonstrating that the heat recovery ventilator could recover heat energy from interior exhaust air. More research, however, concentrates on an integrated practical system of TE heat pumps/heat recovery and residential building components. This study analyzes a passive technology for residential structures combining a TE heat pump and a heat pipe heat recovery system. 

The integrated system is implemented to cut space heating consumption simultaneously and ensure vital ventilation. It is energy efficient, eco-friendly, and compact, and it may be built modularly and integrated with window frames.