Energy Recovery Ventilation in HVAC

     In this post we will see about Energy Recovery Ventilation..

Introduction

The purpose of this article is to present data pertaining to energy recovery ventilation in heating, ventilating, and air conditioning (HVAC) systems and to develop recommendations for its use as a means of improving indoor environmental quality (IEQ). Energy recovery ventilation (ERV) is widely used throughout the world for cooling, dehumidifying, and humidifying purposes. Many countries have laws requiring its use whenever possible in residential buildings. This paper presents a review of published research studies concerning ERV, including its benefits and disadvantages. Recommendations for future work are provided based on a literature review and results from pilot tests conducted at the author’s university laboratory.

Types of Energy Recovery Systems

There are three types of energy-recovery devices commonly used for air-conditioning applications: heat exchangers, desiccants, and condensate absorbers. Heat exchanger units transfer thermal energy between two fluids. Desiccant units absorb water vapor from dry air. Condensate absorber units remove water from heated liquid water sources (e.g., refrigerant lines).

Benefits of Using Energy Recovery Devices

The primary benefit of using energy recovery devices is their ability to reduce energy consumption by reducing the volume of conditioned space needed to achieve a desired level of comfort. The use of these devices may prevent building occupants from feeling uncomfortable when conditions outside the building are milder than inside.

Disadvantages of Using Energy Recovery Devices

The main disadvantage of using these devices is that they have higher initial cost. Additional equipment costs must be considered when investing in the purchase of a device. Another disadvantage is their potential for causing discomfort due to the noise generated by operation.

Energy Recovery Ventilation:

Energy recovery ventilation (ERV) is an innovative technology used to recover heat from exhaust gasses of air conditioning units. This recovered energy is then re-used to preheat the incoming fresh air before its released into the room/area. This increases the thermal comfort / indoor temperature inside the building. It is widely used in commercial buildings especially offices, hospitals, schools etc.

How does ERV work?:

ERV uses the latent heat that exists in the exhaust gases. As the heated air travels through the unit, it absorbs some of the heat lost by the air handler unit. This heats up the incoming fresh air. By increasing the temperature of the incoming air, the air flow rate goes down and this in turn reduces the load on the air conditioner. Thus reducing electricity consumption.

How much energy could we save?:

The amount of saved energy varies based on the number of air handling units installed in a particular area, size of the ducts and airflow rates.

Types of ERV Units:

There are two types of ERV units – active and passive. Active ERV units are connected to the external air supply and they draw the air from outside. Passive ERV units are connected directly to the return air plenum. The advantage of passive units is they don’t require any external source of hot air and thus they don’t consume electricity. However, there is a trade off here. Since there is no external source of air, the passive unit will be warmer and this means the recirculated air won’t be as fresh as when drawn directly from the outdoors.

Energy recovery ventilation (ERV) is a method of air exchange designed to increase energy efficiency in buildings. ERV combines two technologies: forced convection and natural ventilation (NV). NV is the movement of outdoor air through openings into indoor spaces where occupants breathe the air without any input from mechanical devices. ERV uses a fan to force outside air through holes in the ceiling of a space while allowing fresh air to enter the room. This process forces stale air out of the building, thus increasing the comfort inside. This type of technology is especially helpful when temperature control is difficult due to heat gain in summer and low air flow in winter.

ERV is a ventilation technology that captures heat from building spaces and uses this energy to heat or cool buildings. ERV is typically used in buildings where space is at a premium, but it can also be used in greenhouses, livestock barns, and warehouses. 

Energy Recovery Ventilation (ERV)is designed to recover energy from the exhaust air stream rather than waste it out into the environment. This reduces the amount of cooling needed to achieve desired comfort conditions. Heat recovery ventilators typically consist of heat exchangers, fans and ducts. They work by transferring energy from hot exhaust gas to cooler incoming fresh air through the exchange of mass. ERVs are used in many industries where heating or cooling requirements exceed the capacity of conventional equipment, as well as in commercial buildings. There are two types of ERVs, single stage and multi stage.

Single Stage

Single stage ERV uses only one fan to blow both the recycled and incoming air and recovers only sensible thermal energy (heat). Single stage ERVs are ideal for small spaces such as attics, crawlspaces or basements where the air flow is low and space constraints allow for a single fan without causing excessive noise.

Multi Stage

Multi stage ERVs use multiple fans to blow incoming and outgoing air separately. Each fan blows its respective airflow at different speeds allowing the transfer of latent heat but avoiding any mixing of the air streams. As a result, multi stage ERVs tend to reduce the overall temperature of the space as compared to single stage ERVs while maintaining a comfortable indoor climate. The tradeoff is that they require additional space for installation and operation.

ERV is one of the most popular methods used to recover energy from exhaust air, and has many benefits including reduced energy usage, increased comfort levels, reduced emissions, and lower utility bills. ERV is commonly utilized in commercial settings where space constraints and low operating costs require minimal equipment investments to achieve measurable results.

In HVAC applications, ERV is used to improve indoor air quality by extracting stale air from interior spaces and exhausts it outdoors through ventilation ducts. There are two types of ERVs; active and passive. Active ERVs are powered ventilators that require electricity. Passive ERVs, however, operate without any external energy supply. Passive ERVs utilize thermal mass and natural convection to remove stale air from internal spaces.

How does Energy recovery ventilator works?

The primary function of energy recovery ventilation is to reduce the amount of energy consumed by the air conditioning system, thereby reducing the heating and cooling costs. This is achieved through the exchange of outside fresh air into the return air stream using fans.

Benefits of Energy Recovery Ventilation

It has proven to save approximately 10% - 20% on Heating & Cooling expenses. It helps to improve indoor air quality. This reduces sick building syndrome among occupants. It has a positive impact on the environment by saving energy and producing less carbon dioxide. 

Advantages of ERV

Reduces noise levels by up to 60 dB. Reduces humidity levels by up to 50%. Helps to control odors and smells. Improves acoustic comfort indoors. Increases occupant productivity due to better air quality and increased worker satisfaction. Decreases HVAC equipment failures and maintenance costs.

ERV uses heat recovery rather than air movement to control indoor climate. Heat recovery vents allow fresh outdoor air to pass through while warm stale indoor air passes into the outdoors. ERVs improve energy efficiency and reduce carbon dioxide emissions by reducing the amount of energy needed to maintain comfort indoors. They cool down the air in the summer months and warm it in the winter. 

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