Energy Recovery Unit
What is Energy Recovery Unit (ERU) ?
HVAC systems are used for Heating, Ventilation and Air-Conditioning in small and large buildings alike. The Energy Recovery Unit (ERU) is part of the Galisano Institute for Sustainability’s (GIS) HVAC system. The ERU circulates the air inside of GIS such that a comfortable and pleasant environment is maintained for its occupants.
How HVAC systems and ERU Work?
Most HVAC systems can be described and illustrated in a series of steps:
1. An outside fan unit pulls the air that will be needed and provides the airflow for the entire building.
2. The air then runs through a filter so that outside undesirable materials do not pass through.
3. After the filter, the air is then drawn into the air return unit which again filters the air and sends it to the main heating and cooling unit.
4. From there, the air is either provided moisture or has it taken away to achieve a desirable humidity level.
5. It is then heated or cooled and sent throughout the rest of the building via a series of ducts. Note, all of these steps are powered by electricity.
The ERU achieves the same goals but uses much less energy due to the way it works:
1. The first step in the process is the air intake which is performed by a large air unit on top of the building.
2. Then, the air travels through a filter which removes undesirable particles and materials.
3. The next step is for the air to pass through the enthalpy wheel and to either be heated or cooled.
The wheel works by taking the heat from the outgoing air and giving it to the incoming air through a heat exchange mechanism. In the summer, the outgoing air will be cooler and so the incoming air will have to be cooled while in the winter, the outgoing air is warmer and the incoming air becomes warmed.
4. After heating or cooling, the air passes through conventional coils powered by hot or cold water for additional heating and cooling that may be required.
5. Then, the air passes through the desiccant wheel which controls the humidity levels in the air.
The same idea as the enthalpy wheel is applied. Outgoing air has its moisture content removed by the wheel and as it turns, that moisture content is then absorbed by the incoming air.
6. Lastly, the air is pushed through to the rest of the building.
Energy Recovery Unit
On a normal sunny day in summer, the outdoor air is dry and hot, and the indoor air should be cool and not so dry. The green enthalpy wheel will take away the heat from the outdoor air and ensure it does not run into the building, and the orange dehumidification wheel will take away the moisture in the indoor air and ensure it does not run out of the building.
On a normal snowy day in winter, the outdoor air is wet and cold, and the indoor air should be warm and not so wet. The green enthalpy wheel will supply the heat to the air entering in the building and the orange dehumidification wheel will take away moisture from the outdoor air and ensure it does not run into the building.
Is ERU helping GIS to be more sustainable?
Environmental
The ERU unit at the GIS runs on electricity and waste heat produced from the fuel cell. In 2014, the ERU saved about 2485 gigajoules of energy.
These energy savings helped GIS to reduce its greenhouse gas emissions by 476 Metric tons of CO2 equivalent.
It will take about a year for 390 acres of forest to sequester this amount of carbon.
From these energy savings, we can supply electricity to as many as 44 households.
Economic
In 2014, ERU helped to save about 690,191 kWh of electricity for GIS which corresponds to $64,187.
Social
ERU has a quite operation compared to conventional HVAC system which has components such as compressor and condenser.
For students in GIS, ERU technology is a great educational tool.
