Energy Recovery Systems

According to the Occupation Safety and Health Administration (OSHA), the average American spends 90 percent of their day inside. Since “fresh” or “outside air” has a positive effect on an individual’s overall health, mood and productivity, it becomes increasingly more important to focus on improving the quality of air inside buildings by “bringing fresh air in.”

Bring the ‘Outside’Air Inside with a Marcraft® Energy Recovery Unit

Did you know…?
Reports from medical professionals indicate that 50 percent of all illnesses are linked to polluted air?
The EPA ranks indoor air pollution among the top four environmental risks to the public.

What to do?  
If you are installing a new ventilation system or upgrading a current one, here are suggestions to consider for your specific ventilation system that will: 

     1.  Reduce the consumption of energy
     2.  Conserve natural resources
     3.  Reduce building operational costs

How Much Outside Air is Enough?
Current ventilation standards recommend that 15 to 60 cubic feet per minute (CFM) of outside air should be supplied for every person within the building.  While this is only a recommendation, many companies apply it as their standard.  However, heating, cooling and controlling the humidity of outside air can become costly if some sort of energy recovery is not used.

MarCraft’s Energy Recovery Products provide an economical solution to maximizing ventilation without dramatically increasing the mechanical equipment cost, space requirements and operational costs.

What is ENERGY RECOVERY?
Energy Recovery uses exhaust air that contains heating or cooling energy to condition outside air.  Utilizing this exhaust energy will lessen overall building consumption of energy, therefore reducing building operational costs as well as conserving natural resources.  Commercial buildings account for one-third of the nation’s total energy consumption as well as two-thirds of our country’s total electrical consumption.

While the design of Energy Recovery products can be custom manufactured to optimize any application or requirements, an Energy Recovery Unit (ERU) is generally defined by one of four major components found inside the ERU.  The four components are:

     Plate-type Air-to-Air Heat Exchangers
     Rotary Energy Recovery Wheels
     Heat Pipes
     Run-Around Loops

MarCraft is committed to a cost-effective solution for cleaner air using an Energy Recovery Unit.

University of Illinois Urbana-Champaign - Institute for Genomic Biology

Plate Air-to-Air Heat Exchangers
Plate Air-to-Air Heat Exchangers recover energy by crossing discarded exhaust air and ventilation (supply) air in side-by-side air streams with common recovery plates.  The process “preconditions” the supply air thus requiring the primary conditioning media to do less work.
The Plate Air-to-Air Heat Exchanger offers one spectacular benefit others do not:  There are no moving parts.  Obviously, the absence of moving components results in lower maintenance costs and less unit failure!
 

Heat Pipes
Another consideration is the use of Heat Pipes, which also can be incorporated in Energy Recovery Units.  Heat Pipes require side-by-side air streams, similar to Energy Recovery Wheels and Plate Air-to-Air Heat Exchangers.

Heat Pipes are coils filled with a specific amount of refrigerant that naturally changes phases based on exhaust and supply temperatures, using vapor pressure to transmit energy.  Unlike Energy Recovery Wheels, Heat Pipes recover only sensible energy. However, they rarely involve moving parts.  Again, the lack of moving components results in lower maintenance costs and less unit failure.  Sensible effectiveness of Heat Pipes is between 45 percent and 65 percent.

Rotary Energy Recovery Wheels – ‘Total Energy Recovery Units’
Energy Recovery Wheel units retrieve a portion of exhausted energy by utilizing an enthalpy wheel that rotates between the supply and exhaust air streams.  The distinct advantage of the Energy Recovery Wheel is that it can recover both sensible and latent energy.
Utilizing the latent energy can vastly increase the effectiveness of the wheel, especially in hot, humid environments.  For instance, a 50,000 CFM ENERGY RECOVERY UNIT can have a total effectiveness of up to 85 percent, depending on design conditions.  Partial loads are accounted for by varying the speed of the rotating wheel or by bypassing air.

One concern regarding the Energy Recovery Wheel is cross-contamination.  This is averted by designing wheels to solely transfer moisture and not airborne contaminants.  A purge can also be built into the wheel to wipe the wheel with fresh outside air, further reducing cross-contamination.
According to ASHRAE, the purge section on an enthalpy wheel reduces cross-contamination to less than 0.1 percent when properly applied.

Run-Around Loops
The job of Run-Around Loops is to circulate a liquid between two different air streams.  By simply adding pumps and coils, this becomes a cost-effective energy recovery solution.  Unlike the other Energy Recovery devices, a Run-Around Loop can take advantage of air streams that are not directly next to one another.  Run-Around Loops have limited moving parts and have no cross-contamination issues.  However, due to the typical distance between the outdoor air unit and the Heat Recovery Unit, this type of system also requires onsite interconnecting piping.
A major benefit to this system is that, if properly designed, pre-heat coils can function as the energy discharge side of the loop in the outdoor air unit.  These types of systems are typically controlled by varying water flow with a VFD-driven pump, or by using a three-way bypass valve.  Sensible effectiveness is estimated between 55 percent and 65 percent.

Installing Energy Recovery can dramatically reduce the cost and demand of energy in many different applications.  The criteria to consider when selecting the correct type of ENERGY RECOVERY UNIT (ERU) for your application are as follows:

• Equipment Space Requirements
• Cross Contamination Issues
• Location of Supply and Exhaust
• Climate

One major consideration that should not be overlooked when selecting an Energy Recovery Unit is cabinet or housing leakage.  There are many manufacturers of Energy Recovery Units, but very few can meet the tight construction of a MarCraft TRUCustom™ Energy Recovery Unit.

Interested in having an experienced MARCRAFT engineer can help you design a solution to meet your ENERGY RECOVERY requirements?  Give us a call at 800-325-1303.

Sun Chemical - Explosion Proof Energy Recovery Custom HVAC Units