High Efficiency Heat Pumps

              One of the best ways to conserve energy on any mechanical system is by reducing the number of equipment. This was the goal in mind when manufacturers created water source heat pumps.

Water source heat pumps work by tranferring heat from one system that is trying to lose heat, to another system that is trying to gain heat. As described above, water source heat pumps utilize heat given off of by other equipment and transfer it through a heat exchanger to heat up water. Cold water is guided through a heat exchanger where heat is transferred through a series of plates or tube, and that heat is used to heat up the cold water.

 

           Similar to water source heat pumps and ground water cooling, there are geothermal heat pumps. Geothermal heat pumps work by using "constant temperature of the earth as the exchange medium instead of the outside air temperature which allows the system to reach fairly high efficiencies (300% to 600%) on the coldest winter nights, compared to 175% to 250% for air-source heat pumps on cool days" (Geothermal Heat Pumps 2012). In lieu of utilizing heat given off by other systems or equipment, geothermal heat pumps use ground temperature to transfer heat.

 

Geothermal Heat Pumps (2012). ENERGY.GOV. Retrieved from             

 http://energy.gov/energysaver/articles/geothermal-heat-pumps

Propoer Load Calculations for High Efficiency Buildings

In most commercial buildings mechanical systems account for nearly fifty percent of the buildings energy use. Being that the mechanical system is responsible for almost half of the total energy consumption of the building, manufacturers have been forced to address different means of achieving a more sustainable product. But first some questions must be answered. These questions include, what are the most demanding loads for the building, what is the criteria for the mechanical system, how does newer more efficient HVAC equipment compare to convention HVAC equipment, what ways can manufacturer use new unconventional designs to accommodate the needs of the building while addressing sustainability.

 

                One of leading factors in unsustainable and inefficient mechanical systems is improper load calculations. This results in under loading or overloading the mechanical equipment. By overloading the equipment, the undersized units have to work harder and need more energy to push the internal motors. By installing equipment that is too large for the application, the unit will cycle on and off more, causing the same amount of energy use as under sizing the unit. To cut down on load consumption, designers must design buildings with the smallest but most efficient unit for the application as well as calculate when peak loads may occur. Traditional methods of calculating heat loads include use general rules or "rules of thumb". With today's technology, designers are depending more on software, especially when designing buildings for sustainability and maximum efficiency. Traditionally system loads were sized by the amount of cooling required per square foot of floor area, which is diffucult and senseless in high performance buildings which require maximum efficiency with minimum energy.  Once the load has been calculated designers must choose what equipment will meet the design intent of the building.

 

Underfloor Air Distribution

               Recently, the greening of construction has seen many changes in the mechanical industry. This is especially noticeable in the area of air distribution. Typical Air distribution systems consist of an air handling unit that drives air into the multiple zones of the building. This is done through duct, which can vary depending o the type of system such as mixing boxes, vavs, electric heat, etc. All the aforementioned systems were typically run in the ceiling space above each zone and air was discharged through diffusers and pulled by registers or grills. The more traditional systems were always less sufficient because they require that the air handler push a large volume of air into the space with enough force or throw to meet the occupants comfort level.  The reason for such a large volume was the occupants, lights and other items in the space that release heat. With the traditional system, air was forced downward to cool ant than the cool air and heat was pulled back through the return grilles and registers.

 

                A recent trend in the mechanical industry in underfloor air distribution. Underfloor air distribution works exactly as it sounds. Air is pushed through a duct system beneath the floor which in most cases is referred to as an air highway. As the air is pushed through the air highway, it is pushed through diffusers in the floor and the air is then pulled from grills and registers in the ceiling. The benefits of the underfloor air distribution, is that it acts just opposite of the traditional systems sited earlier. Underfloor systems blow cool air from beneath the floor which in turn pushes the heat up. This is much more efficient as heat has a tendency to rise. With this type of system the air handling unit is forced to do much less work . Though these systems are fairly new to common commercial buildings, data centers and IT centers have been using this technology for years. Not only is underfloor air distribution known for its efficiency, but also for its flexibility. Since the diffusers travel along and air highway below a raised floor, the diffusers can be moved to accommodate different room configurations. Many offices or multipurpose buildings that change cubical or partition layouts often, can benefit from this flexibility. Underfloor Air Diffusers are designed with adjustable damper controls to accommodate any size zone or room layout.  

Benefit of Energy Recovery Ventilation

One the main components of almost any commercial or  industrial mechanical system is the central air handling unit. The air handling unit consists of a boxed frame, a motor driven fan and a refrigerant or chilled water coil or multiple coils.  Although one of the simplest pieces of equipment in the mechanical system, it consumes the energy. An air handler works by using a motor driven fan to force return or outside air across a coil, resulting in cool air. Air handlers are controlled by the building automation system or thermostat. As cool air is required, the motor kicks on and off to meet the buildings demand. As in many cases, air handlers are oversized and have tendency to cycle on and off the requiring much more power than necessary. To offset the high demand for energy and the constant need for cooling manufacturers have introduce energy recovery ventilators.

How it Works

Energy recovery ventilation works by mixing preconditioned exhaust or return air, with incoming outside air. This is typically done through what's known as a heat wheel. The preconditioned air and incoming air is separated into different plenum spaces, that are connected through the heat wheel. As the wheel rotates, it traps cooled preconditioned air and mixes with outside air, which in turn is cooled and dehumidified. Since the air is preconditioned as it enters the air handling unit the motor does not have to work as hard to meet the cooling demand from the building occupants. This also prevents the motor from cycling on and off because of the constant flow of cool air being received from the energy recovery ventilator. The more cool air transferred to the outside or return air, the more efficient the system becomes.

 

Conclusion

Energy recovery ventilators are a common sight in almost any green building. With these advances in technology and the necessity for more efficient mechanical systems, the demand for high efficiency equipment is greater than ever. Energy recovery ventilators seem to be here to stay, due to their proven performance, relatively low cost and easy maintenance. It will be interesting to see what the mechanical market will come up with next.

 

Waterless Urinals: Are the LEED Points worth the Cost of Maintenance?

            As a continuation to my last blog on recent trends in mechanical contracting, waterless urinals have taken over as the urinal of choice for building owners seeking LEED credit. Any Life Cycle Assessment will prove the savings one could expect from switching from conventional urinals, but many refuse to accept the proof because of the long term maintenance issues associated with waterless urinals. First there must be and understanding of what waterless urinals are, and how they operate.

How it Works.

            Unlike conventional urinals, waterless urinals do not come equipped with a connection for a flush valve. Waterless urinals in the U.S typically come in three styles. The first type of waterless urinal is the microbiological type. This model includes a block found in the waste outlet that contains spores which help break down the urine with bacteria which in turn helps eliminate odor. The next type of urinal is the check valve type. These models include a sealed valve that is similar to a one-way valve that is typically activated using gravity or can sometimes be spring operated. The last type of urinals are the barrier style. This particular model is unique as it utilizes a diaphragm that contains oil. The oil helps prevent odors as the urine is more dense than the oil.

Maintenance Issues

            One of the main issues with all waterless urinals is the maintenance aspect. The barrier style model is a prime example. If the oil in the diaphragm is not replaced often, users start to detect odors because there is no longer a shield against them. Many owners will forego waterless urinals just based on costs associated with maintaining them. Recently, I have noticed many owners have requested that a domestic water line be stubbed down in the wall directly behind the urinal, so it will be easier to replace the waterless urinal back to a flush valve model in a future retrofit. Owners uneasiness may come from the many horror stories about waterless urinals. As can be inferred by the name, waterless urinals use no water. That being said, that means there is nothing to flush out the urine to cleanse the copper soil piping. As urine sits in the copper piping, the ammonia from the urine attacks the piping causing corrosion to set in. In some cases, pipe actually cracks causing urine to be released behind the plumbing wall, which can lead to even more problems. This leaves owners wondering, is savings from utilizing waterless urinals worth the possible long term maintenance problems.

Conclusion

            Waterless urinals have been quite trend in recent years, but some might say the trend is coming to an end. Until manufacturers focus more on maintenance and reliability they will continue to see a loss in customers. Is this the end of waterless urinals? And if so, what is going to take its place.