New dehumidifier technologies

by Sally Bouorm | October 1, 2012 11:31 am

By Ralph Kittler

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A myriad of new energy-reduction and environmentally friendly dehumidification technologies have been introduced to the indoor swimming pool market in the last 10 years. These innovations not only provide significant advancements in system performance and reliability, but also considerably reduce operating expenses. These systems also provide natatorium owners/operators a quick return on investment (ROI), which has prompted more facilities to consider upgrading their existing dehumidification equipment even before its useful lifecycle is over. For new construction projects, these systems can potentially save hundreds of thousands of dollars over the equipment’s lifecycle.

Today, a natatorium design team that is simply considering a basic dehumidification unit could still be looking at a system with significantly upgraded components and features compared to what was available even five years ago. Therefore, before considering adding features and options to the base model, designers should evaluate the higher upfront capital cost with the energy savings over the product’s lifecycle.

The dehumidification equipment innovations discussed below are not budget busters and can potentially provide a quick ROI. In fact, many manufacturers include the following features in their base model.

Fan technology

The introduction of direct-drive plenum fans with variable-frequency drives (VFDs) is one example of a new energy-saving technology. These fans deliver air more efficiently than centrifugal-style fans, which are common in traditional dehumidification systems. In comparison, the direct-drive approach provides greater efficiencies with significant energy reductions and less maintenance. While this technology has existed for many years, it was only recently introduced to the dehumidification industry.

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Before this, state-of-the-art was the age-old concept of fan belts connecting the fan motor to the blower, a method which needs regular adjustments and belt replacements. Conversely, the direct-drive method connects the motor directly to the fan shaft, thus eliminating friction, noise, maintenance and power transfer inefficiencies.

When VFDs are added to the mix there is further potential for greater efficiencies with the ability to ramp fan speed up or down, which also adds more flexibility for air balancing. Another potential advantage is the ability to ramp down the plenum fan speed during off-peak hours when less overall supply airflow might be a consideration.

A direct-drive plenum fan with VFD can reduce fan motor energy consumption by as much as 15 per cent. Considering the fans on an aquatic facility’s dehumidification equipment operate 24-7, energy savings over the equipment’s lifecycle can be significant. The payback is instantaneous since this technology is comparable in price to belt-driven systems.

Energy recovery: Using exhaust air to preheat outdoor air

All commercial buildings must bring in outdoor air as mandated by local building codes. These codes are generally based on the recommended values from American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard-62, Ventilation for Acceptable Indoor Air Quality (IAQ).

In the winter, heating cold outdoor air to at least 26.6 C (80 F) just to get it neutral to the indoor air temperature can be expensive. ASHRAE also recommends that an indoor pool’s exhaust air be used to keep the space at a slight negative pressure to assure potentially destructive indoor air, which contains moisture and often chemicals, is not accelerated through the natatorium’s walls or doors leading to other non-pool areas in the building. Therefore, the volume of exhaust air must always exceed the amount of outdoor air. Fortunately for natatorium operators, humid and warm exhaust air is extremely energy rich and ideal for energy recovery, allowing it to be used to preheat the code-required outdoor air.

Energy recovery from exhaust air to outdoor air is an option available from some dehumidifier manufacturers. The exhaust air is warm (minimum 26.6 C [80 F]) and its energy can be recovered and used to preheat the incoming outdoor air, via heat exchangers. Using recovered heat from the exhaust air can cut outdoor air heating costs by 50 to 75 per cent.

Additionally, preheating outdoor air minimizes potential for condensation inside equipment in cold climates. Introducing freezing cold outdoor air into a dehumidifier could theoretically generate snow inside the unit.

The ROI for this type of dehumidification system is often only a few months and rarely more than a few years, which makes it a cost-effective investment for most natatoriums. When considering which form of heat recovery to use, it is important to consider performance, longevity and impact on equipment size. At a minimum, the heat recovery device used to extract heat from the chemically laden exhaust air should be provided with the best possible corrosion protection coatings.

Remotely located exhaust fans can also be outfitted with heat transfer coils that are piped to the dehumidifier. Designers and operators should always consider exhaust air as an energy source for heat recovery.

Heat recovery: Using recovered energy for free pool water heating

Recovering heat from the refrigeration circuit’s compressors to provide free pool water heating is not a new technology. In fact, it is one of the major founding principles of the earliest mechanical dehumidifiers. Before mechanical dehumidifiers were developed in the ’70s, indoor pools generally attempted to control relative humidity levels by simply exhausting this energy-rich air and replacing it with outdoor air. Those early pools were forced to heat the pool water with conventional gas or electric heaters. However, using recovered energy from the compressor’s waste heat to provide pool water heating has made the mechanical dehumidifier a more efficient method for operating indoor pools. This is another option that typically shortens the ROI period and should always be considered.

ASHRAE’s Energy Standard 90.1, Energy Conservation in New Buildings Except Low Rise and Residential Buildings, has taken the energy recovery requirement a step further by mandating heat recovery or the use of a pool cover. In fact, some states in the U.S. have adopted this standard into local code requirements. The standard calls for a pool cover for commercial indoor pools using conventional pool heaters unless “over 60 per cent of the energy for heating comes from site-recovered energy.” The pool water heating option on mechanical dehumidifiers easily satisfies this requirement. Therefore, this option not only saves energy, but can also help satisfy local code requirements and possibly eliminate the need for a pool cover.

Remote monitoring for optimum performance

Dehumidifiers are no different than a car, computer or residential air conditioner, because they all need regular maintenance and calibration to ensure optimum performance. Allowing any system to limp along outside of its optimum operating conditions costs the operator money.

Dehumidifiers control much more than just room temperature as would traditional heating, ventilation, and air conditioning (HVAC) equipment, so their optimum performance is critical to minimizing operating costs. At a minimum, a factory-trained technician should be servicing and adjusting the system a few times a year. For example, if an operator was not aware the pool’s water flow was not getting to the dehumidification system, the unit would not be able to heat the pool water with its recovered energy. In a large facility, this could cost the operator tens of thousands of dollars in free pool water heating annually.

To help operators realize the best possible system performance and lowest possible operating cost for the life of the equipment, some units even feature an on-board monitor/control microprocessor that is capable of sending the dehumidification equipment’s vital operating statistics via Internet to the manufacturing facility. These manufacturers offer a free daily monitoring service and even have ‘smartphone’ applications where an authorized user can access a unit remotely.

This technology also allows the manufacturer to alert a facility manager to any issues as well as help service contractors set up and adjust the unit to ensure optimum performance. In the event of an alarm, troubleshooting can be assisted by a factory engineer, which ensures a quick resolution to any problem.

Keeping the dehumidifier finely tuned to its intended performance parameters will result in further energy and ownership savings over the life of the equipment.

Using a dehumidifier for space cooling and heating

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Residual effects of the dehumidifier’s refrigeration circuit can also be used to cool and partially heat the pool area. The dehumidification process cools the air to condense moisture; during the cooling season this cool dehumidified air can provide year-round comfort without additional operating costs.

These systems can help to heat the space as well. Once again, this is accomplished by recovering heat generated by the compressors. If a pool space needs heating and the pool water heating requirement has already been satisfied, that same heat recovery can be used to partially or totally heat the space. On extremely cold winter days, the building’s conventional heating system will be required to maintain the set point temperatures for the space; however, the first stage is to use all of the heat the compressor generates.

Economizer mode

The economizer concept is not new in the HVAC industry either. Traditional HVAC systems with economizer modes use outdoor air to cool the indoor space. Indoor pool facilities, however, are a little more complicated as outdoor air is used to cool and control the space humidity levels simultaneously. For this to happen, the outdoor air needs to be mild and dry; therefore, the window of opportunity for this mode varies based on geographic locations.

The more humid the location, the fewer days this mode can be used. Larger systems often have a purge setting, which puts the system into 100 per cent outdoor air mode for a few minutes to remove the gaseous pool water chemicals out of the space. A system like this can provide economizer operation for no extra cost. If the outdoor conditions are right, setting the dehumidification equipment to the economizer mode results in free cooling and humidity control. The unit’s microprocessor controller normally monitors the outdoor and indoor conditions and will activate this mode automatically when conditions permit.

LEED and green advantages

For new construction projects, a dehumidifier with many of the aforementioned energy reduction advantages can deliver significant credits in the Leadership in Environmental and Energy Design (LEED^®)[4] program. Additionally, there are possibilities of receiving government incentives and utility rebates for strategies that reduce energy use.

Natatorium dehumidifiers offer more than just LEED credits for energy reduction, however. Water conservation is also a major consideration. Dehumidifiers generate significant amounts of condensate, which can be collected and returned to the pool, saving thousands of litres of water annually. The condensate is clean and nearly potable; yet, its acceptance varies according to local codes. At a minimum, this can be added to the ‘grey water’ reclaim. Condensate return strategies can often amount to one entire pool fill annually.

Additional LEED credits can be accumulated as a result of addressing IAQ measures such as high minimum efficiency reporting value (MERV) air filter materials and reduced refrigerant system charges.

Reducing refrigerant use

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Since the Kyoto Protocol global environmental treaty in 1997, ozone-depleting chlorofluorocarbon (CFC) refrigerants such as R-11 (trichlorofluoromethane) and R-12 (dichlorodifluoromethane) have been phased out and replaced with more environmentally friendly options such as R-410A (a mixture of difluoromethane and pentafluoroethane) and R-407C (a mixture of hydrofluorocarbons).

While these newer refrigerants are less harmful to the environment (i.e. ozone depletion), they can cost up to 10 times as much as the refrigerants they replaced. They also comprise blends of two or three refrigerants, which need to be in exact concentrations to ensure optimal HVAC performance. Further, operators are also faced with more expensive and challenging onsite refrigerant-related service issues. When compared to air conditioning systems, this becomes more significant because traditional indoor pool dehumidifiers have considerably larger refrigerant charges. Until recently, most large community indoor pools, YMCAs, and school natatorium dehumidifiers would have systems with hundreds of kilograms of refrigerant in their circuits; therefore, a refrigerant leak could easily cost thousands of dollars in replacement costs alone.

In terms of new indoor aquatic facility construction, designers are also faced with additional considerations regarding compliance to American National Standards Institute (ANSI)/ASHRAE Standard 34-1010, Designation and Safety Classification of Refrigerants, and ASHRAE Standard 15-2010, Safety Standard for Refrigeration Systems, regarding safe refrigerant concentration limits in occupied spaces.

When considering these challenges related to new refrigerants and mandates, by far the most important innovation in dehumidification equipment has been the recent move toward refrigerant reduction. Rather than using a conventional ‘split system,’ where refrigerant is piped outdoors to a remote air-cooled condenser, these systems now reject heat into a propylene glycol fluid loop, which then goes outdoors to an air-cooled heat exchanger called a dry-cooler. Propylene glycol is environmentally friendly and 95 per cent less costly per kilogram than today’s refrigerants. Further, a refrigerant charge can now be reduced by as much as 85 per cent compared to conventional dehumidifiers.

Although new to the indoor pool industry, this dehumidification technology has been used in computer room air conditioning systems and environmentally sensitive areas for a number of years.

Innovations to consider

Today’s advancements in dehumidification equipment design offer natatorium operators and owners unprecedented performance, reliability and energy savings. Further, these innovations contribute to increased operating efficiencies, five to seven per cent for normal days (under 35 C [95 F]) and the same overall efficiency on the hottest summer days (above 35 C).

Therefore, natatorium operators and owners should consider these new technologies when analyzing their current equipment’s efficiency, environmental impact and overall operational costs. A new dehumidification system could have an attractive ROI and deliver better overall performance.

Ralph Kittler, PE, is co-founder and vice-president of sales and marketing at Seresco Technologies Inc., an Ottawa-based manufacturer of natatorium dehumidifiers. He has 23 years of experience in the heating, ventilation, and air conditioning (HVAC) industry and a degree in mechanical engineering from Lakehead University in Thunder Bay, Ont. Kittler is also an American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) ‘Distinguished Lecturer’ and technical committee 9.10 reviser for Chapter 25, Mechanical Dehumidifiers and Related Equipment in ASHRAE’s 2012 Systems and Equipment Handbook, and technical committee 9.8 reviser for Chapter 5, Natatorium Design in (Large Building Air conditioning Applications) in ASHRAE’s Applications Design Handbooks since 1999. He can be reached via e-mail at ralphkitter@serescodehumidifiers.com[6] or by visiting www.serescodehumidifiers.com[7].

Source URL: https://www.poolspamarketing.com/trade/new-dehumidifier-technologies/

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