Cost saving measures for aquatic facility operators

by Sally Bouorm | August 1, 2010 3:29 pm

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By Randy Mendioroz

With the increasing costs of energy, selecting equipment and systems to provide better operating cost efficiencies is extremely important to the long-term financial viability of any commercial aquatic facility.

First, the bad news. The annual operating cost for a typical 50-m (165-ft) outdoor commercial pool, including water, power, heating and pool chemicals, is about $307,538* per year. The largest expense is natural gas at $216,972 (71 per cent of the total cost). Electricity is next at $43,275 (14 per cent), followed by pool chemicals at $31,698 (10 per cent) and finally, water and sewer costs at $15,592 (five per cent).

In California, over the past few years, the cost of natural gas has increased from an average of $0.55 to over $1.00 per therm and the cost of electricity has jumped from $0.10 up to $0.15 per kilowatt hour. This means operating costs for a typical outdoor commercial pool have increased by more than $123,000 annually. Prices have risen similarly across North America, though not as severe.

What’s the good news? Today’s basic pool design strategies and cutting-edge energy alternatives are excellent at maximizing operating efficiency when planning a new aquatic facility or renovating an existing one.

Keep it pumping

At times, commercial aquatic consultants and contractors select the facility’s pool pump based on the primary factors of initial cost and availability. For example, a cheaper, readily available self-priming pump, which runs at a relatively high 3,450 revolutions per minute (RPM) may only operate at 55 to 60 per cent motor efficiency. However, if a lower RPM pump motor is selected, which runs between 1,750 to 1,150 RPM, motor efficiency of up to 85 per cent can be achieved.

One goal of energy-efficient design is to select pumps with a minimum 75 per cent motor efficiency. These pumps will initially cost more and must be installed at an elevation below the static water level of the pool being served. Another benefit to low RPM pumps is motor longevity, which can be twice that of their harder working counterparts.

Account for the variables

In addition to selecting more efficient pumps, the use of variable frequency drives (VFDs) can significantly reduce energy use associated with electric motors operating over extended time periods.

For example, in many jurisdictions, state and local health departments mandate the sizing of swimming pool circulation pumps for the worst possible condition (i.e. dirty filter conditions and a pump strainer full of debris). This means, when conditions are optimal, the circulation pump is oversized for the actual design condition. In some cases, health regulations mandate a 20-horsepower (hp) pump, when the actual design condition for 95 per cent of the operating hours would only require a 15-hp pump.

By connecting a VFD package to the pump motor and utilizing a highly accurate, digital flow meter that feeds back to the VFD, the operator can adjust the required flow rate as required by the health department. This allows the VFD to control the voltage to the pump motor based on the actual design condition.

If the filter is clean and the pump strainer is empty, the pump motor does not have to work as hard to deliver the required flow rate. Similar to a dimmer switch, the VFD can increase or decrease the horsepower as the conditions require, resulting in considerably higher motor efficiencies. VFD pump motor packages in the 10- to 20-hp range cost approximately $3,000 to $5,000; however, many pool operators have reported electricity cost savings between 30 to 50 per cent as a result.

In a recent case study, Chowchilla Union High School District (in California’s Central Valley) received an energy audit from Resource Solutions Group through their School Energy Efficiency (SEE) program for using a Smart Pump Control System (SPCS) advanced VFD package manufactured by H₂O Technologies. The table below shows the final costs, calculated energy savings and rebate amounts for the system. It also includes information on the simple payback (SPB), internal rate of return (IRR) and net present value (NPV), and shows the project will pay for itself in less than two years by providing the school district with significant utility cost savings.

Variable Frequency Drive Systems: Costs vs. Energy Savings
Measure	Installed	Rebate	Net	Annual	SPB	IRR	NPV
Name	Cost	Received	Cost	Savings
Pool VFD	29470	6880	22950	12900	1.8	0.61	157174

Get with the program

Every time a filtration system is backwashed, money is lost, not only from the water going down the drain, but the cost to heat and chemically treat the pool’s make-up water. Most aquatic facility filtration systems incorporate manual backwash, which means the pool operator backwashes the filtration system on a regular maintenance schedule, whether the system needs it or not.

By specifying filtration systems with micro-processor control, which can backwash based on pressure differential, the filter will only enter this mode when it measures an influent pressure (water within the filtration system) higher than a pre-set limit. For example, the system can be programmed to backwash only when the influent pressure is 69 kPa (10 psi) greater than the effluent pressure (water outside the filtration system).

Rather than operating on a regular maintenance schedule, an automated filtration system will only go into backwash mode when necessary, thereby saving water, heating and chemical treatment costs.

Expect more from a pool heater

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Pool heaters, while similar to traditional water-heating boilers, have historically been less than stellar when it comes to energy efficiency. However, since pool water is heated directly within the heater, they are capable of being more efficient than traditional plate-and-frame or tube-and-shell heat exchangers, which are connected to a central boiler plant. Within the past five to 10 years, pool heater manufacturers have greatly improved product efficiencies. In fact, pool heaters with up to 89 per cent thermal efficiency are more commonly available. Careful attention should be paid to the type of pool heater being proposed by the consultant or contractor.

Warming up to thermal blankets

One daily task, which can yield major savings for an aquatic facility, is the use of a thermal blanket. While some commercial pool operators may dislike the labour involved in removing and replacing a pool cover each day, the cost and energy savings are phenomenal when compared to a facility not using thermal blankets.

Studies on outdoor commercial pools have shown natural gas cost savings up to 50 per cent for operators who are dutiful in replacing pool blankets every evening. At an average capital cost of $3.50 per square foot of water surface area, thermal blankets can pay for themselves quickly.

A recent case study on the outdoor pool at the Lindsay Wellness Center in California revealed a $19,000 investment in thermal swimming pool blankets would lower annual energy costs by $35,158 (34.6 per cent) and reduce annual water consumption by 961,930 L (254,115 gal) or 34.5 per cent. The facility’s return on investment (ROI) was realized in six months. By using thermal blankets on one of the facility’s indoor pools, ROI was realized in a little more than six months.

Harness the power of the sun

Passive thermal solar systems typically utilize the existing swimming pool circulation pump to send water through a series of solar collectors—mounted on the facility’s roof or on a ground-support system—where heat is transferred from the sun to the pool water.

Downstream of the pool filtration system (but upstream of the pool heater), a bypass piping system is installed to route the pool water into the solar collectors.

When used in conjunction with a commercial pool heater, if the solar heating system can provide the necessary set point water temperature, the pool heater will not operate, thereby reducing its run time and associated natural gas costs.

Over the decade, commercial swimming pool operators have expressed a great deal of interest in solar heating systems. With utility rates spiking over the last few years, this interest has increased. Back when natural gas had a unit price of $0.55 per therm, proposing solar was less likely due to the eight to 10-year ROI and the average system’s 12-year life span. More recently, however, with natural gas prices hovering in the vicinity of $0.85 per therm, ROI can now be realized in four to six years, which is considerably more attractive to the average pool operator.

Of the systems studied, copper and glazed solar panels are the most efficient. However, these systems are less than ideal for commercial aquatic facilities due to the high potential for vandalism (e.g. kids tossing rocks and breaking the glazed panels). In addition, the high potential for imbalance pool water chemistry can wreak havoc within copper piping.

For example, if the pH feed system were to malfunction and drive the pH below seven, copper could precipitate out of the solar heating system and into the pool water, thus discolouring plaster to the point where it might have to be completely replaced.

For these reasons, the use of non-metallic solar panels (typically polypropylene [PP] or ethylene propylene diene methylene [EPDM] collectors) are preferred. These systems are less expensive than copper and glazed solar panel varieties and installation costs run approximately $12 to $18 per square foot (assuming suitable mounting space with proper solar orientation is available).

The amount of solar panels required varies greatly by region, but an average of 80 per cent of the water surface area is common for all but the most solar-challenged spots within North America.

For example, a 50-m (165-ft) outdoor commercial pool, would require approximately 929 m² (10,000 sf) of solar panels, with installation costs ranging from $120,000 to $180,000. However, with a potential annual operating cost savings of $50,000 to $75,000, a passive thermal solar heating system can be an attractive option for many pool operators.

See the light

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Another way to reduce an aquatic facility’s energy costs is to replace energy-consuming incandescent underwater lights with high-efficiency LED fixtures. They produce approximately the same amount of light as a 450-watt incandescent fixture, but provide energy savings of nearly 85 per cent.

Initial capital costs for LEDs are approximately double the price of incandescent lighting; each fixture costs approximately $1,000. However, an LED fixture will provide close to 50,000 more hours of light compared to its incandescent counterpart.

Avoid irritated swimmers

Chlorine is the most popular sanitizer for treating swimming pool water, but when it is not managed properly, swimmers can be put off by its obtrusive byproducts (e.g. odours and possible eye, nose and skin irritation). With a combination of adequate chemical control and a properly sized chlorine feed system, these byproducts can be eliminated.

Typical oxidation reduction potential (ORP) controllers have had difficulty maintaining proper chlorine levels to prevent formation of undesirable byproducts. However, by equipping an ORP controller with total water balance control and a part per million (ppm) residual analyzer, chlorine smells and byproducts can be prevented. This state-of-the-art control system should be accompanied with properly sized chemical-feed equipment.

An aquatic facility that uses a salt chlorine generating system, which produces sodium hypochlorite onsite, can offer patrons an alternative to traditional chlorine. Non-iodized table salt, or sodium chloride, is added directly to the swimming pool; dosing levels range from 3,000 to 5,000 ppm. In comparison, human tears have a salinity of 7,200 ppm, while sea water has a salinity of 36,000 ppm. As such, the salt concentration in the swimming pool is relatively low and patrons would not smell, taste or feel the salt.

Despite relatively high capital and maintenance costs, salt chlorine generation reduces or eliminates the storage and handling of chlorine and other chemicals; eliminates the hassle and cost of purchasing liquid chlorine from a vendor and having it delivered; and producing pool water with a more natural, smooth feel. Many aquatic facilities in Europe use salt chlorine generation.

A well-designed chlorine feed system will improve the efficacy of any system including salt chlorine generation and liquid or tabletized chlorine feeders. In cases where a standalone salt chlorine generation system is prohibited by capital cost or mechanical space, a hybrid system can be designed to ensure pristine water quality. With a hybrid unit, a chlorine feed system can be designed to backup the salt chlorine generation system and provide a reliable, quality-controlled chlorine feed system.

What does the future hold?

Increasing utility costs will require aquatic facilities to either scale back operations or adopt energy-efficient pool design strategies. Even though initial capital costs for these technologies may be higher, commercial pool operators should embrace them as they can provide a worthwhile ROI.

Note: *All figures expressed in U.S. dollars.

 

Randy Mendioroz is a principal with Aquatic Design Group in Carlsbad, Calif., a consulting firm which specializes in the programming, planning, design and engineering of competitive, recreational and leisure-based aquatic facilities. He can be reached via e-mail at rmendioroz@aquaticdesigngroup.com[4].

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