University of IdahoCollege of EngineeringMoscow, ID 83844

December 9, 2005

Attn: xxxxxxxCity of Kendrick808 RailroadP O Box 195Kendrick, ID 83537

RE: Hybrid Pool Heating System

Attached, please find a final report for the hybrid pool heating system. The recommended hybrid heating system in the attached report is recommended to meet the needs of the citizens of Kendrick and the outlying area while balancing budgetary restrictions.

This report outlines the steps taken during the design process, including the selection and description of the final design recommendation. In addition, the report also lists several pre-implementation items that need to be resolved before the hybrid system should be installed.

Thank you for the opportunity to work with and learn from you during this project. Your inputs and feedback were an integral part of directing the team to a successful conclusion.

If you have any questions, concerns or wish to discuss details of this project, please feel free to contact us.

Respectfully Submitted,

Team iHeat

City of Kendrick

Team iHeatUniversity of Idaho

Hybrid Pool Heating System

Table of Contents

Page #

EXECUTIVE SUMMARY.......................................................................................................xxx

1 INTRODUCTION....................................................................................................................x

1.1 Purpose...........................................................................................................................x

1.2 Reasons For This Report................................................................................................x

1.3 Background....................................................................................................................x

1.4 Problem Definition.........................................................................................................x

2 CONCEPT DEVELOPMENTS.............................................................................................x

2.1 Current State Investigation............................................................................................x

2.2 Pool Modeling with RETScreen....................................................................................x

2.3 Heating Solution Development......................................................................................x

3 FINAL SOLUTION DESCRIPTION....................................................................................x

3.1 Detailed Hybrid Solution...............................................................................................x

3.1.1 Propane Furnace Component.............................................................................x

3.1.2 Solar Array Component.....................................................................................x

3.1.3 Pumps, Pipes, and Valves..................................................................................x

3.1.4 Controller...........................................................................................................x

3.2 Operating Procedure......................................................................................................x

3.3 Winterization..................................................................................................................x

3.4 Economic Summary.......................................................................................................x

3.5 Solution Evaluation........................................................................................................x

4 CONCLUSIONS.....................................................................................................................X

5 RECOMMENDATIONS FOR FUTURE WORK...............................................................X

RESOURCES................................................................................................................................X

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APPENDIX A – XXXXXX...........................................................................................................X

APPENDIX B – XXXXX..............................................................................................................X

APPENDIX C – XXXXX..............................................................................................................X

APPENDIX D – XXXXX..............................................................................................................X

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Executive Summary

Team iHeat designed a hybrid heating system for the Kendrick City Pool to make it such that the city will be able to open the pool during the Lotus Blossom Festival. The hybrid system has three main components: heating with both propane and solar, and upgrading to a thermal pool cover. Using these three components makes for an efficient way to initial heat the city pool and sustain originally obtained temperatures.

During the design process, the recommended hybrid system evolved as we quickly came to the conclusion that there was not a stand-alone solution for the given goal with perceived budget constraints. Although city officials had stated that they would like to have a purely solar heating system, such system would not meet their opening date deadline. We recommend initially heating the pool water with propane and, once the desired temperature is reached, switch to a pure solar system for water circulation heating, and adding a thermal pool cover to, in essence, add a protective lid on the heated water to mitigate heat loss from the pool’s surface.

Also during the design process, Team iHeat found some installation deficiencies in the current pool heating system, as well as a water leak, both of which have been brought to the attention of city officials, and both being top priority fixes before the hybrid system is introduced.

Overall, the final design meets the opening date goal, and is an inexpensive introduction into the pool heating system.

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CITY OF KENDRICK: HYBRID POOL HEATING SYSTEM

1 INTRODUCTION

1.1 PurposeThis report details a hybrid pool heating solution designed by Team iHeat of the

University of Idaho for application at the City of Kendrick municipal pool.

1.2 Reasons For This ReportThe City of Kendrick has funded research to develop a pool heating solution, part of

which included construction and testing of solar collectors designed by Team iHeat at a cost of $500. This report will provide details on the results from construction and testing as well as determine if these collectors can serve as a component of the hybrid solution which will be developed hereafter.

1.3 BackgroundThe City of Kendrick in Kendrick, Idaho is investigating a low cost heating system for

the municipal pool to provide comfortably swimmable water temperatures by the annual Kendrick Locust Blossom Festival, which is held the last weekend in May. City officials contacted the Engineering Department of the University of Idaho for aide in finding a reduced cost solution through innovation when compared to an off the shelf solution. Team iHeat, a group of senior engineering students, were assigned the request from Kendrick officials as a senior design project in the capstone senior design course offered at the University.

Currently, the city pool opens during the second week of June with temperatures around 75° F. This is two weeks after the Locust Blossom Festival and on the cold end for a comfortably swimmable pool. The pool was originally constructed in 1948 and was designed without a water heating system. Since then, the pool has been renovated twice: once during the 1980’s and again in 2008. Neither renovation included the addition of a heating system; however, the 2008 renovation did include some plumbing for a potential solar heating system.

With the addition of a heating system, Locust Blossom Festival could conveniently expand activities to include the pool as it sits centrally located at Kendrick Memorial Park. This would further enhance the attraction of the Festival to persons of all ages and increase the utility of the pool by expanding the season to include this popular community event.

1.4 Problem Definition

Design an efficient, inexpensive, and controllable system to heat the City of Kendrick's municipal pool to swimmable temperatures by the annual Locust Blossom Festival.

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iHeat met with city officials to determine the basic needs for a pool heating system. These needs were detailed in Table 1.1. These needs and target specifications allowed iHeat to begin defining a heating solution.

Table 1.1 The discussed needs of a pool heating solution.

Needs General Detailed Target SpecificationsSafety Temperatur

eNo scalding water Heated water return <25° F increase

Cleanliness Filtration Same filtration rate or betterPool safe materials Good chemical resistance, non-toxic

Failure Safe shutdown Appropriate breaker circuits and valves.Resource Energy Minimal Cost to run an additional pump

Capital Low cost <$10,000 initial cost and <$1000 yearlyTime Pool Season Opening day Locust Blossom Festival

Time to heat 2-3 weeks before openingService Life Heating System 15 years and recyclable

Comfort Temperature

Heating Heat 130,000 gallon pool to 78-82°F Cooling Heating system shutdown , allow cooling

Interface Human Interaction

Temperature control

Lifeguards and maintenance personnel

Isolation Protected from pool usersVisual Appearance Aesthetically pleasing to pool users

Size Fits within the pool site surroundings/pump room

Maintenance Repair Materials Available at local hardware stores or easily obtainable otherwise

Expertise Serviceable by city maintenance personnel

A major consideration for this project was the availability of volunteer labor and community involvement. iHeat was counseled to use its discretion in finding a solution that meets target specifications and was advised from city officials that volunteer labor could be leveraged in reaching this solution.

2 CONCEPT DEVELOPMENTS

2.1 Current State InvestigationiHeat developed a schematic diagram of the current pool piping system to better

understand how a heating solution would integrate with existing equipment (see appendix BLAH). The components of the current system were identified and reference documents were retrieved for many of them. These include operating manuals for the primary pump, surge tanks, sand filters, chlorination system, flow meter, and water level system (see appendix BLAH). Considerable time was spent observing the pool in operation to better understand how each of these pool components interacts with one another.

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An investigation of the current state of pool usage yielded the following conclusions:

The surge tanks are operating at near full capacity The sand filter water supply and return piping is incorrect The flow meter is located too close to a pipe elbow and is unable to take an

accurate reading The pool has a 3000-5000 gallon per day leak A more regimented cover usage scheme could be employed The pool is about 50% shaded by trees during the proposed warm up time

2.2 Pool Modeling with RETScreenThe Department of Energy (DOE) has provided guidance for pool operators regarding

heating saying: “You can significantly reduce swimming pool heating costs by using a pool cover” [1: 1]. Research indicated that evaporation was the major factor in pool heat loss and the DOE confirmed this stating that “Covering a pool when it is not in use is the single most effective means of reducing pool heating costs” [pg. 2]. The municipal pool currently employs a blue translucent bubble type thermal cover. This cover is used from on average 10 hours each day during the pool season, with the exception of the initial warm-up period in which 24 hour coverage is typical. Initial fill-up of the 130,000 gallon pool occurs near mid May with ground water at 52° F.

Given the current state conditions of the pool, iHeat conducted a study using NASA climate integrated with RETScreen clean energy analysis software which showed a need to provide additional heating from any number of solutions in order to reach 78° F water temperature by the end of May. This study provided projected water temperatures which were in good agreement with actual pool temperature measurements recorded by pool personnel over the previous two years. RETScreen also estimated the required BTUs to bring the pool to 78° F. Team engineers also performed a thermal analysis of the pool by hand given the average ground, air, and feed water temperatures from the climate data as well as the dimensions of the pool and found good agreement with the BTU figure recommended from RETScreen (See appendix BLAH RETScreen model and the propane used under 100% gas).

2.3 Heating Solution DevelopmentThermal modeling of the pool shows 28 million BTUs are required for warm-up from

52°F to 78 (see appendix BLAH). Non-traditional methods of heating including temperature sensitive paint, friction turbines, biomass, and unique solar covers were considered. Each of these were cost prohibitive and/or outside of the scope of this project and a heat output rating remained unknown for each case. The bubble type cover currently in use had no significant inexpensive alternatives that could provide significant improvements in solar heat gain or insulation; therefore, the cover would not be changed.

iHeat investigated purchase costs for traditional commercial solutions including propane gas heaters (natural gas is not available), electric heat pumps, and solar water heating panels.

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The typical costs associated these solutions are detailed in Table 1.1 along with the expected lifetime of each solution.

Table 2.1 Observed costs by iHeat for common commercial heating solutions

Heating solution

Purchase cost

Yearly operating expense

Lifetime Initial warm-up time

Installation cost

Propane, 1.2 Million BTUH

15,000-$20,000 1000-$1500 7-10 years 24-48 hours $2000

400k BTUH Heat Pump $15,000 $1000 10-12

years 4 days $2500

2400 ft2 Fafco solar panel

array

16,000-$20,000 200-$400 10-15

years 2-3 weeks5-$15,000

Supplier recommendations for gas heaters are typically sized for a warm up time of 24 to 48 hours, while solar solutions project 2-3 weeks. This relatively short warm up time for a gas heater in comparison to the solar option comes at a high cost. In a phone interview with Raypak Inc. Customer Service, a pool heater manufacturer, iHeat learned the large heater recommendation and accompanying short warm up time is to allow the heater to minimize temperature swings during times of high usage where evaporation causes significant heat loss in a period as short as one day. City Mayor Dale Lisher and lifeguard personnel indicated the temperature swings as reported by lifeguard personnel were as much as 8 degrees depending on pool usage.

iHeat investigated SunSaver solar pool heaters manufactured by Fafco, a leading commercial manufacturer of solar water heating panels. This product averaged $7 per square foot from most pool suppliers. A brochure of this collector is included in appendix BLAH. iHeat toured an installation of these at Dayton, Washington, which has a pool comparable in size to that of Kendrick. Several photos of the Dayton solar collector array are included in appendix BLAH. iHeat was advised by Dayton maintenance personnel that the array mounting expense was a significant part of the total cost, though city hall was unable to provide supporting documents of the actual expense.

Solar water heating panels for pool heating are constructed of highly UV resistant dark colored plastics. The panels are not insulated which produces excellent performance when ambient air temperatures rise above pool water temperatures, which is usually the case during the typical swimming season (late spring to late summer). iHeat brainstormed two designs that could possibly be constructed by unskilled volunteer labor from readily available materials that maintain the same highly UV resistant property. These designs were a coiled poly tube and twinwall polycarbonate. Both designs were constructed and tested to evaluate feasibility as replacements to the commercial collector option considered earlier. An in depth investigation of these two designs is detailed in a supplementary report (appendix Blah). In summary, the coiled poly hose design was easily constructed from UV resistant tubing, provided efficiencies 20% less

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than the commercial option, but at a 77% reduction in cost over the Fafco SunSaver panel considered earlier. Testing of this design should continue as per recommended in the supplementary report.

Through continued modeling with RETScreen, iHeat investigated hybrid gas-solar or heat pump-solar solutions. The results of this study provided several key advantages over the 100% solar or propane solutions and are summarized below.

Table 2.2 Comparison of a hybrid solution with solar and gas/heat pump options.

Solution Advantages Disadvantages

Hybrid

Solar array size can be integrated on existing site structures, less expensive traditional heater, reduced booster pump size, guaranteed heat up for Locust Festival, expandable for more solar in the future.

Requires good control, winterizing,

Solar

Uses free solar heat, no pollution, low maintenance cost

No guarantee open date, large booster pump required, amount of site preparation for (2400 ft2), solar controller, setup, winterizing, expensive initial cost, controller.

Gas or heat pump

Guaranteed heat up. More simple control than solar.

Expensive initial cost, expensive annual energy cost, shortest life, can pollute.

The original warm-up time specification was 2 to 3 weeks, iHeat decided keep the time to 5 days maximum to reduce heat lost to the surroundings before the pool is opened. The electric heat pump option typically have about a $13,000 initial cost for a 400k BTU/hr rated heat pump system, which runs 4 similar heat pumps in parallel to reach the final rating. iHeat could not find a single heat pump with a rating much higher than 100k BTU/hr. Running 4 separate heat pumps seemed cumbersome and possibly problematic long term as they must be serviced by an HVAC technician. Heat pumps would also have to be installed on the north end in a well ventilated area but still be protected from pool users. Maintaining 4 separate units that have high initial costs was unconvincing.

In summary, the hybrid option was most appealing as it could guarantee an opening date for the pool, use a less expensive heater or furnace for just the initial warm-up period over 4 to 5 days, and allow the solar array and existing cover to provide the heat maintenance after warm-up to maintain swimmable temperatures while reducing temperature swings noted earlier. The initial indications from RETScreen showed the solar array size could be reduced 75% because it was no longer required to provide warm-up.

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3 FINAL SOLUTION DESCRIPTION 3.1 Detailed Hybrid Solution

The key benefits of a hybrid solution for the Kendrick municipal pool are reduced initial and annual costs, visual site improvement, guaranteed opening date, and warmer spring and late summer temperatures. A schematic of the proposed solution is included in BLAH. A simplified schematic of the hybrid solution is shown below.

INSERT SIMPLE HYBRID SCHEMATIC HERE.

3.1.1 Propane Furnace ComponentA single propane furnace cost, rated at 400k BTU/hr, ranged from 2500 to $3000. With

this rating the pool warm-up time is 4 days and would burn about 370 gallons of propane (see appendix BLAH). The propane unit will fit in the existing pump room space near the old pump location. The supply tank can be rented from Clearwater Power, which currently fills the city firehouse tank adjacent to the pool. Jim from Clearwater Power estimated the cost of running the supply lines at $1500, however, an on-site survey would be necessary.

3.1.2 Solar Array Component Initial warm-up provided by the propane furnace dramatically reduces the size of array

required for heat maintenance as was stated earlier. Modeling with RETScreen shows just 392 ft2 would be required (see appendix BLAH) . iHeat chose the concrete bleacher structure on the north end for placement of the array. Not only would this greatly reduce the ground preparation necessary for the array but it would make use of an area that is currently unsafe for sitting, is partly fenced off already, and forms an excellent angle to the sun. This concrete covers a diagonal area of 380 ft2. Using 12 (4’ x 8’) Fafco SunSaver panels the array cost is totals just over $3000 at $260 per panel.

Mounting………….iHeat custom panels………..

3.1.3 Pumps, Pipes, and Valves Approximately 150 feet of 2” PVC would be necessary to supply water to and from the

solar array. This piping would need to be routed into the existing pump room where a booster pump is located. This pump is only allowed to run when the main pump is operating as well as when told by the controller that the solar array can generate useful heated water.

3.1.4 ControllerA solar controller can automate use of the array by running water through it only when it

can generate useful heated water. When the water in the array reaches a minimum temperature above the current pool temperature the booster pump is activated to begin pumping heated water to the pool. The controller senses temperatures from the pool, solar array, and ambient air and determines whether to activate these heating systems without user intervention.

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This controller would be located in the existing pump room and interfaces with the booster pump and solenoid actuated valves. It also can interface with the chlorination system is so desired.

There are many commercial controllers to choose from. iHeat recommends one that can support the current rating of the booster pump and that has a manual override. An example of an excellent controller is a Goldline PL-PS-4. Prices range from 800 to $2000.

3.2 Operating ProcedureThe general operating procedure for the hybrid gas-solar solution calls for a gas heater to

provide initial warm-up over 4 to 5 days. After warm-up the gas heater is turned off for the season and the solar array, with the aid of the bubble cover, maintain pool temperatures for the remainder of the pool season. With a good controller, all operating procedures will take place automatically.

3.3 WinterizingThe solar array should be completely drained of all water at the close of the season

otherwise significant damage could occur. The solar array installed in Dayton had to have one of the main supply pipes replaced which was believed to be empty after opening the end valves. Compressed air should be used as long as it remains below the recommended pressure for the solar panels. iHeat sees the possibility of freezing as the major mode of possible system failure.

3.4 Economic SummaryINCLUDE GRAPHS FROM KELBY

Table 3.1 – Costs of Components of Heating System

Component Detail Initial Cost Annual CostPropane Heater 400k Btu/h heater installed $4000 $1000

Solar Array Fafco SunSaver $3000 $0Pump, piping, and

valves$1500 $100

Controller $1000 $0TOTAL 9500 $1100

3.5 Solution EvaluationREITERATE WHY THIS WORKS AND MEETS THE SPECS. WHY USING

iHEAT PANELS MIGHT SAVE THEM A FEW BUCKS.

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4 CONCLUSIONSCONCLUSIONS HERE

5 RECOMMENDATIONS FOR FUTURE WORKCONTINUE PANEL STUDY INTO THIS SPRINGSite improvement and design implementation PLAN OVER THE NEXT 2 years-REGIMENT COVER USAGE, INSTALL GAS HEATER….SEE IF THE SOLAR

IS STILL NEEDED THAT BADLY

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RESOURCES

[1] U.S. Department of Energy (). Energy Savers: Your home. Swimming pool

heating- pool covers page. Mar. 24, 2009. [Online]. Available:

http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13140.

[Accessed December 11, 2009]

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