solar pool heating: open-loop vs closed-loop
TRANSCRIPT
Distributed Solar Thermal:Rebirthing a Mature Technology
Pool Heating - “Open Loop” vs “Closed Loop”
Dave Sizelove, President & CEOAquatherm Industries, Inc.
Heated67%
Unheated33%
Heated vs Unheated
Heated with natural gas...
CO2 emissions = 6.6 MILLION cars
(driven 12,500 miles annually)
• 5,000,000 In-Ground Residential Pools
• 400,000 Commercial Pools
The MarketIn the United States alone there are...
Outdoor60%
Indoor40%
Indoor vs Outdoor
The SolutionA hybrid solar pool heater consists of...
✓The most cost-effective primary heater(Solar is free heat from the sun)
✓The existing natural gas, propane orelectric pool heater for anytime heat(for times when solar will not be enough)
Goal:
To engineer a “reasonable balance”
between cost and BTU heat collection
from solar.
Projected Energy Savings w/ Hybrid Solar Pool Heater:
Year-round Pool: 40-60% Seasonal Pool: Up to 100%
System TypesOpen Loop: Closed Loop:
Direct heating with Low-Temperature Unglazed Polymer Collectors
Indirect heating with a heat exchanger usingMedium-Temperature or Evacuated-Tube Collectors
Existing Pump & Filter
Controller
Collectors
ExistingHeater
Open LoopOpen Loop:
Direct heating with Low-Temperature Unglazed Polymer Collectors
Existing Pump & Filter
Controller
Collectors
ExistingHeater
Benefits
✓ Designed to economically raise temperature of large volumes of water (like a pool)10-15o F above ambient air temperature.
✓ Specifically designed for low-temp applications like pool heating; inexpensive PVC for feed/return lines.
✓ Approx. Cost - $15-20 per sq. ft. (commercial).
Considerations
‣ Little or no performance when ambient is more than 25o F cooler than pool water temperature.
‣ Sensitive to areas with a cool prevailing breeze.
‣ Life expectancy of 15-20 years
Closed LoopBenefits
✓ Good year-round performance, especially incooler, northern climates.
✓ Less sensitive to cool prevailing breezes.
✓ Life expectancy of 20-25 years.
Considerations
‣ Performance losses of 17-25% due to glazingand use of a heat exchanger.
‣ Feed and return lines must be insulated copperto prevent heat loss from higher temps generated.
‣ Approx. Cost - $80-100 per sq. ft. (commercial).
Closed Loop:Indirect heating with a heat exchanger using
Medium-Temperature or Evacuated-Tube Collectors
Case StudiesAnnual Savings Comparison Based on D.O.E. RSPEC Program Simulations
Portland, OR
Dallas, TX
Washington, DC
Chicago, IL
Atlanta, GA$12,620
$11,421
$11,953
$14,375
$9,290
$11,445
$8,516
$9,969
$13,360
$6,725
Open Loop Closed LoopAnnual Average Savings
Based on:
‣ 4,000 sq. ft. indoor pool
‣ 80o F pool temperature
‣ 82o F room temperature
‣ 50% room humidity
‣ $1.00 per therm
‣ 75% efficient heater
‣ 3,000 sq. ft solar area
‣ $15 / sq. ft. open loop
‣ $80 / sq. ft. closed loop
Case StudiesComparative Payback Analysis Based on D.O.E. RSPEC Program Simulations
0
5.4167
10.8333
16.2500
21.6667
27.0833
32.5000
Portland, OR Dallas, TX Washington, DC Chicago, IL Atlanta, GA
19
2120
17
26
4553
7
Open Loop Closed Loop
Payb
ack
Peri
od (
in y
ears
)
Based on:
‣ 4,000 sq. ft. indoor pool
‣ 80o F pool temperature
‣ 82o F room temperature
‣ 50% room humidity
‣ $1.00 per therm
‣ 75% efficient heater
‣ 3,000 sq. ft solar area
‣ $15 / sq. ft. open loop
‣ $80 / sq. ft. closed loop