Proposal for a Domestic Hot Water System

Researched by David Luong, Mark Piper, Colton Bangs, Aloysius Obodoako, Disha Katharani

Advantages of a Solar DHW System

• Off-grid capability– Ideal for isolated areas where connection to

grid power is difficult to impossible

• Renewable energy source– System completely powered by solar radiation– Savings in long term investment

System Requirements

• Family Size of 3-4 needing 80 gallons of hot water per day

• Maximum storage tank temperature of 120 degrees F

• Average of .63 kW-hrs per day– Assume 9 hours at 70 W peak in operation

Location Resources

• For Philadelphia region,– Air temperature varies between 40-80

degrees Fahrenheit [4-27 degrees C]– Freezing conditions necessitate antifreeze in

thermal circulation system (Propylene glycol typically used)

Solar Availability in Philadelphia Region

K-T model of collector facing true south and ignoring local shading. Ground reflectivity is .2 for all months except .5 for January, .7 for February, and .4 for March.

Monthly Average Radiation on Tilted Collectors in Philadelphia

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Tilt Angle of 40 degrees

Tilt Angle of 55 Degrees

Schematic of DWH System

ThermalCollector Controller

Pump

Storage Tank(with heat

exchanger)

PV Collectors

Hot Water Out

Cold Water In

System Overview

Solar Collector Certification and Rating (June 10, 2005)

The SRCC is an independent third-party organization working out of Cocoa, FL composed of a twelve-member board of directors.

They select a collector at random from participating manufacturers, test it for performance and durability, and release an annual report. In return, the manufacturer gets to stamp the SRCC certification and rating on its product.

A Sample SRCC Rating

continued

Decoding the Rating

• Energy per day is given in the lower table as dependent on weather and temperature differential (Tin – Tamb)

• The SRCC rates Philadelphia as about 14 MJ/m^2/day. • A typical clear day is said to receive 23 MJ/m^2/day,

mildly cloudy is 17 MJ/m^2/day and cloudy is 11 MJ/m^2/day.

• Thus, to analyze collector performance in Philadelphia, we used an average of the mildly cloudy and cloudy day ratings.

Collector Type

The SRCC defines category C as a DHW in a warm climate, and category D as a DHW in a cool climate. We used category C to approximate the losses during summer and D in the winter.

Comparing Collectors

Company Location Model C (Summer) D (Winter) pg. #Net Aperature Area

(sq. ft)

Thermo Technologies Columbia, MD Mazdon TMA-600-30 24.5 18.5 131 36.39

Synergy Solar Austin, TX Synergy T26.68 14 5 129 24.46

Heliodyne, Inc. Richmond, CA Gobi 410 26 11 66 38.3

Focus Technology Co Nanjing, China Apricus AP-30 22 17 59 40.85

SunEarth Fontana, CA Empire EP-40 22.5 9.5 104 37.08

Alternate Energy Technologies Jacksonville, FL Morning Star MSC-40E 28.5 ? 49 36.9

ACR Solar International Carmichael, CA Fireball 2001 9 3.5 24 18.51

Efficiency Rating Per Collector Area

MJ/m^2

Model C (Summer) D (Winter)

Mazdon TMA-600-30 7.2 5.5Synergy T26.68 6.2 2.2

Gobi 410 7.3 3.1

Apricus AP-30 5.8 4.5

Empire EP-40 6.5 2.8

Morning Star MSC-40E 8.3Fireball 2001 5.2 2.0

For our climate and purpose, the Mazdon TMA-600-30 panel manufactured by Thermo Technologies in Maryland is the most efficient.

Project Load

Energy Needed (MJ/day):

Gallons/day Summer Winter

80 5.6 33.8

160 11.1 67.7

Obviously, the winter load will determine the number of panels needed to achieve a desired level of DHW. The family will probably desire three of the Mazdon collectors in order to generate the majority of the winter DHW load needed.

Solar Thermal Collector• Fireball 2001 Solar Collector

– Available in exciting architectural colors

– Weights 38 lbs, easy installation– Copper Solar absorber plate

• Coated with premium black crystal– Low emissivity and high absorptivity

• Serpentine Design to increase fluid exposure to collector

– Rigid Foam Installation for heat retention in the collector box

• Coated with special heat reflecting white paint called Enerchron

– Reflects heat back onto underside of the absorber

– Lightweight Polycarbonate glazing• High insulation value and UV

protection• Greenhouse effect

Solar Thermal Collector

• Fireball 2001 Solar Collector from SolarRoofs.com

• Critical Efficiency– 88% on Clear Day– 82% on Mildly Cloudy– 69% on Cloudy Day

• Loss Coefficient (kW/m2/˚C– .0264 on Clear Day– .0233 on Mildly Cloudy– .0255 on Cloudy Day

Thermal Performance of Fireball 2001 Solar Collector

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Features

Heat Transfer Fluid can be potable water or Propylene glycol

Maximum stagnation temperature of 250 degree F

Hot Water Storage Tank

• ASHRAE recommends 20 gallons of hot water consumption per day per person

• 120 gallon storage tanks in a 3 person household are typically used in the United States given its higher hot water consumption

• Need to include heat exchanger to extract heat from glycol thermal fluid

Solar Storage Tank Rheem - Solaraide TC

Features• 80 Gallon tank w/ heat

exchanger• Tank Lining resist corrosion• Anode rod equalizes turbulent

water action• Automatic temperature

control• Collector feed located at front

of tank• Has temp. and press. release

valve

Solar Circulating Pump

• Desire low power pump to transfer thermal energy from solar collector to storage tank through a heat transfer liquid.– Choose Propylene glycol to avoid freezing in

system– Must operate in recommended flow rate range

prescribed by solar thermal collector

                                     

                                                        

El-SID Pump from Thermo Technologies

•Highly conducive to PV panels because of its adjustable flow rate

•Flow rate changes depending on sun brightness

•Power Requirements and Performance

•12-17 VDC, Current range of .6-.85 Amps, Power of 10 watts

•Maximum flow rate of 3.3 GPM

•Optimal flow rate is 1.2 GPM for Mazdon Thermal Collector

•Features

•Long lasting

•Absence of moving parts, brushes, or bearings

•Magnetic coupled drive

Solar Controller

• Needed to monitor system to avoid overheating the storage tank and to set efficient operating conditions– Ensures efficient heat collection

• Desire low cost, low power consumption, and simple user-interface

Low Voltage Solar Energy Differential Controller

• The USDT 2001 can be powered by a 24 volts DC or AC source to monitor supply and return temperatures.– Need to use two 12 volt PV panel in

series to operate via VDC.– Microprocessor temperature controller to

regular solar heating. LED to indicate supply temperature exceeding return temperature by programmable temperature difference.

– Frost or cooling protection is regulated through return temperature monitoring.

– Max. Adjustable deltaT of 50 F– BP protection range of 32-200 F– Anti-front cycling for system freeze

protection (adjustable up to 50F)

www.thermotechs.com

Photovoltaic Module

• Needed to power solar circulation pump and controller.– Power requirements

• 12 watts needed

– Solar pump needs 12-17 VDC and controller needs 24 VDC

PV Panel from Solar Electric Supply-10

• 10 Watts,12V Nominal,17V Peak– Open Circuit Voltage: 21.6 V– Short Circuit Current: .7 A

• Peak Voltage/Current: 17V/.59A• Polycrystalline Type• Frame

– Anodized aluminum with tempered glass - Omni-mount frame

• Need to have two placed in series to generate adequate voltage to power components

System Cost

• Solar Thermal Collector $2500-3000

• PV Collector $89.95x2

• Storage Tank $1160

• Circulating Pump $229

• Solar Controller $159

• TOTAL ~$4500