A Fundamental Review of Solar Thermal Systems

Installation, Sizing and Benefits of a Bradford White Solar Thermal Water Heater

Bradford White Solar Thermal Training Program

• The sun’s rays hits a solar collector, heating the fluid inside.

• The heated fluid in the collector passes through a heat exchanger, which transfers its heat energy to the surrounding potable water.

• If an internal or external heat exchanger is not available, the heated collector fluid goes directly into the potable water in the tank.

How Does Solar Thermal Work?

– One way of expressing the thermal performance of a solar system is by stating the percentage of the load met by solar energy on a month-by-month basis.

– Monthly totals can be combined to yield the annual solar fraction, expressed as a decimal percentage (e.g. 0.15 = 15%)

– If a solar system has a SF of 0 then there is no solar energy utilized. If it has a SF of 1.0 then all energy provided is from solar.

– Dependent on many factors such as load, collector size, climate, etc.

– Example, the same solar equipment installed in a home in Arizona may have a SF of 75%, but if installed in Connecticut, it may only have a SF of 30%.

Solar Fraction (SF)

System Types

• Active is when a circulator pushes the fluid.

• Passive is when water temperature difference moves the water. Hot water rises/cold water falls.

• Open loop is when the potable water goes through the collector to be heated.

• Closed loop is when the heating fluid is closed off from the potable water and is contained in a loop.

Open Loop System

Closed Loop System

Solar Rating• The Solar Rating and Certification Corporation (SRCC) was provides independent testing, rating and certification of active solar collectors and solar domestic water heating systems.

• Standard OG-100 “Operating guidelines for certifying solar collectors”

• Standard OG-300 “Operating guidelines and minimum standards for certifying solar water heating systems”

OG-300 Certification• Standard OG-300 combines the physical testing of collectors and all major components in a solar water-heating system proposed for sale by manufacturer.

•The standard also provides simulated performance estimates for that system in specific geographical locations.

• Once a water heater is OG-300 certified, it then becomes ENERGY STAR® certified.

• Storage Tank– Stores and delivers heated potable water.

• Collectors– Flat Panel; more efficient in warmer climates– Evacuated Tube; more efficient in colder climates

• Circulation– Circulators

• Controls– Thermistors

• Fluid - the more glycol in the system, the harder the circulator works and lower the heat transfer capability.

Solar Thermal System Components

Heat Exchange Coil•Vitraglas® lined, 1 ½” O.D. carbon steel coil.

•Single Wall provides greater heat transfer.

•Double Wall provides additional protection from heating fluid and surrounding water.

•Because of the large diameter, a smaller and lower cost pump can be installed.

•Smooth internal surface area limits the amount of mineral deposit, which could decrease heat transfer capabilities.

•Glycol and toxicity rating of 1 (practically non-toxic) fluid can be introduced into coil.

• 1” NPT female fittings on single wall• ¾” NPT female fitting on double wall• The coil has a heat transfer area of 14.2 sq ft• Stored water volume of 2.7 gallons• Because of the material and thickness of the coil, maximum supply temperature from a heatingsource can be upwards of 240°F•Maximum supply temperature from a heatingsource must not exceed 250 F

Heat Exchange Coil

Heat Exchange Coil

Single WallDouble Wall

Double Wall Heat Exchange Coil

Head Loss

• Head loss due to friction of water flowing in a pipe is determined in feet of

head. As water moves through pipe and fittings, it loses energy to friction.

Pumps or circulators provide the energy to make up for this loss “head loss”

through the system.

• The more water you push through the pipes, or the smaller the pipes are, the

higher the head loss will be.

• Higher head loss means larger more expensive pumps.

Heat Exchanger Pressure Drop Curve

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Flowrate (GPM)

Tota

l Pre

ssur

e D

rop

(PS

ID)

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

Tot

al H

ead

Loss

(Fee

t)

Single-wallDouble-wall

Sizing a CirculatorHeat Exchanger Pressure Drop

Integrated Mixing Device Features:

• Push to turn hand wheel prevents accidental temperature change.

• Included thermo-strip to approximate outlet water temperature.

• Allows water in the tank to be stored at higher temperatures, increasing usable hot water by as much as 50%, while controlling the hot water outlet at lower temperatures.

• Additional outlet piping connection to draw off unmixed tank temperature water.

• Additional intlet piping connection for recirculation water into the mixing device.

• Additional outlet piping connection to draw off cold water without installing a saddle valve.

• Teflon® coated internal components to extend product life.

Integrated Mixing Device Package

Integrated Mixing Device*Mixed Hot Water

Outlet

½” NPT Un-Mixed Hot

Water Outlet

½” NPT Recirculation Inlet

¼” NPT Cold Water Outlet

Cold Water Inlet

*ASSE and UPC (IAPMO) Certified

Stainless SteelFlexible Connector

Push to TurnHand Wheel

Push to Turn Hand Wheel

100°F to 145ºF Temperature Range

Graduation marks to allow easy adjustment. Each increment is 5ºF.

Arrow is approximately 120°F

Solar Saver® Electric Backup (Open Loop)

• Models available– No heat exchanger; potable water is circulated

through the solar collector. Suitable for frost free locations.

• Single (upper) heating element• Supplied thermistor wires• Connections

– Potable -- Inlet dip tube; Anodic outlet device– Solar – Dip tubes in top of water heater

• Alternate side connects in 80 & 120 gallon models.

• Solar sensor can be mounted by means of threaded stud.

Solar Saver® Models

Model Number US Gal

First Hour Delivery Single

Elements

Floor to Heater Top

Jacket Dia.

Shipping Weight

MS65R6SS 65 46 gl. 59" 22" 168 lbs.MS80R6SS 80 53 gl. 59" 24" 210 lbs.MS120R6SS 119 83 gl. 62 1/2" 28" 310 lbs.

Solar Saver® Specification DataOpen Loop

EcoStor™ Electric Backup

• Models available– Single Wall Heat Exchanger for increased

performance– Double Wall Heat Exchanger for additional

protection between the heating fluid and potable water.

• Single (upper) or Dual Incoloy elements– 4.5 or 5.5 kW elements.

• Integrated Mixing Device for piping flexibility

• Supplied thermistor wires

• Two Anodes

EcoStor™ Solar Indirect Models

Model Number US Gal

First Hour Delivery Single

Elements

First Hour Delivery Dual

Elements

Floor to Heater Top

Jacket Dia.

Shipping Weight

S-SW2-60R6DS 60 46 gl. 84 gl. 59 1/4" 22" 210 lbs.S-SW2-75R6DS 75 53 gl. 97 gl. 59 1/4" 24" 236 lbs.S-SW2-115R6DS 115 83 gl. 124 gl. 62 3/4" 28 1/4" 340 lbs.

EcoStor™ Specification DataSingle Wall Heat Exchanger

Model Number US Gal

First Hour Delivery Single

Elements

First Hour Delivery Dual

Elements

Floor to Heater Top

Jacket Dia.

Shipping Weight

S-DW2-60R6DS 60 46 gl. 84 gl. 59 1/4" 22" 217 lbs.S-DW2-75R6DS 75 53 gl. 97 gl. 59 1/4" 24" 241 lbs.S-DW2-115R6DS 115 83 gl. 124 gl. 62 3/4" 28 1/4" 345 lbs.

EcoStor2™ Specification DataDouble Wall Heat Exchanger

EcoStor™ Heat Exchanger Backup

• Models available– Single Wall Upper Heat Exchanger– Double Wall Lower Heat Exchanger

• Dual Heat Exchanger Design– Can be connected to a variety of different heating

systems. – Solar, space heating, geothermal heating, boiler

heating

• Integrated Mixing Device

• Supplied thermistor wires

• Two Anodes

Heat Exchanger Backup

Solar Thermal

Model Number US Gal

Floor to Heater Top

Jacket Dia.

Shipping Weight

S-DC-DW2-55R6SW 55 62 3/4" 22" 282 lbs.S-DC-DW2-70R6SW 70 62 3/4" 24" 313 lbs.S-DC-DW2-110R6SW 110 66" 28 1/4" 442 lbs.

EcoStor™ Specification DataDual Heat Exchanger

Dual Heat Exchanger Connections

EcoStor2™ Gas BackupAtmospheric Vent

• Models Available – Natural Gas or Propane Gas – Atmospheric Vent– Double Wall Heat Exchanger– 61,000 – 76,000 BTU/hr. input range

• Honeywell Self Diagnostic Gas Control– Advanced temperature control system– Intelligent diagnostics

• Integrated Mixing Device

• Supplied thermistor wires

• Two Anodes

EcoStor2™ Gas Backup

Model Number US Gal

Nat & LP BTU/hr Input

Floor to Vent Conn.

Jacket Dia. Vent Shipping

Weight S-DW2-504T6FBN 45 65,000/61,000 59 1/4" 22" 4" 223 lbs.S-DW2-65T6FBN 60 65,000/63,000 63" 24" 4" 264 lbs.S-DW2-75S6BN 70 76,000/76,000 62 3/8" 26" 4" 306 lbs.

EcoStor2™ Specification Data

Propane models feature a Titanium Stainless Steel Propane Burner. For propane (LP) models, change suffix “BN” to “SX”.

EcoStor2™ Gas BackupPower Vent

• Models Available – Natural Gas or Propane Gas – Power Vent (3” or 4” PVC, CPVC, ABS)– Double Wall Heat Exchanger– 60,000 – 76,000 BTU/hr. input range

• Honeywell Self Diagnostic Electronic Gas Control– Advanced temperature control system– Intelligent diagnostics– Optional Programmable Setback Control

• Integrated Mixing Device

• Supplied thermistor wires

• Two Anodes

EcoStor2™ Gas Backup

Model Number US Gal

Nat & LP BTU/hr Input

Floor to Vent Conn.

Jacket Dia. Vent Shipping

Weight S-DW2-TW-50T6FBN 45 67,000/60,000 59 1/4" 22" 3" or 4" 247 lbs.S-DW2-TW-65T6FBN 60 70,000/63,000 63" 24" 3" or 4" 281 lbs.S-DW2-TW-75S6BN 70 76,000/75,500 62 3/8" 26" 3" or 4" 336 lbs.

EcoStor2™ Specification Data

Propane models feature a Titanium Stainless Steel Propane Burner. For propane (LP) models, change suffix “BN” to “SX”.

EcoStor2™ Gas BackupAtmospheric Vent Ultra Low NOx

• Models Available – Natural Gas Only– Atmospheric Vent– Double Wall Heat Exchanger– 40,000 – 55,000 BTU/hr. input range– Ultra Low NOx radiant burner– Meets the most stringent air quality requirements for

allowable NOx emissions in the country• Honeywell Self Diagnostic Gas Control

– Advanced temperature control system– Intelligent diagnostics

• Integrated Mixing Device• Supplied thermistor wires• Two Anodes

EcoStor2™ Gas Backup

Model Number US Gal

Nat BTU/hr Input

Floor to Vent Conn.

Jacket Dia. Vent Shipping

Weight S-DW4-U5036FRN 45 40,000 59 1/4" 22" 3" 233 lbs.S-DW2-U65T6FRN 60 55,000 63" 24" 4" 272 lbs.

EcoStor2™ Specification Data

• Determine the Daily Hot Water Demand (Gal.)– If unknown, estimate 30 gallons per person per day.– Determine typical inlet water temperature (°F) and desired outlet temperature

(°F).– Calculate the amount of Btu’s needed per day.

• BTU = Gallons x 8.25 x (Outlet – Inlet)• Example: 4 people with 58°F inlet with a 125°F tank• 4 people x 30 gallons/day = 120 gallons per day• BTU = 120 x 8.25 x (125-58) = 66,330 Btu/day

How Do I Size a System?Water Demand

• Flat panel – (Btu/day/1,000) x 1.1 = ft.2 of area.– More efficient in warmer climate/summer.

• Evacuated Tube – (Btu/day/1,000) x 1.3 = ft.2 of area.– More efficient in cooler climate/winter. – Collector temperature - outside temperature is larger.

• Calculate the amount of collector surface area.– Flat Panel: (66,330 Btu/day/1,000) x 1.1 = 73.0 ft2.– Evacuated Tube: (66,330 Btu/day/1,000) x 1.3 = 86.2 ft2.

• Other variables exist such as climate and panel location

How Do I Size a System?Collector Demand

Questions?