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U.S. Department of Energy

Solar Energy Technologies

Solar Thermal Systems:Solar Heating R&D

National Renewable Energy Laboratory

Sandia National Laboratories

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Presentation Outline

Description of solar thermal R&D activities in:

Low-cost passive solar hot water systems Polymer integral collector-storage (PICS) systems

Low-cost active solar systems

Cold-climate solar water heating systems

Combined heating and cooling (CHC) systems

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Solar Thermal Systems Participants

National Laboratories National Renewable Energy Laboratory

Sandia National Laboratories

Industry FAFCO (California)

Davis Energy Group / SunEarth (California)

DuPont Canada Inc. (Ontario)

SRP (Arizona)

Energy Laboratories Inc. (Florida)

Universities University of Minnesota

University of Colorado

University of Central Florida

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Solar Thermal Systems R&D Goals

Near-Term (2006):

Mild-climate solar water heating systems that

deliver energy at $0.04 -$0.06/kWh

Mid-Term (2010):

Cold-climate solar water heating systems thatdeliver energy at $0.05 - $0.06/kWh

Long-Term (2015-2020): Solar space heating and cooling systems that

deliver energy at $0.04 - $0.05/kWh

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Solar Thermal Systems R&D

Low-Cost Passive

Solar Thermal Systems

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Solar Water Heating

Active

Common System Types

Passive

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Passive Solar Water Heating

Integral Collector-Storage

(ICS) System

GasketGlazings

Storage tanks

Insulation

Box

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Innovative, Low-Cost Solar Water Heaters

Project Goal:Cut the delivered, life-cycle energy cost of solar

water heating systems in half by the year 2005.

Source: Solar Buildings Technology Program: 5-YearStrategic Plan, January 31, 1998

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Hardware cost reduction Polymer technology

Parts integration

Installation cost reduction Lighter collectors, flexible bundled piping

Integrated balance of system

Marketing cost reduction New construction: SWH as standard feature or option Do-it-yourself / Home improvement stores

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Technical Challenges (Barriers):

Polymer durability the key technical challenge System performance

Overheating protection

Heat exchanger sizing and placement

Building code issues Use of plastics, e.g., flammability

Structural concerns, e.g., roof weight, wind loading

Manufacturing process design

Thermoforming and rotomolding temperaturetolerances

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Project Phases:

Concept Generation / Exploratory Research Identification of general system configurations which

could conceivably reach the projects cost goal Concept Development / Prototype Test

Development of detailed designs for promisingconcepts and construction and evaluation of prototypes

Advanced Development / Field Test

Development of second-generation prototypes andconducting limited field testing and evaluation

Engineering / Manufacturing Development

Construction of manufacturing facilities and evaluationof near-final systems in real-world applications

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Unpressurized Integral Collector Storage

Thin-walled polymer

vessel of water

Glazing(s)

Supply/Return Piping

Immersed heat exchanger

Insulation

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Davis Energy Group/SunEarth Design

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Davis Energy Group/SunEarth Field Test

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FAFCO Design

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FAFCO Prototype

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Material Durability Testing

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Durability Testing

Outdoor

Accelerated

Laboratory

Chambers

Ultra-Accelerated,

Natural Sunlight

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UV-Screened Polymeric Glazing Construction

Optional Bonding Layer (adhesive, etc.)

Screening Layer (UV absorbers)

Candidate Polymeric Glazing

Another Polymeric Element (e.g., absorber)

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GE HP92WDB 20-mil thick PC Film

No Korad UV screen; 8.2

months Ci5000 exposure

With Korad UV screen; 10

months Ci5000 exposure

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Low-Cost Active

Solar Thermal Systems

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Geographical Limitations of ICS Systems

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Residential Solar Water Heating

Active

Common System Types

Passive

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Active Solar Water Heating

Flat Plate Collector

Indirect Circulation

Solar System

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Active Solar Water Heating System R&D

DuPont CanadaUniversity

of Minnesota

Labs and

Industry

Low Cost Solar Water Heaters

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Low-Cost Solar Water Heaters

for Cold Climates

Polymer Flat Plate

Collector

DuPont / University of Minnesota Collaboration

Polymeric Absorber and

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Heat Exchanger Testing

New In-situ optical device for measuring scale

Tensile strength testing

University of Minnesota

Polyethylene

Polypropylene

Nylon 6,6 HTN

Polybutylene

Polypropylene

Teflon Copper


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Heat Exchanger Testing

0

0.2

0.4

0.6

0.8

1

PSU PB (no

add)

PB (w

add)

Nylon 6,6 HTNExpos

ed/Unexposed

Strength

60C

>82C

For some polymers, hotchlorinated watersignificantly reducesstrength.

Alternate PB formulation(with additives) shows lessdegradation

Loss of strength occursvery rapidly in nylon 6,6.

Strength after 300-1200 hrs in ORP=825 mV

Materials tested at U of MN in FY2003

Strength after aging in Hot, Chlorinated H2O

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Polymer Tube Scaling

1 m 10 m 1 m

Teflon

1 m10 m1 m

Copper

NATIVE AFTER540 Hr exposure to hard water

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Polymer Tube Scaling (cont.)

NATIVE AFTER

540 Hr exposure to hard water

1 m 10 m 1 m

1 m 10 m 1 m

Nylon 6,6

PB

Calcium carbonate accumulates on all polymers tested.

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Polymer Tube Scaling

Results indicate nylon 6,6 enhances scaling.

Mass of scale on PP, PB, HTN, Teflon and copper tubes are similar.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

nylon 6,6 HTN PB PP Teflon CuTube

CaCO3(g/m

2)

HX1

HX2

HX3

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Combined Heating

and Cooling Systems

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Solar Thermal Systems R&D Approach

Features of polymer-based SWH systems: Year-round load: ; good system utilization

New materials:;

lower cost Simple systems: ; higher reliability

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Solar Thermal Systems R&D Approach

Combined space heating and cooling systems Year-round load: ; good system utilization

New materials: ; lower cost

Simple systems: ; higher reliability

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Combined Solar Heating & Cooling System

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COLLECTOR

HOUSE

TRIPLE PLAY MODEL

HOT

TANK

COLD

TANK

TSKY

PUMP

DIVERTER

CONTROLLER

DHWHTR

QAUX, DHW

QAUX, HTG/CLG

QSOL, HTG

WATER MAINS

T

T

TQINT

DHWDRAW

TSET, HTG/CLG

= COMPUTED

= SPECIFIED

GSUN GIR

QSOL, CLG

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Albuquerque, NM

Unglazed Collector 126 ft2, T_HX = 5

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JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Load(GJ) CLG aux

HTG aux

DHW aux

CLG Solar

HTG Solar

DHW Solar

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Albuquerque, NM Madison, WI Miami, FL

125 ft2

250 ft2

500 ft2

Combined Heating and

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Combined Heating and

Cooling Systems

Most Favorable Markets

Unglazed Collector Space Heating &Hot Water Savings

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Solar Thermal Systems R&D Goals

Near-Term (2006):

Mild-climate solar water heating systems that

deliver energy at $0.04 -$0.06/kWh

Mid-Term (2010):

Cold-climate solar water heating systems thatdeliver energy at $0.05 - $0.06/kWh

Long-Term (2015-2020): Solar space heating and cooling systems that

deliver energy at $0.04 - $0.05/kWh

Documents

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