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  • PG&EPG&EPacific Energy Center, San FranciscoPacific Energy Center, San Francisco

    Energy Training Center, StocktonEnergy Training Center, Stockton

    Solar Hot Water Heating SystemsSolar Hot Water Heating Systems

    Courtesy of DOE/NREL

  • Pete ShoemakerPete ShoemakerPG&E Pacific Energy CenterPG&E Pacific Energy Center

    (415) 973(415) [email protected]@pge.com

    InstructorInstructor

    with assistance from

    Paul Menyhearth of The American Solar InstituteJosh Plaisted of Kineo Design and PVT Solar

  • Courtesy of NASA

  • PG&E Portfolio Solution

    Reduce Energy

    Use

    Renewable Power Supply

    ClimateSmart

    Partnership

    Education

    Outreach

    1) Reduce consumption as much as possible.

    2) Get the greenestpower you can.3) Offset any

    remaining carbon emissions.

    The Full Energy Picture

  • Agenda

    Industry overview Essential physics Terms and concepts Collector and System types Site evaluation and design Economics

  • Two Types:1. Solar pool heating

    Industry Overview

    Recreational use Typically unglazed panels (no glass) Temperature around 80 degrees Works seasonally

    2. Solar water heating (SWH) Essential use Glazed panels Temperature around 120 degrees Works year-round Heats domestic hot water (DHW)

  • Solar Pool HeatingSwimming pool water heating

    80 - 85 degrees from May to October

    Source: Fafco

    Courtesy of DOE/NREL

    Mature industry with main markets in California and Florida.

  • Overview

    Courtesy CCSE

  • Overview

    Courtesy CCSE

  • Overview

    Courtesy CCSE

  • Overview

    Courtesy CCSE

  • Industry Overview: U.S.

    Federal Tax Credit: Extended through 2016 30% for both commercial and residential MACRS depreciation for commercial

    Favorable regulatory environment

    Other state and local rebate programs exist or are in the planning stages.

  • Upcoming state rebate program: AB1470

    Industry Overview: California

    Applications accepted 5/1/10 (residential) and 6/1/10 (commercial).

    Systems installed after 7/15/09 eligible.

    Allocation is 40% residential, 60% commercial and multi-family.

    Handbook and online calculator to be developed soon.

    Public meetings held at the CPUC on Van Ness.

  • Essential Physics

    It all starts with the sun.Courtesy ofNASA

  • Greenhouse Effect

    Earth

    Ozone layer

    Short waves get through

    Long waves are trapped

    light

    heat

  • Greenhouse Effect

    Short waves get through

    Long waves are trapped

    light

    heat

    SWH collector

    Glass

    Heat absorber

  • Metal Conductivity

    Some metals transfer more heat than others.

    Copper IronPipe cross-section

    Fluid Fluid

  • Water Behavior

    Water expands both when heated and frozen.

    Steam IceIce

    Moving water will NOT freeze.

  • Water Behavior

    Warm water will rise, cold water will sink.

  • Water Behavior

    Water contains dissolved minerals, which can cause unwanted buildup and clogging.

    Hard water contains more minerals, soft water less.

    Most common minerals are calcium and magnesium.

    The buildup of minerals is called calcification or scaling.

  • Essential Physics: Summary

    Greenhouse effect Light enters but heat trapped

    Color absorption Dark colors absorb and light colors reflect

    Metal conductivity Copper conducts more than others

    Water behavior Expands when heated and frozen Moving water will not freeze Warm water rises, cold water sinks Water contains dissolved minerals

  • Which leads to

    Glass-covered collectors, dark-colored, with copper or aluminum piping

    Systems designed to take advantage of the movement of heated water

    With protection against freezing, overheating, and mineral buildup.

  • Terms and Concepts

    Courtesy ofNASA

  • Terms and Concepts

    BTU: British Thermal Unit. Amount of heat needed to raise one lb. of water one degree F.

    Watt-hour: 3.4 BTU Kilowatt-hour: 3,413 BTUTherm: 100,000 BTU (29.3 kWh)

    Vacuum (evacuated) tube: Tube with no air.Thermosiphon: Natural process of hot water rising (in a tube).Stratification: Separation of hot and cold water (in a tank).Heat exchanger: Device that transfers heat from one medium to another.

    T (Delta T): Change in temperature.

  • Terms and Concepts

    Solar Electric:

    Tied to the grid. Every kWh is used, no waste.

    System design: Storage is the key.

    Solar Thermal:

    No grid--youre on your own.Potential for waste.

    Courtesy of DOE/NREL

  • Terms and Concepts

    Example:Design to cover 100% of usage year-round, including winter.Minimal sun in winter, so need many collectors (expensive).

    But in summer sun, these collectors produce far more hot water than you use, and you cant store it or sell it.Wasted energy, wasted money.

    Solar Fraction: Percentage of buildings hot water requirements that can be met by solarat optimum economics (no waste).

  • Solar Fraction: U.S.

    Simulated Solar Fraction Using a Base (Current Technology) Residential SWH System

    Source: NREL report 2007

  • Collector and System Types

    Courtesy ofNASA

  • Standard Water Heaters

    Typical gas heater:

    Courtesy PG&E

    Direct flue.

    Much heat loss up the chimney.

    Low efficiency.

    (50 70%)

  • Source: Energy Star

    Standard Water Heaters

    More improved model:

    Condensing heater.

    Extended flue which releases much of its heat to the water before venting.

    Vent gases are cool enough to condense.

    Efficiency around 80 90+%

  • Source: Energy Star

    Standard Water Heaters

    Tankless

    Gas or electric.

    Can require special hookup service.

    Effectiveness related to usage patterns.

  • 1. Heat collection2. Heat transfer3. Heat storage4. Heat backup5. Extreme temperature protection

    (freezing/stagnation)

    Collector and System Types

    Five main aspects of solar systems:

  • 1. Heat Collection

    Solar panel

    Collector and System Types

    Five main aspects of solar thermal systems:

    2. Heat Transfer

    Water or glycol

    3. Heat Storage

    Storage tank

    5. Extreme Temperature Protection

    Special valves, pumps, processes, etc.

    4. Heat Backup

    Gas or electric heater

  • Collector and System Types

    Two types of heat transfer systems:

    1. Open Loop (Direct)

    Uses just the water from the main.

    Open to outside elements.

    2. Closed Loop (Indirect)

    Uses heat-transfer fluid in closed system.

    Needs heat exchanger.

    water glycol

  • Collector and System Types

    Further categorized by pumping source:

    1. Passive (natural)

    Thermosiphonprocess.

    Tank must be higher than collector.

    Must have electric source.

    Tank can be anywhere.

    2. Active (electric pump)

  • 3. Heat Storage

    Storage tank

    1. Heat Collection

    Solar panel

    Combined

    ICS: Integral Collector Storage

  • ICS: Integral Collector Storage: 50% SF

    Courtesy energybychoice.com

  • Benefits Low first cost No moving parts Inherent overheat protection Moderate freeze protection

    Disadvantages Sensitive to ambient temperatures Weight

    ICS: Integral Collector Storage: 50% SF

    Figure courtesy SunEarth

    Figure courtesy NREL

    The Simplest Form of Solar

    Sample specifications

  • Simple system with ICS

  • Passive No pumps, nothing requiring outside power

    System Characteristics

    Figure courtesy NREL

    For typical ICS system:

    Open Loop New fluid (water) is constantly enteringsystem is open

    to outside elements

  • Figure courtesy NREL

    Sample specifications

    Flat Plate CollectorsThe Industry Workhorse

    Figure courtesy SunEarth

  • Benefits High thermal performance Not sensitive to ambient temp No moving parts Array is freeze protected

    Disadvantages Cant you get that tank off my roof! Supply & return lines not freeze protected

    Thermosiphon Passive Systems: 65% SF

    Figure courtesy SunEarth Inc

  • Thermosiphon Passive Systems: 65% SF

    Photo courtesy NREL

  • Thermosiphon Passive Systems: 65% SF

    Figure courtesy SunEarth Inc

    Water comes in to tank from main

    Heated fluid rises

    Solar fluid circulates through collector

    Additional heating element boosts temperature as necessary

    120 degree water goes into house

    Cooled fluid sinks

    Heat is transferred to water in tank

  • Passive No pumps, nothing requiring outside power

    System Characteristics

    Figure courtesy NREL

    For typical tank-on-roof systems:

    Closed Loop Heat-exchange loop is closed to new elements

    Open Loop New fluid (water) is constantly enteringsystem is open

    to new elements

    Also can be:

  • Low-Profile Active System

    Benefits Highest thermal performance Freeze protection to 60 F Lightweight low roof profile

    Disadvantages Some active components More expense and maintenance

    Active Systems

    Figure courtesy SunEarth Inc

    Courtesy of DOE/NREL

  • Active Systems

    P

    Needs pump(s) to operate.

  • Photo courtesy Industrial Solar Technology Photo courtesy William Lord