solar water heating basics webinar - pge.com · pdf filejosh plaisted of kineo design and pvt...
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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