solar water heating 2-hour print.ppt · pdf filejosh plaisted of kineo design and pvt solar....

Solar Hot Water Heating SystemsSolar Hot Water Heating Systems

Courtesy of DOE/NREL

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

Energy Training Center StocktonEnergy Training Center StocktonEnergy Training Center, StocktonEnergy Training Center, Stockton

InstructorInstructor

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

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

with assistance fromG Paul Menyharth of theG Paul Menyharth of the American Solar InstituteG. Paul Menyharth of the G. Paul Menyharth of the American Solar Institute

andJosh Plaisted of Kineo Design and PVT Solar

Agenda

• Industry overview• Essential physics• Terms and conceptsp• Collector and System types• Site evaluation and designSite evaluation and design

The Full Energy Picture

PG&E Portfolio Solution

1) Reduce consumption asReduce Energy

Use

1) Reduce consumption as much as possible.

2) Get theUse

Partnership

2) Get the “greenest” power you can.3) Offset any

Renewable PowerClimateSmart

Education

Outreach

) yremaining carbon emissions. Power

SupplyClimateSmart

Li htLi ht

Different Types of “Solar”Light energyLight energyPhotovoltaic (PV)Electricity produced directly from lightElectricity produced directly from light

Heat energyHeat energyC t t d S l P (CSP)Concentrated Solar Power (CSP)Electricity produced by steam

Solar Pool HeatingHot water for poolsHot water for pools

Solar Water Heating (SWH - Solar Thermal)Hot water for domestic use (DHW)

All courtesy of DOE/NREL

Solar Pool HeatingSwimming pool water heatingSwimming pool water heating

80 - 85 degrees from May to October


M t i d t ith i k t i C lif i d Fl idMature industry with main markets in California and Florida.

Overview

Courtesy CCSE

SHW Industry Overview: World

By Permission: REN21. 2008 ”Renewables 2007 Global Status Report”By Permission: REN21. 2008 Renewables 2007 Global Status Report (Paris:REN21) © 2008 Deutsche Gessellschaft fur Technische Zusammenarbeit GmbH

SHW Industry Overview: U.S. History

1890 to 1930’s: Beginnings in California

1930 to 1973: Growth in Florida

1973 to 1986: Oil Embargo and Carter Tax Credits

1986 to 2003: Removal of Tax Credits and Decline

2003 – present: Revival of Incentives and Climate Action

Industry Overview: U.S.

Federal Tax Credit:

Favorable regulatory environment

Federal Tax Credit:• Extended through 2016

30% f b th i l d id ti l• 30% for both commercial and residential• MACRS depreciation for commercial

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

Industry Overview: California

State rebate program: AB1470

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

• Systems installed after 7/15/09 eligible.

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

Essential Physics

Courtesy ofNASA

It all starts with the sun.

Electromagnetic Spectrum

10 -3 10 -7

heat light

Continuum of energy

Courtesy of Wikipedia

Continuum of energy.

Greenhouse Effect

Ozone layer

Short waves get throughlight

Long a es are trapped

Earth

Long waves are trapped

heatEarth

Greenhouse Effect

Glass

Short waves get throughlight

Long a es are trappedHeat absorber Long waves are trapped

heatabsorber

SWH collector

Color Absorption

Dark colors absorb a lot, reflect little

Li ht l b b littl fl t l tLight colors absorb little, reflect a lot

Metal Conductivity

Some metals transfer more heat than others.

FluidFluid Fluid

Pipe cross-section

Copper Ironp

Water Behavior

Water expands both when heated and frozen.

Steam IceIce

Moving water will NOT freeze.g

Water Behavior

Warm water will rise, cold water will sink.

Water Behavior

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

• “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 trappedg pp

• Color absorption• Dark colors absorb and light colors reflect

• Metal conductivity• Copper conducts more than others

W t b h i• Water behavior• Expands when heated and frozen• Moving water will not freeze• 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 waterof heated water …

With protection againstWith protection against freezing, overheating, and mineral buildup.mineral buildup.

Terms and Concepts

Courtesy ofNASA

Terms and ConceptsBTU: British Thermal Unit Amount of heat needed to raiseBTU: 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 BTU,Therm: 100,000 BTU (29.3 kWh)

Th i h N t l f h t t i i (i t b )Thermosiphon: Natural process of hot water rising (in a tube).Stratification: Separation of hot and cold water (in a tank).H t h D i th t t f h t f di

Climate zones: Areas of distinct seasonal temperatures

Heat exchanger: Device that transfers heat from one medium to another.

Climate zones: Areas of distinct seasonal temperatures.Hard freeze: A freeze in which seasonal vegetation is destroyed, ground is frozen solid, and heavy ice is formed.y g y

Stagnation: Condition when collectors are not used and become overheated.

Terms and Concepts

System design: Storage is the key.

Solar Electric: Solar Thermal:

Tied to the grid. Every kWh is used,

No grid--you’re on your own.

no waste.yPotential for waste.


Terms and ConceptsSolar Fraction: Percentage of building’s hot water requirements that can be met by solar—at optimum economics (no waste).

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 waterBut in summer sun, these collectors produce far more hot water than you use, and you can’t store it or sell it.Wasted energy, wasted money.

Solar Fraction: Design

Cover 100% in summer.Will result in 30 – 50% in winter.

Average year-round coverage of 60 – 70% in PG&E territory.

Will ALWAYS need a backup heating source (gas or electric).

Change in perspective

Solar Electric: Solar Thermal:

Selling / maintaining Selling / maintainingSelling / maintaining“solar”

Selling / maintaining “total hot water system” (solar + backup)


Change in perspective

One overall system

solar + backupp

One overall costO ll ffi i

One overall maintenanceO ll lifOne overall efficiency One overall lifespan

Collector and System Types

Courtesy ofNASA

Standard Water Heaters

Typical gas heater:

Direct flue.

M h h t l “Much heat loss “up the chimney”.

Low efficiency.

(50 – 70%)( %)

Courtesy PG&E


Improved model:

Same basic technology, better insulationbetter insulation.

Efficiency around 70 –80%80%.

Source: Energy Star


More improved model:

Condensing heater.

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

tiventing.

Vent gases are cool enough to condense.

Efficiency around 80 –

Source: Energy Star

y90+%


New model:

Heat pump.

Like refrigerator in reverse.

Electric powered, no gasElectric powered, no gas burning.

Best to replace electricBest to replace electric water heater.

Source: Energy Star


Tankless

Gas or electric.

Can require specialCan require special hookup service.

Effectiveness related toEffectiveness related to usage patterns.

Source: Energy Star

System Overview

Five main aspects of solar systems:

1. Heat collection2 Heat transfer2. Heat transfer3. Heat storage4 Heat backup4. Heat backup5. Extreme temperature protection

(f i / t ti )(freezing/stagnation)

System Overview

Five main aspects of solar thermal systems:

1. Heat Collection

2. Heat Transfer

3. Heat Storage

5. Extreme Temperature Protection

4. Heat Backup

Special valves, pumps, processes,

Solar panel

Water or glycol Storage

etc.Gas or electric heaterp g

tank

System Overview

Two types of heat transfer systems:

1 O L 2 Closed Loop1. Open Loop (Direct)

2. Closed Loop (Indirect)

water glycolwater glycol

Uses just the water from the main.

“O ” t t id

Uses heat-transfer fluid in “closed” system.

“Open” to outside elements.

Needs heat exchanger.

Collector and System Types

Two types of heat transfer systems:

1 O L 2 Closed Loop1. Open Loop (Direct)

2. Closed Loop (Indirect)

water glycolone fluid Heat

loopPotable water

HX

water glycol

Uses just the water from the main.

“O ” t t id

Uses heat-transfer fluid in “closed” system.

“Open” to outside elements.

Needs heat exchanger.

System Overview

Further categorized by “pumping” source:

1 P i1. Passive (natural)

2. Active (electric pump)

Thermosiphon process.

T k t b hi h

Must have electric source.

Tank must be higher than collector. Tank can be anywhere.

Collector Types

ICS (Batch) Flat Plate Evacuated Tube

Fi NRELFigure courtesy NREL

ICS: Integral Collector Storage

Heat St

Heat C ll i StorageCollection

Storage tank

Solar panel


Courtesy energybychoice.com


Hot water out

Roof tiltout

Cold water in

Holds 20 to 40 gallons of waterg


Courtesy NREL

Flat Plate Collector

Headers Risers

Figure courtesy SunEarth


“Fin” for heat absorption

Souce: PG&E


H t t

Header

Hot water out

R fRoof tilt

Ris

ers

C ld

Header

Cold water in Holds about one gallon of fluid

Evacuated Tubes

Photo courtesy Industrial Solar Technology Photo courtesy William Lord

Figure courtesy Edwards Hot Water


Evacuated Tubes

Copper rod: may be solid or hollow.

Heat moves eat o esup to bulb.

Double glass wall with vacuum between.

Souce: PG&E

Evacuated TubesFigures courtesy Thermomax

1. Vacuum tube2 Heat pipe

67

2. Heat pipe3. Cold liquid4. Hot vapor 2

1

3

89

4. Hot vapor5. Absorber 4

3

6. Collector return (hot)

5

(hot)7. Collector supply

(cold)8. Heat exchanger9. Shock absorber

H d

Evacuated Tubes

Cold water in Hot water out

Header

Roof tilt

Holds little or no fluid

Plumbing Different Collectors

Photo courtesy Industrial Solar Technology

Flat Plate Evacuated tube

ReturnReturnSupply

S lSupply

ICS: Integral Collector StorageThe Simplest Form of Solar

Benefits

p

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

Disadvantages• Sensitive to ambient temperatures• Sensitive to ambient temperatures• Weight


Sample specifications

Figure courtesy NREL

Simple system with ICS Courtesy of EERE

Simple system with ICS

Heated water moves to top

Hot water is drawn into tank

120 degree water goes into house

Additional heating element boosts temperature as

into house

Water comes in from main

boosts temperature as necessary

System Characteristics

F t i l ICS t

Passive

For typical ICS system:

Passive• No pumps, nothing requiring outside power

Open Loop• New fluid (water) is constantly entering—system is “open”

to outside elementsto outside elements


Flat Plate CollectorsThe Industry Workhorse


Sample specifications



Thermosiphon Passive Systems

Photo courtesy NREL

Thermosiphon Passive Systems

Courtesy CCSE

Thermosiphon Passive SystemsT k t bl tTank—potable water

Heat-exchange loop—”closed” to outside elements

Separation between water in tank and heat-exchange fluid

Figure courtesy SunEarth Inc

Thermosiphon Passive SystemsAdditional heating element boosts t t

W t i

temperature as necessary

120 degree water goes Water comes in to tank from main

g ginto house

Heated fluid rises

Heat is transferred to

Cooled fluid sinks

Heat is transferred to water in tank

Solar fluid circulates


Solar fluid circulates through collector


F t i l t k f t

Passive

For typical tank-on-roof systems:

Passive• No pumps, nothing requiring outside power

Closed Loop• Heat-exchange loop is closed to new elements

Open LoopAlso can be:

Open Loop• New fluid (water) is constantly entering—system is open

to new elements


Active Systems

P

Can be Open- or Closed-loop

Active Systemsp p

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

DisadvantagesDisadvantages• Some active components• More expense and maintenance



Active Systems

Courtesy University of Central Florida


F t i l fl t l t t d t b t

Active

For typical flat plate or evacuated tube systems:

Active• Uses pumps and other active elements

Open Loop• Potable water itself is heated

oror

Closed Loop• Glycol is heated and heat-exchanger is usedGlycol is heated and heat exchanger is used


Freeze Protection

1 Thermal mass (ICS)

Six different methods (can be combined):

1. Thermal mass (ICS)2. Antifreeze (closed loop glycol)3 Auxiliary heater (electric element)3. Auxiliary heater (electric element) 4. Drip valves (moving water won’t freeze)5. Forced circulation of hot water (DFC) 6. Draining (removing water from collector)


Thermal Mass

20 to 40 gallons of water will only freeze under extreme conditions.

ICS systems are freeze-protected in mild (coastal) climate zones.

Antifreeze

• Closed-loop (indirect) systems

• Uses food-grade glycol, specific mixture depending on climate zone.

• Must be serviced every 5 – 15 years.

• The hotter the glycol is run, the more it breaks down and the sooner it needs to be replaced.

• Freeze protection up to 40 degrees below zero.

Auxiliary Heater

• Electric resistance (strip) heater on pipes, collectors.

• Like a heating padLike a heating pad.

• Triggered at specific temperature.

Vulnerable to power outages• Vulnerable to power outages.

Drip Valves

Membrane in valve retracts at around 40 degrees, permitting water to drip out onto the roof.

Courtesy University of Central FloridaCourtesy University of Central Florida

Drip valves are good backup protection against mild freezes, but are vulnerable to failure, particularly in hard-water areas.

Direct Forced Circulation (DFC)

Freeze drain valve Always combined with drip valve(s).


Direct Forced Circulation (DFC)

Freeze drain valve

In freeze conditions, reverse flow gi es p heatgives up heat to protect the system.

Hot water


Drain-back System (closed loop)

Collectors are always empty

hen s stemwhen system (pump) is not running.



Start up: Collectors areCollectors are filled and heating cycle begins.



Shut down: CollectorsCollectors automaticallydrain and heating cycle ends.


Drainback System

• Closed loop• Can use water or glycol in heat-collection loopg y p• Fluid is drained from collectors whenever

system is not runningsystem is not running• Needs large pump to push water into collectors• Pipes must be sloped properly for drainagePipes must be sloped properly for drainage


Site Evaluation and System Design

Courtesy ofNASA

Site Evaluation and Design

Criteria:• Solar resource

A il bl d i t ti• Available space and orientation• Climate zone (temperature range, freezes)• Hot water usage amount and patternsHot water usage amount and patterns• Economics


Solar Resource

Peak SunPeak Sun--hours Measured in kWh/mhours Measured in kWh/m22/day/day

Source: DOE National Renewable Energy Laboratory (NREL) Resource Assessment Programhttp://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/serve.cgi

Shading

• SWH panels not as sensitive to shading as solar electric (PV) panelssolar electric (PV) panels

• Shade measurements and tools similar to that of PVthat of PV

• Major difference: the SWH rebate program l id h di f 10 3only considers shading from 10 to 3.

Solar WindowSunriseSunset

Solar Window“Shade-free from 10 to 3”

Tilt and Orientation

Tilt l f th h iTilt = angle from the horizon.

Orientation = Azimuth = direction north-south in which the panels are facingwhich the panels are facing.

tilt angleºEx. 30º axis

From Horizon

Tilt Azimuth

Surface Orientation Factor (SOF)

90San Francisco, CA

600.40-0.500 50 0 60

SOF

30

Tilt0.50-0.600.60-0.700.70-0.800 80 0 90 300.80-0.900.90-1.00

Chart courtesy NREL

-90 -60 -30 0 30 60 900

AzimuthEast Westy

Rough Home Estimate

D h 60 80 f f f (• Do you have 60 to 80 square feet of roof (or ground) space that is unshaded from 10 to 3?

• Is it on a non-North facing slope (flat is OK)?

If you pass this first screening then the next step is to solicit bids from contractors. They can determine the yappropriate system and give a financial assessment.

Solar PathfinderSolar PathfinderUsed toUsed to gain a quick and approximate understanding gain a quick and approximate understanding

of of solar accesssolar access and objects on the horizon that shade a and objects on the horizon that shade a jjgiven location.given location.

• Latitude specific sun path diagram is placed in the pathfinder.

• The transparent convex plastic domeThe transparent, convex plastic dome reflects objects on the horizon, enabling the user to see the relationship between th bj t d th th f ththese objects and the path of the sun.

• Obstructions can be traced onto sunpath diagram.p g

Solmetric SunEyeSolmetric SunEyeTMTM

• Handheld measurement d i th tdevice that accurately measures solarmeasures solar access and shading (about g ($1400)

Courtesy: Solmetric, Corp.

Mounting

Usage

How much energy are you using to heat water?

Usually it’s not easy to determine, since water heating bills can include space heating and cooking as well.p g g

Three ways:Three ways:

1. Direct measurement

2 Bill l i2. Bill analysis

3. Estimation from industry standards

Industry Standards / Surveys

Average hot water usage per home per day:

• 20 gallons for the first person0 ga o s o t e st pe so

• 15 gallons for the second

• 10 each for all others• 10 each for all others

4 person household =

20 + 15 + 10 + 10 = 60 gallons per day

These assumptions are used in the CSI Thermal li l l tonline calculator.

Industry Standards / Surveys

Natural Gas Water Heating

Averages for typical 4-person home in PG&E territory:

Natural Gas Water HeatingYearly usage: 200 thermsYearly cost: about $300 (current prices)Typical solar fraction: 65 70%Typical solar fraction: 65 - 70%Typical solar savings: about $200 per year.

Electric Water HeatingYearly usage: 3,500 kWhYearly cost: about $700 (current prices)y $ ( p )Typical solar fraction: 65 - 70%Typical solar savings: about $500 per year.

Electric heating is 2 to 3 times as expensive as gas.

State Rebate Program: AB 1470Modeled after the very successful solar electric program (CSI)Modeled after the very successful solar electric program (CSI) to lower costs and raise product and contractor quality.

Uses online entry/calculation program:Uses online entry/calculation program:

• Only allows approved systems.

• Makes sure system is sized appropriately.

• Ensures proper freeze protection for climate zone.

• Gives conservative estimate of production.

• Determines rebate.Determines rebate.

State Rebate Program: AB 1470In additionIn addition…

All contractors or self-installers who want to participate in the rebate program must attend a one-day workshop given by therebate program must attend a one day workshop given by the Program Administrators.

After attending they will receive a unique ID number to use in g y qthe online entry program.

The URL for the CSI Thermal site is: www.csithermal.com

For a list of registered contractors go toFor a list of registered contractors go to

http://www.gosolarcalifornia.ca.gov/solarwater/contractors.php

Rebate Program: AB 1470Systems must be SRCC certified: www solar rating orgSystems must be SRCC certified: www.solar-rating.org

OG 300OG-300

System ratings

OG-100OG-100

Panel ratings

Sample Costing

Savings:• Average yearly usage 210 therms• Solar saves 70% of that, or 147 therms• Average cost per therm $1.37• Yearly savings about $200 (first year)

Cost:• Total installed price $7000• State rebate $1875 (147 * $12.82 up to max)• Tax credit ((7000-1875) * .3) = $1537• Net cost = (7000 – 1875 – 1537) = $3588

Glycol:Sample Costing

y• Will need to be recharged every 5 – 10 years• Best to be professionally done• Estimate of $250 per visit• Total about $750

Pump(s):• At least one replacement

E ti t f $500 $1000 $750• Estimate of $500 - $1000, use $750

Tank + heat exchanger• At least one replacement• Estimate $1000

Estimated total = $750 + $750 + $1000 = $2500

Natural Gas:

Sample CostingNatural Gas:• Typical heater costs $500• Labor costs can be another $300 - $500• Lifespan is 7 – 10 years• Electric heaters may be somewhat less

Conservative total approx. $2500Similar to solar maintenanceSimilar to solar maintenance

What’s a reasonable assessment?

Sample Costing

Solar needs to maintain both systems (solar + backup), but backup works 70%(solar backup), but backup works 70% less.

Can we assume 70% less maintenanceCan we assume 70% less maintenance costs for backup?

If so backup costs with solar would beIf so, backup costs with solar would be about $2500 * .3 = $750.

Maintenance with solar (25 yrs.)

M i i h lMaintenance costs with solar:

$2500 (solar) + $750 (backup) = $3250

Maintenance costs without solar: $2500

Difference: $3250 - $2500 = $750

Conclusion: solar maintenance costs areConclusion: solar maintenance costs are about $750 extra than before, and this should be added in to the overall cost of a solar system.

Works out to about $30/year, or aboutWorks out to about $30/year, or about 0.5% of the purchase price per year.

Sample Costing

Payback:First cost: $3 600• First cost: $3,600

• Maintenance adder: $750T t l lif l t $4350• Total lifecycle cost: $4350

• Savings first year: $200• Straight payback (no inflation factor) =

4350 / 209 = 21 years• With inflation factor of 5.5%, payback

shortens to about 15 years.

EconomicsIt’s recommended that you get at least three bids fromIt s recommended that you get at least three bids from reputable contractors. The bids should all contain the following, clearly specified:

• Full price, including tax, permit, and any additional charges.g

• Estimated maintenance costs and maintenance schedule.

• Estimated production, based on the CSI Thermal calculator output.

• Estimated first year and system lifetime savings, based on reasonable assumptions of utility costs and inflation.

• Warranties for all products and labor, clearly written.

Solar Water Heating Benefits

• Saves money• Lowers greenhouse gas emissions (local

and national goals)• Qualifies for state and federal incentives• Promotes energy independence• Keeps money in local economy

Thank you for participating!PG&E P ifi E C tPG&E Pacific Energy Center

More FREE educational opportunities at www.pge.com/energyclasses

solar water heating 2-hour print.ppt · pdf filejosh plaisted of kineo design and pvt solar....

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