solar energy 20 october, 2010 monterey institute for international studies chris greacen, palang...

Solar Energy20 October, 2010

Monterey Institute for International Studies

Chris Greacen, Palang Thai

Outline• The sun’s energy• Passive solar, cooking, water heating, electricity• Photovoltaics (PV)

– Basic market trend– How PV works

• Basic types of solar electric systems• Grid-connected systems

– Components– Net metering– Calculating simple payback– (with detour on Peak Sun Hours, array tilt, shading)

• Off-grid– Components

• Lead acid batteries• Charge controllers• Inverters

– System sizing overview

World power consumption:

15 TW

Thermal

Electricity

Solar thermal electricity Photovoltaics

Water heatingCookingHome heating/cooling

COMMON GROUND: “Zero Net Energy”

Community

LOPEZ COMMUNITY LAND TRUSTLopez Island, WA

Solar water heating

Generating electricity from sunlight• Solar thermal electric • Photovoltaics (PV)

How solar thermal electric works

www.greenterrafirma.com

Concentrating Solar Power (Solar Thermal

Electric)

Solar Energy Generating Systems (SEGS)

Kramer Junction, CA

www.greenterrafirma.com

How PV works

Current/Voltage (IV) curve for solar cell

Off-grid array-direct system

Image source: Solar Energy International SEI

Off-grid direct current (DC) system with batteries

Image source: Solar Energy International SEI

Pico-PV (small DC systems) Barefoot Power

0.5W

1.0W

1.5W

2.5W

15W

5W

10W

3.6V 12V

Off-grid system with AC & DC loads

Image source: Solar Energy International SEI

Small (300 Watts): Solar Nexus Bigger (3 kW):

Trace

Grid connected (AC)

Image source: Solar Energy International SEI

Net metering

Image source: Real Goods

Image source: Solar Energy International SEI

Image source: Solar Energy International SEI

Photovoltaics

Net Metering in the USA

State policy

Voluntary utility program(s) only

www.dsireusa.org / April 2009

*State policy applies to certain utility types only (e.g., investor-owned utilities)

WA: 100

OR: 25/2,000*

CA: 1,000*

MT: 50*

NV: 1,000*

UT: 25/2,000*

AZ: no limit*

ND: 100*

NM: 80,000*

WY: 25*

HI: 100KIUC: 50

CO: 2,000co-ops & munis:

10/25

OK: 100*

MN: 40

LA: 25/300

AR: 25/300

MI: 20*

WI: 20*

MO: 100

IA: 500* IN: 10*

IL: 40*

FL: 2,000*

KY: 30*

OH: no limit*

GA: 10/100

WV: 25

NC: 20/100*

ME: 100

VT: 250

VA: 20/500*

NH: 100

MA: 60/1,000/2,000*

RI: 1,650/2,250/3,500*

CT: 2,000*

NY: 25/500/2,000*

PA: 50/3,000/5,000*

NJ: 2,000*

DE: 25/500/2,000*

MD: 2,000

DC: 1,000

40 states &

DC have adopted a

net metering policyNote: Numbers indicate system capacity limit in kW. Some state limits vary by customer type, technology and/or system application. Other limits may also apply.

Feed-in tariffs

• long-term contracts for the electricity produced

• purchase prices that are methodologically based on the cost of renewable energy generation.

Thai feed-in tariffs

Assumes exchange rate 1 Thai baht = 0.029762 U.S. dollars

Fuel Adder Additional for diesel offsetting areas

Additional for 3 southern provinces

Years effective

Biomass Capacity <= 1 MW $ 0.015 $ 0.030 $ 0.030 7 Capacity > 1 MW $ 0.009 $ 0.030 $ 0.030 7

Biogas <= 1 MW $ 0.015 $ 0.030 $ 0.030 7 > 1 MW $ 0.009 $ 0.030 $ 0.030 7

Waste (community waste, non-hazardous industrial and not organic matter)

Fermentation $ 0.074 $ 0.030 $ 0.030 7 Thermal process $ 0.104 $ 0.030 $ 0.030 7

Wind <= 50 kW $ 0.134 $ 0.045 $ 0.045 10 > 50 kW $ 0.104 $ 0.045 $ 0.045 10

Micro-hydro 50 kW - <200 kW $ 0.024 $ 0.030 $ 0.030 7 <50 kW $ 0.045 $ 0.030 $ 0.030 7

Solar $ 0.238 $ 0.045 $ 0.045 10

Tariff = adder(s) + bulk supply tariff + FT chargeSolar tariff = $0.24 + $0.05 + $0.03 = $0.32/kWh

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34การไฟฟ�าส่�วนภู�มิ�ภูาค

การไฟฟ�าส่�วนภู�มิ�ภูาคPROVINCIAL ELECTRICITY AUTHORITY

2006 2007 2008 20090

50

100

150

200

250

300

350

Wind

Hydro

MSW

Solar

Cogener-ation

Biogas

Biomass

รวมิ

Year

MW (31 August 2009)

Generating Capacity supply to Grid from 2006 - August 2009

• System size: 3 kW

Grid-connected Solar PV

Bangkok Solar 1 MW PV

• Bangkok• Project size: 1 MW

Grid-connected Solar PV

How do you estimate how much electricity it will produce?

How long does it takes to pay for itself?

Solar panel produces more power when it faces the sun

Seasonal array tilt

36.6 degrees in Monterey

1200

1000

800

600

400

200

Wat

ts/m

²

8:00 10:00 14:00 16:006:00 18:00

Peak Sun Hours

Peak Sun HoursSan Francisco: 5.4 PSH annual average, tilt at latitude*

*Source: http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/23234.txt

annual average peak sun hours (PSH)

Anacortes, WA = 3.7 PSH per day annual averageSan Francisco = 5.4 PSH

Energy produced

kWh per year = (PSH) x (peak kW of array) x (solar panel derating) x (inverter efficiency) x 365

Example:

5.4 hours x 2.5 kW x 85% x 95% x 365 = 4000 kWh

Grid-tied solar simple payback period

• Installed cost $7K to $9K per kW2.5 kW * $8,000 = $20,000

• Value of annual electricity offset:$0.25/kWh * 4000 kWh/year = $1000/yr

• Simple Payback:$20,000 / $1000/yr = 20 years

(assuming no subsidies)

Financial sketch: MW-scale solar project in Thailand

• Project size: 1 MW• Cost estimate: $4

million• Tariffs:

– TOTAL: $0.33/kWh for 10 years

• Simple Payback: 6.5 years

• 10-year IRR: 14%

Discounted accumulated cashflow

(120,000,000)

(100,000,000)

(80,000,000)

(60,000,000)

(40,000,000)

(20,000,000)

-

20,000,000

40,000,000

0 2 4 6 8 10

bah

t

Note: project is real. Financials are conjecture. 10% discount rate, 4% inflation

Off-grid systemsDC SYSTEMS

SYSTEMS WITH AC LOADS

Thai solar home systems

Solar for computer training centers in seven Karen refugee camps

Thai-Burma border

• 1 kW PV hybrid with diesel generator• Each powers 12 computers

Solar panelCharge controller

Battery

Loads

Off-grid system components

Solar panelCharge controller

Battery

Loads

Off-grid system components

PbO2

PbSep

arat

or

+ -

H2SO4

Lead Acid Batteries• Two electrodes

– Negative electrode Lead (Pb).

– Positive electrode Lead dioxide (PbO2).

• Electrolyte – Sulphuric Acid

(H2SO4).• Sulfation, equalizing

Lead Acid Batteries

Lead Acid Battery Types

• Starting, Lighting and Ignition (car battery)– Shallow cycle: 10% DOD– Deep discharge drastically reduces battery life.– Thin plates maximize surface area and current.

• Deep cycle – e.g. golf cart and forklift– Deep cycle: 60% to 80% DOD– Thick plates or tubes withstand deep discharge.

Lead Acid Battery Cycle Life

• Number of cycles to a particular DOD.• Cycle life decreases with increasing DOD.• Sulphation is the main cause of failure.

0% 50% 100%

Depth of Discharge (DOD)

Car battery

Deep cycle battery

2000

4000

Cyc

les

to 8

0%

cap

aci

ty

Solar panelCharge controller

Battery

Loads

Off-grid system componentsCharge Controller

Charge controller

• Ensures that battery is not over-charged

• For small DC systems, often features a Low Voltage Disconnect (LVD) to ensure that battery is not over-discharged

• Fancy big ones sometimes have Maximum Power Point Tracking (MPPT) that squeezes more power out of solar panels

Off-grid system components

Inverter• Converts Direct Current (DC) to

Alternating Current (AC) to power ‘regular’ loads

• Sometimes includes battery charger

• Typically can surge to 3X rated power

Inverter Waveforms

• Square Wave

• Modified Square Wave

• Sine Wave

Back-of-the-envelope steps for designing an off-grid solar

electric system1. Load analysis

2. Specify capacity of solar panel, battery, charge controller, and inverter (if necessary)

3. Wire sizing

ITEM LOAD(Watts)Ceiling Fan 10-50Clock Radio 5Clothes Washer 1450Electric Clock 4Iron 1500Sewing Machine 100Table Fan 10-25Refrigerator/Freezer (19 Cu Ft) 1000 Wh/dayRefrigerator/Freezer (12 Cu Ft) 470 Wh/dayRefrigerator/Freezer (4 Cu Ft) 210 Wh/dayBlender 350Coffee Pot 1200Microwave (.5 Cu Ft) 750Electric Range 2100Incandescent (100W) 100Incandescent (60W) 60Compact Fluorescent (60W equivalent) 16Incandescent (40W) 40Compact Fluorescent (40W equivalent) 11CB Radio 10CD Player 35Cellular Phone 24Computer Printer 100Computer (Desktop) 80-150Computer (Laptop) 20-50Stereo (average volume) 15Stereo (Large Full volume) 150TV (12 inch black and white) 15TV (19 inch color) 60VCR 40Band Saw (14”) 1100Circular Saw (7.25”) 900Disc Sander (9”) 1200Drill (1/4”) 250

Load analysis

Qty LoadWatts each

Watts total

Hours per day

Watt hours

per day

2 light 13 26 4 104

1laptop

computer 50 50 5 250

1tv (19 inch

color) 60 60 1 60

1 DVD player 30 30 1 30

1 circular saw 900 900 0.25 225

1 blender 350 350 0.25 87

  Totals   1416   756

Load analysis

Qty LoadWatts each

Watts total

Hours per day

Watt hours

per day

2 light 13 26 4 104

1laptop

computer 50 50 5 250

1tv (19 inch

color) 60 60 1 60

1 DVD player 30 30 1 30

1 circular saw 900 900 0.25 225

1 blender 350 350 0.25 87

  Totals   1416   756

Inverter

Load analysis

Qty LoadWatts each

Watts total

Hours per day

Watt hours

per day

2 light 13 26 4 104

1laptop

computer 50 50 5 250

1tv (19 inch

color) 60 60 1 60

1 DVD player 30 30 1 30

1 circular saw 900 900 0.25 225

1 blender 350 350 0.25 87

  Totals   1416   756

Solar panels,

batteries

Solar panel derating: 15%

Loss from Wiring: 3%

Loss from Battery: 15%

How many solar panels?What size controller?

Battery size?

Qty Load Watts each Watts total Hours per day Watt hours2light 13 26 4 1041 laptop computer 50 50 5 2501tv (19 inch color) 60 60 1 601DVD player 30 30 1 301circular saw 900 900 0.25 2251blender 350 350 0.25 87.5

  Totals   1416  756.5

Solar panel derating 85%Battery efficiency 85%Wiring efficiency 97%Inverter efficiency 90%Total efficiency 63%Total adjusted watt hours per day (= watt hours / total efficiency) 1,199 Nominal system voltage 12Adjusted amp-hours per day (= adjusted watthours / system voltage) 99.95 Peak Sun Hours (average) 5.4Amps of solar power required (=Adjusted amp-hours / PSH) 18.51 Imp (amps) per solar panel (Astopower PV120. 120 watt. Imp = 7.1, Isc = 7.7) 7.10 Number of solar panels (= amps solar required / amps per panel) 2.61 Rounded up… 3 Isc per panel 7.7Minimum controller current (amps) = 1.25 x Isc 29 Maximum number of days of autonomy 3Max allowable depth of discharge 0.5Battery ampere-hours (= adjusted amphours x days of autonomy / allowable depth of discharge) 600

Wire sizing• Voltage drop – how much power is lost to heat

V = I R

• Ampacity – how much current the wire can safely conduct

12 Volt 2% Wire Loss ChartMaximum distance one-way in feet

Multiply distances by 2 for 24 volts and by 4 for 48 volts.

http://www.affordable-solar.com/wire.charts.htm

Wire sizing

http://www.csgnetwork.com/voltagedropcalc.html

Typically aim for 3% or less loss

Ampacity table

PV system errors

User error: bypassed controller battery

overcharge1. Villager bypasses broken

controller and charges battery directly from PV

2. Battery over-charged. Electrolyte level drops and plates are exposed to air. Battery fails.

1

2

User error: Controller bypass leads to burned diode

1

2

1. Villager bypasses broken controller and charges battery directly from PV

2. One mistake of reverse battery polarity blows up bypass diode in PV junction box, melting junction box.

User error: Villager used inefficient 60 W light bulb

Problems found during training surveys

Installation error: Battery failure caused by solar panel installation in shady location

14:00 Saw Kre Ka village, Tha Song Yang District

Installation error: Bad panel locations

“The Service & Support Department is like the guy in the parade who walks behind the elephant with a broom and a big bucket”

Ministry of Interior

PEA

Installation company

End users

$

$

SHS

Existing linkages

warranty

Tax payers

$

Ministry of Interior

PEA

Installation company

End users

$

$

SHS

Missing linkages

warranty

What happens when systems fail? There is no feedback loop from the end users to

installation company, PEA, government or taxpayers

Tax payers

$

Warranty awareness Self-help: local technicians

+ user training

Ministry of Interior

PEA

Installation company

End users

$

$

SHS

Missing linkages

warranty

Tax payers

$

Feedback on status of systems, failure

modes, successful interventions

SHS Warranty• Postcards with warranty

and maintenance information could be distributed by Tambons

• Idea presented at meeting with DLA (Department of Local Administration)

BGET SHS trainings in Tak province

Thank you

chris@palangthai.org

This presentation available at:www.palangthai.org/docs