solar energy 20 october, 2010 monterey institute for international studies chris greacen, palang...
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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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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
This presentation available at:www.palangthai.org/docs