Solar Energy 20 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 heating Cooking Home heating/cooling

COMMON GROUND: “Zero Net Energy” Community LOPEZ COMMUNITY LAND TRUST Lopez Island, WA

Solar water heating

Generating electricity from sunlight Solar thermal electricPhotovoltaics (PV)

How solar thermal electric works

Concentrating Solar Power (Solar Thermal Electric)

Solar Energy Generating Systems (SEGS) Kramer Junction, CA

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

Photovoltaics

Net Metering in the USA State policy Voluntary utility program(s) only / 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: 100 KIUC: 50 CO: 2,000 co-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, states & DC have adopted a net metering policy Note: 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 = U.S. dollars FuelAdderAdditional for diesel offsetting areas Additional for 3 southern provinces Years effective Biomass Capacity <= 1 MW $ $ Capacity > 1 MW $ $ Biogas <= 1 MW $ $ > 1 MW $ $ Waste (community waste, non-hazardous industrial and not organic matter) Fermentation $ $ Thermal process $ $ Wind <= 50 kW $ $ > 50 kW $ $ Micro-hydro 50 kW - <200 kW $ $ <50 kW $ $ Solar $ $ Tariff = adder(s) + bulk supply tariff + FT charge Solar tariff = $ $ $0.03 = $0.32/kWh

call center การไฟฟ้าส่วนภูมิภาค การไฟฟ้าส่วนภูมิภาค PROVINCIAL ELECTRICITY AUTHORITY Generating Capacity supply to Grid from 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

Watts/m² 8:00 10:0014:0016:00 6:00 18:00 Peak Sun Hours San Francisco: 5.4 PSH annual average, tilt at latitude* *Source:

annual average peak sun hours (PSH)

Anacortes, WA = 3.7 PSH per day annual average San 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 kW 2.5 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% Note: project is real. Financials are conjecture. 10% discount rate, 4% inflation

Off-grid systems DC 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 panel Charge controller Battery Loads Off-grid system components

Solar panel Charge controller Battery Loads Off-grid system components

PbO 2 Pb Separator + - H 2 SO 4 Lead Acid Batteries Two electrodes –Negative electrode Lead (Pb). –Positive electrode Lead dioxide (PbO 2 ). Electrolyte –Sulphuric Acid (H 2 SO 4 ). 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 Cycles to 80% capacity

Solar panel Charge controller Battery Loads Off-grid system components Charge 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 system 1.Load analysis 2.Specify capacity of solar panel, battery, charge controller, and inverter (if necessary) 3.Wire sizing

ITEMLOAD(Watts) Ceiling Fan10-50 Clock Radio5 Clothes Washer1450 Electric Clock4 Iron1500 Sewing Machine100 Table Fan10-25 Refrigerator/Freezer (19 Cu Ft)1000 Wh/day Refrigerator/Freezer (12 Cu Ft)470 Wh/day Refrigerator/Freezer (4 Cu Ft)210 Wh/day Blender350 Coffee Pot1200 Microwave (.5 Cu Ft)750 Electric Range2100 Incandescent (100W)100 Incandescent (60W)60 Compact Fluorescent (60W equivalent)16 Incandescent (40W)40 Compact Fluorescent (40W equivalent)11 CB Radio10 CD Player35 Cellular Phone24 Computer Printer100 Computer (Desktop) Computer (Laptop)20-50 Stereo (average volume)15 Stereo (Large Full volume)150 TV (12 inch black and white)15 TV (19 inch color)60 VCR40 Band Saw (14”)1100 Circular Saw (7.25”)900 Disc Sander (9”)1200 Drill (1/4”)250

Load analysis QtyLoad Watts each Watts total Hours per day Watt hours per day 2light laptop computer tv (19 inch color)60 1 1DVD player30 1 1circular saw blender Totals

Load analysis QtyLoad Watts each Watts total Hours per day Watt hours per day 2light laptop computer tv (19 inch color)60 1 1DVD player30 1 1circular saw blender Totals Inverter

Load analysis QtyLoad Watts each Watts total Hours per day Watt hours per day 2light laptop computer tv (19 inch color)60 1 1DVD player30 1 1circular saw blender Totals Solar panels, batteries

Solar panel derating: 15% Loss from Wiring: 3% Loss from Battery: 15%

How many solar panels? What size controller? Battery size? QtyLoadWatts eachWatts totalHours per dayWatt hours 2light laptop computer tv (19 inch color)60 1 1DVD player30 1 1circular saw blender Totals Solar panel derating85% Battery efficiency85% Wiring efficiency97% Inverter efficiency90% Total efficiency63% Total adjusted watt hours per day (= watt hours / total efficiency) 1,199 Nominal system voltage12 Adjusted amp-hours per day (= adjusted watthours / system voltage) Peak Sun Hours (average)5.4 Amps of solar power required (=Adjusted amp-hours / PSH) Imp (amps) per solar panel (Astopower PV 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 panel7.7 Minimum controller current (amps) = 1.25 x Isc 29 Maximum number of days of autonomy3 Max allowable depth of discharge0.5 Battery 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 Chart Maximum distance one-way in feet Multiply distances by 2 for 24 volts and by 4 for 48 volts.

Wire sizing Typically aim for 3% or less loss

Ampacity table

PV system errors

User error: bypassed controller  battery overcharge 1.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 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

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