Solar Electricity 14 April 2009 Monterey Institute for

Solar Electricity 14 April, 2009 Monterey Institute for International Studies Chris Greacen, Palang Thai

Palang Thai พลงไท พลง (palang): n 1. Power. 2. Empowerment. ไท (thai): adj. 1. Independence. 2. Self-reliance • Thailand NGO • Objective: – To ensure that the transformations that occur in the region's energy sector: augment, rather than undermine, social and environmental justice and sustainability. • Key approaches: – – We teach hands-on energy technology We help draft policies We comment on projects and plans We advocate reform in energy planning processes & regulatory regime

Outline • 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

Photovoltaics

Not to be confused with Concentrating Solar Power (Solar Thermal Electric)

How PV works

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

Off-grid system with AC & DC loads Image source: Solar Energy International SEI

Grid connected (AC) Image source: Solar Energy International SEI

Net metering Image source: Real Goods

Image source: Solar Energy International S

Image source: Solar Energy International SEI

Net Metering in the USA www. dsireusa. org / April 2009 WA: 100 ME: 100 MT: 50* ND: 100* OR: 25/2, 000* VT: 250 MN: 40 WY: 25* NV: 1, 000* CO: 2, 000 CA: 1, 000* WI: 20* IA: 500* co-ops & munis: 10/25 UT: 25/2, 000* NM: 80, 000* AZ: no limit* MI: 20* IN: 10* IL: 40* MO: 100 OH: no limit* WV: 25 KY: 30* NC: 20/100* OK: 100* AR: 25/300 GA: 10/100 HI: 100 KIUC: 50 LA: 25/300 FL: 2, 000* State policy Voluntary utility program(s) only * 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 VA: 20/500* 40 states & DC have adopted a net metering policy State policy applies to certain utility types only (e. g. , investor-owned utilities) Note: Numbers indicate system capacity limit in k. W. Some state limits vary by customer type, technology and/or system application. Other limits may also apply.

Grid-connected Solar PV • System size: 3 k. W

Grid-connected Solar PV Bangkok Solar 1 MW PV • Bangkok • Project size: 1 MW

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

Peak Sun Hours San Francisco: 5. 4 PSH annual average, tilt at latitude* 1200 Watts/m² 1000 800 600 Peak Sun Hours 400 200 6: 00 8: 00 10: 00 14: 00 *Source: http: //rredc. nrel. gov/solar/old_data/nsrdb/redbook/sum 2/23234. txt 16: 00 18: 00

annual average peak sun hours (PSH)

Anacortes, WA = 3. 7 PSH per day annual average San Francisco = 5. 4 PSH

Energy produced k. Wh per year = (PSH) x (peak k. W of array) x (solar panel derating) x (inverter efficiency) x 365 Example: 5. 4 hours x 2. 5 k. W x 85% x 95% x 365 = 4000 k. Wh

Grid-tied solar simple payback period • Installed cost $7 K to $9 K per k. W 2. 5 k. W * $8, 000 = $20, 000 • Value of annual electricity offset: $0. 25/k. Wh * 4000 k. Wh/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/k. Wh 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 WITH AC LOADS

Thai solar home systems

Solar for computer training centers in seven Karen refugee camps Thai-Burma border • 1 k. W PV hybrid with diesel generator • Each powers 12 computers

Off-grid system components Charge controller Solar panel Loads Battery

Off-grid system components Charge controller Solar panel Loads Battery

Lead Acid Batteries – Sulphuric Acid (H 2 SO 4). • Sulfation, equalizing Pb ra t or H 2 SO 4 Se pa • Electrolyte 2 – Negative electrode Lead (Pb). – Positive electrode Lead dioxide (Pb. O 2). - + Pb O • Two electrodes

Lead Acid Batteries

Flooded Lead Acid • Advantages: – Water can be added. – Cheapest. – Most common. • Disadvantages: – Can spill. – Hydrogen is vented during charging. – More prone to vibration damage.

Valve Regulated Lead Acid • Maintenance Free – Similar to Flooded Lead Acid. • Gel – Silica Gel contains the electrolyte • AGM (Absorbed Glass Mat) – Electrolyte is Absorbed in a Fiber Glass Mat

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

Lead Acid Battery Cycle Life Cycles to 80% capacity • Number of cycles to a particular DOD. • Cycle life decreases with increasing DOD. • Sulphation is the main cause of failure. 4000 Deep cycle battery 2000 Car battery 0% 50% 100% Depth of Discharge (DOD)

Battery Capacity • Given in Amp hours [Ah] for a particular discharge rate at 25°C. • Empty is usually defined as 10. 5 Volts. • Usable capacity depends on actual discharge rate and temperature.

Charge and Discharge Rates • Written Ct or C/t Where t = Time = Capacity[Ah]/rate[A] • Examples: – A 200 Ah battery at 10 amps takes 20 hours and has a C/20 rate. – A 200 Ah battery at 2 amps takes 100 hours and has a C/100 rate.

Capacity and Discharge Rate Battery Voltage • Lead sulphate forms at both electrodes. • H 2 SO 4 turns to water. • Discharge rate affects usable capacity. 12. 0 C/10 10. 5 0% 50% 100% Depth of Discharge

Charging Lead Acid Battery Voltage is a function of state of charge and charge rate Lead dioxide and lead form at electrodes. H 2 SO 4 increases. Lower charge rates avoid gassing. 16. 2 Battery Voltage • • C/10 14. 4 C/100 12. 0 0% 50% State of Charge 100%

Equalizing Charge • Only Applicable to Flooded Style Batteries – Provide a charged battery with a high terminal voltage, ~16 V. – High voltage causes the battery to “boil”. – Lead sulfate is dislodged from plates. – Bubbling action mixes up the stratified layers – Equalize charge for a few hours at a time

Off-grid system components Charge Controller Charge controller Solar panel Loads Battery

Charge controller • Ensures that battery is not overcharged • 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

Three Stage Charging • Reduces the charge rate as SOC increases. Bulk Charge Absorption Float 15 V C/100 Time Voltage Current C/20

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 3 X 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

ITEM Ceiling Fan Clock Radio Clothes Washer Electric Clock Iron Sewing Machine Table Fan Refrigerator/Freezer (19 Cu Ft) Refrigerator/Freezer (12 Cu Ft) Refrigerator/Freezer (4 Cu Ft) Blender Coffee Pot Microwave (. 5 Cu Ft) Electric Range Incandescent (100 W) Incandescent (60 W) Compact Fluorescent (60 W equivalent) Incandescent (40 W) Compact Fluorescent (40 W equivalent) CB Radio CD Player Cellular Phone Computer Printer Computer (Desktop) Computer (Laptop) Stereo (average volume) Stereo (Large Full volume) TV (12 inch black and white) TV (19 inch color) VCR Band Saw (14”) Circular Saw (7. 25”) Disc Sander (9”) Drill (1/4”) LOAD(Watts) 10 -50 5 1450 4 1500 10 -25 1000 Wh/day 470 Wh/day 210 Wh/day 350 1200 750 2100 60 16 40 11 10 35 24 100 80 -150 20 -50 15 150 15 60 40 1100 900 1200 250

Load analysis Watts Hours per hours each total day per day Qty Load 2 13 26 4 104 50 50 5 250 1 light laptop computer tv (19 inch color) 60 60 1 DVD player 30 30 1 circular saw 900 0. 25 225 1 blender 350 0. 25 87 Totals 1416 756 1

Inverter Load analysis Watts Hours per hours each total day per day Qty Load 2 13 26 4 104 50 50 5 250 1 light laptop computer tv (19 inch color) 60 60 1 DVD player 30 30 1 circular saw 900 0. 25 225 1 blender 350 0. 25 87 Totals 1416 756 1

Solar panels, batteries Load analysis Watts Hours per hours each total day per day Qty Load 2 13 26 4 104 50 50 5 250 1 light laptop computer tv (19 inch color) 60 60 1 DVD player 30 30 1 circular saw 900 0. 25 225 1 blender 350 0. 25 87 Totals 1416 756 1

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

How many solar panels? What size controller? Battery size? Qty Load 2 light 1 laptop computer 1 tv (19 inch color) 1 DVD player 1 circular saw 1 blender Totals Watts each Watts total 13 50 60 30 900 350 Hours per day 26 50 60 30 900 350 1416 Watt hours 4 5 1 1 0. 25 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) Nominal system voltage Adjusted amp-hours per day (= adjusted watthours / system voltage) Peak Sun Hours (average) Amps of solar power required (=Adjusted amp-hours / PSH) Imp (amps) per solar panel (Astopower PV 120 watt. Imp = 7. 1, Isc = 7. 7) Number of solar panels (= amps solar required / amps per panel) Rounded up… Isc per panel Minimum controller current (amps) = 1. 25 x Isc Maximum number of days of autonomy Max allowable depth of discharge Battery ampere-hours (= adjusted amphours x days of autonomy / allowable depth of discharge) 104 250 60 30 225 87. 5 756. 5 1, 199 12 99. 95 5. 4 18. 51 7. 10 2. 61 3 7. 7 29 3 0. 5 600

Wire sizing • Voltage drop – how much power is lost to heat V=IR • 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. http: //www. affordable-solar. com/wire. charts. htm

Wire sizing Typically aim for 3% or less loss http: //www. csgnetwork. com/voltagedropcalc. html

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 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. 2 1

Problems found during training surveys User error: Villager used inefficient 60 W light bulb

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”

Existing linkages Tax payers $ Ministry of Interior $ warranty PEA $ Installation company SHS End users

Missing linkages Tax payers $ Ministry of Interior $ warranty PEA $ Installation company SHS End users What happens when systems fail? There is no feedback loop from the end users to installation company, PEA, government or taxpayers

Missing linkages Tax payers $ Ministry of Interior $ warranty PEA $ Installation company SHS End users Feedback on status of systems, failure modes, successful interventions Warranty awareness Self-help: local technicians + user training

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