Solar Power Basics for WiFi Networks & ICT

1. Solar Power Basicsfor WiFi Networks & ICT Bruce Baikie BSME – Michigan Technological University Green WiFi - Founder SUN Microsystems – Telecommunication Engineer

2. Agenda • Solar Power Basic • PV System Components • The Solar Panel • The Battery • The Charge Controller • The WiFi & ICT loads • PV System Sizing for WiFi • Costs

3. Why Solar? Earth at Night: http://antwrp.gsfc.nasa.gov/apod/ap001127.html

4. Solar System - Functional Components Collect & Distribute Energy Collect Energy Regulate Energy Regulate Energy Store Energy Store Energy Start Control Energy Distribute Energy Use Energy

5. PV Cell Basics • Semiconductor of transparent positive silicon and negative silicon backing • Incoming light (photons) cause energized electrons to move to the n-silicon and out the connector • Nominal voltage of 0.55 V requires series connections to get useful voltage, 16 V • Short circuit current is proportional to light intensity Maximum output when normal to cell is pointed at light (cosine of sun offset angle) Ref.: FSEC

6. Controls charge current to protect battery Disconnects battery if voltage falls too low (10.6 V is typical) Removes charge current if voltage rises too high (14V is typical) Disconnects Solar Panels at night Charge controller

7. Energy Storage • Energy may be stored chemically • Physically in water behind high dams • Electrically • Flywheels World's largest storage dam, Uganda's Owen Falls Dam. The hydroelectric station at the dam supplies most of the electricity requirements of Uganda, and parts of Kenya.

8. Lead-acid (car) batteries economical but do not work for solar – Need be deep-cycle type batteries Requires maintenance to ensure long life Storage Battery

9. Inverter converts low voltage direct current to 120 VAC 12v or 24v DC input High losses in DC to AC conversion +20% Inverter

10. Typical PV WiFi setup http://www.nunames.nu/about/SolarFi.PDF

11. Solar Panels • Photovoltaic (PV) module is the smallest replaceable unit in a PV array • Solar electric panels come in all shapes and sizes • 36 PV cells connected = 12v • Four factors for solar electric panel's output • efficiency of the cells • the load resistance • solar irradiance • cell temperature

12. Solar Panels - continued • Cell efficiency - 3% to 17% • Load resistance determines where module will operate • Maximum power point • Current and voltage (I-V) curve • Cell Temperature

13. Solar Panels - Shading • 50% drop in cell output • Cells connect in series – so weakest cell will bring the others down • Bird droppings also issue • Leaves & Dirt

14. Solar Panels - Position • Solar Insolation • Orientation • Tilt angle near the latitude angle

15. Batteries • Alessandro Volta in Italy credited with inventor of the modern battery • Lead Acid • NiCad • NiMH • Li-ion Ancient cells discovered in Sumerian ruins origin around 250 BC

16. Batteries – Major PV Lead Acid Types • Flooded (wet) • Gelled • AGM (Absorbed Glass Mat)

17. Batteries • Temperature Effects Batteries • Cycles vs. Life • Battery Voltages • Amp-Hour Capacity • Battery Aging

18. Batteries - Mini Factoids • All batteries will not reach full capacity until cycled 10-30 times • Inactivity can be extremely harmful to a battery. It is a VERY poor idea to buy new batteries and "save" them for later. • Lead-Acid batteries do NOT have a memory, and the rumor that they should be fully discharged to avoid this "memory" is totally false and will lead to early battery failure.

19. Solar Charge Controller • Rated and Sized by Amps & Volts • Blocking Reverse Current • Preventing Overcharge • Control Set Points vs. Temperature • Control Set Points vs. Battery Type • Low Voltage Disconnect (LVD) • Overload Protection • Max Power Point Tracking (MPPT)

20. WiFi Solar Charge Controller - DIY • Jaldi Charger - Pauli Närhi • Affordable price • Locally made using commonly available tools and materials • POE injector • Tier – Power Project • MPPT • Status reporting - Ethernet • POE • Trickle charge http://drupal.airjaldi.com/system/files/Jaldi_Charger_design_1.6.3.pdf http://tier.cs.berkeley.edu/wiki/Power

21. ICT Loads

22. WiFi Loads

23. WiFi Loads – PC Cards

24. PV System Sizing for WiFi Units of measurement • Ampere:Amps - An unit in which electrical current flow is measured • Wattage:Watts – An unit in which electrical power is measured and is obtained by multiplying Voltage and Ampere • Voltage: Volt – An unit in which electrical force is measured. • Watt Hours:Whr - An unit in which electrical power consumption is measured and is obtained by multiplying the wattage by the number of hours of use.

25. PV System Sizing for WiFi The Load Example - A Linksys WRT54GL Router draws 12v draws at 0.67 Amps. What is the Power consumption if it runs for 24 hours? = volts x amps x hours = 12 x .67 x 24 = 192 watt - hours

26. PV System Sizing for WiFi The Battery Example - The capacity of a battery is given in amp hours, but this is very cumbersome and since the battery voltage is always fixed, we divide the watt hours by the voltage. =volts x Amps x hours Volts To get Amp hours • So if a battery is rated at 24 Amp Hour Capacity we can draw • - 2 Amps from it for 12 hours or • - 12 Amps for two hours or • - 24 Amps for 1 hour etc.

27. PV System Sizing for WiFi The PV Example - A Solar Panel output is rated in terms of watts, but we need to know its daily output, watts per day, or sunshine period. This is given as the Solar Radiation period, From Mozambique to the South African border has a very good one, namely 5.5 hours per day. So a 40 watt panel will produce 40 watts x 5.5 hours/day which is 220 watt hours per day. But this power is stored in battery and battery capacity is given in Amp Hours so it is easier to express the Solar Panel Output in Amp Hours.

28. PV System Sizing for WiFi • Power Required per day - 200 watt hours • Using a 12 volt battery 200 watt hours = about 17 Amps Hours 12 volts Battery Capacity Required • Daily Load – 17 Amp Hours • To allow for inefficiency + added overhead - 50% of load – 25 Amp Hr Total: • Daily Load 17 Amp Hr • Daily Radiation Period is 5.5 hours 17 Amp Hrs = 3.1 Amps 5.5 Hrs * 12v = 40 Watt Solar Panel Needed

29. Costs • Powering a single WRT54GL

30. Costs • What is available Locally • Spend more on good Batteries • Maintenance 240 Watt Solution - USD

31. Green WiFi Approach

32. Green WiFi Approach

33. 2008 Project Pipeline Key Projects for 2008 • Senegal – Drew School SF • Energy Management Group - Hawaii • South African Wireless Carrier w/WiMax • Brazzaville - Republic of the Congo • PC4Peace & Sun Microsystems – Vietnam • Xavier High School – Chuuk - Micronesia

34. Senegal School Project - June 2008

41. School Repair & ICT Project

42. Repairing Ceilings and Floors Holes in the ceiling and uneven floor surfaces need to be repaired. Blackboards, desks, and storage are in poor condition

43. Classroom Repairs Teacher’s Storage Teacher’s Desk

44. Desks and Floor Repairs

45. Blackboard and Desk Repairs

46. Internet based WiFi and ICT

47. Solar Power - ICT • 120 Watts • 2 Batteries – 100 Ah • Lighting • Mobile Phone Charging

48. Green WiFi – Project Green Box • 20’ shipping container • Fully Assembled • Built in hardware • 6 internet terminals • 1 Server OSS/BSS • 1 Printer & copier • 1 WiFi router • 10 node wifi net • AGM Battery subsystem • Coffee or tea maker • Mobile Phone Charging In partnership with

49. Summary of Solar Power Learning about solar electricity entails learning about • the sun • the earth • electricity • solar panels • positioning the panel • motion of earth around the sun • sin, cos, … • how the angle to the sun affects power generation • how to store up electric power • What is your WiFi power usage

50. Questions & Answers bruce@green-wifi.org Bruce.Baikie@sun.com