Yesterday was the Summer Solstice, the longest day of the year (in the Northern Hemisphere). A good time to review solar powered hotspots.
Providing free broadband web access using inexpensive 802.11 mesh network was demonstrated at the GoldenHillFreeWeb project, which describes how it’s done.
- Lumin Innovative Products, in Boulder, Colorado, uses Proxim access points. It takes five hours of direct sunlight to fully charge, after which it’ll run for up to 72 hours.
- Popular Science explains how to build a box that can pick up a signal and boost it another 200 to 300 feet. It uses a Linksys Wi-Fi range expander ($100), modified with an omnidirectional 9dBi antenna, a lead-acid battery ($22) and a 10-watt solar panel ($119) from Sundance Solar to charge it.
- The Solacam uses an IP video camera mounted on a freestanding pole in a remote location, powered by a battery charged by a solar panel. A Yagi antenna points the low-res video back to home base via Proxim Tsunami MP.11, an 802.11b-based, point-to-multipoint backhaul solution with a range up to about 12 miles.
- Solar-powered, Internet-capable lights are expected to be installed at more than 4,000 sites in Scotland. LED technology is used to provide lighting.
- A pedal-powered generator can crank out 250 watts for an hour (if you’re in good shape).
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OkSolar has packaged, solar-powered hotspots and IP video cameras.
- A solar-powered WiFi router/WiMax router/surveillance cam has been developed by London-based Kolam and Singapore-based Nex-G Systems. The access point by StarSight uses a high gain omni antenna and a high gain parabolic antenna for backhaul.
- UCSD’s High Performance Wireless Research and Education Network (HPWREN), brings WiFi to several Native American learning centers. They utilize four 80-watt solar panels capable of generating a peak power of 320 watts. Four independent 94-AH gel cell batteries can support up to four 2.4 GHz radios for five days if the panels should fail. Put it on a bike trailer for emergency communications.
- Inveneo’s Communications Station is designed around low power hardware and open source software including an ultra-low power Wyse S50 computer, an analog Telephone Adaptor and an outdoor wireless access point.
Champaign-Urbana Wireless has some good guidelines:
- Assume the WRT54 consumes about 7 watts. We need that service 24 hours a day – so the device will draw 24h * 7 watts = 168 watthours.
- Lead acid batteries have approx. 90% discharging efficiency so 168 wh / 0.9 = 187 wh
- At 12 Volt the current in ampere would be 187 wh / 12 volts = 15.55 amperehours
Now lets assume we get a bad weather situation while we harvest *nothing* from the sun because we have shitty weather with cloudy sky for one week.
- 15.5 amperehours/day * 7 days = 109 amperehours
- 109 ah * 12 Volt = 1308 watthours
If we allow our battery to get discharged from 100 % to 30% charge thus consuming 70 % of the capacity in such a rare situation (depending on the area where we are going to build the system) we need 109 ah / 0.7 = 156 ah storage capacity
A truck battery is available with this size. That would be the cheapest source. (Maybe you find a wrecked truck with working batteries, that the owner wants to donate or lend for a good purpose).
The amount of energy that you can harvest with a solarsystem depends on the area where you are and the time of the year. A well designed system should be able to fully recharge the battery within a few days in good weather conditions while delivering power to the AP.
Gizmodo has a bunch of solar-powered gadgets.
DailyWireless has more on Solar Powered Clouds, Solar WiFi Goes to College, Solar Electric to Go, Solar Powered Media, Access Points as Pencils, Linksys WiFi/Cellular Access Point, Mobile Hotspot How To, Hamster Powered Phone, Solar Powered WiFi, Solar PC, Solar Powered APs, Solar Powered Hotspot, WiFi Routers for Cars, USB Client with Antenna Connector, Routers Unwired: Burning Down The House, IPWireless Mobile Gateway, Cisco Does VSAT, PC Mag Tests KR-1 Mobile Router
