This was a best guess posted the the web site by SamChurchill. Please refine as new information becomes available.

Let's estimate the power requirements of a stand-alone Access Point that includes a 2-way satellite dish, laptop and access point on a hilltop driven by solar panels.

RickLindahl and others are probably better able to give a more accurate picture. But let's guess what a typical solar power Access Point might require for a hilltop Wireless LAN Access Point. These figures are ABSOLUTE GUESSWORK. It's just something to work from.

First, let's analyse the power requirements. I'm guessing on the power:

  1. Echostar 360 Satellite Modem power: 50 watt X 1amp X20hrs/day=1000AH
  2. Laptop Computer (Pentium-M) 20 watts X 1amp X 20hrs/day=400AH
  3. Wireless Access Point 10 watts X 1amp X 20hrs/day=200AH
  4. Total: 80 wattsX 20hrs/day=1600 Amp/Hours Daily

Oh, wait...wait...forget all that.

*** These calculations are all wrong. First of all, watts is a product of amps * voltage and you can't re-factor it to try and come up with AMP hours (which is typically used for batteries. Lets take a look at this again:

1. 50 watts for the Sat modem 2. Laptop at 20 watts 3. WAP at 10 watts Total is 80 watts draw.

Now, at 20 hours at day we get a 1.6 Kilowatt hour draw which is the amount of energy these devices use collectively. However, at any one moment the power used is 80 watts. Since Watts = Current * voltage, we can relate that to something a bit more understandable.

Lets say our voltage target is 12 volts since alot of car batteries and solar cell arrays seem to focus on that. Understand that some of our devices may need different voltages but this would be a start.

So, doing our math we see that 80 watts = Voltage (12) * current and we can derive current by watts/voltage (80/12) which comes out to 6.67 amps.

How about a $300 iPaq running LinuxAccessPoint with the HostApMode drivers? Maybe a Verizon 1XRTT Sierra Wireless 555 card ($300) in one slot (for the backhaul) and a Zcomax ($100) 802.11b card in the other (for the local access). Verizon provides "unlimited" 40-60Kbps cellular service for $99 (but a salesman told me yesterday that daytime minutes are actually limited). Anyway, if that combo works, it wouldn't take much juice. A 10 watt Solarex ($140) mounted on the lid of a small Pelican case ($100) might power it. Mount one on a bridge. X-scale uses even less juice. Or skip the solar and send one of these puppies up in a balloon for special events.

We only get sunlight perhaps 10 hours daily. If this settup consumes 80 watts/hr over 20 hours/day, we will need to store maybe 160 watts/hrs times 10 hours (of sunlight) to fill our 1600 watt/hr batteries. So at least two, 80 watt Siemens Solar Panels or more likely 3-4 might be advisable. This whole watt/hour business doesn't look right but I'm going to go with it for the moment.

Here's a guide using a solar powered Ham Repeater:


  1. Starband (Wildblue, DirectWay) $600

  2. Laptop ($1200)
  3. Access Point ($400)
  4. Mast, router, concrete base, etc ($400)
  5. Total ($2600)

So I get a total of $5,000 for a standalone, hilltop, 2-way satellite access point. I'm probably forgetting some basic and fundamental issues and way off. Still, if a solar-powered Access Point (or hey, a REPEATER) could be built for something like $10/month, that would be so fine. If 50 people paid $10/month that's $500/month.

You couldn't build a business on it. But it might work as a non-profit.

-- AdamShand (Cut and past from the MailingList)

Do Wildblue and DirecWay support/allow/condone sharing of access? --JonSchull

Thanks for posting it, Adam. I'm sure the figures are off but the basic concept is there. Here are more alternative energy and satellite links. Hams have lots of experience. Many power repeaters with PVs.

Someone posted a note that wind power might be more effective. Yeah. It's available 24hrs/day, too. Here's a $1500, 900 watt windmill from a local supplier, Solodyne.

Here are some solar and alternative energy links:

PV WebsitesSolar How ToHome Power MagazineSolar Access NewsSolarDyne in PortlandElectric Bikes $1000 LaFree Bike Denali Bike Imperial Cruiser with 30 foot mast Dynamic Vehicle TrackingElectrifying Times MagazineEV World MagazineNiMH BatteriesBP Solar Siemens Solar in VancouverUni-Solar ViaSat Solar RV Article Packet Radio Repeater Fuel Cell Bike Fuel Cell Letter Fuel Cell Links NREL

Here are some 2-way consumer satellite links

Starband Official Site Starband Users Group Great resourceDirecPC Now called Direct WayDirecWay Competition to Starband Wildblue Coming next year with Spotbeams and 400K up Hughes Spaceways Coming 2003 with 1.5Mbps and up TRW AstroLink Coming 2003 with 1.5Mbps and up iBeam U/O has uplink and downlinks statewide, national streaming provider for education

iBlast Broadcasters attempt to datacast Hughes EdgeUcast Marketing group for DirecPCPanamsat NET/36 Streaming content provider for Qwest and AT&T DSL/CableModems Pegasus FCC recently approved their spot beam satellites Cidera Umm, forgotNetSat Don't know if they're still around New ICO Craig's medium orbit answer to Teledesic MicroSpace Roll your ownOrbLynx Forgot the details Tachyon VSAT for businesses ($500/mo) Teledesic Craig's orbiting tax writeoff

From a post to the MailingList by SamChurchill (in part forwarded from the OpenAp list):

Anyway, I was thinking about the Bridge bridge. A DSL phone line under the Morrison Bridge feeds repeaters located on the Hawthorne and Broadway. Maybe use 802.11g for 11/54mbps.

A Linux Laptop supplies DHCP to the local node and repeaters at the distant bridges. The bridge nodes could be solar powered and since the nighttime traffic isn't much it wouldn't need to be 24/7. So this is from the OpenAp board:

Is the SMC2655W a good candidate for a port of OpenAP? Considering I have more than a few of these deployed, I would love to be able to use them as repeaters and form a larger WAN.

Currently, the network consists of:

One point of origin, a 3mbit DSL connected to a Linux PC. The Linux PC provides a DHCP server, as well as SECIP services. The server is connected to an SMC2655W MiniAP.

Spaced approximately 1/4 mile away from the point of origin, are three Orinoco AP units that act as wireless network extenders/repeaters. I have not found any cheap AP units that can act as repeaters with 802.11b other than these at this point.

The network covers an area about two miles in diameter, with an approximate data rate of 1-2 megabits at the edge of the range.

I would love to be able to deploy the SMC2655W units as repeaters, however the firmware provided with these units is <VERY> limited. No monitoring or status, no support for a DHCP server, and the MAC address filter has room for only 10 entries. Running OpenAP on these small units would be a definite blessing, for the repeater support.

A medium sized lead/acid gel cell, a small solar panel, a good antenna, and a nicely sealed project box with just the motherboard of the SMC2655W would be an ideal solution. These MiniAP's are extremely cheap.


{{{> I am just contemplating the idea of solar powered repeaters > in sealed plastic containers that could just be littered on rooftops > of buildings to provide extended outdoor coverage on sunny days or just > thrown on the ground for temporary outdoor events.}}}

I have a solar powered repeater project. It uses Linksys (Atmel) access points (2) because they have very low power consumption (2W typ) --- all 3.3v design.

{{{> The Fry's in Sunnyvale now has a shelf where they sell > a variety of solar panels for about $8 per claimed > watt in direct sunlight, if I recall correctly.}}}

No chance! You need to remember that the sun don't always shine :) And solar panels are rated for full, direct, bright sunlight, so they often don't produce their rated power even in daylight.

At my location, the latitude is 46 degrees and there can be days of cloud in winter, so I have two 110W panels and two 110Ah batteries. I'd be surprised if it were possible to get away with significantly smaller arrays and batteries even in a low latitude more sunny place.

BTW, that Fry's now carries large PV arrays (Siemens), I think up to 50W. You can also buy these things online for a lower price if you shop around.


Okay, OpenAP has caused me to rethink and simplfy. Forget solar power. All you really need is a car battery supporting the base of a free-standing 25 foot television mast. It feeds POE to the AP inside a Pelican case and offers wireless broadband--without a DSL connection--for what -$500? It should last 24 hours and - in an emergency - you just replace the car battery with a freshly charged one.

Maybe a solar-powered AP package with batteries and solar charger could be packaged for $500. It would have everything you need except the actual AP. Maybe a 40 watt solar panel could feed a small gell cell (going through a charger/controller). The 12 volts output would need to supply 2-3 amps for several hours. If it were used in a public demonstration, it wouldn't need huge capacity. Just enough power to top out the batteries and make sure that it could work for 4-8 hours.

A 12 Volt, 40Watt Panel costs $200, and a 2amp OpenAP costs about $200. Add batteries ($100) charger/controller ($100) and a panel/omni antenna for a remote (repeater). You don't need a DSL connection. ...on a bridge. The Bridge bridge. A standalone unit complete with 80 watts of solar power, gell cells, charger/controller and OpenAP might be packaged for $1000-$2000 a pop? Clamp 'em on top of a bridge superstructure and repeat after me..."Free 54mbs 802.11g Access is Good"...

The 40 watt photovolatic ($200), goes into a charger/controller ($100) and a 60 AmpHour gell cell battery ($100) stuffed into a Pelican case ($100). That's around $500. Then add an OpenAP Access Point ($200) with 8db gain omni ($100). A one-piece Pelican case might include a solar panel swivel mount. The batteries might be heavy duty and support the base of a free-standing mast so you don't need sandbags or guy wires. Here's a high-quality 1000 A/H battery but you could buy Marine batteries at Costco for lots cheaper, maybe $60.

Clif Cox showed PersonalTelco his Pelican Brief: a $2000 weather-proof case stuffed with Cisco APs, POE and other stuff. I have pictures and will post. He connects it to a Tracyron Satellite dish and offers Voice over IP using Promix and Symbol 802.11b cordless phones. He says H.323 works well.

Clif and John Gilmore are using this system in Bhutan, about 60 miles east of Nepal. John Gilmore and Clif Cox pioneered this sort of thing establishing a Richochet connection at Eugene's Country Fair 3 years ago and moving to the Tracyron Satellite dish at the Country Fair and Burning Man 2 years ago.

- Sam

The IBM DC adaptor can run off 12V DC. A deep cycle marine battery, runs a laptop. Assuming a 5A drain on the battery from the adaptor, you should have roughly a 20 hour life on a 110AH battery.

Four Semiens M55 Solar Panels connected in Parallel. Each Panel Produces 55 watts of 12 volt electricity at 3.5 amperage. Connected in Parallel, the four panels produce a maximum electrical charging output of 12 volts at 14 amps. If on an average of only four hours of direct sunlight per day, this will give us approximately 56 amp hours of battery charge daily.

Although a PV system can be as simple as a module and a load (such as a direct-driven fan), most PV systems are designed to supply power whenever it is needed and so must include batteries to store the energy generated by the PV array. Systems with batteries also need electronic devices to control their charging or limit the discharging of the batteries. Since PVs and batteries are inherently DC devices, larger systems usually include DC/AC inverters to supply AC power in standard voltages and frequencies. This enables the use of standard appliances in the system. Otherwise special DC appliances (usually from the RV or marine industry) must be used. On the electrical side, protective devices such as diodes, fuses, circuit breakers, safety switches and grounds are required to meet electric code safety standards. In general, PV systems also require mounting hardware to support and elevate the PV modules and wiring to connect the PV modules and other components together.

How long will my PV system last? Do PV modules lose power over time?

In general, the PV modules are the longest-lived component of a PV system. Top-quality modules such as Solarex's MEGA series are designed to last at least 30 years and carry a 20-year warranty. They are designed to withstand all of the rigors of the environment including arctic cold, desert heat, tropical humidity, winds in excess of 125 mph (200 kph), and 1 inch (25mm) hail at terminal velocity. High-quality industrial batteries will at best last about 7 years. Smaller sealed units will typically last 3 to 5 years. Automotive batteries are poorly matched to the characteristics of PV systems and will generally only last 12 to 18 months in PV service. Some types of PV module (using thin-film silicon) have a predictable falloff in output in the first few months of operation which slows down and stops after some time. The modules' output from then on is relatively stable.

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