[GTALUG] NOT: Re: From BTRFS to what?

Stewart C. Russell scruss at gmail.com
Wed Sep 6 20:12:24 EDT 2017

On 2017-09-06 09:06 AM, Alvin Starr via talk wrote:
> A client came to me asking about helping him setup an Etherium mining
> server pool.

Hey, I know that there are some honest cryptocurrency types out there,
but there are some definite shady ones around Toronto. One Etherium
joker stole ~$500 of Raspberry Pis and accessories from my employer.
Caveat consultor.

I'm a (sometime) utility solar designer. The idea's interesting, but the
implementation's tricky.

> What if you glue a GPU with very little extra hardware to the back of a
> solar panel.

* Solar modules produce variable I-V output depending on sunlight and
air temperature. You'll need to use some kind of inverter to stop your
miners becoming puffs of expensive smoke in their first winter dawn.

> Stick it out in the sun and let it calculate 8-10 hours a day.
> Put a big heat sink on the GPU and it should be able to stay cool enough
> just from air cooling

* Solar modules run roughly 20°C hotter than ambient, often more. The
huge project I worked on in Arizona quite frequently hit 45°C in the
shade, so your GPU would be around 70°C under no load.

* The dead air behind modules is *very* still. Passive cooling would
likely melt.

* You'd need to weatherproof your GPUs against water, dust and ice. Any
crevices attract spiders and ants, and junction boxes in desert
locations are a favoured haunt for scorpions and rattlesnakes.

> Take a few thousand of these and set them out in a sunny place and you
> would have a coin generator.

* You'd need a small amount of ride-through battery, as a heavy cloud or
shading on the wrong bit of the module can reduce your power output to
close to zero.

> Once the hardware is paid for then the operational cost would be close
> to 0 but for some glass cleaner and rags.

* Almost everywhere on the planet requires some kind of permit or
environmental impact assessment. Even glass cleaner and rags need an
MSDS and hazard management plan.

* Some module types (thin film) are in perpetual danger of being
classified as hazardous waste due to their cadmium content.

* If you're far away from people, network is hard.

* If you're in an isolated area, theft of solar equipment is a huge problem.

* There's also something about solar modules that attract people with
shotguns. It usually ends badly for your installation, unless there's a
big fence.

> They would need to be networked together but it does not have to be high
> speed.
> It could be a low power mesh to an edge that connects via something as
> simple as cell phone data.

* Solar modules, with all that wiring and semiconductor hanging about,
make about the best radio signal attenuator I've ever seen. You only try
to make a cell call or get a GPS fix under a solar array once.

* The inverters you'll need can produce a fiendish amount of radio
interference unless they're shielded in expensive enclosures.

> Solar panels cost about $1/watt and there is no ongoing cost but power
> here costs about $0.08-0.16/KWH.

* Modules are way less than $1/W now. Racking will likely double the
cost of your installation, though.

* A utility-grade 330 Wp module is about 2 m² and weighs around 22 kg.
At these latitudes, you'll get about 40 W average across the whole year.
Since you're only proposing running through the day, you'd get more than
that. Have a play on PVWatts <http://pvwatts.nrel.gov/> for hourly
output. Choose a module like a Canadian Solar CS6U-330M for modelling:
it's a solid Mono-Si module with decent efficiency.


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