Hot tub miners

[casascius]

how long do you think you can dump a few kilowatts of heat into a 500 gallon insulated hottub (that already generates heat during its filter cycles even when its not in actual use with people)?

youre gonna throttle your farm down when the tubs at temp?

BTW hottubs are 104 F (40 C).

If I planned my mining to roughly consume the same amount of power as the hot tub uses now, I should be able to keep that hardware busy. Even if it was only two 5970s, it is FREE power.  Of course that presumes I'm interested - I recently sold my mining gear.

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[vapourminer]

[lower hash rate to maintain temp]

yup, read that before. and I repeat:

youre gonna lower your hash rate to near zero?

OK, that will work, Ill admit.

BUT, arent we here to make some money too? not just save some by using waste heat.

[casascius]

BUT, arent we here to make some money too? not just save some by using waste heat.

Aren't these two equivalent?

If "you" provide a waterproof rig I can leave at the bottom of the pool and you "make" money and split it with me, that was worthwhile especially if it was just a couple gpu's. Do this with lots of people and you have money for little risk.

[notme]

BUT, arent we here to make some money too? not just save some by using waste heat.

Aren't these two equivalent?

If "you" provide a waterproof rig I can leave at the bottom of the pool and you "make" money and split it with me, that was worthwhile especially if it was just a couple gpu's. Do this with lots of people and you have money for little risk.

Sounds like a shockingly good time.

[vapourminer]

If I planned my mining to roughly consume the same amount of power as the hot tub uses now, I should be able to keep that hardware busy. Even if it was only two 5970s, it is FREE power.  Of course that presumes I'm interested - I recently sold my mining gear.

a couple cards is slightly more feasible. but even then 500 watts continuous is more than any decent hottub needs, unless you lave the cover off or something.

and I was under the impression some people in this thread had cooling kilowatt+ farms in mind.

this is a hottub we are talking about. we put people in them, not lobsters.

[DeathAndTaxes]

BUT, arent we here to make some money too? not just save some by using waste heat.

Aren't these two equivalent?

If "you" provide a waterproof rig I can leave at the bottom of the pool and you "make" money and split it with me, that was worthwhile especially if it was just a couple gpu's. Do this with lots of people and you have money for little risk.

No.

Putting rigs underwater is unsafe but lets ignore that for a second.  Computing hardware is expensive.  A 1 KW pool or hot tub heater is pretty cheap.  Maybe $300.  A rig which uses 1 KW or power, has water blocks, circulation pumps,  in a nice sealed box with heat exchanger and connections to hot tub is more like $2000. 

So using it part time isn't really viable for anyone.  Rig should run 24/7/365 and provide unlimited free heat to the hot tub but also 24/7/365 hashing operation.  Otherwise given the limited power needs of a hot tub you are looking at a payback period in decades.

This isn't to say something couldn't be done but
a) underwater rigs high voltage rigs
b) "part time" rigs

simply don't make any economical sense.

[vapourminer]

So using it part time isn't really viable for anyone.  Rig should run 24/7/365 and provide unlimited free heat to the hot tub but also 24/7/365 hashing operation.  Otherwise given the limited power needs of a hot tub you are looking at a payback period in decades.

This isn't to say something couldn't be done but
a) underwater rigs high voltage rigs
b) "part time" rigs

simply don't make any economical sense.

exactly. to me, throttling to maintain the hottub at 40C doesnt make sense.

hence, a pump, two loops (one to hottub, other to waste heat radiator), steppers controlling valves to the loops. a few ICs and other stuff (just need a comparator circuit for the temps, really).

on demand heat. max cooling (and hash rate) at all times. NOW its making sense.

[casascius]

It doesn't need to be anything fancy with connections. Just a box you stick underwater when you aren't using the hot tub.

As for "shockingly good time" just unplug the box and take it out when using the tub silly. And use a gfi outlet so the power is cut if any leaves the box into the water as a secondary measure (gfi is already installed on most outdoor outlets anyway on modern construction).

[rjk]

It doesn't need to be anything fancy with connections. Just a box you stick underwater when you aren't using the hot tub.

As for "shockingly good time" just unplug the box and take it out when using the tub silly. And use a gfi outlet so the power is cut if any leaves the box into the water as a secondary measure (gfi is already installed on most outdoor outlets anyway on modern construction).

I'm starting to see how you are thinking now. Most hot tub owners that I know of keep the thing on 24/7 so it is ready to go, but it sounds like you wish to only turn it on when you want to use it. In that case, you will need a lot of wattage, otherwise it will take forever to heat up.

[notme]

It doesn't need to be anything fancy with connections. Just a box you stick underwater when you aren't using the hot tub.

As for "shockingly good time" just unplug the box and take it out when using the tub silly. And use a gfi outlet so the power is cut if any leaves the box into the water as a secondary measure (gfi is already installed on most outdoor outlets anyway on modern construction).

Why not run a copper coil for the hot water instead of putting your electronics underwater?

[casascius]

I'm starting to see how you are thinking now. Most hot tub owners that I know of keep the thing on 24/7 so it is ready to go, but it sounds like you wish to only turn it on when you want to use it. In that case, you will need a lot of wattage, otherwise it will take forever to heat up.

I mean something like the opposite: I have to keep it warm 24/7 (or else it would freeze over), but only use it for 15 minutes here, an hour there.  The miner would keep it warm the rest of the time while it wasn't being used, and having it underwater would eliminate the noise problem.

The very fact that I HAVE to keep it warm in the winter (the only other choice is empty and unusable) means the power cost has already been justified the moment I decided to keep it full.

[rjk]

I'm starting to see how you are thinking now. Most hot tub owners that I know of keep the thing on 24/7 so it is ready to go, but it sounds like you wish to only turn it on when you want to use it. In that case, you will need a lot of wattage, otherwise it will take forever to heat up.

I mean something like the opposite: I have to keep it warm 24/7 (or else it would freeze over), but only use it for 15 minutes here, an hour there.  The miner would keep it warm the rest of the time while it wasn't being used, and having it underwater would eliminate the noise problem.

The very fact that I HAVE to keep it warm in the winter (the only other choice is empty and unusable) means the power cost has already been justified the moment I decided to keep it full.

OK I was confused by your statement of unplugging the box and taking it out, sorry. Still the extra cost would probably not be worth it.

Let's start with this: how many watts is the current heater, and what is the approximate duty cycle that it is running at? I am assuming it is not running full on all the time, but is rather switching in and out to keep the temp steady.

[casascius]

OK I was confused by your statement of unplugging the box and taking it out, sorry. Still the extra cost would probably not be worth it.

Let's start with this: how many watts is the current heater, and what is the approximate duty cycle that it is running at? I am assuming it is not running full on all the time, but is rather switching in and out to keep the temp steady.

Sure, the pool's heater will be switching on and off, but for all intents and purposes, let's say I can readily conclude that I can keep 500 watts of mining running full time, just by averaging its consumption for the month.

I don't know to be exact (I have never measured it) but let's assume that in the summer, it costs $50 a month in power, and in the winter, it costs $200.  That's 7 cents an hour in the summer, and 28 cents an hour in the winter.  7 cents an hour maybe buys me 500 watts.  In the winter, that buys me maybe 2000 watts (possibly more, because $/kWh is higher in the summer).

500 watts is what, a 5970+motherboard?  5970+5870+motherboard?  That's easily a gigahash.  Even with a 500-watt miner (relying on the hot tub's heater to provide the remainder of the heat for the winter), that equipment could be kept near 100% utilization on free power.  When power is free, equipment pays for itself much quicker.

[rjk]

Well unless you add a block to the CPU, don't count it in (same goes with PSU inefficiencies), since all the heat will only be coming from what you have blocks on. You could do 2 or 3 5970s, and even downclock them for a better mhash/watt while still getting enough to keep the pool warm.

[PulsedMedia]

crazy idea: Why not use a heat pump?

GPU-> Water to Water Heat exchanger -> pump -> GPUs

heat pump "cold side" would be warmed with the GPU temperature, giving you a better efficiency for heating the hot tub, while possibly making the GPUs inlet water temp below ambient, atleast at times.
Add water to air heat exchangers or other components as needed, just a basic crazy idea

Heat pumps can achieve close to even 1:6 ratios of efficiency, and i'm not kidding, there are a lot with those over 1:5 ratio for sale.

But yeah, your power consumption would still increase by at least 800W Plus the cost of making heat pump to heat the hot tub, no idea how much that will be.

[casascius]

Well unless you add a block to the CPU, don't count it in (same goes with PSU inefficiencies), since all the heat will only be coming from what you have blocks on. You could do 2 or 3 5970s, and even downclock them for a better mhash/watt while still getting enough to keep the pool warm.

If it's underwater, if the heat does not go into the water, where else will it go? =)

If heat is the desired product, there are zero inefficiencies.  The only thing there needs to be is something to make sure the CPU and PSU get their heat carried away so they don't burn up.  There will not be any net air flow - the air pocket will get hot in proportion to how well the heat can transfer out of the air and into the water.  A CPU block and a water-cooled power supply would probably be necessary.

[rjk]

Well unless you add a block to the CPU, don't count it in (same goes with PSU inefficiencies), since all the heat will only be coming from what you have blocks on. You could do 2 or 3 5970s, and even downclock them for a better mhash/watt while still getting enough to keep the pool warm.

If it's underwater, if the heat does not go into the water, where else will it go? =)

If heat is the desired product, there are zero inefficiencies.  The only thing there needs to be is something to make sure the CPU and PSU get their heat carried away so they don't burn up.  There will not be any net air flow - the air pocket will get hot in proportion to how well the heat can transfer out of the air and into the water.  A CPU block and a water-cooled power supply would probably be necessary.

So you you mean a completely sealed capsule/module that contains a miner that produces heat? And then you dunk it in?

[DeathAndTaxes]

Well unless you add a block to the CPU, don't count it in (same goes with PSU inefficiencies), since all the heat will only be coming from what you have blocks on. You could do 2 or 3 5970s, and even downclock them for a better mhash/watt while still getting enough to keep the pool warm.

If it's underwater, if the heat does not go into the water, where else will it go? =)

If heat is the desired product, there are zero inefficiencies.  The only thing there needs to be is something to make sure the CPU and PSU get their heat carried away so they don't burn up.  There will not be any net air flow - the air pocket will get hot in proportion to how well the heat can transfer out of the air and into the water.  A CPU block and a water-cooled power supply would probably be necessary.

Air is a very good insulator. 

[casascius]

So you you mean a completely sealed capsule/module that contains a miner that produces heat? And then you dunk it in?

Yes - drop it to the bottom, plug in power and ethernet, heat the hot tub and mine coins!

It would be nice if it could be WiFi too, but WiFi won't penetrate water worth a damn.  So, Ethernet is the only choice.

[ElectricMucus]

Get a big aluminum casing, IP68 and stick several FPGAs inside of it.

But you pretty much would have to develop your own board(s) (2 could fit in it on both sides)
And depending on the size of the hottub that's alot of fpgas, which would cost you.