6 ms·

Produce electricity? I assume electricity was used to do the computation in the first place, turning into let's say 80% work and 20% heat. The idea was to use t

Produce electricity? I assume electricity was used to do the computation in the first place, turning into let's say 80% work and 20% heat. The idea was to use that 20% to heat our homes. The original electricity still needs to come from elsewhere.

lmilcin 6y ago
When I said Data Center can produce electricity I did not mean that it can produce as much or more than it takes in. I thought this obvious enough that it did not have to be said. But alas, it has to be said. No, you can't create perpetuum mobile ie. build a machine that given a supply of energy produces as much or even more energy. https://en.wikipedia.org/wiki/Perpetuum_mobile https://en.wikipedia.org/wiki/Perpetuum_mobile
- innocenat 6y ago
  It is still not viable. Assume your datacenter runs at 50C (122F) and the temperature outside is -40C (-40F), using the datacenter heat to generate electricity has theoretical maximum efficiency of 27.85%. If your datacenter is at 23C (73F) and room temp is 0C (32F), then the theoretical maximum is 7.77%. Note the word 'theoretical maximum', in reality probably at least 10 times worse than that.
  - lmilcin 6y ago
    You assume DCs are cooled by the whole volume of air inside when in fact you can put heat pipes on components and get closer to 70-90 degrees heat source. Even years ago when I worked in datacenters the air was circulated from outside to the server rack and then back outside, never crossing from the rack into server room. Newer generations of CPUs are going to be exchange less frequently but will produce more energy as they offer more dense computing. This makes case for investing more in the server hardware. Even then understand, that 7% of a huge amount of energy is still huge amount of energy. Edit: Apparently "Facebook datacenter in Denmark is supplying around 10.000 homes with heating" -- source, another poster. So... you need to rethink your expertise on defining what is and what is not viable.
    - innocenat 6y ago
      You can supply heat no problem. What I was talking about was recovering energy from heat, which is physically limited by Carnot engine. The percentage was Carnot engine efficiency. Note that it is impossible to create Carnot engine in real life, so actual efficiency is much, much, much lower.
oefrha 6y ago
Doing computations hardly stores any energy anywhere (the energy stored in, say, magnetization in a magnetic disk is pretty much negligible), so almost 100% of electricity is turned into heat. The problem with this ~100% efficiency is that, if your goal is heating, you can move way more than 100% heat with 100% electrical energy if you use, say, a heat pump.
- owlmirror 6y ago
  Heat pumps are not viable in a lot of cases, in an urban setting, it's probably the vast majority. So for the many cases were the alternative for heating would be burning fossil fuels, using electricity, ideally produced via renewable energy/nuclear, could be a superior alternative.
  - lrem 6y ago
    Wait, why heat pumps are not viable in an urban setting?
    - lmilcin 6y ago
      For many reasons. First, transporting heat as opposed to electricity is very wasteful, so you only want to transport it in very short distances. Second, typically even small single family home requires quite large volume to store the heat effectively for many months. It isn't that complex only because in a single family home setting you already have a bunch of uncontested land available so you can use the volume that is relatively flat and not too deep. Building this on a scale of a city would be insurmountable challenge. You would have to dig deeper than the buildings are high and any kind of works like that are difficult in urban areas.
      - user-the-name 6y ago
        I think you are thinking of something very different than what "heat pumps" actually are? They don't involve storing heat, they're just an inverse fridge.
virgo_eye 6y ago
No, essentially 100% of energy used for computation will turn into 'waste' heat. If you calculate 1000 digits of pi, those digits will not embody any energy.
- medstrom 6y ago
  Just turning chaos into order takes thermodynamic work, but I was wildly off with my percentages. Thinking in terms of an idealized computer that doesn't create heat, but didn't realize how far we were from that.

lmilcin 6y ago

When I said Data Center can produce electricity I did not mean that it can produce as much or more than it takes in. I thought this obvious enough that it did not have to be said. But alas, it has to be said. No, you can't create perpetuum mobile ie. build a machine that given a supply of energy produces as much or even more energy. https://en.wikipedia.org/wiki/Perpetuum_mobile https://en.wikipedia.org/wiki/Perpetuum_mobile

innocenat 6y ago
It is still not viable. Assume your datacenter runs at 50C (122F) and the temperature outside is -40C (-40F), using the datacenter heat to generate electricity has theoretical maximum efficiency of 27.85%. If your datacenter is at 23C (73F) and room temp is 0C (32F), then the theoretical maximum is 7.77%. Note the word 'theoretical maximum', in reality probably at least 10 times worse than that.
- lmilcin 6y ago
  You assume DCs are cooled by the whole volume of air inside when in fact you can put heat pipes on components and get closer to 70-90 degrees heat source. Even years ago when I worked in datacenters the air was circulated from outside to the server rack and then back outside, never crossing from the rack into server room. Newer generations of CPUs are going to be exchange less frequently but will produce more energy as they offer more dense computing. This makes case for investing more in the server hardware. Even then understand, that 7% of a huge amount of energy is still huge amount of energy. Edit: Apparently "Facebook datacenter in Denmark is supplying around 10.000 homes with heating" -- source, another poster. So... you need to rethink your expertise on defining what is and what is not viable.
  - innocenat 6y ago
    You can supply heat no problem. What I was talking about was recovering energy from heat, which is physically limited by Carnot engine. The percentage was Carnot engine efficiency. Note that it is impossible to create Carnot engine in real life, so actual efficiency is much, much, much lower.

oefrha 6y ago

Doing computations hardly stores any energy anywhere (the energy stored in, say, magnetization in a magnetic disk is pretty much negligible), so almost 100% of electricity is turned into heat. The problem with this ~100% efficiency is that, if your goal is heating, you can move way more than 100% heat with 100% electrical energy if you use, say, a heat pump.

owlmirror 6y ago
Heat pumps are not viable in a lot of cases, in an urban setting, it's probably the vast majority. So for the many cases were the alternative for heating would be burning fossil fuels, using electricity, ideally produced via renewable energy/nuclear, could be a superior alternative.
- lrem 6y ago
  Wait, why heat pumps are not viable in an urban setting?
  - lmilcin 6y ago
    For many reasons. First, transporting heat as opposed to electricity is very wasteful, so you only want to transport it in very short distances. Second, typically even small single family home requires quite large volume to store the heat effectively for many months. It isn't that complex only because in a single family home setting you already have a bunch of uncontested land available so you can use the volume that is relatively flat and not too deep. Building this on a scale of a city would be insurmountable challenge. You would have to dig deeper than the buildings are high and any kind of works like that are difficult in urban areas.
    - user-the-name 6y ago
      I think you are thinking of something very different than what "heat pumps" actually are? They don't involve storing heat, they're just an inverse fridge.

virgo_eye 6y ago

No, essentially 100% of energy used for computation will turn into 'waste' heat. If you calculate 1000 digits of pi, those digits will not embody any energy.

medstrom 6y ago
Just turning chaos into order takes thermodynamic work, but I was wildly off with my percentages. Thinking in terms of an idealized computer that doesn't create heat, but didn't realize how far we were from that.