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The difficulty is that data centers don't generate "high grade heat" ie, they don't actually run very hot. While it might dissipate a lot of heat, the temperatu

The difficulty is that data centers don't generate "high grade heat" ie, they don't actually run very hot. While it might dissipate a lot of heat, the temperature is quite low (they claim their data center only run at ~30C). As a result, their 'waste' heat stream will never be above ~30C if they don't have anything special going on. There aren't a lot of useful things you can do with that type of heat. Even if they managed to dump it all into water and them pipe it over to surrounding housing, it's still not -that- useful, and likely not worth the cost/energy of setting up the system. While they could also conceivably run liquid cooling to -all- of their high temperature components (CPUs and PSUs probably) to get a higher grade waste heat stream, once again, its likely not worth the energy/money to set up that system. This is why most cogeneration or waste heat schemes are on industrial processes - their "waste" heat is pumping out at above boiling at a minimum, and far more useful.

mikeash 13y ago
Just to elaborate, this "low grade heat" makes it physically impossible to recover much energy out of it. If the ambient air is, say, 0C (273K), and the exhaust air is 30C (303K), then the optimal efficiency for recovering energy from the exhaust is less than 10%. In other words, if your data center uses 1MW of power, then with perfect recovery equipment, you could generate 100kW off the waste heat, reducing your total power consumption to 0.9MW. Not a particularly big win, especially since your recovery equipment is not going to be 100% efficient.
- Udo 13y ago
  Without any further treatment, it seems that waste heat is at least enough to heat living and office space (which is probably what they're doing with it). If you arrived at that 10% by just looking at the K, keep in mind that 0C is ambient temperature and already represents the lowest energy level of that system. I really believe it should be possible to take and use more of that 30° degree difference than a mere 3° off the top, even factoring in heat pumps for consolidating it and moving it around. 30° degrees of temperature difference is roughly the subcooling margin for nuclear reactors (http://en.wikipedia.org/wiki/Pressurized_water_reactor http://en.wikipedia.org/wiki/Pressurized_water_reactor), and that's at even higher overall temperatures!
  - mikeash 13y ago
    The place is "In the middle of a forest at the edge of town", so if you're using the exhaust for heating other buildings, you're going to need long insulated conduits to carry it all, and that's probably not worthwhile AND will lose a lot of the heat to the outside anyway.

mikeash 13y ago

Just to elaborate, this "low grade heat" makes it physically impossible to recover much energy out of it. If the ambient air is, say, 0C (273K), and the exhaust air is 30C (303K), then the optimal efficiency for recovering energy from the exhaust is less than 10%. In other words, if your data center uses 1MW of power, then with perfect recovery equipment, you could generate 100kW off the waste heat, reducing your total power consumption to 0.9MW. Not a particularly big win, especially since your recovery equipment is not going to be 100% efficient.

Udo 13y ago
Without any further treatment, it seems that waste heat is at least enough to heat living and office space (which is probably what they're doing with it). If you arrived at that 10% by just looking at the K, keep in mind that 0C is ambient temperature and already represents the lowest energy level of that system. I really believe it should be possible to take and use more of that 30° degree difference than a mere 3° off the top, even factoring in heat pumps for consolidating it and moving it around. 30° degrees of temperature difference is roughly the subcooling margin for nuclear reactors (http://en.wikipedia.org/wiki/Pressurized_water_reactor http://en.wikipedia.org/wiki/Pressurized_water_reactor), and that's at even higher overall temperatures!
- mikeash 13y ago
  The place is "In the middle of a forest at the edge of town", so if you're using the exhaust for heating other buildings, you're going to need long insulated conduits to carry it all, and that's probably not worthwhile AND will lose a lot of the heat to the outside anyway.