Re: Data Center Heat Recovery


Hi Steve,


Leakage current on package only appears if the CPU runs at more than 65°C. This happens very frequently in air cooled environment, when we see CPU at up to 90°C (package temperature). DLC and Immersion allow an inlet temperature between 35 and 45 (depending on technology and “side cooling” for hybrid cooling systems), and will allow heat recovery, without facing leakage current on package.


I think your message was  to say that, to get water at 65°C (for reuse), it is better to get the water out of the IT at around 50°C, and use a heat pump. The heat pump with inlet at 45°C will have a COP of 4 (up to 6, in some cases) while the CPU has a COP of 1 (or even below 1 if you calculate it the same way you do for a heat pump).


BTW, looking at real cases, a heat pump is usually required to regulate the temperature entering the reuse system, if you want to inter-operate with standard building heating or hot water systems that are already in place. Cases that go direct from IT water to facility hot water (NREL, LRZ, etc.) look like ‘home-made’ with a lot of adaptations just not to use a heat pump. I agree that connecting the outlet to a heat pump will be the most efficient long-term investment.






François Jeanmougin
Head of Advanced computing
Phone : +33 768 36 37 12
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De : <> De la part de Steve Harrington via
Envoyé : mardi 19 mai 2020 23:46
À :
Objet : Re: [OCP-All] Data Center Heat Recovery


The NREL data center is very efficient. However, when looking at heat recovery, you have to balance the extra power required at higher CPU temperature with the cost of efficient heat pumps. (a one to one comparison of watts of heat to watts of computer power is not appropriate) A hotter running processor may require 5% more power and a typical heat pump has a COP of 4.

This means that if you run your 100 watt processor hotter so it uses 105 watts to get usable heat, and the heat your are replacing requires 25 watts of power to produce 100 watts of heat, the 20 watt power savings for a 100 watts of heat may not justify the expense of hooking the computer to the heating system.

Also, once you hook up a heat source that you can't control to a heating system, you need to have a backup source of heat.

I don't think it makes sense for San Diego, but it might for a place where heat is expensive and the computers are running at full load all of the time.


Steve Harrington, Ph.D

Chilldyne, Inc | Founder & CTO | 760.476.3419 x510 | 760.994.5544 Cell

5900 Sea Lion Place, suite 150 Carlsbad CA 92010



On 5/19/2020 12:10 PM, Kevin McCoin via wrote:


NREL has done some really awesome stuff in this space and are currently operating at a 1.025 PUE.  Contact for this facility is Otto VanGeet:


Here’s a live dashboard that includes a depiction of their recovery approach:




Kevin L. McCoin

Distinguished Architect, Systems Engineering

Walmart Technology

Enterprise Critical Infrastructure Services
Phone: 479-277-2135  fax: 479-277-4244




Wal-Mart Inc.
805 Moberly Lane
Bentonville, AR, 72712-9280-0560
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From: <> On Behalf Of Andrew Witteck
Sent: Tuesday, May 19, 2020 1:31 PM
Subject: EXT: Re: [OCP-All] Data Center Heat Recovery


Thank you Rolf,

This is very much appreciated.


Andrew Witteck | Specialty Markets Manager

Armstrong International

o (772) 213-9541 ext 4025

c  (772) 473-3055 


From: <> On Behalf Of rolf.brink@...
Sent: Tuesday, May 19, 2020 2:29 PM
Subject: Re: [OCP-All] Data Center Heat Recovery


Hi Andrew,


Yes, this is currently a topic in the ACS Harmonization project. Best bet is to get in touch with the DCF group. ACS and DCF are working together on topics like this. I will put you in touch directly as well.



Rolf Brink

ACS Immersion


From: <> On Behalf Of Andrew Witteck
Sent: Tuesday, 19 May 2020 20:14
Subject: [OCP-All] Data Center Heat Recovery



Hesham, I am not aware of cellular in data centers. I am sorry.

I am interested to find out if there is any work in OCP projects that is related to using Air-cooled data center or liquid cooled data center hall expelled heat for thermal utilities in surrounding buildings? Also if there is any direct/indirect evaporative media work being done as well.





From: <> On Behalf Of Hesham
Sent: Saturday, May 16, 2020 1:41 AM
Subject: [OCP-All] Cellular Data Center



I am interested to find out if there is any work in OCP projects that is related to using Celluar in the Data Center.




Sent from Mail for Windows 10



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