* Posts by David Moss

2 posts • joined 3 Jul 2007

Green Grid pollutes environment with more white papers

David Moss

Give the Green Grid some time!!!

The companies deeply involved in the Green Grid are investing far more than the initiation price you refer to. I participate at the risk to my day job as do all the other contributors to the Green Grid. Our goal is to provide a positive effect on the energy consumption of an industry that provides a huge positive productivity impact to our economy. Gone are the days that a single company can write the rules for an industry. Today, the engineers of our respective companies have to assemble collectively to affect postive changes for the industry, and we assemble in many of these types of consortiums. The real value that the Green Grid will produce hopefully results in industry accepted metrics and procedures in achieving greater energy efficiency. The goal is global and is NOT "top secret". The fact that some of the work is curently limited to member companies is simply to provide value to membership in the effort. Nothing is free. If we rewinded to a time where a single company wrote all the rules, the price of admission would manifest itself in the price of the equipment that company sold. I particpate in other consortiums that publish books that you have to pay for; it's the price of the intellect. The ultimate goal of the Green Grid has to proliferate its value outside its current paying membership because it is aimed at creating valuable metrics and procedures for everyone to use to foster good energy responsibility

Dell gets hot over refrigerant

David Moss

Efficiency claims will eventually be validated

I have a lab of these cooling units at Dell. As soon as I'm able to measure the chilled water used by the entire XD system, I'll be able to verify the efficiency claims that do originate from Liebert. In theory, here is where the efficiency advantages come from: by being located closer to the racks (either hanging in a cold aisle or directly on top of the rack), the fan energy required to draw air across the cooling coil is much less than it is to push a comparable amount of air through a raised floor air handler and through the raised floor to the vent in front of the rack. The coil units overhead are provided liquid refrigerant via remote heat exchange / pumping units. The system is tuned such that the heat the coil picks up from the IT equipment creates a phase change of the refrigerant to gas as it absorbs the heat. This method of heat transfer is extremely efficient and requires less refrigerant than would a water based heat exchanger that operates as a single phase heat exchanger remaining a liquid. The pumps in the XD pumping unit are smaller and require less energy because they are pumping less fluid. The other efficiency advantage is that the XD system is designed to operate above the room's dew point all the time. There is no condensation in any of the XD coils. Condensation and subsequent re-humidification, which is common in CRACs and CRAHs, is a big energy drain.

And yes, if you happen to be fortunate to be located in a climate that enables fresh air cooling, that would generally be even more efficient. ASHRAE TC9.9, the group responsible for environmental recommendations is looking at the possibility of enlarging the recommended humidity ranges for IT equipment. If this happens, more of us can consider free cooling.

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