CO2 spells an end to hot desking

Carbon dioxide is often seen as the enemy of the environment – a greenhouse gas that is largely responsible for the global warming that is rapidly changing the Earth’s climate. In fact, harnessed properly, it is a highly effective cooling agent that is a friend to the planet and which can offer massive advantages in high capacity applications such as mission critical data cooling.
Trox Advanced IT Cooling Systems (AITCS) – the supplier of the acclaimed CO2OLrac cooling system for ultra-powerful computers called blade servers – has expanded its portfolio of supply and install mission critical cooling systems with the development of CO2OLdesk, a powerful carbon dioxide-based cooling system that can counteract the escalating heat loads produced by PCs in dealer desks on the trading floors of financial institutions.

The development is founded on the highly effective ideal of absorbing the dealer’s in-desk PC heat directly ‘at source’. It provides high capacity cooling within trading floors, aiding optimum user comfort without impacting on the background room air conditioning. The system, which uses CO2 as the refrigerant, can deliver up to 30% energy savings over chilled water alternatives.

But the advantages don’t stop there. CO2 is electrically benign and therefore poses no danger to computers or cabling. It also has no impact on the ozone layer and is a low cost gas in abundant supply as a waste by-product of industrial processes. It can therefore be considered as having a negative global warming potential in IT cooling applications because the power savings resulting from increased energy efficiency will reduce CO2 emissions at the power station: for a 250kW system this may be as much as 290 tonnes per year.

The CO2OLdesk system therefore has a dual environmental benefit. Not only does it sequester waste CO2 from industrial processes, but it also reduces power station emissions during operation as it cools the trading floor more efficiently than chilled water (CHW) alternatives.

CO2OLdesk provides the perfect opportunity to positively and safely use the CO2 that could potentially be harmful to the environment at a rate of around 7kg per kW of cooling. That means the carbon footprint is dramatically improved as the emissions reduce at a staggering rate of almost one tonne per kW of cooling.

On top of this, CO2 offers seven times the cooling capacity of CHW because the latent heat capacity of carbon dioxide is 182kJ/kg compared to the specific heat capacity of H2O = 4.2kJ/kg K. What this means is that:

  • 1kg of CO2 absorbs 182kJ of energy in its ‘phase change’.
  • 1kg of H2O absorbs 4.2kJ of energy for a 1ºC rise in temperature.
  • CHW flow/return 6/12ºC 1kg of H2O absorbs 25.2kJ.
  • Therefore, 1kg of CO2 absorbs seven times more energy than water (182kJ / 25.2kJ = 7.22).

The higher cooling capacity of CO2 allows lower volume flows and therefore smaller diameter distribution pipe work and smaller, slimmer cooling units. And CO2OLdesk’s slim construction means it can be co-ordinated with the shallowest floor voids. This opens up a whole new vista for property management companies by widening the choice of properties suitable for dealer room applications. So, for example, existing low height buildings can be used as dealer rooms; impossible if conventional IT cooling is in place.

Typically, CO2OLdesk works by creating a micro climate under the dealer’s desk to house the PCs behind the thermally insulated and brush sealed modesty panels. This co-ordinated approach ensures that the PC heat and CO2OLdesk are perfectly aligned to achieve efficient ‘at source’ cooling, while also providing the best possible hardware environment.

The self balancing, load driven system allows greater flexibility for PC deployment. Excessive peak equipment loads can, through consultation, be managed to accommodate peaks that are above the unit’s cooling capacity as a more holistic ‘levelling-out’ approach is taken to continuous desk runs and their equipment loads. In-desk temperature monitoring is used as a platform for IT and M&E operations to remain in sync to ensure overall ‘desk run’ cooling is achieved.

CO2OLdesk explained

CO2OLdesk is integrated with the raised floor and dealer desks. The insulated desk chamber creates a micro climate so that all of the PC heat is absorbed by CO2OLdesk. The unit is fully compatible with all types of desks.

CO2OLdesk, which is supplied with liquid carbon dioxide at 14ºC, draws the PC’s rejected heat across a heat exchanger and fully absorbs the PC load, enabling the equipment to remain at its design temperature with no impact on the traders. Laboratory tests prove user comfort is improved with CO2OLdesk since it can reduce local ambient desk temperatures from an intolerable 30ºC to a very comfortable 22ºC.

Three alternative designs are available to satisfy specific client requirements:

Recessed: The 200mm deep unit fits within the floor void, finishing flush with the finished floor level and replacing continuous rows of tiles. The unit has a cooling capacity of 1,500W and with its internal baffle plates and multi-deck fans can accommodate PC’s arranged in either a single or two way formation.

Semi recessed: The 150mm deep unit sits 75mm above the FFL to enable integration with shallow voids of just 120mm. The unit’s floor pedestal support system acts as an air inlet/outlet deflector. Interconnecting pipework and wiring between CO2OLdesk units is above the FFL. The unit has a cooling capacity of 1,200W and is designed to suit PC’s arranged in a one-way formation.

Surface mounted: The slim 120mm deep units sit on the raised floor. It is ideally suited to retro-fit applications as the desks can remain in place during installation. The unit has a cooling capacity of 1,200W.

All three systems use stainless steel heat exchangers in order to satisfy the highest levels of robustness and resilience.

Achieving reductions

Consultant hurleypalmerflatt performed an analysis of the CO2OLrac system (CO2OLdesk’s blade server-cooling cousin) installed at Imperial College, London, in order to compare a conventional low density chilled water system with a high density CO2 data centre cooling system. It found that, for a 250kW system, using the high capacity CO2OLrac cooling system would result in a saving of 290 tonnes of carbon per year which would otherwise be given off at the power station to generate electricity to run the system.

Trox AITCS has installed 1.7MW of CO2OLrac systems, so the reduction in carbon generation from power stations as a result of these installations totals almost 1,500 tonnes per year. This equates to 1,000 tonnes per MW. On top of this, around 1.75 tonnes of CO2 per MW is recycled as a cooling medium in the CO2OLrac systems. So a CO2-based cooling system like CO2OLdesk and CO2OLrac offers a double carbon footprint benefit: It removes potentially damaging CO2 from the ecology and results in less CO2 being produced at the power station.

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