Ingmar Meijer

Waste heat recovery in supercomputers and 3D integrated liquid cooled electronics

Ever increasing device density in electronic chips is beneficial for enhancing their computing efficiency. However, it also introduces severe challenges with respect to cooling solution which are indispensible for ensuring a reliable chip operation. Such steady miniaturization will soon render the traditional air cooling strategies futile and make the switching to liquid cooling inevitable. Superior thermal properties and ubiquitous availability make water the most suitable candidate as coolant. Building up on the reported studies in the literature, which have already established the feasibility of water as coolant, here we show that the superior thermal properties of water make it possible to cool electronic chips and data centers using hot water with inlet temperature up to 60°C. The concept is demonstrated through measurements on a copper made scalable manifold microchannel heat sink and a hot water cooled data center prototype. The high exergetic efficiency achieved using hot water cooling should make it possible to reuse the heat otherwise discarded in data centers and therefore improve the overall system efficiency and lower the carbon foot print of the data centers. Finally, the encouraging results are used to model water cooling of 3D chip stacks using an interlayer integrated cooling approach. The model results are compared with measurements on a model simulator and good agreement is found, which lays the ground work for realizing a model based optimization of integrated cooling structures for 3D chip stacks.

Roadmap towards ultimately-efficient zeta-scale datacenters

Chip microscale liquid-cooling reduces thermal resistance and improves datacenter efficiency with higher coolant temperatures by eliminating chillers and allowing thermal energy re-use in cold climates. Liquid cooling enables an unprecedented density in future computers to a level similar to a human brain. This is mediated by a dense 3D architecture for interconnects, fluid cooling, and power delivery of energetic chemical compounds transported in the same fluid. Vertical integration improves memory proximity and electrochemical power delivery creating valuable space for communication. This strongly improves large system efficiency thereby allowing computers to grow beyond exa-scale.

CooLMUC-2: A supercomputing cluster with heat recovery for adsorption cooling

In High Performance Computing (HPC), chiller-less cooling has replaced mechanical chiller supported cooling for a significant part of the HPC system resulting in lower cooling costs. Still, other IT components and IT systems remain that require air or cold water cooling. This work introduces CooLMUC-2, a high-temperature direct-liquid cooled (HT-DLC) HPC system which uses a heat-recovery scheme to drive an adsorption refrigeration process. Using an adsorption chiller is at least two times more efficient than a mechanical chiller for producing needed cold water. To this date this is the only installation of adsorption chillers in a data center combining a Top500 production level HPC system with adsorption refrigeration. This prototype installation is one more step towards a 100% mechanical chiller-free data center. After optimization of the operational parameters of the system, the adsorption chillers of CooLMUC-2 consume just over 6kW of electrical power to not only remove 95kW of heat from the supercomputer, but also to produce more than 50kW of cold water. This paper presents initial measurements characterizing the heat-recovery performance of CooLMUC-2 at different operating conditions.

Case Study: LRZ Liquid Cooling, Energy Management, Contract Specialities

This presentation explores energy management, liquid cooling and heat re-use as well as contract specialities for LRZ: Leibniz-Rechenzentrum.

Advances in silicon oxynitride waveguides

The silicon-oxynitride planar waveguide technology combines a minimum bending radius of 0.55 mm with excellent optical properties. It is an ideal platform for the realization of high functionality optical devices, latest examples will be presented.

HOT WATER COOLED ELECTRONICS FOR HIGH EXERGETIC UTILITY

Cooling poses as a major challenge in the IT industry because recent trends have led to more compact and energy intensive microprocessors. Typically microprocessors in current consumer devices and state-of-the-art data centers are cooled using relatively bulky air cooled heat sinks. The large size heat sinks are required due to the poor thermophysical properties of air. In order to compensate for the poor thermal properties of air, it is typical to use chillers to pre-cool the air below the ambient temperature before feeding it to the heat sinks. Operating the chillers requires additional power input thereby making the cooling process more expensive. The growing cooling demand of electronic components will, however, render these cooling techniques insufficient. Direct application of liquid-cooling on chip level using directly attached manifold microchannel heat sinks reduces conductive and convective resistances, resulting in the reduction of the thermal gradient needed to remove heat. Water is an inexpensive, nontoxic and widely available liquid coolant. Therefore, switching from air to water as coolant enables a much higher coolant inlet temperature without in any way compromising the cooling performance. In addition, it eliminates the need for chillers and allows the thermal energy to be reused. All these improvements lead to higher thermal efficiency and open up the possibility to perform electronic cooling with higher exergetic efficiency. The current work explores this concept using measurements and exergetic analyses of a manifold microchannel heat sink and a small scale, first of its kind, hot water cooled data center prototype. Through the measurements on the heat sink, it is demonstrated that the heat load in the state-of-the-art microprocessor chips can be removed using hot water with inlet temperature of 60°C. Using hot water as coolant results in high coolant exergy content at the heat sink outlet. This facilitates recovering the energy typically wasted as heat in data centers, and can therefore result in data centers with minimal carbon footprint. The measurements on both the heat sink and the data center prototype strongly attest to this concept. Reuse strategies such as space heating and adsorption based refrigeration were tested as potential means to use the waste heat from data centers in different climates. Application-specific definitions of the value of waste heat were formulated as economic measures to evaluate potential benefits of various reuse strategies.Copyright