Abstract-We present the design and evaluation of the heat recovery system for KTH's Lindgren, Stockholm's fastest supercomputer, a Cray XE6. Lindgren came into service in 2010 and has since been primarily used for complex numeric simulations of fluid mechanics and computational chemistry and biology. The heat exchange system collects the wasted heat from Lindgren's 36,384 CPU cores and transfers it via the standard district heating and cooling system to a neighboring building which houses the Chemistry laboratories. We analyze the impact of Lindgren's heat recycle system as a function of outside temperature and we estimate the system's carbon emission savings. Since the original installation of Lindgren in 2010, it has become common practice to use water cooling systems for supercomputers, as water is a better heat transfer medium than air. We discuss the relevant design lessons from Lindgren as they relate to practical and sustainable waste heat recovery designs for today's platforms. Finally, we estimate that the recovered heat from Lindgren reduced the carbon emissions by nearly 50 tons over the 2012-13 winter, the sample period of our analysis.Index Terms-Supercomputer, data center, waste heat recovery, heat exchanger, waste energy reuse, urban district heating and cooling, high-performance computing.

We carry out 1D hydrodynamical simulations of the evolution of a spherically symmetric supernova remnant (SNR) subject to an external radiation field (ERF) that influences the cooling and heating rates of the gas. We consider homogeneous media with ambient hydrogen number densities nH, 0 of 0.1 and 1 cm−3 permeated by an average radiation field including the cosmic microwave, extragalactic, and Galactic backgrounds, attenuated by an effective column density NH, eff from 1018 to 1021 cm−2. Our results may be classified into two broad categories: at low NH, eff, the ERF presents little absorption in the ultraviolet (ionising) regime, and all the ’unshielded’ cases feature an equilibrium temperature Teq ∼ 7000 K below which the ambient gas cannot cool further. In this scenario, the SNR develops a nearly isothermal shock profile whose shell becomes thicker over time. At higher NH, eff, the ERF is heavily absorbed in the UV range, yielding a roughly constant heating function for temperatures ≲ 104 K. These ‘shielded’ cases develop a thin, cold and dense shell throughout their evolution. Energy and momentum injection to the medium do not change significantly between both scenarios, albeit luminosity is higher and more uniformly distributed over the shell for unshielded SNR.

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This work discusses the main analogies and differences between the deterministic approach underlying most cosmological N-body simulations and the probabilistic interpretation of the problem that is often considered in mathematics and statistical mechanics. In practice, we advocate for averaging over an ensemble of S independent simulations with N particles each in order to study the evolution of the one-point probability density Ψ of finding a particle at a given location of phase space (x , v ) at time t. The proposed approach is extremely efficient from a computational point of view, with modest CPU and memory requirements, and it provides an alternative to traditional N-body simulations when the goal is to study the average properties of Nbody systems, at the cost of abandoning the notion of well-defined trajectories for each individual particle. In one spatial dimension, our results, fully consistent with those previously reported in the literature for the standard deterministic formulation of the problem, highlight the differences between the evolution of the one-point probability density Ψ(x, v, t) and the predictions of the collisionless Boltzmann (Vlasov-Poisson) equation, as well as the relatively subtle dependence on the actual finite number N of particles in the system. We argue that understanding this dependence with N may actually shed more light on the dynamics of real astrophysical systems than the limit N → ∞.

An advanced patented process [1] for generating power from waste heat sources can be put to use in Industrial operations where much of the heat is wasted and going up the stack. This waste heat can be efficiently recovered to generate electrical power. Benefits include: use of waste industrial process heat as a fuel source that, in most cases, has represented nothing more than wasted thermal pollution for decades, stable and predictable generation capability on a 24 × 7 basis. This means that as an efficiency improvement resource, unlike wind and solar, the facility continues to generate clean reliable power. One of the many advantages of generating power from waste heat is the advantage for distributed generation; by producing power closer to its ultimate use, it thereby reduces transmission line congestion and losses, in addition, distributed generation eliminates the 4% to 8% power losses due to transmission and distribution associated with central generation. Beneficial applications of heat recovery power generation can be found in numerous industries (e.g. steel, glass, cement, lime, pulp and paper, refining, electric utilities and petrochemicals), Power Generation (CHP, MSW, biomass, biofuel, traditional fuels, Gasifiers, diesel engines) and Natural Gas (pipeline compression stations, processing plants). This presentation will cover the WOW Energy technology Organic Rankine Cascading Closed Loop Cycle — CCLC, as well as provide case studies in power generation using Internal Combustion engines and Gas Turbines on pipelines, where 20% to 40% respectively additional electricity power is recovered. This is achieved without using additional fuel, and therefore improving the fuel use efficiency and resulting lower carbon footprint. The economic analysis and capital recovery payback period based on varying Utility rates will be explained as well as the potential Tax credits, Emission credits and other incentives that are often available. Further developments and Pilot plant results on fossil fired plant flue gas emissions reductions will be reported to illustrate the full potential of the WOW Energy CCLC system focusing on increasing efficiency and reducing emissions.