Cooling requirements fueled the collapse of a desert bird community from climate change.

Climate change threatens global biodiversity by increasing extinction risk, yet few studies have uncovered a physiological basis of climate-driven species declines. Maintaining a stable body temperature is a fundamental requirement for homeothermic animals, and water is a vital resource that facilitates thermoregulation through evaporative cooling, especially in hot environments. Here, we explore the potential for thermoregulatory costs to underlie the community collapse of birds in the Mojave Desert over the past century in response to climate change. The probability of persistence was lowest for species occupying the warmest and driest sites, which imposed the greatest cooling costs. We developed a general model of heat flux to evaluate whether water requirements for evaporative cooling contributed to species' declines by simulating thermoregulatory costs in the Mojave Desert for 50 bird species representing the range of observed declines. Bird species' declines were positively associated with climate-driven increases in water requirements for evaporative cooling and exacerbated by large body size, especially for species with animal-based diets. Species exhibiting reductions in body size across their range saved up to 14% in cooling costs and experienced less decline than species without size reductions, suggesting total cooling costs as a mechanism underlying Bergmann's rule. Reductions in body size, however, are unlikely to offset the 50 to 78% increase in cooling costs threatening desert birds from future climate change. As climate change spreads warm, dry conditions across the planet, water requirements are increasingly likely to drive population declines, providing a physiological basis for climate-driven extinctions

Feasibility study of a combi-pv panel for greenhouse energy supply and water recovery by nightly radiation towards the sky

In southern European areas, characterized by high irradiation, the use of water for both evaporative cooling systems and hydroponic fertigation, represents a serious drawback for crop cultivation under cover. Water recovery systems seem to be an attractive solution, especially when they are integrated in the greenhouse construction. In this research, a feasibility study of applying a water recovery system driven by a combi-PV panel, in a semi-closed greenhouse was carried out. The prototype combi-PV panel was made by coupling an amorphous silicon panel with a sump stacked on the rear PV panel surface and filled with saline water. The system is driven by a cold-heat sink which is the PV panel itself. During night, the combi-PV panel exploits the radiative cooling of a ‘gray’ surface towards clear sky, chilling the water in the sump. In opposition, during day-time, the water in the sump is heated at a temperature higher than the environment. Thus, the water vapour will be condensing on the rear panel surface during night, being the warm air circulation facilitated by bouyancy effect. The evaluation of the system is in progress in order to assess the real amount of energy irradiated and consequently the water-drips to be collected on a proper surface inside the sump. The condensed water can be mixed with saline water to reduce the salinity and be used for fertigation

The effect of cooling prior to and during exercise on exercise performance and capacity in the heat: a meta-analysis

Exercise is impaired in hot, compared to moderate, conditions. The development of hyperthermia is strongly linked to the impairment and as a result, many different strategies have been investigated to combat this. This meta-analysis focused on one of the most popular strategies: cooling. Pre-cooling has received the most attention but more recently cooling applied during the bout of exercise has also been investigated and both were reviewed. We conducted a literature search and retrieved twenty-eight articles which investigated the effect of cooling administered either prior to (n=23) or during (n=5) an exercise test in hot (WBGT >26°C) conditions. Mean and weighted effect sizes (Cohen’s d) were calculated. Overall, pre-cooling has a moderate (d=0.73) effect on subsequent performance but the magnitude of the effect is dependent upon the nature of the test. Sprint performance is impaired (d=-0.26) but intermittent performance and prolonged exercise are both improved following cooling (d=0.47 and d=1.91 respectively). Cooling during exercise also has a positive effect on performance and capacity (d=0.76). Improvements were observed in studies with and without cooling-induced physiological alterations and the literature supports the suggestion of a dose-response relationship between cooling, thermal strain and improvements in performance and capacity. In summary, pre-cooling can improve subsequent intermittent and prolonged exercise performance and capacity in a hot environment but sprint performance is impaired. Cooling during exercise also has a positive effect on exercise performance and capacity in a hot environment

Heat transfer to two-phase air/water mixtures flowing in small tubes with inlet disequilibrium

The cooling of gas turbine components was the subject of considerable research. The problem is difficult because the available coolant, compressor bleed air, is itself quite hot and has relatively poor thermophysical properties for a coolant. Injecting liquid water to evaporatively cool the air prior to its contact with the hot components was proposed and studied, particularly as a method of cooling for contingency power applications. Injection of a small quantity of cold liquid water into a relatively hot coolant air stream such that evaporation of the liquid is still in process when the coolant contacts the hot component was studied. No approach was found whereby heat transfer characteristics could be confidently predicted for such a case based solely on prior studies. It was not clear whether disequilibrium between phases at the inlet to the hot component section would improve cooling relative to that obtained where equilibrium was established prior to contact with the hot surface

iDataCool: HPC with Hot-Water Cooling and Energy Reuse

iDataCool is an HPC architecture jointly developed by the University of Regensburg and the IBM Research and Development Lab B\"oblingen. It is based on IBM's iDataPlex platform, whose air-cooling solution was replaced by a custom water-cooling solution that allows for cooling water temperatures of 70C/158F. The system is coupled to an adsorption chiller by InvenSor that operates efficiently at these temperatures. Thus a significant portion of the energy spent on HPC can be recovered in the form of chilled water, which can then be used to cool other parts of the computing center. We describe the architecture of iDataCool and present benchmarks of the cooling performance and the energy (reuse) efficiency.Comment: 12 pages, 7 figures, proceedings of ISC 201

Applicability of solar desiccant cooling systems in Algerian Sahara: Experimental investigation of flat plate collectors

The increasing interest in the development of solar cooling technologies to their various economic and impressive environmental benefits, conducted us to study the feasibility of solar desiccant cooling systems in Algerian Sahara, particularly in the region of Biskra. Thus, we present in this paper, the results of an experimental investigation of solar flat plate collectors (FPCs) to test and estimate their heat regeneration capacity for solid desiccant cooling applications. The applicability of both Pennington and Dunkle cycles taking into account the effects of some parameters such as outdoor humidity and temperature and hot air temperature required to regenerate the desiccant wheel have been studied. From the psychrometric analysis, it was found that the Dunkle cycle is suitable in warm and semiarid climate. In addition, this study has allowed us to show that the temperature achieved by the flat plate solar air heaters in a large band of air flow rate can satisfy the energy needs for the dehumidification in desiccant cooling systems. Hot water produced by the solar water heaters and the stored one are in the operating temperature gap of the system (50-80 °C)

Resuming safe operation of building water systems--risk of Legionnaires' disease

Legionnaires' disease is a serious disease caused by Legionella bacteria, which thrive in stagnant, warm water. Outbreaks of this disease have been associated with cooling towers, evaporative condensers, showers, faucets, hot tubs/whirlpool spas, and other sources of aerosolized water. Legionella bacteria favor a temperature of 25-42 C (77-108 F) for growth. Because many buildings and cooling towers may be shut down during or after a disaster, the water in those systems may sit stagnant for days to weeks--providing an increased risk of Legionnaires' disease once the systems are restarted."April 28, 2006."At head of title: Disaster safety.Mode of access: Internet from the CDC web site as an Acrobat .pdf file (80.93 KB, 2 p.)

Performing successfully in the heat at the 2004 Olympic Games in Athens: Which active cooling strategies represent best practice for endurance athletes

Previous research using athletes has documented that precooling can improve endurance performance, especially in warm conditions. However, research comparing performance following different cooling techniques which are incorporated into a prerace routine is rare. Purpose: The purpose of this study was to compare the effects of two precooling techniques on cycling time trial performance in warm conditions. Methods: Six endurance trained, regionally competitive cyclists completed one maximal graded exercise test (V02peak 71.4 ±3.2 ml’kg-1min-1) and four ~40 min laboratory cycling time trials in a heat chamber (34.3 ± 1.1°C; 41.2 ± 3.0% relative humidity (rh)) using a fixed power-variable power format. After familiarisation, cyclists prepared for the time trial using two different precooling strategies and a control condition administered in a counterbalanced order. The three trials included: 1) no cooling (Control), 2) cooling jacket for 40 min (Jacket) or 3) 30 min water immersion (29°C to 24°C at a rate of 0.2°C\u27min-1 ) followed by cooling jacket for 40 min (Combination). Comparisons were made using a two-way ANOV A with repeated measures and Student\u27s paired t-tests where appropriate. Results: Rectal temperature (Tre) prior to the time trial was 37.8 ± 0.1°C in Control, similar in Jacket (37.8 ± 0.3°C) and significantly lower in Combination (37.1 ±0.2 C, p \u3c 0.01). Blood lactate during each treatment was similar except for the final readings (Control = 15.8 ± 4.4 mM, Jacket = 19.8 ± 4.3 mM and Combination = 17.5 ± 4.0 mM, p \u3c 0.005). Heart rate was similar throughout the time trial for each treatment. Compared to the Control trial, performance time was similar for Jacket (-16 ± 36s, -1.5%; p = 0.34) but faster for Combination (-42 ± 25s, -3.8%; p = 0.01). The pacing strategy for Control and Combination were similar (gradually reducing split times) but unique for Jacket (started with a fast split time followed by a temporary increase in split times). Conclusions: A combination precooling strategy incorporating immersion in cool water followed by the use of a cooling jacket can: 1) produce decreases in Tre that persist throughout a warm up and 2) improve laboratory cycling time trial performance. The effects of a cooling jacket alone on Tre are subtle and do not appear to persist throughout a warm up. Further research is required to understand the influence of cooling jackets on pacing strategy during time trials performed in the heat