RESEARCH

Data center waste heat recovery is an energy efficient and economically viable option when the data center is near other facilities on the same site. This study explores boosting the vapor from a data center’s two-phase server waste heat using a novel vapor re-compression system featuring an oil-free compressor. The boosted waste heat contains sufficient thermal energy to drive an absorption refrigeration (AR) chiller to obtain a stream of cold fluid. Alternatively, the chiller can be bypassed so the boosted heat is used directly in the neighboring facility. These approaches are modeled to enable the estimation of energy savings and economic benefits under different cooling and heating loads. These calculations also dictate situations where the compressor should be bypassed and the server exhaust simply sent to the condenser for rejection to the ambient. The analysis is focused on the waste heat recovery and re-use potential of a 1 MW data center with a process industry and a hotel in the vicinity. The study focuses on two key issues: 1) the overall efficiency of the waste heat system, including neighboring sites, when boosted with the novel re-compression system versus a turn-key heat pump and 2) the optimal utilization of the hot or cold streams generated based on a thermo-economic analysis.

This project hypothesizes that the current QuantaCool, Corporation microevaporator cold plate (MCP) manufacturing approach can be replaced by a less-expensive compressed metal-foam (CMF)-based MCP with a loss in MCP effectiveness of less than 10%. 2-phase cooling using MCPs provide a more effective means than traditional air cooling to remove the heat from computer servers in data centers, and the growth in server heat output increasingly makes MCP-based cooling attractive as a cooling option. The traditional approaches to MCP manufacturing (e.g., skiving or etching micro-structured features) limits their implementation in hyperscale data center facilities where tens of thousands of servers are housed. Replacing traditionally-manufactured MCPs with CMF-based MCPs, on the other hand, could allow for large-scale production at a reduced cost. This project will explore the influence of metal foam properties, including the amount of applied metal foam compression, through designing, fabricating, and testing CMF-based MCPs to compare their performance with traditionally-fabricated MCPs. A heat exchange model will be developed to characterize the CMF-based MCPs based on CMF features. The testing will include a refrigerant-based cooling loop featuring a heat source cooled by a 2-phase MCP. The consistency of a batch of optimally-designed CMF-based MCPs will also be examined. Funding will be used to support Villanova MSME student Lucas Arrivo, and results from this work will provide the basis for his Master’s thesis, a conference publication and presentation, and a journal publication. Lucas will work closely with Manufacturing Fellow Steven Schon, the CTO of QuantaCool, Inc. The project forges a partnership between QuantaCool and PA-based metal foam supplier GoodFellow USA. The project has a strong synergy with existing data center research at Villanova in the NSF I/UCRC in Energy-Smart Electronic Systems (ES2), which is led by PI Wemhoff.

Food systems are estimated to contribute between 19% and 29% of global greenhouse gas (GHG) emissions and to account for about 70% of global freshwater use. In the US, consumption of food-away-from-home (FAFH) has doubled in 2006 compared with the 1970s and accounts for half of household food expenses. This trend of dining out continues due to factors such as increased female employment and household income. The environmental burden of food away from home stems from two sources. The direct environmental impact is from:

• Food preparation activities including raw material storage, cooking, and food display
• Energy consumption from providing a dining and working environment through heating, ventilation, and air conditioning

Second, the indirect environmental impact from:

• The production, processing and transportation of raw material
• The GHG emissions from the landfill of organic food waste

MSAL is focused on improving environmental sustainability through more efficient use of the food system.

Supplementary material for the paper “Comparing Greenhouse Gas Emissions Associated with Food Away From Home Versus Food At Home in the United States” can be obtained by request to Dr. Aaron Wemhoff.

Thermal energy storage plays an important role in enabling accessibility to intermittent sustainable energy sources, in particular solar energy. Furthermore, thermal energy storage can be used in passive cooling of portable electronics (e.g., smart phones) to lengthen battery life, and also as a thermal barrier in building envelopes. Thermal energy storage is commonly implemented using phase change materials, where the latent heat associated with a solid-liquid phase change is used to store thermal energy.

Thermal energy storage is most effective when the material is heated evenly such that at any point in time the material is at a uniform temperature. The desired behavior is met when thermal diffusivity is large. This is difficult with commonly-used organic phase change materials such as alkane chains (paraffin) and unsaturated acids. Our approach to improve this thermal diffusivity of these materials is to embed highly-conducting nanomaterials such as carbon nanotubes or graphite nanofibers to create a composite material.