Energy-Efficient Computing and Data Centers

7PUE, ERE and TCO of Various Cooling Solutions

7.1. Power usage effectiveness, energy reuse effectiveness and total cost of ownership

7.1.1. Power usage effectiveness and energy reuse effectiveness

When we introduced energy reuse effectiveness (ERE) in [I.3], we used the definition given by Patterson et al. (2010) where ERE measures the benefit from waste heat produced by the data center without taking into account the potential benefit to the data center. In other words, the energy reuse from [I.3] is the waste heat energy dissipated by the IT equipment and reused outside the data center as we will see with National Renewable Energy Laboratory (NREL) Research Support Facility (RSF) in section 7.2.1. With such an approach, ERE is defined by:

[I.3]

with:

[7.1]

where ERF is the energy recovery factor:

[7.2]

If we want to measure the impact when waste heat is reused by the data center itself as with adsorption chillers producing cold water (see section 3.7) as done with CoolMUC at Leibnitz Supercomputing Center (LRZ) (see section 7.2.2), we have to introduce a new definition of ERE, which we will call ERE_DC given by:

[7.3]

Where energy_-DCreused is the waste heat energy effectively ...