From my latest piece on the Arborus Efficiency Journal:
The Winter 2014 issue of Higher Performing Buildings has a great article on the new Bill & Melinda Gates Foundation Headquarters, built in Seattle in 2011. Since the Foundation intends to occupy the building for the long term, the major heating, ventilating and air conditioning system design decisions were based on a total cost of ownership analysis. It’s interesting to see how this analysis informed the design of the central cooling plant. A number of configurations were analyzed and, surprisingly, the one that came out on top is an air-cooled chiller plant connected to a thermal energy storage system. This result is surprising for two reasons: 1) electricity costs in Seattle are low and do not include peak demand charges or time-of-use rates and 2) air-cooled chillers tend to underperform water-cooled systems that use a cooling tower for heat rejection ...