In 2007, a partnership was formed by the city of Lansing, Mich.; the state of Michigan; Accident Fund Insurance Co. of America and its parent company, Blue Cross Blue Shield of Michigan; developer and construction manager The Christman Co.; Lansing Economic Development Corp.; and Lansing Board of Water & Light (LBWL) to renovate the decommissioned Ottawa Street Power Station in Lansing into Accident Fund's new world headquarters. The partnership required LBWL to construct a separate plant to provide chilled water, which previously was supplied by equipment in the Ottawa Street Power Station's basement.

LBWL contracted with Stanley Consultants to provide engineering and construction services for the new Roy E. Peffley Chilled Water Plant. The consulting firm used four new 2,000-ton electric centrifugal chillers in the Peffley plant, which replaced the Ottawa Street Power Station's four 2,000-ton steam-turbine centrifugal chillers. Additionally, one of the Ottawa facility¡¯s 2,000-ton electric units was relocated to the new plant.

Several goals were established for the new plant's construction:

• Improved energy and operational efficiency. To save energy, several environmentally friendly, yet economical, choices were made by the plant's project team.
• Complementary architecture. The new plant is visible in downtown Lansing, so the exterior design was of critical importance.
• Budget control and building information modeling (BIM). It was important to maintain costs throughout the project and keep change orders to a minimum with the use of BIM.
• Improved maintenance operations. Because maintenance access to equipment at the Ottawa Street Power Station was extremely tight, LBWL sought to improve maintenance operations at the new plant.

Chiller Selection
First, the number and size of the chillers for the Peffley plant had to be determined. To aid the chiller-selection process prior to design, the project team evaluated recent historical data for the production and utilization of chilled water.

A historical review of chilled-water loads for the buildings to be served was completed, and a load-duration curve was created (Figure 1). The curve indicated the chilled-water system had a peak load just short of 5,000 tons. Although loads of 1,000 tons or less occurred during most operational hours, LBWL expected loads to increase when new buildings were added to the loop. As a result, 2,000-ton chillers were utilized and part-load performance was maximized for the initial years of operation. Three chillers were installed to meet peak load, and a fourth unit provided "N+1" redundancy. Although the 2,000-ton electric motor-driven chiller was relocated to the new plant, it was not placed into operation. It will be connected and placed into service after load growth has occurred.

Energy/Operational Efficiency
Chilled-water pumping. The Ottawa Street Power Station's chilled-water plant utilized a primary-secondary pumping scheme to deliver chilled water. A primary-secondary system consists of two circuits: a constant-volume production loop (primary) and a variable-volume distribution loop (secondary). The primary loop circulates chilled water through chillers, and the secondary loop circulates chilled water through a distribution system (Figure 2).1