The CHP containers were custom designed to fit the yard, sometimes with only a foot to spare between the CHP and existing equipment and a screen wall. The 3-story tall screen wall was extensively modified with roll-up doors and louvers to provide access and ventilation. The hotel has three separate 13.2kV utility services feeding a single medium voltage switchgear lineup. With no extra space in the electrical room, existing cabinets had to be modified to interconnect the CHP. Unison worked with the OEM, Schneider Electric/Square D to design, fabricate and install the modifications as well as re-program the protective relays and PLC to allow the gear to function automatically in all possible conditions including single, double and triple utility outages. One of the team’s highest-profile projects completed to date is a large Hotel Resort & Convention Center project in the Washington metro area – a 6.0MW CHP system consisting of 3 x 2,000kW engines. The system was designed, installed and commissioned on an aggressive 15-month timeline from contract signing to commercial operation. A particularly challenging part of the design was simply setting the equipment. The available space was a 56’x52’ mechanical yard; a tight fit for three large generators and three 2500kVA step-up transformers.
To minimize the impact to the hotel’s guests and conventions all outage work had to be completed during times of low occupancy, typically Sunday nights. To meet the utility’s requirements for telemetry for and trip control, Unison installed a wireless radio frequency system to communicate with the utility control center and related facility serving sub-stations in the event of a grid outage.
The CHP thermal delivery operates in parallel with the hotel’s existing hydronic boiler plant. The original plant consists of 4 boilers connected to the hotel in a primary-secondary loop. During the summer the CHP is expected to provide all heat necessary for the primary boiler loop. During the winter, the CHP will be the primary source of heat and will be supplemented by the boilers. Only one boiler will need to fire vs. the 2 or 3 that were required prior to CHP installation.