Oil-free technology delivers 5-star energy savings at the Shanghai Xijiao Hotel

Friday, 10 May 2019

A history of prestige

Shanghai Xijiao Hotel is a state-owned hotel with more than 40 years of dignified history. Established in 1960, it has catered to more than 100 domestic and overseas political dignitaries including the Queen of Great Britain, the Emperor of Japan, the Premier of Germany, US Presidents Bush and Obama, and President Putin of Russia. Successive PRC national leaders such as Mr. Mao Zedong, Deng Xiaoping, Jiang Zemin, and Hu Jintao have also stayed in the hotel. It is a place that often hosts meetings for important national affairs and high-end business activities.

The hotel’s luxurious facilities cover 105,000 square meters and include an internal courtyard, a sports center, and a villa. The courtyard houses the conference center, guest rooms, and hotel service area.

A time for renewal

At the heart of the internal courtyard’s air conditioning system were five screw chillers, which had been operating for more than 10 years. Before the retrofit project began, engineers conducted a test on the two 265-ton (930 kW) screw chillers, which were most frequently used. They concluded that energy efficiency was seriously lacking and that the COP was less than nominal. They also observed that the units were difficult to start under low cooling water temperature conditions, and the water pumps and cooling towers were aged, resulting in serious performance degradation.

An elegant solution

The hotel decided to replace the screw chillers with two 300 TR (1055 kW) maglev oil-free flooded centrifugal chillers, both paired with two Danfoss Turbocor® Compressors. The old water pumps were also upgraded to a new set of highly effective pumps and frequency converters. The packing of the cooling tower was renewed as well.

Table 1 Equipment parameters before and after the retrofit

Old New
Screw chillers Maglev oil-free centrifugal chillers
Model: RTHB300 Model: BSMW-1060
Cooling capacity: 930 kW Cooling capacity: 1 060 kW
Motor power: 179 kW Motor power: 190.3 kW
Q’ty: 2 Q’ty: 2

Proven performance

On June 20, 2014, performance testing was carried out on the maglev oil-free chiller and the old screw chillers (as shown in the following figures).

Table 2 Testing Data of Maglev Oil-free Chiller at Different Times

  11:00 11:30 12:00 12:30 13:00 13:30
Measured compressor power/kW 137.3 140.1 143.4 145.6 151.2 149.0
Water flow/(m3/h) 235.0 237.0 240.9 235.9 237.7 237.1
Cooling water inlet temperature/°C 7.3 7.2 7.4 7.3 7.3 7.3
Cooling water outlet temperature/°C 10.7 10.7 10.7 10.7 10.7 10.8
COP 6.75 6.87 6.43 6.39 6.20 6.46

Table 3 Testing Data of Screw Chillers at Different Times

  14:30 15:00 15:30 16:00 16:30 17:00
Measured compressor power/kW 167.0 170.2 173.3 175.4 181.1 178.0
Water flow/(m3/h) 236.0 238.0 240.5 243.6 247.2 247.4
Cooling water inlet temperature/°C 9.3 9.2 9.3 9.3 9.3 9.3
Cooling water outlet temperature/°C 11.3 11.2 11.2 11.3 11.3 11.3
COP 3.28 3.24 3.06 3.22 3.17 3.22

To see how much energy the new compressors were able to save, the project team first compared the energy consumption at the hotel for July through December in 2014 with consumption during the same period in 2011. The difference was significant – the hotel reduced their electrical energy usage by 1,286,900 kWh.

However, to determine how much of that savings was due to the new maglev compressors, the team needed to dig a bit deeper, so they turned to a third-party report, the Research on Energy Consumption Characteristics of Star-Rated Hotels in Shanghai. According to the report, the average ratio of electrical energy usage by air conditioning systems for five-star-rated hotels in Shanghai is 30.19%. Based on that figure, the team concluded that the maglev oil-free centrifugal chillers helped Shanghai Xijiao save 388,515 kWh – a 24.2% reduction in energy usage compared to the old screw chillers. The team estimates that energy savings could reach as high as 50% if all five screw chillers were replaced with maglev oil-free chillers.

A bright future

The retrofit project was a huge success and received a designation as one of the key urban energy-saving retrofit benchmark projects in Shanghai in 2013.

With one major retrofit under their belt, Shanghai Xijiao launched another project in 2017, this time focusing on their 25,000 square meter sports center, which contains a swimming pool, gym, bowling alley, and a children's playground. Given that the maglev oil-free chillers had been running smoothly and reliably, and delivering outstanding energy savings, Shanghai Xijiao decided to implement a similar oil-free solution for the air conditioning system renewal in the sports center. They expect to achieve similar the same high level of energy-efficiency in the coming years.

You can learn more about oil-free technology that drove Shanghai Xijiao’s results by visiting Oilfree.Danfoss.com