Specific Power Cut 28% and 31% on Two Air Systems at an Automotive Plant in Tianjin

The Tianjin plant of an automotive manufacturer runs two separate compressed air systems:

• a 6 bar low-pressure system for general production;
• a 12 bar high-pressure system for processes that need higher pressure.

Both had become expensive to run. The 6 bar system operated at a specific power of 0.143 kWh/m³ and the 12 bar system at 0.171 kWh/m³, well short of current efficiency levels. The compression heat from both systems was being wasted. The plant wanted to upgrade both systems without its own capital investment.

The plant chose an energy management contract. A specialist compressed-air service provider took responsibility for upgrading and operating the stations, and the benefits and risks of the energy savings are shared between the two parties.

The upgrade covered:

• High-efficiency SIND screw compressors for both pressure levels.
• A smart energy-management platform that monitors and optimises both systems continuously.
• A SIND heat-recovery system on the SIND compressors that captures compression heat and supplies it to the factory, including space heating.

The project passed independent testing and earned certification to the Grade-1 energy-efficiency standard.

After the upgrade, both systems were measured:

• 6 bar system: specific power reduced from 0.143 to 0.103 kWh/m³ (−28%).
• 12 bar system: specific power reduced from 0.171 to 0.118 kWh/m³ (−31%).
• More than 7 million kWh of electricity saved per year (expected).
• About 11,018 kWh of heat recovered per day, more than 4 million kWh per year, enough to cover the annual heating needs of about 2,000 employees.
• No capital investment for the plant under the energy-management model.

The project shows how an energy-management contract can upgrade both low- and high-pressure systems without capital investment, while turning waste heat into a useful energy source.