Relic protection requires high quality control of the temperature and relative humidity of the environment. Due to the large energy compensation caused by the fixed dew point on the cooling coil (CC) in the conventional constant temperature and humidity air-conditioning system

a decoupling method of temperature and humidity applying to the cooling coil is proposed

as well as the temperature and humidity control method for multi-zone. A new system employing a temperature and humidity independent control (THIC) device in the CC and a method of PID split-range control are developed. Experiments show that the temperature and relative humidity can be well controlled with a high precision. Now this system has been successfully applied to more than 10 relic protection projects of museums in Zhejiang province

with 30.7% energy-saving rate on average practically.