I. The Challenge of Cultural Heritage Preservation: Why Constant Temperature and Humidity Units Have Become “Energy Guzzlers”

In the quiet exhibition halls and storage rooms of museums, constant temperature and humidity units serve as the “life support systems” for cultural relics, regulating environmental parameters 24 hours a day without interruption. However, behind this meticulous protection lies a steadily rising energy bill. Constant temperature and humidity units typically account for 30% to 40% of a museum’s total energy consumption, and in some older facilities, this figure is even higher.

Against the backdrop of the national “Dual Carbon” strategy, how museums can achieve energy conservation and reduce consumption without compromising cultural heritage preservation standards has become a critical issue that urgently needs to be addressed in the cultural heritage sector.

II. The “Gold Standard” for Temperature and Humidity in Cultural Heritage Preservation

Before discussing energy-saving renovations, it is essential to clarify the strict environmental requirements for cultural relics. According to cultural relic preservation standards, artifacts made of different materials have strict and varying requirements for temperature and humidity. For organic cultural relics, such as calligraphy, paintings, and textiles, the general storage environment requirements are a temperature of 14–20°C and a relative humidity of 50%–60%. Daily temperature fluctuations should not exceed 2–5°C, and daily relative humidity fluctuations should not exceed 5%. In practical applications, many museums set their temperature and humidity control targets for display cases at 20±2°C and 50±5% RH. Some venues with stricter requirements even raise the control precision to ±1°C for temperature and ±5% RH for humidity. Storage facilities for metal artifacts require a drier environment, with relative humidity typically maintained between 45% and 50%; where conditions permit, it can even be lowered to 35%.

III. Four Major Technical Approaches to Energy-Efficient Retrofits

Path 1: Variable Frequency Drive Technology—Saying Goodbye to “Overkill”

Traditional fixed-frequency constant temperature and humidity units are like “stubborn old men”—they only know how to run at full power. When humidity exceeds the limit, the compressor immediately runs at full load; once the target is met, it shuts down abruptly, causing the environmental curve to resemble a roller coaster and keeping energy consumption high. The introduction of variable frequency technology has fundamentally changed this situation.

Variable-frequency compressors enable stepless capacity adjustment from 10% to 100%, allowing them to linearly adjust operating frequency based on actual load, thereby avoiding frequent start-stops and over-supply. In terms of energy savings, variable-frequency compressors are over 30% more energy-efficient than fixed-frequency models. In systems utilizing advanced variable-frequency technology, energy consumption during partial-load operation can be reduced by 30% to 50% compared to fixed-frequency models.

Path 2: Heat Recovery Technology—Turning “Waste” into Treasure

The substantial amount of condensation heat generated by constant temperature and humidity units during the cooling and dehumidification process is often directly discharged into the atmosphere in traditional systems, resulting in a waste of energy. Heat recovery technology captures and reuses this “waste heat” for air reheating or preheating fresh air.

From a technical perspective, there are two primary approaches to heat recovery. Condensate heat recovery is the most direct method: it utilizes the waste heat generated by the refrigeration system as a heat source for heating and reheating the air conditioning unit, replacing traditional electric heating. This not only saves energy but also eliminates the safety risks associated with electric heating. Designs based on dual condensers take this a step further. Through the intelligent switching of two solenoid valves, they flexibly transition between cooling and heat recovery modes, fully utilizing condensation heat as a heating source.

Path 3: Improving the Airtightness of Envelope Structures — Sealing “Hidden Leaks”

While the first two approaches focus on optimizing the equipment itself, retrofitting the building envelope fundamentally reduces environmental impact. No matter how efficient a constant temperature and humidity unit may be, if the storage room or display cabinet lacks sufficient airtightness and humid, warm air from outside continues to seep in, the unit will be forced to operate at full capacity for extended periods to compensate for the loss.

For display cabinets, improving sealing is the most direct approach. Replacing aged silicone gaskets and optimizing door structures can significantly reduce external environmental interference with internal temperature and humidity, reducing unit operating time by 25%. At the storage facility level, the renovation project at the Battle of Pingjin Memorial Hall provides a prime example: constructing a highly airtight building envelope using a “room-within-a-room” design, employing 75mm-thick Class B1 fire-rated polyurethane insulation panels, and sealing all air leaks. Each renovated room covers approximately 50 square meters, with an internal height of no less than 2.8 meters.

V. Conclusion: The Dialectical Unity of Energy Conservation and Cultural Heritage Preservation

The energy-saving retrofit of constant temperature and humidity units is by no means a “trade-off” achieved at the expense of cultural heritage preservation quality, but rather an efficient balance point found through technological innovation. Variable frequency technology prevents the system from providing unnecessary excess energy; heat recovery technology transforms “waste heat” into a valuable resource; intelligent control algorithms enable precise scheduling; and improved airtightness of the building envelope reduces environmental loads at the source. Through the synergistic efforts of these four elements, reducing annual energy consumption by more than 30%—while strictly maintaining the “lifeline” of cultural heritage preservation at a temperature of 20±2°C and humidity of 50±5% RH—has become a fully achievable goal.