Learn about scientific and technological thermal insulation tips from "Erbin" ice storage method
◎Our reporter Du Peng
In the twelfth lunar month of winter, the Songhua River is covered with ice and snow, and it is completely white. Above the ice and snow, people and machines were shuttled back and forth.
Not long ago, when Harbin Ice and Snow World was still welcoming visitors from all over the world, the annual ice storage work had quietly begun.
Preserving ice is a task that Harbin Ice and Snow World must complete every year. In order to open the door as early as possible to welcome guests, Harbin Ice and Snow World usually starts construction in November every year. However, the Songhua River was not completely frozen at this time and ice could not be obtained directly. Therefore, ice storage in previous years has become the main construction material of Harbin Ice and Snow World.
The 25th Harbin Ice and Snow World, which will start construction at the end of 2023, will use the ice stored in the previous year. In order to allow these stored ices to survive the four seasons stably, the staff of Harbin Ice and Snow World have used many insulation technologies.
Cover the ice with a thick "quilt" to help you survive the summer
Every year after the construction of Harbin Ice and Snow World is completed, the ice storage work starts immediately. "At this time, the thickness of the ice on the Songhua River exceeds 60 centimeters, and relatively complete ice cubes can be selected for storage." Sun Zemin, deputy director of the Marketing Department of Harbin Ice and Snow World, said.
There is a huge amount of ice stored in Harbin Ice and Snow World. The space in indoor places such as cold storage is limited and the cost is high. Therefore, the stored ice is often piled directly on the outdoor open space. The collected ice is stored outdoors for a whole year, including during the hot summer months. This sounds weird, but the principle behind it is not complicated. Sun Zemin said that the most important thing to ensure that ice cubes do not melt outdoors is to "cover them" with a quilt.
The heat that can melt existing ice mainly comes from the surface and solar radiation. To block surface heat, staff will lay a layer of heat-insulating cloth on the ground before stacking ice cubes. In order to block the more "lethal" sunlight, the staff will cover the ice with a thick "quilt". On the one hand, this can avoid direct sunlight, and on the other hand, it can isolate the ice from the outside world, ensuring that external heat will not be transferred to the stored ice. This thick "quilt" is composed of insulating plastic cloth, black sunscreen net, rock wool board, straw mat and other insulation materials, with up to 9 layers.
Sun Zemin said that with this "quilt", even after a hot summer, more than 70% of the stored ice will still meet the usage standards when it is used in winter. When needed, staff will use mechanical vehicles to remove blocks of ice from the ice stack. Only ice cubes whose thickness, length, integrity and cleanliness meet the standards can be sent to the park for landscape construction.
After a year of storage, the volume of the ice has decreased, but it has become harder and more compact, making it a good material for ice carving craftsmen. For example, the bottom part of the "Crown of Ice and Snow", the iconic landscape of the 25th Harbin Ice and Snow World, is carved from existing ice, while the upper part is built with newly excavated ice to ensure the stability of the ice sculpture structure.
"Wearing a cotton-padded jacket" to control the temperature of the building
Not only does ice storage require a "quilt" for insulation, many buildings in daily life also adopt similar insulation measures. In order to reduce the energy consumption of buildings and reduce the energy required for cooling and heating, people began to "wear cotton jackets" on buildings to make their internal temperatures relatively constant.
The rock wool board used in the ice storage process of Harbin Ice and Snow World is one of the common thermal insulation materials and is widely used in building insulation.
Rock wool was first born in volcanic eruptions. After the volcano erupted, people discovered that the rock melted by the high temperature had a soft texture and looked like cotton. Subsequently, people simulated a volcanic eruption and melted basalt and other rocks at a high temperature of 1,450 degrees Celsius. Workers then turn the melt into fibers and add other materials to create rock wool panels commonly used in construction.
The main reason why rock wool can retain heat is that it can retain a large amount of air inside. Among many thermal insulation media, the thermal insulation effect of air is second to none, which can effectively reduce internal and external heat exchange.
Rock wool has a low density, a loose internal fiber structure, and a large number of tiny pores. These pores can lock the air and form a stable gas layer inside the rock wool, which effectively slows down the air flow and heat transfer speed, prevents heat exchange between the building and the external environment, and insulates the building. In addition, rock wool also has the characteristics of high ignition point and good fire resistance, and is a Class A fireproof material.
New materials are emerging one after another
With scientific progress and technological innovation, new materials that can be "put on and taken off" freely provide new options for building insulation.
Scientists from the School of Molecular Engineering at the University of Chicago have previously released a research result. Researchers have designed a building material that changes its color depending on the outside temperature. Different colors have different abilities to absorb heat radiation. For example, black has a stronger ability to absorb heat radiation, while white has a weaker ability to absorb heat radiation. When the weather is hot, this material can help cool the building by changing color, keeping the temperature inside the building relatively constant without consuming a lot of energy.
There are also aerogels that can insulate buildings.
Gel is a common substance, and the jelly that people usually eat is a typical gel. Aerogel is a nano-scale porous solid material formed by using drying technology to replace the liquid in the gel with gas. Aerogels have extremely low thermal conductivity compared to traditional insulation materials. Drop a few drops of water on an airgel plate with a thickness of only a few millimeters, and then use a high-temperature spray gun to heat the bottom of the plate. The bottom of the board had been burned red, but the water droplets showed no sign of boiling. The strong thermal insulation ability makes aerogel widely used in the aerospace field.
A new type of silica aerogel unveiled at the "Cambridge Energy Week", a high-end conference in the international energy industry, has the characteristics of super heat insulation, super lightness and fire resistance. Applying the gel to double glazing can increase a building's thermal insulation capacity by 50%.
Due to the outstanding thermal insulation properties of aerogel, many people have tried to apply it to clothing textiles in recent years.
In this regard, Song Lidan, an engineer at the China Textile Construction and Planning Institute, said that although airgel has good thermal insulation effect and broad application prospects, it also has shortcomings. Its biggest disadvantage is that it is brittle, has weak intermolecular forces, is easily powdered, and lacks the flexibility and drape required for clothing. It is not suitable for direct use in daily textiles and clothing.
"Consumers are advised to purchase relevant products rationally and not blindly believe in advertising." Song Lidan added. (Science and Technology Daily)