Thread Content
A Brief Discussion on Building Energy-Saving Technologies Source: China Environmental Protection Network. Building energy consumption refers to the energy used in buildings, including that for heating, air conditioning, hot water supply, cooking, and household appliances. Among these, energy consumption for building heating and air conditioning accounts for the largest share, comprising 50% to 70% of the total energy consumption in buildings. With the rapid development of China’s economy and the continuous improvement of people’s living standards, building energy consumption in China is increasing steadily. In 1999, building energy consumption in China accounted for 20% to 25% of the country’s total energy consumption. In the West**, building energy consumption typically accounts for 30% to 40% of the country’s total energy consumption. Therefore, as people’s living standards continue to rise, urbanization accelerates, and housing system reforms deepen, building energy consumption in China is bound to increase further. Building energy consumption in our country has significant room for growth, and it will represent a major source of increase in energy consumption in the future. In 1999, the total energy consumption in the United States accounted for about 26% of the world’s total energy consumption, with energy used in buildings alone being close to China’s total energy consumption. Since China’s population is about 4.5 times that of the United States, if China’s per capita building energy consumption reached the current level in the U.S., then China’s building energy consumption would account for 40% of the world’s total energy consumption today. This situation is unimaginable. As China’s economy continues to grow and people’s demands for comfort in indoor building environments increase, what should be done regarding energy efficiency in buildings in China? However, energy conservation in buildings must not come at the expense of people’s comfort and health; otherwise, energy conservation loses its meaning. So-called building energy efficiency refers to improving the efficiency of energy use in buildings, so as to achieve the greatest economic and social benefits with limited resources and at the lowest possible energy consumption cost. Therefore, energy conservation in construction is an important measure for implementing the sustainable development strategy, achieving **energy-saving planning goals, and reducing greenhouse gas emissions, and it is in line with global development trends. There are only two ways to address this issue: on the one hand, reducing the demand for energy consumption in buildings by utilizing renewable energy sources and energy-efficient building materials ； On the other hand, it is necessary to improve the efficiency of energy-consuming systems in order to reduce end-use energy consumption. I. Technical approaches and trends for achieving energy efficiency in buildings Rough estimates suggest that the adoption of thorough and effective building-related technical measures can reduce building energy consumption by 2/3 to 3/4. Therefore, during the planning, design, construction, and use of buildings, adopting reasonable and effective building energy-saving technologies while ensuring a comfortable, hygienic, and healthy indoor environment helps to achieve the goal of advancing both building energy efficiency and environmental protection. Japan’s recent proposal of the concept of “energy-efficient and environmentally sustainable design in architecture” is an embodiment of this idea. Generally speaking, the technical approaches to achieving energy efficiency in buildings involve minimizing the overall energy demand within buildings, while simultaneously making extensive use of renewable energy sources, thereby reducing the use of energy sources that can cause environmental pollution in building applications. (1) Reducing the total energy demand in buildings According to statistics, in developed countries, energy consumption for air conditioning and heating accounts for 65% of the total energy consumption in buildings. At present, the growth rate of energy used for heating, air conditioning, and lighting in our country is significantly higher than the growth rate of energy production. Therefore, reducing the energy consumption for cooling, heating, and lighting in buildings is an important aspect of lowering the overall energy consumption of buildings, and this can generally be achieved through the following approaches. 1. Building Planning and Design In the face of global energy and environmental challenges, many new design concepts have emerged, such as low-energy buildings, zero-energy buildings, and green buildings. Essentially, these concepts require architects to adopt a comprehensive design approach and to work closely with energy analysis experts, environmental specialists, mechanical engineers, and structural engineers. In building planning and design, taking into account the influence of broader climate conditions as well as the specific environmental and climatic features of the location where the building is situated, emphasis is placed on making use of the natural environment – such as external air currents, rainwater, lakes and green spaces, as well as the terrain – to create a favorable indoor microclimate for the building, thereby reducing reliance on building systems. The specific measures can be summarized into the following three aspects: selecting an appropriate location for the building, and implementing a proper external environment design (the main methods include planting trees, vegetation, water features, rock formations, and fences around the building) ； Reasonably design the building form (including determining the overall volume of the building and its orientation) to improve the existing microclimate ； A rational architectural form design is a key element in making full use of the building’s outdoor microenvironment to improve its indoor microenvironment, and it is achieved primarily through the structural design of various building components as well as the rational division of interior spaces. At the same time, optimization design can be carried out with the help of relevant software; for example, the building shadow simulation in Tianzheng Architecture (II) can be used to assist in determining the orientation of buildings, as well as the layout of roads, green spaces, and outdoor recreational areas within residential complexes. CFD software such as PHOENICS and Fluent can also be utilized to analyze whether air flow inside and outside the buildings is smooth. 2. Envelope The design of the components that make up a building’s envelope (roof, walls, foundation, insulation materials, sealing materials, doors and windows, shading devices) has a fundamental impact on the building’s energy consumption, environmental performance, indoor air quality, as well as the visual and thermal comfort of those inside the building. Generally, the cost of enhancing the enclosure structure amounts to only 3%–6% of the total investment, while energy savings can reach 20%–40%. By improving the thermal performance of the building’s envelope, heat from the outside can be reduced from entering the building in summer, and heat loss from inside the building can be reduced in winter. This improves the thermal environment of the building, thereby reducing its energy consumption for heating and cooling. Firstly, improving the thermal performance of the various components of the building envelope is generally achieved by altering the thermal properties of the materials used in these components. Examples include the heat diode walls developed in the EU (low-cost thin heat diodes that allow heat transfer in only one direction, thereby providing insulation), as well as glass whose thermal properties change dynamically throughout the seasons. Then, based on the local climate, the geographical location and orientation of the building, and guided by the calculation results from the building energy consumption software DOE-2.0, an optimized design method for the envelope combination is selected. Finally, evaluate the technical and economic feasibility of various components and combinations of the enclosure structure to determine a technically feasible and economically reasonable one. 3. Improve the energy efficiency of end-users. High-efficiency heating and air-conditioning systems, used in conjunction with the measures mentioned above to reduce indoor heat and cold loads, are necessary to truly cut down energy consumption for heating and air conditioning. First, based on the characteristics and functions of the building, design high-energy-efficiency HVAC systems, such as heat pump systems, energy storage systems, and district heating and cooling systems. Then, an energy management and monitoring system is used in operation to supervise and regulate indoor comfort, indoor air quality, and energy consumption. In Europe, for example, sensors are used to measure the temperature, humidity, and sunlight intensity of the surrounding environment; based on a dynamic building model, heating and cooling loads are predicted, thereby controlling the operation of the HVAC system. For other home appliances and office equipment, it is advisable to use products with energy-saving certifications. Like the United States, which encourages the use of Energy Star-rated products, Australia imposes minimum energy efficiency standards (MEPS) on energy-intensive home appliances. 4. Improve overall energy efficiency Significant energy losses occur during the conversion of primary energy into the final energy form used by building equipment systems. Therefore, an evaluation should be conducted across the entire process (including extraction, processing, transportation, storage, distribution, and end-use) in order to comprehensively reflect energy utilization efficiency and the environmental impact of energy. Energy-consuming devices in buildings, such as air conditioners, water heaters, and washing machines, should use energy-supply sources with high efficiency. For example, as a fuel, natural gas has a higher overall energy efficiency than electricity. By adopting second-generation energy systems, heat energy of different grades can be fully utilized to maximize energy efficiency, such as combined heat and power (CHP) and combined cooling, heat and power (CCHP). (II) Utilization of new energy In terms of energy conservation and environmental protection, the use of new energy plays a crucial role. New energy generally refers to unconventional renewable energy sources, including solar energy, geothermal energy, wind energy, biomass energy, and so on. Extensive research has been conducted on various ways of utilizing solar energy, and the direction for its development has gradually become clear, allowing solar energy to be put to use to some extent. For example: 1. As an important aspect of solar energy utilization, solar thermal power generation technology is relatively mature; countries such as the United States, Israel, and Australia have invested in building a number of experimental solar thermal power plants, with commercialization of this technology expected in the future ； 2. With the development of solar photovoltaic power generation, many photovoltaic power plants and \"solar roof\" demonstration projects have been built abroad, which will drive the rapid development of grid-connected power generation systems ； 3. Currently, tens of thousands of photovoltaic water pumps are in operation around the world ； 4. Solar water heater technology is relatively mature, with corresponding technical standards and specifications in place; however, it is still necessary to further improve the functions of solar water heaters and enhance the integration of solar energy in building design ； 5. Passive solar buildings have been widely used due to their simple structure and low cost; their design techniques are relatively mature, and there are design manuals available for reference ； 6. Solar absorption refrigeration technology was developed early on, and it is now used in the field of large-scale air conditioning systems ； Solar adsorption refrigeration is currently in the stage of prototype development and experimental research ； 7. Solar drying and solar cookers have been somewhat widely adopted. Overall, however, the current scale of solar energy utilization is still small, the technology is not yet mature, and its level of commercialization is low; further in-depth and extensive research is still needed. When utilizing geothermal energy, it can be used on one hand to generate electricity from high-temperature geothermal heat, or directly for heating and hot water supply ； On the other hand, low-temperature geothermal energy can be utilized through ground-source heat pumps and underground air systems. Wind power generation is more suitable for windy coastal mountainous areas and high-rise buildings prone to strong winds; there are successful projects in the UK and **, but in the building sector, the more common form of wind energy utilization is natural ventilation. II. New Technologies for Building Energy Efficiency An ideal energy-efficient building should meet the following three requirements with minimal energy consumption: first, it should be able to control the absorption or prevention of solar radiation in different seasons and regions ； Second, it is able to maintain indoor comfort throughout different seasons ； Third, it enables necessary ventilation in indoor spaces. Currently, the main approaches to energy conservation in buildings include: minimizing the consumption of non-renewable energy sources and improving the efficiency of energy use ； Reduce energy loss in building envelopes ； Reduce the energy consumption associated with the operation of building facilities. In these three areas, high-tech plays a decisive role. Of course, some traditional techniques are also used for building energy conservation, but these techniques can only be applied in modern buildings based on advanced experimental validation and scientific theoretical analysis. (1) Reducing energy consumption and improving energy efficiency To maintain the environmental quality of living spaces, heating is required in cold seasons to raise indoor temperatures, while cooling is needed in hot seasons to lower them. Humidification is necessary in dry conditions, and dehumidification is required in humid conditions; all of these actions typically require energy to be carried out. From an energy-saving perspective, it is necessary to improve the efficiency of heating (cooling) systems, which includes the efficiency of the equipment itself, the efficiency of heat transfer through piping networks, metering at the user end, and the efficiency of control devices for the indoor environment. All of these require the relevant industries to employ advanced technologies in aspects such as design, installation, operational quality, energy-saving system control, equipment materials, and business management models. Currently, there are three new technologies for energy savings in heating systems: ① Using computers, balance valves, and specialized intelligent instruments to allocate flow rates in the piping network appropriately, which improves the quality of heating while also saving energy ； ②Heat distribution tables and temperature control valves are installed on the user’s radiator, allowing them to consume and control thermal energy as needed, thereby achieving both comfort and energy savings ； ③New insulation materials are used to wrap the heating pipes in order to reduce heat loss from them. In recent years, low-temperature floor radiant heating technology has proven to be quite energy-efficient. It uses cross-linked polyethylene (PEX) pipes as the water conduits, which are arranged in a bidirectional circulation pattern within the floor layer; in winter, low-temperature hot water is supplied to these pipes (provided by geothermal energy, solar energy, or various sources of low-temperature waste heat) ； In summer, introducing cold water can lower the surface temperature (currently it is only used for heating in China) ； Compared with radiators that rely primarily on convective heat dissipation, this technology offers advantages such as a more even indoor temperature distribution, improved comfort, energy savings, easier measurement, and simpler maintenance. (II) Reducing energy loss in building envelopes The energy loss in a building’s envelope comes mainly from three sources: ① exterior walls ； ②Doors and windows ； ③Roof. Energy-saving technologies in these three areas are of great interest to the construction industry around the world. The main development direction is to develop efficient and cost-effective insulation and heat-insulating materials, as well as practical construction techniques, in order to improve the insulation, heat-insulation performance, and airtightness of building envelopes. 1. External wall energy-saving technologies When it comes to energy efficiency in walls, the traditional approach of using heavy, single materials to increase wall thickness in order to achieve insulation is no longer sufficient to meet the requirements of energy conservation and environmental protection; as a result, composite walls are increasingly becoming the standard choice for walls. Composite walls generally use block materials or reinforced concrete as the load-bearing structure, combined with insulation materials; or in frame structures, thin-walled materials are used along with insulation materials to form the wall. Currently, the main insulation and heat-insulating materials used in construction include rock wool, slag wool, glass wool, polystyrene foam, expanded perlite, expanded vermiculite, aerated concrete, and polymer-modified polystyrene particle slurry. The production and manufacturing of these materials require special processes and equipment, beyond what traditional techniques can achieve. It is worth mentioning the rubber powder polystyrene particle slurry, which is created by mixing rubber powder material, polystyrene particle lightweight aggregates with water to form a slurry that is then applied to the outer surface of walls to create a cavity-free insulation layer. Polystyrene particle aggregate is made by crushing recycled waste polystyrene boards, while the cement paste mixture contains a large amount of fly ash; it is a material that makes use of waste and contributes to energy conservation and environmental protection. There are three types of composite wall technologies: internal insulation, external insulation, and sandwich insulation. Our country makes extensive use of the sandwich insulation method ； In European countries, the use of external foam polystyrene boards is common; in Germany, buildings with external insulation account for 80% of all buildings, and 70% of these use foam polystyrene boards. 2. Energy-saving technologies for doors and windows Doors and windows serve to provide light and ventilation, as well as to act as a barrier; they also play an important role in the artistic aspect of building design. However, doors and windows are the parts most prone to energy loss. To increase the area for natural light and ventilation or to reflect the characteristic features of modern architecture, the size of doors and windows in buildings is becoming larger and larger, with some buildings even featuring entirely glass curtain walls. This places higher demands on energy efficiency in external structural systems. Currently, energy-saving measures for doors and windows mainly involve improving the thermal insulation properties of the materials and enhancing the airtightness of the doors and windows. In terms of door and window materials, in recent years energy-saving products with higher technical content have emerged, such as aluminum alloy insulated profiles, aluminum-wood composite profiles, steel-plastic integrally extruded profiles, wood-plastic composite profiles, and UPVC plastic profiles. The most widely used among them is UPVC plastic profiles, whose raw material is a polymer material – rigid polyvinyl chloride. It not only has low energy consumption and is pollution-free during production, but also features a material with a low thermal conductivity and a multi-chamber structure with good sealing properties, thus offering excellent heat insulation performance. UPVC plastic doors and windows have been in use in European countries for many years; in Germany, they account for 50% of all doors and windows. Since the 1990s, the use of plastic doors and windows in our country has been increasing steadily, and they are gradually replacing materials with high energy consumption such as steel and aluminum alloys. To address the issue of excessive energy loss caused by large areas of glass, advanced technologies have been employed to transform ordinary glass into insulating glass, coated glass (including reflective and heat-absorbing glass), high-strength LOW-E fire-resistant glass (high-strength low-emissivity coated fire-resistant glass), glass with a metal silver layer deposited using magnetron vacuum sputtering, and, most notably, smart glass. Smart glass is capable of detecting changes in external light and responding to them. There are two types of such glass: photochromic glass, which darkens when exposed to light, making it difficult for light to pass through ； When the light exposure is stopped, the glass becomes transparent again, and light can pass through. It can block solar radiant heat when the sunlight is intense ； When it’s overcast, the glass becomes brighter, allowing sunlight to enter the room again. Another type is electrochromic glass, in which conductive films and color-changing substances are coated on two layers of glass; by adjusting the voltage, the color-changing substances can be made to change color, thereby regulating the amount of sunlight that passes through (however, due to their high production costs, they are not yet available for practical use). These glasses offer excellent energy-saving effects. 3. Roof energy-saving technologies Insulation and heat resistance of roofs are among the key aspects of energy savings in building envelopes. In cold regions, insulation is installed on roofs to prevent heat from escaping indoors ； In hot regions, insulating layers are installed on rooftops to prevent the radiant heat from the sun from reaching the interior ； In areas with cold winters and hot summers (the Yellow River to Yangtze River basins), building energy efficiency needs to take into account both winter and summer conditions. A common technical measure for insulation is to use lightweight materials with a low thermal conductivity under the roof waterproofing layer as insulating material, such as expanded perlite and glass wool (this is the direct application method) ； Polystyrene foam can also be installed above the roof waterproofing layer (this is the reverse installation method). In the UK, another method of insulation involves using paper fibers made from recycled waste paper. The production of these paper fibers requires very little energy, and they offer excellent insulating properties; moreover, they are treated with borax to make them fire-resistant as well. During construction, the nail layer interlayer is first placed on the roof, and then paper fibers are blown in to form an insulating layer. Methods for insulating and cooling rooftops include: elevated ventilation, roof water storage or timed irrigation, and roof greening. All of the above approaches can meet the requirements for roof energy efficiency to varying degrees, but what is currently most highly regarded is the use of intelligent and ecological technologies to achieve energy savings in buildings, such as solar thermal roofs and controllable ventilation roofs. (III) Reducing energy consumption in the operation of building facilities Heating, cooling, and lighting account for the largest portion of energy consumption in buildings; reducing energy use in these areas plays a crucial role in saving energy. There are several successful technical solutions in this regard that can serve as useful examples, such as the energy-efficient office buildings developed by the Building Research Establishment (BRE). The office building features advanced energy-saving control systems for its building envelope, and it has open mezzanines inside to facilitate natural ventilation ； Air enters through the lattice windows on the back of the building, while air is expelled through the lattice windows on the top wall at the front of the building, thereby creating natural ventilation throughout the structure. The office building uses high-efficiency heat and cold boilers as well as conventional boilers, with these two types of boilers being switched back and forth under the control of a computer system. The room temperature is regulated through heating and cooling pipe systems embedded in the floor. The building also utilizes a system in which cold water is supplied beneath the floor and used to cool the radiators; cold water is pumped from deep wells beneath the garage into the radiators, and then returned to the surface through another return well located next to the building. To reduce artificial lighting, office buildings employ a comprehensive combination of lighting and daylighting systems that are controlled by a building management system ； Each unit has natural light, and users and managers can remotely control the system via detectors ； In the 100-seat lecture hall, there are two types of lighting systems that allow for brightness levels ranging from 0% to 100%. Energy-efficient tubular fluorescent lamps and incandescent lamps are used to ensure that every audience member enjoys the same excellent visual quality as well as a comfortable temperature. (IV) Development and utilization of new energy While striving to conserve non-renewable energy sources, humanity is also seeking to develop and utilize new energy sources in order to cope with the challenges posed by population growth and energy depletion. This is a mission entrusted to modern people by history, and the effective development and utilization of new energy necessarily relies on high technology. To utilize sources of energy such as solar, wind, tidal, hydro, geothermal, and other renewable natural energies, advanced technical methods are necessary, and these methods must be continuously improved to enable more efficient use of such energies. In buildings, not only can solar energy be used for heating, but solar water heaters can also convert solar energy into electrical energy. Moreover, photovoltaic products can be integrated with building components such as photovoltaic roof panels, photovoltaic exterior wall panels, photovoltaic shading panels, photovoltaic partition walls, photovoltaic skylights, and photovoltaic glass facades, thereby turning energy consumption into energy production. III. Development of New Materials for Building Energy Efficiency (A) External Wall Insulation and Finish Systems (EIFS) This system emerged during the last energy crisis at the end of the 1970s; it was first used in commercial buildings, and later applied in residential buildings as well. Today, EIFS systems account for 17.0% of exterior walls in commercial buildings and 3.5% in residential buildings, with their use in residential buildings growing at a rate of 17.0% to 18.0% per year. This system is a multi-layer composite exterior wall insulation system that can be used in both residential and commercial buildings. The ELFS system consists of the following components: the main component is a thermal insulation panel made of polystyrene foam, typically 30 to 120 mm thick; this panel is fixed to the exterior wall of the building using synthetic adhesives or mechanical means ； The middle layer is a durable, waterproof polymer mortar base layer, which is primarily used on insulation panels and reinforced with glass fiber mesh to distribute external forces ； The outermost part is a beautiful and durable surface coating. To prevent fading and cracking, coating materials typically use acrylic copolymer coating technology; such coatings are available in a variety of colors and textures, and they offer excellent durability and corrosion resistance. (II) Building Insulation Panel System (SIPS) This material can be used in residential and commercial buildings, and it is a high-performance material for walls, floors, and roofs. The middle of the panel consists of a polystyrene foam or polyurethane foam core, typically 120–240 mm thick; the two surfaces can be fitted with different types of solid surface layers as required. For example, in building construction, engineered plywood or other wooden products can be used on both surfaces. Buildings constructed with this material feature high strength, good thermal insulation, low cost, simple construction, energy savings, and environmental protection. SIPS is generally 1.2 meters wide and can reach up to 8 meters in length; its dimensions are standardized. Many factories can also customize it to specific sizes according to project requirements, providing it as a complete set. Contractors only need to assemble it on-site, thus truly realizing the industrialization of housing production. (III) Insulated Concrete Forming System (ICFS) This is an insulating form system in which the forms are made primarily from recycled polystyrene foam plastic and cement-based binders, and it is used for casting concrete walls or foundations on site. During construction, reinforcement is arranged horizontally or vertically inside the formwork; once the wall is completed, this insulated formwork becomes part of the permanent wall, resulting in a concrete wall that provides insulation both on the outside and inside of the wall. The formwork material used on the exterior of the concrete walls meets the requirements for insulation, sound insulation, fire resistance, etc., that are necessary for building exteriors. IV. Conclusion At present, energy waste in building use in our country is extremely severe, and the rate of increase in building energy consumption far exceeds the potential rate of growth in our country’s energy production. If such energy-intensive buildings continue to develop, it will be impossible for energy production to sustain such wasteful demands in the long term; as a result, large-scale energy-saving renovations of existing buildings will become necessary, which will require additional human and material resources. By actively improving energy efficiency in construction, it is possible to **alleviate** the energy shortage and promote the development of China’s national economic construction. Building energy conservation is a comprehensive, multi-faceted systematic project. Building energy conservation technologies encompass building technology, material technology, energy technology, intelligent technology, bionic technology, waste recycling technology, etc., as well as various aspects such as design, construction, management, and policies and regulations; it is indeed a comprehensive and integrated systematic effort. To achieve effective building energy conservation, it is far from sufficient to rely solely on architects; other industries must also develop energy-efficient products with high technical standards, such as energy-saving elevators, energy-saving air conditioners, and energy-saving lighting fixtures. Additionally, new energy utilization technologies need to be developed to enable buildings to gradually achieve low or even zero energy consumption.