Passive solar houses rely entirely on solar heating and do not require other auxiliary energy sources. Active solar rooms use water pumps or fans to send water or air heated by solar energy into the room to achieve heating purposes.
Solar Thermal Utilization Technology
(1) Solar Building
i. Passive Solar House
One of the application forms of solar heating It is a passive solar room, that is, a heating system that relies on the building envelope itself to complete the functions of heat absorption, heat storage, and heat release. The outer envelope of a passive solar room should have a large thermal resistance, and there should be enough thermally heavy materials in the room, such as masonry, concrete or phase change energy storage materials, to maintain sufficient thermal storage performance of the house. In winter, a passive solar room absorbs and stores solar energy through the building envelope during the day, and releases and stores heat at night to meet indoor needs. Passive solar room technology can reduce the heating load in winter and even meet the requirements of the indoor environment without the need for other auxiliary heating methods.
my country began to develop passive solar houses in the 1970s, and entered the promotion and application stage in the 1990s. In 2002, the construction area was estimated to reach more than 10 million square meters. However, the proportion of building area that uses solar heating is still very small, and this technology still needs further development, application and promotion.
According to the different ways of collecting solar energy in the room, passive solar rooms can be divided into the following categories:
① Direct benefit type. In winter, the sunlight passes through the larger area of ??south-facing glass windows and directly shines on the indoor floors, walls and furniture with large heat storage capacity. These materials absorb and store most of the solar energy during the day and gradually release it at night, making the room A certain temperature can still be maintained at night. Due to the large area of ??south-facing windows, this type of sun room should be equipped with thermal insulation curtains and have good thermal insulation and sealing properties to reduce heat loss. Windows should also be equipped with sunshades to block summer sunlight from entering the room.
②Heat collecting and storage wall type. This form of passive solar room is composed of a translucent glass cover and a heat storage wall, with an air layer in the middle, and air vents leading to the room on the upper and lower parts of the wall. During the day, the south-facing heat-collecting and heat-storage wall is used to absorb sunlight passing through the glass cover. The wall will absorb and transmit a certain amount of heat. At the same time, the air in the interlayer is heated and becomes hot air and enters the room through the air vents; at night, the heat-collecting and heat-storage wall Body heat will gradually transfer into the room. The outer surface of the thermal storage wall is painted black or some dark color to effectively absorb sunlight. To prevent heat loss at night, thermal insulation curtains and insulation panels should be installed on the outside of the glass. Heat collection and storage walls can be divided into solid heat collection and storage walls, pattern heat collection and storage walls, water wall heat collection and storage walls, phase change material heat collection and storage walls, and rapid heat collection walls.
③Additional sunroom style. The sun room is attached to the south side of the main house. Its enclosure structure is entirely or partially made of glass and other light-transmitting materials, and the ground is made into a heat storage body. It is heated by solar radiation during the day, and its internal temperature is always higher than the external ambient temperature. The heat is transmitted into the main room through the doors and windows on the wall of the apartment adjacent to the main room. The sunroom can not only supply heat to the main room during the day, but also serve as a buffer zone at night to reduce room heat loss.
④Thermal storage roof pool type. The rooftop pool-type solar room has both winter heating and summer cooling functions, and is suitable for areas that are not too cold in winter and hot in summer. This passive solar house places a sealed plastic bag filled with water as a heat storage body on the roof ceiling, and sets a thermal insulation cover on it that can be opened and closed horizontally. When it is sunny during the day in winter, the insulation cover is opened to allow the water bag to fully absorb and store solar radiation heat, and part of the heat is transferred to the room below through radiation and convection. At night, the insulation board is closed to prevent heat loss to the outside. The opening and closing of the thermal insulation cover in summer is opposite to that in winter. The thermal insulation cover is closed during the day to reduce the heat transfer to the indoor environment. At the same time, a lower temperature water bag is used to absorb the heat in the room below, thereby reducing the indoor temperature; it is opened at night. The thermal insulation cover allows the water bag to release heat to the outside environment.
⑤ Convection ring type. This form of passive solar room uses a south-facing collector to collect heat, and then transfers the heat to a heat storage body set under the floor. The heat from the heat storage body is transferred into the room through the floor.
ii. Active solar room
a. Active solar heating system
Usually solar collectors are used as the heat source of active solar heating systems. Solar thermal heating systems can use air or water as the heating medium. Therefore, there are solar hot air collecting heating systems and solar hot water collecting heating systems.
Solar hot air collectors can be used as heat sources for heating systems. A solar air collector is arranged on the roof facing south, and the heated air is sent into the room by a fan after passing through the heat storage layer. The solar collector can also be equipped with other auxiliary heat sources, and a control and adjustment device can be set to determine the input ratio of the auxiliary heat source according to the supply air temperature.
②Solar hot water collector heating system
Solar hot water collectors can not only provide sanitary hot water, but can also be used as a heat source for low-temperature hot water floor radiant heating.
③ Solar hot water collector floor radiant heating and domestic hot water supply system. The system is equipped with a solar water heater on the roof. The system includes a collector circulating water pump, a hot water storage tank, a hot water supply tank, a heating circulating water pump, an auxiliary heat source, an auxiliary heat source hot water circulating pump, an auxiliary heating heat exchanger and a floor radiant heating coil. wait. The hot water in the solar water heater flows through the floor heating coil to provide heat to the room. After returning to the hot water storage tank, the hot water is sent to the solar collector for reheating by a heat collecting circulating water pump. When the solar energy is insufficient at night or on cloudy days, the auxiliary heat source heating system is used. Ensure indoor heating and domestic hot water needs.
Solar hot water collectors can also be integrated with the building envelope, such as the solar all-glass vacuum collector curtain wall domestic hot water system in the project.
b. Solar refrigeration system
According to different working principles, solar refrigeration technology can be divided into various forms such as solar absorption refrigeration, solar adsorption refrigeration and solar injection refrigeration. Compared with solar absorption refrigeration systems, the technology and performance of solar adsorption refrigeration systems and solar jet refrigeration systems are less mature.
The principle of the solar absorption refrigeration system is the same as that of the lithium bromide absorption refrigerator. The difference is that the heat source of the lithium bromide concentrated solution generator in the solar absorption refrigeration system is hot water or steam generated by the solar collector. supply. The Guangzhou Institute of Energy Research of the Chinese Academy of Sciences is conducting research on large-scale solar absorption refrigeration systems. This project is a key scientific and technological research project of the National Science and Technology Commission’s “Ninth Five-Year Plan”. The institute used two patented technologies, "two-stage absorption lithium bromide refrigerator" and "high-efficiency flat plate collector", to build the country's first practical solar absorption refrigeration system in Jiangmen City, Guangdong Province. The main technical parameters are: the solar collector area is 500m2, and the daily domestic hot water supply is 30m3/h; the refrigerator is a two-stage absorption lithium bromide refrigerator with a cooling capacity of 100kW, and the air conditioning area is 600m2; a fuel-fired water heater is used as an auxiliary heat source.