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Analysis of Three Types of Sunpower Solar Heating Systems

Views:1     Author:Site Editor     Publish Time: 2019-06-19      Origin:Site

A healthy and comfortable living environment is inseparable from various electromechanical equipment technologies. It is these innovative air-conditioning technologies that provide us with a comfortable environment with comfortable temperature, reasonable air and healthy air.

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A. Solar floor heating

The sun is a huge hot sphere with a temperature of several thousand degrees in the central region and an average surface temperature of about 6000K. It radiates energy into the space in the form of electromagnetic waves. China's land surface receives solar radiant energy equivalent to 4.9 billion tons of standard coal per year, which is equivalent to the sum of the power generation of tens of thousands of Three Gorges projects. Due to the characteristics of the sun itself and its spatial relationship with the Earth, the intensity of the radiation on the vertical plane of the Earth's atmosphere and the sun's rays is a fixed value, but due to the rotation and revolution of the Earth and the plane of the Earth's axis and the orbital plane‘s fixed inclination is 23°27', so the earth's surface appears alternate day and night, season change and rain and snow, making the amount of solar energy at a certain point a variable and intermittent value. However, two-thirds of the country's land area is more than 2,200 hours of sunshine per year, and the annual solar radiation exceeds 5,000 MJ.


We advocate the best use of solar floor heating systems for heating. At present, the production and holding capacity of solar water heaters in China ranks first in the world, and its solar vacuum heat collecting tube technology has reached the world advanced level, but the cost is relatively low. Using solar energy to heat water to six or seventy degrees, its efficiency is very high, while the floor heating, water temperature at 40 or 50 degrees can reach the comfort level people need. For ordinary residential homes, floor heating saves about 20% of energy compared to convection heating. In addition, the floor heating has the following advantages: the vertical temperature field distribution is relatively uniform; under the same conditions of room temperature, the temperature from 0.05 to 0.15 m above the ground is about 8 to 10 ° C higher than the convection heating method, which is beneficial to human physiology (ie Compared with the convection heating method, the air convection is weakened, and the air cleanliness is better: the room thermal inertia is better; the average radiation temperature is appropriate, which can reduce the radiation dissipation of the human body; the heat source selection is broad and flexible, and It can be applied in places with hot water above 40 °C; it is conducive to building decoration, does not occupy the use area; it is conducive to the implementation of household heat metering; reducing floor noise; long service life and less maintenance.


We assume that the water is heated from 20 ° C to 50 ° C in December, then:

Total calories per square meter per day: 1764,000 cards = 1764 kcal;

The heat required to heat each kilogram of water from 20 ° C to 50 ° C:

(50-20) °C × 1000 card / ° C = 30000 card = 30 (kcal)

The amount of hot water that can be generated per square meter of heat collecting tube per day is (temperature difference is 30 ° C):

1764÷30=58.8kg


Therefore, as long as the rational use and proper design, the amount of solar energy can fully meet the daily heating needs. According to our empirical data, the ratio of solar heat collection area to floor heating area can reach about 1:5. Once a continuous cloudy day occurs, auxiliary energy can be automatically used to achieve fully automatic uninterrupted floor heating. The solar heating system converts solar energy into heat energy, collects the heat of sunlight through the solar panel heat collecting device, introduces heat into the energy storage tank through the heat conduction cycle, introduces heat into the room through the heat dissipation end, and controls the indoor water temperature through the electronic control instrument.


The solar heating system consists of a solar collector section, a thermal energy storage system, an auxiliary heating system, a domestic hot water end system, and a heating end system supply.

1  Solar collector

The solar collector is a key component in the whole device. It mainly collects the amount of solar energy and heats the water in the hot water storage tank. In the solar heating and hot water system device, the type of collector is generally selected as a flat type, which has the advantages of simple structure, long service life, high pressure bearing, low maintenance rate, and easy integration with buildings.

2  Solar water storage tank

The water tank insulation material is made of polyurethane foam.Fully automatic solar floor heating system.

3  Auxiliary heating

The auxiliary energy system is a supplement and backup for the solar collector system. When the solar energy system cannot meet the heating demand, the auxiliary energy source is activated to heat the water in the hot water storage tank, and stops when the set temperature is reached.

4  Solar heating end

It is a building heating equipment in the solar energy integrated energy system. At present, the best heating end equipment matching the solar heat source is the floor heating hot water coil or the fan coil.

B. Fully automatic solar floor heating system

The fully automatic solar floor heating system consists of a vacuum tube solar collector, a hot water storage tank, auxiliary energy and floor heating.


It is required that the water pipeline of the whole system must use a plastic pipe with an oxygen barrier layer. At present, most of the floor heating systems and radiator connecting pipes do not use oxygen barrier tubes, which leaves hidden dangers for future use. Because plastic pipes have a large characteristic compared with metal pipes, the intermolecular structure is very large and belongs to high polymer. Oxygen molecules can penetrate into the water body through this gap. If it is an ordinary plastic pipe, without oxygen barrier, the oxygen penetration is 100% (equivalent to changing the whole system every 2 days), if you want to add it to the oxygen barrier, his oxygen The penetration rate is reduced by 99.6% (equivalent to changing the new system every 125 days). What kind of harm does aerobic presence have on water bodies? There are two main ones, one for steel, ie the system Corrosion occurs in the presence of steel products, which affects the life of the entire system; the other is in the water body, if there is oxygen, it is easy to have algae breeding, water treatment is clean, it is also contains E. coli Microorganisms, which will continue to multiply in the presence of oxygen, as a pipeline for floor heating, may only have a layer of green mites attached for ten years, but within 50 years of use, this membrane is easy to block the pipeline, the most direct It is the performance that affects its heat conduction. In some countries in Germany and Europe, there must be an oxygen barrier layer for the mandatory implementation of heating pipes. The recommendations for floor heating in our country also mention the recommendations, which are recommended but not enforced, because the pipes produced in the present are almost Without oxygen barrier. It is recommended in the specification to require the use of a tube that blocks the oxygen barrier, or to add an oxygen barrier to the water.


The vacuum tube solar collector and the hot water storage tank form a separate circuit, which is controlled by a temperature control cabinet with two temperature control circuits W1, W2. Wl measures the temperature of the vacuum tube solar collector water tank, W2 measures the water temperature of the hot water storage tank, and requires that when Wl is greater than 60 ° C (the temperature can be set by the user, the same below), the solenoid valve 1 is opened, and the hot water pump is started for a few seconds. When Wl = W2, the solenoid valve 1 and the hot water pump are turned off. When W2 is 45 °C, it is required (Wl-W2 is greater than 20 °C to open solenoid valve 1 and hot water pump; when Wl=W2, close solenoid valve 1 and hot water pump. When W1=5 °C, open solenoid valve 2, Let the water from the collector be drained.


Auxiliary energy, hot water storage tanks and floor heating form a separate circuit. The auxiliary energy source can be a gas furnace, an electric heater, a heat pump, etc., has a hot water pump, and has two temperature control circuits F1 and F2. Fl measures the temperature of the water inlet, and requires that when the water temperature is lower than 40 °C, the auxiliary energy source is activated, such as ignition, power supply, etc.: When the water temperature is higher than 40 °C, the auxiliary energy source is turned off. F2 measures the indoor temperature of the floor heating. It is required to stop the operation of the hot water pump when the indoor temperature is higher than 22 °C. When the temperature is lower than 18 °C, the hot water pump is started to circulate the floor heating system.


Hot water storage tanks require high insulation performance and very good insulation measures for all nodes entering and leaving the pipeline. The overflow pipe adopts a check valve. When the pressure in the tank rises, it will drain or exhaust. Otherwise, when the pressure is reduced to negative pressure, the outside air should not be sucked back. The water supply drain pipe is also a check valve, which requires the inside of the tank. When the pressure is negative, the treated low oxygen content water is automatically replenished.


The floor heating system determines the type and quantity of water separators depending on the size of the heating area. At the same time, buildings with floor heating are required to have higher insulation performance.

C. Simple solar heating system

Using this system, we can retrofit existing non-central heating homes. For the families living in urban areas, some are floor heating, and some are radiator heating. No matter what kind of heating method, there is a gas furnace with a temperature control circuit as the heating energy source. As long as a small hot water storage tank is connected in series in front of the water inlet of the gas furnace, the storage tank and the outdoor vacuum tube solar collector form a simple temperature-discharging circuit to achieve the purpose of solar heating.


For the majority of rural families, this system can be used more simply. The auxiliary heat source can be used in the coal stove for cooking at home. It can be supplemented with three meals a day and boiled water. A vacuum solar collector with a temperature of about 8 square meters can meet the daily heating needs. All investment can be recovered in 3 to 4 years.


Solar energy storage heating introduction

Solar energy storage heating is divided into day storage heating, weekly energy storage, and inter-season energy storage heating.

a.  Energy storage on the same day

On the same day, energy storage refers to the use of solar collectors to collect the heat energy of the day and store it in the water tank to meet the heating demand at the end of the building.

b. Weekly storage energy heating

Weekly storage energy heating refers to the use of solar collectors to collect the heat energy of a week into the water tank to meet the heating demand at the end of the building. The area of the collector is determined by the amount of solar radiation in a week, and the capacity of the tank is slightly larger than that of the day's storage heating system. Suitable for holiday villas that are not inhabited.

c. Inter-season energy storage heating

Inter-season energy storage heating refers to the use of solar collectors to collect heat from spring, summer and autumn in the water tank to meet the heating needs at the end of the building. The area of the collector is determined according to the solar radiation amount of the three seasons, and the capacity of the water tank is more than 10 times the water tank of the storage heating system on the same day. Suitable for villas that do not have enough space for solar collectors.

Auxiliary energy selection

Introduction of auxiliary energy: oil boiler, gas furnace, biomass boiler, coal-fired boiler, electric heating, (electric heating or external electric heater built in water tank), heat pump.


The coal-fired boiler has a long start-stop time, and it is difficult to adjust the output. It is difficult to achieve self-control or unattended duty, and there are environmental pollution problems;


The fuel and gas boilers are easy to control and easy to adjust, which can be easily realized by self-control operation, but the equipment needs to meet the fire protection requirements;


The heat pump has low operating cost and convenient control, but the initial investment of the equipment is high. In addition, the air source heat pump in the northern region has a low energy efficiency ratio in winter;


The electric heating equipment is easy to install and convenient to control. It is the most commonly used auxiliary heat source for solar water heating systems, but the operating cost is high, and sometimes the system investment is greatly increased due to the need for power capacity expansion.


In selecting an auxiliary heat source, it is necessary to consider various factors.

Selection of auxiliary materials for solar heating systems

1. Pipe

The pipes and fittings used in the solar heating system shall comply with the current product requirements. The working pressure and working temperature of the pipeline shall not exceed the allowable working pressure and working temperature of the product standard calibration.


The solar collector system pipeline can be made of steel pipe, thin-walled stainless steel, plastic hot water pipe, plastic and metal composite pipe. The antifreeze system with ethylene glycol as the main component should not be galvanized steel pipe.


Hot water pipes should be made of pipes that are corrosion resistant and meet sanitary requirements. Generally, thin-walled copper pipes, thin-walled stainless steels, plastic hot water pipes, plastic and metal composite pipes, etc. can be used.


When designing, auxiliary equipment such as exhausting device, draining device, thermometer, pressure gauge, safety valve and expansion water tank should be installed at the necessary position of the system pipeline. The closed system should be provided with an expansion tank or a pressure relief valve.

2. Pipe insulation

The collector system, water tank and water supply pipeline of the solar water heating system should be insulated. Commonly used insulation materials are rock wool, glass wool, polyurethane foam, rubber foam and other materials.

Pipe insulation materials are selected in the following requirements:

1) The allowable use temperature of the insulation material product should be higher than the maximum medium temperature of the solar system.


2) Insulation materials should not be used to avoid insects. Rot, bacteria, and mice.


3) It is advisable to use materials with low hygroscopicity, weak water storage and no corrosive effect on the pipe wall; outer layer insulation layer should be protected with waterproof layer.


4) Insulation materials should be non-combustible and non-combustible materials. It should meet the requirements of GB50016 "Code for Fire Protection of Building Design"; the insulation of electric heaters must use non-combustible materials.


3. The efficiency of the solar energy system is closely related to the type of collector and the working temperature of the working fluid. The heat dissipating components of the solar heating system are selected according to the following principles:

1) Solar heating heating system should give priority to low temperature radiant heating system.


2) Water-air treatment equipment and radiator systems should use solar collectors with higher efficiency at 60-80 °C operating temperature, such as high efficiency flat solar collectors or heat pipe vacuum tube solar collectors. The system is suitable for hot summer or cold or mild areas.


3)The hot air heating system is suitable for low-rise buildings or local places where heating is required.

4. Design points of low temperature radiant heating system

1)Solar heating system is more suitable for low temperature radiant heating. The water supply temperature should not exceed 60 °C, and the temperature difference of the return water should be about 10 °C. The water supply temperature of the solar heating system should be 35-50 °C; the working pressure of the heating system should not exceed 0.8 Mpa.


2)Ground structure

The ground structure consists of a slab or a floor adjacent to the soil, a thermal insulation layer, a heating pipe, a filling layer, a leveling layer, and a surface layer. An insulating layer shall be provided on the ground adjacent to the soil, and a moisture barrier shall be provided in the lower part of the insulating layer. The floor adjacent to the outdoor air must be provided with an insulating layer. For wet rooms such as bathrooms, laundry rooms, bathrooms and swimming pools, a barrier layer should be provided on the upper part of the filling layer. When the project allows the ground to be designed in two-way heat dissipation, there may be no insulation on the floor between the floors.


The surface layer should preferably be a material having a thermal resistance of less than 0.05 m2 ° C / W. The thermal resistance of granite, marble, ceramic tile, etc. is 0.02m2.°C/W, the thermal resistance of the wooden floor is 0.10m2.°C/W, and the thermal resistance of the felt is 0.15m2.°C/W.


The thermal insulation layer is made of polystyrene foam plastic plate, the bulk density is not less than 20kg/m, the compressive strength is not less than 100kPa, and the thermal conductivity is not more than 0.41w (m. °C). The thickness of the thermal insulation layer should satisfy: the thermal insulation layer on the floor between the floors. Not less than 20 mm, the insulation layer on the floor adjacent to the soil or outdoor air is not less than 40 mm.


Uninterrupted expansion joints shall be laid at the intersection with vertical members such as inner and outer walls, columns and crossing doors. The width of expansion joints shall not be less than 20mm, and the expansion joints shall be made of polystyrene or high foamed polyethylene foam; the area of the local area shall exceed 30m2. Or when the side length exceeds 6m, expansion joints shall be provided. The width of the expansion joints shall not be less than 8mm. The expansion joints shall be made of high-foamed polyethylene foam or filled with elastic expansion paste.


The material of the filling layer should be C15 bean stone concrete, and the particle size of the bean stone should not be larger than 12mm. The thickness of the filling layer should not be less than 50 mm. If the ground load is greater than 20Kn/m2, the structural designer should use reinforcement measures.


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