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Sunpower Solar and air source heat pump assisted central hot water system

Views:2     Author:Site Editor     Publish Time: 2019-06-13      Origin:Site

SAP - the acronym for Solar air heating-pump, the central heating system of SAP absorbs solar energy through a concentrating collector, driving an air source absorption heat pump unit to extract heat from the air to reach solar energy. The perfect combination of air energy makes the two new energy sources natural. It is the latest technology in the world of clean energy.

"Zero" operating expenses

In the time of the sun, the operation of S.A.P uses solar energy and air energy. The power consumption is only equivalent to the consumption of several bulbs (0.8KW), and the operating cost is almost “zero”.

In the absence of solar time, the operation of S.A.P can be used to reserve solar and air energy, and the operating cost is almost "zero."

“Zero” investment

S.A.P is a distributed central heating system. Each building system is relatively independent, and can be gradually invested according to the progress of the project to increase capital liquidity. The S.A.P system of each building can also gradually invest according to the actual utilization rate, further increasing the liquidity of funds. If you use financial leasing or BOT to rent and sell, use the saved energy costs, and repay the principal and interest, you can get the S.A.P system for free, and the investment is almost “zero”.

S.A.P ultra-low temperature operation

S.A.P can work normally at minus 30 degrees, creating a precedent for air-cooled heat pumps.

Long life

S.A.P adopts ultra-white tempered glass and automatic disaster-resisting design, which can resist 12-class typhoon, blizzard, hail, etc., ensuring users have no worries for more than 20 years.

"Zero”emission

S.A.P can use solar energy and air energy almost all the time. When there is no sun, energy storage energy can be used, and carbon dioxide emissions are “zero”.

Small area, high floor

The thermal working fluid of S.A.P is MR717, which is a natural working fluid and has a destructive power to the ozone layer of “zero”. It is a working medium funded by UNEP.


The S.A.P high-efficiency collector and absorption heat pump main unit enables the heat collecting area under the same conditions to be only one quarter of the traditional solar vacuum tube collector, and the cost is lower, and the applicable floor is higher.

Central hot water system with perfect combination of solar energy and air source heat pump

In the large-scale solar central hot water system, the air source heat pump is undoubtedly an ideal auxiliary heating device. In order to improve the performance of the air source heat pump in the low temperature environment, the solar energy is utilized to solve the rainy weather and winter. When the ambient temperature is low, the hot water supply guarantee rate is insufficient when the solar energy resources are insufficient, so that hot water can be supplied all year round and all weather.

1  Solar-heat pump central hot water system

1.1 Solar energy - heat pump central hot water system basic composition

The main components of the solar-heat pump central hot water system are solar collectors and solar-assisted heating air source heat pump units. Other auxiliary equipments are the same as conventional central hot water systems, including solar circulation pumps, hot water heating ring pumps, and heat exchange systems. , hot water tank and controller.


Flat-plate collector is a kind of solar collector that has been applied earlier. It has always been the leading product in the world solar market. It is widely used in various low-temperature hot water heating fields, but with the advent of vacuum tube solar collectors, it is affected by it. The limitations of its own structure have no advantage in heat collection efficiency. Because the antifreeze problem and the heat collecting performance are greatly affected by the season and the environment, it is mainly applied in the winter in the south, and the winter is not good in the cold regions of the north. It is not recommended for use in large hot water projects.


U-tube vacuum tube collector, heat pipe vacuum tube collector and DC vacuum tube collector are developed on the basis of all-glass vacuum tube collector. The common features of all three have relatively high heat collection efficiency. As a heat absorbing body, metal can be operated under pressure, but it is comprehensively evaluated from the aspects of heat collecting efficiency, leak prevention, anti-scaling, durability, safety, reliability, installation and maintenance difficulty, and heat pipe type vacuum tube collector is the most suitable. The type of solar collector used in the central hot water supply system, followed by the U-tube vacuum tube collector and the DC vacuum tube collector. The heat pipe type vacuum tube collector utilizes heat pipe heat transfer, dry connection, no water in the pipe, small heat capacity, fast heat transfer, freeze resistance, heat shock resistance, strong pressure bearing, good heat preservation, no leakage, easy maintenance, etc. Advantages, the U-tube vacuum tube collector and the DC collector use the concentric sleeve in the vacuum tube to directly heat the working medium, in addition to the characteristics of high operating temperature, strong pressure bearing capacity and good thermal shock resistance, It has higher thermal efficiency than other forms of collectors, and can be installed horizontally, simplifying the mounting bracket, reducing the installation area, avoiding the collector's appearance on the building, and having strong adaptability in solar energy and building combination, but its installation procedure is better than The heat pipe vacuum tube collector is complicated, has many interfaces, and has hidden water leakage during operation, and the system maintenance cost is relatively high.

2  Solar-heat pump central hot water system works

The solar energy and solar energy auxiliary heating air source heat pump are combined as the heat source of the central hot water system. The purpose is to complement each other and make the two complement each other, and spare each other. When the sunshine is sufficient, the solar energy is preferentially used to heat the hot water, and the solar collector is used. The low-temperature hot water is used as an auxiliary heat source for the solar-assisted heating air source heat pump, thereby improving the operating condition of the heat pump and improving its heating performance. This combination makes the two work under relatively stable and efficient conditions, ensuring the system's all-weather sanitary hot water supply throughout the year. The air source heat pump heating process is essentially the utilization of the solar thermal energy contained in the air. According to the working characteristics of the heat pump, only one of the heat supplied by the heat pump unit as an auxiliary heat source during the operation of the entire hot water system A small part comes from electrical energy, so the solar-heat pump central hot water system greatly improves solar energy utilization and reduces the consumption of primary energy.


The solar-heat pump central hot water system operates mainly in the following four conditions:

(1) Solar heating domestic hot water

On most sunny days with good sunshine, the system works according to this working condition. At this time, the work of the solar circulation pump is controlled by the system controller according to the temperature of the solar collector and the hot water tank, and the heat collected by the collector is continuously utilized. It is transported to the hot water tank through an intermediate heat exchanger.

(2) Solar-assisted heat pump unit to heat domestic hot water

When it is cloudy or cloudy, when the solar collector temperature is lower than the hot water tank temperature to directly heat the domestic hot water, the heat pump unit starts, and the air is used as a heat source to heat the domestic hot water in the hot water tank. In the autumn and winter, when the ambient temperature is lower than the economic operating temperature of the heat pump, the heating efficiency of the heat pump unit decreases and the surface of the evaporator is frosted. At this time, the auxiliary pump heating cycle is started, and the low temperature solar hot water above the ambient temperature enters the heat pump unit. In the auxiliary heat exchanger, preheating the passing air, the heat pump efficiency is improved, and the cutting has the function of preventing frosting of the evaporator, and the power consumption of the heat pump unit can be saved.

(3) Solar and heat pump units simultaneously heat domestic hot water

When the sunshine is good on a sunny day, if the heat consumption of the hot water system is greater than the effective heat supply of the solar collector system or the number of solar collectors is small, the heat demand of the hot water system cannot be met, and the solar energy and heat pump units work simultaneously. Heating the hot water system.

(4) The heat pump unit directly heats the domestic hot water

In continuous rain and snow, the heat required by the hot water system is completely provided by the air source heat pump unit. At this time, the solar system is in a standby state, and the heat pump unit works alone to heat the hot water tank.

3  Solar-heat pump central hot water system design

3.1 Determination of the power of the solar-assisted heating air source heat pump unit

In the solar-heat pump central hot water system, the solar-assisted heating air source heat pump unit serves as an auxiliary heat source device for the solar collector system in sunny weather. When the solar energy resources are insufficient or the rainy weather is the main heat source of the system to ensure the normal supply of hot water, The heating power should be determined according to the design heat load of the entire hot water system. For the full-time central hot water system, the heat pump unit power is determined according to the hot water system design hour heat load. For the non-full-time central hot water system, the heat pump unit power should be based on the maximum water consumption, hot water tank volume, heating time and other parameters. determine. The rated heating power of the heat pump unit is not less than the design load of the central hot water system. In colder winter areas, the unit type can be appropriately increased to operate in a relatively high temperature during the day, in a shorter period. Meet the heat demand of the system within the time.

3.2 Determination of the area of  solar collectors

In the solar-heat pump central hot water system, the area of the solar collector should be based on the design heat load of the hot water system or the solar heat supply determined according to the actual situation, and analyze the solar collectors per unit area of the project site. The average daily effective heat is used to determine the installation area of the solar collector.


In hot water projects, solar collectors are generally installed at a fixed angle, and the daily effective heat per unit area varies with the season and the daily solar radiation intensity is not a fixed value. The influencing factors mainly include the installation angle of the collector, the operating conditions of the system, the meteorological parameters of the location and the amount of solar radiation. Different collector types have different heat collection efficiencies, and their effective heat gain is also different. Therefore, in practical applications, the performance parameters such as collector heat collection efficiency and solar radiation data provided by the collector manufacturer are generally analyzed and calculated. Take the annual average.

3.3 Solar collector system form

For the solar-heat pump central hot water system, the solar collector system serves as both the main heat source for hot water heating and the auxiliary heat source for the heat pump unit, and should be able to withstand lower ambient temperatures, so closed systems and system circulating fluids should be used. Use antifreeze solution.

4 The practical significance of solar energy-heat pump central hot water system

4.1 Operational Reliability Analysis

As a main component of the solar-heat pump central hot water system, solar and air source heat pumps are mature energy-saving and environmentally friendly products. The large-scale utilization of solar energy in domestic hot water systems has been more than 20 years old. The application of air source heat pumps has also been used for decades. [10] The solar heat pump central hot water system combines solar energy and air source heat pump technology. Under the condition that it does not affect the original operating functions of the two, the operating efficiency is significantly improved, thereby ensuring stable and reliable operation of the system and saving conventional energy consumption of the hot water system.

4.2 Analysis of energy efficiency

According to the solar radiation data of most parts of northern China, the heat collector area of  the solar water heating system is determined according to the average heat consumption of the sanitary hot water system and the daily average calorific value of the solar collector, and the solar energy-heat pump central hot water system, solar energy Direct heating can meet the heat demand of 60-80% of the hot water system throughout the year. The remaining 20-40% of the heat is supplied by the solar-assisted heating air source heat pump unit. The average COP of the heat pump can reach 3.0, that is, more than 65% of the heat supplied by the heat pump comes from Solar collectors and solar thermal energy cannot be directly utilized by collectors. In the whole system operation, the utilization rate of solar energy absorbed by the collector is close to 100%, and the power consumption of auxiliary heating only accounts for 7-14% of the total energy consumption of the system, which can save at least 85% more energy than the hot water system of conventional energy.


It can be seen from the above analysis that the solar-heat pump central hot water system is a reliable, environmentally-friendly and energy-saving hot water system. The system uses only solar energy and a small amount of electric energy, and does not have any pollution to the environment. It can be promoted and applied in most parts of China where the minimum temperature is above -15 °C during the day and the sun is well irradiated.


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