CN1293344A - Technique for accumulating heat by electric energy in low vally at night and heating or refrigerating at daytime - Google Patents

Abstract

A heating and cooling technology during the day using low-valley electric heat storage at night, which mainly includes a heat storage system, an electric heating system, a heat release system, a heat pump system, and a control system; its advantage is that it solves the problem of difficult direct storage of electric energy through heat storage , and can be dispersed and stored in situ as needed. The stored heat energy is taken out in the form of hot water or steam when needed and converted by a heat pump (refrigerator) for heating or cooling to improve the conversion efficiency of electric energy. It can also be directly heated by steam or hot water.

Description

Heating and cooling technology during the day using electric heat storage in the valley at night

The invention belongs to the technical field of effective utilization of electric energy

1. At present, the domestic and foreign technologies are as follows: 1.1 The status quo of foreign low-valley power utilization technologies

As early as the 1970s, some western developed countries such as the United States, France, Japan, etc. were impacted by the energy crisis, and at the same time there were contradictions between peak and valley loads. After more than 20 years of research and development, a number of electricity storage technologies have been applied to the utilization of low-peak electricity in the world. Zink and John reported in the article "Who says you can not store electricity" published in Power Engineering Magazine Volume 101 No. 3 in March 1997 that the more mature ones include pumped storage power plants, cold storage air conditioners, batteries, etc. At present, the electricity storage technologies being researched and developed include superconducting, compressed air, flywheel, and steam storage. In terms of promoting low-valley power utilization technologies, some countries' power departments have given support from the peak-valley power price difference. In the United States, the price difference between peak and valley is 5 times, and for every 1kw of peak power transferred, the power supply department can also get a reward of 100-500 dollars. In terms of technology development and research, the American Society of Heating, Air-Conditioning and Refrigeration Engineers, the Electric Power Research Institute, the International Energy Storage Advisory Committee, the Energy Storage Application Research Center, and some companies and universities have done a lot of work to make their technology mature. South Korea actively encourages the method of shifting peaks and filling valleys. For every 1kw of electricity transferred by the user, the one-time reward amount is 2,000 US dollars. In 1990, more than 24% of the air-conditioning projects being newly built or rebuilt in North America used ice-storage air-conditioning systems, and it has reached 30% at present, and it is expected to be fully popularized by the end of this century. Huang Hu reported in the article "Application and Promotion of Ice Storage Air Conditioners" published in the first issue of Energy Research and Utilization Magazine in 1996 that in 1987, 60% of the air conditioners in Tokyo, Japan were equipped with ice storage systems. 60% of the central air-conditioning system (power consumption) has adopted cold storage technology. 1.2. Research on Application Technology of Low Valley Electricity in my country

At present, pumped storage power stations, lead storage batteries, cold storage air conditioners, heat storage boilers, etc. have been put into practice and application. The implementation of these schemes has alleviated the contradiction of peak and valley loads to a certain extent, but due to the constraints of some factors such as natural conditions, economic benefits, and application range, they have not been widely used, so they cannot fundamentally solve this problem. Contradiction, to continue to develop effective low-peak power utilization technology has become an urgent problem to be solved.

Therefore, with the increasing development of large-scale generating units and nuclear power generation, it has become a very urgent issue to rationally utilize low-peak power and solve power storage and conversion technologies. At present, the country has issued a number of policies to provide guarantees for the development and utilization of low-valley power technologies. The time for my country to promote and implement low-valley power utilization technologies has arrived. 1.3. Several Low-valley Electricity Utilization Technologies

Pumped storage power stations, cold storage air conditioners, heat storage air conditioners, and storage batteries are four low-valley power utilization technologies that are relatively mature in the world and in my country and have been put into use. 1.3.1 Pumped storage power station

The pumped storage power station is based on the principle of energy conversion, using the excess electricity when the power load is low, to pump the water from the lower place to the upper pond (or reservoir) at the upper place, and this part of the water is then used to generate electricity through the turbine unit, which is used for power system regulation. peak. The pumped storage power station is not only a power user, but also a power source for system peak regulation. Judging from the working status of the pumped storage power station, it mainly operates in two states: pumped water consumption and peak-shaving power generation.

The pumped storage power station has many advantages. It can effectively adjust the peak and fill the valley, especially for the power system with a large peak-valley difference. It increases the low load, reduces the start and stop of generator sets, and enables the grid to operate economically and safely. In addition, the pumped storage power station can also be used for frequency regulation of the system, emergency backup, and reduction of environmental pollution. But it also has many restrictive factors, such as high construction cost, site site is limited by special requirements (the upper pool and the lower pool with suitable height difference), can not be close to the power station or load center, resulting in increased transmission loss, low power storage efficiency, etc. wait. According to Anon's article "Electric-energy storage hinges on three leading technologies" published in Power Magazine Volume 139, Issue 8, published in 1995, at present, the storage efficiency of commonly used pumped storage power stations can reach 10%. Has been applied more. my country's Guangdong, Zhejiang and Beijing Ming Tombs have also been completed or are under construction. Among them, the second phase of Guangzhou Pumped Storage Power Station was listed as a national key construction power project in 1998. 1.3.2 Cold storage air conditioner

Cold storage air conditioners use the power in the low-peak period of the power grid load for cooling. By using the latent heat or sensible heat effect of the cold storage medium, the cooling capacity is "stored" and released during the peak load period of the power grid. It is used for building air conditioning to bear the peak period. Full or partial load required by air conditioning. Therefore, the use of cold storage air conditioners can play a great role in the work of shifting peaks and filling valleys of electric loads. At present, there are many cold storage methods used in air conditioners, which can be divided into two categories: sensible heat storage and latent heat storage according to energy storage methods; The structure of the device can be divided into coil type, plate type, ball type, ice crystal type and ice sheet sliding type and other forms.

Taking the coil-type cold storage air conditioner as an example, the working principle of the cold storage air conditioning system is: at night, the ethylene glycol refrigerant passes through the chiller, the ice cylinder and the bypass to form an ice storage cycle. At this time, the temperature of the solution outlet water is -33°C. The cooling capacity is transferred to the water in the ice cylinder through the coil, so that the water freezes, and the return water temperature is 0°C; during the day, the secondary refrigerant passes through the ice cylinder and parallel bypass, and the flow of the ice cylinder is controlled by setting the outlet water temperature regulating valve The ratio to the parallel bypass flow ensures that the temperature of the outlet water is at a given threshold, and then the cooling capacity is incorporated into the conventional air conditioning pipe network through the heat exchange system, or directly sent to the air conditioner for use in the form of large temperature difference air supply.

At present, the most commonly used cold storage methods are water cold storage, ice cold storage and eutectic salt cold storage. Water storage is to use the sensible heat of water to store cold energy. Specifically, it is to use low-temperature water at 3 to 5°C for cold storage. Its advantages are: low investment, low technical requirements, low maintenance costs, and conventional air-conditioning and refrigeration systems can be used. However, due to the low energy storage density of water [the specific heat of water is 4.2kj/(kg°C)], only 8°C temperature difference can be used, so the system has the disadvantages of large floor area, large cooling loss, and troublesome waterproof and heat preservation. Therefore, water storage technology is more suitable for the expansion or transformation of existing conventional air-conditioning and refrigeration systems, and can increase the refrigeration capacity without increasing or slightly increasing the capacity of the refrigeration unit. Ice storage uses the latent heat of phase change of ice to store cold energy. Since the cold storage density of ice reaches 334kj/kg at 0°C, the volume required for ice cold storage is much smaller than water cold storage to store the same amount of cold. Therefore, its advantages are: high energy storage density, almost constant cold storage temperature; the volume is only a few tenths of water cold storage, which is convenient for storage, has low requirements for cold storage containers, takes up little space, and is easy to make standardized and serialized The equipment brings great convenience to users. But at the same time, it requires a high technical level of the cold storage system, must use a refrigeration unit with a low evaporation temperature, and requires a low evaporation pressure of the refrigerant, so the energy consumption of the compressor is high, and the design and control are far more complicated than the water cold storage system. After the time-of-use electricity price is implemented, the combination of ice storage and low-temperature air supply in the air-conditioning project can compete with conventional air-conditioning economically. Eutectic salt cold storage is another form of cold storage that utilizes the characteristics of solid-liquid phase transition. The cold storage medium is mainly a mixture of inorganic salts, water, coagulants and stabilizers. At present, the most widely used is the eutectic salt cold storage material with a phase transition temperature of about 8-9°C, and its latent heat of phase transition is about 95kj/kg. Although the phase transition temperature is relatively high, it is difficult to popularize and apply due to its low energy storage density, large equipment footprint, high requirements for equipment, and large investment.

Cold storage air conditioners can be used for full-load cooling or partial-load cooling. Full-load cooling is to store the cooling capacity stored during the day in the valley period at night, and the air-conditioning load during the day is fully satisfied by the cooling capacity stored at night. This cold storage method has the best peak shifting effect, but the initial investment is large and the investment recovery period is long. Partial cold storage is to store part of the cooling capacity required during the day at night, and the refrigerator and cold storage system work at the same time during the day to meet the requirements of the air conditioning load. This cold storage method can not only transfer part of the peak electric load, but also reduce the total installed capacity of electricity, and reduce the total investment of the cold storage system, which is a method more acceptable to users.

In the past two decades, cold storage air-conditioning technology has developed rapidly in some western developed countries, such as the United States, France, Japan and other countries, and has been successfully promoted and widely used locally. At present, the more mature ice storage systems in the world include FAFCO, CALMAC, BALTIMORE, and YORK systems in the United States, and CRISTROPIA and IBIS systems in France. Since the 1990s, cold storage air-conditioning technology has also developed rapidly in our country. According to incomplete statistics, there are more than a dozen companies and factories engaged in the production and engineering application of cold storage equipment, and nearly 15 projects have been completed or are currently under construction. In order to organize the application and promotion of cold storage, load regulation and power saving technology from a high starting point, the National Cold Storage Air Conditioning Research Center of China Energy Conservation Association was formally established in April 1995. The cold storage air conditioning research centers in Beijing and Jinan were also established one after another, and other provinces and cities were also established. Under construction. This will undoubtedly play a positive role in the development and progress of cold storage technology. 1.3.3 Thermal storage air conditioner

The regenerative air conditioner we refer to here refers to the application of the regenerative electric boiler in the central air conditioner. Its working principle is that when the power grid is at low load, the electric hot water boiler generates heat energy to make the water fully absorb heat, and then stores the heat energy in a specially set heat preservation container through a special system. In the case of load adjustment and peak avoidance, although the heavy-load electrical equipment is stopped, hot water can be automatically adjusted and delivered to the air-conditioning system from the heat-insulating container, and the air-conditioning can continue to be maintained for heating, so that the room can still be kept at a comfortable temperature Environment.

In this system, an electric hot water boiler is used to convert electrical energy into heat. The electric heating element is installed in a special closed metal casing, inserted into the hot water boiler, and the water is directly heated. Through the multi-layer baffle, the water is forced to circulate in the container to absorb heat. After reaching a certain temperature, it is transported to each heating point. . The thermal efficiency of the whole conversion process can reach 98%. The outlet water temperature is generally 40-65°C, and the highest can reach 75°C. Its dimensions increase with the increase of heating power. The main function of the hot water storage tank in the system is to store hot water and play the role of peak load regulation. The volume of the water tank must be determined according to the size of the heating area of the air conditioner, the characteristics of the user's site, the power supply and the length of heat storage time and other factors. The water tank is equipped with circulating water inlet and outlet, supply water inlet, safety valve, air release valve, sewage valve, inspection hole and automatic control instruments such as pressure, temperature and liquid level. There is also a circulation pipeline in this system, which is an important artery connecting heat supply, heat storage, heat utilization and other equipment. Reasonable design and layout of pipelines according to local conditions are important links to reduce energy consumption and facilitate operation.

To a certain extent, this heat storage air-conditioning system has played a role in shifting peaks and filling valleys, rationally using energy, and maintaining the normal operation of the power grid. As an energy-saving device capable of local peak regulation, it has been welcomed by the power sector. In addition, because of its clean environment, no pollution, and no pollution, it has played a certain role in promoting environmental protection. But for the user, this system uses water as the heat storage medium. Due to the low energy storage density of water [the specific heat of water is 4.2kj/(kg.℃)], the system occupies a large area and the heat loss is large. Waterproof and heat preservation are troublesome, the heating time is short, and the power consumption is large. Make the user use this heat storage air-conditioning system to be subjected to certain restriction. 1.3.4 Battery

The storage battery is a chemical battery consisting of an ion-conductive electrolyte and positive and negative electrodes on both sides. through an oxidation reaction. The difference in the Gibbs energy of the chemical reaction is converted into electrical energy and used by the positive and negative electrodes. Conversely, a reduction reaction occurs during charging. Batteries are widely used in modern energy-saving technologies. Its main application directions in the future are:

(1) Used for power peak regulation to alleviate the contradiction of power supply tension;

(2) Used in electric vehicles to improve system energy utilization efficiency and improve urban environmental protection conditions;

(3) Cooperate with the development of renewable energy such as solar energy and wind energy, and expand its use by storing electricity.

At present, lead-acid batteries are commonly used in countries all over the world. However, due to factors such as low energy density, low power storage efficiency, short life, unsuitable for large-scale, and poor economy, lead-acid batteries are no longer suitable for the needs of the contemporary world economy. All industrialized countries are devoting themselves to the development of new batteries.

In 1980, Japan included the development of new storage batteries for power peak-shaving systems as a large-scale energy-saving technology development project in the Moonlight Plan, with a planned investment of 17 billion yen, and required to achieve the practical goal in 1991: the output was 1000kw, according to 8h Charging and 8h discharging, the efficiency is over 70%, the life span is over 1500 times, the durability is 10 years, and the environmental protection meets the standard. Under the guidance of the above-mentioned plan, research and development were mainly carried out on 4 new types of storage batteries. They are sodium-sulfur batteries, redox flow batteries, zinc-chloride batteries, and zinc-bromine batteries. After basic research on the above four new types of storage batteries, prototypes were made for trial operation and comprehensive evaluation, and a network test was carried out in the power peak-shaving system. In March 1991, the New Energy Industrial Technology Comprehensive Development Organization responsible for organizing this project believed that this test was successful, and the comprehensive indicators after testing had fulfilled the requirements of the Moonlight Project. The problem is that the cost is relatively high, which is about 10 times that of the pumped storage power station. In the future, further research should be done to significantly reduce the cost, so that it can be gradually promoted after reaching a certain level. 1.3.5 Electric vehicles

From the perspective of energy saving and environmental protection, electric vehicles have good development prospects, so industrialized countries such as the United States, Italy, Japan, Germany, and France are competing to develop electric vehicles. The key technology is a new battery, which requires a storage density per unit weight. High, in order to obtain a longer mileage after a single charge, and combine it with power peak regulation, use the low-priced electricity in the valley as the power of electric vehicles, which increases the superiority and energy saving effect. At present, the batteries used in electric vehicles are mostly lead batteries and nickel-cadmium batteries. The former, such as the French Renault Motor Company and some Japanese car companies, use lead batteries because of their good reliability and low cost. The disadvantage is that they can travel a short distance after charging. Companies such as France's Peugeot Group and Italy's Fiat use nickel-cadmium batteries with twice the range. Because nickel-cadmium batteries are more expensive than lead batteries, and cadmium is easy to pollute the environment, Germany, which developed later, uses sodium-sulfur batteries, and Japan has developed nickel-hydrogen batteries that are cheaper than sodium-sulfur batteries and have similar performance. The Ni-MH battery produced by Panasonic Battery in Japan has reached more than 200km on a single charge, but because the price is twice as high as that of the lead battery, it is studying the recycling of nickel to greatly reduce the cost. Japan's Mitsubishi Group is centering on Mitsubishi Motors, with the participation of Mitsubishi Heavy Industries and Mitsubishi Electric, and proposes to develop small, high-efficiency batteries with the performance equivalent to gasoline vehicles and the goal of being able to travel 400km on a single charge. The U.S. Department of Energy also attaches great importance to this, and has organized relevant automobile factories and motor factories to draw up a three-year development plan for batteries for electric vehicles. According to a report in July 1992, the US VB Company has successfully developed a special battery that uses a flywheel mounted on a magnetic bearing in a vacuum to store energy. The walking distance of a single charge is five times that of a lead battery of the same weight. joint development. However, the Japanese Ministry of International Trade and Industry and the battery industry have recently advocated the development of large-capacity lithium batteries. According to K. Kanari and K. Takano et al. reported in the article "Joint research on thermal simulation technology for lithium secondary batteries" published in Bulletin of the Electrotechnical Laboratory, Volume 60, Issue 12 in 1996, that according to the demonstration of the energy density of lithium batteries, it is sodium-sulfur batteries by weight 3 to 4 times that of solar energy. In 1993, it was included in the development of the New Sunlight Project, and it has been put into practical use in ten years.

The purpose of the present invention is to provide a heating and cooling technology during the daytime by utilizing heat storage in the low valley at night to solve the prominent contradiction of power supply—the peak-valley difference between day and night of the power grid load. Solve the problem that the load rate in the valley section from night to early morning is low, and the power supply is tight during peak hours, so that the scale of the power plant must be configured according to the peak load, the power plant cannot generate electricity in a balanced manner, and the power grid cannot operate in the most economical state.

The design idea of "low-valley electricity storage heating and cooling" is to use low-valley electricity to heat the heat medium (thermal medium) at night to convert electric energy into heat energy and store it. Such heat medium needs to have a higher density. Only with high heat capacity and phase change heat can it use its sensible heat and latent heat to absorb a large amount of heat energy. The heat accumulated in the heat medium is converted into steam or hot water through the heat exchange device, and the steam or hot water is then provided to the heat pump (refrigerator) as a high-temperature heat source for heating and cooling to improve conversion efficiency. It is also possible to use the hot water or steam from the heat exchange device to directly supply heat to the outside.

The composition of the invention mainly includes a heat storage system; an electric heating system; a heat release system; a heat pump (refrigerating machine) system and a control system, etc. Its functions are: 1. Heat storage process: first use the low-valley electricity at night (non-valley electricity can also be used) to heat the heat storage material in the heat storage battery to melt it, and convert the electric energy into heat energy--the latent heat of melting of the heat storage material and the sensible heat of temperature rise storage; 2. Exothermic process: When water flows through the exothermic system, it is heated and becomes steam or hot water to flow out; 3. Heat energy utilization process: steam or hot water from the exothermic system enters the absorption heat pump (refrigeration) system as a high-temperature heat source, and drives the heat pump (refrigeration system) to supply heat or cold to the outside; steam or hot water from the exothermic system It can also be directly heated externally.

(1) The heat storage system mainly includes two parts: the heat storage tank and the heat storage material. The heat storage tank is a container made of heat-resistant stainless steel, heat-resistant cast iron or ceramic materials; the heat storage material is a metal material or a salt inorganic non-metallic material with a melting point temperature higher than 300°C and lower than 1000°C.

(2) The electric heating system mainly includes electric heating devices or elements placed on the outer surface of the closed heat storage tank (the surface not in contact with the heat storage material) or placed inside the heat storage tank and embedded in the heat storage material.

(3) The heat release system mainly includes metal coils or metal channels placed on the outer surface of the heat storage tank (the surface not in contact with the heat storage material) or placed inside the heat storage tank and embedded in the heat storage material. During the process, steam or hot water can be generated according to the process requirements. The generated steam or hot water can be directly supplied to the outside of the device or provided to the heat pump as the heat source of the heat pump.

(4) The heat pump (refrigerator) system is an absorption heat pump (refrigerator), which uses steam or hot water provided by the exothermic system as a high-temperature heat source for heating or cooling.

(5) Control system, an electronic control system that controls and monitors the entire device according to process requirements.

The invention has the advantages of solving the problem that electric energy is difficult to store directly through heat storage, and can achieve scattered storage on site according to needs. The stored heat energy is taken out in the form of hot water or steam when needed and converted by a heat pump (refrigerator) for heating or cooling to improve the conversion efficiency of electric energy. It can also be directly heated by steam or hot water.

First of all, it can adjust or alleviate the contradiction between peak and valley difference of electric load. If this technology can be popularized on a large scale, it can partially replace the coal-fired, oil-fired and gas-fired boilers commonly used in cities today, which will greatly increase the use of off-peak electricity, and play a role in shifting peak electricity consumption and reducing power consumption. The power demand during the peak period and the effect of balancing the power grid also enable the power plant to run smoothly, economically and safely, thereby improving power generation efficiency, improving the investment efficiency of the power plant and reducing the investment and waste of power construction, so that the overall The power supply level has been improved.

Second, the environment has been improved. Because electricity is the cleanest energy.

Again, it has better economic benefits. It is estimated that if the low-valley electric heat storage system is only used for heating, its one-time investment is not greater than that of a boiler system with the same heating capacity. After adding a heat pump or a refrigerator, although the investment increases, considering the addition of a cooling system in summer, the utilization rate of the equipment is improved, and the effect of adjusting the peak-valley difference of the power supply load is limited by the season. Therefore, the investment benefit remains the same. is higher.

Fig. 1 is a schematic diagram of a system of the present invention that directly supplies heat to the outside without going through a heat pump system. Among them, 1-control system, 2-power supply line, 3-electric heating element, 4-heat exchange coil water inlet circuit, 5-flow metering device, 6, 9-flow control valve, 7-heat exchange coil water outlet circuit, 8-Return water pipe, 10-User or external heating system, 11, 14-Pipeline pump, 12-Collecting tank, 13-Steam or hot water outlet, 15-Regenerator, 16-Heat-resistant insulation material, 17- Heat exchange coil.

Claims (2)

1, a kind of low ebb electricity accumulation of heat heating refrigeration on daytime technology of utilizing night, its formation mainly comprises hold over system, electric heating system, heat release system, heat pump and control system; The latent heat of fusion of heat-accumulating process: at first utilize the low ebb electricity electric energy at night to add heat-storing material in the thermal regenerator pond, make it fusing, convert electrical energy into heat energy--heat-storing material and intensification sensible heat-store; Exothermic process: water is heated when flowing through the heat release system, flows out after becoming steam or hot water; The heat energy utilization process: the steam or the hot water that go out the heat release system enter absorption heat pump (refrigeration machine) system as high temperature heat source, drive the outside heat supply of heat pump (refrigeration machine) or cold is provided; Go out the steam or the also directly externally heat supply of hot water of heat release system.

2, technology according to claim 1, it is characterized in that: hold over system mainly comprises accumulation of heat pond and heat-storing material two parts, the container of accumulation of heat pond for making with heat-resistance stainless steel, heat-resisting cast iron or ceramic-like materials, heat-storing material are melting temperature at 300 ℃-1000 ℃ metal material or salt Inorganic Non-metallic Materials; Electric heating system mainly comprise be placed on sealing accumulation of heat pond outer surface or be placed on the accumulation of heat pond inner and imbed electric heater unit or element in the heat-storing material; The heat release system mainly comprise be placed on accumulation of heat pond outer surface or be placed on the accumulation of heat pond inner and imbed metal coil pipe or metal passage in the heat-storing material, when water passes through wherein, can produce steam or hot water according to technological requirement, steam that is produced or hot water can be directly heat supply or offer the thermal source of heat pump outside device as heat pump; Heat pump is an absorption heat pump, and steam that provides with hold over system or hot water are that high temperature heat source heats or freezes.