The field of activity (technology) to which the described invention belongs
The invention relates to thermal power engineering, can be used in the combined production of heat, cold and electricity using thermal power plants.
DETAILED DESCRIPTION OF THE INVENTION
Known way to work mobile unit combined production of electricity, heat and cold, in which the generator converts the mechanical energy of the rotating motor shaft into electricity, the exhaust gases passing through the heat exchanger give off heat to the heat transfer fluid for heat supply to heating period or refrigerant from an absorption chiller for summer refrigeration.
The disadvantages of this method of operation of the installation include not high efficiency associated with the release into the atmosphere of a significant part of the unused thermal energy through the devices air cooling engine internal combustion and refrigeration machine, the low degree of use of the refrigeration capacity of the absorption refrigeration machine in summer during periods of low ambient temperature.
The method of operation of a cogeneration system is also known: the first internal combustion engine produces useful energy that is converted into electrical energy using an electric generator, the second internal combustion engine is used to drive the compressor of a refrigeration machine that produces cold in the summer, heat recovered from the engine jacket and exhaust gases, is used for heat supply to consumers in winter period.
The disadvantage of the method of operation of this installation is the low efficiency of the use of waste heat from internal combustion engines, the significant cost of electricity for the operation of the compressor of the refrigeration machine.
There is a known method of operation of a trigeneration system that simultaneously provides heat / cold and electricity, in which heat is supplied during the cold period by utilizing the heat of the exhaust gases and the coolant of the internal combustion engine, the mechanical energy of the rotating shaft of the engine is converted into electricity, the cold is generated in the summer in compression chiller.
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The disadvantages of the method of operation of this installation include low efficiency due to insufficient use of waste heat from the internal combustion engine and significant energy costs for the operation of the compressor of the refrigeration machine.
The closest technical solution (prototype) is a method of inlet of cooled air into a gas turbine, in which one is used to convert the heat of combustion products into mechanical energy, followed by its conversion into electrical energy in the generator. The second heat engine is used as a source of thermal energy, which is converted into cold energy in an absorption refrigeration machine. The cold produced in the absorption refrigeration machine is used for cooling atmospheric air before compression. When the load on the refrigeration system is reduced, the pressure of the gas supplied to the heat engine is reduced.
The disadvantage of the method of operation of this installation is that during the period of incomplete loading of the absorption refrigeration machine, as a result of a decrease in the pressure of the gas used by the heat engine, the temperature of the water supplied from the absorption refrigeration machine to the air-to-water heat exchanger increases, which leads to a decrease in the degree of cooling of the atmospheric air, supplied to the compressor, and, accordingly, to a decrease in the electric power of the installation.
The objective of the invention is to increase the efficiency and electrical power of the installation by increasing the degree of use of the absorption refrigeration machine.
The task is achieved in the following way.
Compressed atmospheric air and/or fuel is burned in the combustion chamber and the heat of the combustion products is converted into mechanical energy using a heat engine. Mechanical energy is converted into electrical energy in an electric generator. The heat energy removed from the heat engine is used for heat supply to consumers and for conversion in an absorption refrigeration machine into cold energy for refrigeration supply to consumers. During the partial load period of the refrigeration machine, the excess cooling capacity is used to cool the atmospheric air before compression.
The drawing shows a diagram of one of possible installations, with which the described method can be implemented.
Contains the following elements: 1 - air compressor, 2 - combustion chamber, 3 - gas turbine, 4 - heat exchanger for cooling turbine disks and blades, 5 - heat exchanger for the turbine lubrication system, 6 - flue gas heat exchanger, 7 - heat exchanger for the consumer heat supply system, 8 - air-water heat exchanger, 9 - pump cooling circuit, 10 - pump, 11 - absorption chiller, 12 - heat consumer, 13 - electric generator, 14 - cold consumer, 15 - pipeline hot water, 16 - chilled water pipeline, 17 - cooling tower of the refrigeration machine, 18 - reverse water supply (cooling) pump of the refrigerator, 19 - room, 20 - dry cooling tower of the trigeneration plant.
The way of operation of the combined production of electricity, heat and cold is carried out as follows
The compressor 1 is the process of compressing atmospheric air. From the compressor 1, the air enters the combustion chamber 2, where the atomized fuel is continuously supplied under pressure through the nozzles. From the combustion chamber 2, the combustion products are sent to the turbine 3, in which the energy of the combustion products is converted into mechanical energy of the shaft rotation. AT electric generator 13 this mechanical energy is converted into electrical energy. The thermal energy removed from the gas turbine through the heat exchangers of the lubrication system 5, the cooling system of the disks and blades 4 and from the exhaust gases 6 is transferred through the pipeline 15 to the heat exchanger 7 to supply consumers 12 with heat in the cold season. During the warm period, part of the thermal energy is used to heat consumers, and the other part of the energy is transferred to the absorption refrigerator 11, which converts thermal energy into cold energy used to supply cold to consumers 14. The water cooled in the heat exchanger 7 is transferred by pump 9 for heating to heat exchangers 4 , 5, 6. If there is no need for thermal energy, excess heat is removed through dry coolers 20 to the atmosphere. When the chiller is running 11 thermal energy is supplied to the generator and to the evaporator, while heat is removed in the absorber and condenser. To remove heat to the atmosphere, a circulating water supply circuit is used, which includes a cooling tower 17 and a pump 18. During the period of incomplete loading of the absorption refrigerator 11, the chilled water is transferred through the pipeline 16 to the air-to-water heat exchanger 8, located outside the room 19, to pre-cool the atmospheric air, supplied to the compressor 1 for compressing atmospheric air and supplying it to the combustion chamber 2, and the water heated in the heat exchanger 8 is transferred by the pump 10 to the 11 for cooling.
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The technical result that can be obtained in the implementation of the invention is to increase the degree of use of the absorption refrigerating machine due to cooling during the period of its incomplete loading of atmospheric air before its compression. Preliminary cooling of atmospheric air by reducing the work of compression makes it possible to reduce fuel consumption in a heat engine, increase the efficiency and electric power of the installation.
List of sources used
1. Patent 2815486 (France), publ. 04/19/2002, IPC F01N 5/02-F02B 63/04; F02G 5/02; F25B 27/00; F25B 30/04; F01N 5/00; F02B 63/00; F02G 5/00; F25B 27/00; F25B 30/00; (IPC 1-7): H02K 7/18; F01N 5/02; F02B 63/04; F02G 5/02; F25B 27/02.
2. Patent 2005331147 (Japan), publ. 12/02/2005, IPC F25B 27/00; F25B 25/02; F25B 27/02; F25B 27/00; F25B 25/00; F25B 27/02; (GRS1-7): F25B 27/00; F25B 25/02; F25B 27/02.
3. Patent 20040061773 (Korea), publ. 07/07/2004, MCP F02G 5/00; F02G 5/00; (IPC 1-7): F02G 5/00.
4. Patent 8246899 (Japan), publ. 09/24/1996, IPC F02C 3/22; F01K 23/10; F02C06/00; F02C7/143; F25B 15/00; F02C 3/20; F01K 23/10; F02C06/00; F02C 7/12; F25B 15/00; (IPC1-7): F02C 7/143; F02C 3/22; F02C06/00; F25B 15/00.
Claim
A method for the combined production of electricity, heat and cold, including the compression of atmospheric air and / or fuel, followed by their combustion in a combustion chamber and the conversion of the heat of the combustion products into mechanical energy using a heat engine, converting mechanical energy into electrical energy in an electric generator, the transfer of part of the thermal energy removed from the heat engine for conversion in an absorption refrigeration machine into cold energy used at least to cool the atmospheric air before it is compressed, characterized in that part of the thermal energy removed from the thermal the engine is used for heat supply to consumers, and the thermal energy converted in the absorption refrigeration machine into cold energy is used for refrigeration supply to consumers, while if excess cold energy occurs during periods of incomplete loading of the absorption refrigeration machine, it is used to cool atmospheric air before compression.
Inventor's name:
Bazhenov Alexander Ivanovich (RU), Mikheeva Elena Vladimirovna (RU), Khlebalin Yury Maksimovich (RU)
Name of the patent holder:
State educational institution of higher vocational education Saratov State Technical University (GOU VPO SSTU)
Postal address for correspondence:
410054, Saratov, st. Politekhnicheskaya, 77, SSTU (patent and license department)
Patent start date:
14.05.2009
Electricity in Russia is such a thing that can be suddenly turned off, which can go up in price or become worse in quality. If you have a data center, a hospital, a shopping center or another important facility, it is logical to take care of your own power source: starting from a certain amount of energy consumed, it is advantageous not to be powered from the city, but to build your own energy center.
Photos of the energy center in Naberezhnye Chelny
Considering that all these facilities (especially for the data center) will need not only electricity, but also heat and cold, large customers rely on their energy centers - and we are engaged in their design, construction and implementation, and we use very interesting scheme trigeneration, which allows you to immediately receive heat, cold and electricity without unnecessary transformations.
Under the cut - photos of the energy center, a short story about its structure and trigeneration in general.
Why do we need energy centers at all?
Electricity costs money. In many cases, it is cheaper to build an energy center than to build infrastructure and pay the city regularly for food. The question “how much electricity, heat, water and cold will cost after putting the facility into operation” is no longer a minor issue today.Often, even the choice of site is not only based on a convenient location for future customers, but also in terms of the possibility and cost of providing the necessary energy resources. It is difficult to plan something when the planned electricity tariffs increase by 1.5-2 times after the commissioning of the facility with the wording “the newly commissioned facility was not included in the balance sheet of the generating supplier”.
Decision
One of the ways out in this situation can be the construction of own generating capacities (own energy center) on the basis of gas piston or gas turbine units with heat recovery using absorption chillers (ABKhM). The whole trick is just that all the "surplus" of heat or cold is not "dumped" somewhere in the process of generating electricity, and is used for the corresponding consumers of the object.The principle is this: during the operation of a gas piston or gas turbine plant, with 1 kW of generated electricity, we can get from 1 to 2 kW of thermal energy as hot water. In full and operating data centers, the electrical load is fairly uniform throughout the year, and the need for cold is comparable to the active electrical IT power. From hot water with the help of ABCM we get cold with an average coefficient of 0.75. Thus, depending on the type of power plants, from 50% to 100% of the required cold can be obtained from their heat. The result is extremely energy efficient system. The lack of heat, as well as the reserve is provided by conventional hot water boilers, whose efficiency is close to 99%.
Externally, only natural gas is consumed low pressure, the output is electricity, heat for heating and cold for air conditioning. At the same time, reliability exceeds standard suppliers, and the cost of resources is noticeably lower. The cost of electricity consumed is up to 2 rubles/kWh and below, which corresponds to external tariffs for voltages of 110 kV and above.
The combined generation of electricity, heat and cold makes it possible not only to reduce energy costs by 2 or more times, but also to reduce the volume of electricity consumption for ventilation and air conditioning. This is achieved by completely or partially replacing the compressors of the cooling system with ABKhM, which practically does not consume electricity. The experience of the projects we have implemented shows that the payback of our own energy center with the right technical solution only 2-3 years, after which the solution begins to bring additional profit to the owner.
The energy center is an independent, fully automated engineering structure working in offline, which includes power plants based on a gas engine and an attached electric generator.
What are the benefits?
When building a high-availability data center, the main source of electricity should be an input independent of the power system, traditionally implemented on the basis of diesel generating sets("city" on the levels above cannot be the main one).Average cost of 1 kWh per diesel fuel varies from 7-10 rubles. For these reasons, the “main” input remains as such only on paper, and electricity in normal mode is received by classical schemes from the mains, that is, from an additional source according to the standard. A small data center with a total capacity of 1 to 2 MW will be connected to the power grid at a voltage of 6 or 10 kV, and will buy electricity at the appropriate tariff group (from 3 to 4 rubles / kWh). With this approach, the cold in the cooling system of the data center is generated by vapor-compression refrigerating machines (VCRs), which consume mains electricity.
The refrigeration capacity of the PCCM cycle is related to power consumption through ε - the coefficient of performance.
For middle lane Russian ε approximately 3.0. This means that to generate 1.0 kW of cold, an electrical power of 0.33 kW is required.
At the same time, it is more than realistic to install your own gas power center (where there is a trigeneration system). As a result, the required amount of cold can be obtained using ABCM without the use of traditional (and expensive) compressors. The experience of designing and redundant systems has been accumulated quite a lot, so even for TIER III and TIER IV there is no fundamental problem in the construction and certification of such an object.
Specific example
One example is the energy center shopping center ESSEN in Naberezhnye Chelny, built by CROC in 2007. The project paid for itself in a little over 2 years, even with an incomplete load. We currently have several other similar projects in the works.Here is his card:
- Type of construction - new construction
- Location construction site– Naberezhnye Chelny, Republic of Tatarstan
- Construction stages - 1 stage
- Purpose - electricity, heat and cold supply of its own shopping and entertainment center.
- The reason is the absence technical feasibility accession to electrical networks.
- Rated power - electricity 2 MW - actual consumption 70%, thermal energy 4 Gcal - actual power consumption 3.7 Gcal, cooling consumption - 1.2 MW, actual consumption 1 MW
- CHP version - container
- Equipment - CGU - Caterpillar (USA), boilers - Buderus (Germany), ABHM - Carrier (China)
And here are his photos:
View of the cogeneration gas piston unit (CGU) inside, expansion tanks: 
Container with backup diesel generator 
Gas distribution point (GRP) of the energy center: 
Gas piston engine (GPU) CATERPILLAR: 
Absorption refrigerator(ABHM) inside: 
Heat exchangers heating point boiler room: 
GPU inside - setup: 
Exhaust gas disposer: 
Connection to the tires of the power board of the GPU: 
Cogeneration gas piston units (CGU): 
Dry cooler (drycooler) KSU: 
He also: 
KSU - chimneys, drycooler, exhaust gas utilizer: 
Summary
- The construction of its own energy center using turnkey trigeneration technology will cost approximately 2,000 euros / kWh. This is quite comparable to the price of connecting to external networks.
- Own energy center for the data center does not lead to an increase in investment, but significantly reduces the energy consumption of the data center and its OPEX as a whole.
- The reliability and efficiency of the data center is increasing.
- The choice of site can be approached more freely: the energy independence of the facility from local infrastructure is achieved, which can be an important advantage.
- The construction of the energy center is carried out in parallel with the construction of the main facility and the time frame is 1.5-2 years.
- CROC has experience in the construction of such facilities, so if you are interested, please contact [email protected], discuss concrete questions. Ready to answer general questions in the comments.
UPD. Many questions on payback and economic part. In general, it all depends on the specific project. General approaches are as follows (the numbers in the calculations are approximate, may differ in different situations and regions):
- It is important to provide for the most complete and stable marketing of all produced resources. If the consumption is uneven (day / night, seasonality), you can “cut out” only the stable part by the energy center, and get bursts from the network. In the sense that it is not necessary to take the power center under the peak, it is economically justified with a stable load above, for example, 60%.
- In the prime cost, more than half of the costs are the price of fuel. 270 cubic meters per 1 MWh, for example, 4 rubles per cubic meter and 8200 hours a year (taking into account the regulations and downtime) - this is about 9 million rubles. Let the service, staff, taxes, oil, etc. be the same, although less in experience. We get OPEX 18 million rubles or 2.19 rubles / kWh. A plug with an external tariff of 4 rubles \ kWh will be about 15 million rubles for electricity and at least 2 million rubles for heat. At large stations, the effect is even greater.
- The cost of the energy center depends on many parameters. Cogeneration of 1 MW (electricity and heat), in a container with one machine, even with a connection to the grid, costs less than 1 million euros on a turnkey basis. More difficult decision, including trigeneration is more expensive. For example, 1.5 million euros / annual savings of 17 million rubles = 3.5 years. The use of cold improves the situation by half. And if you take into account the cost of connecting to electrical networks, the project can pay off at the start.
A trigeneration system is a combined heat and power system connected to one or more refrigeration units. The thermal part of the trigeneration plant basically has a steam generator with heat recovery, which is powered by the exhaust gases of the prime mover. The prime mover, connected to the alternator, provides the production of electrical energy. The intermittent excess heat is used for cooling.
Application of trigeneration
Trigeneration is actively used in the economy, in particular in Food Industry where there is a need for cold water for use in technological processes. For example, during the summer, breweries use cold water for cooling and storage of the finished product. On livestock farms, water is used to cool milk. Frozen food producers work year-round with low temperatures.
The trigeneration technology makes it possible to convert up to 80% of the thermal power of a cogeneration plant into cold, which significantly increases the overall efficiency of the cogeneration plant and increases its power resource factor.
The trigeneration plant can be used year-round, regardless of the season. Recycled heat from trigeneration is effectively used in winter for heating, in summer for air conditioning and for technological needs.
Especially effective is the use of trigeneration in the summer, with the formation of excess heat generated by a mini-CHP. Excess heat is sent to an adsorption machine to generate chilled water for use in the air conditioning system. This technology saves energy that is normally consumed by a forced cooling system. In winter, the adsorption machine can be turned off if there is no need for a large amount of chilled water.
Thus, the trigeneration system allows 100% use of the heat generated by the mini-CHP.
Energy efficiency and high economic efficiency
Optimization of energy consumption is an important task, not only from the point of view of saving energy resources, but also from the point of view of the environment. Today, energy conservation is one of the most urgent problems in the world. At the same time, the majority modern technologies heat production leads to a high degree of air pollution.
Trigeneration, in which the combined production of electrical, thermal and refrigeration energy takes place, is today one of the most effective technologies improve energy efficiency and environmental safety mini-CHP.
Saving energy resources when using trigeneration technologies reaches 60%.
Advantages and disadvantages
Compared with traditional technologies cooling trigeneration system has the following advantages:
- Heat is a source of energy, which allows the use of excess heat energy, which has a very low cost;
- Produced Electric Energy can be fed into the general power grid or used to meet their own needs;
- Heat can be used to meet the needs for thermal energy during the heating season;
- Require minimum expenses for maintenance due to the lack of adsorption refrigeration units moving parts that could be subject to wear;
- Silent operation of the adsorption system;
- Low maintenance and low lifetime costs;
- Water is used as a refrigerant instead of substances that deplete the ozone layer.
The adsorption system is simple and reliable to use. The power consumption of the adsorption machine is small because there is no liquid pump.
However, such a system also has a number of disadvantages: large dimensions and weight, as well as a relatively high cost, due to the fact that today a limited number of manufacturers are engaged in the production of adsorption machines.
Trigeneration is the combined production of electricity, heat and cold using a gas engine. The composition of the trigeneration plant (TGU): gas piston engine generator, thermal module, absorption refrigeration machine, control system. The generator generates electricity, the thermal module in winter time, and the absorption chiller in summer time utilize the heat of the engine cooling jacket, oil cooling jacket and waste flue gases
Trigeneration is beneficial because it makes it possible to efficiently use the recovered heat not only for heating in winter, but also for air conditioning or technological needs in summer. This approach makes it possible to use all year round thus providing the fastest return on investment. Maximum proximity and the possibility of using for any consumer both as the main and backup energy source, installation anywhere (even in an "open field"), reliability in operation, quick payback and long term services of the main equipment (up to 25 years before complete decommissioning) bring TSU to the first place among alternative sources power supply. All you need is gas.
INTEGRATED APPROACH TO PROJECT IMPLEMENTATION Conducting an energy audit: identifying specific features in the energy supply at the customer’s site Project development, equipment configuration selection Production and supply of equipment technical support
TGU can be used both as a main and as a backup power supply Petrol 1.5 - 12 kVA Diesel 1.5 - 2000 kVA Gas 23 - 1500 kVA MTU FORD PERKINS VOLVO LOMBARDINI HONDA Engines: Generators: MECC ALTE Stamford engine characteristics
What you need to pay attention to when choosing a gas cogenerator: a) voltage b) electric power c) location (site) d) daily electricity consumption e) mode of operation (island or in parallel with the network) f) availability of gas limits, gas pressure g ) starting currents h) design
AUTONOMOUS POWER SUPPLY IS MORE PROFITABLE! FACTORS OF ECONOMIC EFFICIENCY OF AUTONOMOUS POWER SUPPLY 1. Natural gas quite cheap. Cogenerators have high efficiency. There are no power losses. Therefore, electricity generated autonomously using cogenerators is 2 to 5 times cheaper. 1. There is no need to pay for connection to the power grid and lay a heating main (for new facilities). There is no need for constant repair of existing heating mains (for old facilities). 2. The cogenerator utilizes the heat generated when generating electricity. This heat can be used for hot water supply, object heating, cold production, technological purposes,
Single electric power - from 50 kW to 2 MW (more can be ordered). The coefficient of heat production in relation to electricity is from 1.4 at low capacities to 1.0 at large ones. Coefficient of obtaining cold in relation to heat - 0.7-0.5 Volume of capital investments - - rubles per kW of installed capacity. Payback period - 2-4 years (depends on the load of the equipment, with round-the-clock and maximum load the payback is faster) after-sales service Specific consumption gas to produce 1 kW of electricity - 0.3-0.4 cubic meters Turnkey project implementation period - 6-8 months Some technical and economic indicators of the use of TGU
Description:
With the full use of the generated electrical and thermal energy, high economic system indicators, and high energy efficiency provides, in turn, a reduction in the payback period for funds invested in equipment.
Joint production of heat and electricity
Cogeneration systems for heat and power: Balancing the ratio of produced heat and power
A. Abedin, Member of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE)
In the described cogeneration systems, the primary fuel is consumed for the simultaneous production of electrical or mechanical energy (power) and useful thermal energy. In this process, it is essential that the same fuel works “twice”, which ensures high energy efficiency of the systems.
With the full use of the generated electrical and thermal energy, high economic indicators of the system are achieved, and high energy efficiency ensures, in turn, a reduction in the payback period for funds invested in equipment.
The configuration of the system of joint production (cogeneration) of heat and electricity is determined by the extent to which the actual heat and electricity loads correspond to the generation of heat and electricity. If there is a market ready to consume excess heat or electricity, balancing the ratio of heat and electricity is not critical for the system.
For example, if electricity can be consumed (under acceptable conditions), then the basis for the operation of the cogeneration system is the need for local thermal energy (the system is designed to provide a heat load). Excess electricity can be sold, and its shortage can be compensated by purchases from other sources. As a result, high energy efficiency is ensured, and the actual ratio of heat and electricity generation for power plant meets the needs of the installation site.
As an example of the effective ratio of thermal and electrical power, consider a steam boiler that produces 4,540 kg of steam per hour, supplied at a pressure of about 8 bar, and consumes 4,400 kW of flue gas energy for this (with an average boiler efficiency of 75%). With the same amount of fuel gas energy consumed in a standard 1.2 MW gas turbine, required amount steam by recovering waste heat. As a result, about 1,100 kW of electricity can be generated "without spending" fuel. This is an example of a very good heat-to-power ratio, thanks to which the system has an attractive economic performance.
Imagine now an absorption chiller serving an air conditioning system with the same steam requirements. During part load operation, the same gas turbine generates electricity in an inefficient manner (usually). In such a system, the waste heat is not fully utilized, unless there is some other consumer of this heat on site. Thus, if the system is operated at partial load for a long time, its economic performance is not good.
The designer of the cogeneration system must decide difficult tasks ensuring the optimal ratio of thermal and electrical capacities, also taking into account daily and seasonal changes in this ratio. Next, typical methods for balancing the ratio of heat and electricity generation are considered.
Method I: use of gas turbines and generators with gas engines
Let's compare the configurations of a gas turbine power plant with a high ratio of thermal and electrical capacity and installations with internal combustion gas engines (gas engine) with a low ratio of thermal and electrical power. As will be shown below, depending on the energy loads of the facility, both gas turbine and gas engine installations can be appropriate.
Example A. Normally, in a building with central air conditioning at peak design conditions, there is a high demand for cold, which requires a large number of heat energy if the absorption chillers are operated with co-generated waste heat.
Let's say that at peak demand, the cooling demand in the building is 1,760 kW and about 1,100 kW of electrical power.
The gas turbine plant can operate with high cogeneration efficiency as follows:
1. Performance parameters of the gas turbine at 35 °C: 1200 kW of electric power at 5340 kW of flue gas energy input (22.5% electricity generation), steam output 7 kg/s at 540 °C.
2. Under the conditions of example A, a waste heat boiler provides a single-stage absorption chiller with approximately 2,990 kW of heat. With thermal energy losses of 7% (for radiation and losses in pipes with hot water), to ensure the required refrigeration capacity of the absorption chiller, the boiler supplies it with hot water at a temperature of 121 °C.
3. The ratio of thermal and electrical power (amount of thermal energy in British units MBtu/h per 1 kWh ) in example A is 8.5 (10 200 / 1 200).
Example B. For the same building as in example A, consuming only 750 kW of electricity and 616 kW of "cold" for air conditioning when operating in partial load mode, the ratio of thermal and electrical power is determined by the following factors:
1. Performance parameters of a gas engine power plant at 25 °C: 750 kW of electric power at 2,000 kW of flue gas energy input (electricity generation 37.5%), utilization of waste heat of cooling water in the amount of 100 kW from the aftercooler circuit and utilization of exhaust gas heat engine in the amount of 500 kW.
2. With a total of 959 kW of heat recovered, it is possible to produce about 616 kW of cold using a single-stage absorption chiller when hot water is supplied to it at a temperature of 90 ° C.
3. The ratio of thermal and electrical power (the amount of thermal energy in units of MBtu / h per 1 kW / h) in example B is 4.4 (3 300 / 750).
The ratio of thermal and electrical power changes from 8.5 (for a gas turbine plant) at peak loads to 4.4 for a gas engine plant in partial load mode. A rational choice of the configuration of the cogeneration system allows to achieve the optimal load ratio and ensure the highest efficiency of the joint production of heat and electricity.
Method 2: Using Hybrid Chillers
A hybrid chiller is needed to balance heat and power generation in cogeneration power plants that provide heat recovery for central air conditioning systems.
During periods of relatively low power demand (when there is little recoverable heat available for the absorption chiller), an electric chiller helps to balance this ratio by increasing electrical load while increasing the amount of waste heat to increase the efficiency of cogeneration.
Method 3: using a thermal energy storage
Accumulators (accumulators) of thermal energy are used as in cooling systems and in heating systems. The use of accumulative storage tanks using hot water (temperature from 85 to 90 ° C) can "save" the existing "waste" heat. The system can also be designed to use hot water with a temperature above 100 °C (at elevated pressure).
Since it is not economically viable to “storage” electricity (especially for small power plants of cogeneration of heat and electricity) to ensure high efficiency heat generation, in such installations, excess heat energy must be stored to meet the demand for electricity.
With the full use of the heat of waste gases for the joint production of heat and electricity intended for central systems air conditioning, it is essential that the heat-using chillers operate at maximum capacity and any excess cooling capacity is stored as chilled water stored in storage tanks.
This can be done using existing water tanks (e.g. designed for a fire extinguishing system) or specially made tanks.
Thermal energy storage can be used to store hot water with a temperature in the range of 85 to 90 °C (water with such a temperature is intensively used, for example, in textile factories). Because the CHP plant produces hot water continuously, hot water can be stored in tanks for industrial use.
The figure shows a simplified diagram of the piping system of a hot water production and storage plant, which is part of a combined heat and power plant that uses a generator driven by a 900 kW turbocharged gas engine at a rotation speed of 1,000 rpm. The diagram does not show all the necessary control valves and instruments for safe and economical operation.
Method 4: Inlet Air Conditioning with a Gas Turbine
EXAMPLE A Gas turbine inlet air conditioning is a technology that can be used in gas turbine generator sets to balance the ratio of heat and power. This technology uses inlet air cooling to increase capacity at peak loads in summer (using either thermal energy storage or in-line chillers using waste heat) or inlet air heating to increase cogeneration efficiency at part load, especially in winter (extra heat is produced). energy per 1 kW of electricity).
Cooling the inlet air increases the performance and efficiency of the gas turbine generator. It is widely used in co-generation systems that use waste heat to supply chilled water from a centralized location.
In such systems, there is or is no storage of thermal energy. This design ensures that the gas turbine generators operate according to the required loads, since the increase in power generation due to the cooling of the inlet air also leads to an increase in the waste heat supplied to the absorption chillers.
Under partial load conditions, the use of a gas turbine with inlet cooling coils is not advantageous, as the additional pressure drop across the (now redundant) cooling coil causes an increase in heat output (increased fuel consumption). In cogeneration plants, part load efficiency can be improved, as shown in the table, by using a conventional gas turbine rated at 1,200 kW used in a cogeneration plant producing pressurized steam used for industrial purposes. 3 bars.
When operating at 40% of maximum load, gas turbine inlet air preheating (limited by plant design) can be used to balance the heat to power ratio, as reduced gas turbine efficiency results in higher available waste heat and, as a result, higher overall efficiency cogeneration. It is stated that the efficiency of the joint production of heat and electricity increases by more than 15% if, under partial load conditions, the inlet air is heated from 15 to 60 °C. Most gas turbine manufacturers can provide performance data for air temperatures up to 60°C. Before designing a system with this capability, the inlet air heating limits should be checked with the gas turbine manufacturer.
EXAMPLE B To increase "waste" heat generation in high temperature, oxygen-enriched gas turbine exhaust gases, post-combustion in the waste heat stream is applied. Large quantity heat means a higher ratio of heat and power, improving the economics of the process of co-production of heat and power.
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Conclusion
Combined heat and power systems operate efficiently if all or most of the electricity and heat is used.
In real conditions, the load varies, so for most systems it is necessary to balance the ratio of produced thermal and electrical power, ensuring efficient and economical operation of the cogeneration plant.
Heat-to-power balancing systems should be adopted in co-generation plants from the outset to ensure optimal use of the output electrical and thermal power and thereby reduce fuel costs, as well as to improve economic indicators systems.
Translated with abbreviations from ASHRAE magazine.
Translation from English L. I. Baranova.
