Combined production of heat, electricity and refrigeration: cogeneration and trigeneration for an industrial facility

Industrial facilities depend on the uninterrupted supply of thermal, electrical, and sometimes refrigeration energy to production facilities. The source can be distribution networks, whose operators set energy tariffs: as a rule, they are inflated relative to economically justified ones. An alternative option is an autonomous generation facility: a boiler house or a mini-thermal power plant.

Cogeneration and trigeneration are attracting the attention of industrialists for the following reasons:

• high energy efficiency;
• obtaining electrical and refrigeration energy at cost;
• development of lean production, which implies minimal losses of raw materials in the production process;
• high level of environmental friendliness;
• creating conditions for the dynamic development of technologies, increasing the energy intensity of manufactured products;
• increasing the overall economic potential and investment attractiveness of the industrial facility;
• no need to interact with distribution organizations, constantly increase energy supply budgets due to tariff increases;
• the ability to regulate the volumes of generated and consumed energy online.

The decision to use cogeneration or trigeneration technology is made on the basis of a detailed feasibility study and approval of a comprehensive engineering support scheme for the facility.

Cogeneration

Cogeneration – combined production of thermal and electrical energy.

Cogeneration plants (cogenerators) are used in the industry of small distributed generation (mini-CHP, mini-CHP) in local energy systems. This development is explained by a number of factors, the main of which are the proximity of the location to the consumer, independence from external supplies of energy resources, and increased reliability of energy supply. In small-scale distributed energy, cogeneration units based on gas piston engines and gas turbine units are most widespread.

The principle of operation of a cogeneration plant based on a gas piston unit: during the combustion of fuel, mechanical energy is generated, transmitted through a single shaft to the generator and converted into electrical energy of standard quality parameters.

When an internal combustion engine operates, a large amount of heat is released, which can be recovered using special equipment and then used. At the same time, no additional amount of fuel is consumed to obtain this energy - this product is a by-product in the technological process of generating electrical energy.

Main sources of associated heat during operation of a gas piston power plant:

• heat of cooling water (“jacket” of engine cooling);
• heat of exhaust gases (exhaust gases).

These sources can be used to obtain thermal energy (heat recovery), thereby regulating the temperature and volume of energy resource production, as well as the volume of installed auxiliary equipment.

The heat recovery system from cogeneration plants makes it possible to obtain associated thermal energy of the required parameters using heat exchangers and waste heat boilers, which remove heat from heated parts and environments. The generated thermal energy is supplied to the existing heat supply system of the enterprise (cogeneration). If associated heat is not used, thermal energy is discharged into the atmosphere.

Operation diagram of a cogeneration plant

When a gas piston installation operates in cogeneration mode, the generation of electrical energy is the priority task of the installation. The generation (utilization) of thermal energy is proportional to the degree of load of the machine (the amount of electricity generated). When the thermal power generated by a power plant exceeds the power consumed, the unused or excess part of the associated heat of gas piston units is discharged into the atmosphere. In the opposite situation, when there is a shortage of heat recovered from a gas piston unit, when the required electrical load is less than the thermal load, the problem of heat shortage is solved by installing additional hot water or steam boilers in parallel with the heat recovery system of the cogeneration unit.

Comparison of cogeneration efficiency with the traditional algorithm for obtaining thermal and electrical energy

The cogeneration mode is the most economically feasible way to generate energy resources, increasing the overall efficiency of cogeneration plants by up to 90%.

Trigeneration

Trigeneration is a process in which part of the thermal energy generated during the operation of a gas piston unit is used to generate cold, which is used for the technological needs of the enterprise and for air conditioning premises.

Working principle of trigeneration

Combustible gas of the required parameters is supplied to the gas piston engine. During the combustion of fuel, mechanical energy is generated, which is transmitted through a single shaft to the generator and converted into electrical energy of standard quality parameters.

When an internal combustion engine operates, a large amount of heat is released, which can be recovered using special equipment and then used. At the same time, no additional amount of fuel is consumed to obtain this energy - this product is a by-product in the technological process of generating electrical energy.

The heat recovery system from gas piston units makes it possible to obtain associated thermal energy of the required parameters using heat exchangers and waste heat boilers, which remove heat from heated parts and environments. The generated thermal energy is supplied to the existing heat supply system of the enterprise (cogeneration). In addition to the cogeneration mode with the simultaneous production of two energy resources, a gas piston installation can, using specially installed equipment, organize a trigeneration mode - the simultaneous production of three energy resources - electricity, heat and cold.

Operating principle of a trigeneration plant

Application areas of trigeneration

Trigeneration is used at various facilities where there is a need for electricity, heat and cold:

• at industrial enterprises;
• in agriculture;
• in the service sector;
• in hotels;
• trade and administrative centers;
• business centers;
• hospitals, resorts and medical institutions;
• swimming pools, sports centers;
• housing facilities;
• airports;
• refrigerated warehouses;
• food storage bases

In a number of applications, recovered heat is used in low-temperature industrial processes such as drying, tanning, food processing, space heating and water heating in buildings, and space cooling using absorption chillers.

Trigeneration projects have a number of advantages. The main ones are the following:

• Economical: surplus thermal energy, which has the lowest cost, is used to produce cold
• Adding a trigeneration cycle to a cogeneration plant increases the unit's load factor throughout the year, which reduces its payback period and increases the efficiency of the investment
• Operating a trigeneration unit is almost two times cheaper than operating compression refrigeration machines
• The absorption system operates almost silently. The noise level at Q0 1500 kW does not exceed 65 dBa at a distance of 1 meter
• Durability: due to the absence of moving parts and their wear in the refrigeration unit, ABKhM has an extended service life before major repairs - 20 years
• Trigeneration plants meet the requirements of international protocols for the protection of the ozone layer of the atmosphere, since refrigerants are not used in absorption machines

Energia Plus engineers perform the entire cycle of design, construction and installation work of boiler houses and mini-thermal power plants. He also performs the functions of a general designer and technical customer.

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