Additional CHP Equipment
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Addition of Gas
If sufficient gas is not available, the CHP automatically reduces its output to match the minimum gas quantity available. However, in order to be able to continue operation of the CHP at high load and optimally supply the property with electricity and heat, a 2G gas mixing line can be installed. This line mixes the lean gas from sewage treatment plants, landfills or mines with up to 100% natural gas.
However, it is also possible that there is a sufficient quantity of lean gas, but the quality is inadequate. In this case, the 2G gas mixing line can add natural gas to the lean gas in order to assure constant operation of the CHP.
The addition of all types of gas always takes place in compliance with applicable regulations for exhaust gas emissions. With this opportunity it is possible to design the gas storage smaller and act more flexible regarding gas production.
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Temperature Levels
2G plants are configured by standard for a supply temperature of 90 °C and a return temperature of 70 °C. Some customer-specific circumstances necessitate a deviation from this, which 2G can easily accommodate based on extensive experience.
Variants heat extraction standard biogas 70/90°C and heat extraction natural gas 70/90°C are also required for older heat networks, absorption cooling systems and applications with process heat. When plants use steam generators for water preheating, etc., variant heat extraction 78/95°C is necessary.
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Additional Heat Applications
Use waste heat efficiently
In general hot water at a temperature of 90 °C is provided by the 2G plant. The waste heat can be used in the following ways:
Hot water systems
- High temperature level with increased system pressure
- Frequent use for the heat supply of a district heating plant or for process heat in industry
Thermal oil heat exchanger
- Is used instead of the standard heat exchanger
- The heat carrier is thermal oil, which can provide a high temperature level (up to 350 °C) in a quasi-pressureless system
- Good cost/benefit ratio
- Frequently used for biogas treatment plants
Air heat exchanger
- Air is heated instead of water
- Typical application: Drying of textiles
- Space-consuming
Heat pump
- Generates ample heat from little electric current in order to provide additional heat to the district heating network, etc.
- The average difference between the head reduction outlet and heat source inlet should not exceed 50 K
- A suitable compressor concept is required that takes the thermal load into consideration
- Additional increase in efficiency of the 2G plant is possible, e.g. using the waste heat of the CHP as a heat source for a heat pump
Calorific value heat exchanger
- Installation of a second heat exchanger after the first one or direct configuration of calorific value heat exchanger
- Additional energy is extracted from the exhaust gas in the form of heat and efficiency increases
- Requirement: low return temperatures (e. g. in swimming pools or heat networks)
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Heat Storage Distribution
The heat generated by 2G plants is often supplied to multiple consumers or the heat should be stored. 2G also provides a suitable system for distribution of the heat.
Distribute heat as needed or store it
With a heating circuit distributor, a fermenter dryer can be operated with the supplied heat in parallel to the biogas plant. Or a natural gas CHP supplies a heating and cold absorption system.
Heating circuit distributor
The heating circuit distributor comprises a hydraulic switch that separates the supply circuit and consumer circuits and a distributor manifold that distributes the thermal output to the respective consumer circuits. The main components of the heating circuit distributor is a 3-way mixer that divides the process regulating groups into the primary circuit (coming from the heating circuit distributor) and consumer-side secondary circuits. Depending on the heat requirement, the 3-way mixer adds more or less hot water to the secondary circuits, which are equipped with a heat pump in order to generate constant volume flows.
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Data Interfaces
Transmit data simply, reliably and securely
Interfaces with various bus systems can be offered for connection to the CHP plant control unit. The following variants are available:
- Ethernet IP
- Modbus RTU
- Modbus TCP
- Profibus DP
The data that can be exchanged can be determined based on the corresponding interface lists. They are provided as technical information. Examples include start/stop requirements ("TI"), various temperatures and pressures. Extensive data can be exchanged with minimal wiring thanks to the data interface. An additional advantage is that analog signals requiring elaborate processing can be transmitted reliably. This data can, for instance, be read in a customerspecific control unit in order to establish a visualization or to communicate status messages and monitor the plant based on the data.
In addition to the interfaces mentioned above, other data interfaces are available on request.
Hardware interfaces can also be provided along with the bus interfaces. However, this is not as comprehensive as a bus interface and only exchanges the most important signals. Digital and analog values are exchanged via terminals.
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Partial load and zero reference control
2G plants are increasingly operated on a requirement basis – without the need to switch off the CHP. A variant of requirement-based operation is zero reference control: Only the amount of current that is actually required by the consumer is produced and not fed into the public mains. In these cases, the 2G plant can react flexibly and the output can be adapted automatically to the local circumstances.
All plants can be operated with a partial load of up to 50%, particularly with temporary limitations. 50% partial load 2G plants which run on natural gas or purified lean gas may be run at 50% rated load on a long-term basis. In the case of purified lean gas, the sulfur content must be recorded on-site on the plant control unit for the purpose of long-term measurement.
2G plants which run on unpurified lean gas may be run at 75% rated load on a long-term basis. Operation at less than 75% of the rated load may only be conducted for a certain amount of time. After each interval at under 75% rated load, the 2G plant must run at an output of over 75% rated load for defined minimum duration so that the condensate in the exhaust tract can be discharged.
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Mains back up and isolate operation
In some regions there are supply networks that cannot provide uninterrupted electric current or in which it is not even available. In these cases a 2G plant in isolated operation can be a remedy for electric current supply. With a "black start", the 2G plant can even be started without external auxiliary energy and an isolated network can be established for independent supply. This works for individual 2G plants as well as for multiple engines connected in parallel.
Isolated operation cannot be equated to emergency power operation. In this case, there are requirements based on standards that necessitate the re-establishment of the power supply in case of a power failure – e.g. in hospitals. However, a 2G plant guarantees numerous possibilities for assuring independent supply in case of a mains failure.
Manual isolated operation
The simplest variant is manual isolated operation. As soon as the mains power fails, the CHP plant and customer system switch over to isolated operation. Now the engine can be restarted and the loads are activated successively. With a return of the mains power supply, the machine must be shut down again. The switchover of the CHP plant and the customer system is followed by the switchover back to mains-parallel operation.
Automatic isolated operation with back synchronization
The basic process in the case of a mains failure and the subsequent start-up of the 2G plant is the same as for manual isolated operation. However, when the mains returns, a reconnection to the public mains can take place with the help of a superordinate on-site coupling switch. The 2G plant can be back-synchronized with the mains once a secure supply is provided.
Automatic isolated operation with load transfer and back synchronization
The entire load can be assumed by the 2G plant in case of a main failure without the necessity of a shut-down. The back synchronization takes place as described above. In this variant an additional zero reference control can be installed (see page 30). Using this control, the CHP plant generates as much energy as is actually required.
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Mains Starter Device
If a mains starter device is used instead of a starter battery, a 2G plant can be started in a more environmentally-friendly manner, with reduced maintenance and better starting behavior, because a higher start-up speed is reached, which enables a secure engine start at colder environmental temperatures, in particular.
Energy for startup from the mains
2G plants are started with a starter that is normally supplied with energy by starter batteries. A common alternative is the mains starter device designed by 2G. It comprises a transformer and an inverter and is adapted to the output of the starter. The mains starter device converts energy from the mains so that the starter can start. The alternating current drawn from the mains by the starter device is inverted in order to provide the direct current required for the starter. Normal starter batteries can be omitted.
Optimized starting process
Unlike batteries, the mains starter device does not have to be replaced or maintained in regular intervals. The starting process can also be optimized with a higher start-up speed. The use of the mains starter device is also beneficial if adequate battery ventilation in accordance with EN 50272 cannot be provided. Use of the mains starter device is possible for all 2G plants with synchronous generators.
The 2G mains starter device is maintenance-free, does not form gases and is free from charge-current monitoring. If isolated operation is desired, the use of starter batteries is necessary, because they can also be used independently of the mains to start the engine.
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Warm Country Version
Worldwide installation of 2G plants necessitates adaptation to climate conditions. With a few modifications, 2G plants can also be ideally equipped for locations with a very warm climate.
Full output even in warm climates
In Germany, there are only a few days each year that the temperature outside is above 40 °C. By contrast, countries in tropical climates have entirely different conditions. If it becomes too hot in the inside of the container, the electronics can be damaged. Consequences: The CHP automatically reduced its power or performs an emergency shut-down. Apart from any potentially damaged components, these two scenarios affect the efficiency of the CHP.
In order to prevent overheating of the 2G plant, 2G offers the following components with the warm country version:
- Switch cabinet with air conditioning system
- Combustion air cooling (so that no warm air enters the container interior)
- Larger mixture and emergency cooler (higher cooling capacity)
With these adaptations, as shown in the drawing to the left, full output can also be provided at high temperatures and an emergency shut-down can be prevented.
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Exhaust Gas Post Treatment
Reduce harmful substances
Like most technical combustion processes, small amounts of harmful substances are also created in the combined heat and CHP plant and must be reduced. Oxidation catalytic converters, SCR catalytic converters and post-combustion systems can assist the reduction of emissions and compliance with applicable regulations.
Oxidation catalytic converters
The oxidation catalytic converter installed in the exhaust tract of the 2G plant assures a reduction of carbon monoxide and formaldehyde emissions. A chemical reaction converts the undesired substances into inert components. The catalytic converters can be designed depending on the required target values so that applicable regulations can always be fulfilled.
SCR catalytic converter
For reduction of nitrogen oxide emissions, with certain requirements, the use of a so-called SCR catalytic converter is necessary, because limits are set within the engine and a simple oxidation catalytic converter cannot achieve the desired effect. With the "selective catalytic reaction", a urea mixture is added to the exhaust gas upstream from the catalytic converter. The nitrogen oxide is converted into harmless substances in the subsequent reaction. Therefore, the highest requirements on the exhaust gas quality can be fulfilled. Basically, a suitable combustion gas quality must be assured for the use of catalytic converters, particularly in lean gas operation. Therefore gas treatment is often necessary.
Post-combustion system
To a lesser extent, hydrocarbons contained in exhaust gas can be removed with the use of a post-combustion system. Depending on the version, these systems can be operated autothermically in stationary operation after the start-up phase so that no additional fuel is required.
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Variants of Oil Supply
Reduce expenses for oil changes and supply
Oil is required in an engine for friction-free interaction of the moving parts and a fine seal of individual components. To protect the engine, it is important to use a high-quality oil. Periphery equipment that are well-matched simplify the entire CHP operation and extend the service life.
The engine oil is an important operating material for the 2G plant and must be replaced regularly. In order to reduce the related expenses, a good oil supply is necessary. 2G offers periphery that meets the requirements. The following possibilities can be realized:
Lubrication oil supply consisting of:
- 1 x 1000 l fresh and 1 x 1000 l used oil tank, double-walled with tank content indicator
- Used oil tank overfill protection device
- Lubricating oil pump
Pump lance system comprising
- 2 x 200 l drums
- Lubricating oil pump
- Oil collection trough
Lubricating oil container
- Dimensions: 3000 mm x 2500 mm x 2500 mm (WLH)
- Storage capacity 2 x 1000 l tanks
- 1000 l collection volume
Automatic oil refilling unit
In order to minimize the cost of oil supply, 2G offers the option of an automatic oil refilling unit. This system, including oil storage tank with sight glass for visual oil level control guarantees the optimal oil level in the engine over an extended time.
In the filius series the oil reserve tank is not installed on the frame; it is arranged externally.
In addition, an oil volume expansion can increase the volume of oil circulating in the engine system. The aim is to extend the oil change interval and save on expenses due to downtimes and to increase the operating time of the 2G plant.
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Measurement instrumentation
With the use of various meters, both the operator and the 2G control center have a continuous overview of the plant and can react to the slightest changes.
In order to register a 2G plant to the German Federal Office of Economics and Export Controls, various meter statuses must be recorded. This is important for the mains operator to know how much electricity has been fed into the public mains or how much natural gas was drawn. Some specifications that the 2G app can visualize are also important to the customer. Therefore, the plant proprietor always has the latest operating statuses of their plant on hand.
Gas meter
- Measurement of the amount of gas drawn
- With MID certification (is frequently desired by customs for energy tax reimbursement)
- Calibrated with calibrating report, specification in operating and standard cubic meters and M-bus readout (used in natural gas applications)
- Uncalibrated (use in biogas applications, not mandatory)
Electric current meter
- Measurement of the amount of electricity fed into the mains
- If applicable, the energy supply company requires a registered output measurement with installation of their own current meter
- An electric current meter is provided by the energy supply company. In natural gas applications, additional electric current meters are normally installed (one meter for recording of the total output and another meter for the measurement of internal current consumption)
Heat quantity meter
- Measurement of delivered heat (e.g. to a swimming pool or a hospital)
In addition to the meters mentioned above, sensors for the protection of persons can be installed. A gas warning system detects escaping gas and a CO2 sensor measures the carbon monoxide concentration in the CHP plant room.
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Contact us for further information about CHP equipment specifically designed to match a 2G system.
