| Condensing Steam Turbine Generator | High-pressure steam expands through multiple turbine stages to a low-pressure condenser. The condenser maintains vacuum, increasing the expansion ratio and converting more steam energy into electrical power. | Approximately 40–65 bar(a)
380–450°C | Approximately 0.05–0.15 bar(a)
Saturated or slightly superheated exhaust steam | Electricity-focused WTE plants where export power is the primary energy product and there is limited demand for usable process heat. | High electrical output for a given steam flow; stable operation; suitable for grid-connected base-load generation; well-established water-steam-cycle technology. | Requires a condenser and cooling system; lower total energy utilization when no heat customer exists; cooling-water or air-cooled-condenser performance strongly affects output. |
| Extraction-Condensing Steam Turbine Generator | Steam is extracted from one or more intermediate turbine stages for district heating, process steam, deaerator service, or feedwater heating. The remaining steam continues to the condenser. | Approximately 40–65 bar(a)
380–450°C | Controlled extraction commonly about 2–20 bar(a); final exhaust typically 0.05–0.15 bar(a) | WTE plants requiring both electricity and flexible heat or steam supply, especially facilities with seasonal or variable heat demand. | Flexible balance between power production and useful heat; can supply multiple pressure levels; maintains condensing capability when heat demand falls. | More complex control and protection systems; extraction reduces electrical output; turbine design must accommodate changing extraction flow and pressure. |
| Back-Pressure Steam Turbine Generator | Steam expands through the turbine and exits at a controlled pressure above atmospheric pressure. Exhaust steam is directly used for heating or industrial processes rather than condensed for maximum power generation. | Approximately 40–65 bar(a)
380–450°C | Commonly about 2–10 bar(a), depending on the heat user | WTE facilities located near a dependable district-heating network or continuous industrial steam customer. | Simple and efficient combined heat-and-power arrangement; reduced condenser duty; high overall fuel-energy utilization when heat demand is reliable. | Electrical output depends on the required exhaust pressure; limited flexibility during low heat demand; unsuitable when there is no stable steam or heat off-taker. |
| Controlled-Extraction Back-Pressure Turbine | Steam is extracted at a controlled intermediate pressure, while the remaining steam expands to a higher-pressure back-pressure exhaust for another heat user or process stage. | Approximately 40–65 bar(a)
380–450°C | Extraction commonly about 3–15 bar(a); final exhaust commonly about 1.5–5 bar(a) | WTE sites serving two or more heat users with different pressure requirements. | Supports multi-level heat supply; can achieve high combined heat-and-power utilization; useful for integrated municipal and industrial energy systems. | Higher mechanical and control complexity; operating range must be checked carefully against minimum steam flow, heat demand, and turbine stability limits. |
| Single-Casing or Compact Small Steam Turbine | A compact turbine expands a relatively modest steam flow through a small number of stages and drives a generator directly or through a speed-reduction gearbox. | Approximately 20–45 bar(a)
300–420°C | Condensing: about 0.08–0.20 bar(a)
Back-pressure: about 2–10 bar(a) | Small WTE plants, sewage-sludge incineration facilities, or sites with limited steam production and restricted installation space. | Compact footprint; lower initial equipment complexity; suitable for modest electrical capacities; simpler installation and maintenance planning. | Lower efficiency at very small scale; greater sensitivity to steam-flow changes; auxiliary power, standby requirements, and minimum-load performance should be evaluated. |
| Reheat Condensing Steam Turbine | Steam expands through a high-pressure turbine section, returns to the boiler or reheater for temperature recovery, and then expands through intermediate- and low-pressure stages. | Main steam commonly about 60–100 bar(a)
450–540°C | Typically about 0.05–0.12 bar(a) at the condenser | Large WTE plants with high steam flow, high annual operating hours, and sufficient boiler and materials capability for advanced steam conditions. | Can improve cycle efficiency and reduce moisture in the final turbine stages; appropriate for large, electricity-oriented installations. | Higher capital cost and system complexity; WTE flue-gas corrosion, high-temperature materials, boiler availability, and maintenance requirements can limit economic benefit. |
| Air-Cooled Condensing Turbine Generator | The turbine exhaust is condensed in an air-cooled condenser. Ambient air removes heat through finned tubes, eliminating the need for a large continuous cooling-water supply. | Commonly about 40–65 bar(a)
380–450°C | Approximately 0.08–0.25 bar(a), depending on ambient temperature and condenser design | Water-constrained, arid, remote, or land-based WTE sites where wet cooling is impractical or environmentally restricted. | Very low process-water consumption; reduced dependence on cooling-water infrastructure; easier siting where water availability is limited. | Higher back pressure during hot weather; larger footprint and fan power demand; electrical output can vary significantly with ambient temperature and wind conditions. |
| Water-Cooled Condensing Turbine Generator | Turbine exhaust steam is condensed using circulating cooling water in a surface condenser. Heat is rejected through a cooling tower, river, seawater system, or other approved heat sink. | Commonly about 40–65 bar(a)
380–450°C | Approximately 0.05–0.12 bar(a), subject to cooling-water temperature and condenser cleanliness | WTE plants with reliable cooling-water availability and sufficient space or permits for cooling towers and water-treatment systems. | Generally lower condensing pressure than air cooling; strong hot-weather performance; compact condenser arrangement for suitable sites. | Requires water intake, treatment, blowdown management, and corrosion control; environmental permits and water availability may be decisive. |
| Synchronous Generator Package | The steam turbine drives a synchronous generator whose rotor speed is synchronized with the grid frequency. Typical two-pole or four-pole designs operate at 3,000 or 1,500 rpm on a 50 Hz grid and 3,600 or 1,800 rpm on a 60 Hz grid. | Generator voltage commonly about 3.3–15 kV
Frequency: 50 or 60 Hz | Power factor commonly designed around 0.8–0.95, depending on the grid code and excitation system | Grid-connected WTE projects requiring voltage control, fault-ride-through capability, and compliance with utility interconnection requirements. | Can provide reactive-power support; suitable for stable parallel operation; widely used for medium- and large-scale turbine-generator sets. | Requires excitation, synchronization, protection, and grid-code compliance systems; generator selection must match turbine speed, output, voltage, and short-circuit requirements. |
| Induction Generator Package | The turbine drives an asynchronous generator that obtains magnetizing current from the grid or from power-electronic equipment. It normally operates with a small slip relative to synchronous speed. | Commonly used for smaller output ranges
Voltage and frequency selected for the local grid | Typically requires grid support for reactive power unless capacitor banks or converters are installed | Small, stable-output WTE applications with a strong grid connection and limited requirements for independent voltage regulation. | Simple construction; generally robust; potentially lower package complexity for small units. | Limited reactive-power and islanding capability; less suitable for weak grids, independent operation, or applications requiring precise voltage control. |
| Modular Multi-Unit Turbine-Generator System | Several smaller turbine-generator sets operate in parallel. Units can be started, stopped, or operated at different loads to match changing steam production from multiple waste-processing lines. | Each unit is designed for its own steam flow and pressure
Common WTE steam conditions remain project-specific | Condensing, extraction, or back-pressure operation can be arranged by module | Plants with multiple incinerator lines, fluctuating waste throughput, staged expansion, or a strong requirement for partial-load availability. | Better redundancy; flexible maintenance scheduling; improved matching of turbine capacity to changing steam flow; easier phased capacity expansion. | More balance-of-plant equipment, controls, valves, and maintenance points; total cost per kilowatt can be higher than a single optimized unit. |
