Cogeneration - and systems for it - are described, starting with fundamentals and definitions and extending to benefits, uses, operation and applications. Although the term cogeneration can in general refer to any process that generates two (and sometimes more than two) products, we typically in this book restrict our use of the term cogeneration to its most common meaning: the simultaneous production in a single process of electricity and heat (typically in the form of steam and/or hot water). In such instances, cogeneration is often referred to as CHP. For clarity, cogeneration is contrasted with thermal electrical generation, pointing out similarities and differences, and highlighting how cogeneration is a logical extension of many systems for thermal electricity generation. The trade-offbetween thermal and electrical outputs of cogeneration is discussed, demonstrating how electrical output decreases as thermal output (and the quality of the thermal output as measured by its temperature) increases. The interface between cogeneration and energy storage is also discussed, where the storage can apply to the thermal and/or electrical product of cogeneration. A general cogeneration system model, suitable for thermodynamic and engineering assessments, is provided that is sufficiently flexible and robust to model most cogeneration system options. Energy and exergy balances for the general cogeneration system model are given and illustrated. The advantages and applications of cogeneration are given, and the main categories of heat demands that can normally be satisfied with cogeneration are described: residential, commercial and institutional processes (e.g., heating of air and water) and industrial processes (e.g., drying, heating, boiling). The selection of the size and type of a cogeneration system to match as optimally as possible the thermal and electrical demands is discussed, as are matching schemes that can be used. Systems for thermal electricity generation are described, including steam-turbine, gas-turbine, combined-cycle, reciprocating engine and renewable energy-based thermal electricity-generation technologies. Cogeneration systems are also detailed, and it is shown how the types of cogeneration systems available parallel to the types of systems for thermal electricity generation.

Chapter Contents:

• Overview
• 3.1 Introduction
• 3.2 Fundamentals
• 3.3 Cogeneration and related energy systems
• 3.3.1 Cogeneration definition
• 3.3.2 Cogeneration vs. thermal electrical generation
• 3.3.3 Cogeneration benefits
• 3.3.4 Cogeneration uses and operation
• 3.3.5 Cogeneration applications
• 3.3.6 Cogeneration and energy storage
• 3.4 General cogeneration system model
• 3.5 Description of a general cogeneration system
• 3.5.1 Energy and exergy balances
• 3.5.2 Efficiencies
• 3.5.3 Trade-off between cogeneration electrical and thermal outputs
• 3.6 Systems for electricity generation and cogeneration
• 3.6.1 Thermal electricity-generation systems
• 3.6.1.1 Steam-turbine electricity-generation systems
• 3.6.1.2 Gas-turbine electricity-generation systems
• 3.6.1.3 Combined-cycle electricity-generation systems
• 3.6.1.4 Reciprocating engines
• 3.6.1.5 Fuel cells
• 3.6.1.6 Other systems
• 3.6.2 Cogeneration systems
• 3.6.2.1 Steam-turbine cogeneration systems
• 3.6.2.2 Gas-turbine cogeneration systems
• 3.6.2.3 Combined-cycle cogeneration systems
• 3.6.2.4 Reciprocating engine-based cogeneration systems
• 3.6.2.5 Fuel cells
• 3.6.2.6 Solar cogeneration
• 3.6.2.7 Micro-cogeneration
• 3.6.2.8 Other systems
• 3.7 Case study: reciprocating engine heat and power generation for wastewater treatment
• 3.7.1 Cogeneration system
• 3.7.2 Anaerobic digesters
• 3.7.3 Biogas conditioning
• 3.7.4 Biogas storage tank
• 3.7.5 System benefits
• 3.8 Closure

Inspec keywords: cogeneration

Other keywords: steam-turbine; thermal electricity generation; combined-cycle; cogeneration systems; CHP; exergy balances; reciprocating engine; energy balances; gas-turbine; renewable energy-based thermal electricity-generation

Subjects: Thermal power stations and plants