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On-Site Power and Heat by the Numbers

Carnot limits, engine and turbine cycles, steam turbines, waste heat and combined heat and power, worked through one laundry's energy plant

Judge on-site power and heat with engineering thermodynamics: Carnot limits, Otto, Diesel, Brayton and Rankine cycles, turbochargers, waste heat recovery and the cogeneration business case.

10 chapters · About 104 minutes · Free to read · Intermediate engineering thermodynamics

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KEVOS® LibraryENGINEERINGOn-Site Powerand Heat by theNumbersKEVOS® ORIGINAL BOOK10 CHAPTERS

About this book

Every proposal for on-site power arrives with a set of efficiencies: an electrical efficiency for the engine, a heat recovery figure, a utilisation factor and a payback period. The figures are often all true and still tell the buyer very little, because each is measured against a different basis and none says how much of the heat the site can actually use. This book gives an engineer the thermodynamics to rebuild those figures from first principles and decide for themselves.

It starts with the first law and the Carnot limit, then analyses the machines one at a time: compressors and turbines in steady flow, the Otto and Diesel cycles behind gas engines and standby generators, the Brayton cycle behind gas turbines and microturbines, and the Rankine cycle behind steam turbines. It then follows the heat that every engine rejects, finds how much of it is worth recovering, and finishes with cogeneration, where power and heat are judged together and turned into a business case.

It is for mechanical, process and energy engineers, plant managers, energy auditors and students who know the first law and the idea of specific heat and want to apply them to real equipment. It assumes algebra, powers and natural logarithms. Each chapter works one running case with real numbers, includes one plausible mistake and how it was found, links the KEVOS® tool that performs the chapter’s main calculation, and ends with an exercise and its worked answer.

The running case

Every chapter follows one fictional plant. This is an illustration. A commercial laundry in a regional Australian city washes, dries and irons linen for hotels and restaurants. It runs 16 hours a day, 300 days a year (4,800 hours), and is reviewing on-site generation before it replaces an ageing boiler.

  • Electricity: an average demand of 450 kW while the plant runs, never below 400 kW.
  • Steam: 550 kW at 10 bar gauge (184.1 °C) for the flatwork ironers and finishing, from a gas-fired boiler of 82% efficiency on the gas’s higher heating value.
  • Hot water: 350 kW for the tunnel washer, from a steam calorifier fed through a pressure-reducing valve at 2 bar gauge.
  • The proposal: a lean-burn gas engine generator taking 1,000 kW of fuel on the lower heating value, making 400 kW of electricity (390 kW net), with 230 kW of jacket-water heat at 90 °C and 0.64 kg/s of exhaust at 470 °C.
  • The alternatives: a recuperated microturbine, a back-pressure steam turbine in place of the pressure-reducing valve, and an organic Rankine cycle unit offered for the jacket water. The site already has a 500 kVA standby diesel generator.

The plant, its equipment, the measurements and every price are invented. None describes KEVOS® work or a real business. Surroundings are taken as 25 °C and 101.325 kPa throughout.

How to use the book

Read Chapters 1 and 2 first: they set out the energy balance, the Carnot limit and the steady-flow analysis that every later chapter uses. Chapters 3 to 5 deal with reciprocating engines, Chapters 6 and 7 with gas turbines and Chapter 8 with steam turbines; each group can be read on its own. Chapters 9 and 10 bring the heat and the money together and depend on the earlier figures for the gas engine.

The cycle chapters use the cold-air standard: air as an ideal gas with constant specific heats and reversible processes. It is a model for understanding and comparing, not for predicting a real machine’s output, and each chapter says where it departs from reality. Steam properties come from the IAPWS-IF97 formulation. Fuel is treated as methane for combustion calculations.

Source limits and professional responsibility

The laws and cycle formulas in this book are standard and exact within their stated assumptions. Equipment figures such as the engine’s efficiency, the turbocharger’s measurements and the microturbine’s component efficiencies are illustrations; real figures come from the manufacturer’s data at the actual operating conditions and from tests on site. Prices are illustrations, stated excluding GST.

Gas engines, turbines, boilers, pressure equipment, gas installations and generators connected to the electricity network carry serious hazards and are regulated in Australia. Their design, installation, connection, operation and maintenance are matters for competent engineers, licensed gas fitters and electricians, the gas and electrical safety regulators, the local network service provider and the environmental regulator, under work health and safety law and Safe Work Australia’s model code of practice for plant. This book teaches how to judge energy conversion. It is educational and is not a design or approval for any plant.

Who this book is for

Mechanical, process and energy engineers, plant managers, energy auditors and technical students who need to judge engines, turbines, heat recovery and cogeneration proposals with their own numbers.

What you will learn

  • Use the first law, heat rate and the Carnot limit to test any efficiency or power claim for a heat engine.
  • Analyse compressors and turbines in steady flow and find their isentropic efficiency from measured pressures and temperatures.
  • Work the air-standard Otto, Diesel and Brayton cycles and explain how far real gas engines, diesels and gas turbines fall short of them.
  • Calculate condensing and back-pressure steam turbine cycles, including heat rate and exhaust dryness.
  • Find the exergy of engine exhaust and jacket water, and judge recovery claims against it.
  • Calculate cogeneration utilisation and primary energy saving on a consistent heating-value basis, and build a heat-led business case.

Inside this book

Chapters

  1. 01Heat into work: the first law and the Carnot ceilingHow the first law accounts for every kilowatt of fuel, what efficiency and heat rate mean, and how the Carnot limit at real temperatures tests any claim to turn heat into power.
  2. 02Compressors and turbines in steady flowThe steady-flow energy equation for compressors, turbines, nozzles and throttles, isentropic efficiency from measured temperatures, and a turbocharger test that checks its own power balance.
  3. 03The Otto cycle and the gas engineThe air-standard Otto cycle step by step: compression ratio, efficiency, net work, mean effective and peak pressure, why the ideal overstates a gas engine, and how knock and lean burn set limits.
  4. 04The Diesel cycle and the standby generatorThe air-standard Diesel cycle with its cutoff ratio, how it compares with the Otto cycle at equal and at real compression ratios, peak pressure, and what the model says about a standby set.
  5. 05Real engines: fuel, heat rate and the energy balanceGross and net heating values, heat rate at full and part load, ratings and ambient conditions, the full energy balance of a gas engine, and exhaust flow and dew point from the air–fuel ratio.
  6. 06Gas turbines and the Brayton cycleHow a gas turbine turns fuel into shaft power: the Brayton cycle, pressure ratio, turbine inlet temperature, the back-work ratio, component efficiencies and why hot days cut output.
  7. 07Microturbines and the recuperatorHow a recuperator lifts a microturbine's efficiency, how effectiveness, size and pressure ratio interact, and why a cooler exhaust can leave a steam-using site worse off.
  8. 08Steam turbines: condensing and back-pressureThe Rankine cycle from steam-table enthalpies: condensing plant for scale, a back-pressure turbine in place of a pressure-reducing valve, exhaust dryness, heat rate and fuel chargeable to power.
  9. 09Recovering engine heat: exhaust, jacket water and the exergy limitWhere an engine's rejected heat goes, the exergy of a stream that cools as it gives up heat, matching each stream to a demand at the right temperature, and testing a heat-to-power claim.
  10. 10Cogeneration: utilisation, primary energy saving and the business caseJudge a cogeneration plant by utilisation, power-to-heat ratio and primary energy saving, size it to the heat demand, and build and stress-test the A$ business case for one site.

Apply This in Practice

Use these KEVOS® tools to try the method from this reading with your own numbers.

References and source notes

The manuscript and worked examples are original KEVOS® writing. References inform particular concepts; their authors do not endorse this book. Web references were consulted on 30 October 2026.

  • E. M. Greitzer, Z. S. Spakovszky and I. A. Waitz, Massachusetts Institute of Technology. 16.Unified: Thermodynamics and Propulsion (lecture notes) (2026). Open university notes used as the checkable reference for the steady-flow energy equation, the Carnot cycle, the Brayton, Otto and Diesel air-standard cycles and the Rankine cycle. The book's treatment, running case, numbers and exercises are original.
  • International Association for the Properties of Water and Steam. Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS R7-97) (2012). Formulation used, through an independent implementation, for every steam enthalpy, entropy, saturation temperature and specific volume in Chapter 8.
  • National Institute of Standards and Technology. NIST Chemistry WebBook, SRD 69 (2026). Source of the heat of combustion of methane and the enthalpy of vaporisation of water from which the higher and lower heating values in Chapters 1 and 5 are derived.
  • J. D. Cox, D. D. Wagman and V. A. Medvedev (eds), Hemisphere Publishing. CODATA Key Values for Thermodynamics (1989). Named in Chapter 5 as the source of the enthalpy of vaporisation of water at 25 °C, 44.0 kJ/mol, used to convert the higher heating value of methane to the lower.
  • International Organization for Standardization. ISO 8528-1 Reciprocating internal combustion engine driven alternating current generating sets, Part 1: Application, ratings and performance; ISO 3046-1 Reciprocating internal combustion engines, Performance, Part 1: Declarations of power, fuel and lubricating oil consumptions, and test methods (current editions). Named by number and scope in Chapters 4 and 5 for generating-set duty ratings and for the reference conditions behind engine power and fuel figures. Paywalled; no clauses or values are quoted.
  • Australian Taxation Office. Goods and services tax (GST) (current web page). Cited in Chapter 10 for the basis of comparing costs excluding GST: a registered business claims GST credits on its business purchases.
  • Australian Government, Department of Climate Change, Energy, the Environment and Water. National Greenhouse Accounts Factors (published annually). Named in Chapter 10 as the source of the emission factors for gas and for grid electricity by state that decide whether cogeneration lowers a site's emissions. No factors are quoted.
  • Australian Gas Networks. Understanding your gas bill (2026). Cited for the way Australian gas is billed by energy content in megajoules, the basis behind converting between billed (higher) and datasheet (lower) heating values in Chapters 5 and 10.
  • European Parliament and Council of the European Union. Directive 2012/27/EU on energy efficiency, Annex II (2012). Named as the origin of the primary energy saving measure for cogeneration used in Chapter 10. Its method is described, not quoted; the reference efficiencies in the book are the analyst's stated choices, not the directive's values.
  • S. Carnot. Réflexions sur la puissance motrice du feu (1824). Named as the historical origin of the reversible engine and the temperature limit on heat engines in Chapter 1. Its argument is described, not quoted.
  • Standards Australia and Standards New Zealand. AS/NZS 5601.1 Gas installations, general installations; AS 3814 Industrial and commercial gas-fired appliances; AS/NZS 3000 Electrical installations (wiring rules) (current editions). Named by number and scope in Chapter 10 as standards that bear on installing a gas engine generator. No clauses or values are quoted; the book does not cover their requirements.
  • Safe Work Australia. Model Code of Practice: Managing the risks of plant in the workplace (2022). Cited for the duty to manage the risks of engines, boilers, turbines and pressure plant discussed in the running case. The book does not cover plant safety; this code, the plant's own procedures and licensed trades do.

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