CHE 516: Energy Systems Engineering
Estimated study time: 9 minutes
Table of contents
Sources and References
Primary texts — Moran, M.J., Shapiro, H.N., Boettner, D.D., and Bailey, M.B., Fundamentals of Engineering Thermodynamics, 9th ed., Wiley, 2018; Sorensen, B., Renewable Energy, 5th ed., Academic Press, 2017.
Supplementary texts — Çengel, Y.A. and Boles, M.A., Thermodynamics: An Engineering Approach, 9th ed., McGraw-Hill, 2019; MacKay, D.J.C., Sustainable Energy — Without the Hot Air, UIT Cambridge, 2009 (open-access).
Online resources — MIT OCW 2.60 “Fundamentals of Advanced Energy Conversion”; Stanford ME 255 “Thermal and Mechanical Energy”; IEA World Energy Outlook public summaries; U.S. EIA data portal; IPCC AR6 WG3.
Chapter 1: Energy in Society
1.1 Scale and Units
Global primary energy consumption is roughly 600 EJ/year (\( 6 \times 10^{20} \) J), equivalent to about 19 TW average power draw. Units: 1 BOE ≈ 6.1 GJ; 1 tonne oil equivalent (toe) ≈ 42 GJ; 1 MWh = 3.6 GJ; 1 quad = 1.055 EJ. Per-capita consumption varies a factor of 30 across countries, reflecting industrial structure and lifestyle, not natural resource endowment.
1.2 Fossil Fuel Reserves
Proved reserves (90% probability of recoverability) vs. resources (geologic presence). Reserves-to-production ratios: oil ~50 years, natural gas ~50, coal ~140. Unconventional sources—shale gas/oil (hydraulic fracturing), oil sands (surface mining and in-situ SAGD), methane hydrates—have altered the picture dramatically since 2000, especially in North America.
1.3 Energy Services vs. Energy
Lighting, mobility, space heating, industrial heat, computing—these are the actual services demanded. Decoupling efficiency from service enables reductions in primary energy without lifestyle loss. Second-law analysis (exergy) quantifies how much of any energy stream is convertible to work.
Chapter 2: Thermodynamic Cycles
2.1 The Rankine Cycle
Steam power plants follow the Rankine cycle: pump → boiler → turbine → condenser. Ideal efficiency:
\[ \eta = \frac{w_{net}}{q_{in}} = \frac{(h_3 - h_4) - (h_2 - h_1)}{h_3 - h_2}. \]Enhancements: superheating (raises \( h_3 \) without moisture in turbine), reheating (multiple expansions with intermediate reheating), regeneration (feedwater preheating with extracted steam). Modern supercritical plants achieve 45%+ thermal efficiency.
2.2 The Brayton Cycle
Gas turbines follow the Brayton cycle: compressor → combustor → turbine. Ideal efficiency for ideal gas with constant \( C_p \):
\[ \eta = 1 - \frac{1}{r^{(\gamma-1)/\gamma}}, \]with pressure ratio \( r \). Real cycles incorporate component isentropic efficiencies (typically 0.85–0.90) and pressure losses. Combined cycle plants use Brayton exhaust to drive a Rankine cycle, reaching 60%+ efficiency.
2.3 Refrigeration and Heat Pumps
Reversed Brayton, vapor-compression, and absorption cycles provide cooling and heating. Coefficient of performance for heat pump:
\[ COP_{HP} = \frac{Q_H}{W_{in}}, \]with ideal (Carnot) upper bound \( T_H/(T_H - T_C) \). Heat pumps for space heating deliver 3–5 units of heat per unit of electricity, offering order-of-magnitude efficiency gains over combustion.
2.4 Combined Heat and Power
Cogeneration (CHP) and trigeneration produce electricity plus low-grade heat for process or district use, raising fuel utilization from ~35% (power only) to 80%+ total. Location of load (industry, district heating) governs applicability.
Chapter 3: Nuclear Energy
3.1 Fission Physics
\( ^{235}U + n \to \) fission products + 2-3 \( n \) + 200 MeV. Chain reaction self-sustains when the effective multiplication factor \( k = 1 \). Moderators (water, heavy water, graphite) slow neutrons to thermal energies for higher fission cross-section. Control rods (B, Cd, Hf) absorb neutrons to regulate \( k \).
3.2 Reactor Types
Pressurized water reactor (PWR), boiling water reactor (BWR), pressurized heavy water reactor (CANDU, Canadian), gas-cooled reactor (AGR), fast breeder (liquid metal coolant), small modular reactor (SMR). Each has characteristic fuel, coolant, moderator, and safety envelope.
3.3 Fuel Cycle and Waste
Uranium mining → enrichment (centrifuge, gaseous diffusion) → fuel fabrication → reactor → spent fuel storage → reprocessing (optional) → deep geological repository. High-level waste decays over \( 10^5 \) years; repository engineering (Yucca Mountain, Onkalo) solves for containment over comparable timescales.
3.4 Fusion
D-T fusion requires temperatures \( \sim 10^8 \) K and confinement time satisfying the Lawson criterion \( n\tau T > 10^{21} \) keV·s/m\(^3\). Magnetic (tokamak, stellarator) and inertial (laser, Z-pinch) confinement schemes compete. ITER and the SPARC/NIF generation pursue net energy gain; commercial fusion remains a multi-decade endeavor.
Chapter 4: Renewable Energy
4.1 Solar
Insolation: 1361 W/m\(^2\) top-of-atmosphere; \( \sim 150-250 \) W/m\(^2\) annual average at surface in temperate latitudes. Photovoltaic cells convert light directly, with Shockley-Queisser limit of 33% for single-junction silicon; commercial modules reach 20–24%. Concentrating solar thermal uses mirrors and a receiver to generate high-temperature heat for Rankine/Brayton cycles.
4.2 Wind
Wind power per unit area: \( P/A = (1/2)\rho v^3 \). Betz limit: \( 16/27 \approx 59.3\% \) of kinetic energy extractable. Modern turbines achieve 45–50% capacity factors onshore, higher offshore. Turbine size has grown from 50 kW in the 1980s to 15 MW offshore today.
4.3 Hydro and Ocean
Hydroelectricity remains the largest renewable source globally (~16% of electricity). Pumped hydro storage provides ~95% of grid-scale storage worldwide. Tidal (barrage, stream), wave, and ocean thermal energy conversion (OTEC) remain at demonstration or niche scale.
4.4 Bioenergy
First-generation biofuels (ethanol from corn/cane, biodiesel from oilseeds) raise food-vs-fuel concerns. Second-generation (lignocellulosic ethanol, biomass-to-liquid via gasification-Fischer-Tropsch) and third-generation (algal) technologies aim at higher yields without food competition. Life-cycle carbon balance is the key sustainability metric.
Chapter 5: Transportation and Portable Power
5.1 Internal Combustion Engines
Otto cycle (spark ignition): efficiency \( \eta = 1 - 1/r^{\gamma-1} \), with compression ratio \( r \sim 10 \) giving theoretical 60%, real 25–30%. Diesel cycle: higher \( r \sim 20 \), theoretical 65%, real 35–40%.
5.2 Hybrid Powertrains
Parallel, series, and series-parallel hybrids combine ICE with electric motor(s) and battery. Benefits: downsized engine at higher average load (better efficiency), regenerative braking, engine shutoff at idle. Plug-in hybrids extend range via larger battery and grid charging.
5.3 Fuel Cells
Proton exchange membrane (PEM) fuel cells: H\(_2\) + ½O\(_2\) → H\(_2\)O + electricity + heat. Ideal voltage 1.23 V; practical 0.6–0.8 V under load. Solid oxide fuel cells (SOFC) operate at 800 °C, accept hydrocarbons, and integrate with turbines. Hydrogen production (electrolysis, steam methane reforming with CCS) governs lifecycle emissions.
5.4 Batteries
Electrochemistry: anode + cathode + electrolyte. Li-ion energy density \( \sim 250 \) Wh/kg (cell), \( \sim 150 \) Wh/kg (pack). Cycle life 1000–5000 depending on chemistry. Emerging: solid-state (higher density, safer), lithium-sulfur, sodium-ion.
Chapter 6: Grid, Storage, and Carbon Management
6.1 Electricity Grid
Balancing generation and load in real time; frequency (60 Hz in North America) signals balance. Baseload (nuclear, coal, some hydro), load-following (gas, hydro), and peaking (gas peakers, diesel, batteries) operate on different timescales. Renewables’ intermittency drives flexibility needs.
6.2 Grid-Scale Storage
Pumped hydro: mature, siting-limited. Lithium-ion batteries: growing fast, short-duration. Compressed air (CAES), liquid air (LAES), thermal storage, flow batteries, hydrogen (power-to-gas): each fills different duration × power × cost niches. 4-hour duration dominates current installations; longer-duration (days-weeks) storage technology is active R&D.
6.3 Carbon Capture, Utilization, Storage
Post-combustion (amine scrubbing), pre-combustion (syngas shift + separation), oxyfuel (pure O\(_2\) combustion producing CO\(_2\) + H\(_2\)O), direct air capture. Storage in saline aquifers, depleted oil/gas reservoirs, mineralization. Utilization (enhanced oil recovery, concrete curing, CO\(_2\)-derived fuels) partially offsets cost.
6.4 Systems Analysis
Integrated assessment models, energy-economy-environment (E3) models, and detailed capacity expansion models guide planning. Scenario analyses (IEA STEPS, Net Zero; IPCC SSPs) explore futures under different policy and technology assumptions.
