Alternative Energy Resources
A Living Textbook for the Energy Transition
Preface
“The energy problem is not primarily a scientific problem; we understand the physics quite well. It is not primarily a technological problem; most of the technologies we need either exist or are within reach. It is fundamentally a problem of scale, systems, and choices.”
This textbook began as an update to David MacKay’s Sustainable Energy: Without the Hot Air (2008), one of the clearest expositions of energy mathematics ever written. MacKay, the Cambridge physicist who served as Chief Scientific Adviser to the UK Department of Energy and Climate Change, insisted on “numbers, not adjectives.” He demonstrated that you could cut through the rhetoric surrounding energy policy with nothing more sophisticated than multiplication and division, a healthy respect for physical laws, and a commitment to internal consistency.
MacKay passed away in 2016, but his intellectual legacy remains vital. The physics in Without the Hot Air is as correct today as when he wrote it. The Carnot limit still constrains heat engines. The Shockley-Queisser limit still bounds single-junction solar cells. Conservation of energy remains undefeated.
What has changed, dramatically, is the economic and political landscape surrounding that physics.
What Changed Since 2008
When MacKay wrote his book, solar photovoltaic panels cost over $5 per watt, making them a niche technology for satellites and remote applications. Today they cost under $0.20 per watt, a decline of more than 96%. Battery packs for electric vehicles cost $1,200 per kilowatt-hour; today they cost $108/kWh, heading toward $80/kWh. Wind turbines have roughly tripled in size while their levelized cost has fallen by two-thirds.
These cost reductions were not foreseeable from physics alone. They emerged from the interaction of technology, manufacturing scale, policy support, and market competition: the full chain from Principle through Outcome that this textbook examines.
But dramatic cost reductions have not produced a dramatic energy transition. Global fossil fuel consumption continues to rise, reaching new highs in 2024. Carbon dioxide concentrations have climbed from 385 ppm when MacKay wrote to over 425 ppm today. The share of fossil fuels in primary energy has declined from 82% to roughly 80% over fifteen years. This is progress, but far from the transformation required.
Here we confront the central tension of our subject: extraordinary technological progress coexisting with inadequate systemic change. This is not a puzzle that physics alone can solve. It requires understanding infrastructure lock-in, political economy, supply chains, and the sheer scale of the global energy system.
The Framework for Change
This textbook is organized around a five-stage framework that connects fundamental physics to real-world outcomes. The framework operates bidirectionally:
\[ \text{Principle} \longleftrightarrow \text{Technology} \longleftrightarrow \text{Product} \longleftrightarrow \text{Policy} \longleftrightarrow \text{Outcome} \]
Principle: The underlying physics or chemistry (photovoltaic effect, nuclear fission, thermodynamic limits). These set hard boundaries on what is possible.
Technology: The engineered system that exploits a principle (silicon solar cells, pressurized water reactors, lithium-ion batteries). Technologies can be improved but are constrained by principles.
Product: The commercially available offering (a JinkoSolar panel with specific efficiency, a Tesla Megapack with defined capacity, a GE wind turbine with a warranty). Products have prices, specifications, and supply chains.
Policy: The rules, incentives, and regulations that shape deployment (investment tax credits, feed-in tariffs, renewable portfolio standards, building codes, grid interconnection rules). Policy creates or destroys markets.
Outcome: The measured results (emissions reductions, electricity prices, reliability metrics, employment figures, health impacts). Outcomes are what ultimately matter.
Two Directions of Analysis
Reduction to Practice (left to right): Starting from principles, how do we develop technologies, commercialize products, and design policies to achieve desired outcomes? This is the engineer’s and policymaker’s direction: given what physics allows, what can we build and deploy?
Reduction to Understanding (right to left): Observing outcomes, what do they reveal about the underlying principles, technologies, and policies at work? This is the analyst’s and scientist’s direction: given what we see happening, what explains it?
Both directions matter. The steam engine preceded the formal laws of thermodynamics; Carnot analyzed existing engines to understand their limits. Today’s battery research is driven by market demand, not pure curiosity. Solar policy failures reveal technology constraints; technology breakthroughs reshape policy possibilities. Understanding flows both ways.
The Energy Trilemma
Every energy decision involves tradeoffs among three objectives:
Security: Reliable supply that meets demand when and where needed. Security includes physical reliability (do the electrons flow?), supply chain resilience (what if a key supplier fails?), and fuel diversity (how exposed are you to price shocks?). Security is what economists call a threshold good: below a minimum, everything else falls apart.
Equity: Fair distribution of costs and benefits. Equity asks: Who can afford adequate energy? Who lives near power plants and mines? Where are jobs created and lost? The “green premium” (the extra cost of clean alternatives) falls differently on different communities.
Sustainability: Long-term environmental consequences. Sustainability encompasses climate impacts (lifecycle greenhouse gas emissions), local pollution (air and water quality), resource depletion (are we drawing down stocks?), and ecosystem effects (land use, biodiversity, water). A critical insight: sustainability now is equity later. Environmental damage imposes costs on future generations with no voice in today’s decisions.
No country has solved all three dimensions simultaneously. Every energy choice involves tradeoffs among them. This textbook will help you understand those tradeoffs rather than pretend they don’t exist.
How This Book Is Organized
Module 1: Foundations and Thermodynamics establishes the physical and analytical foundations. Chapter 1 introduces the Framework for Change and Energy Trilemma. Chapter 2 covers thermodynamic laws, the hard constraints on all energy conversions. Chapter 3 places these principles in modern context, including the Smil-versus-optimists debate about transition timescales.
Module 2: Harvesting the Sun examines energy sources that ultimately derive from solar radiation. Chapters 4-5 cover fossil fuels (stored ancient sunlight), including their chemistry, geography, and conversion technologies. Chapters 6-9 address solar photovoltaics: the physics, the manufacturing revolution, the circuitous policy history, and current challenges. Chapters 10-12 treat wind energy analogously. Chapter 13 covers biofuels (contemporary photosynthesis). Chapter 14 addresses hydropower, waves, and tides.
Module 3: Geothermal and Nuclear turns to non-solar sources. Chapters 15-16 cover geothermal energy, including the emerging Enhanced Geothermal Systems that could make geothermal a global rather than niche resource. Chapters 17-18 address nuclear fission (its physics, safety history, and economics) and nuclear fusion’s uncertain promise.
Module 4: Storage, Sourcing, and Future Systems addresses the integration challenges. Chapters 19-20 cover energy storage, especially the battery revolution. Chapter 21 examines hydrogen and grid infrastructure. Chapter 22 addresses critical minerals and supply chains, the geographic and geopolitical constraints on deployment. Chapter 23 tackles the “hard stuff”: sectors like aviation, shipping, steel, and cement where decarbonization remains technically and economically difficult.
Module 5: The Energy RPG applies everything to a capstone simulation where you take on stakeholder roles and negotiate energy transition decisions under realistic constraints.
How to Use This Book
Each chapter follows a consistent structure:
- Physical principles first: what does physics permit and forbid?
- Technology and products: how have engineers exploited those principles?
- History and policy: what actually happened and why?
- Trilemma analysis: how does this technology score on Security, Equity, and Sustainability?
- Quantitative exercises: building your own back-of-envelope intuition
We encourage you to work through the calculations yourself. Check our numbers. Find our errors (there will be some). The point is not to memorize figures but to develop the facility to generate reasonable estimates quickly.
Throughout, look for these recurring elements:
Step-by-step estimates you can reproduce with basic arithmetic.
Explicit links to Principle → Technology → Product → Policy → Outcome.
Where Security, Equity, and Sustainability conflict, and how different stakeholders resolve them differently.
A Note on Data Currency
Energy data ages quickly. The costs, capacities, and projections in this textbook are accurate as of late 2025, but the landscape continues to shift. We note publication years for all major data sources and encourage you to consult primary sources for current figures.
Some key references that are regularly updated:
- International Energy Agency (IEA): World Energy Outlook, Global Energy Review
- International Renewable Energy Agency (IRENA): Renewable Power Generation Costs
- BloombergNEF: Battery price survey, energy transition investment reports
- U.S. Energy Information Administration (EIA): Annual Energy Outlook
The physics doesn’t change. The economics does. This book gives you the tools to interpret both.
Acknowledgments
This textbook builds directly on David MacKay’s Sustainable Energy: Without the Hot Air, which remains freely available at withouthotair.com. MacKay’s intellectual generosity in making his work openly accessible set a standard we aspire to follow.
We are indebted to the scholars whose work informs every chapter.
Special thanks to the students of EAEE 4002 who have tested earlier versions of these materials and whose questions invariably revealed where our explanations fell short.
This is a “living textbook” updated annually. Energy economics and policy evolve rapidly; foundational physics does not. We maintain version notes indicating when specific data was current and flag sections most likely to require revision.