Making electricity: thermal, nuclear, hydro, wind and solar

By the end you will be able to

• Trace the energy balance of a steam power plant and explain why most of the fuel's energy leaves as low-temperature heat
• Explain how gas turbines, combined-cycle plants and diesel engines work, and where each is used
• Describe how nuclear fission makes electricity and weigh its record against its early promise
• Use the simple physics of falling water, wind speed and sunlight to estimate output from hydro, wind and solar plants
• Read the 2025 global electricity mix and current generation costs, and judge what they do and do not tell an investor

Contents

1. Part 1 Steam: the workhorse of electricity

   For more than a century most electricity has been made the same way: burn something, boil water, let the steam spin a turbine. Coal, gas, biomass, nuclear and some solar plants all share this core. Understanding where the energy goes inside a steam plant explains its efficiency, its appetite for water and why it still matters for grid reliability.

   • A steam plant turns fuel into a spinning shaft in four steps
   • Most of the fuel's energy leaves as warm water, not electricity
   • Hotter steam and reused heat push efficiency up
2. Part 2 Gas turbines and diesel engines

   Steam is not the only way to turn fuel into motion. Gas turbines let the burning gases themselves spin the blades, and diesel engines push pistons with the force of combustion. Smil calls these two machines the prime movers of globalisation: they fly the planes, drive the ships, back up the grids and balance the wind and sun.

   • A gas turbine burns fuel in a stream of compressed air
   • Combined cycle recovers the turbine's hot exhaust
   • Diesel engines win where efficiency and compact fuel matter most
3. Part 3 Nuclear electricity

   A nuclear power station is a steam plant whose boiler has been replaced by a reactor. The physics of fission gives uranium an energy density millions of times that of coal, and reactors run almost without interruption. Yet nuclear power never became the dominant, cheap source its pioneers promised, and its share of world electricity has shrunk for three decades even as output hit a record.

   • Fission heat raises steam, and a little fuel goes a very long way
   • Smil calls nuclear power a successful failure
   • Nuclear output hit a record in 2025 while its share kept shrinking
4. Part 4 Hydro and wind: electricity from moving water and air

   Hydro and wind plants skip heat altogether. They take the kinetic or potential energy of flowing water and moving air and turn it straight into shaft rotation, so there is no second-law penalty and no fuel. What limits them instead is geography and weather: how much water falls how far, and how fast and how often the wind blows.

   • Hydro output is flow times height, and the best sites are finite
   • Wind power rises with the cube of wind speed
   • Onshore wind is now the cheapest new electricity, but it is built with fossil fuels
5. Part 5 Solar electricity and the 2025 mix

   Photovoltaic cells are the only common way of making electricity with no moving parts at all. After a slow start lasting more than a century, solar became the fastest-growing source of electricity in history in the 2020s. Its rise is reshaping the world mix, but its daily rhythm and low capacity factor bring their own problems.

   • A solar cell turns light straight into direct current
   • Solar became cheap through manufacturing scale, but it only works by day
   • In 2025 renewables matched coal, and solar and wind covered the growth in demand
6. Wrap-up Key terms, try it in the table, final quiz, sources