Energy explained simply

Energy is messy. These explainers make it a little less ridiculous — for readers, professionals, and companies alike.

Illustration of a house above water with a hidden underground grid system below, representing ancillary services that support reliable electricity.

What are ancillary services? The grid services nobody notices until something goes wrong

Buying enough electricity is not enough to run an electricity system. The grid also needs resources that can react in seconds, hold frequency, support voltage, replace a generator that suddenly disappears, and even help restart the system after a blackout. Those invisible jobs are called ancillary services—and as power systems add batteries, renewables, demand response, and power electronics, they are becoming much more visible.

Cross-section illustration of a district heating network with red and blue underground pipes supplying heat to city buildings.

What is district heating? One heating system for an entire city

Most buildings have their own boiler, furnace, or heat pump. District heating asks a very different question: why should every building make heat separately? Produce heat centrally, recover it from places already throwing it away, move it through insulated pipes, and an entire neighborhood—or city—can share one thermal system. The idea is old. What we can feed into those pipes is becoming much more interesting.

Featured image showing natural gas being cooled into LNG and transported by an LNG carrier across the sea.

What is LNG? How natural gas learned to cross an ocean

Natural gas has one awkward physical problem: as a gas, it takes up an enormous amount of space. LNG solves that by cooling natural gas to around −162°C, shrinking its volume roughly 600 times and turning a pipeline-bound fuel into something that can cross oceans on ships. That simple phase change quietly transformed natural gas from a regional commodity into a global one.

Featured image showing renewable electricity being turned into an e-fuel droplet at a clean fuel plant, with wind, solar, an airplane, and a cargo ship nearby.

What are e-fuels? Turning electricity back into something you can burn

E-fuels do something wonderfully inefficient—and potentially very useful. They take renewable electricity, use it to make hydrogen, combine that hydrogen with captured carbon, and rebuild familiar fuels such as kerosene, methanol, or synthetic diesel. Why bother turning electricity into fuel instead of simply using the electricity? Because some machines are much easier to decarbonize with molecules than electrons.

Illustration of Earth resting beside a geothermal power plant with wells carrying hot and cool water through underground heat.

What is geothermal energy? The renewable power plant hiding under your feet

The Earth is hot beneath our feet—hot enough in the right places to heat cities and generate electricity around the clock. Geothermal energy taps that underground heat, but the real story is more interesting than “find a volcano and drill.” New drilling technologies may be turning one of renewable energy’s most geographically limited resources into something much bigger.

Illustrated Combined-Cycle Gas Turbine plant with glowing hot exhaust moving from a gas turbine through heat recovery equipment to a steam turbine producing electricity.

What is a Combined-Cycle Gas Turbine? Two turbines, one flame

A combined-cycle gas turbine burns natural gas once but extracts electricity in two stages: first from a gas turbine, then from a steam turbine powered by the hot exhaust the first turbine was about to throw away. That simple act of refusing to waste heat is why CCGTs can reach efficiencies around 60%—and why they still matter in a power system filling up with wind, solar, and batteries.

Illustrated winter scene showing a heat pump outside in the snow sending warm glowing heat into a cozy home where a family sits indoors.

What is a heat pump? The heater that refuses to make heat

A heat pump can deliver three or four units of heat while using roughly one unit of electricity. No, it is not breaking physics. The trick is that it does not create most of the heat—it moves heat that was already there. Here is why your refrigerator, air conditioner, and one of the biggest technologies in building decarbonization are basically members of the same family.