Energy: Sources and Forms
Nothing happens without energy. To understand it is to understand a piece of how our world is held together, and who holds it in their hands.
Energy sounds like physics class, like formulas and dry numbers. Yet it is one of the most political things there is. Whoever has access to energy can heat their home, travel, produce and have a say; whoever does not freezes and falls behind. A critical look at energy is therefore not a purely technical question but a question of self-determination: do we understand what we depend on, or do we let others decide it for us?
Energy and power: two words that are often confused
In everyday life we mix up the two terms, but they mean different things. Energy is the ability to bring something about: to generate heat, to lift a weight, to move a car. Power is energy per time, that is, how fast this ability flows.
An image makes it clear: energy is the water in the bucket, power is the jet from the tap. A thin jet (little power) can fill the same bucket over many hours as a mighty gush (a lot of power) does in a few seconds. We measure energy in kilowatt-hours (kWh) and power in watts (W). An old 100-watt light bulb burning for ten hours uses one kilowatt-hour. This very distinction is often blurred in debates, for instance when a "giant plant" is advertised with its peak power, but no one says how much it actually delivers over the year.
What we need energy for
Almost everything that makes up our day is converted energy. We heat in winter and cool in summer, we cook, light rooms, move around by bus, train and car, we lift loads with cranes and elevators, and even reading this text runs on a device that computes. No prosperity without energy: it is the silent raw material behind food, clothing, housing and communication.
How much can a person produce, and how much do they consume?
This is where it gets interesting, because the comparison exposes something we take for granted. A person exerting themselves can sustain only about 100 watts of usable muscle power, just about as much as that old light bulb. A trained racing cyclist might hold 300 to 400 watts for a short time, but not for long.
Now weigh against that how much energy a person in a rich country actually claims. Add it all up (electricity, heating, transport, the energy for manufactured goods), and a person in Germany consumes on average around 6000 watts around the clock.1 That is sixty times what they can produce themselves. Put vividly: each of us invisibly commands dozens of tireless "energy slaves" toiling in the background: machines, motors, power plants. This comfort is an enormous privilege, and it is unequally distributed: worldwide the average is closer to 2500 watts, in many countries far below.
This is exactly where the idea of the 2000-watt society comes in, a concept from Switzerland. It simply asks: how much could each person consume permanently if everyone got the same and the planet could bear it? The answer is roughly 2000 watts.1 That is not a threat of doing without, but a question of fairness that one can take up once one has grasped the numbers.
Energy consumption and quality of life
A stubborn myth goes: more energy means more prosperity, less energy means going without and falling back. The numbers tell a different story. In many industrialized countries the economy grows while energy consumption falls. In Germany, for example, final energy consumption has tended to decline since the 1990s, even though gross domestic product (GDP) has risen markedly over the same period.2 Experts call this decoupling: prosperity and hunger for energy no longer march in lockstep.
This is made possible by efficiency (an LED shines using a fraction of the electricity of a light bulb), by better-insulated houses, more economical engines and a restructuring of the economy away from energy-hungry heavy industry toward services. The decisive message is emancipatory: More quality of life is entirely compatible with less energy consumption and less CO₂ emission. A warm, bright home, good food, mobility and culture do not depend on the sheer quantity of kilowatt-hours consumed, but on how cleverly we use them. Whoever understands this need not let the debate be forced on them as a choice between climate protection and a good life, for this opposition is often a rhetorical manoeuvre, not a law of nature.
Many forms, many sources
Energy appears in many guises: as motion, heat, light, chemical bonds, electric current.3 For us, two ends of the chain matter above all: electricity and heat.
Electricity we obtain today from a colourful mix: wind on land and at sea, flowing water, sun, plus coal, oil, gas and waste incineration, geothermal heat as well as nuclear fission (and perhaps one day nuclear fusion). Heat is supplied directly by the sun, and also by coal, oil, gas, biomass such as wood, and likewise nuclear energy.
Before it becomes electricity or heat, there are the primary energy sources, roughly ordered into three groups: fossil energy (coal, oil, gas), nuclear energy and renewable energies (sun, wind, water, biomass, geothermal). Every conversion costs something, because at each step a part is lost as unused heat. That is why the most efficient kilowatt-hour is always the one we never consume in the first place.
In the end there are only a few origins
However bewildering the variety seems: almost everything can be traced back to a handful of primal sources. By far the most important is the sun. It drives the weather and with it the wind; it evaporates water that, as rain, feeds the rivers and thus hydropower; it makes plants grow, from which food, wood and biomass are made. And even coal, oil and gas are nothing but ancient solar energy, bound up in plants and tiny organisms and pressed into the ground over millions of years. When we burn fossil fuels, we are burning the sunlight of the day before yesterday.
Only a few sources do not come from the sun: geothermal heat from the hot, partly radioactively heated interior of the Earth, nuclear energy, whose heavy atoms once formed in exploding stars, and tidal energy, which comes from the gravitational pull of the moon and sun. This is more than a pretty piece of natural history: it shows how deeply we are embedded in larger cycles, and how short-sighted it is to burn through a store millions of years old in a few generations.
Why this concerns everyone
You don't have to be a physicist to have a say on energy. It is enough to know the difference between energy and power, to be able to put your own figures in context, and to ask where something actually comes from and who profits from it. For behind every kilowatt-hour lie decisions about prices, dependencies and power. Whoever understands the basic concepts is caught neither by advertising promises nor by fear-mongering slogans, and can judge in a self-determined way. That is exactly what critical thinking about energy is about: not learning answers by heart, but being able to ask the right questions.