Why wind and solar cannot carry the “Energiewende”

Dr. Peter F. Mayer, tkp.at

The green transformation is not failing for lack of idealism, but because of the laws of nature. A sober look at the structural limits of wind and solar energy.

In the current public debate, wind turbines and solar panels are readily presented as a simple replacement for coal, oil and gas. But anyone who looks at the physical fundamentals quickly realises that this narrative does not withstand objective scrutiny. The limits of wind and sun are not political or economic questions — they follow inevitably from the nature of the energy sources themselves and from the physics of electricity, as the analysis “The Core Issues With Renewables” by S. Andrews clearly sets out.

Wind power and the cube law: hard mathematics instead of green hope

The power that can be extracted from the wind is proportional to the cube of the wind speed — the so-called cube law. Anyone who understands the physics knows that this extreme sensitivity means that wind power generation fluctuates strongly, even on an hourly basis.

Regions that appear “windy” on an annual average repeatedly experience long periods of low or even zero output. The actual utilisation (capacity factor) of onshore wind turbines in many temperate climate zones is only between 25 and 35 per cent — offshore sites perform better, but remain subject to the same cubic relationship. A single calm day can simply wipe out a large part of the expected output.

Solar power: daily and seasonal mismatch with demand

Solar irradiation follows the Earth’s rotation and its orbit around the Sun. At night the yield is zero. Even during the day, cloud cover, atmospheric conditions and the angle of incidence reduce the energy collected. The seasonal effect is enormous: in middle and high latitudes, winter irradiation can amount to only a third to a fifth of summer values.

A solar plant designed for summer peak demand delivers only a fraction of its output in winter — precisely when heating demand is highest in many countries. The result is a generation profile that is predictable, but stubbornly out of step with demand. No number of additional panels changes the fact that the resource itself is interrupted by daily and annual cycles.

The energy density dilemma: electricity is not everything

Electricity is a high-quality form of energy, but in practice not an energy-dense one. Fossil fuels store large amounts of chemical energy in a compact, stable and easily transportable form: a litre of diesel contains about 35–38 MJ, a litre of petrol around 32–34 MJ. The best commercial lithium-ion batteries, by contrast, manage only about 0.9–1.0 MJ per litre — and far less on a mass basis once packaging and thermal management are taken into account.

This discrepancy has direct consequences for agriculture and transport: tractors, combine harvesters, heavy lorries, ships and aircraft require high power densities and long ranges.

If diesel is replaced by batteries, the mass to be carried multiplies, the payload falls, and frequent, long charging times become necessary.

For many agricultural tasks and long-distance freight, the energy density gap remains decisive. Electrification works well for light vehicles and short distances — for high-energy applications that today depend on liquid fuels, it is far more difficult.

Storage: the missing link in the chain

Hydrocarbons come already stored: coal, oil and gas can be stockpiled for months or years with modest infrastructure. Electricity, by contrast, must be generated and consumed almost simultaneously — or converted into another form and stored.

• Grid storage batteries can provide short-term balancing (minutes to a few hours).
• Longer-term storage — days, weeks or seasonal — remains expensive and technically limited.
• Pumped storage is geographically restricted.
• Hydrogen and synthetic fuels cause large conversion losses.
• Compressed air and other mechanical systems have their own efficiency and location limits.

Because wind and solar output can remain low for days or weeks (the well-documented European “Dunkelflaute” phenomenon, or dark doldrums), the need for storage is not marginal but systemic. Until affordable, long-term storage on a continental scale exists, the intermittency of wind and sun must be cushioned by backup generation — in practice mostly natural gas, sometimes also coal or nuclear power, always at considerable additional cost.

Grid stability: the narrow line between blackout and overproduction

A power grid must balance generation and consumption within narrow limits. The variability and unpredictability of wind and solar power make this balance extremely difficult — not only when output falls, but also when it suddenly rises, which increases the risk of blackouts, as we saw in Spain.

Electricity is admittedly only a minor component (18.3 per cent) of the total energy consumption of a modern economy — yet practically every area of society depends on it. The consequences of an unstable grid are therefore far-reaching, even if the “electricity share” appears small.

Physics as the first-order variable

The cube-law sensitivity of wind, the daily and seasonal absence of the sun, the low practical energy density of electricity compared with liquid or solid fuels, and the difficulty of storage on a large scale are not temporary weaknesses. They are consequences of physics, as S. Andrews rightly stresses in his analysis.

Any serious energy strategy must treat these physical realities as first-order constraints — and not as minor details that can be overcome by sheer scale alone. Anyone who ignores this is building on sand. Or, in the most literal sense: on wind and weather.

Can energy be “renewed” at all?

The term “renewable energies” is one of the most successful marketing constructs of recent decades. It suggests that wind, sun and water are an inexhaustible source – as if the energy were simply “there” and only had to be harvested. But physics and economics tell a different story. Anyone who looks more closely will see that the term “renewable” is a semantic deception. The term “renewable energies” obscures the decisive point: energy is not renewable – it can only change its form. The First Law of Thermodynamics says that energy can neither be created nor destroyed, only converted. The Second Law says that in every conversion part of it is lost as heat – entropy increases.

The installations that use these sources are also anything but renewable: they are made of steel, concrete, copper, rare earth metals and plastics – all finite and produced with considerable energy expenditure. The central question is therefore not “Is the energy renewable?”, but: “How much energy do I have to invest in order to obtain the energy?” – this is the question of EROI (Energy Return on Investment), also known in German as the “Erntefaktor” (harvest factor).

More about the problems and health hazards of wind power:

Die Windkraft-Lüge. Was Windräder in Wahrheit anrichten (The wind power lie: what wind turbines really do) Dr. Peter F. Mayer, Torsten Engelbrecht. TKP Verlag, 1st edition 2026. Paperback ISBN 978-3-9506363-0-7.

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This article first appeared in German on tkp.at – with kind permission of Dr. Peter F. Mayer.
Cover image: seagul / Pixabay