Sustainable energy: a grand challenge in demand for fundamental science
Robert Schlögl, Fritz-Haber-Institut der MPG
Access to sustainable energy is a key requirement for almost all individual and societal
activities. Our dependence on this strategic product comes to the attention of the public
and politics only in intervals dictated by failures of markets or technologies impeding
the silent gigantic industry providing these goods (“oil crisis”).
We exhaust the global resources of energy carriers at much too high rates translating
into low prices ignoring the societal cost and the loss of opportunity for future
generations. Very little seems to counteract the enormous economic drivers and the
political request for “affordable” energy supports this tendency.
Free energy as a physical entity is a highly valuable resource that is plentiful in dilute
solar form but rare in controllable dense forms required for human economic and
cultural activities. The residual time of some decades before real shortages of fossil
carriers will occur and upset human activities, should be used to find technical and
societal measures for a sustainable harvesting and conversion of energy carriers
preferable independent of the resources of biological life. These resources will be
needed for food production and for stabilizing the global ecosystems as prerequisite of
human life.
Such a conversion of the energy basis is probably the greatest actual challenge of
civilization. We need all possible sustainable solutions that can convert solar energy into
immediate and storable free energy carriers represented by electricity and by solar fuels
for high-power density applications such as load transportation, aircraft operation and
production of structural materials.
The two fundamental options are solar primary energy or nuclear primary energy. As
uranium-based fission technology carries critical risks and other fission processes are
not explored yet, we have a realistic, yet far from technological option in fusion energy.
In analogy to nature, all solar processes fall into two steps of first energy concentration
and charge carrier separation, followed by a conservation step into a fuel, for all that
energy that cannot be used immediately as electricity in a demand-driven grid system.
The first step is already quite developed and we have technologies in operation
performing this task in the form of windmills, photovoltaics and hydropower stations.
Energy storage in grid dimensions is only possible in thermo-mechanic forms such as
pumpwater and molten salt storage solutions. Large challenges arise form the grid-wide
implementation of these non-fossil energy conversion technologies.
What we lack fundamentally, however, are energy storage options. Already now we have
to reduce the grid consumption of primary electricity simply because we cannot stop the
operation of fossil and nuclear stations for technological and/or economic reasons. The
required energy storage capacity in dimensions of a sizeable fraction of all primary
energy consumption is required in temporal and regional highly diversified forms: we
need short-term (h), medium-term (d) and long-term (a) storage options in doublefigures GW dimensions distributed in Europe. In addition, the storage devices must cope
with fluctuating operation, partial loading and rapid on-off switching characteristics.
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Thermo-mechanical storage options are useful but lack severely specific energy
densities. We thus need to revert to chemical energy storage. This occurs either in
batteries (secondary elements) or in solar fuels, preferably of a similar chemical
structure than our current fossil fuels with, however, a better-defined molecular
structure. This can only be achieved if we combine the electrochemical water splitting
for hydrogen with a solar refinery technology that converts CO2 and nitrogen into solar
fuels. The carbon pool for the CO2 comes either from carbon capture technologies or
from biomass utilization (direct or after fermentation or combustion). Such a strategy
replaces the natural carbon cycle via CO2 and photosynthesis by an artificial
“photosynthesis” with split unit operations for creation of electrons and for chemicals.
The inherent advantage of this strategy over the also useful “artificial leaf” approach,
that mimics natural photosynthesis in a single integrated device, is the large fraction of
primary electricity that can be used without any conversion losses that otherwise occur
if a purely photosynthetic solar fuel generates all electricity needs.
All the elementary processes of such a scenario can work on the laboratory scale. Some
unit operations are used in current technologies and can be built on grid scales. None of
the processes of a solar refinery are, however, operational in large scale under the
essential pre-condition of sustainability. This condition encompasses all functional
materials (such as noble or rare chemical elements) and processes (no waste
production, no deposits with unknown risk for future generations, no competition with
food generation).
It is thus evident that we critically need a massive effort in fundamental research to
overcome these hurdles. It must be seen that the basic challenges of chemical reactions
are being studied since decades without having found suitable solution strategies. It is
far from correct that the energy challenge is merely a technological or economic
challenge only: foremost it is a conceptual challenge when it comes to replacing the
system of fossil energy by a system of regenerative energies.
We have conceptual tools to tackle these grand challenges allowing to foresee that they
can be solved on time scales required by the systemic change of the energy supply
system. In order to achieve this, we need changes on the boundary conditions of
research and developments. The present energy science is sub-critically fragmented and
overloaded by top-down regulations stemming from the incorrect idea that we can
manage the energy system conversion on the basis of current knowledge. This is only
true for few selected elements of such as system. Besides energy storage also the
management of energy distribution and fuel conversion carry similar challenges
residing in material science, informatics and engineering. In all these areas a bottom-up
search for scalable and sustainable conceptual solutions is necessary.
The enormous scale of energy conversion in financial dimensions of the EU national
product requires timescales of adaptation of decades. This is the chance for science and
technology to emerge fast enough in several fields provided that science political
restrictions are rapidly removed. A non exhaustive list of issues are the critical size of
grants, bottom-up organization with sufficient grant periods, a trust-based reward
system that minimizes fast-track research, removal of funding constraints and
exaggerating reporting requests within EU, collaborations that need to be only resultdriven, sufficient funds in relation to the size of the challenge, termination of non-quality
driven funding, trustful science-economy collaboration through useful IP regulations.
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These modifications in the science system need to be stable and predictable in order to
attract sufficient human resources in typically unattractive disciplines of hard sciences
and engineering.
If we can liberate the creativity and ingenuity of Europe’s science infrastructure it
should be well possible to solve the energy issues in such useful terms that we not only
secure the energy needs of Europe but even create technology for export in regions of
the world where energy consumption is much higher than here. This would contribute
most to mitigate the climate change and to sustain peaceful evolution of mankind.
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