The Future of Energy Supply: Challenges and Opportunities Nicola Armaroli* and Vincenzo Balzani*

Essays

DOI: 10.1002/anie.200602373 Renewable Energies The Future of Energy Supply: Challenges and Opportunities Nicola Armaroli* and Vincenzo Balzani*

Keywords: hydrocarbons · natural resources · photochemistry · renewable energies · science and society · solar energy conversion

Dealing with Change help in solving the energy problem? Will it be possible for all the Earths “Questions are never indiscrete, answers inhabitants to reach the standard of sometimes are.” living of developed countries without Oscar Wilde devastating the planet? Will science and technology alone take us to where we Each generation is confronted with need to be in the next few decades? new challenges and new opportunities. Should we, citizens of the western world, In a restricted system like the Earth, change our lifestyle and shift to innova- however, opportunities discovered and tive social and economic paradigms? exploited by a generation can cause Can people living in poor countries challenges to the subsequent ones. Fossil improve their quality of life? fuels have offered astounding opportu- Forty years ago, looking at the first nities during the 20th century in the rich Figure 1. In this 1970 picture, an average photos of the Earth seen from space, we countries of the western world, but now American family is surrounded by the barrels fully realized that our planet is a space- mankind has to face the challenges of oil they consume annually. Now this con- ship that travels without any destination arising from fossil-fuel exploitation. sumption is about 40% higher. in the infinity of the universe. As The proven reserves of fossil fuels are passengers of this spaceship we are progressively decreasing,[1] and their deeply interested in finding solutions continued use produces harmful effects, is, a steady 13 trillion watts of power to the energy crisis. As parents, we wish such as pollution that threatens human demand. How long can we keep running to leave our planet in a good shape for health and greenhouse gases associated this road? the benefit of future generations. As with global warming. Currently the scientists, we do have the duty to con- worlds growing thirst for oil amounts tribute to the discussion on the impend- to almost 1000 barrels a second,[2] which ing energy crisis. As chemists, we can means about 2 liters a day per each “Currently the world’s growing help improving energy technologies person living on the Earth (Figure 1).[3] and, hopefully, finding scientific break- The current global energy consumption thirst for oil amounts to almost throughs capable of solving the energy is equivalent to 13 terawatts (TW), that 1000 barrels a second.” problem at its root. Finally, as citizens of the affluent part of the world, first class passengers of spaceship Earth, we [*] Dr. N. Armaroli should ask ourselves how can we really Molecular Photoscience Group Istituto per la Sintesi Organica e la Fotor- Energy is the most important issue help passengers now traveling in much eattività of the 21st century. Here is the funda- worse compartments of this spaceship. Consiglio Nazionale delle Ricerche mental challenge we face, here are many We know that our lifestyle, based on Via Gobetti 101, 40129 Bologna (Italy) vital and entangled questions that we consumerism, may cause disparities. Fax : (+39)051-639-9844 are called to answer. Can well-being, or Disparity is, indeed, the most prominent E-mail: [email protected] even happiness, be identified with the characteristic among the Earths inhab- Prof. Dr. V. Balzani highest possible amount of per capita itants and, in the long run, the most Dipartimento di Chimica “G. Ciamician” energy consumption? Should we pro- dangerous problem. Finding a correct Università di Bologna Via Selmi 2, 40126 Bologna (Italy) gressively stop burning fossil fuels? Can solution to the energy crisis could offer Fax : (+39)051-209-9456 scientists find an energy source capable the opportunity to reduce disparity and E-mail: [email protected] of replacing fossil fuels? Can chemistry create a more peaceful world. Our

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Ü These are not the final page numbers! Angewandte Chemie generation will ultimately be defined by 100% in the 1980s and to 120% in ever, even the most educated people of how we live up to the energy challenge. 1999.[5] This statistic simply means that developed countries do not care much we are living above our possibilities. about its importance. There is indeed a Furthermore, we make extensive use of big disproportion between the extensive “Our generation will ultimately resources that cannot be regenerated by be defined by how we live up to the biosphere. This is not only the case of fossil fuels, that are irremediably “There is big disproportion the energy challenge.” consumed when used, but also that of between the extensive use we metals.[6] Clearly, spaceship Earth has a limited carrying capacity. It has been make of energy and the scarce An Unsustainable Growth in an calculated that if all the worlds 6.5 bil- knowledge we have of it.” Unequal World lion inhabitants were to live at current North American ecological standards, “My grandmother used to say: there are we should look around for another two but two families in the world, have-much Earths to accommodate them.[5] Of use we make of energy and the scarce and have-little.” course also Europe is heavily contribu- knowledge we have of it. This situation Miguel de Cervantes, Don Quixote ting to unsustainable Earth exploitation: is not good for a society willing to European terrestrial biosphere absorbs become knowledge-based as Europe is Energy is the number one but, by no only 10% of Europes anthropogenic supposed to do.[8] [7] means, the unique problem for human- CO2 production. If you ask simple questions to com- ity. Food, water, health, environment, mon people, for example, How energy is education, population, war, democracy produced? How much energy do you are other important problems. It can be Known and Hidden Costs of consume? What is the cost of electric- noted that all of them, perhaps except Energy ity? How can you save energy? you will for democracy, are strictly dependent on most likely get poor answers. As educa- the availability of energy.[4] It is easy to “The struggle for existence is the struggle tors we should ask ourselves: how understand that a hospital consumes a for available energy” energy is taught in our schools and huge quantity of energy. Perhaps it is Ludwig Boltzmann universities? more difficult to reckon the colossal In recent years the price of energy amount of energy embodied in and What is energy? The answer is not has substantially increased; the common consumed by a stealth bomber. Modern simple. We might apply to energy what belief is that energy is now extremely agriculture, which provides any kind of Saint Augustine argued about time expensive. But can we really complain? food and delicacies to Western consum- (Confessions, XI, 14): “What is time? If The current “high” price of the most ers, is one of the most energy intensive nobody asks me, I know; if I wish to valuable energy source, oil, is around human activities. For example, the en- explain to him who asks, I know not.” $70/barrel, that is, $0.44/liter. Hence, ergy of 7 liters of oil is needed to Energy is an ubiquitous entity look- crude oil is cheaper than some mineral produce 1 kg of beef. Some people say ing like heat, electricity, motion that, waters one can find on the supermarket that modern industrial agriculture is, in unnoticed, shapes and drives every sin- shelves. Currently, the cost of petrol in a fact, the use of land to turn oil and gas gle instant of our life (Figure 2). How- gas station in Europe (ca. E1.3LÀ1)is into food. Excluding the light coming from the Sun, the Earth is a closed system. The second law of thermodynamics states that, in a closed system, there are limitations that cannot be overcome; apparently, several economists are not acquainted with this simple principle. We must never forget that human economy vitally depends on the planets natural capital (e.g. oxygen, water, bio- diversity, etc). Fortunately, part of this capital is regenerated for free by the direct and indirect action of sunlight on the biosphere, but drawing on the natural capital beyond its regenerative Figure 2. The power at the disposal of energy-affluent people: to run a TV set the continuous capacity results in depletion of the muscular work of 2 people would be needed, while for a complete cycle with an energy-efficient capital stock. Humanitys load corre- washingmachine the number is increased to 15. To take-off a fully loaded Boeing747, sponded to 70% of the capacity of the 1.6 million “energy slaves” would be required. These examples give an idea of how much energy global biosphere in 1961, and grew to we use.

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lower than that of water in a restaurant. (Figure 3). Even in peace time there is a change are deprived people, as shown in Thus it is still cheaper for a car to drink gigantic security machine operating to the aftermath of Katrina in New Or- than for a human being.[9] safeguard key energy corridors and leans. In other words, affluent energy Our energy bonanza, however, facilities (pipelines, sea routes, refiner- consumers will mainly generate the comes at a price that is not paid directly ies, etc.) and these costs are not directly damage, the poor will suffer most. by individuals or by energy companies, charged on the oil barrel. but by the society as a whole in terms of Europe is leading the way to estab- socio-economic and environmental lish a scientifically sound account of Energy and Quality of Life damage. For instance, in Europe health energy externalities.[12] The European care for people injured by car accidents Union (EU) has recently estimated the “You can never get enough of what you (i.e., energy intensive transportation) is extra-cost of electricity production by don’t need to make you happy” paid with public money and this con- different sources. For example, electric- Eric Hoffer tributes to burden national budgets. The ity generated by coal in Germany im- hidden costs of energy (“externalities”) plies an extra cost of 0.73E cents per Energy is embodied in any type of deal with short term negative impacts kWh, that is, 10-times higher than wind goods and is needed to produce any kind related to the discovery, extraction, dis- energy.[13] From these and related data it of service. This is the reason why it takes tribution, and conversion of power re- becomes clear that, if externalities were energy to improve peoples standard of sources as well as long-term effects, such included in energy accounting, some living. Since more energy yields more as health damage arising from air-pollu- renewable technologies would be al- goods and more services, one could tion exposure.[10,11] Externalities are ready competitive with traditional tech- believe that the well-being of people probably the greatest taboo of the nologies on a purely economic basis. increases with increasing consumption energy puzzle. Some side-effects of en- Probably the heavier externality that of energy. This, however, is not always ergy consumptions are transmitted to big energy consumers are inflicting to all the case. The quality of life is highly future generations (e.g., nuclear waste); of the citizens of the world is the forcing correlated with energy consumption others, in the form of huge military costs of the carbon cycle that fosters global during basic economic development, related to securing energy supply, fur- warming. The amount of carbon we are but it is almost completely uncorrelated ther burden our society. In this regard it injecting in the air (ca. 7 Gt/year) looks once countries are industrialized.[11] little if compared to the naturally occur- ring exchange between the biosphere “Some side-effects of energy and the atmosphere (ca. 200 Gt/year). “The quality of life is almost consumption are transmitted However this is enough, on the long completely uncorrelated with term, to steadily increase CO2 concen- energy consumption once to future generations, others, tration (+ 30% since industrial revolu- burden our society.” tion), alter the Earths radiation bal- countries are industrialized.” ance, and trigger artificial climate var- iations that overlap with natural oscil- lations.[14] The most likely scenarios When the per capita energy consump- is sufficient to recall that the first imply an increase of extreme weather tion reaches a value of about 2.6 ton of Persian Gulf War (PGWI, 1990–1991) events, such as top scale hurricanes, oil equivalents (toe) per year there is no cost approximately $80billion, most droughts, heavy precipitations, heat further improvement. There is in fact a likely a tiny value if compared to the waves. Of course, the most exposed to strict parallelism between overcon- unknown cost of the ongoing PGW II the “external” effects related to climate- sumption of energy and food. The nation with the highest number of over- weight or obese people (USA: 130mil- lion, or 64%) is also the one with the highest energy consumption per capita (8 toe per year). An American consumes as much energy as 2 European, 10Chinese, 20Indian, or 30African people.[11] Calories are both biologically and socially healthy only as long as they stay within the narrow range that sepa- rates enough from too much.[15] Over a definite threshold, energy inputs increase inefficiency of personal life (obe- sity) as well as of social life (traffic jams), cause more waste, boost medical Figure 3. The so-called “energy strategic ellipse”, an area stretching from Arabian Peninsula to expenses and, last but not least, increase Western Siberia, where about 70% of the world’s proven oil and gas reserves are concentrated. inequality.

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As soon as a black-out takes place in Our oil-addicted civilization is going gasification and carbon sequestration a country, for whatever reason, the to face a problem that might change the underground. The latter technology, solution proposed by most politicians energy scenario dramatically, the so- that aims at capturing CO2 from sta- and economists is that of making new called oil peak.[18] Starting from early tionary sources (e.g., power plant flue power plants. This, for example, was the 20th century the demand of oil has gases) thereby preventing its release in case for the nationwide black-out that steadily increased and the supply has the atmosphere, encounters a wealth of occurred in Italy on a Saturday night in always been able to cope with such a environmental, technical, economical, September 2003, when the power de- demand: we needed more oil and we and political obstacles.[21,22] Coal has mand was less than 30% of the national extracted it easily. There will come a another significant drawback: in many capacity production. The wisest decision time, however, in which the supply will cases it requires someone digging it to take in front of any “energy crisis” in not be able to satisfy the ever increasing underground, which is not exactly the developed countries is not that of in- demand. That day the oil reserves will easiest job one can dream of. Probably, creasing energy supply, but that of not be exhausted, but the golden age of the lowest vocation rate for this career is reducing energy demand. It is not diffi- “easy oil” will be over. The pessimists found among the biggest energy con- cult to demonstrate that affluent coun- believe that we are now at the oil peak, sumers of affluent countries. tries can cut the energy consumption by the optimists[19] shift it 30years later. In conclusion, it is clear that, sooner 25% at virtually no sacrifice for peo- Actually, even if the latter are right, the or later, we will face an energy transition ple.[16] Since a substantial amount of the oil peak problem will not be moved too from fossil fuels to some kind of renew- consumed energy is embodied in indus- far away: after all, the babies today will able energy source (Figure 4),[23] be still young in 30years time. Oil is the ideal fuel since, being “The wisest decision to take in liquid, it is easy to extract and transport. any energy crisis in developed For some applications oil is practically impossible to replace: can we conceive countries is that of reducing to run a Boeing-747 Jumbo Jet with solid energy demand.” or gas fuels? The gas peak is expected to occur later than oil peak. However, the short- trial products, avoiding production of age in the supply of Russian natural gas useless things and increasing the lifetime to Europe in winter 2006 has shown that of products would save a lot of energy. the distribution infrastructure of this Unfortunately this goal does not fit valuable energy source is rigid and with the mantra of endless economic fragile. We should also consider that in growth. the future a substantial share of Russian gas could take the direction south to developing Asian countries. The distri- Fossil Fuels bution problem can be limited, in principle, by building liquid natural gas “Is fossil solar energy the only one that (LNG) tankers and regasification termi- may be used in modern life civiliza- nals. These infrastructures, however, are tion? That is the question” extremely expensive and imply severe Giacomo Ciamician security issues. This is probably the reason why most California LNG termi- Figure 4. The famous paper “The Photochemis- try of the Future” also published in Science by Oil is the most valuable commodity nals were built off the Mexican coast.[20] Giacomo Ciamician in 1912 (ref. [23]), where in world trade. It can be estimated that, The risk of accident is limited, but … he pointed out the need for an energy transi- at current prices, roughly six billion you never know. tion from fossils to renewables. One century dollars a day change hands in worldwide Coal is the most abundant and dirt- later this call is more urgent than ever. petroleum transactions.[17] We currently iest of fossil fuels. Basically, the problem consume 85 million barrels of oil a day of coal in the next 100 years is not and demand is growing mainly as a availability, but environmental sustain- Nuclear Energy result of increasing car ownership in ability. Just to give a visual impression, a Asian countries. If China and India, with standard 1000 MW plant consumes a “The nuclear power industry remains as now less than 20 cars for 1000 people, 100-trainloads of coal a day. The trend in safe as a chocolate factory” should reach the car saturation level of the use of the most greenhouse-inten- The Economist, March 29th 1986 (4 weeks European countries (about 700 cars per sive fuel is in conflict with ongoing before the Chernobyl catastrophe) 1000 people), their automotive fleet efforts for a world-scale climate policy. would need 28 million barrels of oil a In the hope to mitigate the climate Nuclear energy can be obtained by day, that is, almost three times the impact of coal, considerable resources fission or fusion. While fission is largely current production of Saudi Arabia. are being invested on projects for coal used to produce electrical energy, fusion

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is still at the level of preliminary labo- it is questionable if any nuclear plants would render developing countries ratory experiments[24] (except for would have been constructed in the U.S. heavily depend on foreign technology bombs). The most technically advanced without this support.[10] and their political freedom could be nations have recently joined to launch a To contribute significantly to our substantially compromised. project called ITER that should demon- future energy needs, nuclear energy strate by 2050 the possibility to use should provide 10TW of power for an nuclear fusion for civil purposes. It is extended period of time. Production of Solar Energy difficult to forecast whether this project, such a large amount of energy would which is extremely complex and very require 10000 one-gigawatt-electric (1- “Life is a water mill: the effect produced E expensive (about 10billion , which GWe) nuclear fission plants which by the falling water means approximately 2 E for each per- means that a new power plant should is achieved by the rays of the sun. son on the Earth) will be successful. be constructed somewhere every other Without the sun the wheel of life cannot Presently there are 441 operating day for the next 50years. [27,28] Once that be kept going. fission power plants in the world. In level of deployment was reached, the But we have to investigate more closely the next few years this number will terrestrial uranium resource base would which circumstances and laws of Nature likely decrease because, while waiting be exhausted in 10years. Spent fuel bring about this remarkable transfor- for new planning and regulation clear- should then be reprocessed and breeder mation ance, the 26 plants that are now under reactor technology should be developed of the sunrays into food and warmth.” construction will hardly replace the old- and disseminated to countries wishing to Wilhelm Ostwald est reactors close to decommissioning.[25] meet their additional energy demand in Development of fission nuclear energy this way.[29] Conventional fuel reprocess- As mentioned before, spaceship faces a number of difficulties. In princi- ing, however, requires the separation of Earth is a closed system. We are lucky, ple, modern reactors are safe, but people plutonium from radioactive material, however, to have an inexhaustible en- cannot forget the Chernobyl accident, making much easier plutonium stealing ergy flow coming from the sun and whose terrible material and psycholog- for atomic weapons. The Bush admin- deposited on the surface of the Earth: ical consequences are still difficult to istration has recently asked Congress to 120000 TW of electromagnetic radia- evaluate. The problem of safe disposal provide $40billion start-up funding for tion. It is a quantity of energy far of nuclear waste has not yet been solved an ambitious program called Global exceeding human needs. Covering even in the United States, in spite of the Nuclear Energy Partnership (GNEP) 0.16% of the land of the Earth with huge effort to construct a national that aims at launching an improved 10% efficient solar conversion systems deposit in the Yucca Mountain,[26] nuclear recycling process.[29] If the proj- would provide 20TW of power (Fig- whereas leaving nuclear deposits radio- ect were successful, by 2025 the U.S. and ure 5),[30] nearly twice the worlds con- active for thousands of years to future its partners would provide fresh nuclear sumption rate of fossil energy and the

generations raises moral concern. Civil fuel and small nuclear reactors to devel- equivalent of 20000 1-GWe nuclear nuclear energy is tightly and ambigu- oping nations. In return, these user fission plants. ously linked with weaponry technology nations would agree not to build urani- Solar energy has enormous potential (see the current Iran affair) and prolif- um enrichment and to give back spent as a clean, abundant, and economical eration of nuclear weapons is the last fuels to the original supplier for reproc- energy source, but cannot be employed thing we need on our fragile spaceship essing. This kind of initiative, however, as such; it must be captured and con- Earth. Nuclear plants are primary targets for terrorists and are hugely expensive to build, safeguard, and decommis- sion.

“Civil nuclear energy is tightly and ambiguously linked with weaponry technology.”

The development of nuclear energy has been heavily subsidized in different ways. In U.S., for example, the Price– Anderson act poses a cap of $200 million on the cost of private insurance, that would otherwise be prohibitive. When Figure 5. The production of 20 TW of power, the world’s mid-century projected demand, would required, resources are ultimately pro- require covering0.16% of Earth’s land (red squares) with 10%-efficient solar panels (courtesy vided by taxpayers. Observers note that of Prof. Nathan Lewis, Caltech, Pasadena).

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Ü These are not the final page numbers! Angewandte Chemie verted into useful forms of energy. Since ment (grid-connected PV systems). solar energy is diffuse (ca. 170Wm À2) “Over 50% of energy use in From 2002 to 2004, grid-connected solar and intermittent, conversion should in- modern houses is spent in photovoltaics grew by 60% per year, to volve concentration and storage. Cur- cover more than 400000 rooftops (of rently, none of the many routes used to warm up water for heating, which 200000 in Japan, and 150000 in convert solar energy into heat, electric- washing, and cooking.” Germany).[31] ity, and fuel is competitive with fossil In conventional PV cells electrons fuels at todays world market price. and holes created by absorption of However, if the “external” costs of photons with energies above the semi- energy from fossil fuels were consid- around the world, lead by Barcelona conductor band gap lose their excess ered, the cost comparison would give and Oxford, have enacted ordinances energy as heat. The thermodynamic quite different results. requiring solar thermal systems in new limit for energy conversion efficiency Some scientists believe that in the buildings, with very significant results. under these conditions is 31%. In prin- future it will be possible to collect An important improvement of solar ciple, this limit can be overcome by energy from the space by solar power thermal conversion would be to con- second-generation systems made of satellites (SPS) and then send micro- struct systems capable of accumulating semiconductor p–n junctions arranged wave power beams back to Earth. We heat during the day, storing it in an in tandem configuration (multijunction will not consider these futuristic appli- embedded phase transition, and release solar cells).[28] cations in the following. it in a controlled manner. The most common, first-generation The Suns energy can also be con- PV cells, consisting of single-crystalline verted into high-temperature heat by silicon, have efficiencies between 5 and Solar Thermal Conversion using mirrors to concentrate the radia- 15%, a lifetime of about 30years and a tion. Once the sunlight is concentrated, cost for grid-connected electricity of The most broad-scale way of making heat can be converted into electricity by about 0.20–0.40 $/kWh, to be compared use of solar energy is that of solar heat engines or used for thermochem- to electric grid supplies from fossil fuels, thermal collectors, in which a liquid is ical processes such as methane reform- which vary between 0.03 (off-peak, heated to supply hot water for direct use ing and metal oxide reduction.[28] After a developed country) and 0.80 $/kWh or home heating. These systems are very stagnant period which lasted until a few (rural electrification).[31] The energy simple and do not need sunlight con- years ago, high-temperature solar ther- payback time of a solar cell is of the centration. The market for solar thermal mal systems have recently regained order of 2–4 years and in its lifetime a collectors grew some 50% between 2001 interest. Spains market is emerging cell may produce electricity with a value and 2004. The EU accounts for 13% and some developing countries have of something in the order of 10times its (1.6 million square meters installed in planned projects.[31] Breakthrough di- cost of production.[28] Total world cumu- 2004).[31] The highest density of solar rections are materials that can withstand lated installed capacity of PV amounted thermal systems is in Israel (740m 2 per the high temperatures and corrosive to 1.8 GW in 2004.[31] 1000 inhabitants; in Germany, it is ten- chemical environments in solar furna- Solar electricity is already cost-com- times less), where most buildings are ces. petitive with fossil and nuclear electric- required by law to have solar hot-water ity if externalities are taken into consid- collectors. The 110million square me- eration. Furthermore, it can reasonably ters of installed collector area (77 ther- Solar Electricity be expected that an intense research mal gigawatts, GWth, of heat production effort in this field will produce new capacity) worldwide correspond to al- Solar electricity can be produced concepts, designs, materials, and tech- most 40million households, about 2.5% from photovoltaic (PV) cells and related nologies capable of increasing cell effi- of the roughly 1.6 billion households devices, or from high-temperature sys- ciency and reducing cost. that exist worldwide.[31] It is important tems. The first method is by far the most During the past decade, solid-state to point out that, contrary to common promising for diffuse electricity produc- PV cells based on molecular-based or- perception, over 50% of energy use in tion. PV cells have many applications. ganic systems like those used in video modern houses is spent in the most They are particularly well suited to display technology have been devel- trivial fashion: warm up water for heat- situations where electrical power from oped. Their energy conversion efficien- ing, washing, and cooking. Hence wide the grid is unavailable. About 1.6 billion cy is still low (less than 5%), but they diffusion of solar thermal conversion people still do not have access to offer great potential for construction of would substantially alleviate the energy electricity and a substantial portion of low-cost, lightweight, large-area, flexi- and environmental bill of the residential the worlds poor lives in areas where the ble solar cells. The development of high- sector. cost of extending the electric grid is efficiency organic solar cells could lead It has been estimated that in 2004 prohibitive. In developed countries, so- to solar conversion paints that would the use of solar energy in the place of lar cells (in the form of modules or solar allow extensive capture and conversion fossil fuels to obtain hot water has panels) on building roofs can be con- of solar energy.[28] avoided production of 25–30million nected through an inverter to the elec- Solar energy can be converted into tons of CO2. A number of major cities tricity grid in a net metering arrange- electrical power also by photoelectro-

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chemical cells based on a semiconductor electrode in contact with an electrolyte containing an electron relay. The most stable, and therefore most used semi-

conductor is TiO2 which, however, does not absorb much of the sunlight because its band gap is too high (3.0eV, ca. 410nm). To overcome this problem, dye molecules are adsorbed onto thin films of sintered nanocrystalline particles of [32] TiO2. The dye molecules, when excited by sunlight, inject electrons into the

TiO2, producing the charge-separation process. These dye-sensitized solar cells are attractive because of the low cost of

TiO2 and the potential simplicity of their manufacturing process. Laboratory scale devices of 11% efficiency have been demonstrated, but larger modules Figure 6. A very simplified sketch representingkey processes in natural photosynthesis: solar are much less efficient. light harvesting by pigments, energy transfer to the reaction center, charge separation, production of carbohydrates and oxygen (courtesy of Dr. Lella Serroni, University of Messina). D donor, A acceptor, P photosensitizer. Solar Fuels

Liquid fuels are the best form of tation energy is then transferred to transfer steps, to catalytic sites, where energy since they can be stored and reaction center (RC) proteins, where it they are used to oxidize water and transported. Because of the intermittent is converted by an excited-state elec- produce fuels, such as carbohydrates. nature of solar energy, its conversion tron-transfer process into electrochem- Artificial photosynthesis: The need into useful chemical fuels is even more ical potential energy. The quantum effi- and possibility to achieve artificial pho- advisable. Solar electricity can be con- ciency of the charge-separation process tosynthesis[34] was anticipated by the verted into chemical fuels through the is close to 100%. The resulting oxidizing Italian chemist Giacomo Ciamician [23] electrolysis of water to produce H2 and and reducing equivalents are then trans- (Figure 7) about one century ago:

O2, but it is a very expensive method. ported, by subsequent thermal electron- “Where vegetation is rich, photochemis- Therefore, direct production of fuels from sunlight (perhaps including meth- anol)[33] would be much more advanta- geous. Natural photosynthesis: Natural photosynthesis converts sunlight into fuels, producing biomass and, over geo- logical time, fossil fuels. Fossil fuel production rate, however, is about 500,000-times slower than our current consumption rates. The maximum potential photosynthetic conversion of sunlight to chemical energy is about 6.7%, but only a fraction of this is realized. Globally, only 0.3% of the solar energy falling on land is stored in plant matter, and only a fraction of this can be harvested.[11] Improving upon the efficiency of natural photosynthesis would of course be a very important result. To reach this goal, elucidation of the molecular basis of the overall process is essential (Figure 6). In photosynthetic organisms, light is harvested by Figure 7. Giacomo Ciamician, pioneer of photochemistry and prophet of the energy transition, antenna systems consisting of pigment- while watchinghis flasks under solar irradiation on the roof of his laboratory at the University of protein complexes. The captured exci- Bologna, Italy, circa 1910.

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Ü These are not the final page numbers! Angewandte Chemie try may be left to the plants and, by by charge transport to deliver the oxi- Fuels from biomass: Biomass has rational cultivation, solar radiation may dizing and reducing equivalents to cata- been, and continues to be, an important be used for industrial purposes.In the lytic sites where oxygen evolution and resource for energy production partic- desert regions, unsuitable to any kind of hydrogen evolution (or CO2 reduction) ularly in developing countries where it is cultivation, photochemistry will artifi- should separately occur. While some often used to provide energy in small- cially put their solar energy to practical progress has been made on each aspect scale industries and more generally as uses.On the arid lands there will spring of artificial photosynthesis, integration fuel-wood in stoves causing severe up industrial colonies without smoke and of the various components in a working health problems.[40] Substantial energy without smokestacks; forests of glass system has not yet been achieved (Fig- production from biomass requires very tubes will extend over the plants and ure 8).[37] large areas of cultivable land, and huge glass buildings will rise everywhere; in- Difficulties arise because formation amounts of water. It has been estimated side of these will take place the photo- of hydrogen and oxygen from water (as that, at current consumption rate, the chemical processes that hitherto have well as reduction of CO2) are multi- substitution of a mere 5% of gasoline been the guarded secret of the plants, electron processes, whereas light ab- and diesel fuels for Europe and U.S. but that will have been mastered by sorption is a one-photon process that would claim about 20% of their culti- human industry which will know how results in a one-electron charge-separa- vable land.[41] to make them bear even more abundant tion process. Therefore catalysts are In the industrial countries, biomass fruit than nature, for nature is not in a necessary to couple single photon events is employed to produce heat and elec- hurry and mankind is.And if in a distant to processes capable of accumulating tricity using mainly solid biomass, or to future the supply of coal becomes com- the redox equivalents needed for fuel obtain liquid fuels, such as ethanol and pletely exhausted, civilization will not be production. Efficient catalysts, particu- biodiesel, from crops (33 billion liters in checked by that, for life and civilization larly for oxygen generation, however, 2004, about 3% of the 1200 billion liters will continue as long as the sun shines!”. have not yet been found. The recent of gasoline consumed globally).[31] Eth- The efficient production of clean discovery of the structure of the oxygen anol is extracted from sugarcane in solar fuels would indeed represent the evolving center of natural photosynthe- Brazil and from corn in the U.S. The most important breakthrough of mod- sis[38] may help in designing efficient Brazil cane–ethanol system converts ern science. Although this task presents artificial catalytic systems. 33% of the harvested primary energy many scientific challenges, some results More successful has been the study into ethanol[42] providing, in 2004, 44% so far obtained are encouraging.[35] of hybrid natural–artificial systems, for of all (non-diesel) motor-vehicle fuel example, the construction of a proton consumed as pure ethanol (E95) or a pump using an artificial donor–acceptor 25%-ethanol/75% gasoline blend triad and ATP synthase incorporated in (E25). More than half of all new cars “The efficient production of a liposome.[39] sold in Brazil are flexible-fuel vehicles clean solar fuels would represent the most important breakthrough of modern science.”

For solar fuel production to be economically and environmentally attractive, the fuels must be formed from abundant, inexpensive raw materials such as water and carbon dioxide. Water should be split into molecular hydrogen and molecular oxygen,[36] and carbon dioxide in aqueous solution should be reduced to ethanol with the concomitant generation of dioxygen. These are the two reactions on which research is presently focused. The best way to construct artificial photosynthetic systems for the practical production of solar fuels is that of mimicking the molecular and supramolecular organi- Figure 8. A very simplified sketch representingkey processes in artificial photosynthesis: solar zation of the natural photosynthetic light harvesting by molecular antennas, energy transfer to a reaction center, charge separation, process: light harvesting should lead to water splitting with production of hydrogen and oxygen on the two sides of a membrane charge separation, that must be followed (adapted from ref [37]).

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that run with pure ethanol or the stronger competitor for traditional tech- other mode of electricity production; ethanol/gasoline blend. Use of ethanol nologies. Disadvantages are related to 2) easy harvesting of potential energy as E85 and E10blends (that is 85% or the natural variability of winds, the for peak electricity demand, available 10% ethanol) is increasing in the U.S., distance between wind farms and con- within seconds; 3) reliable supply of where the corn–ethanol system is re- sumption centers, and aesthetic and irrigation and drinking water; 4) protec- ported to convert 54% of the harvested ecological objections. The total amount tion against recurrent, and sometimes primary energy.[43] Mandates for blend- of globally extractable wind power has destructive, floods. In principle the [30] ing biofuels into vehicle fuels have been been estimated to be 2–6 TWe. Earth untapped hydro potential is sim- appearing in several countries including The wind-power market is concen- ply huge, however only a small fraction India and China. In Europe, several trated in a few primary countries, with of it can be utilized in a sustainable countries produce biodiesel and provide Spain, Germany, India, U.S., and Italy fashion from an economic and environ- tax exemption for this fuel. In Germany, leading expansion in 2004, but new mental standpoint. According to recent biodiesel production grow by 50% in large-scale commercial markets are tak- estimates, the remaining exploitable 2004. EU has a biofuels target of 5.75% ing the first steps in several countries hydroelectric resource is less than for 2010. Notably, the net energy gain in such as Russia, China, and Brazil. The 0.5 TW.[28] the production of biodiesel from soy- wind-power industry produced more As far as Europe is concerned, the beans is substantially higher than that of than 6000 wind turbines in 2004, at an potential for new big hydroelectric bioethanol from corn.[44] average size of 1.25 MW each.[31] Ac- plants is minimal, but small size and Current research directions on bio- cording to the European Wind Energy widely distributed facilities can give a mass focus on 1) increasing cellulose-to- Association,[46] by the end of the current significant contribution to tomorrows sugar conversion for the production of decade 75000 MW of wind turbines will energy mix. This situation is also true for ethanol,[16, 45] and 2) gasification technol- be installed in Europe, able to satisfy the developing countries where tens of mil- ogies to produce synthesis-gas (syngas), residential electricity need of almost lions of rural homes already receive

a mixture of CO and H2 for use in fuel- 200 million European citizens. The vast power from small hydroelectric plants, forming reactions.[28] European wind-energy potential, in mostly in China.[16,31] principle, would be able to satisfy all our electricity needs. Wind, Hydro, and Other Renew- Other Renewables ables Hydroelectric Energy Mother nature donates us a few “Praised be You my Lord with all Your other options to draw energy from our creatures, Hydrogeneration is one of the oldest Earth spaceship. The most important of especially Sir Brother Sun, technologies for electricity production, these is probably geothermal energy, Who brings the day and through whom thus it is easier to evaluate advantages related to the heat stored in the depths You give us light. and disadvantages.[16] Among the latter, of our progressively cooling planet. In And he is beautiful and radiant with invasivity comes first. The land occupied some selected areas, as demonstrated in great splendor. by the world hydroelectric infrastruc- Italy over a century ago, underground Praised be you, my Lord, through ture is estimated to be roughly thermal energy can be extracted and Brother Wind, 300000 km2 (approximately the area of used as heat or converted into electric- Praised be You, my Lord, through Sister Italy), although hydroelectric plants ity. Geothermal direct-heat utilization Water, provide just 3% of world total primary capacity has nearly doubled from 2000 [47] Praised be You, my Lord, through Sister energy supply (TPES). The construc- to 2005 (13 GWth increase), with at least Mother Earth,” tion of big dams has caused the forced 13 countries using geothermal heat for Saint Francis, Canticle of the Creatures displacement of 40-to-80 million (usual- the first time.[31] The total geothermal ly poor) people in developing countries energy at the surface of the Earth, Wind during the 20th century, with unaccount- integrated over all the land area of the able social and economic penalties. continents, is 12 TW, of which only a Producing electricity by wind im- Reservoirs have often inundated ar- small fraction could practically be ex- plies a number of hard-to-rival advan- cheological sites as well as many unique tracted. The global potential electric tages such as 1) guaranteed perpetual natural ecosystems and life in down- energy generated in this way could cover zero cost of the primary “fuel”; 2) no stream rivers (e.g., the Colorado) has 3–5% of current consumption, which is emissions in the atmosphere or heat to often been dramatically affected. Re- certainly interesting especially for re- dissipate; 3) a relatively simple technol- cently it has also been shown that water gions of the planet where exploiting ogy; 4) short times of construction and reservoirs can be significant sources of geothermal energy is practical.[16]

wide tunability of installed capacity CO2 and CH4 from decaying vegetation. Other, minor energy resources could from a few kW to hundreds of MW. Despite these drawbacks, hydroelectric be obtained by taking advantage of the Inevitably, the price of wind-made elec- power exhibits many important advan- ocean and lake temperature gradients, tricity will continue to decrease on the tages such as 1) the lowest operating currents, and waves, while the Earth– long term, making it a stronger and cost and a longer plant lifetime than any Moon gravitational energy can be ex-

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Ü These are not the final page numbers! Angewandte Chemie ploited in some selected coastal areas of hydrogen economy will not occur soon Growth and Potential of the northern hemisphere where tides and might also not occur at all unless a Renewable Energies move large volumes of sea water in a large research effort is set up to over- relatively short time. The cumulative come several scientific and technologi- “The only way to discover the limits of energy in all tides and ocean currents in cal obstacles.[49–52] the possible is to go beyond them into the world amounts to less than 2 TW. Combustion of molecular hydrogen, the impossible” However, in our quest for an increas- H2, with oxygen produces heat and Arthur C. Clarke ingly diversified energy portfolio, they water, and combination of molecular must be carefully considered, especially hydrogen and oxygen in a fuel cell In the last few years, the use of on the local scale. A recent interesting generates electricity, heat, and water. renewable energies has grown rapidly. example is the use of the deep cold Clearly, if hydrogen could promptly From 2000 to 2004, the average annual waters of Lake Ontario to provide air- replace oil, both the energy and the growth rate was: grid-connected solar conditioning to thousands of Torontos environmental problems of our planet PV 60%, wind power 28%, biodiesel offices and houses.[48] would have been solved. Unfortunately, 25%, solar hot water/heating 17%, off- however, there is no molecular hydro- grid solar PV 17%, geothermal heat gen on the Earth. Molecular hydrogen capacity 13%, and ethanol 11%.[31] Such The Hydrogen Economy cannot be “mined”, but it has to be a generalized increase in all the fields of “manufactured”, starting from hydro- renewable energies is very important ““I believe that water will one day be gen rich compounds, by using energy. since it allows each country to construct employed as fuel, that hydrogen and Therefore, hydrogen is not an alterna- a diversified energy portfolio. oxygen which constitute it, used singly or tive fuel, but a secondary form of Solar water heaters are fully com- together, will furnish an inexhaustible energy. This is the central (but not petitive with conventional water heat- source of heat and light, of an intensity of unique) problem of hydrogen economy. ers; ethanol in Brazil is competitive with which coal is not capable … . Water will Like electricity, hydrogen must be pro- gasoline; hydro, geothermal, and some be the coal of the future”” duced by using fossil, nuclear, or renew- forms of biomass power generation are Jules Verne, The Mysterious Island able energy and then it can be used as an already competitive with power from energy vector, with the advantage, with fossil fuels (2–4 $cents/kWh) and nucle- According to media and press it respect to electricity, that it can be ar energy 4–6 $cents/kWh; wind power seems that the energy problem will stored. is competitive at good sites, and solar shortly be solved by hydrogen (Fig- Although a proper use of hydrogen PV power is expected to become com- ure 9), that sometimes is described as a is not expected to cause big environ- petitive before 2010 even in developed fuel obtainable for free from water. mental problems, one cannot say that countries at high insolation regions. hydrogen is a “clean” form of energy. In While waiting for progress in solar- fact, hydrogen is “clean” or “dirty” fuel production, solar thermal and solar depending of the primary energy form electricity can already supply a notice- used to produce it. Hydrogen obtained able amount of energy. Chinas target by spending fossil fuels or nuclear en- for solar thermal is to reach 230million ergy incorporates all the problems of square meters by 2015, more than twice using those primary energy sources. the amount of worldwide collectors to- Burning fossil fuels in remote regions day. Solar thermal conversion can in- to produce hydrogen as a clean fuel for deed replace much of the heat now metropolitan areas would be an ineffec- supplied by burning fossil fuels and tive solution, owing to the transboun- biomass. dary nature of atmospheric pollution.[53] Solar electricity can be profitably Figure 9. A hydrogen fuel-cell bus in Iceland. The water splittingand recombination reac- Clearly, clean hydrogen can only be exploited in developing as well as de- tions are figuratively represented by the open- obtained by exploiting renewable ener- veloped countries. By 2005, more than ingand closingof the door. gies, and this can be done, in principle, 2 million households in developing through the intermediate production of countries have received electricity from electricity (e.g., by wind or photovoltaic solar home systems. An idea of how Policy-makers have strongly biased cells) followed by water electrolysis, or necessary development in this field is opinions on the hydrogen issue.[49] Most by photochemical water splitting. and how huge this market is, comes from scientists believe that the shift to a the estimate that 350million households worldwide do not have access to central power networks. The spreading of de- “According the media it seems centralized electricity generation sys- that the energy problem will tems could eliminate the need to build up an extensive and costly transmission shortly be solved by hydrogen.” grid, in the same way as mobile tele- communications has allowed the leap-

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frogging of cabled telephone lines in water industry, 130000 jobs in Germany ence,[57] research aimed at solving the some developing regions of the world. from all renewables, and 15000 jobs in energy problem will also lead to abun- In some developed countries, de- the European wind industry.[31] Detailed dant positive outcomes in other fields. mand for grid-connected PV systems studies are available on the estimation outstrips production. Solar PV is indeed of direct jobs that can be created by the one of the worlds fastest growing, most development of the various kinds of Answers to Fundamental profitable industries. Chinese module renewables. Questions production capacity doubled during There is strong evidence that solar 2004. Indias primary solar PV manu- and other renewable energies can take “Better to expect the foreseeable than be facturer expanded production capacity off with great benefit for people and the caught out by the unexpected” from 8 MW in 2001 to 38 MW in 2004. environment. Policy can play a funda- AndrØ Isaac Large production is expected from new mental role to support this develop- plants installed in the Philippines, Thai- ment. Key points are durability and At the beginning of this essay we land, and other countries. Substantial, reliability of political support and direct pointed out that the energy problem is but not sufficient, increase in production involvement of local authorities. A vari- entwined with many other social issues, is taking place also in Europe, where at ety of renewable-energy promotion pol- and that we need to know the answers to the end of 2004 the top two producers icies have been adopted in farsighted several entangled questions before tak- were QCell in Germany (75 MW) and countries. ing decisions that could heavily affect Isofoton in Spain (53 MW).[31] In spite of such a fast growth, the our lives and, even more so, those of our The harnessing wind energy is also contribution of renewable energy to the children and grandchildren. After the increasing worldwide. Considering the overall energy supply is still very low. above discussion, we are in the position current level of deployment of on-shore Renewables (excluding hydroelectric) to propose some answers that are, of and off-shore wind farms, especially in provide 0.5% of world TPES and 2% course, as much entangled as the corre- Europe, it is outdated to consider them of world electricity;[55] more than one sponding questions. as “alternative” energy stations. third of the latter share is produced in Can well-being, or even happiness, be In new buildings, solar thermal and Europe.[56] There is a need to accelerate identified with the highest amount of per- PV systems can be integrated and in- the development of renewable energies, capita energy consumption? NO. In- corporated into roof and walls. Blending but this acceleration can only be based crease in energy consumption helps of small wind turbines with PV and/or on scientific research. If suitable re- material development, but in developed solar heaters is also possible. Standar- search projects are launched and sup- countries it does not help people to dized “plug and play” full-scale house- ported, a wealth of more efficient and solve their nonmaterial problems. We hold off-grid PV systems are produced less expensive materials to construct have to change the paradigm that gov- and shipping containers with integrated systems for solar energy conversion into erns our energy policy. The energy crisis systems consisting of PV modules, small heat and electricity can reasonably be in a wealthy society cannot be over- turbines, and advanced batteries are also expected in a few years and production whelmed by increasing energy produc- available. Indeed, the sophistication of of solar fuels by artificial photosynthesis tion. To expand our happiness we should many segments of the renewable-energy is a likely achievement in the long run. make room for our nonmaterial values industry increases year by year. As pointed out by the Basic Energy and to human relationships. At least 48 countries worldwide, in- Science Workshop on Solar Energy Should we progressively stop burning cluding all 25 EU and 14 developing Utilization in April 2005,[28] research in fossil fuels? YES, for three important countries, have now some type of re- solar-energy conversion lies at the cross- reasons: 1) fossil fuels are a not renew- newable-energy promotion policy. For roads where physics, chemistry, and able energy source that is going to example, an European Solar Thermal biology meet nanoscience. Sciences exhaust; 2) use of fossil fuels causes Technology Platform has just been cre- greatest advances have always occurred severe problems to human health and ated to promote and ease the develop- on the frontiers, at the crossroads of irreversible damages to the environment of industries with high technolog- different disciplines, where the most ment; 3) fossil fuels should be preserved ical potential.[54] European renewable- profound questions are posed. Solving as raw material for the chemical indus- energy targets are 21% electricity and the energy problem is indeed a great try. Energy from fossil fuels should 12% total energy by 2010. Large com- question that needs to be tackled by an progressively be used only for creating mercial banks, venture-capital investors, interdisciplinary scientific effort. Since the conditions for a smooth transition and leading global companies are great questions often make good sci- toward the development of new energy strongly interested in renewable ener- sources. gies, whose growth is supported by at Can scientists find an energy source least 150marked facilitation organiza- “Research aimed at solving the capable of replacing fossil fuels? YES. tions. More than 1.7 million jobs have energy problem will also lead to There are two abundant energy sources, been estimated to be directly involved in solar energy (that broadly speaking renewable energies in 2004, including abundant positive outcomes in includes the other renewable energies) 400000 jobs in the Brazil ethanol indus- other fields.” and nuclear energy. These two forms of try, 250000 jobs in the China solar hot- energy are completely different not only

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Ü These are not the final page numbers! Angewandte Chemie for technical reasons, but also from the and development of related technolo- Will science and technology alone social viewpoint. gies can contribute to poverty allevia- take us to where we need to be in the next Nuclear energy obtained by the tion. few decades? NO. Even if science and presently available technology (fission) Can chemistry help in solving the technology will fully succeed in taking is neither clean nor inexhaustible. Fur- energy problem? YES. The three con- advantage of solar energy, we should thermore, it is a very concentrated form version routes of solar energy (solar never forget that spaceship Earth, ex- of energy that has to be produced under heat, solar electricity, solar fuel) require cept for solar energy, is a closed system strict technical, political, and military special materials and two of them in- and that we are already using the natural control because of its high capital cost, volve chemical processes. New material capital beyond its regenerative capacity. possible catastrophic accidents, difficul- systems, guided by the interplay be- Therefore, there is a need to reduce our ty to dispose wastes, misuse of nuclear tween rational design and experimental pressure on the Earth and to recycle material, proliferation of nuclear arma- screening, can greatly improve the per- resources as much as we can, especially ments. Development of nuclear energy formance of light absorbers, energy in view of population growth. We must will favor energy overuse, increase dis- converters, and energy-storing systems. become aware that the Earth is not an parities among rich and poor nations, Chemistry can play a key role in im- open place in which we live, but a closed and lead to a more fragile world. proving any kind of energy-related tech- system which we belong to and whose Solar energy is abundant and inex- nology and can even find novel solu- destiny we share.[59] haustible. It can be exploited all over the tions. Finding a breakthrough for solv- Should we, citizens of the western world by a variety of friendly, but still ing the energy crisis is indeed the “grand world, change our lifestyle and shift to relatively expensive technologies, some challenge” of chemistry.[27, 28,57] innovative social and economic para- of which are very simple. Solar energy is Will it be possible for all Earths digms? YES. We should change our a diluted and diffuse form of energy, inhabitants to reach the standard of living lifestyle for two reasons. First, the no- which can be transformed without fear- of developed countries without devastat- tion of endless economic expansion ing big accidents, misuse, and military ing the planet? NO. Even if, as expected, cannot be maintained because it contra- applications. Being not concentrated, the population growth will soon reach a dicts the second principle of thermody- solar energy will discourage energy plateau, there are not enough resources namics. Second, we know that our life- overuse and reduce pressure on the for all people to live at the level reached style, based on consumerism, increases consumption of the Earths other re- today by developed countries. To keep a disparities. sources; being diffuse all over the world decent level of life we will be forced to In affluent countries we live in (Figure 10), it will reduce disparities exploit sunlight for recycling the most societies where the concepts of among the worlds nations. Most poor important raw materials. “enough” and “too much” have been countries have abundant solar energy removed. At most, we agree on the need of increasing efficiency of energy consumption. Higher efficiency, however,

“In affluent countries the concepts of ’enough’ and ’too much’ have been removed.”

will not lead us towards the promised land of sustainability because not only is efficiency still consumption, but it can even increase consumption. For example, if we increase energy efficiency of some cars, consumers will presumably use the saved money to buy other items, perhaps more dangerous from a sustainability viewpoint (e.g., faster cars). To live in the third millennium, we need new thinking and new ways of perceiv- ing worlds problems. We need to overcome the logic of efficiency and enter a logic of sufficiency to attain ecological [60] Figure 10. Yearly sum of solar irradiation on horizontal surface in Europe in kWhmÀ2 ; there is stability. only a factor of 1.6 between the values for Rome and London (data from European Commission Can people of poor countries im- Joint Research Center). Isolated red dots are major metropolitan areas. prove their well-being? YES, they can.

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What is not clear is whether we wish to model of life ignores any limit, dissipates a necessary condition for a successful help. To contribute to this effort, we enormous amounts of resources, produ- society and prevents the construction of should change somewhat our lifestyle. ces huge quantities of waste, and causes a peaceful world. Indeed, the ultimate Between 2002 and 2030, consumption in an intolerable increase in disparity strategy to cope with the future is U.S./Canada is expected to increase by among the worlds nations. The second learning to say “enough”. Initially it 5.7 mbpd (million barrel of oil equiva- step is to launch, without any further may be difficult, but living on the Earth lent per day) as a result of a population delay, a massive and concerted plan for believing that there is no need for the increase of 88 million. By comparison, a research and development of renewable concept of “enough” is already quite population increase in India of 383 mil- energies. This is again a task of devel- risky and will clearly become impossible lion will be responsible for an additional oped countries where most of scientific in a few decades. Perhaps most people, 1.4 mbpd, or an increase in China of research is currently performed.[63] The including politicians, will understand 164 million will be responsible for an various forms of renewable energy this “enough” if explained by responsi- additional 1.5 mbpd.[61] should be carefully considered on the ble scientists. To diminish the huge disparity in local scale. As technology improves, it The energy crisis is a challenge, but, energy distribution among rich and poor will become easier for each community indeed, also an opportunity. It offers a one might propose to stop the growth in and each country to exploit the renew- precious chance to become more con- affluent countries while raising energy able energies available in its territory cerned about the world in which we live supply to poor countries. This is certain- and to have a more and more diversified and the society that we have construct- ly more realistic than imposing a de- energy portfolio. ed. It is actually an opportunity for crease of energy consumption among Political leaders of all nations should scientists to take an active role in rich. Unfortunately, however, this strat- put energy as the number one priority in protecting the Earth and helping to egy is inadequate because there are not the agenda. The way out of the fossil- change what is wrong in our social and enough resources on the planet for fueled civilization is indeed a global political organization, beginning with 6.5 billion energy voracious people. problem, bristling with difficulties. Since the huge disparity between the rich Any action to restore equity has thus it will take a long time, any further delay and the poor. We are well aware that to focus on lowering the standard of life will increase our responsibility towards the stability of human society decreases of the rich while attempting to raise that future generations. with increasing disparities. Ronald Rea- of the poor. Scientists have to provide the tech- gans trickle-down approach to the What we can do as scientists is help nological advancements to make energy developing countries to build their own transition a reality, but not only that. research capacity for generating appro- They have the moral duty to inform the “The Earth is in our hands. Are priate solutions to their specific prob- general public of the urgency and com- we capable of reducing dispar- lems involving energy resources, public plexity of the energy problem and they ity and creating a more peace- health, agriculture, ecology, and basic must speak up with politicians on a key education. Providing modern energy issue: the energy conundrum must be ful world?” services is crucial for the eradication of framed on a longer temporal perspec- extreme poverty as called for in the UN tive than that of political careers. Scien- Millennium Development Goals.[62] world problems does not work and, if things do not change, sooner or later the “Scientists have the moral duty poor will rise up against the rich. We try Conclusion to inform the general public of to set aside the problem of disparity, but the urgency and complexity of in the long run it cannot be eluded. The “If our black and nervous civilization, fragile spaceship Earth is in our hands. based on coal, shall be followed by a the energy problem.” Are we wise enough to develop, beside quieter civilization based on the utiliza- science and technology, a civilization tion of solar energy that will not be capable of reducing disparity and creat- harmful to progress and to human hap- tists, who are well aware of the conse- ing a more peaceful world? Besides wise piness” quences of the Second Principle of politicians, we need concerned scientists Giacomo Ciamician Thermodynamics, should also convince capable of knowing whether where we economists and politicians that sustain- are going is the right place for us to go. Prompt global action to solve the ability requires that we reject the notion Of course, new energy sources may energy crisis is needed. Such an action of endless economic expansion.[64] be found in the next decades, since should be incorporated in a more gen- Let us not forget that there is no science and technology will continue to eral strategy based on the consciousness renewable power source on Earth that advance. Nuclear fusion, if successfully that the Earths resources are limited. can beat our wastefulness and igno- exploited, could solve the energy prob- The first step of this strategy is to rance. Each nation, community, and lem at the root. Unfortunately, however, drastically reduce consumption of fossil even every single citizen should identify we cannot rely on what is presently fuels. This is a task that mainly concerns thresholds of real needs. Consuming unknown. Reducing energy consump- the affluent countries, where a wrong resources above such a threshold is not tion and using renewable energies are

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Ü These are not the final page numbers! Angewandte Chemie options already available. Someone may combined heat and power facilities [4] Though, curiously, nowadays a “war for find the expansion of solar technologies (CHP)[65] and shifting progressively to energy” is sometimes propagandized as unrealistic. In this regard, it is nice to solid-state lighting.[66] a “war for democracy”. [5] M. Wackernagel, N. B. Schulz, D. Deum- recall that horse traders laughed at the Renewable energies are fairly well ling, A. C. Linares, M. Jenkins, V. Kapos, first automobiles, shortly before going distributed all over the world, including C. Monfreda, J. Loh, N. Myers, R. out of business. “Mainstream forever”, Europe. As an average, solar power is Norgaard, J. Randers, Proc.Natl.Acad. namely new gas and oil explorations, only 1.5-times higher in Italy than in Sci.USA 2002, 99, 9266 – 9271. seems to be the most audacious recipe of Germany (Figure 10). Europe must [6] R. B. Gordon, M. Bertram, T. E. Grae- many analysts for the energy crisis. They strengthen its role as world leader in del, Proc.Natl.Acad.Sci.USA 2006, sound like dinosaurs in a world under renewable energies. Today we need to 103, 1209 – 1214. continuous evolution and are reminis- buy energy resources from other con- [7] I. A. Janssens, A. Freibauer, P. Ciais, P. Smith, G. J. Nabuurs, G. Folberth, B. cent of the 1970s information technol- tinents, tomorrow we must be able to Schlamadinger, R. W. A. Hutjes, R. ogy gurus, who did not even imagine the share and sell our energy know-how to Ceulemans, E. D. Schulze, R. Valentini, personal computer era. the rest of the world. Our European A. J. Dolman, Science 2003, 300, 1538 – We would like to close this Essay institutions give us the hope that this can 1542. with a few comments on the role of our be done in the framework of fairer [8] 2000 Lisbon European Council, Presi- continent, Europe. The EU regions international relationships than those dency Conclusions, can be found under enjoy the highest quality of life but are established during the present oil era. http://www.europarl.europa.eu/sum- mits/lis1_en.htm the poorest as far as conventional en- Europe must lead the way for a real, [56] [9] In affluent countries tap water is of ergy reserves are concerned. Oil pro- albeit gradual, structural economic re- excellent quality and very cheap. Never- duction in the North Sea peaked in late form: passing from the intensive use of theless, quite often, people prefer to 1990s and is now inexorably declining. non-renewable energy resources (fossil drink mineral water or soft drinks which Norway and Britain the greatest Euro- fuels) to the use of the abundant, inex- are as much as 1000 times more expen- pean oil producers, possess a mere 1.2% haustible, less harmful primary energy sive. This is a classical example of the of the worlds proven oil reserves. The source provided by the Sun. Our con- luxurious energy attitude of affluent societies: a lot of energy is consumed tinent has the intellectual, cultural, and to supply drinkable water to households, economic resources to lead this crucial which is mostly used to flush the toilet or “If a prompt action to energy endeavor. sprinkle the garden. On the other hand European universities have a most big energy investments are made to transition is needed for the important role in creating a new gener- bring a variety of drinks, sometimes world, it is simply imperative ation of conscious and responsible citi- abused and unhealthy, on our tables. for Europe.” zens who feel active members of soci- [10] D. M. Kammen, S. Pacca, Annu.Rev. Environ.Resour. 2004, 29, 301 – 344. ety,[67] according to the strategic objec- [11] V. Smil, Energy, Oneworld, Oxford, tive of the Council of Europe meeting in 2006. Lisbon (2000): “to become the worlds [12] See for example http://www.externe.in- combined gas reserves of Norway and most dynamic and competitive knowl- fo/ the Netherlands, account for just 2.1% edge-based economy capable of achiev- [13] European Commission, 2003, External of the total. The situation is not better ing a sustainable economic growth with Costs—Research Results on Socio-Envi- with coal, with Germany and Poland new and better jobs and a greater social ronmental Damages due to Electricity and Transport, can be found under holding 2.3% of the worlds recoverable cohesion”.[8] Values such as conscious- http://www.externe.info/externpr.pdf amount. It might sound distasteful to ness, compassion and care have to be the [14] R. A. Kerr, Science 2006, 311, 1698 – some nuclear energy supporters, who roots of such a knowledge-based econ- 1701. talk about “energy independence”, that omy. And if the diluted nature of solar [15] I. Illich, Energy and Equity, The Trinity not a single European region is listed energy will force us to substantially Press, London, 1974. among uranium and thorium reserve modify our way of living, this will not [16] V. Smil, Energy at the Crossroads, MIT holders. If a prompt action to energy necessarily mean that our lives will be Press, Cambridge, MA, 2003. transition is needed for the world, it is less enjoyable in a more peaceful world. [17] D. ORourke, S. Connolly, Annu.Rev. Environ.Resour. 2003, 28, 587 – 617. simply imperative for Europe. Certainly the existence of billions now [18] K. S. Deffeyes, Beyond Oil, Hill and Given the scarcity of conventional underprivileged will be better than right Wang, New York, 2005. energy resources, energy conservation is now. [19] P. W. Huber, M. P. Mills, The Bottomless mandatory for Europe: we must make Well, Basic Books, New York, 2005. use of our limited energy resources in a Published online: && &&, 2006 [20] P. Roberts, The End of Oil, Mariner smarter way. Just an example: to get one Books, Boston, 2004. unit of light service by using a traditional [21] S. Anderson, R. Newell, Annu.Rev. Environ.Resour. 2004, 29, 109 – 142. tungsten lamp, we feed a power station [1] M. R. Simmons, Twilight in the Desert, Wiley, Hoboken, NJ, 2005. [22] R. H. Socolow, Sci.Am. 2005, 293,49– with 100 units of primary energy, simply [2] P. Tertzakian, A Thousand Barrels a 55. wasting 99 units as heat in the electricity Second, McGraw-Hill, New York, 2006. [23] G. Ciamician, Science 1912, 36, 385 – production/transmission and in the bulb [3] R. A. Kerr, R. F. Service, Science 2005, 394. itself. We can perform better by using 309, 101. [24] W. E. Parkins, Science 2006, 311, 1380.

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[25] M. Inman, Science 2005, 309, 1170– [41] International Energy Agency, Biofuels [57] D. Kennedy, C. Norman, Science 2005, 1171. for transport—An international perspec- 309, 75. [26] J. Johnson, Chem.Eng.News 2005, tive, 2004, can be found under http:// [58] R. E. Smalley, MRS Bull. 2005, 30, 412 – 83(June 6), 32 – 34. www.iea.org/textbase/nppdf/free/2004/ 417. [27] R. Eisenberg, D. G. Nocera, Inorg. biofuels2004.pdf [59] R. W. Kates, Annu.Rev.Energ.Environ. Chem. 2006, 45, 6799 – 6801. [42] K. S. Kheshgi, R. C. Prince, G. Marland, 2001, 26, 1 – 26. [28] US Department of Energy Office of Annu.Rev.Environ.Resour. 2000, 25, [60] T. Princen, The Logic of Sufficiency, Science, Basic Research Needs for Solar 199 – 244. MIT Press, Cambridge, MA, 2005. Energy Utilization, 2005, can be found [43] For a recent assessment on energy [61] European Commission, Annex to the under http://www.er.doe.gov/bes/ return on energy investment for bioe- Green Paper—A European Strategy for reports/files/SEU_rpt.pdf thanol see R. Hammerschlag, Environ. Sustainable, Competitive and Secure En- [29] G. Hess, Chem.Eng.News 2006, 84- Sci.Technol. 2006, 40, 1744 – 1750. ergy, 2006. (March 27), 34 – 36. [44] J. Hill, E. Nelson, D. Tilman, S. Polasky, [62] See http://www.un.org/millenniumgoals/ [30] R. F. Service, Science 2005, 309, 548 – D. Tiffany, Proc.Natl.Acad.Sci.USA [63] D. King, Nature 2004, 430, 311 – 316. 103 551. 2006, , 11206 – 11210. [64] A reviewer has criticized this essay [45] G. Hess, Chem.Eng.News 2006, 84- [31] Worldwatch Institute, Washington, DC, stating that “It does illustrate the idea (March 6), 50– 56. 2005, Renewables 2005—Global Status that scientists should not be allowed to [46] European Wind Energy Association and Report, can be found under http:// write about economics or public policy: The European Commission, 2003, Wind www.worldwatch.org/press/news/2005/ they know a few of the words, but none Energy, the Facts.An Analysis of Wind 11/06/ of the music”. We wonder which words Energy in the EU-25, can be found under [32] M. Grtzel, Inorg.Chem. 2005, 44, and music the economists and politicians http://www.ewea.org/index.php?id = 91 6841 – 6851. know who insist on the need to increase [47] Note that a substantially smaller area, [33] G. A. Olah, A. Goeppert, G. K. S. Pra- 150000 km2, covered with 10%-efficient the gross domestic product (GDP) of kash, Beyond Oil and Gas: The Meth- photovoltaic panels would in principle developed countries when it is known anol Economy, Wiley-VCH, Weinheim, cover the current world total energy that this does not make people happier Germany, 2006. demand. (see, for example, D. Kahneman et al., [34] Artificial Photosynthesis (Eds.: A. Col- [48] See http://www.enwave.com/enwave/ Science 2006, 312, 1908 – 1910) and with- lings, C. Critchley), Wiley-VCH, Wein- [49] S. G. Chalk, J. Romm, M. Jacoby, Chem. out considering that increasing GDP heim, 2005. Eng.News 2005, 83(August 22), 30– 35. means increasing the consumption of [35] K. Maeda, K. Teramura, D. L. Lu, T. [50] N. Armaroli, V. Balzani, Energia Oggi e resources, mostly taken form poorer Takata, N. Saito, Y. Inoue, K. Domen, Domani, Bononia University Press, Bo- countries, and accumulation of waste Nature 2006, 440, 295. logna, 2004. that is immediately distributed to the [36] V. Balzani, L. Moggi, M. F. Manfrin, F. [51] R. Coontz, B. Hanson, Science 2004, 305, whole world (e.g. carbon dioxide) or Bolletta, M. Gleria, Science 1975, 189, 957. later directed to poor countries (e.g. 852 – 856. [52] U. Bossel, The Hydrogen Illusion, 2004 electronic waste). The mounting con- [37] V. Balzani, A. Credi, M. Venturi, Mo- can be found under http://www.efcf.com/ cern about the massive environmental lecular Devices and Machines, Chap.5 , reports/ degradation and related social unrest of Wiley-VCH, Weinheim, 2003. [53] H. Akimoto, Science 2003, 302, 1716 – the so-called worlds factory, China, [38] K. N. Ferreira, T. M. Iverson, K. Magh- 1719. should prompt deep reflections in this laoui, J. Barber, S. Iwata, Science 2004, [54] See http://www.esttp.org/cms/front_ regard. 303, 1831 – 1838. content.php [65] J. Johnson, Chem.Eng.News 2003, [39] G. Steinberg-Yfrach, J. L. Rigaud, E. N. [55] International Energy Agency, Key 81(October 6), 20– 23. Durantini, A. L. Moore, D. Gust, T. A. World Energy Statistics, 2005 can be [66] See for example http://www.olla-projec- Moore, Nature 1998, 392, 479 – 482. found under http://www.iea.org/dbtw- t.org [40] It is estimated that millions of people in wpd/Textbase/nppdf/free/2005/ [67] R. R. Ernst, Angew.Chem. 2003, 115, poor countries suffer from severe respi- key2005.pdf 4572 – 4578; Angew.Chem.Int.Ed. ratory problems arising from indoor air [56] US Energy Information Administration 2003, 42, 4434 – 4439. pollution generated by improperly vent- Database, which can be found under ed stoves fueled with biomass. http://www.eia.doe.gov/

16 www.angewandte.org 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2006, 45,2–17 Ü

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Essays

Renewable Energies Energy for everybody? The ever increas- ingworld energydemand cannot be N. Armaroli,* V. Balzani* &&&& — &&&& satisfied much longer with fossil fuels, alternatives are required to limit the The Future of Energy Supply: Challenges chance of a climate collapse and the and Opportunities spreadingof wars for natural resources. The 21st century will be largely defined by the way we face and resolve the energy crisis. This is an intricate and fascinating scientific challenge, in which chemistry will play a fundamental role, and also an unprecedented opportunity to shape a more peaceful world.

Angew. Chem. Int. Ed. 2006, 45, 2 –17 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.angewandte.org 17 These are not the final page numbers! Ü Ü