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Energy today and tomorrow. Excerpt from the book “Figures do not lie”

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Kolibri and Azbuka-Attikus Publishers present Vaclav Smil’s book “The numbers don’t lie. 71 facts important for understanding everything in the world “ (translated by Yuri Goldberg).

Canadian scientist, ecologist and political scientist Vaclav Smil is famous for his work on the connection between energy and ecology, demography and real politics, as well as his virtuoso ability to handle large arrays of statistics. This book, which fascinated Bill Gates, summarizes the most interesting material that Smill writes for IEEE Spectrum, one of the world’s leading scientific and engineering publications, and is a relevant guide to understanding the true state of affairs on our planet. It covers a wide range of topics, such as people, nations and countries, energy and how we use it, technical innovation, and the machines and devices that define the face of modern civilization. Urgent and important, combining statistics and history written with a sense of humor, this book makes us question what we thought was true.

We suggest reading two chapters from the book.

Sunlight: still out of competition

The progress of civilization can be traced by the level of lighting – primarily by its power, cost and light output. The latter reflects the ability of the light source to elicit a significant response in the eye and is calculated as the total luminous flux (in lumens) divided by the rated power (in watts).

In photopic conditions (that is, in bright lighting that allows colors to be distinguished), the apparent light output reaches a peak of 683 lm / W, the maximum for a 555 nanometer (nm) wave in the green part of the spectrum, and this color at any level power seems the brightest.

For many millennia, our artificial light sources have lagged behind this theoretical maximum by three orders of magnitude. Candles have a light output of only 0.2 to 0.3 lm / W, lanterns with light gas (illuminated European cities in the XIX century) – 5-6 times more, and the efficiency of the carbon filaments of the first Edison bulbs remained at about the same level . Light output increased sharply with the appearance of metallic filaments of osmium (1898; 5.5 lm / W) and tantalum (1901; 7 lm / W); After another ten years, tungsten filament in a flask filled with a mixture of nitrogen and argon increased the light output of conventional household lamps to 12 lm / W, and twisted tungsten filament, which appeared in 1934, increased it to 15 lm / W for 100-watt lamps. , which became the standard source of bright light in the first two decades after World War II.

Source: © V. Smill “Figures do not lie. 71 facts that are important for understanding everything in the world. ” Image courtesy of Azbuka-Atticus Publishing Group

Light sources with a different principle of operation – low pressure lamps, sodium and mercury (fluorescent) – appeared in the 1930s, but became widespread only in the 1950s. The best modern fluorescent lamps with electronic ballast have a light output of 100 lm / W; high pressure sodium lamps – up to 150 lm / W; low pressure sodium lamps – up to 200 lm / W. However, sodium lamps emit only monochromatic yellow light with a wavelength of 589 nm, and therefore they are not used indoors: they are only suitable for street lighting.

Today, all our hopes are connected with LEDs.

LEDs were invented in 1962 and at that time emitted only red light, ten years later green appeared, and in the 1990s. – blue LEDs of the increased brightness.

By covering such blue LEDs with fluorescent phosphors, the engineers were able to convert some of the blue light into warmer tones and thus obtain white light suitable for interior lighting. The theoretical limit for a bright white LED is about 300 lm / W, but modern household lamps are still very far from it. Philips sells in the United States – the standard mains voltage here is 120 volts (V) – 18-watt soft white light bulbs and adjustable power bulbs (replacement of 100-watt incandescent bulbs) with a light output of 89 lm / W. In Europe, where the mains voltage ranges from 220 to 240 V, Philips offers LED lamps with a light output of 172 lm / W (replacement of European 1.5-meter fluorescent tubes).

High efficiency LEDs have already led to significant energy savings worldwide; in addition, such lamps can work for three hours a day for twenty years, and if you forget to turn off the lights in the house, it will be almost not reflected in the electricity bill. However, like all other sources of artificial light, they do not provide a spectrum of radiation comparable to natural. Incandescent lamps give too little blue light, and fluorescent lamps emit almost no red light; LEDs have insufficient intensity in the red part of the spectrum and excessive intensity in the blue part. Their light is not very pleasing to the eye.

Since the 1880s. the light output of artificial light sources has increased by two orders of magnitude, but we still do not know how to reproduce sunlight indoors.

Batteries of increasing capacity: why?

It would be much easier to expand the use of solar and wind energy if we had better ways to store large amounts of electricity to compensate for interruptions in its flow.

Even in sunny Los Angeles, a standard home with rooftop photovoltaic panels that meet its needs will still face a serious daily shortage of up to 80% in January and a daily surplus of 65% in May. Such a house can be disconnected from the mains only if you install a bulky and expensive set of lithium-ion batteries. Even a small national power grid – 10 to 30 GW – can rely on intermittent sources only if there is a few gigawatts of electricity storage that can provide several hours of continuous operation.

Since 2007, more than half of the world’s population has lived in cities. By 2050, the number of citizens will exceed 6.3 billion and will be two-thirds of the total population, with a significant increase in the number of giant cities with a population of more than 10 million people (see the chapter “Prosperity of giant cities”). For the most part, these people will live in high-rise buildings, and therefore the opportunities for local electricity generation will be limited, but they will need an uninterrupted supply of electricity for homes, services, businesses and transport.

Imagine an Asian giant city in which a typhoon rages for a couple of days. Even if the main power lines can meet more than half of the city’s needs, it will take many more gigawatt-hours from storage until intermittent sources are restored (or fossil fuels may need to be connected, the same ones from which fossil fuels are needed). we seek to get rid of).

Lithium-ion batteries are used to store energy in both stationary and mobile versions. Lithium alloy is used as an anode, and graphite as a cathode (in ordinary lead-acid car batteries, the active substances of the electrodes are lead dioxide and lead). But, despite the much higher energy consumption, lithium-ion batteries are still not suitable for long-term storage of large energy reserves. The largest storage system, consisting of 18,000 lithium-ion batteries, is being built in Long Beach by AES Corp. for Southern California Edison. After commissioning in 2021, the repository should maintain a capacity of 100 MW for four hours. But 400 MWh of electricity is still two orders of magnitude less than a large Asian city would need if it lost sources of intermittent generation.

Source: © V. Smill “Figures do not lie. 71 facts that are important for understanding everything in the world. ” Image courtesy of Azbuka-Atticus Publishing Group

So, we need to multiply the storage volume: But how? The energy efficiency of sodium-sulfur batteries is higher than that of lithium-ion batteries, but hot liquid metal is very inconvenient as an electrolyte. Flow batteries, which store energy directly in the electrolyte, are still being implemented. Supercapacitors are not able to supply energy for a long time. And compressed air and flywheels – the eternal favorites of popular journalism – have been implemented in only a dozen small or medium-sized projects. It is likely that in the long run our hopes will be linked to cheap electricity from solar energy: with it we will decompose water by electrolysis and use the resulting hydrogen as a universal fuel – but the prospects for such hydrogen energy are still dim.

Thus, for large-scale energy storage, we still have to rely on technology that emerged in the 1890s: a pump-fed reservoir. You build one tank on a hill and use pipes to connect it to another below, and then use cheaper electricity by pumping water up at night to rotate the turbines during peak periods. Hydroaccumulation accounts for 99% of the world’s electricity storage, but at the same time we have to put up with the inevitable losses of about 25%. Many such storage facilities provide 1 GW of power – up to 3 GW – for a short time, but a metropolis that is completely dependent on solar and wind generation will require several such facilities. However, most giant cities are located away from the steep slopes or deep mountain valleys that are needed for hydro-accumulation. Many – including Shanghai, Calcutta and Karachi – are located on the coastal plains. Hydroaccumulation for them is possible only if the transmission of electricity over long distances.

The need for more compact, flexible, large-scale and cheaper electricity storage is self-evident. But the miracle is not in a hurry to us.

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