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U.N. Predicts New Global Population Boom

Projections for climate change and many other big-picture trends assume that the world’s population will peak at nine billion people.

A new analysis suggests that the world’s population will keep rising through 2100, and not flatten around 2050 as has been widely assumed. Such an increase would have huge implications, but the prediction’s reliability is debatable, given that it does not take into account future hardships a large population would likely face.

According to the new analysis by researchers at the United Nations and several academic institutions, there is an 80 percent chance that the world’s population, now 7.2 billion, won’t stop at nine billion in 2050, but will instead be between 9.6 billion and 12.3 billion by 2100. The researchers increased their estimates after noting persistent high birth rates and faster-than-expected progress in combatting HIV/AIDS in Africa, according to the study, which is published today in the journal Science.

There are significant caveats. Climate change is projected to put major stresses on agriculture and water supplies, and these stresses were not considered as potential checks on population growth. Nor does the study take into account that population growth could trigger deadly calamities like food shortages, war, and disease even without climate change, says John Bongaarts, vice president and distinguished scholar at the Population Council, a think tank and research organization based in New York City.

Past studies assumed that the pattern of declining birth rates observed in Asia and Latin America in recent decades would be repeated in Africa. This assumption is built into previous projections, notably ones of Wolfgang Lutz, director of the Vienna Institute of Demography.

But that’s not what’s actually happening. For example, in Nigeria—Africa’s most populous nation, with 160 million residents—women are still having an average of six children each, as they’ve been doing for about the past 15 years. Such trends contribute to new estimates predicting a 90 percent probability that in 2100, Nigeria’s population will exceed 532 million. Africa’s overall population is now expected to go from one billion to four billion, says Adrian Raftery, a professor of statistics and sociology at the University of Washington who coauthored the report.

Raftery also points out that United Nations estimates have a history of accuracy. Projections made in the 1950s held that the population in 2000 would be 6.2 billion, and would be around seven billion now, both of which are close to what actually happened.

In response to the study, Lutz says, his newest analysis still suggests a less-dire outcome. “Our most likely scenario comes out somewhat lower than the current United Nations projections,” and suggests population will peak at 9.4 billion around 2070 and start a slow decline to nine billion by the end of the century, he said in a statement. “The end of world population growth is still to be expected this century.”

The differences in the two projections, he said, is due to differing methods and assumptions made about future birth and death rates for individual countries.

The United Nations paper offers prescriptions for keeping the population in check: more education for women and more widely available contraceptives.

Source? MIT

Germany and Canada Are Building Water Splitters to Store Energy

Renewables will never account for more than a fraction of the world’s energy resources until their intermittency can be addressed.

Gas power: A Hydrogenics electrolysis system in Falkenhagen, Germany, can absorb two megawatts of excess renewable energy and store it in the form of hydrogen.

Germany, which has come to rely heavily on wind and solar power in recent years, is launching more than 20 demonstration projects that involve storing energy by splitting water into hydrogen gas and oxygen. The projects could help establish whether electrolysis, as the technology is known, could address one of the biggest looming challenges for renewable energy—its intermittency.

The electrolyzer projects under construction in Germany typically consist of a few buildings, each the size of a shipping container, that consume excess renewable energy on sunny and windy days by turning it into an electric current that powers the water-splitting reaction. The resulting hydrogen can then be pumped into the storage and distribution infrastructure already used for natural gas and eventually turned back into electricity via combustion or fuel cells. It can also be used for a variety of other purposes, such as powering natural-gas vehicles, heating homes, and making fertilizer.

Germany isn’t the only country investing in hydrogen energy storage. Canada is getting in on the action, too, with a major demonstration facility planned for Ontario.

Electrolysis has advantages over some other energy storage options. It can be deployed almost anywhere, it can store vast amounts of energy, and the hydrogen can be used to replace fossil fuels not only in electricity production but also in industry and transportation, which account for far more carbon emissions.

Even so, it has long been considered a relatively lousy way to store energy because of its low efficiency—about 65 percent of the energy in the original electricity is lost. But improvements to the technology are reducing costs, and the large-scale use of renewable energy is creating new needs for storage, making electrolysis a practical option in a growing number of places.

Power down: This new mini-fridge-size electrolyzer from Hydrogenics can produce as much hydrogen as 12 conventional ones.

Earlier this year, Siemens broke ground in Mainz, Germany, on what it says will be the world’s largest proton exchange membrane (PEM) electrolyzer. Whereas other electrolyzers are designed to operate with steady power levels, the PEM system performs well even with quickly changing amounts of power from wind and solar. When it opens next year, it will have the capacity to produce 650,000 kilograms of hydrogen a year, the energy equivalent of 650,000 gallons of gasoline. (As a demonstration plant, however, it probably won’t run continuously.)

Hydrogenics, which has supplied electrolyzers for many of the biggest projects in Germany, is designing a 40-megawatt system that will produce the equivalent of 4.3 million gallons of gasoline a year. The company recently developed a PEM electrolyzer that’s less than a tenth the size of its conventional alkaline ones. The small size, in addition to making it easy to site the electrolyzers, can help lower costs.

Costs are also decreasing because excess wind and solar power creates a glut of power on the grid. Because power needs to be used as soon as it’s generated to keep the grid stable, prices are sometimes dropped to zero so buyers can be found. Cheap electricity makes electrolysis far more competitive.

Electrolysis remains more expensive than producing hydrogen from natural gas—at least in the United States, where natural gas is cheap. But it can compete with storage options such as batteries, says Kevin Harrison, a senior engineer at the National Renewable Energy Laboratory in Golden, Colorado. It’s also more versatile than the cheapest way to store energy: pumping water up a hill and then letting it back down to drive a turbine. That approach is severely limited by geography—but, he says, “you can put an electrolyzer almost anywhere.”

Source: MIT 

Adaptive Material Could Cut the Cost of Solar in Half

A material with optical properties that change to help it capture more incoming sunlight could cut the cost of solar power in half, according to Glint Photonics, a startup recently funded by the Advanced Research Projects Agency for Energy (ARPA-E).

Glint’s adaptive material greatly reduces the cost of a tracking system used in some types of solar power. It changes its reflectivity in response to heat from concentrated sunlight in a way that makes it possible capture light coming in at different angles throughout the day.

It’s well known that focusing sunlight makes it possible to use smaller, cheaper solar cells. But this is usually done with lenses or mirrors, which must be moved precisely as the sun advances across the sky to ensure that concentrated sunlight remains focused on the cells. The equipment required for that and the large amount of steel and concrete needed to keep the apparatus steady makes the approach expensive.

Glint’s light concentrator has two parts. The first is an array of thin, inexpensive lenses that concentrate sunlight. The second is a sheet of glass that serves to concentrate that light more—up to 500 times—as light gathered over its surface is concentrated at its edges.

small lenses focus sunlight onto an adaptive material that helps track the movement of the sun

Sun tracker: Small lenses focus sunlight onto an adaptive material that helps track the movement of the sun.

The sheet of glass is covered with reflective materials on the front and the back that trap light inside the glass. One of these sides features the new adaptive substance made by Glint. When a beam of concentrated light from the array of lenses hits the material, it heats up part of it, causing that part to stop being reflective, which in turn allows light to enter the glass sheet. The material remains reflective everywhere else, helping to trap that light inside the glass—and the light bounces around until it reaches the thin edge of the glass, where a small solar cell is mounted to generate electricity.

As the day goes on, the beam of light from the lenses moves and the material adapts, always allowing light in only where the beam of light falls, and reducing the need to keep the apparatus pointed directly at the sun.  

Glint’s CEO Peter Kozodoy says solar power from its devices could cost four cents per kilowatt-hour, compared to eight cents per kilowatt-hour for the best conventional solar panels. This month, the company received the first installments of a $2.2 million grant from ARPA-E. The ARPA-E funding will allow the company to scale up from prototypes just 2.5 centimeters across to make 30-centimeter modules, nearly large enough for commercial operation.

Howard Branz, a program director at ARPA-E, says the main remaining challenge is increasing the amount of sunlight that makes it to the solar cells, something that needs to be improved over the proof-of-concept device, in which some of the light is absorbed or reflected en route to the solar cells.