Global Emissions Culprits

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The Economist : Desalination Breakthrough

THERE is a lot of water on Earth, but more than 97% of it is salty and over half of the remainder is frozen at the poles or in glaciers.  Meanwhile, around a fifth of the world’s population suffers from a shortage of drinking water and that fraction is expected to grow.  One answer is desalination—but it is an expensive answer because it requires a lot of energy.  Now, though, a pair of Canadian engineers have come up with an ingenious way of using the heat of the sun to drive the process.  Such heat, in many places that have a shortage of fresh water, is one thing that is in abundant supply.  Ben Sparrow and Joshua Zoshi met at Simon Fraser University in Vancouver, while completing their MBAs.  Their company, Saltworks Technologies, has set up a test plant beside the sea in Vancouver and will open for business in November.  Existing desalination plants work in one of two ways.  Some distil seawater by heating it up to evaporate part of it.  They then condense the vapour—a process that requires electricity.  The other plants use reverse osmosis.  This employs high-pressure pumps to force the water from brine through a membrane that is impermeable to salt.  That, too, needs electricity. Even the best reverse-osmosis plants require 3.7 kilowatt hours (kWh) of energy to produce 1,000 litres of drinking water.

Mr Sparrow and Mr Zoshi, by contrast, reckon they can produce that much fresh water with less than 1 kWh of electricity, and no other paid-for source of power is needed.  Their process is fuelled by concentration gradients of salinity between different vessels of brine.  These different salinities are brought about by evaporation.  The process begins by spraying seawater into a shallow, black-bottomed pond, where it absorbs heat from the atmosphere.  The resulting evaporation increases the concentration of salt in the water from its natural level of 3.5% to as much as 20%.  Low-pressure pumps are then used to pipe this concentrated seawater, along with three other streams of untreated seawater, into the desalting unit.  As the diagram explains, what Mr Sparrow and Mr Zoshi create by doing this is a type of electrical circuit.  Instead of electrons carrying the current, though, it is carried by electrically charged atoms called ions.

Salt is made of two ions: positively charged sodium and negatively charged chloride.  These flow in opposite directions around the circuit.  Each of the four streams of water is connected to two neighbours by what are known as ion bridges.  These are pathways made of polystyrene that has been treated so it will allow the passage of only one sort of ion—either sodium or chloride.  Sodium and chloride ions pass out of the concentrated solution to the neighbouring weak ones by diffusion though these bridges (any chemical will diffuse from a high to a low concentration in this way).  The trick is that as they do so, they make the low-concentration streams of water electrically charged.  The one that is positive, because it has too much sodium, thus draws chloride ions from the stream that is to be purified.  Meanwhile, the negative, chloride-rich stream draws in sodium ions.  The result is that the fourth stream is stripped of its ions and emerges pure and fresh.  It is a simple idea that could be built equally well on a grand scale or as rooftop units the size of refrigerators.  Of course, a lot of clever engineering is involved to make it work, but the low pressure of the pumps needed (in contradistinction to those employed in reverse osmosis) means the brine can be transported through plastic pipes rather than steel ones.  Since brine is corrosive to steel, that is another advantage of Mr Sparrow’s and Mr Zoshi’s technology.  Moreover, the only electricity needed is the small amount required to pump the streams of water through the apparatus.  All the rest of the energy has come free, via the air, from the sun.

Reference : http://www.pheedcontent.com/click.phdo?i=c03d296d65b0c7a30e1f0d5e9e07374c

FT : Walking The Green Talk

Scary requirements -

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Reference : Financial Times, Sep 24th 2009

FT : US Is The Real Renewable Energy Dragon

The history of the US is replete with images of extravagant fossil-fuel consumption: smoke billowing from gleaming trains; long, sleek, gas-guzzling cars; gigantic refineries endlessly pumping out plumes of dirty air.  But the reputation is somewhat misleading.  For much of the country’s history, renewable energy played a far more central role than it does today.  The first US hydroelectric power plant opened on the Fox River near Appleton, in eastern Wisconsin, in 1882, supplying electricity to the town’s paper mill and to the home of its owner.  By the early 1900s, hydroelectric power supplied more than 40% of US electricity needs and by the 1940s, hydropower provided about 75% of all the electricity consumed in western and Pacific north-western states.  Fossil-fuel consumption, however, rapidly eclipsed hydro, and in recent years environmental criticisms of the damage dams can have on aquatic ecosystems led to the decommissioning of some plants.  Nowadays, hydroelectric generation supplies only a small fraction of the US’s electricity.  However, its history goes to show that the country was not always the great global polluter it is today.  And as the US moves to reduce its dependence on carbon fuels, alternative energy sources are back in vogue.  In fact, renewable energy already plays a relatively significant role in US electricity production.  Discounting hydroelectricity, the US is the world’s biggest consumer of renewable energy for electricity – consuming twice as much as Germany and three times as much as Japan.

Renewable energy, including hydro, accounted for more than 7% of the US’s total energy consumption in 2008, according to the US Department of Energy.  Although that is still dwarfed by energy from petroleum, natural gas and coal, alternative energy sources are slowly but surely taking a bigger share of the country’s energy use: in 2004, renewable energy’s share of total US energy consumption stood at 6%; and renewable energy consumption grew by 7% between 2007 and 2008, despite a 2% decline in total US energy consumption.  At 7% of the total, alternative energy sources are rivalling nuclear power’s 9% contribution to the US’s energy make-up.  Although hydroelectricity remains by far the largest source of renewable electricity in the US – providing about 248bn kilowatt hours last year – the real star of the renewable energy scene in recent years has been wind power.  The sector has grown strongly in recent years.  By the end of last year, wind provided 1.3% of US total electricity generation, up from 0.4% in 2004.  Last year the US overtook Germany as the world’s biggest producer of power from wind.  Before the economic downturn, the US wind energy industry had aimed to reach the goal of supplying 20% of the US’s electricity supply by 2030.  But since the crisis struck, much financing has evaporated.  In general, the renewable energy industry has found debt financing scarcer and pricier than for conventional power…..While wind-generated energy is relatively cheap, industrial solar generation is much more expensive than coal and natural gas.  Nevertheless, the industry is expected to grow.  A recent report by Pike Research, the clean technology research group, says the US could jump ahead of Germany, Spain and Japan to lead the global solar industry by 2014.  Solar producers from those countries have recently made big investments in the US.  That reflects the support of President Barack Obama, who set aside $39bn of the $787bn stimulus package for green projects.  “There is significant momentum behind the solar industry, but that growth is being driven by policy directives and government incentives, not by economics,” analysts at Credit Suisse noted this year, arguing that in the longer term, solar prices needed to drop by 50% if renewable energy were to claim its place on the US electricity grid.  This, they said, could happen by next year or the year after.

…..Apart from the short-term financing problems, wind and solar power face a structural hurdle in becoming a mainstream part of the US energy scene.  Ray Gogel, president and chief operating officer of Current Group, which sells “smart grid” technology to electricity utilities, points out that the growth in alternative energy has also introduced much more volatility into the US’s power grid.  This is because wind and solar power cannot be depended on at the times when energy demand is highest.  As a result, reserve margins have to be high – about 85% of renewable energy in the grid – and the standby energy needed for this is usually provided by coal or natural gas, which offsets some of the environmental benefits of using renewables in the first place.  Mr Gogel, a veteran of the alternative energy industry, says the real step forward for renewables will be to “weather proof” the electricity grid through better technology – something the Obama administration has indicated it wants to spur by designating $4bn for smart-grid technology.  That should start to enable more use of alternative energy sources with fewer volatility problems.  If it works, says Mr Gogel: “We won’t be talking about alternative energy – we’ll just be talking about sustainable energy.”

Reference : http://www.ft.com/cms/s/0/2dcf907a-a75c-11de-9467-00144feabdc0.html

FT : Global Wind Capacity

Interesting graphic -

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