Tag Archives: Water

Salinity gradient power rising as a realistic renewable energy source

Estuaries are the locations where river water mixes with seawater. They are found along coastlines throughout the world, but what most people don’t realize is the significant potential to produce clean energy from these mixing water streams. The salinity gradient between the two streams of water contains a large amount of osmotic power, which can be thought of as the available energy (or chemical potential) from the differences in salt concentration between the fresh water and seawater. The enormous amounts of energy released where freshwater and seawater meet “can be utilized for the generation of power through osmosis”, which is “defined as the transport of water through a semi-permeable membrane.” [1]

The idea of obtaining energy from osmosis, or salinity gradient power, has been studied for decades, but in early 2009 two teams were racing to be the first to build a working prototype power plant making salinity gradient power a feasible method for renewable energy generation. Both teams have been working on the development and implementation of a membrane based osmotic process, but their approaches for generating the electricity are very different [2]. Westus (The Centre for Sustainable Water Technology), located in the Netherlands, is focusing on the Reverse Electrodialysis (RED) method to produce electricity. They claim that they will utilize fresh water from the Rhine river and saltwater from the North Sea to construct a type of battery by employing two membranes permeable to ions, but not to water. Utilizing the saltwater, one membrane will allow the passage of positively charged sodium ions into a stream of fresh water and the other membrane will allow the passage of negatively charged chloride ions into another channel of freshwater. The separated charged particles with electrodes placed in both streams makes up the chemical battery, which directly produces electricity. [2] Statkraft, a leading renewable energy group located in Norway, is focusing on Pressure Retarded Osmosis (PRO) as their method to extract electricity from salinity gradients. This method utilizes a membrane, permeable to water, to draw fresh water into the concentrated salt water, thus increasing the pressure in the salt water chamber. The resulting pressure can then be used to drive a turbine to produce electricity. In November of 2009, Statkraft opened the world’s first prototype osmotic power plant in Tofte Norway. [3] This facility had a limited production capacity (of around 4 kW) and is mainly used for testing and validation of data, hopefully leading to the construction of a large commercial power plant by 2015.

While the idea of harvesting free energy from estuaries and salinity gradients may seem like a flawless idea, it comes with both pros and cons. On one side, the technology is considered “as green as it gets”, with the only waste product being brackish water, which flows into the sea mixing with the sea water [2].  It is a constantly flowing source of renewable energy, unlike the intermittent energy provided by sources such as solar or wind power. It can also easily be combined with existing power plants and industries and can be built underground, thus reducing costs and visual pollution [2]. On the other side, the membrane technology still has a long way to go. The membranes are prone to bio-fouling from algae and silt, which reduce the membrane’s lifetime and efficiency. Salinity gradient power is mainly suitable only for places where there is an abundant supply of freshwater meeting saltwater, which clearly favors countries with a large coastline [2]. Also, the environmental impact and environmental policy should be considered for future plants of this type. First off, there are many species of aquatic life that are adapted to survive in waters with a specific range of salinity concentrations, and these power plants could affect the salinity of an area of water. It has been found that large salinity changes in aquatic environments can result in low densities of plants and animals [4]. Then one must consider the environmental policy and impact of structures that intake such large volumes of river water and sea water. These power plants must conform to strict construction permits and environmental regulations.

While many issues dealing with the viability of salinity gradient power as a renewable energy source are still being addressed, advancements in the technology are constantly being made. In June of 2012, Statkraft’s head of osmotic power said “We see that the development of technology is accelerating and that an industry is emerging. The membranes we are testing at Tofte this summer are ten times more efficient than the ones we installed during the opening of the prototype in the autumn of 2009” [5]. Earlier this year, researchers discovered a new more efficient way to harness osmotic power utilizing Boron nitride nano tubes [6]. They claim that a 1 meter-squared membrane using this technology could have the same 4 kW capacity as the whole Statkraft prototype power plant. This experimental device, which is three orders of magnitude more efficient than the current system, could significantly enhance the commercial viability of salinity gradient power as a realistic source of energy [6]. While the ultimate future of salinity gradient power is unknown, it has the potential to be one of the prominent renewable energy sources on the planet.

[1] http://www.statkraft.com/energy-sources/osmotic-power/

[2] http://www.gizmag.com/salinity-power-renewable-energy-osmosis/11206/

[3] http://www.gizmag.com/statkraft-osmotic-power/13451/

[4] Montague, C., Ley, J. A Possible Effect of Salinity Fluctuation on Abundance of Benthic Vegetation and Associated Fauna in Northeastern Florida Bay. Estuaries and Coasts. 1993. Springer New York. Vol. 15 No. 4. Pg. 703-717

[5] http://www.statkraft.com/presscentre/news/statkraft-considering-osmotic-power-pilot-facility-at%20sunndalsora.aspx

[6] http://www.gizmag.com/osmotic-salinity-gradient-power-nanotubes/26623/

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Straws of Life: A Global Solution

We take for granted the fact that we live in a country that provides easily attainable clean drinking water. Water fountains provide tap water that has been purified of disease-causing bacteria and are widely available and accessible to the public. Clean drinking water has evolved into an expectation for us; it is now considered a basic human right to have access to improved sources of drinking water.

Sadly, this is not the case for underdeveloped countries.

Worldwide, 783 million people drink water that is unclean and unsafe [2].

RTEmagicC_739px-Mwamongu_water_sourceThese unsanitary conditions, usually typical for third world countries, can be deadly. It is estimated that up to 4,000 children die every day from diarrheal disease and other illnesses caused by unclean drinking water [1][2]. Most of these countries don’t have the infrastructure to provide clean water, or any other form of residential energy, for the public. Africa is in real trouble: “Of the 25 nations in the world with the greatest percentage of people lacking access to safe drinking water, 19 are in Africa” [3].

The main cause for lack of clean water is simple lack of power. Impoverished countries don’t have the energy (or money) to construct and operate water treatment facilities. Having said that, necessity is the mother of invention; in 2005, the swiss-based company Vestergaard Frandsen found a solution: It’s called LifeStraw. [4]


The LifeStraw is a handheld straw-like device that allows the user to filter water as they drink it.lifestraw-a-diagram

When a user sucks on the top of the straw, water is pulled through hollow fibers with pores 0.2 microns in length. These small pores trap any bacteria, parasites, or impurities in the water as it flows up to the user’s mouth [6]. It’s a relatively simple strategy, and is fairly effective. It removes 99.9% of bacteria and parasites from the water. One of these straws can last for 1,000 liters; this is equivalent to sustain one grown human with drinking water for a year [5].

While this device seems like a life saver, it has some limitations. Firstly, it is unable to filter out chemicals and water-borne viruses. However, the main issue is with the cost of the item. While only $6.50 per personal LifeStraw, citizens of impoverished nations still can’t afford them [1].

Again, Vestergaard came up with a solution to that problem: they donated LifeStraws to over 4.5 million Kenyans.  LifeStraws help users to bypass burning wood to boil water, which helps Vestergaard earn carbon credits. The company can then sell these credits to other companies who need to offset their carbon emissions [1]. In this way, Vestergaard can save lives while the pollutant companies pay for it.

Some people are upset with Vestergaard’s philanthropic move on the basis that the public image covers up the profit that they are actually making [1]. But I’m pretty sure the Kenyans aren’t complaining, and no one can argue against the value of lives saved.



[1] Barksdale, Martha, and Kate Kershner. “How LifeStraw Works.” HowStuffWorks. N.p., n.d. Web. 02 Apr. 2013.

[2] “Clean Water Campaign.” Clean Drinking Water. N.p., n.d. Web. 02 Apr. 2013.

[3] David, Michael,, David,, and Caroline. “Africa.” ThinkQuest. Oracle Foundation, n.d. Web. 02 Apr. 2013.

[4] “LifeStraw FAQ.” Waterforlifestraw.co.uk. N.p., n.d. Web. 02 Apr. 2013.

[5] “LifeStraw Frequently Asked Questions.” LifeStraw Frequently Asked Questions. N.p., n.d. Web. 02 Apr. 2013.

[6] “LifeStraw.” Wikipedia. Wikimedia Foundation, 04 Feb. 2013. Web. 02 Apr. 2013.

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Insurance, Water, Electricity, and Climate Change

As discussed in class, the validity of climate change is inevitable; the cumulative evidence that exists in support of climate change will eventually lead to a unanimous consensus [1]. However, it is important to know how climate change might be affecting us today.

In a recent article on the website Co.Exist (which I encourage all of you to regularly visit), Terry Tamminen adopts an interesting approach to assessing how climate change will play a significant role this year in four markets: insurance, water, real estate, and electricity. I offer my opinions on each of his analyses. Tamminen writes that the Insurance Information Institute recorded national insured losses of close to $36 billion in 2011 “from record-setting extreme weather catastrophies” [2].  While this is a significantly high number, the chart from the III puts things into perspective [3]. There definitely seems to be a higher frequency of losses post-1988 compared to pre-1988. In fact, it seems like the three years with the highest insured losses on record were all after 1994. Tamminen is perhaps right on the trend of increasing insurance costs.


Another kind of disaster discussed in the article is drought. In our class last Thursday, Mark Strama alluded to a general consensus in Texas that water is one of the state’s biggest concerns [5]. Spicewood Beach, a town not too far from Austin in Burnet County, has become the first town in Texas to officially run out of water [4]. The town is currently transporting in their water from miles away and costs the agency roughly $1000 a day. In 2011, Texas experienced its driest year since 1917, and if it continues this way, it’s not unimaginable to see these costs being passed down to consumers in the foreseeable future.

Tamminen discusses how the cost of coastal real estate will also rise as a consequence of preparing for more intense storms. But the last – and perhaps the most interesting – argument he makes is that the cost of electricity bills will go down. In California, specifically, the Energy Commission has been releasing some fairly detailed guidelines on the energy consumption of household goods. The 2010 edition, for example, has a stipulation that “a television shall automatically enter … stand-by mode after a maximum of 15 minutes without video and/or audio output” [6]. Tamminen believes that regulations like these, along with higher standards on chargers, will save $306 million a year off Californian energy bills, because they will have to build capacity for a lower peak load. I couldn’t find the source of this information, but a quick look at the USA’s energy consumption seems to imply that our energy consumption has reduced its rate of growth, while we consumed less in the years 2008-2010 compared to 2007 [7]:

While history has definitely shown that we can consume less, it’s hard to say definitively whether per unit energy costs will go down as a result of these measures. We trade energy on a global market, and the rising energy consumption of countries like China, India, and Brazil will probably have a bigger impact on the cost of energy compared to progressive local standards.

Do you agree/disagree with Tamminen’s views? Do you think he missed other important indicators?

[1] Dr. Webber’s Lecture on Energy, Technology, & Policy. The University of Texas at Austin, April 3, 2012

[2] 3 Things That Will Cost More in 2012, Terry Tamminen. http://www.fastcoexist.com/1679610/3-things-that-will-cost-more-in-2012

[3] http://www.iii.org/facts_statistics/catastrophes-us.html

[4] http://www.nytimes.com/2012/02/04/us/texas-drought-forces-town-to-haul-in-water-by-truck.html?_r=1

[5] Mark Strama’s Lecture on Energy, Technology, & Policy. The University of Texas at Austin, April 5, 2012

[6] http://www.energy.ca.gov/2010publications/CEC-400-2010-012/CEC-400-2010-012.PDF

[7] Data from EIA Annual Energy Review.


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CDP Water/Carbon Nexus Accounting

The Carbon Disclosure Project (CDP) is the world’s largest corporate and business carbon tracking mechanism with some 2,500 companies beginning to disclose their carbon footprints. This project “represents 475 investors with $55 trillion under management.” (Bhatia, Bloomberg 2009)
Of course the water content of everything we use is far more significant than most people imagine, and CDP recently announced that it will be canvassing 300 companies water use as well (available 4th Quarter of 2010). Major companies are signatories of CDP including Goldman Sachs, chemicals giant BASF, Walmart, Chevron and many more. It is not known which companies will be canvassed for water, but this is a major step in the right direction of trying to account for the world’s most important input, water, and the world’s most important output, greenhouse gases (known more commonly as C02 equivalents which includes gases like methane which are much more potent than C02 in its radiative forcing effects and therefore often measured in C02 “equivalents”, or simply “carbon”, for ease).
A similar project was recently conducted by the Pacific Institute and Ceres trying to address the risk of water (availability) which is becoming more and more pronounced (Morrison, Ceres 2009) One of the frustrations of businesses and communities is the lack of water input tracking throughout the value-chain process of products and processes. The Pacific Institute documented 8 sectors/industries including apparel, high-tech/electronics, beverage, food, biotech/pharma, forest products, metals/mining, and electric power/energy. It then broke out each industry into 4 steps of the value-chain including raw material production, suppliers, direct operations, and product use/end of life. Blue (surface and groundwater), green (rainwater stored in the soil as moisture) and grey (polluted) water intensities were calculated across this matrix to compare industry water intensity.
One common thread in the difficulty of tracking water and carbon is accounting for the transportation of billions of goods, materials and people traded and transported throughout the world. This kind of accounting is often overlooked because of the complexity, but it is fundamental that we understand the transportation usage of water and carbon of products and processes because it is so huge to begin with. The EPA put transportation as the #2 US greenhouse gas emitter at 28% of total emissions (the electric power industry was #1 at 34% of the total GHG emissions).

The Ceres / Pacific Institute report revealed how complex this tracking can get when you consider the value-chain of a good or process (it left out transport however). While the sheer numbers may seem daunting, imagine how many packages UPS, DHL, FedEx etc. deal with on a total world daily basis. They know exactly what’s going where, where it’s at in real time (usually) etc. Walmart for instance is renowned for its allocative efficiency of products throughout its stores and supply chains by knowing exactly where everything is, and how long it will take to restock stores in need.
At least retail should have little problem letting consumers, producers, entrepreneurs & legislatures compare the water and carbon footprints of 2 goods. Products bar codes’ could have an added tracer that identifies where the product was shipped from. Additional barcodes could be added by each transporter identifying the distance and means of transportation (or by another similar convention). This would inevitably favor local products, but that’s maybe part of the great sacrifice that fate asks of our generation, which has it pretty well so far compared to the previous generations. You may need to pay a small premium for the extra tons of CO2 and water you are actually consuming. This isn’t really a tax, it’s more of a weaning industry off the ecological welfare it’s been taking all these years. No more ecological subsidies- it’s time we pay for what we actually consume (including transport)! I hope CDP is accounting for transport somehow.

Bhatia, Meera. ” Carbon Disclosure Project to Canvass Water Use by Companies.” Bloomberg 19 November 2009 http://www.bloomberg.com/apps/news?pid=20601085&sid=aPkh05tK1SOE
Morrison, Morikawa, Murphy & Shulte. “Water Scarcity& Climate Change: Growing Risks for Businesses & Investors.” Ceres & The Pacific Institute February 2009 http://www.pacinst.org/reports/business_water_climate/full_report.pdf
INVENTORY OF U.S. GREENHOUSE GAS EMISSIONS AND SINKS: 1990 – 2007 APRIL 15, 2009 U.S. Environmental Protection Agency. http://epa.gov/climatechange/emissions/usinventoryreport.html p. 36

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