Monday, March 23, 2009

Like Astronauts Do

Last friday, March 20, the International Space Station showed off it's full power capability with the successful deployment of the final pair of solar wings, which were delivered and installed in the day's prior by the American Discovery Team. [1]
Watch the space station unfurl solar wings.

The starboard 6 or S6 solar array installed has a wingspan of 240 feet, with 32,800 solar cells. Click here for more information about the S6 solar system. More interesting to me though is that the team also replaced a tank for a failed unit in a system that converts urine to drinkable water. [2]

I didn't realize the ISS had a water recovery system (WRS), and I was curious about the technology behind it. After a little digging I found most of what I was looking for.

It didn't take long for me to realize that the reclaimed water unit is just one small piece to a huge power puzzle aboard the ISS called the Environmental Control and Life Support System (ECLSS). "The ECLSS consists of an air revitalization system, water coolant loop systems, atmosphere revitalization pressure control system, active thermal control system, supply water and waste water system, waste collection system and airlock support system. [3] The point is that all of these systems interact in a closed loop, receiving power from the solar arrays, to support the ISS atronauts' lives.

Grid assembly began in July of 2006 when the oxygen generator was delivered by the space shuttle Discovery. Then, on November 14, 2008, the US space shuttle Endeavour delivered the WRS which was fully operational by November 25.

The WRS (left image) recycles urine and waste water to clean water that can be used to drink, bath, prepare food, or generate oxygen by electrolysis. First, the Urine Processor Assembly (UPA) reclaims water from urine through distillation. This water is then added to the pther waste water and sent through the Water Processor Assembly (WPA). The WPA first uses a series of filters to remove free gases and solids. Then, any micro-organisms and other contaminates are removed by fast, high temperature chemical reactions. The end result is 6.8 tonnes of recycled waste water per year, which means the three person ISS crew can be increased to six, and more scientific equipment can be stored onboard. [4]

Such a renewable system is fantastic and I am sure the technology imployed in space is benifiting our energy technology efforts here on earth. Infact, Water Security Corporation, the patent owner of the WRS technology, has commercialized The Discovery – Model WSC4 for rural water dissenfection, which won a humanitarian award. [5]

But what I could not find is how much energy input is needed for the entire ECLSS, or even just the WRS. Because unlike the space station, whose energy storage from solar power is on site, we are having difficulties with storing and transpoting solar energy on Earth. So, my question is if large scale production of water recovery systems for homes and businesses of developed countries, where clean water is easily accessed, is practical in terms of the energy input?


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