Using Solar Energy to Produce Solar Steam

Posted by Chuck Harrell on Jun 4, 2016 11:00:00 AM

sunWe're all used to seeing solar energy being used to power homes and some shops and provide energy to "the grid" but it's rarely used to power machinery.

Now, things are changing in that sun-rich countries like Oman, they are going to use solar energy to produce steam which will in turn, be used to power the drills which access hard to reach oil reserves.

Glasspoint, the company responsible for implementing this project, will use photovoltaic cells to "concentrate sunlight to generate 6,000 tons of solar steam per day....to feed directly to PDO's existing thermal EOR operations.

Solar steam is the process of using solar energy to heat water and turn turbines to generate electricity.  The difficulty is getting enough power from the sun to consistently keep boiling the water.  There are several conventional methods of increasing the power of the sun, from using heliostats (movable mirrors) to track the sun's position and concentrate the energy by up to 1,000 times to "parabolic troughs' which concentrate it by 60 to 80 times.  Another less common method of increasing the efficiency is to add something into the water to help it boil.  Traditionally, this 'something' is gold nanoparticles but since this also requires a heliostat and only increases efficiency by another 24%, it's not very popular.  But, according to this article from the Economist researchers at MIT, they built a "set-up that consists of a double-layers black disc floating on the surface of the water in an insulated breaker.  The disc's top layer consists of graphite flakes that were treated by placing them in a domestic microwave oven and heating them up, 'just like making popcorn', says Gang Chen, head of the MIT research team.  The resulting exfoliated graphite forms a 5mm thick porous matrix that absorbs and concentrates the heat from the sun.  The lower layer is a 10mm think porous carbon form that floats on the water and prevents the heat in the top layer from being lost to the water below.  The heat in the top layer creates a pressure gradient that slowly and continuously draws water up through the disc were the popcorned graphite easily turns the thin layer into steam."

This method is particularly useful since it only requires a magnification of ten and maybe even three and is 85% more efficient.

The Glasspoint project however uses troughs to concentrate the sunlight onto a pipe filled with water and they are confident that this project will save 5.6 trillion Btus of natural gas per year and will reduce CO2 emissions by more than 300,000 tons per year or the equivalent of taking 63,000 cars off the road.

In a country with guaranteed sunshine, an idea like this is an easy choice to make but in cloudier cooler climates where sunshine is less reliable, the folks at MIT maybe onto something that could help us all benefit from solar steam.

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