You can not create energy without water, whether it is directly driving hydroelectric turbines or being boiled to drive a steam turbine or more likely being used to cool the systems.
You can not get water without using energy, if you're lucky enough to live next to a pristine stream you're going to need to pump it out, otherwise you have to process it, or pump it great distances.
A great example of this in Australia, that has received a lot of attention is desalination (particularly if you are a Sydney sider). Desalination requires A LOT of energy and when I say a lot I mean a lot! Currently it takes around a top of the line efficient reverse osmosis filtering plant around 5 MWh of electricity to generate 1 ML of water, or around 1.25 Wh to get your glass of water filtered. And if you consider an old school thermal desalination plant it takes around 80MWh/ML or around 20 Wh per glass of water.
Now when you consider that the majority of energy in Australia is generated using coal fired power stations, cooled with cooling towers then we need to factor in the water cost of generating the electricity it takes roughly 1900 L of cooling water to generate a MWh of electricity.
Further to the water cost of the electricity we need to consider the waste water from the desalination plant. The most efficient RO plants have water usage efficiencies of around 48% (which means 52% of the water that enters a desalination plant leaves as waste water) and generally the efficiency is more likely to be down in the mid to high 30s. So if we take the most efficient plant around then for every ML of clean water that is produced there is 1.083 ML of dirty water produced.
So basically for your glass of water you'll be using 1.25 Wh and 273 mL if you're getting it via desalination. If you don't happen to live at the desalination plant then there'll be additional energy that is required to pump the water to your location and further if the desalination plant isn't co-located with the power plant then transmission losses of around 20% need to be factored into the equation as well.
SOURCE: IEEE Spectrum 6.10
A great example of this in Australia, that has received a lot of attention is desalination (particularly if you are a Sydney sider). Desalination requires A LOT of energy and when I say a lot I mean a lot! Currently it takes around a top of the line efficient reverse osmosis filtering plant around 5 MWh of electricity to generate 1 ML of water, or around 1.25 Wh to get your glass of water filtered. And if you consider an old school thermal desalination plant it takes around 80MWh/ML or around 20 Wh per glass of water.
Now when you consider that the majority of energy in Australia is generated using coal fired power stations, cooled with cooling towers then we need to factor in the water cost of generating the electricity it takes roughly 1900 L of cooling water to generate a MWh of electricity.
Further to the water cost of the electricity we need to consider the waste water from the desalination plant. The most efficient RO plants have water usage efficiencies of around 48% (which means 52% of the water that enters a desalination plant leaves as waste water) and generally the efficiency is more likely to be down in the mid to high 30s. So if we take the most efficient plant around then for every ML of clean water that is produced there is 1.083 ML of dirty water produced.
So basically for your glass of water you'll be using 1.25 Wh and 273 mL if you're getting it via desalination. If you don't happen to live at the desalination plant then there'll be additional energy that is required to pump the water to your location and further if the desalination plant isn't co-located with the power plant then transmission losses of around 20% need to be factored into the equation as well.
SOURCE: IEEE Spectrum 6.10
Water is used because it's cheap, plentiful, and has a convenient boiling point. You don't need it to be potable for most power plants, and you can recycle it. Fuel cells, solar, and wind power do not use water (although Fuel cells *produce* water). I'm sure there's others.
ReplyDeleteThe deep link between water and energy is in the energy cycle - Water is either heated by the earth's core or by the sun (the evaporation cycle really feeds hydro). This is the same as wind or coal.
Unfortunately, in order to cool a power plant the water needs to be fairly good quality and for instance if water is used to cool a plant it can generally not then be used to say irrigate a field without some significant post processing to remove minerals that contaminate the water. Also, the figures above are for the output of non-reusable water from a plant.
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