Next Big Future (http://nextbigfuture.com/2009/02/water-and-energy.html )
February 10, 2009
For any energy source, the cooling water can be waste-water or salt-water if the siting of the power plant has those non-fresh water sources available. Coal and solar-thermal can have more siting issues. Coal needs to be nearer to coal resources because millions of tons/year of coal is needed per plant. Solar thermal needs to be in sunny areas.
The main concerns with water that is used for energy relate to the fresh water budget of an area and rate of fresh water withdrawals. So if fresh water is turned into steam that leaves an area and falls as rain elsewhere it is no longer part of the current water budget for a particular area.
Some water definitions
Watershed (Drainage Basin, Catchment Basin, River Basin)
(1) The total region or area above a given point on a stream or lake that contributes water to the flow at that point. It is designated by the dividing line of area from which surface streams flow in two different directions; the line separating two contiguous drainage areas. (2) United States usage. The total area above a given point on a stream that contributes water to the flow at that point. The entire region drained by a waterway or which drains into a lake or reservoir. (3) British usage. The topographic dividing line from which surface streams flow in two different directions; the line separating two contiguous drainage areas. (4) The area drained by a stream and its tributaries
Managing all the natural resources of a watershed to protect, maintain, or improve its desired water budget, both quantity and quality, over time.
A useful measure of performance from a water-efficiency standpoint is the net energy yield per unit of water withdrawn or consumed. Consumptive use of water is largely due to evaporation losses from cooling towers and evaporators during the distillation of ethanol following fermentation. Consumptive use of water is difficult to directly measure because it depends on relative humidity, wind speed, and temperature in addition to the process configuration. However, water permits are generally required from state authorities to withdraw well water or surface water for industrial use, and this water is more or less continually metered. For that reason, this report considers water withdrawals as the measure of water use. This includes both consumptive and non-consumptive use, but as biorefineries increasingly incorporate water recycling, the difference between consumptive and total water use is decreasing.
Water budget. A summation of inputs, outputs, and net changes to a particular water resource system over a fixed period. (Also, water balance model).
It is estimated that 69% of world-wide water use is for irrigation, with 15-35% of irrigation withdrawals being unsustainable.
It is estimated that 15% of world-wide water use is industrial. Major industrial users include power plants, which use water for cooling or as a power source (i.e. hydroelectric plants), ore and oil refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent.
It is estimated that 15% of world-wide water use is for household purposes. These include drinking water, bathing, cooking, sanitation, and gardening. Basic household water requirements have been estimated by Peter Gleick at around 50 liters per person per day, excluding water for gardens.
Recreational water use is usually a very small but growing percentage of total water use.
Explicit environmental water use is also a very small but growing percentage of total water use. Environmental water usage includes artificial wetlands, artificial lakes intended to create wildlife habitat, fish ladders around dams, and water releases from reservoirs timed to help fish spawn.
Sandia Presentation on Water and Energy
Sandia has a 14 page water and energy overview