Why I say “water and clean energy, are two sides of the same coin?” At the outset, it may sound odd, but in reality, these two are closely interconnected. Let us examine, step by step, how they are connected, to each other, and what are the implications, in terms of cost, and environmental issues.
Take for example, power generation industries. The two basic materials, any power plant require, are, fuel and water. It does not matter, what kind of fuel is used, whether it is a coal based power plant or liquid fuel based plant like Naphtha, or gas based plants, like piped natural gas or LNG Of course, this statement is applicable only, for existing, conventional power generation technologies, and not for PV solar or wind energy, technologies. Let us consider, only power generation, involving conversion of thermal energy, into electrical energy. Today, more than 80% of power generation in the world, is based on thermal power, including nuclear plants. What is the usage of water in power plants? All thermal power plants use steam, as the prime motive force, to drive the turbines, (gas turbine is an exception, but, even in gas based plants, the secondary motive force, is steam, using waste heat recovery boilers, in combined cycle operations). The quality of water for conversion into steam is of high quality, purer, than our drinking water. The second usage of water is for cooling purpose. The water consumption by power plants, using once through cooling system is 1 lit/kwhr, and by closed circuit cooling tower, it is 1.7lit/kwhr .Only about 40% power plants in Europe, for example, use closed circuit cooling towers, and the rest use only ‘once through’ cooling systems. The total power generated in 2010, by two largest users, namely US and China, were 3792Twhrs and 3715 Twhrs respectively. The total world power production, in 2008 was 20,262 Twhrs, using following methods.
Fossil fuel: Coal 41 %, Oil 5.50%, Gas 21%, Nuclear 13% and Hydro 16%.
Renewable: PV solar 0.06%, PV thermal 0.004%, Wind 1.1%, Tide 0.003 %, Geothermal 0.3%, Biomass &others 1.30%.
(1Twhrs is = 1,000,000,000 kwhrs)
The above statistics, gives us an idea, on how much water, is being used, by power generating plants, in the world. Availability of fresh water, on planet earth, is only 2.5% (96. 5% oceans, 1.70% ground water, 1.7% glaciers and ice caps, and 0.001% in the air, as vapor and clouds).The world’s precious water source, is used for power generation, while millions of people, do have water, to drink. The cost of bottled drinking water is US$ 0.20 /lit, in countries like, India. This situation is simply unsustainable.
The prime cause, for this situation, is lack of technology, to produce clean power, without using water. The power technology, we use today, is based on the principle of electromagnetism, invented, by Michael Faraday, in the year 1839. That is why, renewable energy, is becoming critically important, at this juncture, when the world is, at the cross road.
In order to overcome, the shortage of fresh water, many countries are now opting, for seawater desalination. Desalination, again, is an energy intensive process. For example 3-4 kwhrs of power is used, to desalinate 1 m3 of water. This power has to come, from fossil fuel fired, thermal power plants, which are often co-located, with desalination plants, so that, all the discharge, from both the plants, can be easily pumped into the sea. Since, the world is running out of fresh water, we have to look for attentive source of water. In countries like India, the ground water is being exploited, for agricultural purpose, and the ground water is getting depleted. Depleting water resources is a threat to agriculture production. It is a vicious circle.
That is why, distributed energy systems, using Hydrogen as an alternative fuel, is an important step, towards sustainability. One can generate Hydrogen from water, using renewable energy source, like solar or wind, and store them, for future usage. The stored Hydrogen can be used to generate power, as and when required, at any remote location (even where there is no grid power).The water is regenerated, during this process of power generation using Fuelcell, which can be recycled. There is no large consumption of water, and there is no greenhouse emission. It is a clean and sustainable solution. The same stored Hydrogen can also be used as a fuel for your car! Therefore; (The above statics are based on Wikipedia data).