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Tag Archives: Ocean thermal energy conversion

We have been using fossil fuels like diesel, petrol and natural gas for power generation and transportation from the time of industrial revolution. The basic fuel and the combustion technology are practically the same with efficiencies less than 40%. In fact we have become very complacent with both the fuel and the combustion technology and there were no major research and development on both the above issues. In fact we became completely dependent on these two issues and there was no real breakthrough either in substituting the fossil fuel or in the combustion technology. The basic reason behind this situation can be attributed to the discovery of electromagnetism, which opened the way for electricity generation as well as transportation. In both these industries, the key part is the motor which provided a rotary motion. This rotary motion generates electricity in turbines and such motion is created by combustion of a fuel, which is invariably a fossil fuel. We have carried on this for few decades before the emission of greenhouse started rising abnormally and became an issue.

We are now at cross roads wondering what the future holds for the world. Is it possible to carry on the business as usual or look for an alternative source of energy? We started looking at various sources of energy as an alternative. Any alternative energy source should meet two critical parameters namely the lower or no carbon emission and sustainability. Low carbon can be achieved by few methods. The immediate option is to maximize the energy efficiency of existing systems so that for the given input of fuel the output is much higher than what we have achieved all these years. But this increase in efficiency should be real to achieve the emission levels of greenhouse suggested by the UN panel on climate change.

The second option will be to switch over to different fuels with less carbon emission e.g., coal-fired power plants switching over to gas-fired power plants using combined cycle. Retrofitting organic Rankin cycle as a bottoming for steam turbines to squeeze out some extra energy. Decentralizing the power plants in a phased manner in favor of distributed energy systems where gas, instead of electricity, can be supplied to each industry, to generate their own power using CHP process. All these measures can help reduce the emission level but our dependency on fossil fuel will still continue.

W can look at a completely different fuel source and new technology for power generation and transportation. If we look at carefully there are not many alternative fuel sources except Hydrogen that could meet these limits. We are also trying to develop bio fuels. But biofuels are also organic chemicals with carbon backbone which will generate greenhouse emission. Moreover bio fuel sources such as palm oil, corn are also food sources. There is an indiscriminate deforestation and plantation of palm trees in tropical countries like Malaysia, Indonesia and PNG. The focus is now shifting to carbon based organic compounds like biofuel and biogas. This will create a situation where food crops will be substituted with energy crops creating food shortage.But the carbon dioxide level in the atmosphere may not be reduced drastically by these methods.

We need to develop an energy source which does not emit any carbon emission and at the same time we should be able to use existing technology to the possible extent. Only Hydrogen can meet these requirements. In the current situation it is impossible to substitute fossil fuels in a short span of time. We can cut fossil fuels by blending with Hydrogen to the most extent possible so that we can meet two goals. We can cut the carbon emission and at the same time we can deploy Hydrogen as a blended fuel with fossil fuel and not, pure Hydrogen. Since Hydrogen is a very light gas and readily forms an explosive mixture with oxygen, this opens up a new opportunity to develop Hydrogen assisted combustion process in power generation as well as in transportation. It will be easier to handle a mixture of natural gas and Hydrogen for combustion in Gas turbine, or spark ignited reciprocating engines, as well as, gasoline combustion engines in cars. This will also gives us an opportunity to develop advanced and competitive systems like Fuel cell as an alternative technology for combustion process in due course of time.

The hydrogen assisted combustion technology is much easier, faster and economical and at the same time cut the greenhouse emission to an accepted level. But the source of such Hydrogen cannot be natural gas but only renewable sources. The renewable technologies such as solar, wind, geothermal, OTEC (ocean thermal energy conversion) should generate renewable Hydrogen. This is the key for sustainability as well as for greenhouse gas mitigation. These two benefits are too attractive to ignore and it is time we move from total fossil fuel to Hydrogen blended fossil fuel. The blended fuel along with the energy efficiency measures suggested above should go hand in hand, so that we may get over this turbulent period of financial crisis and global warming.

It is also possible that Hydrogen assisted combustion be adopted for coal-fired power plants by simply firing coal slurry, finely powdered coal blended with water and conveyed pneumatically for firing boilers and also for gasification process to generate syngas for IGCC (Integrated gasification and combined cycle) applications. Syngas production will be critical in the near future for a smoother transition from fossil economy to Hydrogen economy irrespective of the route we adopt.

Water makes up seventy-one percent of the planet earth and ninety-eight percent of it makes up the ocean.  It is a single source of water for all forms of life on earth and it also plays an important role in climate changes in the atmosphere. Ocean is the biggest heat sink and absorbs sun’s heat and also a carbon sink absorbing excess carbon dioxide from atmosphere. The surface temperature of seawater is warmer than the temperature at the bottom of the ocean. Sun supplies solar energy to the ocean. In fact the water temperature in Deep Ocean is about 15-20C less than the surface temperature, and it is used as a working fluid to cool buildings by evaporative cooling without using any electricity like commercial air-conditioning.

OTEC (ocean thermal energy conversion) system is a potential method of generating power using the temperature gradient between ocean’s surface water and ocean’s deep water. A temperature difference, as small as 15 -20C is enough to generate power using Kalina cycle, like geothermal energy systems. Commercial plants using this technology are already in operation in few countries. The biggest advantage with open cycle ocean thermal energy conversion system is the fresh water (desalinated ocean water) as a by-product. This technology is unique because it can generate not only power but also drinking water from sea without polluting the air with greenhouse gas emissions. In fact this technology should be deployed commercially is many islands around the world, where there is always a demand for power and drinking water.

“Water, water, everywhere but not a drop to drink”. It is the situation in many islands and many parts of the world. Islands like Maldives and Mauritius should adopt this technology to generate power and supply drinking water without burning fossil fuels like diesel or setting up desalination plants. Of course, the economy of scale and finance is an issue in many islands.

PNG (Papua New Guinea) is one of the biggest islands in Pacific Ocean where there is s severe shortage of   power and water. The country is endowed with rich minerals, oil and gas but the basic necessity like power and water are in short supply. OTEC will be an ideal solution for such islands. Fresh water supply is going to be a major issue in parts of the world due to global warming and climate changes. In countries like India, drinking water is in short supply and a number of seawater desalination plants are coming up. Bottled waters are expensive and unaffordable to a common man. This will only increase the power requirements in the country when there is already a massive shortage of power. OTEC is an ideal solution for India with its long coastal line.

One of the major issues with current power generation technologies is the pollution. In any combustion process involving fossil fuel the combustion products like carbon dioxide, carbon monoxide and Oxides of Nitrogen (the greenhouse gases) will contribute global warming. What is the level of such emission and how fast the globe is warming is a futile argument. The pollution can be small in term of PPM (parts per million) but the cumulative effects over several decades is a major issue and that cannot be simply dismissed. There are many places where the Arsenic content in drinking water is above certain acceptable levels (only in ppms) but such small excess cause debilitating health conditions. This is the same argument with greenhouse emission and global warming. It can be gradual and insignificant but it will reach a tipping point and dramatic changes can happen all of a sudden. Nature has got its own mechanism to adjust any imbalances and keep up certain equilibrium. But humans cannot take them for granted and pollute the air and water indiscriminately. There will be a price to pay.

 

Ocean is the largest and inexhaustible source of Hydrogen. Currently Caustic soda plants use sodium chloride (salt) brine as the raw material for conversion into Caustic soda; the by-products are Hydrogen and Chlorine. Caustic soda plants are currently using Hydrogen as a fuel or use to manufacture Hydrochloric acid. They can generate on site power using Hydrogen to offset their energy cost. In both water electrolysis as well as brine electrolysis, Hydrogen is a product and Ocean water is the largest source of such Hydrogen. In fact countries should generate Hydrogen using desalinated water and OTEC power. The stored Hydrogen is a stored energy that can be used as and when required. That is why we believe ‘water and energy are two sides of the same coin’.

 

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