Ocean-the largest source of Clean energy

Water makes up seventy one percent of the planet earth and ninety eight percent of it constitutes 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 sufficient to generate power using Kalina cycle, similar to 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 maintain 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 onsite 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’.

Water- Fuel of the future

Water constitutes 71% of the planet earth and it is the most potential energy source of the future. Water is a product of combustion between Hydrogen and Oxygen, two most abundantly available elements and vital for life on earth. The bondage between Hydrogen and Oxygen is so strong that it requires certain amount of energy to separate them. Separation of Hydrogen and Oxygen using the process of Electrolysis is a well known technology. Separation of water by high temperature using Thermolysis has also been studied. In both the processes the separation of Hydrogen and Oxygen after decomposition is a key step because of the strong affinity between the two elements. Hydrogen has to be separated in a pure form without any trace of Oxygen. Currently most of Hydrogen is generated commercially by steam reforming natural gas because of its easy availability as piped gas in many developed countries. Moreover steam reforming is a well established commercial technology that has been used for decades in chemical process industries. The hydrogen resulting from steam reforming is acceptable for combusting in Hydrogen internal combustion engines but not pure enough for a Fuel cell car. Any trace of impurity from natural gas such as Sulfur or mercaptans can potentially poison the catalyst used in fuel cell which is very expensive. Hydrogen with purity less than 99.99% is not recommended for Fuel cell applications. Currently there are few issues to be addressed before Hydrogen becoming a commercial fuel. The energy required to separate Hydrogen from water by commercial electrolysis is about 6Kws (kilowatts) to generate 1 m3 (cubic meter) of Hydrogen. Two key factors for electrolysis are purity of water and DC power source. Water of certain purity is a critical component for Hydrogen generation. Deionized water with electrical conductivity less than 0.10 micro Siemens/cm is required. Normal drinking water conductivity is less than 100micro Siemens/cm. The potable water can be deionized with reverse osmosis system to get necessary quality. In fact both high purity water and direct current are not commercially available. A renewable energy sources such as solar or wind that generates direct current can be used for electrolysis. This will eliminate batteries and rectifiers that we normally use in renewable energy systems. The generated Hydrogen can be stored in cylinders under high pressure. The stored hydrogen is the stored energy that can be used as and when required. We can use the stored Hydrogen to generate electricity to meet our power requirement whether it is a home or business or industry. The major advantage with this system is that we can generate power whenever we need and we don’t have to depend on the grid power. We can also export surplus power to the grid. In fact all DC appliances can be connected with DC power from Fuel cell and operated to improve the efficiency. Such a system is ideal for remote locations without any grid supply such as remote villages or islands. The same stored Hydrogen can also be used as fuel for a car whether it is a combustion engine or a Fuel cell car. Hydrogen can be compressed and stored under high pressure. Alternatively, Hydrogen can be stored using metal hydrides in smaller volumes. Honda introduced the first fuel cell car in the market in 1999. Since then they have made considerable improvements. Honda FCX Clarity, sedan offers a mileage of 270 miles for a single cylinder of Hydrogen at 5000 psi pressure. They are introducing a latest model with Hydrogen pressure at 10,000 psi which will considerably improve the mileage further. Unlike Hybrid cars, Fuel cell cars run silently and experts who have test-driven the car are very much impressed with the performance. Similarly Ford introduced Hydrogen combustion engine 6.8 liters V-10 engine to power E-450 Hydrogen shuttle bus. Ford modified their Gasoline engine to suit Hydrogen fuel. Substituting Gasoline with Hydrogen is no longer a theory but a commercial reality. More and more research is being undertaken to improve the performance. Currently the cost of Hydrogen cars and Hydrogen fuel is expensive, due to lack of infrastructures to manufacture such cars or to distribute Hydrogen. However these cars will soon replace gasoline cars. Similarly individual homes and business can generate their own electricity for their daily use using stored Hydrogen. Water will become the fuel of the future and Hydrogen will clean up the air that has been heavily polluted by fossil fuels for decades.

Renewable Hydrogen-Future source of clean energy

I use the word ‘renewable Hydrogen’ for the Hydrogen derived from water using renewable energy sources such as solar, wind, geothermal, wave energy, ocean thermal energy conversion systems and biological processes. Hydrogen is clearly the energy source of the future because it has got the highest energy content, compared to any other fossil fuels such a diesel, gasoline, or Butane. The energy content is more than three times that of natural gas, which is currently considered as the cleanest commercial fuel available in the market. The heating value of Hydrogen is 61,100Btu/lb compared to 23,879 Btu/lb of natural gas. Moreover, only Hydrogen can guarantee a complete reduction of Carbon dioxide from the atmosphere. The problem with renewable Hydrogen is the cost, at current situation. The DOE (department of energy, USA) has targeted a cost for Hydrogen production at $10to $15 per mmBtu, which is comparable with current Natural gas cost. Currently bulk of the Hydrogen is commercially produced by steam reforming natural gas. However; this process will emit carbon dioxide at the rate of 11,888gms per Kg of Hydrogen produced. Though the cost of Hydrogen by this route is cheaper, mitigation of carbon dioxide is clearly an environmental issue. However it is an important route during the transition process from fossil fuel to a full- fledged Hydrogen economy of the future. Natural gas is increasingly in demand and the price of natural gas keeps increasing as the supply demand gap widens. Large natural gas liquefaction plants are already in operation in many parts of the world and number of new plants are under implementation or under planning stages. Japan, South Korea, Taiwan are three largest importers of LNG (liquefied natural gas) from Australia in Pacific region. There are many coal seam methane gas facilities already in operation in Australia and many are under planning. Due to the disaster at Fukashima nuclear plant, Japan has stepped up its import of LNG. India and China, which have been traditionally using coal as a major fuel, have started importing LNG for their power plants. This has pushed the prices of LNG in the international market significantly. Though LNG is relatively a cleaner fuel, it is very expensive to build import terminals. Moreover countries like India and China do not have a good distribution network by pipelines.The economy of scale also favor only large capacity LNG plants and terminals. However it is not a sustainable solution in the long run considering the fact that supply of natural gas also keeps dwindling steadily. Despite all these obstacles, Governments around the world are looking only for short term solutions like LNG, simply because it is an easy fix. Biogas can be generated from organic waste and waste waters by anaerobic digestion. Many sewage treatment plants around the world have started generating biogas to generate power and use captively and to export the surplus power to the grid. Similarly municipalities are also implementing projects to convert ‘waste garbage’ to ‘energy’. However, the scale of operation favors only large capacity plants in larger cities. However these biogas plants will still emit carbon dioxide because biogas will be combusted using conventional engines, micro turbines and Fuelcells.This is once again a temporary solution only. We need to look beyond all these technologies to really reduce the greenhouse emissions. The only option is by Renewable Hydrogen and we need to take steps to make it a commercial reality. Biohydrogen is another potential technology. However the technology is still in a nascent stage but it is promising. Renewable Hydrogen using renewable energy sources are our best bet. Countries have already started investing in renewable energy infrastructures such as solar and wind. They can as well plan for renewable Hydrogen so that they can be certain about three things. One, they can generate and use uninterrupted power supply without importing oil or gas. Secondly they can be certain that greenhouse emissions can be reduced to pre-industrialization level. Thirdly they can be certain about the final cost of energy and its stability in the long run. These are three important factors every citizen of a country is looking for. It requires political will, determination and swift action on the part of individual Governments.

Hydrogen-the key to sustainability

Renewable energy is one of the fastest growing energy sources of our times. But still there are many obstacles to overcome, before it can substitute current methods of electricity generation using fossil fuels, or substitute petrol in cars. The main obstacle is, the intermittent and unpredictable nature of renewable energy sources, such as wind and solar. Wind blows only certain seasons of the year and then wind velocity fluctuates widely in a day. Similarly sun shines only certain hours in a day and the intensity of radiation varies widely in a day. The wind velocity and sun’s radiation intensity are critical components in designing a reliable energy system. It is an anomalous situation, when we need power, there is no sun or wind; when sun shines or wind blows, we may not need any power. How to overcome this anomaly? That is the key, in successfully deploying renewable energy technologies. Currently we are using batteries to store the energy. When there is a wind with reasonable velocity or sunshine with reasonable radiation intensity, we can generate power and store them in batteries. The wind velocity should be above certain threshold limit, say for example, a minimum wind velocity of 3mts/sec for certain number of hours, while designing a wind based energy system. The same principle applies to solar energy and we need certain minimum solar intensity and number of hours. But in reality, we don’t get these minimum operating parameters, which make the design of a renewable system more complicated. Batteries can accumulate these small energy generations by intermittent sources of wind and sun, and store them. But these batteries have certain life between 3-5 years and requires regular maintenance, replacements.They also have certain charging and discharging cycles and limitations. At the end of its life, it has to be disposed carefully because these batteries are made of lead and acid, which are toxic materials. Many companies are trying to introduce better technologies such as ‘flow batteries’. But experience shows that such batteries are confined to only smaller capacities. Large scale storage is expensive and sometimes it is not economically feasible. Lithium-ion batteries are more efficient than Lead-acid batteries, but they are more expensive so the renewable energy projects become expensive and cannot compete with conventional fossil fuels, in spite of higher tariffs offered by Government as incentives. Moreover the demand for Lithium-ion batteries will increase substantially in the future, as more and more Electric cars are produced. But lithium sources are limited and it is not sustainable. The best option to develop renewable energy systems is to generate Hydrogen using renewable energy and store them, instead of storing them in batteries. We can use stored Hydrogen to generate power, or use as fuel for the car, as and when we need. There are no maintenance or disposal problems with Hydrogen storage, when comparing with batteries. Hydrogen generators (electrolyzers) can generate Hydrogen whenever the intermittent power flows from wind or sun. They can operate from a wide range of capacities from 5 to 100% of rated capacity and they are more suitable for renewable energy sources. But there will be a loss of energy, because the amount of power required to generate Hydrogen, is more than the power generated from the resulting Hydrogen by a Fuelcell.The initial cost will be higher, but it will give operational flexibility with least maintenance, and even adoptable to remote sites. Technology is improving to reduce the cost of fuel cells and electrolyzers so that Hydrogen based renewable energy will become a sustainable source of energy in the future. Hydrogen is the only solution that can solve both power generation and transportation problems the world is currently facing.