Fuelcell can become a commercial reality

We now generate electric city from heat, obtained by combustion of fossil fuel such as coal, oil and gas. But such combustion generates not only heat but also greenhouse gases such as Carbon dioxide and oxides of Nirogen.The only alternative to generate power without any greenhouse gas emission is to use a fuel with zero carbon. However, oxides of Nitrogen will still be an issue as long as we use air for combustion because atmospheric air has almost 79% Nitrogen and 21% oxygen. Therefore it becomes necessary to use an alternative fuel as well as an alternative power generation technology in the future to mitigate greenhouse problems.

Hydrogen is an ideal fuel to mitigate greenhouse gases because combustion of Hydrogen with oxygen from air generates only water that is recyclable. Combining Hydrogen with Oxygen using Fuel cell, an electrochemical device is certainly an elegant solution to address greenhouse problems. But why Hydrogen and Fuel cell are not commonly available? Hydrogen is not available freely even though it is abundantly available in nature. It is available as a compound such as water (H2O) or Methane (CH4) and Ammonia (NH3). First we have to isolate Hydrogen from this compound as free Hydrogen and then store it under pressure. Hydrogen can easily form an explosive mixture with Oxygen and it requires careful handling. Moreover it is a very light gas and can easily escape. It has to be compressed and stored under high pressure.

Generation of pure Hydrogen from water using Electrolysis requires more electricity that it can generate. However, Hydrogen cost can be reduced using renewable energy source such as solar thermal. The solar thermal can also supply thermal energy for decomposing Ammonia into Hydrogen and Nitrogen as well as to supply endothermic heat necessary for steam reformation of natural gas into Hydrogen. On-site Hydrogen generation using solar thermal using either electricity or heat can become a commercial reality. Hydrogen generation at higher temperatures such as Ammonia decomposition or steam reformation can be directly used in Fuel cell such as Phosphoric acid Fuel cell.

Phosphoric acid fuel cell is a proven and tested commercial Fuel cell that is used for base load power generation. It is also used for CHP applications. Hydrogen generation using solar thermal and power generation using Fuel cell is already a commercial reality and also an elegant solution to mitigate greenhouse gases. Large scale deployment of Fuel cell and solar thermal will also cut the cost of installations and running cost competing with fossil fuel.Fuecell technology has a potential to become a common solution for both power generation and transportation.

While Government can encourage renewable energy by subsidizing PV solar panels and discourage fossil fuel by imposing carbon tax, they should give preference and higher tariff for power purchase from Solar thermal and Fuel cell power generators. This will encourage large-scale deployment of Fuel cell as a potential base load power source.

Solar thermal for base load power

The city of Athens hosted its oldest tradition of lighting the Olympic torch for the 2012 London Olympic Games on Thursday in Olympia. The torch was lit by solar power; using parabolic mirror to redirect the sun’s light to light the flame with purest natural light. The thermal energy of sun’s light can be powerful when focused to a point and it can reach a temperature as much as 600C.The parabolic trough with reflective mirror focuses the sunlight on the tube called ‘collectors’ in which a fluid with high boiling point is circulated. The hot fluid in turn is used to convert water into steam in boiler. The hot oil transfers its heat to the water in a heat exchanger and returns back to the parabolic trough. It is a closed circuit system. The hot oil at 390C generates steam at 370C at 100 bar pressure, which is used to run a HP steam turbine. The standard steam condensing cycle generates power similar to fossil fuel fired power plant. A 50 Mw Trough plant in Israel (Negev Desert) is already in operation.

The capacity of such plant can be easily expanded by adding modular parabolic troughs and collectors and the plant can be designed to meet  specific power demands. This is a straight forward method to generate base load power using standard steam cycle. The efficiency of such system will be 41% maxium.However recently few companies are trying use a combined cycle. This increase the solar to heat efficiency from 50.5% to 53.6%.This nominal 50Mw power plant generates  a total peak power of 57.10Mw using a solar collection area of 310,028m2 with annual solar to electrical efficiency at 16.3% using a water-cooled condenser in the steam cycle. The cost of energy works out to $0.23 to $ 0.25 /kwhrs.

By using a central solar collection tower (Heliostat) and bottoming with Rankin/Kalina cycle ,it is estimated that the total installed cost can be reduced by 10%.The system can be configured from 2Mw up to 100Mw using both trough and tower system. The system can be installed in any remote, arid locations using air condensers, where cooling water is a problem. The estimated annual specific energy cost is less than 6 cents/kwhrs, comparable to low-cost fossil energy but with zero pollution and with zero carbon emission.

Solar thermal is a potential clean energy of the future for many countries around the world with yearlong sunshine with good intensisty.The solar thermal energy can also be used in many process industries where thermal heating is required. Solar salt pans can use solar thermal energy very efficiently to cut their production cycle. The concentrated brine can be used as a circulation fluid in solar collectors and also be used to generate power using low heat technologies like Kalina cycle, because concentrated salt brine can store thermal heat.

Gemasolar power in Spain is a base load power station supplying power for 25,000 homes 24×7 using molten salt (60% KNO3+40% NaNO3) as a thermal storage medium instead of batteries. Nine plants were built in 1980 in Mojave Desert with a combined capacity of 354 Mws.

Other examples of solar base load power plants are Blythe solar with capacity of 968Mw at Riverside County, California and Ivanpah power station with capacity of 370 Mw capacities in US. Large scale solar base load plants are no longer a theory but a commercial reality.

Direct solar lighting is also being introduced using fiber optics. The sun light is collected at a central point and directed through fiber optics to various rooms inside the building supplying direct sun light. This saves not only electricity but also provides natural light to work places because human body requires a certain amount of UV light exposure. Solar energy is here to stay and offer various clean energy solutions in the future.