Liquid biomethane- an emerging fuel for rural economy.

Biogas is fast becoming a fuel of the choice for rural economy in many parts of the world because large number of agriculture and farming communities lives in rural area. Most of these countries depend on imported Diesel, LPG and Gasoline for their industries, agriculture, transportation and cooking. Countries like India with large population spends huge amount of foreign currency towards import of petroleum products, making it more vulnerable to the fluctuating oil and gas prices in the international market. However, there is an increasing awareness in India recently about the importance of generating biogas as an alternative energy source to fossil fuel because 70% of the Indian population lives in rural areas. With an estimated cattle population of 280 million (National Dairy development Board 2010) there is a potential to generate biogas at 19,500 Mw. The following calculation is based on the costing details provided by successful case studies of community based Biogas plants in India. One community based biogas plant has 121 families consisting of 5 members per family as stake holders. They supply cow dung at the rate of 4.50 Mt/day for 365days in a year and generate biogas by an anaerobic digester, designed and constructed locally. Biogas is supplied to all the stakeholders every day for 2 hrs in the morning and for about 2 hrs in the evening for cooking. This is equivalent to burning 3025 kgs of wood/day (121 families x 5members/family x 5kg wood per member= 3025 x 4000 kcal/kg= 12.10 mil Kcal/day= 48.40 mmBtu/day).The piped natural gas in India is supplied currently at the rate of $16/mm Btu, which means the plant is able to generate revenue worth $774.40 per day. But each family of 5 members are charged only Rs.150 per month or 121 families are charged 121 x Rs.150= Rs.18, 150/month ($363/month). The family members also supply milk to co-operative dairy farm which has also contributed to set up the biogas plant. Total cost of the project is $43,000 of which Government subsidy is $20,000, Dairy farm contribution $ 16,000 and the stake holders $7000.The economic and social benefit of this project is enormous. The economic benefit by way of fuel savings, revenue from the sale of vermin compose and by way of Carbon credit amounts to Rs.48,94,326 ($97,926/yr).(source:SUMUL). The above case study clearly shows how successfully India can adopt bioenergy as an alternative to fossil fuel in rural areas. We have already seen how biogas can be enriched to increase its methane content and to remove other impurities by way of water scrubbing as shown in the figure. The purified and dried biogas with Methane content 97% and above can be liquefied using cryogenic process by chilling to -162C.The liquefaction of biogas is energy intensive but it is worth doing in countries like India especially when there is no natural gas pipeline network.BLG (liquefied biogas) is an ideal fuel for industries with CHP (combined heat and power) applications with energy efficiency exceeding 80% compared to conventional diesel engine efficiency at 30%.By installing LBG service station and catering to transport industry, India can reduce their import of crude oil while reducing the greenhouse gas emissions. Producing LBG also leads to a renewable fuel available for heavier vehicles. The fuel can be stored as LBG on the vehicle, which increase the driving distance per tank. The requirement is that the vehicle is running frequently, otherwise LBG will vaporize and CH4 will be vented to the atmosphere. LBG is in liquid form only when the gas is stored on the vehicle. When it gets to the engine it is in its gas phase. When LBG is delivered to remote fuel stations or storages it is transported in vacuum insulated pressure vessels. One such manufacture of these semi-trailers is Cryo AB and the dimensions of a standard equipped semi-trailer, suitable for Nordic logistic conditions, is shown in Figure 13. This trailer is optimized for the transportation of LNG/LBG and has a tank capacity of 56,000 liters (~33,000 Nm3 LBG). It is vacuum insulated and the heat in-leakage is less than 0.9 % of maximum payload LBG per 24 hour. The maximum payload is 83.7 % filling rate at 0 bar (g) (=19,730 kg). The source of heat is the surrounding air and the heat in-leakage raises the pressure of the LBG. The maximum working pressure is 7.0 bar (g). If this pressure is exceeded gas is vented to the atmosphere through a safety valve. (Cryo AB, 2008) Fuel station technology: There are three different types of fuel station available, using LBG as a feed stock: - LBG refueling station - LCBG refueling station - Multi-purpose refueling station LBG stations fuel LBG to vehicles equipped with a cryogenic tank while LCBG stations refuel CBG. LCBG stands for liquid to compressed biogas and LBG is transformed to CBG at the refueling station. Multi-purpose refueling stations are able to fuel both LBG and CBG, and consist of one LBG part and one LCBG part. (Vanzetti Engineering, 2008a) There are a number of companies in the LNG business working with the development of fuel stations using LBG as a feedstock. The presented data in this text is based on information from three different companies; Cryostat, Nexgen fuels and Vanzetti Engineering. This article will focus on the multi-purpose station and since the three companies’ designs are very similar, only a general description will be presented. The reason why the multi-purpose station is chosen is because LBG could be a good alternative for heavier vehicles. Here it is assumed that these vehicles already are available and in use on a large extent. The refueling station assumes to be situated in conjunction with one of the frequent roads in India, not in vicinity with the gas network. The following requirements lie as a background for the design: - Possibility to fuel both LBG and CBG - One double dispenser for CBG; one nozzle for vehicles (NGV-1) and one nozzle for busses (NGV-2) - One single nozzle for LBG - Expected volume of sale: 3000 Nm3/day - Pressure on CBG: up to 230 bar (200 bars at 15°C) The standard equipment on the multi-purpose station consists of a storage tank for LBG, cryogenic pumps, ambient vaporizer, odorant injection system and dispensers. (Cryostat, 2008a) There are three types of cryogenic pumps: - Reciprocating - Centrifugal - Submerged Reciprocating pumps are able to function at very high pressures and are therefore used for the filling of buffer tanks and gas cylinders. Centrifugal pumps are able to produce high flow rates and are used for the transfer of cryogenic liquids between reservoir tanks or road tankers. (Cryostat, 2008b) A submerged pump is a centrifugal pump installed inside a vacuum insulated cryogenic tank. This tank is totally submerged in the cryogenic liquid, which makes it stay in permanently cold conditions. (Vanzetti Engineering, 2008b) A sketch over a multi-purpose station can be seen in Figure 14. LBG is stored in a vacuum insulated cryogenic vessel and LBG is delivered with semi-trailers. The volume of the storage tank is usually designed to match refilling on a weekly basis. The transfer from trailer is either done by gravity or by transfer pumps, the latter significantly reducing transfer time. (Vanzetti Engineering, 2008a) From the LBG storage tank the station is divided into two; the LBG part and the LCBG part. The LCBG part consists of a reciprocating pump, an ambient vaporizer and buffer storage. The reciprocating pump sucks LBG from the storage tank and raises the pressure to around 300 bars, before sending it to the ambient high pressure vaporizer. CBG is then odorized before going to the CBG storage and the dispenser. The buffer unit is gas vessel storage, with a maximum working pressure of 300 bar, enabling fast filling of vehicles. (Nexgen Fueling, 2008) The LBG part only consists of a centrifugal pump that transfers LBG from the storage tank, through vacuum insulated lines, to the LBG dispenser that dispense LBG at a pressure of 5-8 bar. (Nexgen Fueling, 2008) Some LBG dispensers are supplied with a system for the recovery of the vehicle boil of gas. (Cryostar, 2008a) To reduce methane losses all venting lines are collected and sent back to the higher parts of the storage tank, to be reliquaries by the cold LBG. (Heisch, 2008) (Ref: Nina Johanssan, Lunds Universitet) Economics of LBG: The LNG trucks averages about 2.8 miles per gallon of LNG, equating to about 4.7 miles per DEG. Table 5 compares the energy content, fuel economy and DEG fuel economy. The greenhouse emission is completely eliminated by using LBG.

Can Bio-gasification transform our world?

Carbon neutral biomass is becoming a potential alternative energy source for fossil fuels in our Carbon constrained economy. More and more waste –to-energy projects is implemented all over the world due to the availability of biomass on a larger scale; thanks to the increasing population and farming activities. New technological developments are taking place side by side to enhance the quality of Biogas for power generation. Distributed power generation using biogas is an ideal method for rural electrification especially, where grid power is unreliable or unavailable. Countries like India which is predominantly an agricultural country, requires steady power for irrigation as well as domestic power and fuel for her villages. Large quantity of biomass in the form of agriculture waste, animal wastes and domestic effluent from sewage treatment plants are readily available for generation of biogas. However, generation of biogas of specified quality is a critical factor in utilizing such large quantities of biomass. In fact, large quantity of biomass can be sensibly utilized for both power generations as well as for the production of value added chemicals, which are otherwise produced from fossil fuels, by simply integrating suitable technologies and methods depending upon the quantity and quality of biomass available at a specific location. Necessary technology is available to integrate biomass gasification plants with existing coal or oil based power plants as well as with chemical plants such as Methanol and Urea. By such integration, one can gradually change from fossil fuel economy to biofuel economy without incurring very large capital investments and infrastructural changes. For example, a coal or oil fired power plant can be easily integrated with a large scale biomass plant so that our dependency on coal or oil can be gradually eliminated. Generation of biogas using anaerobic digestion is a common method. But this method generates biogas with 60% Methane content only, and it has to be enriched to more than 95% Methane content and free from Sulfur compounds, so that it can substitute piped natural gas with high calorific value or LPG (liquefied petroleum gas). Several methods of biogas purification are available but chemical-free methods such as pressurized water absorption or cryogenic separation or hollow fiber membrane separation are preferred choices. The resulting purified biogas can be stored under pressure in tanks and supplied to each house through underground pipelines for heating and cooking. Small business and commercial establishments can generate their own power from this gas using spark-ignited reciprocating gas engines (lean burnt gas engines) or micro turbines or PAFCs (phosphoric acid fuel cells) and use the waste heat to air-condition their premises using absorption chillers. In tropical countries like India, such method of distributed power generation is absolutely necessary to eliminate blackouts and grid failures. By using this method, the rural population need not depend upon the state owned grid supplies but generate their own power and generate their own gas, and need not depend on the supply of rationed LPG cylinders for cooking. If the volume of Bio-methane gas is large enough, then it can also be liquefied into a liquified bio-methane gas (LBG) similar to LNG and LPG. The volume of bio-methane gas will be reduced by 600 times, on liquefaction. It can be distributed in small cryogenic cylinders and tanks just like a diesel fuel. The rural population can use this liquid bio-methane gas as a fuel for transportation like cars, trucks, buses, and farm equipments like tractors and even scooters and auto-rickshaws. Alternatively, large-scale biomass can be converted into syngas by gasification methods so that resulting biomass can be used as a fuel as well as raw materials to manufacture various chemicals. By gasification methods, the biomass can be converted into a syngas (a mixture of Hydrogen and Carbon monoxide) and free from sulfur and other contaminants. Syngas can be directly used for power generation using engines and gas turbines. Hydrogen rich syngas is a more value added product and serves not only as a fuel for power generation, but also for cooking, heating and cooling. A schematic flow diagram Fig 3, Fig4 and Fig 6 (Ref: Mitsubhisi Heavy Industries Review) shows how gasification of biomass to syngas can compete with existing fossil fuels for various applications such as for power generation, as a raw material for various chemical synthesis and as a fuel for cooking, heating and cooling and finally as a liquid fuel for transportation. Bio-gasification has a potential to transform our fossil fuel dependant world into Carbon-free world and to assist us to mitigate the global warming.

Hydrogen from seawater for Fuelcell

We have used Hydrocarbon as the source of fuel for our power generation and transportation since industrial revolution. It has resulted in increasing level of man-made Carbon into the atmosphere; and according to the scientists, the level of carbon has reached an unsustainable level and any further emission into the atmosphere will bring catastrophic consequences by way of climate change. We have already witnessed many natural disasters in a short of span of time. Though there is no direct link established between carbon level in the atmosphere and the global warming, there is certainly enough evidence towards increase in the frequency of natural disasters and increase in the global and ocean temeperatures.We have also seen that Hydrogen is a potential candidate as a source of future energy that can effectively substitute hydrocarbons such as Naphtha or Gasoline. However, hydrogen generation from water using electrolysis is energy intensive and the source of such energy can come only from a renewable source such as solar and wind. Another issue with electrolysis of water for Hydrogen generation is the quality of water used. The quality of water used for electrolysis is high, meeting ASTM Type I Deionized Water preferred, < 0.1 micro Siemen/cm (> 10 megOhm-cm). A unique desalination technology has been developed by an Australian company to generate onsite Hydrogen directly from seawater. In conventional seawater desalination technology using reverse osmosis process only 30-40% of fresh water is recovered as potable water with TDS less than 500 ppm as per WHO standard. The balance highly saline concentrate with TDS above 65,000 ppm is discharged back into the sea which is detrimental to the ocean’s marine life. More and more sweater desalination plants are set up all over the world to mitigate drinking water shortage. This conventional desalination is not only highly inefficient but also causes enormous damage to the marine environment. The technology developed by the above company will be able to recover almost 75% of fresh water from seawater and also able to convert the concentrate into Caustic soda lye with Hydrogen and Chlorine as by-products by electrolysis. The discharge into the sea is drastically reduced to less than 20% with no toxic chemicals. This technology has a potential to revolutionize the salt and caustic soda industries in the future. Caustic soda is a key raw material for a number of chemical industries including PVC.Conventionally, Caustic soda plants all over the world depends on solar salt for their production of Caustic soda.Hydrogne and Chlorine are by-products.Chlrine is used for the production of PVC (poly vinyl chloride) and Hydrogen is used as a fuel. In the newly developed technology, the seawater is not only purified from other contaminants such as Calcium, Magnesium and Sulfate ions present in the seawater but also concentrate the seawater almost to a saturation point so that it can be readily used to generate Hydrogen onsite. The process is very efficient and commercially attractive because it can recover four valuable products namely, drinking water, Caustic soda lye, Chlorine and Hydrogen. The generated Hydrogen can be used directly in a Fuel cell to generate power to run the electrolysis. This process is very ideal for Caustic soda plants that are currently located on seashore. This process can solve drinking water problems around the world because potable water becomes an industrial product. The concentrated seawater can also be converted in a salt by crystallization for food and pharmaceutical applications. There is a growing gap between supply and demand of salt production and most of the chemical industries are depending upon the salt from solar pans. Another potential advantage with this technology is to use wind power to desalinate the water. Both wind power and Hydrogen will form a clean energy mix. It is a win situation for both water industry and the environment as well as for the salt and chemical industries. In conventional salt production, thousands of hectares of land are used to produce few hundred tons of low quality salt with a year long production schedule. There is a mis- match between the demand for salt by large Caustic soda plants and supply from primitive methods of solar production by solar evaporation contaminating cultivable lands. The above case is an example of how clean energy technologies can change water, salt and chemical industries and also generate clean power economically, competing with centralized power plants fuelled with hydrocarbons. Innovative technologies can solve problems of water shortage, greenhouse gases, global warming, and environmental pollution not only economically but also environmental friendly manner. Industries involved in seawater desalination, salt production, chemical industries such as Caustic soda, Soda ash and PVC interested to learn more on this new technology can write directly to this blog address for further information.

Fuelcell power using Biogas

Fuel cell technology is emerging as a base-load power generation technology as well as back-up power for intermittent renewable energy such as solar and wind, substituting conventional storage batteries. However, Fuelcell requires a Fuel in the form of Hydrogen of high purity. The advantage of Fuel cell is, its high electrical efficiency compared to conventional fossil fuel power generation technology, using Carnot cycle. Fuel cell is an electro-chemical device similar to a battery and generates power using electro-chemical redox reaction silently with no gaseous emission, unlike engines and turbines with combustion, rotary movements and gaseous emissions. The fuel Hydrogen can be generated using a renewable energy sources such as solar and wind as described in my previous articles, “Solar Hydrogen for cleaner future” dated 4 July 2012, and “Renewable Hydrogen for remote power supply “dated 28 June 2012. Alternatively, Hydrogen can also be generated using biomass through Biogas. Biogas is an important source of renewable energy in the carbon constrained economy of today’s world. The biogas can be generated from waste water and agro-waste by anaerobic digestion using enzymes. Biomass such as wood waste can also be gasified to get syngas, a mixture of Hydrogen and Carbon dioxide. In anaerobic digestion, the main product will be methane gas accompanied by carbon dioxide and nitrogen while the main product in gasification will be Hydrogen, cabon monoxide and carbon dioxide and oxides of Nitrogen. Whatever may be the composition of the resulting gas mixture, our focus will be to separate methane or Hydrogen from the above mixture. In anaerobic digestion, the resulting Methane gas has to be steam reformed to get Hydrogen gas suitable for Fuel cell application. In gasification, the resulting Syngas has to be separated into pure Hydrogen and Carbon dioxide so that pure Hydrogen can be used as a fuel in Fuel cell applications. As I have outlined in many of my previous articles, Hydrogen was the only fuel we have been using all these years and we are still using it in the form of Hydrocarbons and it will continue to be the fuel in the future also. The only difference is future Hydrogen will be free from carbon. We have to address two issues to mitigate Carbon emission, and it can be done by 1.Elimination of Carbon from the fuel source. 2. Generation of Renewable and Carbon free clean energy directly from solar and wind. One option to eliminate Carbon from the fuel source is to use Biomass as the raw material to generate Hydrogen so that fresh Carbon will not be added into the atmosphere by emissions .The second option is to generate pure Hydrogen from water by electrolysis using renewable energy such as wind and solar. Environmentally friendly waste-to-energy projects are becoming popular all over the world. But currently most of these waste-to-energy projects generate either Biogas (Methane) by anaerobic digestion or Syngas (Hydrogen and Carbon dioxide) by gasification. Both these gases require further purification before they can be used as a fuel for power generation. The Methane content in the Biogas (about 60% methane and 40% Carbon dioxide with other impurities) needs to be enriched to 90% Methane and free from other impurities. The composition of a typical Biogas is shown in table1. The resulting purified methane gas will be reformed using steam reformation in presence of a catalyst to obtain syngas; finally Hydrogen should be separated from resulting syngas so that it can be used directly into the Fuelcell.The common Fuel cell used for this application is invariably Phosphoric acid fuel cell. PAFC uses 100% Phosphoric acid in Silicon carbide matrix as an electrolyte. PAFC is a self contained unit completely enclosed in a cabin consisting of a gas reformer, Fuellcell power generator, Power conditioning unit and other auxiliaries. The PAFC is of modular construction with capacities ranging from 100Kw up to 500Kw as a single unit. It can be installed outdoor in the open and it can be readily connected to a piped Biogas. It can also be connected to existing piped natural gas or LPG bullet as a stand-by fuel. Any waste-to energy project can be integrated with Fuel cell power generation with CHP application to get maximum economic and environmental benefits. Hydrogen derived from biomass will be an important source of fuel in the future of clean energy; and Fuel cell will become an alternative power generation technology for both stationary power generation and transportation such as Fuel cell car or Hybrid cars. PAFC is a compact, self-contained power generation unit that is used even for base load power. The electrical efficiency of PAFC is about 42% .It is suitable for CHP applications so that the total energy efficiency can reach up to 85%.It is ideal for supplying continuous power 24x7 and also to use waste heat for space heating or space air-conditioning with an absorption chiller in CHP applications. The ideal candidates for PAFC power generation using CHP will be hospitals, super markets, Data centers, Universities or any continuous process industry.PAFC is currently used as a backup power for large scale renewable energy project with an access to piped natural gas. A schematic flow diagram of a fuel cell power generation is shown in Fig 3 using biogas at Yamagata sewage treatment plant in Japan. Biomass based Fuecell power generation has a great potential all over the world irrespective of location and size of the country.

Fuelcell or battery for Renewable energy back-up?

Batteries have become indispensable for energy storage in renewable energy systems such as solar and wind. In fact the cost of battery bank, replacements, operation and maintenance will exceed the cost of PV solar panels for off grid applications during the life cycle of 20 years. However, batteries are continued to be used by electric power utilities for the benefits of peak shaving and load leveling. Battery energy storage facilities provide the dynamic benefits such as voltage and frequency regulation, load following, spinning reserve and power factor correction along with the ability to provide peak power. Fuel cell power generation is another attractive option for providing power for electric utilities and commercial buildings due its high efficiency and environmentally friendly nature. This type of power production is especially economical, where potential users are faced with high cost in electric power generation from coal or oil, or where environmental constraints are stringent, or where load constraints of transmission and distribution systems are so tight that their new installations are not possible. Both batteries and fuel cells have their own unique advantages to electric power systems. They also contain a great potential to back up severe PV power fluctuations under varying weather conditions. Photovoltaic power outputs vary depending mainly upon solar insolation and cell temperature. PV power generator may sometimes experience sharp fluctuations owing to intermittent weather conditions, which causes control problems such as load frequency control, generator voltage control and even system stability. Therefore there is a need for backup power facilities in the PV power generation. Fuel cells and batteries are able to respond very fast to load changes because their electricity is generated by chemical reactions. A 14.4kW lead acid battery running at 600A has maximum load gradient of 300 A/sec, a phosphoric-acid fuel cell system can match a demand that varies by more than half its rated output within 0.1 second. The dynamic response time of a 20kW solid-oxide fuel cell power plant is less than 4 second when a load increases from 1 to 100%, and it is less than 2 msec when a load decreases from 100 to 1%. Factory assembled units provides fuel cell and battery power plants with short lead-time from planning to installation. This modular production enables them to be added in varying increments of capacity, to match the power plant capacity to expected load growth. In contrast, the installation of a single large conventional power plant may produce excess capacity for several years, especially if the load growth rate is low. Due to their multiple parallel modular units and absence of combustion and electromechanical rotary devices, fuel cell and battery power plants are more reliable than any other forms of power generation. Fuel cells are expected to attain performance reliability near 85%. Consequently, a utility that installs a number of fuel cell or battery power plants is able to reduce its reserve margin capacity while maintaining a constant level of the system reliability. The electrochemical conversion processes of fuel cells and batteries are silent because they do not have any major rotating devices or combustion. Water requirement for their operation is very little while conventional power plants require massive amount of water for system cooling. Therefore, they can eliminate water quality problems created by the conventional plants’ thermal discharges. Air pollutant emission levels of fuel cells and batteries are none or very little. Emissions of SO2 and NOx in the fuel cell power plant are 0.003 lb/MWh and 0.0004 lb/MWh respectively. Those values are projected to be about 1,000 times smaller than those of fossil-fuel power plants since fuel cells do not rely on combustion process. These environmentally friendly characteristics make it possible for those power plants to be located close to load centers in urban and suburban area. It can also reduce energy losses and costs associated with transmission and distribution equipment. Their location near load centers may also reduce the likelihood of power outage. Electricity is produced in a storage battery by electro-chemical reactions. Similar chemical reactions take place in a fuel cell, but there is a difference between them with respect to fuel storage. In storage batteries chemical energy is stored in the positive/negative electrodes of the batteries. In fuel cells, however, the fuels are stored externally and need to be fed into the electrodes continuously when the fuel cells are operated to generate electricity. Power generation in fuel cells is not limited by the Carnot Cycle in the view that they directly convert available chemical free energy to electrical energy than going through combustion processes. Therefore fuel cell is a more efficient power conversion technology than the conventional steam-applying power generations. Fuel cell is a one-step process to generate electricity, the conventional power generator has several steps for electricity generation and each step incurs certain amount of energy loss. Fuel cell power systems have around 40-60% efficiencies depending on the type of electrolytes. For example, the efficiencies of phosphoric-acid fuel cells and molten-carbonate fuel cells are 40-45% and 50-60%, respectively. Furthermore, the fuel cell efficiency is usually independent of size; small power plants operate as efficiently as large ones. Battery power systems themselves have high energy efficiencies of nearly 80%, but their overall system efficiencies from fuel through the batteries to converted ac power are reduced to below 30%. This is due to energy losses taking place whenever one energy form is converted to another A battery with a rated capacity of 200Ah battery will provide less than 200 Ah. At less than 20A of discharge rates, the battery will provide more that 200 Ah. The capacity of a battery is specified by their time rate of discharge. As the battery discharges, its terminal voltage, the product of the load current and the battery internal resistance gradually decreases. There is also a reduction in battery capacity with increasing rate of discharge. At 1-hr discharge rate, the available capacity is only 55% of that obtained at 20-hr rate. This is because there is insufficient time for the stronger acid to replace the weak acid inside the battery as the discharge proceeds. For fuel cell power systems, they have equally high efficiency at both partial and full loads. The customer’s demand for electrical energy is not always constant. So for a power utility to keep adjustment to this changing demand, either large base-load power plants must sometimes operate at part load, or smaller peaking units must be used during periods of high demand. Either way, efficiency suffers or pollution increases. Fuel cell systems have a greater efficiency at full load and this high efficiency is retained as load diminishes, so inefficient peaking generators may not be needed. Fuel cells have an advantage over storage batteries in the respect of operational flexibility. Batteries need several hours for recharging after they are fully discharged. During discharge the batteries’ electrode materials are lost to the electrolyte, and the electrode materials can be recovered during the recharging process. Over time there is a net loss of such materials, which may be permanently lost when the battery goes through a deep discharge. The limited storage capacity of the batteries implies that it is impossible for them to run beyond several hours. Fuel cells do not undergo such material changes. The fuel stored outside the cells can quickly be replenished, so they do not run down as long as the fuel can be supplied. The fuel cells show higher energy density than the batteries when they operate for more than 2 hours. It means that fuel cell power systems with relatively small weight and volume can produce large energy outputs. That will provide the operators in central control centers for the flexibility needed for more efficient utilization of the capital-intensive fuel cell power plants. In addition, where hydrogen storage is feasible, renewable power sources can drive an electrolysis process to produce hydrogen gas during off-peak periods that will be used to operate the fuel cells during peak demands. The usage of storage batteries in an electric utility industry is expected to increase for the purposes of load leveling at peak loads, real-time frequency control, and stabilizing transmission lines. When integrated with photovoltaic systems, the batteries are required to suppress the PV power fluctuations due to the changes of solar intensity and cell temperature. The fact that the PV power outputs change sharply under cloudy weather conditions makes it hard to decide the capacity of the battery power plants since their discharging rates are not constant. For a lead-acid battery, the most applicable battery technology for photovoltaic applications to date, the depth of discharge should not exceed 80% because the deep discharge cycle reduces its effective lifetime. In order to prevent the deep discharge and to supplement varying the PV powers generated on cloudy weather days, the battery capacity must be large. Moreover, the large battery capacity is usually not fully utilized, but for only several days. Fuel cells integrated with photovoltaic systems can provide smoother operation. The fuel cell system is capable of responding quickly enough to level the combined power output of the hybrid PV-fuel cell system in case of severe changes in PV power output. Such a fast time response capability allows a utility to lower its need for on-line spinning reserve. The flexibility of longer daily operation also makes it possible for the fuel cells to perform more than the roles of gas-fired power plants. Gas turbines are not economical for a purpose of load following because their efficiencies become lower and operating costs get higher at less than full load conditions Fuel cell does not emit any emission except water vapor and there is absolutely no carbon emission. However, storage batteries themselves do not contain any environmental impacts even though the battery charging sources produce various emissions and solid wastes. When an Electrolyzer is used to generate Hydrogen onsite to fuel the Fuel cell, the cost of the system comes down due to considerable reduction in the capacity of the battery. The specific cost of energy and NPC is lower than fully backed battery system. During dismantling, battery power plants require significant amount of care for their disposal to prevent toxic materials from spreading around. All batteries that are commercially viable or under development for power system applications contain hazardous and toxic materials such as lead, cadmium, sodium, sulfur, bromine, etc. Since the batteries have no salvage value and must be treated as hazardous wastes, disposal of spent batteries is an issue. Recycling batteries is encouraged rather than placing them in a landfill. One method favoring recycling of spent batteries is regulation. Thermal treatment for the lead-acid and cadmium-containing batteries is needed to recover lead and cadmium. Sodium-sulfur and zinc bromine batteries are also required to be treated before disposal. Both batteries and fuel cells are able to respond very fast to system load changes because they produce electricity by chemical reactions inside them. Their fast load-response capability can nicely support the sharp PV power variations resulted from weather changes. However, there are subtle different attributes between batteries and fuel cells when they are applied to a PV power backup option. Power generation in fuel cell power plants is not limited by the Carnot Cycle, so they can achieve high power conversion efficiency. Even taking into account the losses due to activation over potential and ohmic losses, the fuel cells still have high efficiencies from 40% to 60%. For example, efficiencies of PAFCs and MCFCs are 40-45% and 50-60% respectively. Battery power plants, on the other hand, themselves have high energy efficiency of nearly 80%, but the overall system efficiency from raw fuel through the batteries to the converted ac power is reduced to about 30%. A battery’s terminal voltage gradually decreases as the battery discharges due to a proportional decrease of its current. A battery capacity reduces with increasing rate of discharge, so its full capacity cannot be utilized when it discharges at high rates. On the other hand, fuel cell power plants have equally high efficiency at both partial and full loads. This feature allows the fuel cells to be able to follow a changing demand without losing efficiency. The limited storage capacity of batteries indicates that it is impossible for them to run beyond several hours. The batteries when fully discharged need several hours to be recharged. For its use in PV power connections, it is as hard to estimate the exact capacity of the batteries. In order to prevent the batteries’ deep discharge and to supplement the varying PV powers on some cloudy weather days, the battery capacity should be large, but that large capacity is not fully utilized on shiny days. For fuel cells, they do not contain such an operational time restriction as long as the fuel can be supplied. Thus, the fuel cell power plants can provide operational flexibility with the operators in central control centers by utilizing them efficiently. As intermediate power generation sources, fuel cell power plants may replace coal-fired or nuclear units under forced outage or on maintenance. For the PV power backup the batteries’ discharge rate is irregular and their full capacity may usually not be consumed. So, it is difficult to design an optimal capacity of the battery systems for support of the PV power variations and to economically operate them. Instead of batteries fuel cell power plants exhibit diverse operational flexibility for either a PV power backup or a support of power system operation.