‘Clean Energy and Water Technologies’ is now a social enterprise based in Melbourne, Australia. The purpose of this enterprise is to introduce a zero emission technology developed and patented by Ahilan Raman, the inventor of the technology. A 25 Mw demonstration plant will be installed to show case the above technology. This platform also used as a blog will publish articles relevant to Zero emission technologies for power and Zero liquid discharge technologies for water industries.
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 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.
A safe and clean water is becoming a scarce commodity in many parts of the world. With growing population and rapid industrialization, the demand for water has increased dramatically. This in turns pushes the demand for energy and fossil fuels resulting in further increase in global warming. According to WHO (World Health organization) specifications, a clean and safe water should be free from pathogenic organism such as bacteria and virus, and also the TDS (Total dissolved solids) levels should be below 500ppm (parts per million). Unfortunately such quality water is not readily available from surface or ground water. The water stored in catchment area for supply of drinking water to cities requires certain chemical and biological treatments before it can meet WHO specification.
In many smaller cities especially in developing countries such treated drinking water is not available. NASA’s Gravity Recovery and Climate Experiment Satellite or GRACE orbiting earth in tandem, two satellites are able to measure the water storage on ground and below across the world. The NASA data shows that most of area in Northern India will be facing a severe shortage of water in the near future because farmers are pumping ground water at an alarming rate. The ground water is getting depleted faster than it is being replenished. The water table has gone deeper and deeper and many of the pumps they used five to ten years ago cannot pump water anymore because the water levels have gone so deep. States like Punjab, supposed to be ‘wheat bowl of India’ are facing water shortage. Farmers who have used 100 feet bore well are now digging their bore well up to 900 feet. To make the situation worse, a large number of coal fired power plants are licensed to meet the increasing power demand in India. Both quantity and quality of water has a direct impact on energy demand and global warming. The rainwater which replenished the ground aquifers are unable to match the water sucked by these pumps. About 114 million people living in Rajasthan, Punjab, and Harynaya including the capital city of Delhi are facing water shortage.
The likely alternative for these states is to desalinate the seawater from the west coast of India and pump them all the way to Delhi, which is thousands of kilometers from the coast. The increasing economic growth of India has increased the demand for power, often based on coal. Power industry is one of the largest users of water. Plants located on coastal are able to use seawater for their ‘once through’ cooling system and for boilers. But the plants located inland have to use only surface water like rivers. They cannot use ‘once through’ system, but use a closed circuit cooling systems where they have to store large pool of hard water.
It is a vicious cycle. Water shortage increase the demand for power and power shortage increases the demand for water. Desalination is the only alternative but it is a very energy intensive and a costly solution. Changing climate, global warming, deforestation, and water shortage are ominous signs of Nature’s fury against human greediness.
When countries like Australia set up their largest desalination facilities, the country experiences the heaviest rains in decades with flash flooding in many parts, making politicians wonder whether their water management decisions are right. Unfortunately Science cannot solve our greediness only human beings can learn lessons from Nature and take right decisions.