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Wednesday, April 5, 2023
How desalination plants contribute to global warming and solutions to address them? I posted the following article in my blog www.clean-energy-water-tech.com in 2014. We are now addressing this problem by setting one the largest integrated membrane-based sea water desalination plants in India using renewable power without using oil and gas. Highly contaminated and concentrated effluent discharge from existing and operating desalination plants around the world have greatly contributed to global warming according to world’s leading research institutions in marine science and oceanography. https://www.clean-energy-water-tech.com/2014/02/desalination-plants-contribute-to.html The ocean’s circulation which acts as conveyor belt distributes the increasing salinity and temperature of the sea across the globe. Several companies are researching on solutions to address the above problem and to achieve a Zero Liquid Discharge (ZLD) concept. Concepts such as FO (forward osmosis), OARO (osmosis assisted RO), NF pre-treatment with EDR, recovery of minerals such as Potassium chloride, Magnesium chloride (a precursor for extraction of Magnesium metal), Lithium chloride, Bromine etc. Theoretically all these solutions are encouraging but when to come to practise there are several hurdles to get over. Currently the most popular SWRO process is to recover 40% fresh water from seawater and discharge the balance 60% with twice its salinity and contaminated chemical are discharged in the sea. Such practice is going on since sixties when RO membranes were introduced. SWRO is an energy intensive process along with thermal evaporation they contribute to a great amount of green house gases. Despite several improvements in energy conservation in membrane processes the emissions of GHG was never addressed till date. Meanwhile several large-scale desalination plants are planned and implemented to overcome severe shortage of fresh water especially in African countries and pacific island and many arid regions of the world. We in CEWT are introducing CAPZ (clean water at affordable price with zero discharge) desalination a proprietary technology that not only achieve the highest recovery of fresh water from sea water but also generates simultaneously a highly value added ultrapure saturated Sodium chloride brine that serves as feed stock for chloralkaline industries substituting ‘solar evaporated salt’ as a source of Sodium. The pure saturated Sodium chloride brine is the feedstock to produce Caustic soda using membrane electrolysis as well as to produce Soda ash using Solvay process. Modern chloralkaline plants are very large in scales of operation which requires large quantities of solar salts. Due to climate change and unseasonal monsoon rains that have severely affected the solar salt production world-wide leaving a large gap between demand and supply. It has sharply increased the price of solar salt in the international market. Bulk of the solar salt is also used in ‘de-icing’ road due to severe snow in the industrialised countries. CAPZ desalination can recover up to 72% fresh water as well as 4.70% saturated sodium chloride brine simultaneously. Directly from seawater. Our current proposed plant in India will produce about 10,000 Mt of saturated Sodium chloride brine per day or 3150 Mt/day of high-quality salt along with 80,000 m3/day of fresh water from a seawater intake of 182,000 m3/day achieving zero liquid discharge (ZLD). We can also retrofit OARO system in our process to further increase water and salt production making it the most effective and economical and environmentally desalination technology in the world!
Wednesday, November 6, 2019
Global warming and climate change are the topics of the day and doomsday predictions are abounding. In a divided world of differing ideologies and dogmas, emotions play a major role and all conclusions are drawn out of such emotions. Emotional intelligence is the key and in-depth analysis will clear the clouds of doubts and disbeliefs and not just raw emotions.
When quantum science emerged as a mainstream science substituting classical science the world changed dramatically often leading to spirituality or eastern philosophy of ancient India. When Albert Einstein said, “I hope the moon is still there when I am not looking at it”, it had huge implications and a few decades later quantum science confirmed that Einstein was wrong. In other words, it is the conscience that creates the reality. With this is the reality of science one may wonder whether “reality” has anything to do with “science” at all. Albert Einstein in his own words said, “As far as the laws of mathematics refer to reality, they are not certain; as far as they are certain they do not refer to reality”.
Let us examine about the science of global warming due to man-made GHG emissions resulting in climate change. Electricity was a new form of energy discovered in eighteenth century and it became part of human civilization ever since. But it was already existed in nature in the form of lightning, but we were unable to recognize it or reproduce it in the scale that can be useful to us. Then the question is whether electricity was discovered by human beings at all and if so, can we reproduce “lightning?” and use this electricity without emitting any carbon emission at all. The answer is no, at least for now due lack of technology to predict lightning, tapping it economically and storing it for distribution. Theoretically lightning alone can supply all the electricity world needs but practically it is almost impossible to utilize it for the above reasons. When electromagnetism and electricity were discovered they did not relate it to “lightning” but claimed as a separate discovery between the relationship between magnetic and electric charges which resulted in generating electricity. Then later we were able to explain “lightning” due to positive and negative charges between the cold clouds and rising hot air with water.
Science is nothing but explaining nature with theoretical concepts and physical demonstrations. That is why yoga sutra describes the world as a phenomenal world and it is an irreducible experimental substance. That is the peculiarity of science because it is the human conscience that creates this scientific reality. I too conclude that “as far as law of science of climate change refers to reality, they are not certain; as far as they are certain they do not refer to reality.” Similarly, science has nothing to do with economics and but we human beings made economics as a measure of one’s life and his or her success. This is the fundamental flaw in human thinking. One can conclude that all man-made theories and practices are fundamentally flawed which is evident from the world of turmoil we are witnessing and living in. We failed to ask emotionally intelligent questions by endless pursuit of happiness through money and materials in the name of science.
As I mentioned in my previous article we developed generating electricity from thermal source and we ended up digging fossil fuels at enormous cost and added further value by combustion with air generating huge amount of CO2.But we never estimated the cost of CO2 at that time and we never realized the future impact of such a CO2 emissions from fossil fuels till now. Even now we do not want to put a price for CO2 emissions and continue to emit by simply denying the fact that such unabated emissions will have consequences. We conveniently use science and economics when it suits us, otherwise we reject them outright when it does not suit us. All climate change denials come from the fear of economic collapse unconsciously.
Therefore, the first step in achieving zero carbon emission is to eliminate fossil fuels completely or impose penalty to discourage emissions if we accept global warming and climate change as the reality. Without taking this first step we cannot move forward.
Now there is a new awakening that Hydrogen will substitute fossil fuels with zero emissions. This is again a mistake. Imaging all cars and power plants using hydrogen and fuel cell and emit (only) water vapour into the atmosphere. I am sure that will drastically change our climate in a very short span of time. The atmospheric moisture will dramatically increase trapping enormous amount of heat and precipitation. The consequences will be dire. Every kg of Hydrogen will require 9 kgs of water. Renewable Hydrogen is a precious commodity and it can be used only to decarbonize the fossil economy and cannot be used a fuel directly. Such an attempt will be a failure.
Alternatively, we can continue to use fossil fuel as usual but eliminate CO2 emission by simply recycling in the form of RNG (renewable natural gas) using renewable hydrogen. This may look as an expensive proposal at the first instance, but it will become a norm in the long run and we human beings have a capacity to adopt to this new reality. It is now possible to capture CO2 economically and substantially while generating power using direct Carbon fuel cell with highest electrical efficiency. It can be easily recycled in the form of RNG. Why Governments don’t act?
In the absence of above alternative, we may have to face the consequences of climate change due to man-made emissions and simply be content with an American slogan, “In God we trust”.
2. DCFC by Fuelcell energy and Exxon.
Sunday, November 5, 2017
Friday, November 14, 2014
Tuesday, January 15, 2013
It is a fact that solar energy is emerging as a key source of future energy as the climate change debate is raging all over the world. The solar radiation can meet world’s energy requirement completely in a benign way and offer a clear alternative to fossil fuels. However the solar technology is still in a growing state with new technologies and solutions emerging. Though PV solar is a proven technology the levelised cost from such plants is still much higher than fossil fuel powered plants. This is because the initial investment of a PV solar plant is much higher compared to fossil fuel based power plants. For example the cost of a gas based power plant can be set up at less than $1000/Kw while the cost of PV solar is still around $ 7000 and above. However solar thermal is emerging as an alternative to PV solar. The basic difference between these two technologies is PV solar converts light energy of the sun directly into electricity and stores in a battery for future usage; solar thermal plants use reflectors (collectors) to focus the solar light to heat a thermic fluid or molten salt to a high temperature. The high temperature thermic fluid or molten salt is used to generate steam to run a steam turbine using Rankine cycle or heat a compressed air to run a gas turbine using Brayton cycle to generate electricity. Solar towers using heliostat and mirrors are predicted to offer the lowest cost of solar energy in the near future as the cost of Heliostats are reduced and molten salts with highest eutectic points are developed. The high eutectic point molten salts are likely to transform a range of industries for high temperature applications. When solar thermal plants with molten salt storage can approach temperature of 800C, many fossil fuel applications can be substituted with solar energy. For example, it is expected by using solar thermal energy 24x7 in Sulfur-Iodine cycle, Hydrogen can be generated on a large commercial scale at a cost @2.90/Kg.Research and developments are focused to achieve the above and it may soon become a commercial reality in the near future. “The innovative aspect of CSP (concentrated solar power) is that it captures and concentrates the sun’s energy to provide the heat required to generate electricity, rather than using fossil fuels or nuclear reactions. Another attribute of CSP plants is that they can be equipped with a heat storage system in order to generate electricity even when the sky is cloudy or after sunset. This significantly increases the CSP capacity factor compared with solar photovoltaics and, more importantly, enables the production of dispatchable electricity, which can facilitate both grid integration and economic competitiveness. CSP technologies therefore benefit from advances in solar concentrator and thermal storage technologies, while other components of the CSP plants are based on rather mature technologies and cannot expect to see rapid cost reductions. CSP technologies are not currently widely deployed. A total of 354 MW of capacity was installed between 1985 and 1991 in California and has been operating commercially since then. After a hiatus in interest between 1990 and 2000, interest in CSP has been growing over the past ten years. A number of new plants have been brought on line since 2006 (Muller- Steinhagen, 2011) as a result of declining investment costs and LCOE, as well as new support policies. Spain is now the largest producer of CSP electricity and there are several very large CSP plants planned or under construction in the United States and North Africa. CSP plants can be broken down into two groups, based on whether the solar collectors concentrate the sun rays along a focal line or on a single focal point (with much higher concentration factors). Line-focusing systems include parabolic trough and linear Fresnel plants and have single-axis tracking systems. Point-focusing systems include solar dish systems and solar tower plants and include two-axis tracking systems to concentrate the power of the sun. Parabolic trough collector technology: The parabolic trough collectors (PTC) consist of solar collectors (mirrors), heat receivers and support structures. The parabolic-shaped mirrors are constructed by forming a sheet of reflective material into a parabolic shape that concentrates incoming sunlight onto a central receiver tube at the focal line of the collector. The arrays of mirrors can be 100 meters (m) long or more, with the curved aperture of 5 m to 6 m. A single-axis tracking mechanism is used to orient both solar collectors and heat receivers toward the sun (A.T. Kearney and ESTELA, 2010). PTC are usually aligned North-South and track the sun as it moves from East to West to maximize the collection of energy. The receiver comprises the absorber tube (usually metal) inside an evacuated glass envelope. The absorber tube is generally a coated stainless steel tube, with a spectrally selective coating that absorbs the solar (short wave) irradiation well, but emits very little infrared (long wave) radiation. This helps to reduce heat loss. Evacuated glass tubes are used because they help to reduce heat losses. A heat transfer fluid (HTF) is circulated through the absorber tubes to collect the solar energy and transfer it to the steam generator or to the heat storage system, if any. Most existing parabolic troughs use synthetic oils as the heat transfer fluid, which are stable up to 400°C. New plants under demonstration use molten salt at 540°C either for heat transfer and/or as the thermal storage medium. High temperature molten salt may considerably improve the thermal storage performance. At the end of 2010, around 1 220 MW of installed CSP capacity used the parabolic trough technology and accounted for virtually all of today’s installed CSP capacity. As a result, parabolic troughs are the CSP technology with the most commercial operating experience (Turchi, et al., 2010). Linear Fresnel collector technology: Linear Fresnel collectors (LFCs) are similar to parabolic trough collectors, but use a series of long flat, or slightly curved, mirrors placed at different angles to concentrate the sunlight on either side of a fixed receiver (located several meters above the primary mirror field). Each line of mirrors is equipped with a single-axis tracking system and is optimized individually to ensure that sunlight is always concentrated on the fixed receiver. The receiver consists of a long, selectively-coated absorber tube. Unlike parabolic trough collectors, the focal line of Fresnel collectors is distorted by astigmatism. This requires a mirror above the tube (a secondary reflector) to refocus the rays missing the tube, or several parallel tubes forming a multi-tube receiver that is wide enough to capture most of the focused sunlight without a secondary reflector. The main advantages of linear Fresnel CSP systems compared to parabolic trough systems are that: LFCs can use cheaper flat glass mirrors, which are a standard mass-produced commodity; LFCs require less steel and concrete, as the metal support structure is lighter. This also makes the assembly process easier. »»The wind loads on LFCs are smaller, resulting in better structural stability, reduced optical losses and less mirror-glass breakage; and. »»The mirror surface per receiver is higher in LFCs than in PTCs, which is important, given that the receiver is the most expensive component in both PTC and in LFCs. These advantages need to be balanced against the fact that the optical efficiency of LFC solar fields (referring to direct solar irradiation on the cumulated mirror aperture) is lower than that of PTC solar fields due to the geometric properties of LFCs. The problem is that the receiver is fixed and in the morning and afternoon cosine losses are high compared to PTC. Despite these drawbacks, the relative simplicity of the LFC system means that it may be cheaper to manufacture and install than PTC CSP plants. However, it remains to be seen if costs per kWh are lower. Additionally, given that LFCs are generally proposed to use direct steam generation, adding thermal energy storage is likely to be more expensive. Solar to Electricity technology: Solar tower technologies use a ground-based field of mirrors to focus direct solar irradiation onto a receiver mounted high on a central tower where the light is captured and converted into heat. The heat drives a thermo-dynamic cycle, in most cases a water-steam cycle, to generate electric power. The solar field consists of a large number of computer-controlled mirrors, called heliostats that track the sun individually in two axes. These mirrors reflect the sunlight onto the central receiver where a fluid is heated up. Solar towers can achieve higher temperatures than parabolic trough and linear Fresnel systems; because more sunlight can be concentrated on a single receiver and the heat losses at that point can be minimized. Current solar towers use water/steam, air or molten salt to transport the heat to the heat-exchanger/steam turbine system. Depending on the receiver design and the working fluid, the upper working temperatures can range from 250°C to perhaps as high 1 000°C for future plants, although temperatures of around 600°C will be the norm with current molten salt designs. The typical size of today’s solar power plants ranges from 10 MW to 50 MW (Emerging Energy Research, 2010). The solar field size required increases with annual electricity generation desired, which leads to a greater distance between the receiver and the outer mirrors of the solar field. This results in increasing optical losses due to atmospheric absorption, unavoidable angular mirror deviation due to imperfections in the mirrors and slight errors in mirror tracking. Solar towers can use synthetic oils or molten salt as the heat transfer fluid and the storage medium for the thermal energy storage. Synthetic oils limit the operating temperature to around 390°C, limiting the efficiency of the steam cycle. Molten salt raises the potential operating temperature to between 550 and 650°C, enough to allow higher efficiency supercritical steam cycles although the higher investment costs for these steam turbines may be a constraint. An alternative is direct steam generation (DSG), which eliminates the need and cost of heat transfer fluids, but this is at an early stage of development and storage concepts for use with DSG still need to be demonstrated and perfected. Solar towers have a number of potential advantages, which mean that they could soon become the preferred CSP technology. The main advantages are that: »»The higher temperatures can potentially allow greater efficiency of the steam cycle and reduce water consumption for cooling the condenser; »»The higher temperature also makes the use of thermal energy storage more attractive in order to achieve schedulable power generation; and »»Higher temperatures will also allow greater temperature differentials in the storage system, reducing costs or allowing greater storage for the same cost. The key advantage is the opportunity to use thermal energy storage to raise capacity factors and allow a flexible generation strategy to maximize the value of the electricity generated, as well as to achieve higher efficiency levels. Given this advantage and others, if costs can be reduced and operating experience gained, solar towers could potentially achieve significant market share in the future, despite PTC systems having dominated the market to date. Solar tower technology is still under demonstration, with 50 MW scale plant in operation, but could in the long-run provide cheaper electricity than trough and dish systems (CSP Today, 2008). However, the lack of commercial experience means that this is by no means certain and deploying solar towers today includes significant technical and financial risks. Sterling dish technology: The Stirling dish system consists of a parabolic dish shaped concentrator (like a satellite dish) that reflects direct solar irradiation onto a receiver at the focal point of the dish. The receiver may be a Stirling engine (dish/ engine systems) or a micro-turbine. Stirling dish systems require the sun to be tracked in two axes, but the high energy concentration onto a single point can yield very high temperatures. Stirling dish systems are yet to be deployed at any scale. Most research is currently focused on using a Stirling engine in combination with a generator unit, located at the focal point of the dish, to transform the thermal power to electricity. There are currently two types of Stirling engines: Kinematic and free piston. Kinematic engines work with hydrogen as a working fluid and have higher efficiencies than free piston engines. Free piston engines work with helium and do not produce friction during operation, which enables a reduction in required maintenance. The main advantages of Stirling dish CSP technologies are that: »»The location of the generator - typically, in the receiver of each dish - helps reduce heat losses and means that the individual dish-generating capacity is small, extremely modular (typical sizes range from 5 to 50 kW) and are suitable for distributed generation; »»Stirling dish technologies are capable of achieving the highest efficiency of all type of CSP systems »»Stirling dishes use dry cooling and do not need large cooling systems or cooling towers, allowing CSP to provide electricity in water-constrained regions; and »»Stirling dishes, given their small foot print and the fact they are self-contained, can be placed on slopes or uneven terrain, unlike PTC, LFC and solar towers. These advantages mean that Stirling dish technologies could meet an economically valuable niche in many regions, even though the levelised cost of electricity is likely to be higher than other CSP technologies. Apart from costs, another challenge is that dish systems cannot easily use storage. Stirling dish systems are still at the demonstration stage and the cost of mass-produced systems remains unclear. With their high degree of scalability and small size, stirling dish systems will be an alternative to solar photovoltaics in arid regions.” (Source : IRENA 2012)