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Showing posts with label Biomass. Show all posts
Showing posts with label Biomass. Show all posts

Saturday, September 4, 2021

What future holds for energy and climate?

Energy industry is at a crossroad. It must now find a new direction to address the climate issue while to continue to supply energy to the world. The options are very clear. It can find new ways and means to genuinely address some of the mistakes of the past by inventing new methods to address the problem irrespective of the cost involved because time is not in our favour. Alternatively, one can redirect the issue using new terminologies and jargons and temporarily buy some time till finding an alternative and lasting solution to the problem. The first option will take time and cost more, and the second option may not take time and cost less. It seems most of the companies are choosing the second alternative. But how? Renewable energy is defined as “a source of energy that is available from the nature that can be constantly replenished”. This will guarantee the sustainability. But we are used to Carbon based fuels and technologies and therefore we also need a renewable Carbon that can substitute fossil fuels so that existing technologies for power and transportation can be used. Biomass is also derived from plants and animals like fossil fuels, but it is different in terms of time scale, and it can be replenished quickly unlike fossil fuels. It is basically made up of Carbon, Hydrogen and additionally oxygen, like fossil fuels such as coal, oil and gas but free from sulphur. Therefore, one can use the same technology such as combustion, gasification and pyrolysis etc and convert a biomass into energy, chemicals and fuels while claiming them as “renewables”. It will require oxy-combustion and gasification methods and unfortunately usage of pure Oxygen will be inevitable.Therefore, both Carbon as well as Hydrogen derived from biomass becomes “Green” and “renewable”. In addition "Green Hydrogen" using renewable energy sources such as solar and wind by water electrolysis will help decarbonisation by capturing and converting CO2 emissions into a Syngas. It requires a steep fall in the cost of renewable electricity to less than $20/Mwh and Carbon emission to be taxed at least @ $250/Mt to discourage fossil industry. Once we establish green and renewable Carbon and Hydrogen then it is only a matter of generating a syngas, combination of Hydrogen and Carbon monoxide with various ratios to synthesis various chemicals including bio crude oil that leads to refineries to produce petrol, diesel and aviation fuels. We will be back into the game but with different brand called “Green and renewable”; it is "an old wine in a new bottle" Everybody is happy and politicians can now heave a sigh of relief and feel comfortable. One can also use “blue hydrogen’ as a mix to green hydrogen and synthesis various downstream chemicals such as Ammonia, urea etc. Thus they can use them to decarbonise the fossil economy. In either way there is still an issue of CARBON EMISSION that needs to be addressed. They may claim biofuel as Carbon neutral, but it will not stop the increasing concentration of GHG into the atmosphere or climate change. Therefore Carbon tax will be inevitable. Bioenergy and renewable energy may increase the sustainability but will not address the issue of global warming and climate change. Nature does not discriminate between ‘bio-carbon’ and ‘fossil carbon’. Only “Carbon Recycling Technology” can address the problem of global warming and climate change. The simplest method will be to to collect CO2 emission from all petrol and diesel engines in a liquid form using a retrofittable device in the vehicle and convert them in a centralised facility to Syngas using renewable Hydrogen .The syngas can be converted into renewable crude using F-T reaction hat can be processed in a refinery for recycling into petrol, diesel and aviation fuel so that we can eliminate technologies such as large batteries and Fuel cells. By this way we can ensure the CO2 level in the atmosphere is stabilised and existing infrastructures are utilised. The availability of biomass for a radical change will be an issue especially in Asia where growing population requires more land for agriculture and deforestation is a common problem. Perhaps we need completely a new electricity generation technology that can "drive electrons to flow in a super conductor" and a magnetic storage using a cryogenic fluid. Unfortunately not many researchers are working in this direction.

Wednesday, July 11, 2012

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.