Renewable technologies are considered as clean sources of energy and optimal use of these resources minimize environmental impacts, produce minimum secondary wastes and are sustainable based on current and future economic and social societal needs. Sun is the source of all energies. The primary forms of solar energy are heat and light. Sunlight and heat are transformed and absorbed by the environment in a multitude of ways. Some of these transformations result in renewable energy flows such as biomass and wind energy. Renewable energy technologies provide an excellent opportunity for mitigation of greenhouse gas emission and reducing global warming through substituting conventional energy sources. In this article a review has been done on scope of CO2 mitigation through solar cooker, water heater, dryer, biofuel, improved cookstoves and by hydrogen.

https://www.beren.sakarya.edu.tr/sites/beren.sakarya.edu.tr/file/1380752545-07-RenewEn.pdf.pdf

Role of renewable energy sources in environmental protection: A review

There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient conversion method compared to other thermo-chemical conversion technologies. However, this technology is not yet fully developed with respect to its commercial applications. In this study, more than two hundred publications are reviewed, discussed and summarized, with the emphasis being placed on the current status of pyrolysis technology and its potential for commercial applications for bio-fuel production. Aspects of pyrolysis technology such as pyrolysis principles, biomass sources and characteristics, types of pyrolysis, pyrolysis reactor design, pyrolysis products and their characteristics and economics of bio-fuel production are presented. It is found from this study that conversion of biomass to bio-fuel has to overcome challenges such as understanding the trade-off between the size of the pyrolysis plant and feedstock, improvement of the reliability of pyrolysis reactors and processes to become viable for commercial applications. Further study is required to achieve a better understanding of the economics of biomass pyrolysis for bio-fuel production, as well as resolving issues related to the capabilities of this technology in practical application.

https://cyberleninka.org/article/n/1011788.pdf

Biofuels production through biomass pyrolysis - a technological review.

The main purpose of this review is to update the information on gasification tar, the most cumbersome and problematic parameter in any gasification commercialization effort. The work aims to present to the community the scientific and practical aspects of tar formation and conversion (removal) during gasification as a function of the various technological and technical parameters and variables.

/pdf/biomass-gasifier-tars-their-nature-formation-and-conversion-1uli6zy3re.pdf

Biomass Gasifier "Tars": Their Nature, Formation, and Conversion

Plasma assisted combustion: Dynamics and chemistry

http://oa.upm.es/927/1/Acta_Astronautica(1007-1039).pdf

The asymptotic structure of counterflow diffusion flames for large activation energies

This paper uncovers some of the misconceptions associated with the usage of producer gas, a lower calorific gas as a reciprocating engine fuel This paper particularly addresses the use of producer gas in reciprocating engines at high compression ratio (17 : 1), which hitherto had been restricted to lower compression ratio (up to 12 : 1) This restriction in compression ratio has been mainly attributed to the auto-ignition tendency of the fuel, which appears to be simply a matter of presumption rather than fact The current work clearly indicates the breakdown of this compression ratio barrier and it is shown that the engine runs smoothly at compression ratio of 17 : 1 without any tendency of auto-ignition Experiments have been conducted on multi-cylinder spark ignition engine modified from a production diesel engine at varying compression ratios from 115 : 1 to 17 : 1 by retaining the combustion chamber design As expected, working at a higher compression ratio turned out to be more efficient and also yielded higher brake power A maximum brake power of 175 kWe was obtained at an overall efficiency of 21% at the highest compression ratio The maximum de-rating of power in gas mode was 16% as compared to the normal diesel mode of operation at comparable compression ratio, whereas, the overall efficiency declined by 325% A careful analysis of energy balance revealed excess energy loss to the coolant due to the existing combustion chamber design Addressing the combustion chamber design for producer gas fuel should form a part of future work in improving the overall efficiency

Biomass derived producer gas as a reciprocating engine fuel—an experimental analysis

The paper addresses a distributed power generation system that has evolved at the Indian Institute of Science, Bangalore. The technological and field-related experience pertaining to open top re-burn down draft biomass gasification system coupled with the internal combustion engine or thermal device are brought out. The gasifier reactor design uses dual air entry – air nozzles and open top to help in establishing a thick high temperature zone to remove the contaminants in the product gas; a gas clean-up system to further refine the gas to ultra-pure quality. These elements are integrated with other sub-systems, namely feedstock preparation, ash handling, water treatment, process automation and other accessories to form an Independent Power Producer.Based on this technology there are over 30 units operating in India and abroad, with an accumulated capacity of over 20 MW. Over 80,000 h of operation of these systems have resulted in a saving of about 350 tons of fossil fuel, implying a saving of about 1120 tons of $CO_{2}$ – a promising candidate for Clean Development Mechanisms (CDMs),other than reduction in toxic gases like $NO_{x} and SO_{x}$.

/pdf/biomass-gasification-technology-a-route-to-meet-energy-needs-21y98fdzah.pdf

Biomass gasification technology - a route to meet energy needs

This paper presents computational and experimental results on a new burner configuration with a mild combustion concept with heat release rates up to 10 MW/m(3). The burner configuration is shown to achieve mild combustion by using air at ambient temperature at high recirculation rates (similar to250%-290%) both experimentally and computationally. The principal features of the configuration are: (1) a burner with forward exit for exhaust gases; (2) injection of gaseous fuel and air as multiple, alternate, peripheral highspeed jets at the bottom at ambient temperature, thus creating high enough recirculation rates of the hot combustion products into fresh incoming reactants; and (3) use of a suitable geometric artifice-a frustum of a cone to help recirculation. The computational studies have been used to reveal the details of the flow and to optimize the combustor geometry based on recirculation rates. Measures, involving root mean square temperature fluctuations, distribution of temperature and oxidizer concentration inside the proposed burner, and a classical turbulent diffusion jet flame, are used to distinguish between them quantitatively. The system, operated at heat release rates of 2 to 10 MW/m(3) (compared to 0.02 to 0.32 MW/m(3) in the earlier studies), shows a 10-15 dB reduction in noise in the mild combustion mode compared to a simple open-top burner and exhaust NOx emission below 10 ppm for a 3 kW burner with 10% excess air. The peak temperature is measured around 1750 K, approximately 300 K lower than the peak temperature in a conventional burner.

/pdf/studies-on-a-new-high-intensity-low-emission-burner-4um9m7jge4.pdf

Studies on a new high-intensity low-emission burner

This paper summarizes the findings involved in the development of producer gas fuelled reciprocating engines over a time frame of six years. The high octane rating, ultra clean and low energy density producer gas derived from biomass has been examined. Development efforts are aimed at a fundamental level, wherein the parametric effects of compression ratio and ignition timing on the power output are studied. These findings are subsequently applied in the adaptation of commercially available gas engines at two different power levels and make. Design of a producer gas carburetor also formed a part of this developmental activity. The successful operations with producer gas fuel has opened possibilities for adapting commercially available gas engine for large scale power generation application, albeit loss of power to an extent of 20-30%. This loss in power is compensated to a much larger proportion by the way of reduction in toxic emissions; these technologies generate fewer amounts of toxic gases (low $NO_x$ and almost zero $SO_x$) and zero towards GHG.

/pdf/development-of-producer-gas-engines-b3j3hhk9sj.pdf

Development of producer gas engines

The paper addresses case studies of a low temperature and a high temperature industrial heat requirement being met using biomass gasification. The gasification system for these applications consists of an open top down draft reburn reactor lined with ceramic. Necessary cooling and cleaning systems are incorporated in the package to meet the end use requirements. The other elements included are the fuel conveyor, water treatment plant for recirculating the cooling water and adequate automation to start, shut down and control the operations of the gasifier system. Drying of marigold flower, a low temperature application is considered to replace diesel fuel in the range of $125-150 1\hspace{2mm} h^{-1}$. Gas from the $500 kg\hspace{2mm} h^{-1}$, gasifier system is piped into the producer gas burners fixed in the combustion chamber with the downstream process similar to the diesel burner. The high temperature application is for a heat treatment furnace in the temperature range of 873–1200 K. A $300 kg \hspace{2mm}h^{-1}$ of biomass gasifier replaces 2000 1 of diesel or LDO per day completely. The novelty of this package is the use of one gasifier to energize 16 burners in the 8 furnaces with different temperature requirements. The system operates over 140 h per week on a nearly nonstop mode and over 4000 h of operation replacing fossil fuel completely. The advantage of bioenergy package towards the economic and environmental considerations is presented.

H. S. Mukunda

Papers

Biomass derived producer gas as a reciprocating engine fuel—an experimental analysis

Biomass gasification technology - a route to meet energy needs

Studies on a new high-intensity low-emission burner

Development of producer gas engines

Biomass gasification—a substitute to fossil fuel for heat application