Decentralized Energy Technologies for Micro-level Sustainability: Some Issues and Challenges V.V.N.Kishore Professor & Head, Dept. of Energy and Environment TERI University

The Three Major Energy Concerns of the Millennium Climate change concerns due to unprecedented energy use Rapid depletion of conventional energy sources Providing clean and affordable energy to two billion people without adequate access

Evolution of average per capita energy consumption

Global carbon cycle and anthropogenic fluxes

The Keeling curve, a long term record of carbon dioxide

Spectral range of outgoing thermal radiation

Price of crude oil and the OPEC oil shock

Trend of oil prices since 1995

Widening gap in energy consumption between rich and poor

Some energy access issues at the national level About 100 million households (600 million people) do not have access to clean cooking energy About 50% of all households do not use electricity About 23% of all households do not have toilets A large number of small and micro- enterprises use biomass energy

A Basic Engineering Challenge Can a small energy conversion device have the same performance as a large one with reference to 1.Conversion efficiency 2.Emissions 3.Cost

A special challenge for small bio energy technologies How can one deal with the large variability of biomass materials while designing high performance conversion devices?

Case 1: The Chulha vs Boiler Biomass burning Chulha Coal fired boiler No control of air Air supply through fans/blowers Limited heat transfer area Well-designed heat transfer Open burning Burning in closed space High heat losses Low heat losses No control on emissions Emission control devices in place Variability of fuels Fuel standardized Low efficiency, high emissions High efficiency, low emissions

The Improved Chulha Riddle Can a reasonable fuel savings (50-60%) be achieved with open ports and without mechanical air control for all kinds of biomass materials, variable sizes of vessels and all types of food cooked?

Some past efforts to control air supply and to increase heat transfer area

Some promising options: The turbo stove (TERI)

Some promising options (contd.) The BP stove The Approvecho stoveThe Philips stove

Case 2: The Biogas Plant for Waste Utilization- A simple pit or a complex biochemical reactor?

The importance and relevance of anaerobic digestion technologies for India Resource too large to ignore Can give benefits of clean energy generation, bio-fertilizer production and sanitation simultaneouly Biogas from cattle dung Total bovine population (2003) : 272 million Yearly dung production kg/day/animal) = million tons Yearly gas production lit/kg) : million m3 /annum Biogas from poultry litter Total poultry population (1997) : 347 million Yearly dung production 200 g/bird) : 25 million tons Yearly gas production 116 l/kg) : 2938 million m3/ annum Total gas production : mtoe (387 mtoe total for India)

Problems/limitations of small digesters Low conversion efficiency of available carbon into methane High hydraulic retention times, hence large digesters No temperature control, hence fluctuations in gas production Improper mixing, leading to unfavourable residence time distribution Inability of most designs to accept any biomass other than cattle dung Scum formation Requirement of large quantities of water Non-standard equipment for gas utilization (hydrogen sulfide removal, gas burners, gas engines)

Past attempts to improve performance of small digesters Use of solar energy for heating the digester RTD studies, use of a diffuser to improve RTD Install a simple mixer for scum breaking and better RTD Instal scum-breaking nets Develop a device for constant pressure gas supply to the burner (for fixed dome designs)

Some promising options for small scale anaerobic digestion of solid wastes Plug flow degester developed by Dr. H N Chanakya at I I Sc

Acidification 6 reactors for conversion into volatile fatty acids HRT of 6 days Digested waste is a very good manure Methanation High rate methanation reactor- UASB HRT-16 h and COD reduction- 90% Treatment of high strength leachate to produce biogas (70-75% CH 4 ) Some promising options for small scale anaerobic digestion of solid wastes (contd) TEAM Process of TERI A Biphasic process for digestion of leafy waste, food waste etc.

Case 3: Small Scale Decentralized Power- A small amount of electricity makes a big difference A CFL of 10 W improves the quality of life in households Small power for lighting/TV/mobile charging etc. has several social benefits such as education, connectivity, productivity improvement etc. A small fan (5 W) in the turbo stove results in a quantum jump in efficiency Incorporation of a few pumps is crucial for the high rate digestion in the TEAM process Addition of a small blower (~.5 HP) makes the gasification process possible Several small enterprises listed under KVIC can actually improve their performance by using a small amount of electricity (e.g. Soap making)

Technology options for DG Photovoltaic systems (Technology well developed, high initial cost, maintenance costs due to battery) Small hydro power (Technology well developed, site specific) Biomass gasification (Technology reasonably mature, but gaps exist; impurities in gas, small gas engines not standardized. Low initial cost but supply chain for biomass and services still informal) Biomethanation (Several possibilities for technology improvements, small scale systems for impurity removal and power generation not yet standardized. Supply chain problems similar to gasification. Otherwise a very promising and appropriate solution) Bio- diesel (A few pilots exist, uncertainties regarding oil yield etc.)

7 kW e briquetting gasification system at Dhanawas ( ) Electricity from agro- residues Useful for village electrification Can be scaled-up for captive power generation Useful for irrigation pumping

Biomass gasifier system (10-20 kWe) capacity

Village electrification – Gasifier at Village Jemara, Chhattisgarh

Will be very happy if some of you apply your knowledge and minds to any of the problems mentioned in this lecture. Thank you!