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

y = 5E-06x2 - 0.3934x + 7098.8R2 = 0.8959

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Oct-95 Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04 May-05 Oct-06 Feb-08

Oil

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Price $/BBL

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 boilerNo 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 stove The 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 (@12 kg/day/animal) = 1191.3 million tons Yearly gas production (@30 lit/kg) : 35739 million m3 /annum 

Biogas from poultry litter Total poultry population (1997) : 347 millionYearly dung production (@ 200 g/bird) : 25 million tonsYearly gas production (@ 116 l/kg) : 2938 million m3/ annumTotal gas production : 19.34 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% CH4)

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 kW7 kWee briquetting gasification briquetting gasification system at Dhanawas (1989-system at Dhanawas (1989-

1993)1993)

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 electrification – Gasifier at Village Jemara, ChhattisgarhVillage 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!