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
80
70
y = 5E-06x 2 - 0.3934x + 7098.8
R2 = 0.8959
60
Oil Price ($)
50
40
30
20
10
0
Oct-95
Mar-97
Jul-98
Dec-99
Apr-01
Sep-02
Price $/BBL
Jan-04
May-05
Oct-06
Feb-08
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 microenterprises 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
Limited heat transfer area
Open burning
High heat losses
No control on emissions
Variability of fuels
Low efficiency, high emissions
Air supply through fans/blowers
Well-designed heat transfer
Burning in closed space
Low heat losses
Emission control devices in place
Fuel standardized
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 UtilizationA simple pit or a complex biochemical reactor?
The importance and relevance of anaerobic
digestion technologies for India
Biogas from cattle dung
Biogas from poultry litter
Total bovine population (2003) :
272 million
Yearly dung production (@12
kg/day/animal) = 1191.3 million tons
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 : 19.34 mtoe (387
mtoe total for India)
Yearly gas production (@30 lit/kg) :
35739 million m3 /annum
•
•
Resource too large to ignore
Can give benefits of clean energy generation, bio-fertilizer
production and sanitation simultaneouly
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
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.
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)
Case 3: Small Scale Decentralized PowerA 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 kWe briquetting gasification
system at Dhanawas (19891993)
Electricity from agroresidues
 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!