COGENERATION AND DISTRIBUTED RESOURCES

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COGENERATION AND DISTRIBUTED RESOURCES

• Professor Akhtar Kalam
• Victoria University

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A secure supply of power and heat is of
paramount importance, and it must be provided at
the lowest possible cost.



The privatisation of the
electricity supply industry has brought
competition in to the market place for
electricity supply and buyers.
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EcoGeneration in Australia

• Based on industry growth trends and current
  government initiatives, by 2010 EcoGeneration
  should almost double to represent approximately
  14 per cent (7000 MW) of total installed
  generation capacity in Australia compared to 7.8
  per cent (3390 MW) at the end of 1999 (AEAs
  estimate). Of this total, renewables should
  quadruple form 530 MW to approximately 2100 MW by
  2010. Non-renewable EcoGeneration should
  increase by some 70 per cent to approximately
  4900 MW. These growth rates reflect
  international trends where ecologically
  sustainable power production technologies are
  recording by far the highest growth rates.

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EcoGeneration EcoGeneration includes
cogeneration, renewables, waste-to-energy and
distributed generation technologies.
EcoGeneration is a natural grouping of
environmentally sustainable energy delivery
technologies as they offer similar benefits and
face similar challenges in the National
Electricity Market.
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Cogeneration (also known as combined heat
and power - CHP) Cogeneration involves the
production of combined heat and power. Heat that
would otherwise be wasted is recovered and used
in commercial and industrial applications.
Cogeneration is typically two to three times more
efficient than major conventional, coal-fired,
centralised power stations. On average it
produces one-third the greenhouse gas emissions
of conventional power production.
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Renewable generation Renewable generated power
produces no net greenhouse emissions. Includes
power generated from natural resources such as
biomass, hydro, wind, solar and tidal. It also
includes power generated using certain wastes.
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Waste-to-energy This is electricity produced
using waste fuels, some of which may otherwise
cause local environmental challenges. A number of
waste fuels are deemed to be renewable including
cane residue (bagasse) from the sugar industry
sludge gas from sewage treatment plants and
methane from landfill sites. Fossil fuel-based
waste streams include coal waste methane,
refinery waste gases and coal tailings.
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Distributed generation This is power generation
generally located close to where it is consumed,
for example, supplying electricity on-site or
over-the-fence. Also referred to as
decentralised, embedded or localised generation.
Can be as small as a 1 kWe solar photovoltaic
system, or even larger than a 450 MW industrial
on-site cogeneration system.
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Embedded generation This refers to
smaller-scale generators that are connected to
electricity distribution networks. This is in
contrast to large-scale coal-fired generators
that are connected to very high voltage
electricity transmission networks.
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THE TECHNOLOGY Cogeneration
- is essentially a philosophy. It describes the
use of technology, that combines the generation
of heat (Mechanical energy) and electricity
(Electrical energy) in a single unit in a way
that is more efficient than producing heat and
electricity separately in boiler plant and at the
power station.
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In other words, cogeneration is the energy
process whereby waste heat, produced during the
generation of electricity, is utilised for steam
raising or heating. This is no different than any
other power stations. The only difference being
that the waste heat from the electricity
generating plant is harnessed made used of
rather than being thrown away in the form of
Waste Heat.
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The mechanical energy can be used for any
mechanical application such as driving motors,
compressors, extruders, etc. The electrical
energy can be used to meet in-house demand and
any surplus sold back to the electricity grid.
The thermal energy can be converted to steam or
hot water for process application, or for drying
purposes.
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In brown coal and gas fired power stations, 28
to 35 of the energy in the fuel is converted to
electricity, the other 65 to 72 becomes heat
which must be disposed of. In cogeneration, both
the recovered heat and the electricity or
mechanical energy are used, so efficiency
increases to 70 to 82 depending on the prime
mover used. This utilisation is well over twice
that of a large conventional power station.
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• WASTE HEAT
• STEAM Hot Water
• (Industrial Process) (Space heating in a
  commercial building or district heating
  scheme)

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• CONVENTIONAL PLANT
• WASTE HEAT rejected to the environment
• Capturing this will result in ? of 90 to be
  achieved
• cf. 36 (Conventional plant)
• 52 (Combined Cycle Gas Turbine)

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The economics of cogeneration schemes are most
compelling for organisations with a high heat
requirement. Units range from as little as 20kW
to hundreds of MW and can be linked to public and
commercial buildings, industrial sites and
community heating schemes.
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Cogeneration has a very wide application in the
industrial and commercial sectors, and also in
public institutions. In the industrial sector
potential exists in manufacturing (petroleum,
chemical, food and beverage, textiles, paper,
iron and steel, motor vehicles, glass and clay),
mining and forestry.
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There are two obvious times to consider investing
in cogeneration first, when existing boiler
capacity needs to be replaced and second, when
new buildings are being planned. Hospitals, for
example are already being designed to include a
cogeneration system from inception.
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Once the economics have been worked out and the
investment has been made, financial savings
quickly offset the initial additional costs
incurred, giving a payback in as little as two or
three years. The life of a cogeneration system
can exceed fifteen years, so the savings accrue
long after the initial capital costs have been
recouped.
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Cogeneration cycles

• TOPPING
• BOTTOMING
• COMBINED-CYCLE

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In a topping-cycle system, fuel is burned to
generate electricity the thermal energy
exhausted from this process is then used either
in an industrial application or for space
heating.
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In a bottoming-cycle system, the waste heat is
recovered from an industrial process application
and used to generate electricity.
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Combined-cycle systems generally use a
topping-cycle gas turbine the exhaust gases are
then used in a bottoming-cycle steam turbine to
generate more electricity and process thermal
energy. Heat pumps may also be used with a
cogeneration system to upgrade low-temperature
heat for process use.
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Cogeneration plants vary widely in size and
packaged micro-cogen units in the size range 20kW
to 60kW are commercially available for suitable
office buildings, restaurants, hotels, etc. For
units below 800kW, diesel and gas engines are the
most common type of prime motor. From
approximately 800kW to 10MW, gas turbines or
large reciprocating engines can be used. Steam
cycles (steam turbines) can also be used
especially in coal, waste gas or biomass fired
cogeneration systems. For applications above
10MW, gas and steam turbines are generally used.
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THE MARKET
The recent privatisation of the
electricity supply industry (ESI), together with
a number of business and technical changes, have
provided new impetus to the development of
cogeneration. It is not these factors alone that
are providing renewed interest in cogeneration,
but their conjunction at this time. Taken
together, the factors provide a window of
opportunity for the exploitation of cogeneration.
The development of cogeneration has increased
since the restructure of the ESI, but there is
still a long way to go to catch on to the rest
of the world.
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HEAT AND POWER PRODUCTION - A BRIEF HISTORY
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• Cogeneration is not a new idea
• Old days ? Factories ? Had their own power
  stations ? Supplied their own Heat Power
• 1965 ? 66 of the electricity consumed in the UK
  paper industry was generated on-site from COGEN
  schemes
• 1990 ? 66 went down to 20
• Grid systems
  (CEGB) ? reliable supply real lower prices
• REASONS
• (acted against Cogeneration
• in the last 2 decades ? decline)
  Development in Boiler plants
• Relatively cheap oil

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The Situation Today

• Recent years ? Renaissance
• 1990 ? privatisation of ESI ? competition
• ? Gas used for generation ? ??
• Since 1989 ? 1500MWe of new COGEN capacity (U.K.)

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• ADVANTAGES
• Efficient way of converting primary fuel to
  useful energy
• Process Industries benefit viz. commercial
  Environmental sectors
• Targets have been set by Governments and this
  will depend on
• Future gas and electricity prices
• Development in electricity trading
• Environmental pressures

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The Future

• INDUSTRY TODAY
• Market Driven energy market
• Needs specific legislation
• COGEN CAN BECOME A DRIVING FORCE

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In total contrast to coal, gas can be moved
relatively easily and without impacting on the
environment. Therefore, the engineering case for
gas-fired cogeneration meeting local heat and
power needs is very strong. There might well be
seen a reversal of the trends of the last 60
years, with the use of the Grid declining and
heat and power production being combined close to
the point of need.
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WHY COGENERATION NOW?

• Regardless of the engineering case for
  cogeneration, it will not "take off" unless it is
  economically attractive. The two fundamental
  parameters that dominate commercial viability
  are-
• (a) primary fuel costs
• (b) the capital costs of cogeneration schemes.

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Fuel Prices

• Most cogeneration schemes currently being
  developed are fuelled by gas. Until comparatively
  recently the pricing policy, did not encourage
  the development of gas-fired electricity
  generation. It was argued that gas was a premium
  fuel, too valuable for this application. This
  view has now changed.

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Capital Cost

• Industrial cogeneration schemes in general
  utilise either reciprocating engines or, more
  commonly now for larger installations, gas
  turbines. Concentration here is on gas turbines
  because they are generally preferred for schemes
  of several megawatts. Gas turbine technology has
  been improving rapidly in recent years producing
  more efficient machines. The market is developing
  with more players offering a greater range of
  machines.

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The "Green" Ticket

• Cogeneration can genuinely be labelled a "Green"
  technology. The overall thermodynamic efficiency
  of cogeneration is very high. Further, when gas
  fired, no sulphur dioxide is produced and NOx can
  be effectively controlled either by steam
  injection or dry NOx control through the design
  of burners. Finally, the application of
  cogeneration reduces the production of CO2
  compared with the grid/boiler approach. Although
  it is difficult to put a value on "green"
  benefits in money terms, it can do no company any
  harm to be associated with environmentally
  friendly technology.

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Ageing Boiler Plant

• In the fifties and sixties falling electricity
  prices, in real terms, encouraged industry to
  import electricity and produce steam and hot
  water in conventional boiler plant. Significant
  amounts of low cost, efficient package boilers
  were installed in the 1960's. Much of this plant
  is now reaching the end of its useful life.

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Security of Supply

• Security of supply can be of paramount importance
  in industrial environments. An on-site
  cogeneration scheme can enhance the security of
  both heat and electricity supplies. In
  particular, it is possible to design the
  electrical connections to ensure continuity of
  supply for the complete failure of the Grid. Such
  arrangements can prove most beneficial from both
  commercial and, in certain situations, safety
  viewpoints.

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Cogeneration in Australia

• VICTORIA (SECV) State Government INCENTIVE
  PACKAGE - 1987
• SOUTH AUSTRALIA (SAGASCO) Established a COGEN
  division
• At the end of 1999, cogeneration and distribution
  generation represented 8.3 of installed capacity.

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Cogeneration data

• No authoritative information is available on the
  extent of non-utility cogeneration and power
  production.
• The best available estimate puts cogeneration
  capacity in Australia at about 2,200MW, made up
  of the following industries
• Alumina industry is the most significant
  industry, accounting for 23 of operational
  capacity, 38 of electricity generation and 36
  of thermal production

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WA is the greatest user of cogeneration by
State/Territory accounting for 35 of operational
capacity, 39 of electricity generation capacity
and 32 of thermal production
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Steam turbine projects accounted for 58 of
operational capacity by prime mover technology,
57 of electricity generation and 95 of thermal
production
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Natural gas projects accounted for 56 of
operational capacity by primary fuel, 66 of
electricity generation and 38 of thermal
production. Renewable generation capacity
accounted for 360.3MW of capacity, representing
16.4 of total generation capacity
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Non-Cogeneration State/Territory
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Non-Cogeneration Prime Mover Technology
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Non-Cogeneration Primary Fuel
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1999 7 Cogen projects totalling 234MW 10
non-Cogen, grid connected, distributed generation
project totalling 295MW were committed and under
construction. Renewable projects amounted to 13
of the overall total
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Victorian support

• Within five years, it is conservatively expected
  that about 500 MW of Victoria's power will be fed
  into the SEC grid from private and public
  cogeneration and renewable energy projects, the
  equivalent to the output from one Loy Yang power
  station unit.

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COGENERATION COMMERCIAL VIABILITY

• It would be irresponsible to give the impression
  that cogeneration offers a panacea to all energy
  problems. Commercially viable opportunities are
  still small in number. The main factors
  influencing commercial viability are dependant on
  site's heat to power ratio and equipment
  utilisation.

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GREENHOUSE EFFECT

• WORLD ENERGY CONSUMPTION ?
• 1945-90 ? ELECTRICITY CONSUMPTION IN Vic ? 25
  FOLD. SIMILAR TRENDS IN OTHER PLACES. NOT
  POSSIBLE TO SUSTAIN SUCH GROWTH
• ? CONSERVATION REQUIRED

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GREENHOUSE EFFEST IS A SERIOUS PROBLEM

• AUSTRALIA ? MAJOR CONTRIBUTOR TO GREENHOUSE GASES
• 6 TIMES MORE THAN THE WORLD AVERAGE RATE
• GREATER THAN BOTH JAPAN USA
• VICTORIA HAS AN EVEN HIGHER PER CAPITA OUTPUT

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GOAL SET FOR 20 REDUCTION IN CO2 EMISSION BY
2010.

• IN GLOBAL SENSE
• ELECTRICITY CONTRIBUTES 25 OF ALL CO2
  EMISSIONS REPRESENTING 14 OF ALL GREENHOUSE
  GASES GENERATED AND VICTORIA IS RESPONSIBLE FOR
  0.1.

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ALTERNATIVES

• COGENERATION RENEWABLE ENERGY
• REMOTE AREA POWER SUPPLIES
• ENERGY AUDITS
• COGENERATION -- PROVEN REDUCTION OF GREENHOUSE
  GAS EMISSION REDUCTIONS

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CALCULATIONS OF POTENTIAL EMISSION SAVINGS
DEPENDS ON

• ? HOW MUCH COGEN IS ASSUMED TO BE POSSIBLE
• ? TYPE OF GENERATION BEING DISPLACED BY
  COGENERATION
• ? HEAT TO POWER RATION AND CAPACITY FACTOR OF THE
  COGENERATORS
• NO AGREED UPON ESTIMATES OF THE TECHNICAL AND
  ECONOMIC POTENTIAL FOR CONERATION IN AUSTRALIA

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AVERAGE EMISSIONS SAVINGS WILL BE ASSUMED SUCH
THAT RECIPROCATING ENGINE COGENERATORS
DISPLACES 910 gCO2/kWh GAS TURBINE
COGENERATORS DISPLACES 870 gCO2/kWh
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ASSUME GAS TURBINE COGEN PLANT TO OPERATE AT
CAPACTITY FACTOR OF 80 AND RECIPROCATING ENGINE
COGEN PLANT TO OPERATE AT CAPACTITY FACTOR OF 40
HEAT TO POWER RATIO 1.5
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500 MW OF GAS RECIPROCATING COGENERATOR OPERATION
AT A CAPACITY FACTOR OF 40, THE ANNUAL REDUCTION
IN CO2 EMISSIONS IS CALCULATED AS
FOLLOWS500,000 kW X 8760 h X 40 X 910
g/kWh 1,600 kt
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1000 MW OF GAS TURBINE COGENERATOR OPERATING AT A
CAPACITY FACTOR OF 80
1,000,000 kW X
8760 h X 80 X 870 g/kWh 6,100 ktONLY CO2
EMISSIONS CONSIDERED!ANALYSIS SHOULD CONSIDER
CH4 NOx .THEREFORE CO2 EMISSION WILL CHANGE BY
FEW .
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Species Gas turbine g/kWh Gas engine Gas boiler Black coal power station Brown coal power station
CO2 520-620 420-650 220 900-990 1,160-1,400
NOx 0.5-0.6 4-20 0.26 4-5 6.8-6.9
CO 0.3-0.6 1.5-2.5 0.07 0.09-0.16 0.1-0.2
CH4 0.1-0.2 1.5-2.5 0.07 0.25-0.27 0.03-0.05
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CO2 SAVINGS FROM COGENERATION
400 kW GAS TURBINE
CO2 SAVINGS DUE TO DISPLACED
ELECTRICITY ARE THE DIFFERENCE BETWEEN

COAL FIRED POWER STATION EMISSION
950 g/kWh (BLACK COAL)

GAS ENGINE EMISSION 530
g/kWh NET
420 g/kWh
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HEAT TO POWER RATIO 1 (TYPICAL GAS FIRED
COGENERATOR) CO2 SAVINGS DUE
TO DISPLACED BOILER FUEL ARE FOR 400 X 1.0
400 kW (THERMAL) OF HEAT CO2
EMISSIONS FOR GAS FIRED BOILER ARE 220 g/kWh
(THERMAL) AND THE COGENERATOR PLANT GENERATES NO
ADDITIONAL CO2 IN MEETING THE HEAT REQUIREMENTS.


THEREFORE TOTAL CO2 SAVING IS THUS (420 220 X
1.0) 640 g/kWh (ELECTRICAL)
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GAS FIRED COGEN CAPACITY
Country Cogen capacity (MW) Generator capacity (MW) Cogen as of the total
Australia 2082 41000 5.1
Japan 180000 6.5
UK 45000 7.0
USA 745600 8.0
Netherlands 15900 29
Spain 28420 6.5