Cogeneration - ULisboa · PDF fileIn the gas turbine cycle the injection of steam (generated in the recover ... electric energy generated by the cogeneration plant in ... the EEGO

Cogeneration

•Cogeneration Definition

•Thermodynamics background

•Cogeneration Parameters

•National Legislation

•Cogeneration Systems & Technologies

•Cogeneration in Portugal

•Cogeneration Facilities (examples)

• Industrial Sector

• Building Sector

Equipamentos Térmicos

Cogeneration Definition

What is cogeneration

Cogeneration: simultaneous production of power and heat,

with a view to the practical application of both products


Cogeneration Definition

What is cogeneration

• Integrated system

• Located at or near a building/facility

• A way of local energy production

• Uses heat that is lost otherwise (cooling, heating,

dehumidification and process heat)

• Way to use energy more efficient

• Different areas of application

• Different technologies


Cogeneration Synonyms

• Cogeneration

• Combined Heat and Power (CHP)

• Cooling, Heating and Power (CHP)

• Trigeneration (Trigen)

• Integrated Energy Systems (IES)

• Building Cooling, Heating, and Power (BCHP)


• Improves energy efficiency

• Conserves natural resources (fossil fuels)

• Lower emissions (including CO2)

• Lower energy costs

• If heat fits demand, cheapest way of electricity production

• Improves security of supply

• Reduces transmission and distribution losses

• Enhances competition

Benefits of Cogeneration


Thermodynamics and Cogeneration

Thermodynamics:

To produce work from heat is necessary a thermal cycle and part

of the energy (heat) obtained from the hot reservoir is release to

the could reservoir.

Carnot Cycle Efficiency

TB - Cold reservoir temperature

TA - Hot reservoir temperature

Cogeneration:

Is necessary produce heat at an appropriate temperature (Qu

useful Heat).


Combined Gas Turbine Cycle

The combine Gas turbine cycle can be used as a cogeneration

system.

Even when useful heat are not produced, there are a recover of

heat of the gas turbine in the recover boiler. The generated steam

is used tor produce electricity by a Rankine Cycle.

The efficiency of the combined cycle is the sum of the efficiency of

both Cycles


Cogeneration Parameters I

• Electrical/Mechanical Efficiency / Rendimento Mecânico/Electico

•Global Efficiency / Rendimento global ou Factor de utilização de

Energia

•Heat/Power ratio / Razão Calor/Electricidade


Cogeneration Parameters II

• FESR-Fuel Energy Saving ratio / PEP – Poupança de Energia

Primária

• EEE-Equivalente electrical efficiency / REE - Rendimento Elétrico

Equivalente

specific consumption (inverse)


Equivalent Electrical Efficiency

Rendimento Eléctrico equivalente

• DL 538/99 – EEE = 55 % (from 1999)

-EEE = 45 % (1995-1999)

• DL 313/01 from 2001 defines the EEE was a function of the Fuel used in the

Combined heat and Power Plant

•55 % Natural Gás, LPG-liquefied petroleum gas, liquid fuel (not fuel oil)

•50 % Fuel oil, heavy fuel oil

•45 % Biomass or residual fuels with support

•Reference boiler efficiency

•90 % - Fossil Fuel

•70 % - Renewable Fuel

• CR - Energy from Renewable Fuel

•The FESR depends on the Country Electric Systems


Fuel input

Separate

generation

Fuel input

Cogeneration

92

Electricity

35

Heat

50 53

100

Power plant

h = 38%

Boiler

h = 95%

Electricity

h = 35%

Heat

h = 50%

Total

145

Total

100

Energy conservation = (145-100)/145 = 31%

Conventional Generation Versus

Cogeneration


Fuel input

Separate

generation

Fuel input

Cogeneration

81

Electricity

35

Heat

50 53

100

Power plant

h = 43%

Boiler

h = 95%

Electricity

h = 35%

Heat

h = 50%

Total

134

Total

100



Cogeneration


Fuel input

Separate

generation

Fuel input

Cogeneration

64

Electricity

35

Heat

50 53

100

Power plant

h = 55%

Boiler

h = 95%

Electricity

h = 35%

Heat

h = 50%

Total

117

Total

100



Cogeneration


Parameters analyze

Thermal

Power Plant

Boiler Heat


Influence of increase the heat production

with a low efficiency equipment

The demand

of heat

increase

The demand of

Heat/Electricity

change over the

year but the

legislation is based

on the annual

value


FESR

Influence of the electric and thermal efficiency on FESR for

different values of Heat/Electricity ratio


FESR/Global Efficiency Specific

technologies

Heat/Electricity ratio

typical values:

TG Gas Turbine: 0,5-1,5

TV Stream Turbines: 1-4

(back pressure)

Source: Pita, 1995


How cogeneration Saves Energy?


Thermodynamic Cycles Classification

• Depending on the temperatures at the thermal energy is used

-Bottom Cycles (Heat → Power/Work)

-Top Cycles (Power/Work→Heat)

• Depending on the Technologies

•Gas Cycles – Gas turbines, Diesel/SI Engines with recovery boiler to produce

steam or with the use of flue gases direct on a process (greenhouses, drying

processes)

•Steam Cycles (Rankine cycles) – Water/steam is the work fluid. The hot

water/steam could be used directly on a process or as a energy transport fluid.

•Back Pressure Turbines/ Turbinas de Contrapressão (process that need

steam at an elevate temperature or at high pressure)

•Extraction Condensing Turbines/ Turbinas de Extracção/Condensação to

maximize the Electric generation

•Gas turbine combined cycle – Gas turbine cycle with a recover boiler to

generate steam used in a Rankine Cycle

•Others: Heat Pumps, Fuel Cells


Technologies Main Properties

•The efficiency of a Rakine cycle can reach 40 % and the gas turbine combined

cycle 55 %

•For all cases the global efficiency is near 80 % in CHP

•CHP whit heat pumps have normally a Global Efficiency greater than 100 %

Technology Power (MW) Electric

Efficiency

Extraction/Condensing Steam Turbine 30-300 0.25-0.3

Back Pressure Stream Turbines 1-200 0.2-0.25

Gas Turbines Cycles (0.15) 1-150 0.18-0.35

Internal Combustion Engines 0.05 – 25 0.35-0.4

Fuel Cells 0.005 – 0.2 0.37-0.4


Turbine Cycles used on Electric Power

Generation

Cycle

Source: Horlock, 1987

W Q The electric efficiency increase

Gas Turbine

Steam Turbine

Combined Gas Turbine

The cycle with the lower

electric efficiency allows the

use of heat at a higher

temperatures

In the steam turbine and

combined gas turbine cycle

to maximize the electric

efficiency the heat should be

reject at the lower possible

temperature



In the steam turbines plant an

increase in the useful Heat Qu

decrease the electric efficiency

Its normal have several levels

of temperature to use the Qu

In the steam turbine and

combined gas turbine cycle

the thermal energy is used to

generate steam in the recover

boiler, In the stream turbine

cycle the steam is expand in a

turbine to produce electricity

Cycle

Sigel Turbine Cycles for Combined Heat

and Power Plats


Cogeneration Parameters for Single

Turbines Cycles

Source: Horlock, 1987 (reference values considered ηT=0.9 and ηE=0.4)

Cycle E Qu ηg FESR QU/E

Extraction/Condensing Steam Turbine 0.38 0.10 0.48 0.057 0.26

Back Pressure Stream Turbines 0.25 0.60 0.85 0.235 2.4

Gas Turbines Cycles with recuperator 0.30 0.55 0.85 0.265 1.83

Combined gas turbines (Gas/back pressure Steam Turbines)

0.40 0.42 0.82 0.318 1.05

In the gas turbine cycle the injection of steam (generated in the recover

boiler) in the turbine increase the electric capacity and the electric efficiency

(STIG).


CHP Applications


Main Cogeneration Technologies



* taken from Cogeneration Guide, Cogen Europe

Typical Cogeneration Performance

Parameters


DL 23/2010 de 25 de Março de 2012

•Adaptation of the European directive 2004/8/CE

• Defines benefits/premium to the cogenerations sector based on:

1) Reduction of the primary energy consumption and CO2 emissions

2) Promote the high efficiency cogeneration plants and renewable

cogeneration based on renewable sources of energy

3) Promote the integration of Cogeneration in the electricity market

•Define two exploration regimes

•General regime (all capacity): The market define the energy price

(temporary-benefit/premium for Plant with Electric capacity < 100 MW)

•Special regime (Electric capacity < 100 MW):

•The market define the Heat price

•The tariff of the electricity have benefit/premium based on the efficiency


Portaria 140/2012 de 14 de Maio de 2012

•Review of the Cogeneration Electric Tariff

• Reference tariff for the Natural Gas, LPG or liquid Fuel (except Fueloil)

Cogeneration Plants:

• 89.89 €/MWh for Electric capacity < 10 MW

• 80.44 €/MWh for Electric capacity between 10 MW and 20 MW



•Reference tariff for the Cogeneration from renewable sources:



•Reference tariff for the Fueloil Cogeneration Plants:



•Hora ponta/hours with high electricity demand + 10%

•Vazio e supervazio/ hours with low electricity demand -13 %


Prémios de eficiência / Efficiency

premium

a) PEm Efficiency premium value in month m

b) PC Reference costs for the valorization of Primary Energy saving 28.71 €/MWh

c) PEP Primary energy savings (certified)

d) EEPlm Net electric energy generated by the cogeneration plant in month m

(total electric energy generated – electric energy consumed by the Cogeneration Plant)

e) K Primary energy saved differentiates factor

(0.5 to high efficient cogeneration plant and 0.3 efficient plant)

f) EP/EE Ratio between the Primary Energy consumed by the Cogeneration Plant

and the Electric energy generated (typical values)


Ratio EP/EE

i) Natural gas Internal combustion engines: 2.86

ii) Gas Turbines (Natural Gas) eclectic capacity < 20 MWe: 3.70

iii) Gas Turbines (Natural Gas) eclectic capacity > 20 MWe: 3.12

iv) Fueloil Internal combustion engines: 2.60

v) Steam turbines: 5

vi) Combined gas turbines: 2.5

vii) Renewable cogenerations plats: 5



Transition Regime:

•Plants with electric capacity > 20 MW

•The transition to the new remuneration regime occurs at the beginning of

the month following the EEGO audit (EEGO - entity that certifies the

primary energy savings)

•For all other cases the transition occurs in the following quarter

•During the extension period, the reference tariff for no renewable

installations is depreciated annually by one percent, for installation with a

capacity of 20 MW or less



Cogeneration Classification:

•According to capacity

-< 1 MW Small Cogeneration

-< 50 kW Micro Cogeneration (Biomass Plant Electric capacity < 3.68 kWe

have a subsidized regime DL 363/2007)

•introduces efficiency levels :

-high efficient cogeneration plant:

-Efficiency: Other cases


Electric Energy Certification

•The electricity produced in cogeneration plant with high efficiency is certified

based on a series of data (fuel, amount of heat used, PEP, CO2 emissions)

•EEGO – Is the entity responsible for certificates the Cogenerations electrical

energy (and control the CO2 emissions)

•DGEG – Is the entity that identify the high efficiency Cogenerations Plants.

•For the installations type a) and c) the annual global efficiency as to be > 80 %

•For the installations type b), d), e), f), and g) as to be > 75 %

•When the annual global efficiency are lower, the C implicit value is used to

calculate the:

ECHP = HCHP/C


Cogenerations Installations Types

a) Combined gas turbine cycle with heat recover 0.95

b) Back pressure steam turbines 0.45

c) Extraction/condensing steam turbine 0.45

d) Gas turbine wit heat recovery 0.55

e) Internal combustion Engines 0.75

f) Microturbines

g) Stirling Engines

h) FuelCells

i) Steam Engines

j) Rankine Organic Cycles

l) Other technologies

Technologies for small plants

Implicit ratio

C = E/H


Economics

Costs:

• Capital

• Operation and maintenance

• Fuel

Benefits:

• Heat

• Electricity less purchase

sell to grid

Economic value of cogeneration

• Depends very much on tariff system

• Heat: avoided cost of separate heat production

• Electricity: less purchase (kWh); sale of surplus electricity and peak

shaving (kWe)

• Carbon credits

Cogeneration Economics Analysis


Economic Analysis

PT-Payback Time \ Tempo de retorno do investimento

NPV - Net Present Value \ VAL – Valor Atual líquido

IRR - Internal Rate of Return \ TIR – Taxa interna de Rentabilidade

•The Payback time in a first approach is determine by:

PT = Initial Investment / Annual Cash flow

Cash flow= (Revenues - Expenses)

•NPV/VAL:

CFi – Cash Flow in year i

Ii – Investment value in year i

ai – Discount Rate (the rate of return that could be earned on an investment in

the financial markets with similar risk.); the opportunity cost of capital

i – time period

•TIR/IRR- The discount rate that makes the net present value of all cash flows from a

particular project equal to zero. Generally speaking, the higher a project's internal rate of

return, the more desirable it is to undertake the project.

http://en.wikipedia.org/wiki/Rate_of_return

http://en.wikipedia.org/wiki/Opportunity_cost


Economic Analysis

IRR - Example

Year (i) Cash flow (i)

0 -123400

1 36200

2 54800

3 48100

In this case r = 5.96%


Economical Parameters

•The Fuel price/cost

•The Electricity price/cost

•The useful heat price/cost

•The cost of the useful heat depends of the temperature level at the

heat is used.

•Price-weighted Global Efficiency / Factor de utilização de energia

ponderado pelo preço

*Heat pump produce heat by a compressor cycle (using electricity) PE = 0.1

Fuel Heat €/kWh(ηT = 90 %)

Propane/Butane Gas LGP 0.09

Natural Gas 0.05

Diesel for heat 0.05

*Heat pump (Cop = 4) 0.03

Heat approximate costs (Investment costs not included)


Cogeneration Economics


Cogeneration Economics


Cogeneration System Design Options


Reference Efficiency Values

Source: Manual de Procedimentos da EEGO Entidade Emissora de Garantias de Oringem

Available: www.dgeg.pt (areas sectoriais-energia electrica-produção em regime especial

http://www.dgeg.pt/





http://www.dgeg.pt/





http://www.dgeg.pt/





http://www.dgeg.pt/



Source: Cogen Portugal





Example


Otto Natural gas Engine Gas engine

Nominal Electrical Power 1100 kW

Fuel Natural Gas

Electrical Grid Connection Tension 0.380 kV

Annual Average Temperature 19 ºC

Construction year 2006

Annual operating hours 8 000 h

Fuel consumption (LHV based) 25 150 MWh

Useful Heat 10 560 MWh

Electrical Energy Generated 8 800 MWh

Electrical Energy Consumptions 176 MWh

Global Efficiency

FESR-Fuel Energy Saving Ratio

Reference Electrical efficiency corrected by the average temperature

Fraction of Electric Energy Exported to the National Electric System

Correction factors


CO2 Emission- EEGO Proceedings

Manual • CO2 emissions from CHP

• Avoid CO2 emissions

The CO2 emissions factor are defined by the IPCC, intergovernmental Panel on Climate

Change, publish in Despacho 17313/2008 (June 26).



Despacho 17313/2008 (June 26)


Demand Heat Curve


Cogeneration in Portugal

The installation of Cogeneration Plants in Portugal occurred in three phases:

-1st Large industries

-2nd The possibility of sold electricity to the National Electric System

-3rd The introduction of Natural Gas in Portugal (Otto, GT and CC)

Cogeneration Install Capacity in Portugal

Natural gas

Engines

Natural gas

Turbines

Heavy

Fueloil

Engines

Back

pressure

Turbines

Propane

Engines Biogas

Engines Micro

Turbines

New CHP Plants:

Combined gas turbine

cycles in Sines and

Matosinhos Petroleum

Refinery



Sector by Technologies

Cogeneration Install Capacity by Technologies

The back pressure Steam turbine are installed

mainly in the Pulp paper and chemical Industries

Natural gas

Engines

Natural gas

Turbines Heavy Fueloil

Engines

Back pressure

Turbines

Propane

Engines

Biogas

Engines

Micro

Turbines

Pulp Paper Industry Chemical and

Petroleum Industry

Food Industry

Others Industry Textile Industry

Total capacity at the end of 2005 1200 MW

Actually the Combined Gas Turbines and the Gas

turbines are present in some of this sectors


Sector by Fuel

Fueoil Cogeneration Install Capacity by Sector

Other include the building Sector

Fueloil Engines have environmental

limitations

Some Fueloil Engines can be converted

to Natural Gas

Natural Gas Cogeneration Install Capacity by Sector

Total Natural Gas Capacity at the end 2005 322 MW

Wood Food

Textile Others

Chemical

Glass an Ceramics

Pulp paper

Tertiary

Wood

Food

Textile

Others

Chemical

Glass an Ceramics

Pulp paper

Tertiary


Pulp Paper Industry Cogeneration Plant

Two steam boiler produce steam for one

circuit

The steam circuit have different pressures

levels

The biomass boiler burn wood residues

rejected by the pulp paper process

The recover boiler burn black liquor


Internal Combustion Engines


Capacity MW

Input Energy Fraction

Electricity 7.5 40 %

Heat 6.7 35 %

Capacity MW

Economizer 1.0

Recover Boiler 3.0

Jacket 2.7


Commercial Center Colombo

Cogeneration Plant

ηg = 86 %

EEE = 37 %

Electric Capacity 37 MW

Shops 11.2 MW

Hyper Market 4 MW

Commons Spaces 21.7 MW

Cooling Capacity 14.8 MW

3 Compressor Chillers

2 Absorptions Chillers

Diesel /Fueliol Engines

Convertibles to

Natural gas


Combined Gas Turbine Plants

GALP - Oil Refining Plants - combined gas cycle

Electric Capacity [MW]

Exported Eclectic

Energy (MW)

Steam Production (t/h; bar)

EEE/REE (%)

Matosinhos 80 60-80 200; 67 65

Sines 2 X 80 100-140 415; 82

Fuel: Natural Gas and Refinery Gas


• Industrial cogeneration wood and agro-industries, food processing, pharmaceutical, pulp

and paper, oil refinery, textile industry, steel industry, cement

industry, glass industry, ceramic industry

• Residential/commercial/institutional cogeneration hospitals, schools and universities, hotels, houses and apartments,

stores and supermarkets, office buildings

Typical Cogeneration Applications


Trigeneration Plant Climaespaço

absorption chiller

Gas turbine

Heat exchanger inside

the buildings


Trigeneration Plant Climaespaço


Fuelcell IST


Cogeneration as a Share of National

Power Production in EU


Main Steps to Realize The Cogeneration

Project

1) Obtain the representative annual diagram of useful/economical Heat/Cooling based on

demand.

1) Based on the dally diagram for different month of the year

2) Careful with the temperature/condition necessary to use the heat

2) Research /define the technology appropriate to the Energy demand

1) Electrical capacity

2) Economical Useful Heat capacity

3) Turn down ratio

4) Availability Factor

5) Type of Fuel and efficiency of the equipments

6) Energy needed to operate (peripherals equipments)

7) Energy Storage Systems

8) Startup time

9) Live time of the equipments

3) Define the business model and the Operation Conditions

1) Useful heat price – Based on Market values

2) Electricity Energy Price – Based on Market values

3) Investment

4) Maintenance/Operational Cost – Based on Technical information

5) Other cost (environmental tariffs, eventual financial penalties when the cogeneration plant have

to stop, other cost associate to the project, taxis,)


Main Steps to Realize The Cogeneration

Project

4) Verify The Legislation/Regulation

Check if the defined operating conditions are according to the legislation / regulation

5) Economical Analisys

Sensitivity analysis of the main project variables

The Final Report:

A descriptions of the heat useful demand and the conditions of the heat client

A descriptions of the CHP and the technology

(technical/economical justification of the option)

Economic analysis of the project

(with a justification of the values used)

Technique analysis that proves the cogeneration benefits:

Reduction of the primary energy consumption

Increasing the efficiency

Reduction of the green gas emissions


Useful Documentation

Available Online

• Decreto Lei n.º 23/2010 de 25 de Março

• Lei n.º 19/2010 de 23 Agosto

• Portaria n.º 140/2012 de 14 de Maio

• Portarian.º 325-A/2012 de 16 de Outubro

• Despacho 17313/2008 de 26 de Junho

• Manual de Procedimentos da Entidade Emossora da Garantias de Origem

www.dgeg.pt (areas sectoriais-energia electrica-produção em regime especial

• Cogen Portugal- Cogeração

http://www.cogenportugal.com/ficheirosupload/Brochura%20Cogera%C3%A7%C3%A3o.pdf

• Estudo do Potencial de Cogeração de Elevada Eficiência em Portugal

(Direcção Geral de Energia e Geologia)

http://www.dgeg.pt/

http://www.dgeg.pt/

http://www.dgeg.pt/

http://www.dgeg.pt/

http://www.dgeg.pt/

Documents

Cogeneration - ULisboa · PDF fileIn the gas turbine cycle the injection of steam (generated in the recover ... electric energy generated by the cogeneration plant in ... the EEGO