Prof. R. Shanthini 17 March 2012 Module 11 Energy Management (continued) Energy management basics Energy audit Demand-side management Life-cycle assessment.

Prof. R. Shanthini 17 March 2012

Module 11

Energy Management (continued)

Energy management basics

Energy audit

Demand-side management

Life-cycle assessment

Exergy analysis

Carbon and ecological footprints

Clean development mechanism


Selected topics in Energy Management:

Energy audit



Exergy analysis (continued)




Exergy is the maximum theoretical work that can be obtained from an amount of energy.

Energy is conserved.

Exergy (which is the useful work potential of the energy) is not conserved.

Once the exergy is wasted, it can never be recovered.


Exergy (formal definition) and the Dead State

The useful work potential of a system is the amount of energy we could have extracted as useful work.

The useful work potential of a system at the specified state is called exergy.

Exergy is a property and is associated with the state of the system and the environment.

A system that is in equilibrium with its surroundings has zero exergy and is said to be at the dead state.

YA Çengel and MA Boles, Thermodynamics: An Engineering Approach, 5th Ed.



Exergy Forms


There are 4 components:

– Kinetic exergy of bulk motion

– Potential exergy of gravitational or electro-magnetic field differentials

– Physical exergy from temperature and pressure differentials

– Chemical exergy arising from differences in chemical composition

We can ignore the first two for many industrial and economic applications.


Exergy of kinetic energy

Kinetic energy is a form of mechanical energy and can be converted directly into work.

Kinetic energy itself is the work potential or exergy of kinetic energy independent of the temperature and pressure of the environment.

Specific exergy of kinetic energy:


)kJ/kg(2

2Vxke

It is also known as kinetic exergy EKN


Exergy of potential energy

Potential energy is a form of mechanical energy and can be converted directly into work.

Potential energy itself is the work potential or exergy of potential energy independent of the temperature and pressure of the environment.


Specific exergy of potential energy:

)kJ/kg(gzxpe

It is also known as potential exergy EPT


2

0 0 0( ) ( )2

Vh h T s s gz


It is also known as physical exergy EPH

Physical exergy

Physical exergy from temperature and pressure differentials


2

0 0 0( ) ( )2

Vh h T s s gz


The exergy change of a fluid stream as it undergoes a process from state 1 to state 2 is

2 22 1

2 1 2 1 0 2 1 2 1( ) ( ) ( )2

V Vh h T s s g z z

The exergy of a flow (stream) on a unit mass basis is written as follows:

Exergy of a flow stream


Exergy transfer by heat transfer

By the second law we know that only a portion of heat transfer at a temperature above the environment temperature can be converted into work.

The maximum useful work is produced from it by passing this heat transfer through a reversible heat engine.

The exergy transfer by heat is

0heat 1

TX Q

T



Derivation is given on the following slides.



= Tenv 1 - TH

Hot reservoir at TH K

Heat engine converts heat into work

Environment at Tenv K

ηthermal = Wout Qin

Wout

Qin

Qout

ηCarnot

ηCarnot = Wmax

Qin

Exergy = Wmax

= ηCarnot Qin

= Qin

Tenv 1 - TH


Derivation ends here.



Exergy transfer by work

Exergy is the useful work potential, and the exergy transfer by work can simply be expressed as

surrwork

(for boundary work)

(for other forms of work)

W WX

W

where , P0 is atmospheric pressure, and

V1 and V2 are the initial and final volumes of the system.

The exergy transfer for shaft work and electrical work is equal to the work W itself.

Note that exergy transfer by work is zero for systems that have no work.

surr 0 2 1( )W P V V



Exergy transfer by mass

Mass flow is a mechanism to transport exergy, entropy, and energy into or out of a system.

As mass in the amount m enters or leaves a system the exergy transfer is given by

X mmass


Note that exergy transfer by mass is zero for systems that involve no flow.

2

0 0 0( ) ( )2

Vh h T s s gz

where


The Decrease of Exergy Principle

The exergy of an isolated system during a process always decreases or, in the limiting case of a reversible process, remains constant.

This is known as the decrease of exergy principle and is expressed as

isolated 2 1 isolated( ) 0X X X



Exergy Destruction

Irreversibilities such as friction, mixing, chemical reactions, heat transfer through finite temperature difference, unrestrained expansion, non-quasi-equilibrium compression, or expansion always generate entropy, and anything that generates entropy always destroys exergy.

The exergy destroyed is proportional to the entropy generated as expressed as

destroyed 0 genX T S



The decrease of exergy principle does not imply that the exergy of a system cannot increase.

The exergy change of a system can be positive or negative during a process, but exergy destroyed cannot be negative.

The decrease of exergy principle can be summarized as follows:

destroyed

0 Irreversible proces

0 Reversible process

0 Impossible process

X



Exergy Balances

Exergy balance for any system undergoing any process can be expressed as

Total Total Total Change in the

exergy exergy exergy total exergy

entering leaving destroyed of the system


For a reversible process, the exergy destruction term is zero.


in out destroyed system

Net exergy transfer Exergy Changeby heat, work, and mass destruction in exergy

X X X X

General:


in out destroyed system( )x x x x

General, unit-mass basis:


Rate of net exergy transfer Rate of exergy Rate of change by heat, work, and mass destruction of exergy

X X X X

General, rate form:



Rate of net exergy transfer Rate of exergy Rate of change by heat, work, and mass destruction of exergy

X X X X

General, rate form:


0heat

work useful

mass

system system

1

/

TX Q

T

X W

X m

X dX dt

where

2

0 0 0( ) ( )2

Vh h T s s gz


Chemical exergy

Even when a system is in a state of thermomechanical equilibrium with the environment, it may still be out of equilibrium with that environment owing to the difference in the composition and nature of the components making up the system and the environment, respectively.

These differences lead to values for the chemical exergy.

For example, pure nitrogen and oxygen have nonzero chemical exergies because their mole fraction in the environment is different from unity (1).


Chemical exergy in Iron Production

Production of pure iron (Fe) from iron oxide (Fe2O3).

This requires exergy from burning coke (pure carbon).

The reaction is as follows:

2Fe2O3 + 3C 4Fe + 3CO2

Carbon dioxide (CO2) is the waste product from the reaction.

3/4 moles of CO2 is produced per mole of Fe manufactured.


ComponentChemical exergy

(kJ/mol)

Number of moles in the

reaction Chemical

exergy (kJ)

Fe2O3 16.5 2 33

C 410.3 3 1230.9

Total chemical exergy of reactants 1263.9

Fe 376.4 4 1505.6

CO2 19.9 3 59.7

Total chemical exergy of products 1565.3

2Fe2O3 + 3C 4Fe + 3CO2

Exergy imbalance = 1565.3 – 1263.9 = 301.4

2Fe2O3 + 3C 4Fe + 3CO2 has the correct mass balance, but incorrect exergy balance



(kJ/mol)


reaction Chemical

exergy (kJ)

Fe2O3 16.5 2 33

C 410.3 3.76 1542.7

O2 4.4 0.76 3.3

Total chemical exergy of reactants 1579

Fe 376.4 4 1505.6

CO2 19.9 3.76 74.8


Exergy balance = 1580.4 – 1279.0 ≈ 0

2 Fe2O3 + 3.76 C + 0.76 O2 4 Fe + 3.76 CO2

On the input side oxygen has been added to fulfill the balance of the extra C required


2 Fe2O3 + 3.76 C + 0.76 O2 4 Fe + 3.76 CO2

3.76/4 moles of CO2 is produced per mole of Fe manufactured

Molecular mass of Fe is 56 and that of CO2 is 44.

(3.76/4) x 44 kg of CO2 is produced per 56 kg of Fe.

0.74 kg of waste CO2 is produced per kg of Fe manufactured.

This is the thermodynamic minimum.

In reality, blast furnace has an average efficiency of 33%.

So, a mole of C accounts for only 135.4 kJ instead of 410.3 kJ.

As a result, we require 12.42 moles of C instead of 3.76 moles.



(kJ/mol)


reaction Chemical

exergy (kJ)

Fe2O3 16.5 2 33

C 410.3 12.42 5095.9

O2 4.4 9.42 41.4

Total chemical exergy of reactants 5170.3

Fe 376.4 4 1505.6

CO2 19.9 12.42 247.2


Exergy balance = -3417.6

2 Fe2O3 + 12.42 C + 9.42 O2 4 Fe + 12.42 CO2 + heat

(12.42/4) x 44 kg of CO2 is produced per 56 kg of Fe.

2.44 kg of waste CO2 is produced per kg of Fe manufactured.


• Prime movers ( electricity)• Transport• High temperature process heat• Mid and low temperature process heat• Lighting• Non-fuel application

Types of exergy service


Exergy Analysis:

Transactions of the ASME, Vol 119, Sept 1997, pp200-204


Exergy Analysis:



Exergy Analysis:



Exergy efficiency of useful work categories:

B. Warr et al. / Ecological Economics 69 (2010) 1904–1917











Energy and exergy efficiencies of space heating technologies:



Aggregate exergy efficiency:







Exergy maps also available at http://gcep.stanford.edu/research/exergycharts.html


Selected topics in Energy Management:

Energy audit



Exergy analysis




Let’s take a look at how globalization assists in combating global warming.

Global warming is said to have caused by greenhouse gases (GHG).

GHGs are gases in an atmosphere that absorb and emit radiation within the thermal infrared

range. This process is the fundamental cause of the greenhouse effect.

http://en.wikipedia.org/wiki/Greenhouse_gas#cite_note-0


The Greenhouse effectA T M O S P H E R E

S U N


The main GHGs in the Earth's atmosphere are water vapor, carbon dioxide, methane,

nitrous oxide, and ozone.

Without GHGs, Earth's surface would be on average about 33°C colder than at present.


Rise in the concentration of four GHGs


Global Warming Potential (GWP) of different GHGs


The burning of fossil fuels, land use change and other industrial activities since the Industrial revolution have increased the GHGs in the atmosphere to such a level that the earth’s surface is heating up to temperatures that are very destructive to life on earth.


Time taken to reach equilibrium after the emissions peak

CO2 emissions

CO2 stabilization takes 100 to 300 years

Temperature stabilization takes a few centuries

Sea level rise due to thermal expansion takes centuries to millennia

Sea level rise due to ice melting takes several millennia

CO2 emissions peak 0 to 100 years

Today 100 years 1000 years

Magnitude of response


United Nations Framework Convention on Climate Change

(UNFCCC)

Kyoto Protocol

So there was an urgent need for global action to reduce GHGs.

One global treaty

Another global treaty


United Nations Framework Convention on Climate Change (UNFCCC)

UNFCCC sets an overall framework for intergovernmental efforts to tackle the challenge posed

by climate change.

It recognizes that the climate system is a shared resource whose stability can be affected by industrial

and other emissions of carbon dioxide and other GHGs.

The objective of the treaty is to stabilize GHG concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the

climate system.

Source: http://unfccc.int/essential_background/convention/items/2627.php



Under the Convention, governments:

- gather and share information on GHG emissions, national policies and best practices

- launch national strategies for addressing GHG emissions and adapting to expected impacts, including the provision of financial and technological support to developing countries

- cooperate in preparing for adaptation to the impacts of climate change

Source: http://unfccc.int/essential_background/convention/items/2627.php



May 09, 1992: The Convention was adopted at the United Nations Headquarters, New York.

June 1992 – June 1993: It was open for signature at the Earth Summit (held in Rio de Janeiro) and thereafter at the United Nations Headquarters, New York.

March 21, 1994: The Convention entered into force.

Source: http://unfccc.int/essential_background/convention/status_of_ratification/items/2631.php

Currently, there are 194 Parties (193 States and 1 regional economic integration organization) to the UNFCCC.


Kyoto ProtocolThe Kyoto Protocol is an international agreement linked to the UNFCCC, and it is adopted at third Conference of Parties (COP) to the UNFCCC in Kyoto, Japan, in 1997.

The major distinction between the Protocol and the Convention is that while the Convention encouraged industrialised countries to stabilize GHG emissions, the Protocol commits them to do so.

Recognizing that developed countries are principally responsible for the current high levels of GHG emissions in the atmosphere as a result of more than 150 years of industrial activity, the Protocol places a heavier burden on developed nations under the principle of “common but differentiated responsibilities.”

Source: http://unfccc.int/kyoto_protocol/items/2830.php


Dec 11, 1997: The Kyoto Protocol was adopted in Kyoto, Japan.

Feb 16, 2005: Protocol entered into force.

Kyoto Protocol


The major feature of the Kyoto Protocol is that it sets binding targets for Annex I parties for reducing the emissions of the following GHGs: - Carbon dioxide (CO2) - Methane (CH4)

- Nitrous oxide (N2O) - Sulphur hexafluoride (SF6)

- Hydrofluorocarbon (HFC) group of gases - Perfluorocarbon (PFC) group of gases

The binding targets of Annex 1 parties amount to a total of 5.2% below that of 1990 levels over 2008-2012.


Kyoto Protocol


Australia, Austria, Belarus, Belgium, Bulgaria, Canada, Croatia, Czech Rep. Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Monaco, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Russia Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine, UK, USA

Annex 1 parties to Kyoto Protocol

Countries with economies in transition to a market economy. Annex II countries which is a subgroup of Annex 1 countries.USA has no intention to ratify the Protocol.


Emission trend of Annex 1 parties in 2005

Decreased emissions(1990 baseline)

Increased emissions(1990 baseline)


USA, which was expected to cut the emissions 7% below the 1990 level, has no intention to ratify the Protocol.

Since USA, which roughly contributes a quarter of the world’s GHGs, has not ratified the Protocol and since a number of parties to the Protocol has not so far met their Protocol emissions target, the success of the Kyoto Protocol is questionable.

Kyoto Protocol


Under the Treaty, countries must meet their targets primarily through national measures.

However, the Kyoto Protocol offers them an additional means of meeting their targets by way of three market-

based mechanisms, which are the following:

Emissions trading (ET), known as “the carbon market" Clean development mechanism (CDM)

Joint implementation (JI)

The mechanisms help stimulate green investment and help Parties meet their emission targets in a cost-effective way.

The Kyoto Mechanisms



The Kyoto Mechanisms


ET - Emissions TradingAAU (Assigned Amount Units) are exchanged between Annex I countries

JI - Joint ImplementationAnnex I investors receive ERUs (Emission Reduction Units) by investing in a project in another Annex I nation which reduces GHG emissions

CDM - Clean Development MechanismAnnex I investors receive CERs (Certified Emission Reductions) by investing in a project in a non-Annex I nation which reduces GHG emissions


Clean Development Mechanism (CDM)

Source: http://www.bellona.org/factsheets/1191918665.67

CDM is a mechanism to ensure that Annex I countries can meet their emission reduction target in a cost effective way by financing GHG emission reduction in developing countries.

If an Annex I country finance an emission reduction project in a Non-Annex I country, the project participants will be granted ”Certified Emission Reductions” (CERs), also called carbon credits.

The number of CERs granted reflects the emission reduction; an emission reduction equal to one metric ton of CO2 gives one CER.

The CERs are tradable, and they can be used to supplement national GHG emission reductions.







Annex I countries cannot base all their emission reductions on CERs.

The European Trading System (ETS) limits emission reductions covered by CERs to 10 to 30 percents; the rest must be real emission reductions in the home country.

There are two reasons for this limit; (1) to ensure that there are not too many CERs on the market (2) to ensure that Annex I countries do not base all their

emission reduction on buying CERs without reducing emissions at home.

Only projects that contribute to sustainable development in developing countries are accepted as CDM projects.




Only projects that would not have taken place without the CDM will be accepted as a CDM projects, and this is referred to as the Additionality criteria.

An example of additionality is a wind power project that is not profitable without the CDM, but with the added value of CERs it will be profitable.

A financial and/or technical analysis has to be performed to document additionality. The analysis has to highlight all reasons why the project would not happen without the CDM, and all technical, legal and infrastructural barriers must be described.




The idea behind additionality is to ensure that CDM projects results in real emission reductions that would not have happened in a business-as-usual scenario.

Another prerequisite for CDM projects is that there exists a recognised method for calculating emission reduction. This is referred to as the Methodology criteria.

Finally, CDM projects must also meet the host country’s criteria for sustainable development.




The complicated framework for registration of CDM projects has lead to criticism because several sustainable projects find the cost of CDM registration as a main barrier for the project.

As an example, several smaller solar energy projects in developing countries have not taken place because of an expensive and complicated process of CDM registration.

However, a procedure called Programmatic CDM will reduce this barrier because it allows similar projects to be evaluated in one common process instead of several individual processes.

Another problem is that many potential CDM projects do not apply for CDM status due to lack of knowledge about the CDM registration process.




CDM projects include energy efficiency, renewable energy production, methane emission reduction, and fuel switch projects.

There are CDM projects within several industrial sectors including power production; steel, cement and paper plants; renewable energy; forestation; hydropower; and biomass.

Some projects are controversial, like large water dam projects for hydropower and HFC23 projects (HFC23 is a GHG with a global warming potential 11,700 times higher than CO2). The HFC23 projects have so far been extremely profitable, and it is therefore discussed to exclude HFC23 projects from the CDM.


Clean Development Mechanism (CDM) Around half of CDM credits issued have been for destroying HFC-23 (trifluoromethane) which is emitted while making the refrigerant HCFC-22 (chlorodifluoromethane).

HFC-23 is easily removed by cheap gas scrubbers. It prevents more preferable CDM projects, like biomass or wind power, and creates a perverse incentive for companies to expand refrigerant plant capacity purely for the greater profit of destroying HFC-23 byproducts.

Montreal protocol is aimed to reduce ozone-depleting gases - for example, by replacing HCFC-22 with other HFC blends or hydrocarbons which are kinder to the ozone layer. But developing countries are allowed to increase their HCFC-22 production until 2016 and maintain that level until 2040.




There are large commercial risks due to the uncertainty of future CERs prices, since Kyoto protocol expires in 2012 and it is highly uncertain what happens with CDM post Kyoto.

Prof. R. Shanthini 17 March 2012 Source: http://www.bellona.org/factsheets/1191918665.67

There is a common international understanding that there is a need for a mechanism like CDM also beyond 2012, but one challenge is to establish a mechanism that all countries can agree on, including the U.S. and other countries that have not ratified the Kyoto protocol.



The overall objective of the energy management programme is to enhance economic activity of the country without making an additional burden on the energy sector.

It is observed that this can be achieved by realizing energy conservation equivalent to 20% of the energy consumption of year 2010, by 2020.

Sri Lanka Sustainable Energy Authority

http://www.energy.gov.lk/sub_pgs/energy_managment.html


The energy management programme launched by SLSEA has 4 facets as per given below,

The scope of the activities is to support energy efficiency improvement and conservation in all sectors, namely industrial, commercial and domestic consumer categories.


(1) Regulatory interventions

(2) Energy Efficiency services

(3) Enhancing awareness on energy conservation

(4) Facilitating funding schemes for energy efficiency improvement.




(a) Energy auditing and supportive services through Energy Services Companies (ESCOs)

(b) Training & education on energy conservation & management

(c) Facilitation services through sophisticated measuring equipment

(d) Coordinating energy management activities through Energy Managers

(e) Energy labeling of electrical appliances

(f) Introducing energy efficiency guidelines for building construction

(g) Sri Lanka National Energy Efficiency Award

(h) Software for energy system analysis

Activities:





REGULATORY INTERVENTIONS

ENERGY LABELING PROGRAMME

In the process of energy efficiency improvement, ensuring high efficiency levels of the electrical appliances used is a very important aspect.

Internationally accepted methodology for this is ‘Energy Labeling’. SLSEA has launched energy labeling process in collaboration with the Sri Lanka Standards Institute (SLSI).

Cooperation is obtained from National Engineering Research & Development (NERD) Centre and University of Moratuwa for product testing and related technological assistance.




ENERGY EFFICIENCY FINANCING

SUSTAINABLE GUARANTEE FACILITY (SGF)

(a) SGF is a mechanism providing technical and financial guarantees for energy efficiency improvement projects

(b) Participating Financial Institutes for SGF

- Hatton National Bank

- Sampath Bank

- Commercial Bank

- NDB Bank

- DFCC Bank

- Seylan Bank

- Bank of Ceylon




ENERGY EFFICIENCY SERVICES

Energy consumption baselines for industrial & commercial sectors

Energy Consumption Baselines established for some of the sectors provide some basic guideline for setting targets for the establishments in the respective sectors.




AWARENESS PROGRAMMES

Taking the message of energy conservation to end use sectors including the general public is an important aspect in carrying out energy conservation in the country.

Our programmes on awareness creation include enhancing the knowledge on energy conservation and inculcating attitudes towards energy conservation among seminars & workshops as well as print & electronic media are the different channels used in carrying out awareness programmes.

School population is a special target group, and school curriculum based awareness creation approach is in place.




AWARENESS PROGRAMMES

Taking the message of energy conservation to end use sectors including the general public is an important aspect in carrying out energy conservation in the country.

Our programmes on awareness creation include enhancing the knowledge on energy conservation and inculcating attitudes towards energy conservation among seminars & workshops as well as print & electronic media are the different channels used in carrying out awareness programmes.

School population is a special target group, and school curriculum based awareness creation approach is in place.

Prof. R. Shanthini 17 March 2012 Module 11 Energy Management (continued) Energy management basics Energy audit Demand-side management Life-cycle assessment.

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