[PDF] Compressed air energy storage type of storage compressed air

View - Download Compressed air energy storage

Previous PDF

Next PDF

IN DEGREE PROJECT TECHNOLOGY,

FIRST CYCLE, 15 CREDITS

, STOCKHOLMSWEDEN2018

Compressed air energy

storage

Process review and case study of small scale

compressed air energy storage aimed at residential buildings

EVELINA STEEN

MALIN TORESTAM

KTH ROYAL INSTITUTE OF TECHNOLOGY

SCHOOL OF ARCHITECTURE AND THE BUILT ENVIRONMENT

1

ACKNOWLEDGMENT

We would like to express our gratitude to our supervisor Assist. Prof. Justin Ning-Wei Chiu, for without

his advice and guidance the making of this report would not have been possible. Thank you! 2

INDEX OF FIGURES

FIGURE 1. SCHEMATIC IMAGE OF CAES SYSTEM. NOTE THAT THERMAL STORAGE IS OPTIONAL AS IS THE NUMBER OF COMPRESSORS

AND TURBINES. ........................................................................................................................................... 12

FIGURE 2. DETAILED DESCRIPTION OF EQUATIONS USED FOR DECIDING CHANGES IN TEMPERATURE, PRESSURE AND VOLUME FOR ALL 22

DIFFERENT STAGES IN THE CAES PROCESS. ISENTROPIC PROCESS RELATION IS ABBREVIATED AS IPE AND IDEAL GAS LAW AS IGL,

BOTH USED TO DENOTE HOW THE VALUE OF THE CONCERNED PROPERTY IS DERIVED. ..................................................... 18

FIGURE 3. LOAD PROFILES FOR ONE HOUSEHOLD DURING MONDAY-FRIDAY AND SATURDAY-SUNDAY. ...................................... 23

FIGURE . THE BLUE AND ORANGE STAPLES SHOW VARIATIONS IN PRESSURE DURING CHARGE PHASE, DISCHARGE PHASE AND THE GREY

LINES FOLLOWS THE PRESSURE IN THE STORAGE. DURING PERIODS WHERE ONLY THE GREY LINE IS PRESENT THE STORAGE HAS

BEEN EMPTIED TO MINIMUM PRESSURE AND THE SYSTEM IS AT REST. THIS FIGURE IS TRUE FOR MONDAY TO FRIDAY. ............ 2

FIGURE -. THE BLUE AND ORANGE STAPLES SHOW VARIATIONS IN PRESSURE DURING CHARGE PHASE, DISCHARGE PHASE AND THE GREY

LINES FOLLOWS THE PRESSURE IN THE STORAGE. DURING PERIODS WHERE ONLY THE GREY LINE IS PRESENT THE STORAGE HAS

BEEN EMPTIED TO MINIMUM PRESSURE AND THE SYSTEM IS AT REST. THIS FIGURE IS TRUE FOR SATURDAY AND SUNDAY EXCEPT

FOR THE SMALL DETAIL THAT FOR THE LAST HOUR OF SUNDAY THE PRESSURE INCREASES LIKE IN FIGURE TO ACCOMMODATE THE

SEVEN-HOUR CHARGE PERIOD FOR MONDAY....................................................................................................... 2

FIGURE 6. THE BLUE AND ORANGE STAPLES SHOW THE MASS THAT NEEDS TO BE EXPANDED TO SATISFY THE DEMAND OF EACH

DISCHARGE PERIOD. THE GREY LINE IS THE DIFFERENCE BETWEEN MAXIMUM AND MINIMUM MASS. .................................. 2-

FIGURE 7. AVERAGE ELECTRICITY SPOT PRICE FOR EACH HOUR DURING WEEKDAY AND WEEKDAY FOR THE OF 2017 (NORDPOOL,

2018A). ................................................................................................................................................... 26

INDEX OF TABLES

TABLE 1. EFFICIENCIES FOR VARIOUS COMPONENTS AND PROCESSES. ................................................................................ 21

TABLE 2. SPECIFIC HEAT CAPACITIES USED DURING CALCULATIONS. ................................................................................... 21

TABLE 3. ECONOMIC RESULT FOR A WEEK WITH AND WITHOUT CAES. .............................................................................. 26

TABLE . CAPITAL COST AND CHARACTERISTICS OF MAIN COMPONENTS. ............................................................................ 26

TABLE -. NET PRESENT VALUE FOR TWO SCENARIOS. ..................................................................................................... 27

3

NOMENCLATURE

Abbreviations

CAES Compressed air energy storage

EES Electrical energy storage

IGL Ideal gas law

IPE Isentropic process equations

HPC High pressure compressor

HPT High pressure turbine

LPC Low pressure compressor

LPT Low pressure turbine

NPV Net present value

RFB Redux flow batteries

TES Thermal energy storage

U-CAES Underground compressed air

energy storage

UW-CAES Underwater compressed air

energy storage

Variables

Area c

Specific heat capacity constant

volume c

Specific heat capacity constant

pressure í µ Energy í µ Mass í µÌ‡ Mass flow í µ Molar mass í µ Pressure

Heat flux

í µ Gas constant í µ Time í µ Temperature í µ Specific volume

Volume

í µ Work

Greek symbols

Heat capacity ratio

Efficiency

Subscripts

1

Inlet/Before process

2

Outlet/After process

í µ Generator

Mechanical

í µ Total í µí µí µ Atmospheric conditions

Specific

í µ Storage í µ Compressor í µ Heat í µí µ Natural gas í µí µ Round-trip 4

ABSTRACT

The potential for electrical energy storage to both provide services to the electrical grid and help to

better integrate renewable energies in the electrical system is promising. This report investigates one

type of storage, compressed air energy storage (CAES), where energy is stored by compressing air

during hours of low electricity demand and later expanding the air to generate electricity during high

demand hours. To this day it exists two large plants, but small facilities have yet to be implemented,

raising the question whether it could be viable to use CAES on a smaller scale as well. By creating a

model of a CAES system based on the principles of thermodynamics and applying it to a hypothetical

group of residences, its ability to balance daily fluctuations in electricity demand is explored. The

result show that the system is able to cover some of the demand but there is no economic profit to be

gained. The results of this report suggest that a CAES system of this size is not a viable option during

current price market for electricity in Sweden but during other circumstances it could be relevant. KEYWORDS: compressed air energy storage (CAES), electrical energy storage (EES), artificial air storage, thermodynamic analysis, economic evaluation 5

SAMMANFATTNING

NYCKELORD: komprimerad luft som energilagring (CAES), elektrisk energilagring (EES), artificiell 6

TABLE OF CONTENTS

1. Introduction..........................................................................................................................8

1.1. Purpose.......................................................................................................................................................................9

1.2. Objectives..................................................................................................................................................................9

2. Background........................................................................................................................10

2.1. Electricalenergystorage................................................................................................................................10

2.1.1. EESintheenergysystem.........................................................................................................................10

2.1.2. Electricalenergystoragesolutions....................................................................................................11

2.2. TheCAESprocess................................................................................................................................................12

2.2.1. Compression...................................................................................................................................................13

2.2.2. Storage...............................................................................................................................................................13

2.2.3. Expansion.........................................................................................................................................................15

2.2.4. Thermalstorage............................................................................................................................................15

3. Methodology......................................................................................................................16

3.1. Casestudy...............................................................................................................................................................16

3.2. LoadProfile...........................................................................................................................................................16

3.3. Calculationsforsystemdimensioning......................................................................................................16

3.4. Heattreatment....................................................................................................................................................19

3.5. Efficiencies.............................................................................................................................................................19

3.6. Constants................................................................................................................................................................20

3.7. EconomicEvaluation........................................................................................................................................21

3.8. Electricityprices.................................................................................................................................................21

3.9. Investments...........................................................................................................................................................21

4. Results.................................................................................................................................22

4.1. SystemProperties...............................................................................................................................................22

4.1.1. Loadprofile.....................................................................................................................................................22

4.1.2. Compressionandexpansionwork......................................................................................................23

4.1.3. Chargeanddischarge.................................................................................................................................23

4.1.4. Efficiency..........................................................................................................................................................25

4.1.5. Heat.....................................................................................................................................................................25

7

4.1.6. Lossduetoconstantvolumestorage................................................................................................25

4.2. Financialresults..................................................................................................................................................26

5. Discussion...........................................................................................................................27

5.1. Assumptions..........................................................................................................................................................27

5.2. Constantvolume/varyingpressurevs.Constantpressure/varyingvolume...........................28

5.3. Optimization.........................................................................................................................................................28

5.4. Profitability...........................................................................................................................................................29

5.5. Largescaleorsmallscale...............................................................................................................................30

5.6. Environmentalaspects.....................................................................................................................................30

5.7. Socialaspects.......................................................................................................................................................30

6. Conclusionsandrecommendations............................................................................31

7. References..........................................................................................................................32

8

1. INTRODUCTION

As global warming and climate change continue to increase and make themselves known not only by

their consequences but increased awareness, the interest for sustainable solutions grows rapidly. The

concept of "sustainable development" is a multifaceted term, used by many and in just as many contexts. Many definitions of sustainable development are derived from the Brundtland report, which states that to make development sustainable humans need to "ensure that it meets the needs of the present without compromising the ability of future generations to meet

their own needs" (UN, 1987) but this can be interpreted in many ways. While its vague definition is by

some deemed problematic, the general consensus is still that sustainable development is of the greatest importance for the future of the human race and needs to be a top priority (Kuhlman and

Farrington, 2010).

One of the most important drivers of development is energy, which is necessary for growth on both a

individual and global level (IPCC, 2016) and also part of the UN's sustainability goals (UN, 2016). In

many parts of the world there is an abundance of energy, as society has spent both time and resources in developing the techniques of harnessing energy from sources such as oil, coal and nuclear materials. With the growing climate changes it has been made obvious that the traditional

ways of energy production will no longer be able to sustain the world in ways that do not risk radically

changing the global ecosystem. Furthermore, the UN sustainability goals specify that energy should be

both clean and affordable, a criterion that is not fulfilled by the use of fossil fuels (Stockholm Resilience Centre, 2018). Renewable energies in many forms are being developed, but just as fossil

energies have a problem fulfilling the "clean" part of "clean and affordable energy", renewables have

a problem fulfilling the "affordable" part. Within this affordability spectrum falls the problematic fluctuating properties of many renewable energies as the main sources (such as sun, wind and waves)

are not constant in their supply but vary with time. A proposed solution to battle the fluctuation, and

thereby making renewables a more attractive and stable form of energy, is energy storage. Today, the practiced forms of electric energy storage are pumped hydroelectric storage, certain

battery technologies and compressed air as energy storage (Drury et al., 2011). While these solutions

all have the ability of supporting renewable energies in terms of balancing peak-demand and providing

back-up reserves, they all come with their respective set of problems. Although these solutions are already being commercially implemented to some extent, further development is required if they are

to be applied on a global scale. This report will focus on investigating the field of compressed air as

energy storage, commonly known as CAES. The concept of CAES is to compress air in period of excess energy, and later on expand it, releasing the energy back into the grid during periods of energy shortage. There already exists two functional CAES plants (Garvey and Pimm, 2016) which were constructed several decades ago, and as technology has since then developed, many aspects could be improved. In the process of compressing, storing and expanding the air the main emissions originate from the burning of fossil fuels to regulate temperatures, giving the environmental issues a more uniform solution by simply ensuring that the required energy comes from renewable sources. To promote an increased use of CAES, this report will instead focus on investigating the technical performance and

economic viability. Since large scale CAES plants already exist, the report will, in addition to providing a

detailed description of the technical process and how CAES is being used today, investigate the 9

possibility of implementing it on a smaller scale to give energy storage capacity to a group of smaller

buildings or one large building.

1.1. PURPOSE

Provide an overview of the technical aspects of the CAES process and analyze its viability as energy storage on a small scale.

1.2. OBJECTIVES

• Outline the full process, from compression to expansion, of CAES from a technical and engineering perspective. This includes key aspects such as efficiency, excess heat treatment and variations due to chosen storage type. • Investigate whether CAES is a feasible option for small scale energy storage to balance daily energy demand fluctuations and increase energy independence. • Evaluate CAES, from an environmental viewpoint, in relation to other energy storage options and identify its role in the development of renewable energies. 10

2. BACKGROUND

2.1. ELECTRICAL ENERGY STORAGE

The electric system is a complex configuration of power generating units, transmission and energy users creating supply and demand within the system. To keep the system stable, equilibrium has to

exist between supply and demand of electricity (Ibrahim et al., 2008). However, the electricity demand

is constantly changing, both from day to day and season to season, all depending on the users need

for heating, cooling, lighting etc. (Denholm et al., 2010). The integration of renewable energies with

variable and unpredictable energy output, such as wind and solar power, into the grid ads yet another

dimension of uncertainty making it even harder to maintain equilibrium (Ibrahim et al., 2008). The amount of electricity from renewable energy sources in the grid has increased which is an important step towards a more sustainable energy system and a way to lessen the overall dependence on fossil fuels and thereby also greenhouse gas emissions (Denholm et al., 2010, Salvini et al., 2017). To increase the chances of more integration, the unreliability of renewable energy sources must be

tackled to make it easier to integrate them into the grid. Electrical energy storage (EES) could be a

solution since it could be a way to regulate the electricity supply from renewables to meet the changing demand and thereby maintain equilibrium (Ibrahim et al., 2008). EES could also be a way to strengthen reliability of the existing power grid as well as boosting integration of renewables (Denholm et al., 2010).

2.1.1. EES IN THE ENERGY SYSTEM

The instability of variable renewable energies can be observed in deregulated electricity markets

where the electricity price can be highly volatile and change drastically during the day because of the

changes in energy output from renewable energies (Bullough et al., 2004). The price of electricity is

determined by a balance between demand for electricity and the supply (Nordpool, 2018b) and a variation of different power plants is used to meet the need for electricity where a baseload plant handles the constant demand (Denholm et al., 2010). To provide baseload power a technology where the output of power can be planned regardless of weather conditions have to be used and in Sweden it consists of hydropower and nuclear power (Byman, 2016). Baseload power plants are often used as much as possible and in some cases, e.g. nuclear power, there are restrictions preventing rapid changes in output power i.e. this type of power plants can produce a constant and reliable energy output but if the electricity demand spikes the output cannot be changed fast enough to meet that demand. Usually these plants have a large capital cost and low variable cost (fuel) which encourage constant usage. Consequently, other electricity production technologies have to be used for meeting

variations in load. These are called load-following plants, and some can be classified as intermediate

meaning they meet variations in load from day to day. Then there are ones that meet unforeseen peaks in demand, peaking units (Denholm et al., 2010). Since the electricity price is determined by supply and demand the off-peak electricity is cheaper. Electric energy storage solutions are a possible addition to the grid which may have potential to

improve the electricity system in a multiple of ways and they are a part of future sustainable energy

systems (Lund and Salgi, 2009). The improvements include contributing to meet the variation in

electricity demand since EES could be an alternative to better utilize baseload plant and reduce need

for plants operating with less efficiency. EES can provide load leveling effect, meaning it uses

electricity during off peak and storing it to later supply electricity during high peak hours. EES also has

11

the ability to provide backup in case of temporary loss of other electricity production. Intermittent

power generation from renewable resources and other variations in demand also cause frequency variations in the grid, meaning there is a need for frequency regulation which EES can provide byquotesdbs_dbs14.pdfusesText_20

[PDF] compressed air energy storage ppt

[PDF] compressed air energy storage working

[PDF] compressibility of distilled water and seawater

[PDF] compressor hp to tons

[PDF] comptabilité analytique de gestion cours

[PDF] comptabilité analytique de gestion cours pdf

[PDF] comptabilité générale s1

[PDF] comptabilité générale s1 examen

[PDF] comptabilité générale s1 examen corrigé

[PDF] comptabilité générale s1 karim economiste

[PDF] comptabilité générale s1 pdf karim economiste

[PDF] comptabilité udem

[PDF] compte ameli

[PDF] compte de résultat exemple

[PDF] compte rendu de formation doc