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Literature Reviews in MEL

This section of the workshop considers the purposes, organization, and features of a successful literature review in Applied Science that students may well be expected to produce in the MEL program. For this section, we sample two LRs, the main one from a successful MEL student paper (which has been anonymized) and a second LR from a published paper, both studies being in Environmental Engineering. This workshop samples from the writing in these papers as they become necessary in the tasks below. 

Task 10: Examining an Exemplary Introduction from the CEEN 503 Term Paper

Read the excerpt from the end of the introduction section (before the literature review) of a term paper rated as “Exceptional”, written by a student in the Master of Engineering Leadership program, specifically in the Clean Energy Engineering stream and the course CEEN 503, Sustainable Energy Systems. For convenience and anonymity of the student writer, we’ll call this the CEEN report.

Please recall from the first part of this workshop about the three conventional purposes for reviewing literature. After reading the end of the introduction below, predict whether the report will review the literature for purpose 3

  1. To gain a broad understanding of the relevant research in a specific subfield.
  2. To analyze the research in a specific subfield for research topics and contributions.
  3. To highlight a specific gap, problem, or opportunity as a rationale and background for (proposing) a new study.

Paper Title: TECHNOLOGY FOR RETROFITTING NATURAL GAS POWER PLANTS IN ALBERTA

1. Introduction

[…]

Carbon capture and sequestration can be expected to play a key role in enabling Alberta to achieve a net zero electricity grid. Particularly if Alberta is to meet the 2035 net zero target, as the federal government has indicated will be required by legislation, retrofitting existing facilities with carbon capture technology will be necessary. This paper will review the carbon capture technologies commercially available and determine which are best suited to this application.

As can be appreciated, even before reading the literature review, the paper’s statement of purpose assumes a conventional general-to-specific order for reviewing studies of these technologies, starting with all those technologies that qualify (as was reviewed, this is based on the research criteria) , narrowing down to those that are most promising.

Task 11: Identifying the Knowledge Gap in Engineering Research from the Introduction Section

It was noted earlier that literature reviews often identify a research question, focus, or proposal based on an identified gap in knowledge. What is missing or needed in this field of engineering that this study seeks to address? Identify the sentence from the Introduction that best highlights the gap:

Task 12: Choosing the Most Likely Organizational Approach for the Initial Phase of the Literature Review

Recall the factors determining the organization of literature reviews:

General Factor in Determining LR Organization Example Studies
1. Classification of the research-based materials reviewed
  • Applied, empirical studies
  • Methodological studies
  • Professional training materials
  • Policy documents
  • Theoretical studies
2. Scope of perspective on the topic
  • Macro view
  • Midlevel view
  • Micro view
3. Positioning of research studies relative to (author’s) preferred approach
  • Aligned
  • Non-aligned
  • Neutral

Now read the references cited in the CEEN report’s initial review section, listed below in the order that the sources were reviewed. The kinds of sources referenced and their order suggest the particular way that this opening literature review was organized and even its role in the second phase of the literature review. (See * to identify the referenced organizations.)

AESO*, 2022. Understanding Electricity in Alberta. [Online] Available at: htps://www.aeso.ca/aeso/understanding-electricity-in-alberta/ [Accessed 10 July 2023].

AESO, 2023. 2022 Annual Market Statistics, Calgary: AESO.

IPIECA**, 2022. Combined Heat and Power (2022). [Online] Available at: htps://www.ipieca.org/resources/energy-efficiency-solutions/combined-heat-and-power2022#refs

Government of Canada, 2023. Emission Factors and Reference Values. [Online] Available at: htps://www.canada.ca/en/environment-climate-change/services/climate-change/pricingpollution-how-it-will-work/output-based-pricing-system/federal-greenhouse-gas-offset-system/emissionfactors-reference-values.html#table_1

Goverment of Canada, 2020. Provincial and Territorial Energy Profiles – Alberta. [Online] Available at: htps://www.cer-rec.gc.ca/en/data-analysis/energy-markets/provincial-territorial-energyprofiles/provincial-territorial-energy-profiles-alberta.html#s3

National Energy Technology Laboratory, n.d. POINT SOURCE CARBON CAPTURE FROM POWER GENERATION SOURCES. [Online] Available at: htps://netl.doe.gov/carbon-capture/power-generation [Accessed 6 July 2022].

Garcia, J. A., Villen-Guzman, M. & Rodriguez-Maroto, J. M., 2022. Technical analysis of CO2 capture pathways and technologies. Journal of Environmental Chemical Engineering, 10(5).

Raynal, L. et al., 2011. The DMX™ process: An original solution for lowering the cost of post-combution carbon capture,. Energy Procedia,, Volume 4, pp. 779-786.

* AESO (Alberta Electric System Operator) is the non-profit organization responsible for operating Alberta, Canada’s power grid.

** IPIECA (The International Petroleum Industry Environmental Conservation Association) is a global not-for-profit oil and gas industry association for environmental and social issues.

Select the description of the organization of this first phase of the literature review that you consider is most likely given the above reviewed studies and their order:

Task 13: The role of evaluation in narrowing the research focus

Below is the first literature review section of the CEEP report discussed in the previous task. For this task, we have identified the words and phrases that express the writers’ explicit evaluations, whether positive or negative. Read the first phase of the literature review and match the writers’ evaluative language with the entity that was evaluated:

Alberta’s Natural Gas Power System

In Alberta there are currently 53 natural gas fired power plants, with a total capacity of 10.5GW, including the plants under construction as discussed in section 1 (AESO, 2023). This includes co-generation plants located in oil and gas facilities that sell power to the grid when demand for process heat is low.

The first step in analyzing what technologies would be a good fit for each facility was to determine the CO2 emissions breakdown from each one. Using the nameplate capacity, Alberta Electrical System Operator (AESO) availability factor statistics for natural gas combined cycle plants (80%) and co-generation facilities (60%) in 2022 (AESO, 2023) and an average efficiency of 50% developed by IPIECA (IPIECA, 2022), the annual natural gas usage for each plant was estimated. Statistics Canada CO2 emissions factors were then used to calculate the emission rates from each facility. An emission factor of 1962 gCO2 /m3 for marketable natural gas was used for dedicated power facilities, while 2109 gCO2 /m3 for unmarketable gas was used for the co-generation facilities (Government of Canada, 2023). This was selected as the cogeneration facilities are commonly located at gas plants, or other oil and gas facilities, where nonpipeline spec gas may be used, at the discretion of each company.

Using this estimating method, the total emissions add up to 27MT per year. Compared to the published value of 29.3 MT CO2 e (Goverment of Canada, 2020) for the year 2020, this was deemed an acceptable estimate. It was expected that the calculated value would be less than the actual since the calculated value does not consider other greenhouse gases such as NOx and other contaminants, which are included in the published CO2 -equivalent value.

A summary of the results is shown in Figure 1 [not shown in workshop version]. The full plant data and calculation sheet is included in Appendix A. It can be seen in figure 1 that there is a bi-modal distribution of emissions. There are many smaller facilities with less than 0.4Mtpa CO2 and nine large facilities with emissions greater than 1Mtpa. This is an important finding, as the technology required for the large facilities may be different than those available for the small facilities. Many technologies have been piloted on the same scale as the small facilities. This means that the application of technology readiness level (TRL) 6-8 technologies will carry less risk when used in the small plants. Given the size and relative importance of the larger facilities, only TRL 9 technologies should be considered for retrofits in the immediate future.

For either case, a key factor in the evaluation of these technologies was ensuring that they could remove carbon dioxide from flue gas with a low of CO2 concentration of 5%, which is typical for natural gas combustion in air (National Energy Technology Laboratory, n.d.). Alternatively, technologies which raise the CO2 concentration to a level which enables faster, and cheaper CO2 capture were also considered.

Technology Review

Post Combustion Capture: Chemical Absorption

The main area of continued advancement for this technology is the development of state-of-the-art solvents. Many companies are developing, or have developed, solvents which are capable of outperforming MEA. The criteria which are used to evaluate the new solvents are (Garcia, et al., 2022; Raynal, et al., 2011):

  1. Little or no additional capital cost, compared to the MEA process. This is accomplished by ensuring fast reaction kinetics, high CO2 selectivity and low degradation from impurities and regeneration-reuse cycles. 2.
  2. Energy penalty less than what is needed for regeneration of MEA (3.6MJ per ton CO2 captured).

Task 14: The rate of explicit evaluations across the literature review

In this literature review, the rate of evaluation changes as the review progresses. What is the pattern?

Task 15: Analyzing the Organization of Studies in the Second Phase of the CEEN Report’s Literature Review

We have so far only covered the first half of the literature reviewed in the CEEN report. The second phase of the literature review in this paper is not unusual but it does support the finding in the literature review of literature reviews by Swales & Lindemann (2002) that this sub-genre of academic writing varies considerably.

The second phase of the LR begins with the criteria set up for comparing new solvents and summarizes the individual studies (in bold) of these new solvents in a table. Read this part of the review and identify how these specific studies are organized in the table:

The criteria which are used to evaluate the new solvents are (Garcia, et al., 2022; Raynal, et al., 2011):

  1. Little or no additional capital cost, compared to the MEA process. This is accomplished by ensuring fast reaction kinetics, high CO2 selectivity and low degradation from impurities and regeneration-reuse cycles.
  2. Energy penalty less than what is needed for regeneration of MEA (3.6MJ per ton CO2 captured).

New solvents which are now commercially available are summarized in Tables 1 and 2.

Table 1. Advantages and Disadvantages of Various Solvents

Solvent Advantages Disadvantages
Aqueous Ammonia (Godin, et al., 2021)
  • Can capture other contaminants, such as SOx and NOx , reducing pretreating requirements.
  • Higher CO2 absorption than amines.
  • Lower energy penalty for regeneration (compared to amine).
  • Low corrosivity. Carbon steel construction materials can be used.
  • Slow absorption reaction kinetics – requires longer residence time and larger equipment.
  • Higher capital cost
  • Ammonia toxicity causes HSE risk for operations staff.
Chilled Methanol (Garcia, et al., 2022)
  • Resistant to degradation from high temperature and contaminants reducing pretreating requirements.
  • Lower energy penalty than amines. Can be regenerated using pressure swing separation rather than temperature swing.
  • Low corrosivity. Carbon steel construction materials can be used.
  • Refrigeration equipment adds cost unless existing refrigeration has excess capacity (e.g. LNG facilities).
  • Absorbs traces of mercury if present. Over time mercury levels build up in solvent.
Secondary and Tertiary Amines (Garcia, et al., 2022), (Puxty, et al., 2009)
  • Mature technology
  • Many have higher CO2 absorption rates than MEA.
  • May be designed to use air stripping, with no external heat, resulting in low energy penalty.
  • Can be substituted for MEA to increase capacity of existing units
  • Required compression can be an advantage if there is no throttling before sequestration.
  • Air stripping adds to the volume of gas being sequestered or downstream separation requirements.
  • Requires flue gas dehydration before CO2 removal.
  • Higher absorption efficiency at high pressure – requires inlet compression.
Dual Amines in Aqueous solution (DMX Process) (Raynal, et al., 2011)
  • High CO2 absorptivity and selectivity
  • Lower flowrates through stripper result in lower energy penalty of 2.1 – 2.3 GJ/ton of CO2
  • Low degradation in lab scale tests, compared to MEA.
  • Very low corrosion rates – allows for the use of carbon steel materials
  • Added equipment for separation of liquid phases, rather than more minor modifications to existing process as with others on this list.
  • Industrial scale degradation is difficult to simulate in a lab experiment. This represents risk for implementation

Task 16: Ordering Information within paragraphs and sentences

Tasks 10-15 present the benefits of preparing an outline for your report’s Introduction and literature review by considering the nature of topics covered and materials reviewed, the scope between macro and micro perspectives, and how the topics and materials evaluated.

The pattern of organization we’ve observed aligns within the Create A Research Space (CARS) model for research article introductions, which comprise three stages, the first two involving the LR and the third introducing the purposes and nature of the study typically motived by the ‘gap’ identified in stage 2:

The CARS Model for Research Article Introductions (Swales, 1990)
Stage 1: Establishing a research territory
Claiming the centrality and significance of the field
Making topic generalizations
Reviewing previous research & related references
Stage 2: Establishing a research niche
Indicating a gap in research
Counter-claiming
Question raising
Stage 3: Occupying a research niche by
Outlining purposes of new research
Announcing present research
Announcing principle methods and findings

The CARS model for writing research paper introductions illustrates a general pattern in academic communications, which tends to favour a general-to-specific order and a move from established knowledge to new knowledge. The present task examines similar patterns in information ordering at smaller scales, in paragraphs and sentences.

Below are two paragraphs from a literature review in a published chemical engineering paper on carbon capture (Björklund, Weidemann, and Jansson., 2023*). The two paragraphs contain about the same information but the paragraphs differ in other aspects. Read them both to identify which of the two is easier to read in the sense of the flow of ideas.

* Emission of Per- and Polyfluoroalkyl Substances from a Waste-to-Energy Plant─Occurrence in Ashes, Treated Process Water, and First Observation in Flue Gas Sofie Björklund, Eva Weidemann, and Stina Jansson. Environmental Science & Technology 2023 57 (27), 10089-10095 DOI: 10.1021/acs.est.2c08960

Task 16 Feedback (Please complete the task first before proceeding)

Experienced readers will almost certainly prefer the first version of this paragraph over the second even though they contain the same ideas and claims. In Paragraph 1, each new sentences flows from the previous sentence, facilitating the reader’s cohesive understanding and interpretation of the paragraph. Why is this? How does the flow of ideas actually work in writing?

To answer these questions, we need to decompose the version of the paragraph that flows well into sentences, and examining how each sentence begins, which we shall call its DEPARTURE, and ends, which we shall call its DESTINATION. The basic function of language in representing the world and experience is expressed in the structure of the sentence. In sentences, meaning flows from the point of departure to its destination. Accordingly, how we order information matters to the achievement of flow between the departure and destination. The question becomes “what kind of information is best suited to sentence departures and what kind for sentence destinations, respectively?”

Given we use language and writing to exchange new ideas, it’s easy to point out that destinations – ends of sentences – are expected to include information that we expect will be new to the reader. As for the point of departure of the sentence, that should be information that is already known or expected to be known by the target reader. In this way, the ideal order of information in sentences involves starting with information that is known or expected to be known by the reader, establishing this information as a shared point of departure between writer and reader, with the remainder of the sentence involving new information. In this way, all new information is based on a foundation of shared information.

In the Table 1 below, we have divided the eight sentences in the extract into sentence departures – which include the first content elements of the sentence – and destinations, which begin with the first main verb phrase of the sentence. If our above theoretical proposal about information order is true, then the departures should contain information that is known or recognized by the target reader while the remainder should contain information that has not been previously mentioned. The analysis shown below bears this out. Note especially that well-written departures will contain information that readers reasonably recognize from their background knowledge or information that was recently presented in the destinations, that is, recently new information that is now known. In the latter case, reference words like “This” or “such” often remind the reader that the information links to a previous sentence (although not in this example). This common pattern of information transfer is called the zigzag pattern.

Table 1: Building Flow in Writing using the ZigZag Pattern

In Version 2 of the same paragraph above, we disrupted the flow of information by repeatedly

  1. Including new or unexpected information in the departure position (which should contain shared information) while
  2. Ending sentences (which should contain new information) with information that the reader already knows. These two practices, as illustrated in the second version above, must be avoided.

To summarize the strategies for organizing literature reviews that have emerged across the workshop so far, we note the need to lead into a literature review with an introduction involving a general perspective on the topic and sub-field, which are evaluated as significant and worthy of attention. The overall structure of the LR reflects careful planning of the type and scope of the studies and other references reviewed, generally moving towards increasingly specific topic foci. The LR often closes with by identifying a gaps in the research or an opportunity, which typically leads immediately into the aims of a new study or research proposal.

In the body of the literature review, we’ve observed the importance of lead or topic sentences of the paragraphs in previewing the topic and the direction at each stage of the literature review. Focusing in on the flow of information in paragraphs, we’ve noted that sentences should build on each other by beginning with information known or recognized by the target readers and ending with information that for them will be new. It’s worth noting, too, that strategies such as general-to-specific information order across a text, and the known-new information order of sentences are generalizable to most kinds of academic writing.

 

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