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Modelling > Model design > Flashcards

Model design Flashcards

1
Q

Examples of model expressions:

A 
CAPEX
OPEX 
(P)EROI
Emissions - carbon footprint 
EcoPoints
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2
Q

Expand: CAPEX

A 
Capital expenditures (CAPEX) are a company's major, long-term expenses
Examples - buildings, equipment, machinery, and vehicles.
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3
Q

Expand: OPEX

A

Operating expenses are the costs a company incurs for running its day-to-day operations.
Examples: Wages, rent, taxes

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4
Q

(P)EROI

A

(Processed) Energy Returned or Invested
Energy Return on Investment (EROI) is a ratio for describing a measure of energy produced in relation to the energy used to create it.
The threshold between energy producer and energy sink is set at 1.

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5
Q

Temporal influences on overall sustainability

A

Energy demand, intermittent resources, decentralised load balancing

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6
Q

Factors influencing system sustainability

A

LCA characteristics
Temporal dynamics
Geographic diversity
Complexity

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7
Q

Relative patterns

A

% of maximum flow available at every interval between 0% and 100%
(cow manure either 100% available from stable or 0% available from the field)

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8
Q

Absolute pattern

A

Actual value per interval

wind speed, temperature which can be implemented into the calculation of the flow

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9
Q

Model Verification

A

Verification ensures that the computerised model made correctly
“did I create the model right”

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10
Q

Model Validation

A

Validation ensures that the model itself functions accurately for the specific purpose
“Did I create the right model?”

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11
Q

Acceptable range of accuracy

A

The accuracy required of the model for its intended purpose

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12
Q

The cost curve

A

As the cost increases, so does the confidence in model accuracy

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13
Q

Value curve

A

Value of the model increases to the user as the confidence of the model increases

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14
Q

The problem entity

A

The system idea, situation, policy or phenomena to be modelled

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15
Q

The conceptual model

A

The mathematical, logical, graphical representations of the problem entity

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16
Q

Computerised model

A

conceptual model implemented on the computer

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17
Q

How is the PE, and Concep and Comput models interlinked

A

conceptual developed through analysis and modelling
conputerised developed through programming and implementation
Inferenced about PE are obtained through experimentation on computerised models

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18
Q

Operation validity

A

The models output behaviour has a satisfactory range of accuracy for the intended purpose of the model

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19
Q

Data validity

A

ensuring necessary data for the model building, evaluation and testing are adequate and correct

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20
Q

Ground truth

A

A measure of validity..

Information that is known to be real or true.

A model is an approximation of reality - how far is it from the ground truth

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21
Q

What are the primary techniques required for model validation

A

Face validation, structured walk through, trace

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22
Q

What are the primary techniques used to determine correct programming

A

Structured walk through, trace `

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23
Q

How can an LCA be used by decision makers `

A

(RIMC)
Reduce negative impact of new product
Identify what can be improved in existing products
Modifying aspects which can cause more significant issues further in its lifetime
Comparing environmental performance of similar products

24
Q

Why is the expression of GWP in kgco2eq and not Kgco2?

A

Measuring the impact of emissions on the environment accounts for all greenhouse gases. Different gases will have different environmental impact - however they are summed up into a single score of GWP 100.

25
Q

What is EcoPoints?

A

A single unit measurement of obtained by a combination of factors of impact categories relating to environmental impacts.
3 impact categories - human health, ecosystems and resource depletion.

26
Q

Handling complexity with modelling

A

Modular approach
Consciousness of system boundaries
Budget
Time

27
Q

Components within a single sub-module

A 
Main variables 
Impact factors
Primary flows 
Direct flows 
Indirect flows 
Embodied flows
28
Q

What kind of information can you find in the primary data base

A

Physical properties of the materials used in primary flows. for example, material densities, heating values and molar mass.

29
Q

What data is found within the direct coefficient database

A

Here will be the values needed for calculating the direct flows - for example, the amount of electricity, heat, diesel required to conduct these processes

30
Q

What information can be found in the direct IMPACT coefficient data base

A

Data for calculating direct impact indictors such as the costs (CAPEX and OPEX) efficiency (P)EROI, Emissions (GWP) and environmental impacts (EcoPoints)

31
Q

What data is found within the indirect data base

A

specific coefficients relating to the processes needed for the direct material and energy flows - mainly used for calculating impact factors e.g. extraction, refining, transport and use of diesel

32
Q

What data is found in the embodied database

A

Impact factors relating to the installations required for the specific sub-module - costs, materials used, construction, energy for constructions and deconstruction (at end of life).
There are two main variables for embodied 1. the size/ power rating of the infrastructure 2. the lifetime of the infrastructure

33
Q

Questions to ask when verifying a model… Does/is the model

A

Add to scientific findings/ societal benefits
Provide clear answers
Reviewed and verified by experts

34
Q

Subjective testing

A

Testing through common reasoning by the modeler

Can be done using graphical display and review of model behaviour - also comparison to other models

35
Q

Objective testing

A

Using some kind of statistical/mathematic test e.g. hypothesis testing or confidence intervals.

36
Q

How can accuracy be measured

A

Factual aspects - compared with the ground truth

Conceptual aspects - opinion by experts

37
Q

What is the link between accuracy and development time

A

The goal is to retain the highest accuracy in the lowest time required

38
Q

% of accuracy for fact based comparisons

A

80%

however primary data accuracy should be in the range of 95%-99%.

39
Q

Why should you be mindful of the information on EcoPoints

A

The ReCiPe software is still evolving = possible uncertainties in the indicators

40
Q

Hypothesis testing

A

To determine whether the models outputs are in a satisfactory range for its intended purpose - means, distributions, variances and time series are tested under different scenarios.

41
Q

Confidence intervals

A

The shorter the lengths of the confidence intervals the more invalid the data is considered - they are the differences between the means, variances and distributions of different simulations and outputs from a set of experimental conditions.

42
Q

Types of graph for model comparison

A

Histograms
Box-plots
Behaviour charts

“output behaviour has sufficient accuracy for models intended purpose”

43
Q

Functional unit

A

Quantified performance of a product system for use as a reference unit in an LCA study

It is a single comparison unit of an LCA indicated in a measurable unit (MJ, Kg)

44
Q

Function of SIMAPRO

A

Science-based tool used to collect, analyse and monitor the sustainability performance data of your company’s product or service. Assessing the environmental impact across all life cycle stages

45
Q

Limitations of LCA

A

Defining the system boundary - spatial and temporal resolutions and capital goods analysis.
Not suitable for precautionary approach - catastrophes
Other system boundaries - socioeconomic, financial (subjective)
Specific data difficult to obtain
Time consuming`

46
Q

Advantages of LCA

A 
System reliability - well accepted 
Software/database availability
Includes multiple impact categories
Allows for comparison 
(also think how decisions makers/companies will use this information for the benefit of themselves and environment)
47
Q

LCA interpretation should include

A

Identification of significant issues as proposed in the problem entity
Evaluation of the study - completeness, sensitivity, and consistency
Drawn recommendations and conclusions and limitations

48
Q

Production chain

A

Analytical tool used to understand the nature of the production process.

49
Q

Other types of models

A

Predictive models - altering the variables to fit different scenarios to extrapolate potential future projections
Optimisation models - altering the data set to find out optimal outcomes for specific values (costs, efficiency).

50
Q

3 purposes for data collection

A

building conceptual model
validating the model
experimenting with the validated model

51
Q

Conceptual model validity

A

Ensuring the underlying theories and assumptions in relation to the problem entity are correct
The logical, mathematical and graphical assumptions are ‘reasonable’ for the intended purpose of the model

52
Q

Operational validity

A

Ensuring the model output behaviour has the accuracy required for the intended purpose of the model.

(this is where subjective and objective testing comes in)

53
Q

Why can model ‘correctness’ not be fully established

A

no algorithm exists to test model correctness

Every simulation project is new and unique so must be tailored made and verified throughout

54
Q

GWP

A

100 year global warming potential.
Comparable for fossil and renewable energy sources.
Many different GHG with their own potentials and properties.
carbon neutral, carbon releases and fossil fuels.

55
Q

What is the process of model design

A

Problem definition
• Conceptual model: Main expressions, Main variables, Equations
• Data collection: Literature, Measurements
• Actual model
• Validation

Modelling (2 decks)

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