Stocks and Flows

The stock and flow model is a simple but powerful model with broad relevance. Anything with inputs and outputs and an overall level is appropriate. The carbon dioxide in the atmosphere and the amount of money in a bank account are good examples.

Stocks and flows

• Bath tub model

• Steady state

• Residence time

Future activities

• Carbon dioxide concentration in ETC

• California drought

Bath tub model

• Flow in

• Flow out

• Level of water in the tub

Atmospheric CO2 Bathtub Model

Steady State

• Level in bathtub is steady

Brainstorm

• What things could be modeled with this

Residence time

• How long does something remain in the bath tub?

Adding rates

• What happens with two faucets?

Carbon dioxide Activity

• Estimate persons in the room with carbon dioxide?

• Draw stock and flow of room

• List relevant quantities

• Create estimates for the relevant quantities

• Synthesize estimates to create overall estimate

Learning Objectives

• Able to use stock and flow models to make estimates

Question

• Based on carbon dioxide measurements, what is our estimate of the

  number of persons in the ETC?

Review the Method

• State question

• Plan of attack

• Break down

• Synthesize

Review people calculation

• Carbon dioxide people calculation

• We started with a question, how many people given a carbon dioxide

  measurement

• We decided on a model to look at this

• We asked what smaller problems we could solve to take on the larger

  problem

• We tried to solve each of these smaller pieces

• We then synthesized everything

Review notes

• Chalkboard review

Using modern computation tools

We were off

• What did we miss?

• Fresh air entering through windows?

• Breath estimates?

• Air mixing?

California Drought

• What questions can we ask about the drought?

• Which of these questions can use a box model?

Water sankey diagram

LLNL Water Flows CA

Board Notes

Board Notes

Board Notes

Board Notes

Board Notes

Board Notes