index Expo Renew Nonrenew 2source Slowren Factors Recycle Daypr

## Growth on Two Sources

#### Description:

A system of this type uses two energy sources, one renewable, the other nonrenewable. When the nonrenewable source is used up, the growth declines back to a steady state based on the renewable source.

#### Examples:

• A population of microbes which decompose a pile of leaves and the leaves falling from the trees.
• The world economy growing up on both fossil fuels and renewable sources.
• #### Variables:

N = nonrenewable energy source
J = steady inflow of energy
Q = stored biomass
K*JR*Q = part of J that goes into the system
K3 = increasing factor of Q
K7 = increasing factor of Q
K8 = decreasing factor of Q

#### Equations:

DN = -K4*N*Q
JR = J/(1 + K*Q)
DQ = K7*N*Q + K3*JR*Q - K8*Q

#### Simulation:

The graph shows the changes of N (red) and Q (green) over a time period.
Source code: Twosource.java

#### "What if" Experiments:

Think about the renewable and nonrenewable sources of our economy:

• If we find more fuels (N), will our industrial society peak higher or last longer?
• If pollution increases giving us less available clear sun and rain (J), how will this affect the growth and future of the economy?