Smart Cities - Transition Engineering
Climate Change
Since the industrial revolution started in the 1800s humanity has been steadily raising the level of carbon dioxide in the atmosphere. The level of carbon dioxide in the atmosphere is expressed in parts per million (ppm). At the start of the industrial revolution the level of carbon dioxide in the Earth's atmosphere was 290 ppm.
The info graphic shows the increase in carbon dioxide from the start of the industrial revolution up to the present.
- 100 Gt-C between 1800 - 1960 to reach 310 ppm
- 100 GT-C between 1960 - 1980 to reach 340 ppm
- 350 GT-C between 1980 - 2014 to reach 400 ppm
- 250 GT-C between 2014 - ?? to reach 500 ppm (2 degC global temperature warming)
The global temperature rise can be calculated based on the level of carbon dioxide and other Green House Gases in the atmosphere. The variability is associated with probability calculations. Since the risks associated with climate change are so high it is best to take a conservative approach and aim to keep carbon dioxide at the lowest value range.
- 425-785 ppm for 1.5 °C
- 489-1106 ppm for 2 °C.
- We are currently at 412.5 ppm in 2020.
To keep the global temperature at 1.5 degC the release of carbon dioxide needs to be limited to 100 GT-C from 2014 until 2050. The average amount of carbon dioxide release each year is approximately 10 GT-C per year. To keep within the 100 GT-C budget we would need to reduce carbon dioxide emissions by 10% per year. Climate Change Victoria estimates that the remaining budget is closer to 800 GTCO2-eq.
Transition to 100% Renewables
The world is steadily progressing to reduce the burning of fossil fuels and transition to 100% renewables. The transition to renewables can be modeled by engineers. Several assumptions are used in the model, such as how quickly to reduce fossil fuels, and how quickly renewable technology can be rolled out. In the model presented below the time period of interest is from 2020 to 2050 where the world transitions to between 80-100% renewables. This graph and other similar to it are widely used to demonstrate to the public and policy makers that transition is possible with current renewable energy technologies.
100% renewable energy scenario assumptions
- Fossil fuels reduced by 6.5% per year
- Coal power plants are decomissioned
- Oil and natural gas energy production plant outputs decline
- No new hydro
- Wind increases by 4% each year and levels off at 21% of energy mix
- Solar PV increases by 10% per year and then levels off. Panels need replacing after 30 years.
- No more biofuels
- Biomass energy increases to use as heating fuel
- Geothermal and landfill gas increases 10 fold.
Transition to 100% renewables using a percentage plot. This modelling was conducted for the USA.
Total Primary Energy Production
The graph above can also be presented as a plot of Total Primary Energy production. You can think of Total Primary Energy as the sum of all the energy used to run the global economy. The chart shows that in order to achieve 80% renewables the Total Primary Energy of the economy must decrease from today's levels (2020) by approximately half. What does this mean?
The same plot shown with Total Primary Energy production. To achieve 80% renewable energy supply by 2050 total primary energy production must decline. The level of total primary energy production is equivalent to levels in the 1950s and 1960s.
Energy Return on Investment EROI
The reason for this can be traced back to the Energy Return on Investment (EROI).
- An EROI of 20 means that for every 100 units of production, 5 units are used by the energy sector. Or, for 1 unit of energy invested, 20 units are returned
- An EROI of 2 means that for every 100 units of production, 50 units are used by the energy sector. Or, for 1 unit of energy invested, only 2 units are returned.
Once the EROI drops below 5 it means that society is investing huge resources in the energy sector but getting a low return on the investment.
Investment in PV solar has an EROI of 5 to 10. The addition of battery storage will lower the EROI because batteries require energy (and resources) to build, maintain and decommission, and they add energy losses to the system (e.g. 20% energy loss). We currently don't fully consider these factors because solar PV panels and manufactured off shore using fossil fuels (not accounted for) and we rely on a power grid base load supported by fossil fuels. When fossil fuel inputs are significantly reduced the low EROI will be more apparent.
We can make energy source regardless of the EROI. We can fill up our cars with BioEthanol, however if scaled up to the whole economy the economy would fail (Energy Profit Margin in Decline).
EROI comparisons
- Hydro = 35 to 50
- Thermal coal = 30 to 50
- Wind = 5 to 30
- Solar = 5 to 10
- BioEthanol = 1
- Intensive (industrial) agriculture = 0.1
Battery Storage
Example of EROI for Wind power with and without batteries. Using the batteries in an electric car would return an enen lower EROI.
Wind will also be more expensive to build (lower EROI) for the following reasons:
- noise complaints and forced shutdowns at night
- infrasturucture upgrades to the electricity grid
- expensive offshore installations
- rare earth metals used in constuction of electricity generators
- addition of expensive storage options
- Less usable energy than base load supplies (at scale)
Climate Change preparation
