Smart Cities - Transition Engineering

Transition to 100% Renewables

Transition to 100% renewables using a percentage plot. This modelling was conducted for the USA.

Total Primary Energy Production

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)

Alinta says court wind farm ruling will have 'dramatic' and chilling effect on renewable energy investment ABC News 26 March 2022