Industrial energy use is dealt with in the ZeroCarbonBritain model at a high level and a cautious approach is taken. Industrial energy demand is based on 2007 levels adjusted for 2030 population (1.15x) and a 25% reduction in energy intensity. This results in an industrial energy demand of 287 TWh, 12% higher than the actual industrial energy demand in 2017. Losses from synthetic fuel production is treated separately.
It is part of the scenario noted for further development. The following is my attempt at exploring the manufacturing energy required to build key elements of the renewable energy supply infrastructure: Offshore wind, Onshore wind and Solar PV. We can get an initial indication from this of the proportion of the total industrial energy demand that would relate to the manufacture of these technologies.
A Vestas V90 3.0 MW turbine sited in good location can achieve a capacity factor of 54.16%, generating 14,230 MWh/year (Horns Reef in Denmark). The LCA study gives the embodied energy per turbine as 8,098 MWh, which means the energy payback happens in 0.57 years or 6.8 months. The embodied energy per GW/MW/kW installed is therefore 2700 GWh/MWh/kWh respectively. The LCA suggests turbine lifetimes of between 20 & 30 years is possible.
The ZeroCarbonBritain scenario includes 140 GW of offshore wind capacity. At 2700 GWh per GW this would require 378,000 GWh of energy to build - or if expended evenly over a fleet lifetime of 25 years with a portion in continuous replacement: 15,120 GWh/year. This is equivalent to 5.3% of ZeroCarbonBritain's projected industry energy demand of 287 TWh/year.
ZeroCarbonBritain projects a rapid build out of zero carbon supply capacity. If 140 GW of offshore wind where built over a 10 year period, the energy demand for turbine production would be equivalent to 13.2% of ZCB industrial demand.
Key materials
1. Vestas LCA: V90-3.0 MW 2006
A Vestas V90 3.0 MW turbine sited in good location can achieve a capacity factor of 30%, generating 7,890 MWh/year (realistic site placement in Denmark). The LCA study gives the embodied energy per turbine as 4,304 MWh, which means the energy payback happens in 0.55 years or 6.6 months. The embodied energy per GW/MW/kW installed is therefore 1435 GWh/MWh/kWh respectively. The LCA suggests turbine lifetimes of between 20 & 30 years is possible.
The ZeroCarbonBritain scenario includes 30 GW of onshore wind capacity. At 1435 GWh per GW this would require 43,050 GWh of energy to build - or if expended evenly over a fleet lifetime of 25 years with a portion in continuous replacement: 1,722 GWh/year. This is equivalent to 0.6% of ZeroCarbonBritain's projected industry energy demand.
Key materials
1. Vestas LCA: V90-3.0 MW 2006
2. Vestas LCA: V82-1.65 MW turbines 2007
3. Vestas LCA: V110-2.0 MW turbine 2015
Page 35 of the Fraunhofer Solar PV report includes a chart showing the Energy Pay-Back Time of Rooftop PV Systems including mounting and inverters located in Germany. EPBT time varies from ~1.2 years for CdTe technology to 3.4 years for Mono-Si. The EPBT has improved over time due to increased manufacturing efficiency so we might expect the average EPBT to improve further.
It is also worth noting that EPBT is the primary energy equivalent payback and is currently calculated based on LCA's with energy systems that inculde a mix of thermal generation. A solar PV panel manufactured on a zero carbon renewable energy supply including mining and basic material processing would likely impact on this calculation. As an example the 2015 IEA-PVPS report suggests that the EPBT for single-crystalline silicon could reduce from 2.4 years today to 1.2 in future (page 8) [6].
In the ZeroCarbonBritain scenario 1 kWp of Solar PV generates about 840 kWh/year. If the EPBT is 2.0 the embodied energy would be about 1680 kWh/kWp (non-primary?). It's not that clear what the electricity and synth fuel requirements would be per kWp of solar PV production in a ZeroCarbonBritain like scenario, more research required.
The ZeroCarbonBritain scenario includes 90 GW of solar PV capacity. At 1680 GWh per GW this would require 151,200 GWh of energy to manufacture - or if expended evenly over a lifetime of 30 years with a portion in continuous replacement: 5,040 GWh/year. This is equivalent to 1.8% of ZeroCarbonBritain's projected industry energy demand.
1. Fraunhofer Solar PV report
2. Solar-PV energy payback and net energy: Meta-assessment of study quality, reproducibility, and results harmonization
3. An Exploration of Divergence in EPBT and EROI for Solar Photovoltaics
4. Review on life cycle assessment of energy payback and greenhouse gas emission of solar photovoltaic systems 2013
5. Energy payback time and carbon footprint of commercial photovoltaic systems
6. Life Cycle Assessment of Future Photovoltaic Electricity Production from Residential-scale Systems Operated in Europe
Wave, Tidal, Hydro, Geothermal & Solar thermal add up to a combined capacity of 48 GW. If we assume an midway embodied energy between Offshore wind, Onshore and Solar of ~2000 GWh/GW as a rough starting point this suggests 96 TWh. If these technologies are replaced on a 20 year timescale this would result in 4.8 TWh/yr of industrial demand.
The combined total of all the above technologies is 26.6 TWh/yr or 9.3% of industrial demand. These technologies produce 797 TWh/yr of energy and so provide a steady state annual EROEI of ~30x. If the excess electricity is not included (it may be exported or curtailed) this EROEI would fall to 24x.
The paper 'Hydrogen or batteries for grid storage? A net energy analysis' gives the electrical embodied energy of lithium ion batteries to be 136 kWh per kWh. The paper also quotes a cycle life of 6000 cycles at 80% DOD which seems a bit optimistic.. but also does not specify degradation extent e.g x number of cycles to 70% capacity.
The paper 'The Underestimated Potential of Battery Electric Vehicles to Reduce Emissions' by Auke Hoekstra suggests that the GHG emissions of lithium ion battery production is 65 kg GHG per kWh of battery produced and quotes 1500 to 3000 cycles as the expected cycle life to 80% of original capacity today. He also notes that cycle life is expected to increases to between 5,000 and more than 10,000 by 2030.
The ZCB scenario suggests between 50 and 200 GWh of stationary storage which would therefore require between 6.8 TWh and 27.2 TWh to produce. If these last 10 years this would be between 0.7 TWh/yr (0.2%) and 2.7 TWh/yr (0.9%).
1. Hydrogen or batteries for grid storage? A net energy analysis 2015
2. Electric vehicle life cycle analysis and raw material availability 2017
3. The Underestimated Potential of Battery Electric Vehicles to Reduce Emissions
4. GHG Emissions from the Production of Lithium-Ion Batteries for Electric Vehicles in China
378 kWh primary per kW of fuel cell. The paper estimates the electrical energy equivalent embodied energy as 378 kWh x 30% = 114 kWh per kW. The paper states that this assumption necessarily introduces significant uncertainty and they therefore examine a wide range in their sensitivity analysis.
The ZCB scenario includes 25 GW of hydrogen electrolysis. At 114 GWh/GW this would require 2.85 TWh to manufacture or 9.5 TWh at the primary energy value. If these last 10 years this would be between 0.3 TWh/yr (0.1%) and 0.95 TWh/yr (0.3%).
1. Hydrogen or batteries for grid storage? A net energy analysis 2015
The ZeroCarbonBritain scenario includes provision for 15 million 30 kWh electric cars & vans (1 for every 2 households). This is under half the number of cars registered on our roads today - but given that annual new car registrations in the UK is around 2.3 million/year would require EV sales to rise to 100% or more of all present day car sales within a very sort time if we are to reach 15 million electric cars by 2030 in addition to a significant retirement program and build up of alternatives. Car sales would then fall to ~0.76m/year.
ZCB scenario suggests 306bn passenger miles/year by EV in 2030. The average occupancy is 2 people per car and so the total vehicle miles is 153bn miles/year. A 30 kWh battery lasting 2000 cycles [3] should provide ~ 200k miles before loosing 20% of capacity. 153bn / 200k = 765 thousand cars manufactured per year at steady state x 30 kWh batteries x 136 kWh per kWh of battery [1] = 3.1 TWh/year industrial demand (1% of ZCB industrial demand). It's likely that battery capacities will be larger than this but this should also mean they last proportionally longer - as well as the potential for use in second life stationary storage applications.
In addition to the battery a Nissan Leaf sized EV will also include: 796kg steel, 24kg cast iron, 12kg wrought aluminium, 66 kg cast aluminium, 56.4 kg copper/brass, 0.2kg magnesium, 42kg glass, 145 kg plastic, 19.2 kg rubber and 36kg of other. (Source Updated_Vehicle_Specifications_in_GREET2.pdf).
In 'Sustainable Materials without the hot air' an example is given of steel car door production at 700MJ for 12 kg of door which works out to 16.2 kwh/kg, if the door is representative of the embodied energy in the rest of the steel body the embodied energy is 12.9 MWh per 796kg car body. A large part of the energy intensity here assumes that 60% of the steel used for steel door frame manufacture is lost as fabrication scrap, cutting out the door panel shapes from steel sheet. Reducing the yield loss would therefore have a significant effect on reducing this embodied energy figure.
The paper Yield Improvement Opportunities for Manufacturing Automotive Sheet Metal Components by Philippa M. Horton et al suggests that the average yield loss may be less than the car door example at 44%. This would reduce the embodied energy per kg to 11.6 kWh/kg or 9.2 MWh per 796kg steel car body.
At 11.6 kWh/kg the steel car body would add another ~7.1 TWh of industrial demand per year (2.5% of ZCB industrial demand).
If the balance of the remaining materials (~400 kg) where at a similar intensity they would add 4.6 MWh. The total embodied energy of the car would be ~18 MWh including the battery (this is a little lower than other embodied energy estimates in the 20-30 MWh range so is worth double checking). Multiplying this by 765 thousand cars would result in 14 TWh/yr of industrial demand or 4.8% of total ZCB industrial demand.
One important issue with this calculation is that it uses a steel process chain that uses fossil fuels rather than zero carbon alternatives such as steel production via hydrogen reduction and electric arc furnaces. A full LCA based on a zero carbon supply chain is required rather than one that uses today's industrial system.