One Potential Transition to 100% Renewable Energy (Technical Perspective)

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This video describes one option for existing energy systems to transform from fossil fuels to 100% renewable energy. This is a pedagogical video so I have tried to include enough detail to explain how the design of our Smart Energy System has evolved, but avoid too much detail to ensure it is still understandable. Therefore, some of the details have been overlooked for communication of the main principals. The 7 steps defined in this video are as follows:

1. Replacing fossil fuels with bioenergy such as coal with biomass, natural gas with biogas or gasified biomass, and oil with biofuels. However, there will not be enough bioenergy to cover all of our energy needs so other measures are necessary.

2. Reduce our demand for energy by making our buildings more efficient i.e. ~30-50% less heat, making our electronics more efficient i.e. ~10-15% less electricity, and our transport more efficient, although transport will likely still increase due to the current growth in demand.

3. Connect the electricity and heat sectors to one another using district heating. This enables us to
i. use the surplus heat from power plants instead of wasting it in the sea or rivers, thus making the system more efficiency and
ii. to use new sources of renewable and surplus heat such as solar thermal, geothermal, and surplus heat from industry.

I forgot to number the next step in the video, but next we introduce new sources of renewable electricity, primarily in the form of wind and solar power. These new sources are cheaper and more sustainable than using bioenergy, but they have one significant drawback: they are intermittent. Therefore, we need to have suitable technologies in place so we can keep the lights on even when the wind is not blowing or the sun is not shining. At this stage, with the technologies we have in place, only ~10% of our electricity can be provided by wind and solar power due to this limitation, so the following steps need to help increase this limit.

4. To begin, we add some thermal storage to the district heating system. This allows our CHP plants to operate in a more flexible way so that we can now integrate ~20% wind or solar power onto our electricity system. Thermal storage is a simple and well-know technology which costs ~50 times less than electricity storage.

5. Next, we add both large-scale heat pumps to the district heating system and individual heat pumps to the buildings to replace boilers. This connects the electricity system to very cheap and large-scale thermal storage, thus increasing the flexibility. Now we can provide ~40% of the electricity demand with wind or solar power, including the new electricity required for the heat pumps. Some indivdiual bioenergy boilers may still be used in niche areas, but the majority of buildings in rural areas now have heat pumps, while in the cities we have district heating.

6. Now that the electricity and heat sectors are heavily interconnected, we can start to find some sources of additional flexibility in the transport sector. To begin we introduce electric cars, EVs, which are expected to replace 70-80% of conventional cars in the future. We can now
i. replace oil or biofuel in combustion engines and
ii. use the batteries in the vehicles to add more wind or solar power. This means that ~60% of our electricity demand can now come from wind or solar.

7. Finally, the last major challenge is replacing fuel in the heavy-duty transport. To do this we use synthetic fuels. A synthetic fuel is a hydrocarbon, like oil and gas, that is created by combining hydrogen and carbon. Hydrogen can be produced from electricity using electrolysis, while carbon can be obtained from many sources such as the power plant exhausts, bioenergy, industrial processes or the air. We recommend the production of methanol or dimethyl either as the synthetic fuel for remaining cars, trucks and ships. Now we have connected electricity production to heavy duty transport, but more importantly we have connected the intermittent electricity supply, i.e. wind and solar, to fuel storage. Fuel storage is very large and very flexible so now we can supply ~80% of our electricity needs from wind and solar power.

To conclude, we estimate that we now have an energy system that is:
i. 100% renewable
ii. Does not over rely on our bioenergy resource
iii. Will not significantly increase the cost of energy compared to a fossil fuel system: we estimate an increase of up to approximately 10-15% when you go as far as 100% renewable energy.
iv. Will create a lot more local jobs for countries that currently import fossil fuels

You can read more about our research at my research group's website, www.EnergyPLAN.eu, or my own website www.dconnolly.net. This video was made possible due to funding from The Danish Council for Strategic Research under the 4DH (http://4dh.dk/) and CEESA projects (http://www.ceesa.plan.aau.dk/).
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