The e-book ‘Climate Change for Astronomers’ led by Dr. Travis Rector addresses how astronomers can communicate and educate others on the science of climate change. The purpose of the book and the first chapter is summarised here. For this bite, I summarise the second half of Chapter 7, written by astronomers Dr. Travis Rector and Dr. Ka Chun Yu.
While existing energy sources along with biomass energy, nuclear fission power, hydro-electric, geothermal, and hydrogen energy storage were discussed in this bite (the first half), this section of the chapter discusses the energy sources we could potentially rely on in the future. It is necessary to consider additional alternatives to present day options for renewables (such as solar, wind) and non-renewable energy sources (such as fossil fuels), because having a broad range of options available will allow us to deal with the pros and cons of various energy sources. It will be unrealistic to completely replace coal with a single source of renewable energy. Some sources may not be feasible options or financially viable in particular environments and regions, and it is important to understand why this is the case. However, we can work to redesign energy infrastructure that combines the power of many different energy sources in a clever way. This bite will cover the possibility of using ocean power, nuclear fusion power and their pros and cons. Apart from this we can consider the possibility of carbon capture (to reduce emissions), smart methods of storing energy, and approaches to making our energy usage more efficient by modifying our energy infrastructure.
Future and alternative solutions
Ocean power (renewable energy)
Nuclear fusion energy
Carbon Capture
Negative Emissions Technologies
Energy Storage in batteries
Alternative energy storage options
Reduced emissions by increased energy efficiency
Ocean power is an approach in which energy is captured from the ocean’s waves and movements. It can involve placing a device at the surface of the ocean, such as a tidal turbine – these are analogous to wind turbines but operate underwater. Alternatively, there are various kinds of wave energy converters.
Pros: Ocean tides are generally quite predictable; some wave energy converters that rely on ocean waves are somewhat weather dependent (since wind creates waves), but less so than wind turbines. Furthermore, during operation, no emissions are produced from these devices. Unlike wind turbines, they don’t create much noise or impact views.
Cons: There is a high cost associated with the maintenance of these devices due to corrosion from water. The presence of these devices may also have impacts on marine environments that need to be considered. Ocean power may be readily available to cities close to the ocean (which most cities are), however they are only suitable when strong tides are present.
How solutions we implement may need to vary by sector
In considering the residential sector, it is possible that many home appliances can be switched to electric (e.g. switching stoves that use gas to induction stoves). Most of the energy used in the residential sector is for heating, air conditioning and ventilation. Heat pumps (which are completely electrical devices), can replace conventional furnaces to completely electrify these needs (which is greener if the electricity is produced from a renewable source). The commercial sector has similar issues (and thus solutions). However, there is also the opportunity to identify areas for improvement in terms of energy efficiency by installing energy management systems to track and manage energy in large buildings, which was mentioned in the previous section.
The industrial and transportation sectors will be much harder to decarbonize. In the industrial sector, most emissions come from the production of cement and the production of steel (accounting for 8% of global emissions). This is because the process heating used to produce steel (and cement) is highly energy intensive. Adding CO2 to concrete can actually help reduce emission as well as make the material itself stronger. Further, hydrogen combustion can be used in process heating to replace fossil fuels (e.g. to make ‘green steel’), but it is more costly. It also requires us to ensure the hydrogen is not produced from fossil fuels in the first place, but is produced using renewable approaches.
Finally, the transportation sector is most reliant on fossil fuels, but there are potential solutions for reducing emissions. Regarding automobiles, there has been growth in the use of electric vehicles (EVs), which are in some ways more energy efficient than internal combustion engine (ICE) vehicles. EVs don’t lose energy while they are idle, and even convert some kinetic energy back to potential energy from ‘regenerative braking’. Over their lifetime, EVs have ~⅓ of the emissions of an ICE – this calculation includes emissions from charging the vehicle (due to the average mix of electricity produced in the US market), and emissions released in the process of manufacturing it. On the downside, range can be an issue for EVs, since more planning is needed for travelling long distances (it takes more time to charge an EV than to fuel up an ICE). On top of that, the battery of the EV can lose capacity over time, although the batteries typically don’t need to be replaced in the lifetime of the vehicle. EVs are more expensive to purchase currently, even if money is saved over the lifetime of owning it, compared to an ICE. It is possible we could consider hydrogen combustion for automobiles, but existing engines can’t easily be modified, and hydrogen is more expensive than electricity or fuel if produced from renewables. It is also hard to find somewhere to refuel with since it is more difficult to store hydrogen.
Aside from burning fossil fuels, aircraft release soot and aerosols at high altitudes that form cirrus clouds and contribute to warming via radiative forcing. It will be difficult to replace fuel in aircrafts with hydrogen combustion because fuel is much easier to store (it can be stored in the wings) and has a higher specific energy (energy per unit mass). One can consider batteries, but they also have a much lower specific energy than fossil fuels. Batteries also do not ‘burn off’ and this limits the distances aircraft can fly. However, using electric aircraft may allow the regional air travel market to grow due to the lower maintenance costs of electric aircraft. There is also some possibility to have hydrogen combustion aircraft, which will partially reduce emissions, but will still face some issues related to storage of the hydrogen, radiative forcing and energy capacity of the hydrogen per unit volume. However, there is some work being done to replace current aircraft fuels with more sustainable fuel options (such as biofuels).
Some final points to consider
It is possible various solutions can be combined to reduce fossil fuel emissions. For example, solar and wind are promising, but solar power generates more energy during the day, so the use of batteries for storage (or perhaps methods like pumped hydro) allow us to use the excess energy later, when the output from solar power is lower at nighttime. We could also possibly mix solar and wind power with methods like geothermal or hydroelectric energy as a baseload (these methods were discussed in the previous bite if you need to recall them). Creative solutions can allow us to deal with the disadvantages of individual approaches.
We can consider switching to decentralized energy grids, or just ‘smarter’ grids. For example, High Voltage Direct Current (HVDC) reduces the loss of energy over long distances, compared to using standard AC. Having smaller producers of energy in local regions may also allow some more flexibility; for example, due to varying weather in different regions it may warrant dispatching different energy sources in different areas. It may be possible to even have energy distributed on the scale of individual homes (think solar power and also storage in batteries), or operators in localised regions may distribute energy according to the local environment to optimize storage and usage. In such a case, there may be economic benefits to doing so for the entire grid.
Renewables also tend to get cheaper over time; this is supported by something called Wright’s law, which says that more learning and experience tends to reduce the cost of a product each time it is produced. Interestingly, decarbonising the grid might also actually be cheaper for everyone – regardless of the need to do so to tackle climate change. From this textbook chapter, ‘an analysis by the Deloitte Economics Institute found that inaction on climate change could cost the U.S. economy $14.5 Trillion by 2070’ and ‘the U.S. economy could gain $3 trillion, and add nearly 1 million more jobs, if it rapidly decarbonizes over the next 50 years’.
Overall, the barriers to climate change are more political and social (see more about that in this bite) than many have been led to believe – the ideas and solutions we need exist, and decarbonising is actually possible. We don’t need to despair, but we do need to start acting to start tackling the problem.
Edited by Katherine Lee
Author
I am a third year PhD student at the University of Queensland, studying Large Scale Structure cosmology with galaxy clustering and peculiar velocities, and using Large Scale Structure to measure the properties of neutrinos.
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