Summaries of studies/articles:
Information from:
https://www.theguardian.com/environment/2011/aug/31/pipe-balloon-water-sky-climate-experiment
http://www2.eng.cam.ac.uk/~hemh1/climate/Geoengineering_RoySoc.htm
https://www.britannica.com/video/82470/formation-clouds-rain
https://www.shsu.edu/~dl_www/bkonline/131online/f05elevation/05index.htm
https://en.wikipedia.org/wiki/Airborne_wind_turbine
https://www.sciencedirect.com/science/article/pii/S1364032116304282
https://www.timeanddate.com/weather/western-sahara/el-aaiun
There has been a lot of scientific research on the many ways that we may be able to create a ‘volcano in the sky’, allowing particles of chemicals to enter the stratosphere in a mimicry of the cooling effect erupting volcanos have. This would work through linking a balloon with a garden hose to Earth 20km high to release chemicals into the stratosphere, reflecting the sun and cooling the earth. A £1.6m grant from the government is allowing British scientists to do a smaller scale experiment, pumping water into the air, and this will soon escalate to other chemicals if it is successful. A balloon has been found to be the cheapest option to bring these chemicals into the stratosphere. There has, however, been criticism from environmentalist groups, who say that this experiment would do nothing to solve the carbon dioxide problem, which is the real issue of global warming, and it could have bad side effects. There are also other methods (ocean nourishment, space mirrors, cloud nourishment, artificial trees, albedo changes, carbon capture and storage) that have been explored to help the global warming issue.
The SPICE project stands for Solar Radiation Management (SRM) and works with stratospheric particles. In this project, particles are to be injected into the stratosphere at heights 10km-18km. There are many different methods for delivering these particles, including using aircrafts, balloons, ballistics, thermal plumes, or a fixed tower/pipe supported by balloon. The rate required for effectiveness is 1Mte p.a. and the estimated price is to be above 1bn p.a, but the pipe method would cost 1/10 of this. In order for such a big project to be executed effectively, exploration of the different methods is important, in terms of modelling and designing, as well as safety issues. The project accepts the chance that global warming may be a process too far gone to repair completely, and therefore aims to minimise the effects of global warming, even if it cannot stop it altogether. Just as in the aforementioned research, this project is inspired by the cooling process of volcanos. It aims to find the ‘perfect’ particle, in order to maximise the reflection of the sun. The best location for these injections of particles is yet to be decided.
Water droplets in clouds can block sunlight. Sometimes, they can condense on the ground, which creates fog. These are often in valleys where hills are blocking their paths. Clouds can travel with wind and wet the ground with dew. Clouds bring water from places that have water to places that do not, replenishing those areas. When droplets become larger, they become rain droplets. These help plants, animals and humans. The sun then evaporates some of the water, and the cycle continues. Scientists are also suggesting that we shoot seawater into the sky, forming clouds, and allowing this to cool the earth, termed ‘marine-cloud brightening’. In 1990, it was proposed by John Latham that increasing clouds’ ‘droplet concentration’ could prolong their lives, which would then allow for more sunlight to be reflected back into space. The Rayleigh Jet technique they propose to use involves having ships spray the water from the seas. The saltwater would leave behind salt crystals which would help form more clouds. The report found that there was an increase of 5% in reflection by using 30 megawatts of energy. However, there is debate over how effective this would be, as the reflection of the sun varies so much that our efforts may be lost in the sun’s natural variations. There are also concerns over how these efforts would impact the effectiveness of solar energy. It could lead to a drop in the solar panels’ effectiveness by as much as 20%. They could also be harmful for the global warming effects for future generations. It is therefore not recommended that we look at these methods as solutions for present times, but as a last resort.
Elevation clearly effects the weather, seen in the mountains that have snow upon them, when below, while in the same area, the weather is hot and dry. Air density is important, as the higher you go up, the thinner the air is. You are also going further away from the land/water that can heat and cool the earth. Mountainous areas are especially effected by the sun’s radiation and its temperature. In the night, then, the thinner air also makes the temperature drop much faster than areas lower down. The Environmental Lapse Rate shows the rate which the temperature heats and cools as you rise higher in the atmosphere. There are sometimes ‘inversions’ where the temperature rises rather than cools as the elevation goes up. Clear skies can cause nocturnal inversions, as well as dry air, the occurrence of short days and long nights, calm winds, and snow-covered surfaces. Upper air inversions are associated with desert areas, as it is very hot on the surface of the desert, and the temperature drops sharply as you elevate. This is the result of two columns of air meeting and creating a cap and an inversion.
This is especially important when considering the creation of the Saharan forest. The Dew Point is the cool temperature that the air must be in order to be saturated with water vapour, which would then become dew. The Dew Point for the El Aaiún in the Western Sahara area has been recorded as 15oC. As the air above the Sahara is cooler than that on the ground, creating clouds above the Sahara would have the effect of cooling the ground, and therefore perhaps making it easier for plants to grow and to positively impact climate change. As it stands, the Dew Point would be high above the floor of the desert.
An airborne wind turbine is another option to be considered when thinking about methods to combat global warming. This term refers to a design for a wind turbine that resides in the air with a rotor and no tower. The wind would be more efficient at this higher level, and the cost of a tower would be avoided. There are challenges with safety, transferring the power back to the ground, and with aviation interference. The aerodynamic variety relies on the wind for support, similar to a kite, and have been researched since 1980. The aerostat variety relies on buoyancy to support it, often incorporating balloons. Shell and Google are commercialising the potential disruptiveness of high altitude wind energy systems. Shell aims to make floating offshore wind farms, and are investing in Makani’s project. The Makani kite is aiming to ascend to 1,000 feet, compared to the commercial wind turbines which reach over 300 feet. Traditional kinds of wind turbines are heavier and cost more money.
As an example of these kind of energy resources in action, HAWPs in Northern Ireland are largely based on Loyd’s work, who suggested ‘crosswind kite power’. These are ground-based power solutions that involve kites and a tethered ground power generator. They would be using rigid wings, which can mean significant power losses when they are being put into maintenance. Multiple wing systems can extract more power. Using an ABM, the 3 most prominent approaches are tethered kites, rotorcrafts, and balloons. Kites are favourable because they would survive crashes better and they can be designed to be very lightweight. Rigid wings can create more power but can have worse consequences in the case of a crash. A high voltage tether is necessary, but it cannot be too heavy. There are many safety limitations to HAWP systems, which could be solved by limited airspace zones for the HAWP devices and lights could improve their visibility. An alternative for HAWP devices is propulsion systems for ships, although this also lacks feasibility. The study that I have linked above identifies some geographical limitations for the HAWP devices; motorways, railways, settlements, airports and military training areas, controlled airspaces, and protected areas. The Northern Ireland example was taken over 20 years. The wind power densities ranged from 1850 to 2100 W/m2 at 3000m of height. The results show that there is a lot of potential for HAWP in Northern Ireland, although this is still a developing field of research.
In order to create rain for our Saharan forest, the many different methods of creating immediate relief from the effects of climate change are especially worthy of research. Due to the specific environment of the Saharan desert, creating a cooler ground surface area through ‘marine cloud-brightening’ may assist this affect, although it could counter-balance any attempts to utilise the area for more solar-panels, in order to encourage rain. Using HAWPs and airborne wind turbines seem effective ways to create sustainable energy, although they seem reliant on the area that they are built in, in order to have the best return. However, many of the methods discussed here appear to favour minimising the notable effects of global warming, rather than fixing the source. Rather than this approach, I would advise looking into using these methods to assist in creating a better solution, such as a Saharan forest which is useful in reversing the carbon dioxide abundance in the atmosphere.