On Science Daily an article of Solar cells with an efficiency over 40 percent, i.e. more than 40 percent of the sunlight received is converted into electricity. This development is important, both for space settlements and terrestrial energy supply.
On Science Daily there is an interesting article on the structure of quantum dots. Better understanding of this structure would lead to more efficient solar cells, wich of great importance for space settlements.
Though there is broad consensus that Solar power will be the principal energy source for Space Settlements, several methods of converting Solar power into useful forms of energy have been proposed. In most cases this means to conversion of solar energy into electricity, but also the production of thermal energy of industrial importance.
In most Space colonization plans space habitats and solar power satellites are proposed as separate structures. This because space habitats have to rotate in order to generate “artificial gravity”, whilst solar power satellites are preferentially kept stationary. Most proposal suggest microwaves as the method of power transmission to space habitats (or even to Earth), where the microwaves are converted into electricity.
In Space colonization literature two main types of Solar Power Satellites (SPS) have been proposed: the first type uses Solar energy to heat a fluid (such as helium) to drive a turbine to generate electricity. The second type uses photo-voltaic cells to convert Sunlight directly into electricity. Both types use electricity to produce microwaves, which are then beamed to the consumer.
Type I satellites are by far the most simple SPSs to construct, and have been proposed since the 1960s. Basically you only need a mirror, tubes, a compressor, a turbine and a working fluid to build one. Back in the 1970s photo-voltaic cells were much less developed than today. And for that reason most early proposals for Solar Power Satellites were of this type.
Another advantage of type I satellites of type II ones, is that photo-voltaic cells will deteriorate due to their exposure to Solar winds. And consequently type II satellites will decrease in power output over time.
But on the other hand type I satellites are much more vulnerable to meteorite impacts. A small hole in one of the tubes caused by such an impact, will cause the working fluid to leak from the system; which will render the entire plant useless. However, if a type II satellite, which is composed of a multiple photo-voltaic cells is hit by a meteorite, only the cells which are hit will be destroyed, whilst the others will still be in operation.
Compared to type I satellites, type II satellites are less massive and hence require less material resources to be built. Also type II satellites have no moving parts, which are subject to wearing off.
Besides these two main types, several other types of Solar power satellites have been proposed. An interesting proposal are Solar-pumped lasers. These are laser which are powered directly by Solar power, without the intermediate step of producing electricity. The generated laser beam can then be used to transmit energy over great distances. This has several potential applications.
First, such lasers can be used to propel solar sails throughout the solar system. A second application is to transmit power to settlements at great distance from the Sun. The amount of Solar power one receives, decreases with the distance to Sun squared. For instance Saturn is located 10 times as far from the Sun as Earth, and receives per squared meter a 100 times less energy. A solar power satellite in the neighbourhood of Saturn needs to be a 100 times larger than a comparable satellite in the neighbourhood of Earth.
Since laser beams are highly concentrated, a solar-pumped laser in our neighbourhood could power a SPS close to Saturn. And that SPS could be considerably smaller.
Lewis Strauss coined in reference to the prospect of fusion power, the phrase too cheap to meter. Mr. Strauss argued that once fusion power would become available, the costs to produce electricity would be so low, that wouldn’t be worthwhile to charge the consumer in respect to their actual energy consumption.
The principal source of energy in Space Settlements is, of course, solar power. Our natural fusion reactor produces such amounts of power, that only a tiny fraction is needed for use by Space Settlers. Hence the question arises whether Space Settlers should be charged for their actual energy consumption?
Though the Sun does deliver its energy for free, it does not mean that the energy consumed by Space Settlers should be free. In order to make use of Solar energy, Space Settlers should convert it into useful forms of energy, such as electricity. This requires the construction of Solar Power Plants (SPPs).
And though a SPP has no fuel costs, it needs money for its construction and maintenance. Further the SPP has to be protected against meteorites and terrorists. It is obvious to someone has to pay for these services. And then we are only talking about the power plants, what to think about the construction and maintenance of the grid? But the good news is that even if we take these cost into consideration, space settlers will receive a considerably lesser energy bill than their terrestrial fellows.
The backside of SPPs is that the initial investment to build them, is quite high (though this would be compensated by the extreme long service life of the plants) and hence vulnerable to emerge of monopolists. After all once a space energy company has built a SPP, it can offer energy at relatively low prices, while the threshold of building a new plant will deter potential competitors.
Since such a monopoly is likely inevitable, it would be best if the governments of space settlements will take care of the production and maintenance of SPPs. This had two benefits: first all profits will flow to public treasury, and secondly price setting by the energy company is subject to democratic supervision.
Serving the Internet we found an interesting development: The Himalayan Kingdom of Bhutan is planning to replace all fuel power car by electric ones. The country’s aims with this plan to cut the expenses on oil imports with 70%, and hence to save money. Due to its location, Bhutan is able to produce huge amounts of hydro-electricity, of which most is exported. At this moment private citizens are not allowed to import cars, but some observers expect the authorities may make an exception for electric cars.
With the approaching peaking of oil production, and subsequent oil depletion, more countries might follow Bhutan. And in space settlements we see no use for cars powered by internal combustion engines. Especially because in space solar power is abundantly available.
We found on The Independent the following article Japanese engineers plan to turn the Moon into a giant solar panel station. It’s clear that Japan is busy to look for alternative energy resources after the Fukushima disaster of 2011. This plan is a subset of so-called space based solar power or SBSP. The idea is to install solar panels on the Moon which will turn electricity into microwaves which are subsequently transmitted to Earth, and converted back to electricity.
We of Republic of Lagrangia aren’t convinced of the desirability and feasibility of SBSP for terrestrial purposes. We have discussed this topic earlier on this blog. And we have also written about Ocean Thermal Energy Conversion as a solution of Japan’s energy crisis. As an alternative we have discussed Solar Energy Islands as a method of producing energy at sea.
Though space and air flight are as distinct from each other, as air flight and ship transport are from each other, many people do group them together. Therefore we’ll discuss in this post the future of aviation on Earth.
Of all types of aircraft air-planes are the most well-known and together with helicopters the most popular ones. Most air-planes are powered by burning kerosene. Unfortunately petroleum, of which kerosene is made, is going to be depleted in a few decades. And given that simultaneously the amount of air traffic is increasing, flying will become more and more expensive.
For other modes of transportation the depletion of oil is less a problem, ships can be powered by wind, by using kites. Land based vehicles can be powered by electricity and can be recharged along the route. An electric plane is possible but a commercial air plane would need very heavy batteries, which would mean that fewer passengers and cargo can be transported at a flight.
An easy solution would be to replace petroleum-based kerosene by bio-fuels or synthetic fuels. Bio-fuels have they big disadvantage that the production of it will compete with food production, and hence will increase the price of food and lower people’s access to food.
Another option would be to reconsider airships. Since the disaster with the Hindenburg airships have fallen out general use, but modern version use inert helium rather than flammable hydrogen as buoyant. Only helium is on Earth are rare resource, and much of our helium reserves is wasted in, for instance, helium balloons at parties.
Fortunately there might be good news. With the prospect of oil depletion, more people are turning to fusion power as a method of energy production. And the primary waste product of fusion power happens to be helium. With more fusion power plants, also more helium will be produced. And hence more airships can be produced.
But wouldn’t be nice if we could use solar energy to power air planes? Well, NASA just did that, their Pathfinder planes are basically flying wings covered by solar arrays. But these are small, unmanned planes designed for research purposes rather than for transportation. For commercial air planes huge solar panels would be required.
The Canadian company Solarship has developed an aircraft which combines airship technology with solar energy. Their hybrid airship, while being heavier than air, gets a substantial part of its lift from buoyancy and therefore reducing its fuel consumption.
The people behind Solarship claim that the main benefit of their product is that increase the accessibility of many parts of the world, because no infrastructure is required for the operation of their airship. Though they intend to use their airship for cargo, it seems also to be usable for transporting people.
A totally different approach more suitable for mass transport along predetermined routes, is the vacuum tube train also known as “vactrain“. The idea is to drive maglev trains through long vacuum tubes, because it takes less energy to remove air from a tube than for a maglev to overcome air resistance. This approach would allow speeds up to 8,000 km/h. Vacuum tube trains might be powered by fusion power plants.
Space advocates are often accused of that they are not concerned with the future of our own planet or that they have no solution for terrestrial problems. Of course it is not true that space advocates have no concerns or solution for Earth, only different space advocates have different ideas on dealing with these issues. Save from the direct benefits of space colonization for Earth, the space movement has no single coherent vision for solving terrestrial problems. However, this does not prevent space advocates from developing and discussing ideas in this area.
On Republic of Lagrangia we have posted several posts on several terrestrial issues. I will give here an overview.
On energy policy: