Solar Techonology

The energy of the light is part of your existence. Without it life wouldn’t have been able to grow, and if it suddenly ended, life would disappear.

The relationship between the man and the Sun has always been filled with mystery and confusion. Since the men started to consider the sun a God, the explanations about the light and energy we get from it were variants, but we have always known how to take advantage of its effects.

The first farmers discovered, many thousand years ago, the relationship that exists between the hours of sunlight exposure and the speed of growth of some vegetables, but until the scientists clarified the process of Photosynthesis, said relationship was difficult to explain.

Some villages in the ancient times came to develop mirrors and lens capable to concentrate the light, but besides on rare occasions, people only took advantage of some of the reflective and refractive properties of the light, without knowing how to explain the energetic properties.

Source: inhabitat.com

 In places with high sun exposure times and clean atmosphere, is possible to obtain part of the domestic electricity from the Sun. Through big panels, provided with a high number of photovoltaic cells, its possible to transform the solar energy into electricity to warm the house, make run the appliances, get hot water and all those things we usually get thanks to the energy from the electric companies. All of this thanks to a clean and economic system.

The sunlight going mainstream

The human beings have learnt to use the sun light better. Little and big experiments have been developed to make our lives more comfortable. Greenhouses use the sunlight to maintain its elevated inner temperature; in cold weather places, the homes have big windows to use better the light and heat from the sun. There are experimental electric centrals that transform the energy through photovoltaic cells.

The invention of the artificial light

source: littlerockfamilyhousing.com

So far we have seen examples of how the solar energy can be transformed into other forms of energy. However, human beings also have learnt to produce light from other energetic sources.

Our ancestors discovered that anything that burns produces certain amount of light, but it took a long time to find materials that could burn slow enough and produce significant amount of light. The torches, the candles and candiles were the only acceptable result produced after thousand of years, until in the XIX century some experiments were developed to use the gas and petroleum as lighting systems. 

 At the end of that century a really effective system of artificial illumination was found: the light bulbs that could produce light from electricity. Inside there was a metal filament; when electricity flows, the filament heats ‘til incandescence and produces light. For the filament to not burn, Oxygen must be removed from the inside of the bulb. Many electric lamps have been developed; some don’t have filaments, but gases capable to emit light.

 

Solar Powered Cars

Solar cells are capable of producing a reasonable amount of electric energy from solar light. This has stimulated the imagination of many creative people around the world.

One of the most attractive uses for the photo electricity –electricity produced by light– are the vehicles powered by solar energy. So far, tests on airplanes, boats and cars have been performed with different results. A light airplane, which had all the roof covered by solar cells capable of producing enough energy to move an electric engine, was able to fly over the English Channel. 

Each year on Australia an original race is celebrated where only solar powered cars run. The participants have to travel from side to side the Australian continent and most of them don’t finish. The average speed accomplished by these cars is between 50 and 80 Km per hour.

The disadvantage of vehicles directly powered by photovoltaic cells is that they only work well on places with a exceptionally clear and sunny weather.

As usually happens on the high technology business, Japan is one of the pioneers on solar energy applications to transportation. The main inconvenient of using solar energy on vehicles is the necessity of using heavy accumulators or batteries that occupy too much space. This is because of the need of store energy for the vehicle when there is no solar light available. The batteries store the energy when solar light is abundant.

A possible dream 

In the 60’s, experts around the world worked in a project that could look as science fiction. It involves launching an enormous space station to convert solar energy into electricity and send it to the earth in form of microwaves.

 

The space station would have 3 main parts: a solar collector of 6 Km long by 2.5 Km width, build of mirrors and photovoltaic cells; a energy central and a microwave transmitter. Despite its cost, an installation of this magnitude could be rentable on the long run thanks to the fact that the energy efficiency of solar cells is higher outside the earth’s atmosphere. This microwaves could be transformed into electricity again on earth. 

 

The microwave transmitter space station project has never go further than in paper, many hoped that this could have been the end of the fossil fuels. Nevertheless, some day we could have to give a chance to these exotic and crazy methods to obtain efficient energy for men.

 

Solar Energy

The solar light is very important for the life on earth. It’s one of the most important world energy resources used by plants and seaweeds to transform the nutrients to grow. The oxygen we breathe is released in the process.

The plants absorb water and minerals through the roots that end up in the leaves thanks to a network of small conducts. The leaves absorb Carbon dioxide from the air and, with the help of these 3 substances –water, minerals and Carbon dioxide– the plants build their tissues. To be able to do so they need energy, the same as we do for your foods. The energy the plants use is the solar energy they get and transform it through the process of Photosynthesis

The photosynthesis

The leaves of all plants have a green substance called chlorophyll that is used to retain light energy. This energy allows them to separate the Carbon and Oxygen from the Carbon dioxide and combine the carbon with the water and minerals stored in the leaves. The results of these combinations are the sugars and starches that are the majority of the nutrients of the plants. The oxygen is free and released during the process. This all together is the process of Photosynthesis. That’s why reforestation projects must be put in practice to help reduce carbon dioxide in our atmosphere.

The humans benefit from the solar light too

We need the light energy, among other things, to produce an essential vitamin for our growth and conservation of our bones and teeth: The vitamin D. Our body produces this vitamin, in the skin, through a similar process to the photosynthesis of the plants.

An excess of light can be dangerous

A part of the solar energy, the ultraviolet radiation, can seriously harm the living things but, luckily, the largest part of all the radiation doesn’t get to us. It is retained by the ozone of the outer layers of the atmosphere. The small portion that gets through can harm our skin if we do no take cautions when we expose ourselves to the sun for too long. A skin cancer specialist will recommend we should not expose ourselves for too long especially during the summer.

The balance of life

Without living things there is no oxygen, without oxygen there is no ozone, without ozone there are no living things…Life on Earth depends on the balance of many factors that must act in the right measure: with no solar radiation there is no life, but an excess of it could kill everything.

A short history review: Ozone Formation

About 4 billion years ago life started on Earth. However, for many million years there was no life on the land, because of the high amount of radiation from the sun that hit the Earth that made it impossible. The only living things were on the bottom of the oceans, and were mainly seaweeds. At some point, a new kind of seaweed appears, with chlorophyll that start occupying the shallow areas close to the shores. There they get enough light to be able to do photosynthesis and were safe from the excess of solar radiation. For million of years, these seaweeds released oxygen, than ended up in the atmosphere. So, the primitive atmosphere of the Earth began to change, reducing the proportion of carbon dioxide and increasing the oxygen to the levels of our time. From the atmospheric oxygen, ozone started to form, that accumulated in the outer layers of the atmosphere. The ozone prevents harmful solar radiation to go through, and, when the ozone layer had enough thickness, some organisms began living outside the water, on the mainland. It was the beginning of the conquering of the planet. 

The ozone is not an especial or weird substance. The ozone is just oxygen in a tri-atomic molecular form, this means, 3 atoms instead of 2 of the “normal” oxygen molecules. This is the reason ozone is so unstable.

Stay tuned and will explain the Photosynthesis process in a chemical way ;)

Energy Transformation

This is an important concept you must know, it is studied in the firsts courses or High school and University, but still a very hard topic to understand. the hardest course about energy i took was Thermodynamics.

Matter and Energy

The entire Universe is formed by matter and energy. The matter is relatively easy to distinguish: wood, plastic, water or steal are different examples of matter; but the energy is a harder thing to describe and define. In our everyday lives we rarely stumble upon pure energy, but with the effects of it over matter. The water of a mountain river has energy because it is capable of moving rocks, but when it gets to the plain and calms down it can no longer do anything: it has lost its energy. A new battery can light a bulb, but after hours of work it stops: it has consumed all the battery energy.

Even though we can only explain energy through its effects, we can measure it. We can know, for example, the amount of energy that there is in the water hold in a dam, in a gallon of gasoline or in a battery.

The light, from the Sun or from devices made by man, is one of the purest forms of energy. Its effects are present constantly in our lives. Today we can see how this type of energy is being used, with solar panels, the energy efficiency of these devices is still low but in the next years we can expect improvements on it.

One of the ways to recognize energy is by its capability to perform a work. A brick in the ground doesn’t have energy, but if we lift it, it has stored energy that will be released upon drop. To break a nut, you have to apply a force on it. If you put a nut in the ground and drop the brick, the nut will break. The work of breaking the nut has been performed by the brick with the energy you transmitted to it when you lifted it.

The water in a dam looks placid and calm, but it has an enormous amount of energy stored. When the gates open, the water goes out with extremely force. If we channel towards a turbine, we can take advantage to make clean energy, but if the dam breaks it can destroy everything on its path.

The solar energy hits the Earth in the form of light and heat; the plants use it for their growth. On this wheat field the solar energy is transformed into substances on the grains that are used as food.

Source: Ciencia Recreativa (1992) - Planeta Agostini 
 

Density Facts

So in the end, in relation to the floatability of a body the most important thing is not the absolute density, but the relative density of the object and the fluid in which the object is immersed. For example, the wood is a dense object and heavy in the air, but it is not if its in the water, because the density of the water is bigger than the wood’s.

This concept is used in many aspects of our life. The most common gases used are fuels, butane, and natural gas, and the most common residue from combustion, the carbon dioxide, all are denser than air, therefore they do not float in it, but occupy the lowest part of their location. The vents on kitchens and other places where these gases are used or produced are located in the bottom part of doors and walls that lead outside to allow this dense gases to flow out. The vents located in the upper part allow the entrance of new fresh air.

Salty water

The dissolution of Salt in the water increases its density. This is the reason for the sea water has more density than river water. The difference is not that big, but enough to allow some objects with density almost the same as river water to float in sea water.

Couple of tourists in the Dead Sea. They are no sitting down on the bottom: they float because of the high salinity

The composition of sea water is not the same in every part of the world. In closed seas, or almost closed, and medium depth, as the Mediterranean, the Black Sea or the Dead Sea, the higher evaporation of the water produces bigger concentrations of salt and therefore increased density. The open and deep oceans like the Atlantic or Pacific have waters with less density.

Swimming in the Dead Sea

 An extreme case of high density caused by high salt concentrations is the Dead Sea. The dead Sea is, in reality, a salty lake of about 80 Km long and 17 Km wide, located in Israel and Jordan. Its depth is low, about 40 m average, and it changes a lot depending on the seasons. The low depth and the fact that its surface is located about 390 m under any other ocean and sea has favored the evaporation of the water for thousand of years, producing a high concentration of salt like any other sea. The density of these waters is high, so floating in them is quite easy. In fact the hard part in this sea is to drown, but at the same time these conditions have banished any kind of vegetal or animal life form in it.


Source: Ciencia Recreativa (1992) - Planeta Agostini 

Taking Advantage of Density

As we already know, the floatability of an object depends of the hydrostatic push of the fluid in which it is immersed. Objects which density is lower or equal to the density of the fluid will float.

Float in the water

Sometimes you would wonder, why all those big ships made of steel can float in the water? Even though the iron and steel are like 8 times denser than water, a boat can float because in its design, the major part of its volume it’s occupied by air, which is like nine hundred times less dense than water. Therefore the ship and the air contained inside of it, is less dense than water.

Submarines

The submarines obey the same principle we have applied to ships, but they are able to increase their density to submerge and navigate under water, and decrease it when they want to float and sail in the surface.

The increase or decrease of the density of a submarine is accomplished by pumping water from and into the ship. The submarines have, distributed along its structure, tanks that are filled with water to increase the density of the ship to submerge, or air to make it float.

 Up: the submarine in the surface; Middle: as the tanks fill the submarine submerge; Down: emptying the tanks makes the submarine go up again.

Fish Swim bladder

Most of Fish balance their density with the water surrounding them with a special organ, called the Natatory Bladder or Swim Bladder, located in its abdomen, and in some cases connected to the digestive system. This Bladder is a bag of muscle tissue filled with a mix of gases.

This Bladder may assist the fish increasing or decreasing its density. By compressing the air which is contained in it, the fish descends in the water; and it rises again by relaxing these muscles which had served to compress the bladder. The gas density is less than the density of water.

Source: snhs-plin.barry.edu/Research/Fish_Anatomy.htm

Globes and Zeppelins

Everything I said about density and hydrostatic push is valid for all fluids, gas and liquid. Therefore it can also be applied to the air. The bodies immersed in air also experiment a push towards up that equals the weight of the displaced volume of air, but this push has a low value for objects with high density, as the human body for example, and its effects are not noticeable. This is not the case for low-density objects.

Some gases, like the hydrogen or helium, are less dense than the air. If we fill a bag of an impermeable material with any of these gases, the bag will experiment a push towards up superior to its weight and, if we set it free, it will ascend. This is the principle in which globes and zeppelins go by.

When we talk about the atmosphere, the lower layers of air close to the surface of the earth are denser, partially for the pressure of the superior layers.

We also need to know that the gas density decreases when the temperature of that gas increases, that is if it doesn’t find obstacles to increase volume.

Open and Closed Globes

The Globes that use the mentioned gases (Hydrogen, Helium) have to be necessarily closed, other way the gas would just escape and the globe would crash. But there are ways you can make an Open Globe fly. In this case the gas used to fill the Globe it is the same air, but increasing its temperature above the temperature of the surrounding air.

As long as the temperature of the air contained inside the globe it’s higher than the one outside of it, the globe will ascend, but there is a limitation. We said already that the air density in higher atmosphere layers is low, As the globe ascends, it will eventually find these high-density air layers and to keep ascending it will need to increase its temperature even further. Finally, in higher atmosphere layers, the density of the air is so low he globe won’t be able to ascend anymore no matter how much it increases the temperature of the air inside of it.

The Zeppelin

The Globes, open or closed, depend of the airstreams and wind to come and go. The zeppelin is a kind of closed Globe that has an engine attached to it that moves some propellers. This way it no longer depends on the wind. At the beginning the zeppelins were full of Hydrogen, but this gas is very flammable so it was replaced by Helium, although more expensive it was safer.

The last zeppelin dedicated to passenger transportation was the Hindenburg, of 247 m. of length and capable of lifting 22200 Kg. It was full with Hydrogen, and in May 6^th 1937 it went on fire when it was landing on New York.

Source: Source: Ciencia Recreativa (1992) - Planeta Agostini

Everything Floats

Today I'm gonna introduce a physical concept that is used a lot in Chemistry. Like some physical properties, this one is hard to explain; I never had a clear concept on college and only understood it correctly in university.

Let’s use this example:

What weights more, a pound of rocks or a pound of feathers?

                                  

Both are the same, a pound is a pound, the difference is that to have a pound of rocks we would only need a few smaller rocks, but to get a pound of feathers we will need a lot of them.

The difference of the volume occupied by these 2 objects is because of the difference of DENSITY between them.

The density of a material is its weight divided by the volume occupied by that mass. The density of liquid water is 1, this means I liter of water weights 1 Kilogram, but the density of ice is 0.9 because 1 liter weights 900 grams. This is the explanation of why the ice floats in your drink.

Hydrostatic principle

If we tie a rock to a string and we immerse it into water we observe that the necessary effort to hold it is less than when it is in the air; it’s like if its weight was decreased. In the same way, if we try to sink a glass pushing its bottom into the water we will notice a big resistance.

These 2 phenomenons obey the same reason: Every liquid exert over the objects immersed in them a force in the contrary direction of the weight, called Push or Bouyancy.

Archimedes discovered that the push experimented by any object immerse in a liquid or a gas is equal to the weight of the fluid being displaced but in opposite direction.

Floating

 

Therefore, on any object immerse in a liquid act 2 forces: its own weight, directed to the center of the Earth (gravity) and the push force of the fluid, directed in the opposite direction. When the weight is bigger than the Push, the object sinks. When the push is equal to the weight, the object remains suspended in equilibrium without movement. And when the push is bigger than the weight, the object goes up to the surface until the weight of the immersed section equals the weight of the displaced fluid.

 Any object can float, as long as it is immersed on a substance more dense than itself, like this bronze object that is floating in Mercury. 

 Source: Ciencia Recreativa (1992) - Planeta Agostini