Renewable energy sources

Why focus specifically on renewable energy sources? As discussed above, these sources have certain advantages that are emerging increasingly critical More »

How does a solar panel work


A solar panel is composed of solar cells made from silicon. Each cell directly converts light into electricity. A solar cell is composed of a thin plate having a negative charge and a positive charge over below. This plate is made of semi-conducting material, usually silicon, which conducts energy when there is light. The energy of the sun light starts an electric current of thin metal plates in front of the cell, which, by the electrical application, goes back to the metal behind the solar cell. The cell will transform a larger or smaller portion of light into electricity, depending on the type of silicon.

The sun does not always shine strong, but still gives enough energy to power solar panels on cloudy days and give us electricity, also in winter. We call it indirect or diffused light.

In order to deliver enough energy, place the solar panels so that the light falls there as much as possible. They do not really need to be oriented to the south. An orientation between southeast and southwest and a tilt angle between 20 ° and 60 ° will also perform well. The photovoltaic panels are bonded to each other and connected to batteries or the electricity current.

off-grid-pvAutonomic systems

An autonomic photovoltaic system produces electricity for an electricity consumer who is not related to the electricity current. The photovoltaic panel delivers electricity directly to the electricity consumer, the residue is stored in a battery. During the night or when the sun does not deliver enough electricity, consumer takes energy from the battery. Typical examples are calculators, watches, the lighting of the gardens and streets, parking meters and buildings in isolated areas.

residential_grid_pvNetwork-related systems

In a photovoltaic system connected to the network, the DC voltage of the photovoltaic panels is converted into a useful AC voltage that is directly delivered to the electricity grid. This happens by a transformer. Network-related systems do not need battery. When consumers use less electricity than delivered from photovoltaic panels, the residue is directed to the network. The electricity meter will return to this point. During the night and when the sun does not deliver enough electricity, the energy will be taken from the electricity network.

Efficiency and yields per m²

1m² surface of photovoltaic panel creates by year moderately slightly over 100 kWh. For dANYO high yield per m² panels generates even up to 160 kWh / m² or more. The average electricity consumption of a family in Belgium is 3500-4000 kWh per year. To generate the electricity we would need an installation having a surface of 35 to 40 m2. Because of system connection to the grid, system should not annually produce electricity as a family consumes. In practice the steps of the installation rather depend on the budget available and the place of performance available.


The power of a photovoltaic system is expressed in Wp (watt peak) or kWp (kilowatt peak. 1000 Wp = 1 kWp). This is the power that the photovoltaic system produce during standard sunlight. The power per m2 of photovoltaic panels also depends on the type of cell and producer. It varies between 50 W per m2 of the amorphous silicon and 170 W per m2 of solar cells made of monocrystalline silicon with high efficiency. For Sanyo panels even 190 W per m².

Renewable energy sources

Why focus specifically on renewable energy sources? As discussed above, these sources have certain advantages that are emerging increasingly critical – particularly inexhaustible nature of these resources, and low environmental impact compared to other sources energy. The development of the use of renewable energy sources is inevitable (the oil, gas, etc. are beginning to run and generate international tensions), but what is more, particularly desirable for the protection of our environment , the biosphere and the planet.

Human activities have caused enormous changes at continental and global scale, particularly in the use of fossil fuels. The global warming phenomenon explained by the increase in anthropogenic “greenhouse effect”, already evident effects: melting polar ice caps, El Niño, migration or extinction of animal and plant species, etc. As for nuclear power, whose operation does not appear to cause such effects because it does not produce any “greenhouse gases”, it remains dependent on limited resources and its emissions are so potentially dangerous (waste radioactive) it is necessary to bury in “dumps” where it is desirable that nobody comes before venturing a good million years. In short, nuclear power will be an interesting solution in the long term if we solve (at least) the problem of production waste. But today, it is still far from being the case.

You will agree, therefore, the only sustainable energy sources are renewable sources of energy. Let’s see what it is and how it is possible to exploit them.

Solar energy: photovoltaics

Using semiconductor materials such as silicon, it is possible to make devices that convert sunlight into electricity: this is what is called solar cells or photovoltaic cells. By having a solar cell in the sun, a voltage appears across it: it is a solar energy converter into electrical energy. The solar cell makes it possible to capture solar energy – at least one party. Currently, the best solar cells have an efficiency of about 15%, which means that 85% of the energy that reaches the surface of the solar cell is not converted into electricity. Indeed, it makes a lot of losses, but 15% is not bad and it’s mostly better than nothing when you think that this energy we “fell” from the sky all day (weather permitting).

By assembling solar cells can be realized solar panels, such as those that supply many artificial satellites but also, more recently, such as those that can be seen already timestamps, telephone booths, and even houses roofs. The production of electricity by photovoltaic conversion worth to grow because of its low yields compared to its still high cost (photovoltaic panels are relatively expensive even if the price was divided by four between 1970 and 1990 and more since) .


  • Resource available everywhere on the surface of our planet, especially in temperate areas, tropical and equatorial.
  • The photovoltaic panels are particularly suited to roofs and can produce some of the electricity needed for a home without unnecessarily occupy space.


  • Dependent on non-renewable energy storable the weather. Power generation is random.
  • Still expensive photovoltaic panels.
  • The maximum production level depends on the sensor surface exposed to the sun, resulting in a large footprint (or on the roof or the facade) as soon as one needs a fairly consistent power.


  • Well suited to the electrification of isolated sites such as mountain refuges, radio relay, sheep, non-insulated homes connected to a power grid.
  • Suitable for low power consumers and / or mobile devices (calculators, satellites, timestamps, sailing equipment, …)
  • Suitable for food refrigeration or air conditioning systems (especially in very sunny and very hot countries!)
  • Unsuitable for uses such as heat generation, propulsion (even if it is still possible See for example the solar plane.)
  • For the production of heat or cold, solar thermal energy is much better (it avoids going through the form of electrical energy, which reduces conversion losses)
  • Photovoltaic panels can also be connected to the power grid. Owner becomes electricity producer for the other when its output exceeds its own consumption.

Solar thermal energy

The sun warms us of course, but it is possible to capture this heat to use for a particular purpose. To do this, use different types of sensors. This goes for the cover outside the pool (made of plastic bubbles dark) until glazed collector solar water heater, through the greenhouse or frame gardener or simple porch. In all these cases, the sensor (glass) creates a “greenhouse effect” by letting solar radiation and by trapping heat within the space it defines.

But solar energy can also produce cold if a refrigeration device using type “absorption”. In this case, as in the case where it is desired to carry this heat, the sensor is placed behind a metal tube in which a coolant fluid circulates – that is to say that will “bear the heat.” In general, we chose an inexpensive fluid, abundant and environmentally friendly: water! Finally, you can also add a sensor system that concentrates sunlight to reach higher temperatures. The latter system is usually part of a complex system to produce thermal electricity plant type. This brings us to a completely different area which would require a web page alone (coming? …).


  • Energy available everywhere on the surface of our planet, especially in temperate areas, tropical and equatorial.
  • Solar thermal collectors can be integrated into roofs or facades.


  • Renewable energy still dependent on the weather, season and place where you are. It is necessary to provide a non-intermittent heating system to take over day without sunshine.


  • Well suited to the domestic hot water or heating a home (average season).
  • Used for air conditioning with absorption systems (especially in very sunny countries and therefore very hot!)
  • Also usable for the production of electricity in mass of solar power concentrator.
  • Note that you can also use this principle “solar oven” (used for cooking).

Wind energy

Wind energy is a mechanical energy that can be captured in many ways. Simply with a sail, wind energy can be used to propel a sailboat. This first use dates back to antiquity. At that time, the wind was (with animal energy) one of the only propulsion sources. It is also the energy of the wind which made walking a part of the industry through windmills. The windmill blades use wind energy to spin a wheel that overwrites all that is possible to overwrite: cereals, oilseeds, etc. Then the industrial revolution in the 19th century has replaced the wind by other energy sources (coal, oil, gas, electricity).

Today the wind is again operated by more modern mills: windmills. There are two types of wind turbines:

  • Those who provide work, such as pumping water or turning a wheel. They are generally small. They are found in arid areas (Africa, USA, Australia, etc.).
  • Those that provide electricity (also known as wind turbines). They have very different sizes (from a few meters to 100 meters high). The smaller are used to power remote sites or private houses. The largest are often grouped in wind farms for mass production on the electricity grid (wind farms).


  • Energy available everywhere on the surface of our planet, especially in coastal areas, plains and hilly areas.
  • Requires a small footprint


  • Renewable energy still dependent on the wind. In isolated use, it is necessary to provide an electricity storage battery system for windless days.
  • Large wind turbines are huge and do not go unnoticed in the landscape.
  • Wind turbines are moving mechanical systems that require some maintenance (lubrication, cleaning blades), otherwise they lose their qualities.


  • Marine propulsion, pumping, power generation.
  • Provides scalability by wind farms.


The water cycle is an immutable natural background processes that takes place on the entire planet. The water of oceans, seas, lakes and rivers evaporates to go into the atmosphere, forming clouds and rain, snow or hail through which it falls to the ground. The engine of this great cycle is again … the sun. Indeed, it is the warmth that allows the evaporation of water from the soil and seas that will form the clouds.

But the water that falls on a mountain, before arriving in a sea or an ocean, must first form streams, rivers and finally rivers. The water speed (kinetic energy) of Rivie and rivers comes from the conversion of potential energy (due to altitude), as is the case for our champagne cork between points B and C ( see page 2). Going down to the sea, the water picks up speed and flows. The kinetic energy of the water depends on its speed but also its mass. Although the speed of the river water is not very large, their mass can be colossal. It is therefore possible to voloriser this energy by converting it either to mechanical energy (water mill) or electricity (hydroelectric dam).


  • As the river is not dry, energy is available. It is therefore a source of energy available enough (except in cases of persistent drought).


  • The biggest dams can drown very large areas, which may include residential areas (displacement). They can threaten local ecosystems (fauna and flora).
  • Dams can silt up because they reduce the flow of water but also of all elements chariés streams.
  • The released water (and more rarely the dam failure) can cause considerable damage downstream of the dam (tidal waves).


  • Over water: no dam but simply a roadway. Only a portion of the water of the river is used and the drop height is low. The production is continuous.
  • Retaining: a dam blocks any water and energy is released and converted to order.
  • The twenty-first century, especially power generation is privileged (hydro). Dams can also be used as energy storage (Energy Transfer Station by Pumping or STEP) and are used to balance the power grids.


The word means litérralement “heat of the earth.” In fact, the Earth is not an inert planet, like the Moon, but active. Volcanism, earthquakes, Earth Ecorse movement (plate tectonics), black smokers, geysers, all these earthly phenomena are explained by the fact that the center of our planet releases energy; a colossal energy when you consider the changes that can cause some of them. Often referred elsewhere cataclysms and natural disasters for more powerful, often pests.

The energy of the Earth has been known since antiquity and the hot springs were widely used at that time. Indeed, the heat of the Earth, when it reaches the earth’s crust can be heated groundwater. If this water has the opportunity to escape to the surface, she quietly deaf (hot spring) or it vaporizes and escapes violently (geysers). This underground heat can then be exploited either to heat buildings or to produce electricity. For it is dug deep wells by which either one captures the underground hot water is injected from the cold water, which is heated on the hot basement and is recovered by a second borehole.


  • As the amount of energy collected is not greater than the heat from the center of the Earth, the resource is inexhaustible.
  • This energy produces no waste.


  • Over-exploitation of a deposit brings the basement of the temperature drop which lowers the quality of the deposit to exhaustion.
  • There are risks of competition between the pumped water for its heat and water sometimes pumped itself (this is the case in Paris for example).
  • The deposits are located in some areas where terrestrial Ecorse lets spend heat (thin).


  • For small temperatures (low and medium energy of 30 to 150 ° C), heat is used directly for heating buildings. When the temperature is higher, we can use the energy to turn a turbine and generate electricity. In this case, it is geothermal power. We find this type of facility in the Philippines or Turkey for example.
  • In the case where the temperature is too low to heat the building, it is possible to use a heat pump. In this case, a part of the heating is made from electricity, and the other party by geothermal energy.
    (NOTE: I will present later the heat pump)
  • Heating “Geothermal says” that is sometimes proposed by some generally Heating captures its heat to a few tens of centimeters below ground. In this case, one can not speak of geothermal exacteement, since the heat collected is not from the center of the Earth, but the sun warms the ground. It is therefore a misnomer.


The term biomass refers to the mass of beings that live on Earth. But the energy called “biomass” actually comes from beings who have passed the bucket! In case, otherwise, we simply speak of animal energy.

Indeed, energy, as we have seen in the introduction of this file, is used by all living things. This is what distinguishes the inert mineral world. Every living exchange with the outside of the material (to form organs) and energy (to be able to act, that is to say, live).

The energy for a living may heat (to maintain its internal temperature) or chemical (for whatever is more complicated to operate and build organs). We check where chemical energy is nobler than the thermal energy, as we have already seen on page 4 of this issue.

Some living things, unsophisticated, do not have the “built-in heater”: they know not regulate their internal temperature and are therefore sensitive to changes in climate, cold in particular. This is the case of plants and a lot of animals called “cold-blooded” and “cold blood”, such as fish and reptiles. Those lucky enough to regulate their internal temperature are “warm-blooded” or “hot blood”, such as birds and mammals. They come to convert part of the chemical energy they have stored thermal energy for heating “from the inside”. (For more on this, see this page one, very informative)

The energy is stored by the living beings in the form of fats, sugars, or proteins. And we fall back on the famous calories from page 5! Biomass energy, we eat every day: it is even stated on the packaging!

But now let’s get serious. How to draw energy from apples, banana skins, dead branches and duck fat?

Today, three large product families biomass are operated:

  • Wood energy
  • Biogas
  • Agrofuels
  • Wood energy

Wood! This is an old story. Already at the time of the war of the fire, the wood was a strategic resource for heating and cooking. And if it was supplanted by coal and gas, oil or electricity, it is still a very good way to heat that has not been abandoned. Many countries still use large scale and in Europe, this is the first produced primary energy.

– But wood is it really a renewable source of energy?

– Yes, it is. You will find, as I do that when you cut a tree, it is possible to plant another instead. The resource is renewable precisely because we replanted after cutting. Otherwise, it’s called the mess and deforestation.

– Yes, but … and pollution? Smoke? CO2?

When one knows burning wood in a stove, fireplace or properly adjusted boiler pollution (soot, carbon monoxide) is relatively low. For CO2, it is more complicated: it is one of the inevitable products of combustion, the other being water.

– And the greenhouse effect then? It is not green, your thing!

– But think two seconds, please. What causes the increase of the greenhouse effect?

– Well, the CO2 being sent into the atmosphere. So your wood is not a good solution!

– Not so sure, my man! It is the CO2 being sent into the atmosphere but DO NOT COME TO THE ATMOSPHERE! In short, it is the one that comes and adds large carbon stocks that inexorably empty, as geological reserves of hydrocarbons. However, carbon wood that produces the CO2 is from where?

– Uh …?

– Exactly, it comes from the atmosphere. Green plants (we say more cleverly “chrolophylliennes”) such as trees, fix atmospheric CO2 through their leaves intermédiraire. So, just to plant a tree for it absorbs, during its growth, the CO2 emitted Whom burning his grandfather. And the circle is complete! When it runs in a loop, it is renewable.

– Not bad wood!


  • Wide availability of the resource on earth, except in desert areas where wood is scarce.
  • Low emissions and no contribution to the greenhouse effect.
  • The revival of its use in countries that were a little diverted leads to better management and optimization of woods and forests.
  • The price of firewood is not keeping oil prices.


  • It is a very dense energy source. For heating during winter will require a large amount of wood, which require a lot of transport, handling and ample storage space.
  • The exploitation of woods and forests must be accompanied by a new plantation. And must be reasoned because the forest is home to many plants and animals. Otherwise, it degrades the ecosystem and deteriorates the resource.


  • Today is exclusively for heating. In individual use, the wood will be used in fireplaces (preferably insert), mass stoves or boilers. In common use, it will be in these automatic boilers and heat networks.
  • Wood can be packaged in sticks, in chips or pellets.


In biofuels, there “agro” and there is “fuel”: these fuels (liquid) products from agricultural activities. That is, when you think about it, from agriculture, is known to produce very energy-rich substances such as sugar, alcohol or oil. With a little chemistry can be transformed into fuel that can be put in the tank of a car or a tractor.

Today, we produce three kinds of biofuels, classified by chemical family: vegetable oils, esters, alcohols.

  • Crude vegetable oils
    These are oils obtained from certain plants: rapeseed, sunflower, palm, jatropha. If you heat them, they burn. A small engine control and some adjustments are sufficient for that can be used directly, or mixed with petroleum fuels.
    You can also use the used frying oil. In this case, it is recycling and avoids throwing oil. So it’s very good for the environment (except maybe the smell of fried …)
  • Esters
    They are produced by a chemical process from rapeseed or soy oil. Then mixes the gas oil and it makes bio-diesel.
  • Alcohols
    They are produced from sugar crops: sugar cane, sugar beet, maize. By fermentation, sugar (or starch) into alcohol. This is called bio-ethanol. This biofuel can be used in a mixture in gasoline engines.


  • From agriculture, these fuels contain CO2 from the atmosphere. So there is no greenhouse effect caused by combustion.


  • Intensive agriculture, the source of biofuels, is harmful to the longer a security environment. It works through tractors, synthetic fertilizers and pesticides that damage the soil and do not respect nature. Pesticides are poisons kill insects, fungi, and plants which are then found in the soil, air and water. Fertilizers create imbalances and concentrate in groundwater (nitrates). We now know that agriculture is deadly and it will soon be completely changing agricultural practices.
  • On the other hand, the agriculture requires a lot of energy to power tractors, to produce fertilizers and pesticides, etc. so that the energy balance of biofuels production can be negative in some cases: more energy is consumed to produce than they release when used. In this case, it would be wiser not to produce them.
  • Cultivate fields to produce fuel when millions of people around the world have difficulty feeding poses an ethical issue. Should we not start by feeding the planet before feeding motor vehicles?
  • Competition uses plays on prices, which explains the crisis of 2007 maize in Mexico. Maize is a staple food in this country, but because of the demand for corn fuel prices shot up, causing riots.


Agriculture produces many things: vegetables and fruits, cereals, oilseeds, coffee, cocoa, sugar crops, fibrous plants for clothing (cotton, flax, hemp, etc.) as well animals of all kinds (cattle, sheep, goats, poultry, etc.). As explained above, plants capture the sun’s energy they use to grow, flower and bear fruit. And that’s because these plants are full of energy we eat and are nutritious.

But it does not always use the whole plant; there is therefore waste. Grind this waste pile them up, heat a little and that is enough to feed an army of … any bacteria. They transform this waste into natural fertilizers: compost. They also produce a toxic gas that smells bad but is full of energy called the “biogas”. It is a mixture of different gases, including methane, the main component of natural gas. So we can produce biogas almost everywhere where organic waste products: on farms, but also in landfills. The challenge is to collect and store the gas which is rapidly bulky.


  • Fairly easy to produce as occurs spontaneously in landfills.
  • Collect biogas prevents this greenhouse gas in the atmosphere parte.
  • Adds value to waste.


  • As all the gas, it is bulky. Storage and transport are difficult.
  • It smells bad and is toxic.


  • As biogas is not convenient to carry, it is best used where it is produced. Can burn to generate heat and optionally electricity.

Tidal energy

Twice a day, the level of seas, oceans (and even continents!) Rise and lower, in a slow oscillation. This is the tide, well-known people who live in the sea, as on the beach, the tide goes out and takes his place. This immutable oscillation is due to the rotation of the Earth on itself associated with the influence of the moon. The satellite of our planet is large enough to slightly distort the Earth. The height of the tide is often small (a few meters at most) but the amount of water raised is colossal! Because this form of renewable energy is potential energy, just as hydropower. To exploit it, was devised to make kinds of dams in the sea when it leaves the water of the tide (or down) drive turbines (called “bulbs” groups) that produce the electricity. It works, and yet there are very few plants of this type. In fact almost one in the world, located in Brittany, the Rance estuary.

The idea is very good but unfortunately there are very few places in the world where conditions are favorable for this type of installation. Often the tide is not strong enough and it does not worth to build a powerhouse for so little.

This solution is not ideal either, because the operation of the dam prevents water to clean the bottom of the sea, so that the top side of the dam tends to silt.

Price of solar panels

Solar house increasing value

Solar panels are of two types: photovoltaic produce electricity, heat and thermal.
The installation of a solar panel is often expensive. But it is an investment that quickly pays, through savings.

Solar panel price: a major investment

A solar panel, photovoltaic or thermal it is not an easy purchase. The initial investment is sometimes very important. It includes:

Transparent solar panels that can be used as a window!


The University of Michigan has developed fully transparent solar panels. They manage to generate electricity while letting light. Multiple applications are starting to emerge.

A technological revolution

Many works were held for the production of energy by luminescent materials, but the results were never very convincing so far. Today, the total transparency of the active luminescent layer suggests a multitude of possibilities for the future. Our lives every day will be much easier, no need battery charger for our laptop, our tablet, they will be recharged only with totally independent screens.
The best applications will be for the house with windows, bay windows that will produce your electricity, indoor fully heated through these coatings. This is not planned for the distant future but for tomorrow, for this year thanks to the research of the American researchers.

The photovoltaic panels


In parallel with solar panels that produce heat, photovoltaic panels generate electricity. However, the energy source remains the same. Indeed, photovoltaic panels need solar energy to produce electricity. Type of installation greatly reduces energy consumption. However, it is essential to know their operation and the place where they should be installed.

The operation of the panels

Photovoltaic solar panels operate through materials called semiconductors such as silicon. These materials are designed to absorb sunlight and convert it into electrical energy. This transformation is called the photovoltaic effect. Photons of sunlight bring electrons (silicon) in motion which generates electricity continuously.