Solar Power – Energy from the sun. As humans we need the sun to live. Our technology also “lives” largely from the sun. It’s a part of renewable energy sources for the future. Solar energy and wind energy are free to collect. They are always there to make a use for it.
Solar Power – Energy from the sun
The energy of the sun comes about through nuclear fusion. When hydrogen is converted into helium, a lot of energy is released. The sun is the energy source for geological processes on earth. Without it there would be no wind, there would be no water cycle, and no life would be possible. The amount of energy that the sun produces is gigantic. Every second there is enough free energy to provide the Europe with 50 million years of electricity.
The sun provides direct energy in two forms, light and heat. Energy from the sun is generated by the enormous pressure exerted on the core of the sun. These two forms of energy together with the secondary structures of energy, such as wind, tides, hydropower and biomass, make up 99.9% of the power on earth. The atmosphere and magnetosphere protect the earth against the most harmful radiation from the sun. However, the released energy that reaches us is still 9000 times greater than the needs of all earthlings combined.
In the nineteenth century, scientists had already determined that the sun consisted of helium and hydrogen gas. According to the German physicist Von Helmholtz, the sun is created because matter clumped from space under the influence of gravity. The heat that was released thereby caused the temperature to rise to fifteen million degrees Celsius. Von Helmholtz’s theory about the origin of the sun is still adhered to. But that theory does not explain why the sun still produces so much energy.
Which process ensures that the sun releases energy?
The answer came in 1938 from the American physicist Bethe. He stated that the power of the sun comes from nuclear fusion. In which two hydrogen atoms are combined into helium atoms. Of course, this process can not continue forever. At one point all hydrogen is converted into helium. Fortunately, we do not have to worry about that: the sun has fuel for a few billions of years.
When all the hydrogen is used up, a new phase in the life of the sun breaks up. The nuclear fusion is then not limited to the core of the sun, but also takes place in the outer regions. The sun then swells up to fifty times its current size and becomes a so-called red giant. That all happens in about six billion years. The earth will continue to exist, but with a temperature of about 1500 C life will no longer be possible.
What is sunlight energy
Sunlight consists of different colours that are absorbed to a greater or lesser extent by the solar cell. The size of absorption is determined by the semiconductor material used, from which a photovoltaic cell is built up. Such a material is not equally sensitive to all colours. Solar panels mainly use visible light (about 45% of the sunlight), light that we can observe with our eyes. Light consists of photons (= the light particles from solar radiation = energy packages) that determine the colour of the sun.
The photon must have a minimum amount of energy needed to release electrons in the semiconductor material. If the power is higher than the required minimum, the excess energy is published in the form of heat. Approximately 55% of the energy is lost in the light in this process. Then the electrons have the property to fall back to their old state. The theoretically possible conversion efficiency is therefore not higher than 20-30%.
At the moment, the very best small photovoltaic cells with an optimal colour sensitivity at laboratory level have a yield of at most 32%. The commercially produced solar cells currently have a return of between 6% and 16%. Amorphous silicon photovoltaic panels (thin film) have a yield of between 6% and 8%, mono-crystalline solar panels give 15% to 16%, and polycrystalline solar panels give an efficiency of approximately 14%.
Solar Power – Energy from the sun
Solar power is the most direct way to harvest the energy from the sun. We do this via solar panels and collectors. Wind energy is also not possible without the sun. The wind is created because it is warmer in one place than on the other. And that’s because of the sun.
Even water power depends on the sun. Hydropower plants use the flow or fall of water from top to bottom. Just as water mills used to do. But who brings the water up? That is the sun. Thanks to the heat of the sun, the water evaporates. The water rises and when the clouds cool down it rains or snows. That water flows down from the mountains again and there we build our hydropower plants.
Types of solar energy systems
PV panels convert sunlight into electricity (solar power). It is a readily applicable and environmentally friendly technique for generating electricity. Too much electricity generated can easily be supplied to the electricity grid. There are also more and more products on the market, in which solar cells are integrated into building materials, such as roofing, façade panels or roof tiles. Solar panels last 30 – 35 years. Generally, the solar panel manufacturers guarantee that the solar panels will still produce at least 80% of the original yield after 25 years.
There are two types:
- Autonomous systems: these systems are not connected to the grid, the electricity is supplied to a battery or directly to a device, for example, a pump or a vehicle to grid car. This involves direct current (DC = Direct Current).
- Network-connected systems: the electricity is supplied to the public electricity grid. To be able to do this, the direct current must first be converted into 230 volts alternating current (AC) using an inverter.
Portuguese sunlight is ideally suited to generate sustainable electricity. The sun delivers clean energy that never runs out. Solar panels convert that light into clean and free energy. Good for the climate and for your wallet.
A solar collector or solar water heater uses the energy of the sun to heat water that is used in the kitchen or in the bathroom. A solar water heater is an additional system on the boiler. The device is not used for heating a home. This requires a solar water heater combination. With a solar water heater you can save about 50% on the costs of heating your tap water. A third of your gas consumption is used for heating tap water. A solar water heater saves half of this. So you can calculate yourself what you can save on gas.
Hybrid solar panels:
With hybrid solar panels, you can generate both electricity and heat. They are particularly interesting when you have a small roof surface where you do not have enough space for a separate system (photovoltaic panels and collector independent). A very practical use is swimming pools. Thermal energy for heating the water and electrical power to run the pumps.
What are hybrid solar panels?
Hybrid solar panels, also called PVT (Photo Voltaic Thermal) panels, are solar panels that can generate both electricity and hot water. A hybrid system is, in fact, nothing more than a combination of a solar collector and a traditional solar panel. Hybrid solar panels can generate electricity efficiently. This has to do with the cooling of the panels that takes place through the collector section. Solar panels perform best when they do not get too hot.
In the summer, the temperature of a traditional solar panel can quickly rise to more than 75˚C, and that is not favourable for the efficiency. The electrical efficiency of a hybrid panel is better than that of a traditional solar panel, thanks to better cooling. However, the thermal efficiency of the collector section is somewhat lower compared to a conventional collector.
Solar Power – Energy from the sun
Electricity, light and heat are the most common practical use of the sun.
Germany, Spain and Portugal are investing in great solar energy industries. There are solar power plants. Huge installations of solar panels that generate electricity. Portugal has solar thermal plants. The word thermal indicates that they use the heat of the sun to eventually make electricity. The power plants consist of hollow mirrors that combine the sunlight to heat up liquid and develop steam. Turbines will be driven by the steam force. There are also solar thermal plants in Spain. Another name for it is Concentrated Solar Power plants.
A disadvantage of solar thermal plants (Concentrated Power plants) is that they require a lot of water to cool the steam in the turbine. Every 1,000 kWh costs 3 m3 of water, which can not be reused because it just evaporates.
Large-scale solar panels (‘solar parks’):
In Spain and Germany, large plants with thousands of square meters of photovoltaic panels have been built with a subsidy. The capacity of such solar projects amounts to more than 1 MWp (megawatt peak). One MWp is 1 million watt peak. In Portugal, more and more such large solar parks are now being built, from every Wp to dozens of MWp. The solar cell systems are arranged in rows or in a so-called tracker system. Trackers each contain 12 panels and rotate along with the position of the sun so that the light is always optimal.
Solar Power – Energy from the sun
Concentrated Solar Power plant with mirrors:
A Concentrated power plant is a solar thermal system that uses the heat of the sun. When you combine sunlight at one small point, the light energy concentrates and the temperature can rise quickly. This allows you to bring water to the boil, which produces steam. Steam power can drive a turbine again. That is in short how Concentrated Solar Power (CSP) works. Since electricity comes from heat and not from a photovoltaic reaction, it is called a solar thermal power plant. In Spain, for example, curved mirrors are in the form of a feeding trough. The mirrors direct sunlight on a pipe that is filled with thermal oil. The oil, therefore, becomes heated to more than 400 degrees Celsius. Through a heat exchanger, the oil transfers the heat to water, which starts to boil. The pressure created by the steam then drives a turbine, which finally produces electricity.
Concentrated solar power plants:
As with Concentrated Solar Power (CSP) plants, concentrated plants use light bundling to concentrate on a small surface. They do this with mirrors in the form of dishes. The difference with CSP is that electricity is generated by a photovoltaic reaction, not by heat. The mirrors reflect the light at a small collection point of specialised, highly efficient solar cells.
Larger energy yield with solar dishes:
With concentrated solar plants you can generate a lot of energy with a minimal panel surface. A 35-watt peak panel (35 kWp) requires a panel of only 0.23 m2. While a traditional system for the same power requires about 350 m2 of solar cells. Each photovoltaic panel has its own cooling. The efficiency of light conversion to electricity decreases rapidly as the cells warm up.
Concentrated solar projects plants have a capacity between a 10-megawatt peak (10 million watt peak) and some gigawatt peak (1-gigawatt peak is 1 billion watt peak).
Solar Power – Energy from the sun
- Saving or balancing solar power:
More and more households generate electricity with solar panels themselves. The feed in tariffs are an important rol for youre investment. But in that way you are doing well for the environment, because energy from the sun is clean and sustainable. But the sun only shines during the day, while you also use electricity in the evening. Fortunately, you can return power that you do not use during the day to the power supply. You will receive compensation for this.
- Store in water:
In Lagos Algarve a trial with 200 households is running under the name ‘City of the Sun’, which immediately converts energy with a new technique. By, for example, heating up water during the day and using it at night, the residents deal more efficiently with their self-generated energy. The nice thing is that they do not have to do anything for it. The equipment itself will figure out what the best way is to ‘park’ the energy and to retrieve it.
- Store in batteries:
Car manufacturers have been experimenting for years with batteries to drive electric cars. The same technique can also be used at home to store electricity. There are a few drawbacks here. For example, the capacity of the batteries is somewhat limited. Moreover, they are still quite expensive. Also, its production and the final processing of the battery (when it breaks down for example) is damaging to the environment. Scientist try to improve this technique every day. Sometimes they break through.
Not all the sunlight can be used to generate solar energy. The materials from which photovoltaic cells are made reflect or absorb a large part of the light. As a result, a commercial solar panel now has an efficiency of about 18%, so only about one-sixth of all the light that reaches the panel. Improving the efficiency is one of the areas that energy researchers are now focusing on. The progress in efficiency that has already been achieved is impressive. The first photovoltaic cells, built in the fifties, had an efficiency of only 4%, or less.
The different forms of solar energy offer many applications. In principle, it is possible to get all the energy that you use at home (electricity and heating) from the sun! In the Algarve portugal it is commen to heat up swimming pools.
The ongoing innovation in the sustainable energy sector and the fact that it is competitive with energy from fossil fuels, it is expected that the share of solar power will continue to grow strongly.
Up to the horizon solar panels that rotate with the sun, or hollow mirrors that power steam engines. Such solar power stations already exist in Europe. Energy from the sun is the future!