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Solar Wiring

Cables, both direct current (DC) and alternating current (AC), if correctly sized, will minimize energy losses and protect the installation.

For a photovoltaic system, DC cables must meet some requirements:

* Have grounding line and protection against short circuit.
* Be resistant to UV rays and adverse weather conditions with a wide range of temperatures (approximately between -40ºC and 110ºC).
* Possess a wide voltage range (more than 2000 V).
* Be simple and easy to manipulate.
* Be non-flammable, of low toxic level in case of fire and without halogens.
* Have a very low conduction loss (up to 1%).

Photovoltaic installation cables must have certain characteristics that differentiate them from conventional cables, although many argue that differences are not very large.

Since voltage in a photovoltaic system is low DC voltage, 12 or 24 V, currents that will flow through the cables are much higher than those in systems with 110 or 220 V AC voltage.

Power amount in Watts produced by the battery or photovoltaic panel is given by the following formula: P = V. I

V = voltage in Volts
I = current in Amperes

This means that to supply a power at 12 V current will be almost 20 times higher than in a 220 V system. It implies that much thicker cables must be attached to prevent overheating or even a fire.

Following table indicates recommended cable section according to power and for different voltage levels.

For very low voltages and low power demands, very thick cables must be used. For example, to reach a power of approximately 1 Kw at 12 V we would need a 25 mm2 section cable. The same as to supply 20 Kw at 220 V.

This increases system price drastically because thicker cables are more expensive.

That is why it is very important that the lengths of DC wiring are as short as possible.

When designing large systems, a cost / performance analysis must be performed to choose most suitable operating voltage. It would be advisable to gather small groups of modules and if possible to make operating voltage higher than 12 or 24 V.

To verify cable section values recommended in tables, maximum voltage drops compared to voltage at which you are working should be below the 3% / 5% limit.

To calculate the relationship between conductor section and its length we can apply following formula:

S = 2 r. l. i / ΔV

Being:

r Conductive material resistivity (0.018 in case of copper conductors)
l Cable section length
i Current intensity
ΔV Voltmeter reading difference

Let’s see an example:

Battery terminals output voltage is 13.1 V. The main line between it and a device, which consumes 60 W, measures 12 m of 6 mm2 cable.

We must find the voltage value at device input to verify that we are within maximum recommended values of voltage drop.

The intensity i = P / V = 60 / 13.1 = 4.6 A

S = 6 = 2. 0.018. 12 4.6 / ΔV

ΔV = 0.33 V

Therefore, voltage at device input will be: 13.1 – 0.33 = 12.8 V

Voltage drop is 2.34% (maximum recommended value: 3%).

It is normal to use tables to select recommended section and use the formula to calculate the voltage drop and perform the verification.

In case that voltage recommended maximum values drop are exceeded, we will select section immediately above and we will carry out verification again.

Cables for photovoltaic applications have a designation, according to regulations, which is composed of a set of letters and numbers, each with a meaning.

Cables designation refers to a series of characteristics (construction materials, nominal voltages, etc.) that facilitate the selection of the most suitable to the need or application.

This is an extract of contents included in Technical-Commercial Photovoltaic Solar Energy Manual and Sopelia e-learning training.

All you need is Sun. All you need is Sopelia.

Heat Transfer Fluid

Heat transfer fluid passes through absorber and transfers energy to thermal utilization system (accumulator or exchanger).

Most used types are:

* Natural water: can be used in open circuit, when sanitary water passes directly through collectors, or in closed circuit (independent consumption circuit).

In first case, circuit can only be constituted by materials allowed for drinking water supply. In some countries this system is not allowed.

It will be necessary to consider water characteristics, especially its hardness (calcium and magnesium amount), which when heated produces a hard crust or tartar.

This crust accelerates corrosion, restricts flow and reduces heat transfer. The values start to be problematic from 60 mg / l. Very soft waters can also cause problems due to their corrosivity.

* Water with antifreeze: to avoid drawbacks of freezing and boiling of heat transfer fluid, use of antifreezes called “glycols” is the most widespread.

Mixed with water in certain proportions prevent freezing to a limit of temperatures below 0 ° C depending on their concentration.

On the other hand the boiling point rises making heat transfer is protected against too high temperatures.

Choice of concentration will depend on historical temperatures of the area where installation is located and on characteristics provided by manufacturer.

Most commonly used glycols are ethylene glycol and propylene glicol.

Resultado de imagen de tabla anticongelante solar

Fundamental characteristics of antifreeze:

• They are toxic: their mixing with drinking water must be prevented by making secondary circuit pressure greater than that of primary, for prevention exchanger possible breakage.

• They are very viscous: factor to take into account when choosing electric pump that is usually more powerful.

• Dilates more than water when heated: as a safety standard, when we use antifreeze in proportions of up to 30%, when sizing the expansion vessel, we will apply a coefficient of 1.1 and 1.2 if proportion is greater.

• It is unstable at more than 120ºC: it loses its properties so it stops avoiding freezing. There are some that withstand higher temperatures, but they are expensive.

• The boiling temperature is higher than that of water alone, but not too much.

• Specific heat is lower than that of water alone, so it must be taken into account in the flow calculation, conditioning pipe and pump dimensioning.

To calculate antifreeze amount that must be added to an installation, you must first consult the table of historical temperatures which is the minimum temperature recorded in that city or location.

Once it is known, goes to glycols graph supplied by manufacturer and value is transferred to indicate what percentage is.

* Organics fluids: there are two types, synthetic and petroleum derivatives.
Precautions mentioned in case of antifreeze regarding toxicity, viscosity and dilation are applicable to organic fluids. Additional risk of fire should be mentioned, but also that they are chemically stable at elevated temperatures.

* Silicone oils: they are stable and of good quality products. They have the advantages that they are not toxic and that they are not flammable, but current high prices mean they are not widely used.

All you need is Sun. All you need is Sopelia.

Solar Energy Wherever You Are

Many times the purpose of incorporating solar energy to our professional skills, scope of business or personal life has hovered in our head.

We have almost always run into the same barrier: time.

We are working or studying and we find it very difficult to have even a few hours a week.

It is rare to find training offerings that are not too short (few hours workshops) or too long (one or more years) and which in turn have an affordable price.

If we add the difficulty of having to move, because most are taught in presence way, finally we ended up postponing again and again this purpose.

In 2014 Sopelia gave, in collaboration with the Technology National University of Mar del Plata (Argentina), the Technical – Commercial Solar Energy Course in tele-learning (distance + presence) methodology.

In 2016 Sopelia updated and divided that training action in 2 specific courses:

* Technical – Commercial Solar Thermal Energy

* Technical – Commercial Photovoltaic Solar Energy

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Sopelia rode them on a Moodle 3.1 platform and the result is 2 courses in e-learning methodology.

This means you can receive Solar Energy training with the best market value wherever you are.

You only need a computer, smartphone or mobile device and Internet.

Being the 1st edition there is a 50% off list price.

These two courses provide technical and commercial training in solar energy domestic applications with the aim of spreading the technology and develop human resources for incorporation into work and business world.

You will identify the most relevant aspects of solar energy within the current energy landscape.

You will define, describe and analyze the most important features of solar energy.

You will know the composition, understand the operation, design and maintenance of facilities to implement thermal and photovoltaic solar energy projects.

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It is a training aimed at students and technical careers graduates, technical schools graduates, engineers, architects, professionals and installers of related sectors (air conditioning, electricity, rural), people with experience in renewable energies, environmental professionals and individuals interested in incorporating solar energy into their lives.

The 2016 edition starts on September 19th and ends on November 25th.

You can register until 16 September inclusive in www.energiasrenovables.lat

If you are under 30 years old and live in Latin America, with the course completed, you can apply to be Sopelia Country Manager in your country of residence.

And if you are under 25 and live in Latin America, you can get a 50% scholarship and finished the course, apply to become Sopelia Trainee.

If you speak Spanish you have no excuses, Solar Energy wherever you are with Sopelia.

Solar PV Latin America

Latin America generates about 7% of the world’s electricity and non-traditional sources account only for 6% of the energy mix.

It is expected that by 2050 over 20% of the electricity generated in the region will come from non-hydro renewables.

May the contribution of photovoltaics be significant?

This technology has great potential in the region, but is still marginalized to the background among the countries’ energy choices and many times what is done about it is just to “stand” and very little is accomplished.

Compared to the rest of the world, the rate of solar photovoltaic energy implementation in Latin America is very low.

Annually the installation of about 100 GW of solar photovoltaic energy is expected worldwide and usually only 1% corresponds to this region.

However, the fact of not having been one of the pioneer regions where the development of this technology began will allow learning from other regions or countries mistakes.

We must distinguish between solar industrial development (manufacturing of modules and other components) and solar energy (solar electricity).

Solar industrial development in the region has difficulties with the sharp drop in solar modules’ prices.

In contrast, solar electricity production is favored by the fall in modules prices and makes solar photovoltaic energy more competitive.

The average cost of 1 W of installed solar PV has dramatically dropped in recent years and most projections indicate that this trend will continue. The underlying costs associated with solar photovoltaic energy will also continue to decline.

PV installed capacity of Latin American countries has always been oriented to isolated applications to meet the needs of rural populations without access to electricity network.

Only after 2014 solar photovoltaic projects began to attract capital.

Latin America has 51 solar photovoltaic plants in operation and 625 MW of installed PV in 2014, compared to 133 MW in 2013. They have announced 23 GW projects, 5,2 GW in contracts, 1,1 GW under construction and 722 MW in operation.

From GTM Research consultancy recent studies show that the installed capacity in MW has increased 370% in 2014 and is expected to rise 237% in 2015.

This figure could be revised downwards following the price collapse that has rocked the oil industry and the commodity sector in recent months.

Today, in Latin American countries with good levels of radiation and without large subsidies in the energy market, the model of solar PV is self-sustaining.

In some cities in Mexico, Brazil, Chile and Peru, the solar PV cost is situated very close to grid parity.

Countries like Costa Rica, Guatemala, Mexico, Panama, Dominican Republic and Uruguay already have national laws and regulations in place for connecting photovoltaic generators under the net metering system.

The most suitable places to locate large plants are the deserts near the Pacific coast and northeastern Brazil.

Over the next 20 years it is expected that the investment in solar photovoltaic energy per year will reach about U$S 100.000 million worldwide.

A forecasted development of 3,5 GW is estimated in Latin America by 2016.

Could this be possible?

To know it, we are going to do a country-by-country analysis because there are very different realities.

Solar Thermal Latin America

Solar thermal energy for domestic applications is a mature technology that has been successfully developed in many countries for over 30 years.

It is not well understood why its underdeveloped compared with photovoltaics while almost double its performance.

It is a relatively simple technology that already has small and medium manufacturers in countries of the region such as Argentina, Uruguay and Brazil. However, there is still no certification at regional level as in Europe.

In the Caribbean nation of Barbados 80% – 90% of households have solar energy equipment on their roofs. This country ranks in the top 5 global installed capacity per capita.

There are no reliable data concerning the installed capacity in Latin America.

The most recent global estimate dating from 2012 and informs an installed capacity of 234 GWth. Brazil is among the top 7 countries with about 4 GWth (2%).

The Latin American regional market is slowly developing.

In parallel, there is an emerging incipient regulatory framework for certifications that are mainly based on regulatory frameworks of Europe and the US. COPANT is working on the unification of the regional framework of standards and certifications.

One of the main barriers to the development of solar thermal energy are important subsidies that some countries in the region granted to conventional energy.

Professionals and companies in the solar energy industry of Latin America and the Caribbean met recently in San Jose, Costa Rica, to promote the development of this technology in the region.

The meeting was made by IRENA (International Renewable Energy Agency), OLADE (Latin American Energy Organization), ICE (Instituto Costarricense de Electricidad) and the German Metrology Institute (PTB).

According to the Innovation and Technology Department of IRENA, currently the region only takes advantage of 3% of its solar thermal potential.

The most important conclusión we arrived is that the region has great potential for development of solar energy in residential and commercial areas, but experience shows that to achieve this, we must build confidence in this technology.

How is this achieved ?

Proposals were:

1) Develop mechanisms to ensure the quality of the facilities (standards and inspections)

2) Encourage best practices among professionals and companies (testing and certification)

3) Implement government policies that promote genuine development of this technology

The global analysis of the development programs of solar thermal energy estimates a worldwide installed capacity of 1,600 GWth in 2030 and 3,500 in 2050 GWth.

Will be Latin America an important player in this global installed capacity growing ?

To know that, in next deliveries we will discuss solar thermal sector of each country in the region.

Solar Energy in Latin America

Before evaluating the solar potential of the region, we will expose some macro variables.

Latin America includes Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Cuba, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Dominican Republic, Uruguay and Venezuela.

It has 22.222.000 km2 (approximately 13.5% of the planet’s land surface) and more than 600 million inhabitants.

The region has a remarkable political and economic diversity and is unstable because of the continued monetary policy focus shift.

Currently, in Latin America 3 types of economic systems are recognized.

The capitalists, with open economies that rely on the free market and free trade agreements. Some of these countries are Peru, Chile, Mexico, Colombia, Panama and Costa Rica.

Countries that, even though argue having an open structure to the world, are clearly protectionists, with a social market or mixed economy. Some of these countries are Argentina, Uruguay, Brazil, Ecuador, Bolivia and Paraguay.

Finally there are a few countries that maintain closed economies with little regard for free market and with a clear tendency to Marxist models. This is the case of Cuba, Venezuela and Nicaragua.

The largest economies by GDP are Brazil, Mexico, Argentina, Colombia and Venezuela.

The most developed in terms of GDP per capita are Chile, Argentina and Uruguay’s economies.

Let us analyze the solar resource available in the region.

Solar energy is evenly distributed, since much of the region lies within the so called ‘Sun Belt’ region presenting the highest solar radiation; with the exception of specific sites, it is a predictable and reliable resource.

What is the main advantage of solar energy over other renewable energies?

Solar energy has a higher degree of integration into the urban environment.

Roof facilities take advantage of idle surfaces to generate clean energy. The country that manages to focus its efforts on such facilities’ development will have the key to its own, and its inhabitants’, energy sovereignty.

Another important factor is that solar installations can be performed by local workers, reducing dependency on technology developers and equipment suppliers (mostly manufactured outside the region). This eliminates the link between the equipment’s sale, installation, commissioning, operation and maintenance; unlike it happens with other renewables.

With some of the best solar resources in the world, Latin America has great opportunities.

Some reasons to be optimistic:

1. Good levels of solar radiation in the region

2. Sustained downward trend in solar systems components’ prices

3. Technology with high potential for generating local employment

4. Increasing public environmental awareness

5. Convenience for many countries to reduce dependence on oil and its derivatives

6. Political will is evidenced by governments of some countries in the region

And some outstanding issues:

1- Investment in modern interconnected transmission networks infrastructure and bidirectional measurement equipment

2- A larger financial market to support solar technology long-term development with loans

3- Legal uncertainty and economic instability in some countries of the region

In upcoming deliveries we will analyze the thermal and photovoltaic solar energy domestic applications’ situation in the region.