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We sponsor CPV-9 congress. Japan, 15 – 17 April.

SAV is to participate and sponsor the most important international conference in the CPV industry.

CPV-9.

The conference will take place in Miyazaki, Japan from 15th to 18th April, where SAV will make the most of the opportunity to present its products and services. Visit www.cpv-9.org for further information about the conference.

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Calibration

Our engineering department offers calibration services to the CPV industry. We will provide traceable calibration certificates to allow the following devices to be used as customized references specific to tests and measurements of different CPV technologies.

  • CPV Monomodules: Composed of a single set of concentrating optics and solar cell, these devices are very useful for validating prototype designs, for serving as a reference for solar simulators such as the Helios 3198, as well as for outdoor measurements when a primary reference is not available.
  • CPV Receivers and CoCs: We can provide a traceable reference for use with our Helios 3030-XX line of CPV component testers.
  • CPV Modules: We can offer power measurements under highly controlled conditions to create calibrated control modules to increase the traceability of both indoor and outdoor measurements.
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SAV at “CPV International 2013”

SAV team attended the 4th international conference on CPV commercialization which took place in Madrid on 21st and 22nd March.

Important international companies from the sector participated and the main topics included the different possibilities the CPV industry faces for commercial expansion in different parts of the world.

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CPV Design

We offer a range of technical product development services in the CPV area including:

  • Measurement and quality control consulting.
  • Assessment and optimization of CPV designs.
  • Evaluation and selection of component suppliers.
  • Assistance with the industrialization of existing products.
  • Turn-key solutions for CPV components, optics, and modules.

We leverage both the deep experience of our technical team in concentration, solar cells, optics, test, and mechanical systems, as well as our technical alliance with IES-UPM, in order to provide you with fast and rapid solutions and access to the technical experts in diverse fields.

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Concentrated Photovoltaics (CPV)

Amongst the various different photovoltaic technologies, the latest at present is concentrated photovoltaic, commonly known as CPV.

The great scientific and commercial interest that this technology has provoked is mainly thanks to the high yield offered by these installations in terms of energy produced particularly in areas of high irradiation. but also because of its great potential for reducing costs when compared not only with other solar technologies but also with other sources of renewable energy.  These characteristics could make CPV the most widely used solar energy vector for large generating plants in the future.

Solar Added Value has a high degree of technical specialization in the understanding of CPV technology, and its function principles of which are described within here.

 

The functioning principles of CPV technology

Concentrated photovoltaic modules are capable of collecting solar radiation and increasing its power density (measured in W/m2) by the use of lenses in order to focus it on a much smaller solar cell than the one in the collector entrance area.

The interest in this kind of technology stems from the fact that high efficiency solar cells (> 40%) are already commercially available. Whilst expensive this allows the impact of the overall cost of the system to be reduced by use of the optical devices mentioned and capable of intensifying up to 1300 times the irradiation (W/m²) coming from the sun. Thus, allowing the semi-conductor area required to be minimized, as shown in the diagram.

Concentrated Photovoltaics principle by use of a refractive lens.

Concentrated Photovoltaics principle by use of a refractive lens.

The increase in energy intensity created on the cells by the use of the optical elements inevitably leads to the narrowing of the numerical aperture of the rays of light which means that only direct sunlight can be used – with an approximate tolerance of ±1º. Therefore, double axis tracking systems are essential in the BOS.

 

Basic characteristic elements of CPV systems

Type of cells

CPV modules normally use multi-junction (MJ) cells. These cells are actually comprised of several solar cells, called sub-cells, connected in series and made of different semi-conductor materials. The advantage of this configuration is that it allows for greater use of energy from the photons present in the solar spectrum, thus providing the system with a higher degree of conversion of light into DC electricity.

Moreover MJ cells can be designed and specifically calibrated for a determined spectrum in order to make the photovoltaic conversion even more efficient. Currently, the most used MJ cells are the  triple-junction ones which normally offer an efficiency rate conversion of more than 40%, much greater than any other commercially known PV technologies and as shown in the graph.

Efficiency rates reached by photovoltaic cells as per type. Source: NREL, USA.

Efficiency rates reached by photovoltaic cells as per type.
Source: NREL, USA.

 

Use of optical elements

Lenses used in the CPV industry can be either reflexives (mirrors) or refractive (Fresnel lenses) and these elements are usually referred to as “primary lens”.

Different SOE designs mounted on MJ cells.

Different SOE designs mounted on MJ cells.

At the same time, the system usually also has a second optical element (secondary lens or SOE) which is attached  onto the cell. Its mission, amongst others, being to increase the numerical aperture of the set whilst at the same time ensuring a uniform distribution of the energy from the cell, which prevents the generating of hot spots on it.

 

Double axis tracking elements.

As previously explained, CPV systems only use solar resources coming from direct sunlight (the one with greatest energy), which means that their modules require the installation of double axis tracking collectors.

For a conventional CPV module, the value of the numerical aperture usually ranges between 0.7º and 1.2º. This value must be taken into account when designing or selecting the kind of tracker to be used. Currently there are sufficient precise tracking devices to guarantee this requirement, allowing the modules to be correctly orientated even with heavy loads.

Double axis tracker and tracking device with heavy load CPV modules.

Double axis tracker and tracking device with heavy load CPV modules.

Independently from the type of cell, it is evident that most of the characteristic elements defining CPV technology (optics, trackers, tracking devices and motorization, etc.) have already been used in other sectors, such as the car industry, IT or the aerospace industry, which means that it is relatively simple to bring about significant improvements by optimising the way in which they are used together. The fact is that there are important R&D centres researching into the optimization of this technology. In addition there are important companies already making CPV installations worldwide. These facts allow us to conclude that CPV technology will continue to acquire particular importance in the next few decades in the electrical sector and more precisely in the sector of renewable energies.

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Photovoltaic Solar Energy

Definition and History

Photovoltaic is a method that generates electrical direct current (DC) by means of the use of a semi-conductor element when it is lit by a photon beam from the sun.

In photovoltaic applications, solar cells, which are the semiconductor elements, are interconnected and encapsulated in the so-called photovoltaic modules, so as to provide the cells with greater durability, resistance and insulation. Thus functioning over a long term period is guaranteed, usually between 20 to 25 years, with a production rate of more than 85% of the initial nominal power.

In order to build the whole system in the solar plant additional elements are needed. The invertor, the batteries, the structures where the modules are mounted on (fixed, single axis or double axis tracking) as well as the other elements required to build the plant (cables, protection, transformers, etc.) is usually called “Balance of System” (BOS).

Photovoltaic plant with Polycrystalline Silicon panels installed on non-tracked support structures

Photovoltaic plant with Polycrystalline Silicon panels installed on non-tracked support structures. Source: Institute of Solar Energy.

On a historic note, it should be mentioned that the photovoltaic effect was discovered as far back as 1839 by Becqueler, although the first silicon cell was not developed until 1954 at Bell Laboratories in the USA. In the 60’s the fundamental theory of the solar cell began to be developed with regards to all the most relevant aspects known to date and which characterize each of the solar technologies existing today, such as: materials, radiation spectrum, thermodynamics and efficiency. ars, with a production rate of more than 85% of the initial nominal power.

 

Types of Photovoltaics Technologies

Basically depending on the type of cell selected, we can classify photovoltaic technologies into different subgroups, whose characteristics will have a greater or lesser impact on the configuration of the BOS.

Without going into great detail the technologies commercially available at present are as follows (listed in decreasing order as per number of MW installed worldwide):

Monocrystalline and Polycrystalline Silicon

Monocrystalline Silicon before cutting

Monocrystalline Silicon before cutting

These represent almost 90% of the photovoltaic installations that exist worldwide at present. They are characterised by the ease of installation although the ratio of efficiency of the panels is not normally higher than 20%. In terms of BOS, they can be installed as either fixed structures or mounted trackers. At present, they are extensively used but the large area of cells required per square metre of installation along with the need to use many other auxiliary materials for the production of the module means that its potential for reducing costs is limited.

Thin Film

This technology is mainly based on the use of cells made from amorphous silicon, cadmium telluride (CdTe), CIGS (flexible cells) and other semiconductor materials. They are normally characterised by low efficiency rates of around 10%, which means they are not suitable for use in areas of medium and high irradiation but are appropriate for areas with low levels of irradiation. They generally need a large area for installation although the manufacturing costs are low. One of the main disadvantages is that the initial investment for production plants is the highest of all the systems described here.

Concentrated Photovoltaics (CPV)

Normally based on the use of multi-junction (MJ) cells, this is the photovoltaic technology and the one most recently commercially applied for in-land solar farms installations (it was already in use in the aerospace industry). In general, it uses optical devices to concentrate light and thus reduce the high cost of MJ cells, which means that the BOS needs to necessarily include double axis tracking. Its high yield (panels achieve efficiency of over 30% nowadays but it is believed that in the future they may reach around 40-50%) makes it ideal for the generating of electricity in large plants located in areas with a high degree of solar radiation and at the same time presents this technology as having a greater potential for reducing costs.

Installation of a photovoltaic plant with CPV modules and single post type double tracking. Source: ISFOC.

Installation of a photovoltaic plant with CPV modules and single post type double tracking.
Source: ISFOC.

From the outset, most of the efforts have been concentrated on achieving the most efficient conversion cells (difference between energy from the sun and energy generated by the device) in such as way as to ensure the modules achieve the greatest amount of energy with the lowest possible manufacturing costs. Therefore, from a more commercial point of view, modules are generally classified not only in terms of conversion efficiency but also in terms of the €/Wp ratio, where the watt peak (Wp) is the power which a module provides for a perfectly adapted load when the light proceeding from 1 kW/m² and a determined spectrum fall on it whilst the cells are maintained at 25ºC.

Once the panels have been installed, the most important parameter at plant level is the production of energy in terms of Kw/h/m², which indicates the level of electricity produced per hour and aside from the technology and configuration of the BOS will also depend on the amount of solar resources available at each location.

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Due Diligence

SAV offers technical due diligence services for photovoltaic power plants, particularly for those using CPV technology. Independent evaluation of the technical specifications and functional conditions of a PV plant is essential in order to be able to assess its production capacisty. Our services include:

  • In situ measurement of plant performance.
  • Calculation of plant performance and prediction of yearly production.
  • Analysis of deviations from predicted performance and recommendations for corrective measures.

These services are intended not only for CPV producers but for investors in CPV.

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Welcome

Solar Added Value is a technological company focusing its activities in the solar sector and already being an international reference company within the Concentrated Photovoltaic Sector.

Our team is made up of technical professionals, in the main engineers, highly expertise at developing research projects for the application of innovating products and solutions within photovoltaics.

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Training

We organize custom training course in concentration photovoltaics, covering both general theory as well as the highly technical aspects of CPV characterization. Although we include training services with the sales of all of our solar simulators, additional on-going training can help your team to maximize the usefulness of SAV testers.

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Software Design

Our experience in test software development for our own products allows us to offer software design services in order to develop custom software solutions in order to build on the functions of our existing products or for other purposes.

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Custom Test Devices

Our R&D department is ready to assist you to provide you with custom CPV characterization solutions that meet your needs. Because our measurement products are highly adaptable, these systems can often be integrated into these custom solutions, speeding development time.