Victron Energy Solar Systems and Schrack Technik from Zagreb

Victron Energy photovoltaics and solar systems

Photovoltaic (PV, Eng. Photovoltaics, PV) is a solar power technology that uses solar cells to convert solar energy into electricity. One of the world’s best manufacturers is a Dutch company called Victron Energy and its components can be obtained, alongside the full project, at Schrack Technik d.o.o. in Zagreb. Important materials for making photovoltaic solar cell can be present as a single crystal, poly-crystal or amorphous substance. Classic semiconductor that is used for solar cell silicon, and other materials. Solar cell is essentially a PN junction (semiconductor diode). When the solar cell lights up, absorbed photons produce electron-hole pairs for which there is a potential difference at the ends of the solar cell. If contacts cells connected to an external consumer and will pass an electric current, a solar cell becomes a source of electricity. Solar PV power plant consists of PV panels connected in fields connected to the network via heat or consumers. They can be independent and connected to the network. Stand-alone solutions in the developed world now make up only about 5% of the total installation and next PV panel still have batteries, two-way inverters and are often combined with other sources. PV panel represents independent elements whose power ranges from 50W to 300W. One PV panel consists of more crystalline PV cell or a cell in the thin film. Fields can be placed on a fixed or movable mechanisms to achieve greater production of electricity by monitoring the movement of the sun. Fixed installation is typically at the optimum angle for maximum annual production. Mobile solutions can have a 20-30% higher production of electricity depending on the version (1-axis and 2-axis) and total radiation, with the higher price of installation and maintenance costs. Network System (Grid-Connected) The network is connected to the public network via a home installation. Electricity from photovoltaic systems primarily supplies family house consumers, and the excess electricity produced can be sold to the public network. Electric system performs the function of storing energy. In the event that the photovoltaic modules do not produce enough electricity, power loads complemented by taking over power from the grid. You can check Victron Energy Hrvatska, its components and parts and the offer at schrack.hr on-line store.

Photovoltaic modules and main components

1. mounting elements
2. cables
3. junction box with protective equipment
4. Victron Energy exchanger DC/AC (inverter) – solar inverter converts direct current into alternating module, synchronized with the voltage and frequency of the network.
5. counter sales and purchases of energy – Registers generated energy to the grid and consumed energy taken from the grid.
6. connection to network – The systems are generally connected to the low voltage level of the power system.
7. each type of cell is suitable for network and stand-alone system, or network system is mainly used by crystalline silicon cells. When connecting to the grid PV power plants must comply with technical regulations as defined by the distribution companies. The regulations generally require protective measures relating to security and the impact on the operation of the network. The rules and standards for connection are still under development and each country (and distribution) has its own peculiarities.

Experience in the Republic of Croatia are in their infancy and the Croatian Electricity Company (HEP) is still evolving approach to connecting distributed sources. Administrative obstacles to obtaining the status of eligible producers are certainly more than the difficulties of interconnection.

Off-grid systems (Eng. Stand-Alone-Systems or Off-Grid)

Solar photovoltaic (PV) systems that are not connected to the network (isolated or stand-alone systems) are commonly used in places where there is no electricity network or where the construction of the electrical network is not cost-effective. Often these are small settlements and the difficult and inaccessible areas with poorly developed infrastructure (for example the use of such systems can be cottages). In Croatia, the implementation of island photovoltaic systems particularly interesting on the islands or in the mountains (isolated houses, cottages and mountain huts). Off-grid systems provide the user with a complete energy independence.

Off-grid photovoltaic systems can be with or without energy storage, which will depend on the type of application and power consumption mode, and the hybrid system.

Hybrid systems combine solar photovoltaic systems with cogeneration, fuel cell, wind turbine, or most commonly, a generator on diesel or biodiesel fuel (diesel engine). In such system of electricity produced solar modules or other sources of system, primarily supplies the consumers, and the excess energy full solar batteries. In the event that the conditions for the production of electricity are not met, the source of power loads the battery. Only if neither the battery no longer has the energy to power the load, generator on diesel or biodiesel fuel is included. In general, each type of cell is suitable for network and stand-alone system.

Types cells and their technology

Monocrystalline solar panels

Classic semiconductor that is used for solar cell silicon. Monocrystalline solar cells with high efficiency (about 16 percent), which provides a high-energy yield with compact dimensions. Because of the aforementioned characteristics, recommended its use for roof installation, which should realize a high power to a limited area. The modules are best suited when it is clear weather with plenty of sunshine. Monocrystalline modules have a long service life (over 20 years), but the production of demanding, therefore the modules of higher prices. Area monocrystalline module is monochrome dark and shows rectangular shape of the cell. Efficiency (serial production): About 16 percent. The average area requirement for the supply of family homes with electricity (5,000 kWh / a): ~ 31m². Main areas of application: Roof installation on a limited area

Polycrystalline solar panels

The difference between the single-crystal and polycrystalline modules in the molecular structure of the active crystal. Production of crystal cell is less demanding and thus are more favorable than monocrystalline modules. The efficiency of polycrystalline cells is around 15 percent, which is lower compared with the single crystal modules and therefore need more space for modules. Polycrystalline modules are equally favorable life and areas of application are similar to those of single crystals. Polycrystalline solar modules are the most used and best suited as when clear weather. This type of cell provides bluish, marble image. Efficiency (serial production): About 15%.

The average area requirement for the supply of family homes with electricity (5,000 kWh / a): ~ 33m² Main areas of application: Roof installation

Thin-film cells

The amorphous solar modules If you use a thin film of amorphous silicon that is called amorphous or thin layer cell. In amorphous materials, the atoms have an irregular structure, and amorphous materials have a lower density of crystal. Unlike crystalline silicon cells, silicon is not applied in the liquid state than in the vapor phase. Thus, the layer thickness is 100 times less than that of mono- or polycrystalline cells, so production costs are lower in line with the cost of materials and modules are suitable. Thin-film cells have a large coefficient of absorption of blue light, however, have an advantage in cloudy weather. Lack of amorphous silicon solar cells is in its low efficiency. The efficiency of thin-film silicon cells is about 7 percent, which is lower compared to other cell types. The market share is around 20 percent. The amorphous solar modules are primarily used in systems where low power is needed (watches, pocket PCs) or as an element of the facade. This type of cell provides a homogeneous, because the surface is monochrome dark brown or black. Efficiency (serial production): Approximately 7 percent

The average area requirement for the supply of family homes with electricity (5,000 kWh/a):

~ 71m². Main areas of use: Element facades, watches, pocket PCs

Cells High efficiency HIT cells

HIT (Heterojunction with Intrinsic Thin layer) cells have high efficiency and technology features a thin amorphous layer of monocrystalline silicon on both sides of the plate. HIT cells have a broad light spectrum, and thus produces direct or also in diffuse light and thus to the efficiency to 21%, even at high temperatures. Their drawback is that the modules are more expensive than others. Due to the characteristics of HIT cells, recommended their use in residential buildings, where it must implement a high power to a limited area. Efficiency (serial production): Approximately 16.8 percent

The average area requirement for the supply of family homes with electricity (5,000 kWh/a):

~ 30m². Main areas of use: installations on residential buildings on the limited surface

LGBC (Laser Groove Buried Contact) cells (also called Saturn-cell)

As HIT cells are Saturn-cells of high efficiency and belong to the single crystal-cells. Increased surface plate has a pyramidal shape, thus reducing the reflection of light. Saturn-cells are especially effective in the early morning and evening hours. The concept of Saturn-cell invented firm BP Solar, which continues to develop the technology. The efficiency (mass production): 15.5 percent

The average area requirement for the supply of family homes with electricity (5,000 kWh / a):
~ 32m². Main areas of application: Roof installation on a limited area

Flat collectors

The central part of the flat-plate collector is an absorber with a dark plate. The absorber consists of sheet metal, which are embedded in thin copper tubes. Through it flows a liquid heat carrier. If solar radiation hits the absorber, mainly be absorbed and partly reflected. By absorbing heat is, that the sheet metal sinks in copper pipes. Collector fluid absorbs the heat and transfers it to the tank. Collector surface is covered with a glass plate. Glass prevents the reflection of sunlight and increases the thermal effect. At the back and on the sides set up a thermal insulation layer on the mineral basis. Price-level collectors are most favorable, which is the reason to take even more than 80 percent market share in Europe. However, the efficiency of flat plate collectors is about 30% lower than vacuum tube collectors. Are recommended to achieve a temperature between 20 and 80 degrees. Flat collectors can be installed in various ways, such installation on the roof, integration into the roof or free installation. If we want to achieve the temperature of hot water of 50 °C: Efficiency (summer): ~ 70 percent Efficiency (winter): ~ 45 percent

Thermosiphon solar system (flat collectors) can be combined with flat collectors and vacuum collectors. The system works by gravity and natural circulation of used liquid which is less dense cold and heated water, and functioning without the pump. The liquid heat carrier is heated in the collector. The container is placed above the collector, where heated fluid due to lower density floats above the cold fluid at the top of the tank and radiates warmth. The temperature is reduced and the fluid flows back into the collector. Price thermosiphon collector is very favorable, because the pump and complex control circuits are not required. The device is recommended for flat roofs or on undeveloped site.   The vacuum flat collector’s Flat collectors can be and make the vacuum in the interior of the collector. This increases the efficiency of the collector, as well as price collectors is growing. Are recommended to achieve a temperature between 20 and 120 degrees.   Thermosiphon solar system (with vacuum flat collectors)

Vacuum tube collectors contain vacuumed glass tube connected a metal reflector which heats the solar absorbers and liquid. The absorber is integrated into each tube, and can be easily rotated to the position of the sun, which increases the effect. The vacuum in the pipes prevents heat loss and enables them to achieve a higher temperature than most flat panels. Vacuum tube collectors are collectors of high efficiency, but they are more expensive than flat plate collectors. Good work and in cooler conditions, but the advantage is lost in warmer conditions. Because of the aforementioned characteristics, their use is recommended for achieving high temperatures between 50 and 120 degrees. The location is recommended their use in more countries of northern and central Europe, while due to higher prices less suitable for the Mediterranean area (e.g. the Croatian coast and islands). They are mostly adapted for roof installation (or less for installation in the roof) and are ideal when it comes to limited areas. If the installation of collectors in an ideal direction (southeast and southwest) is not possible, vacuum tube collectors are ideal, because they produce satisfactory even in diffuse light. Depending on the method of connecting pipes distinguish and indirectly electric pipes – Heat-pipe vacuum tube collectors. The vacuum heat pipes are called “Heat pipe” – copper pipe filled with fast volatile liquid. The vacuum between the glass tubes is exclusively within the glass, and the collector is better protected against penetration of air. As the coating surface of the absorber used on the inner surface of the two pipes. When CPC vacuum tube collectors, vacuum glass tube is placed in a parabolic mirror, which increases the efficiency of the collector. If it is desired to achieve a temperature of 50 °C:
Efficiency (summer): ~ 70 percent
Efficiency (winter): ~ 60 percent

Thermosiphon solar system with vacuum tube collectors can be combined with flat collectors and vacuum collectors. The system works by gravity and natural circulation of used liquid which is less dense cold and heated water, and functioning without the pump. The liquid heat carrier is heated in the collector. The container is placed above the collector, where heated fluid due to lower density floats above the cold fluid at the top of the tank and radiates warmth. The temperature is reduced and the fluid flows back into the collector. Price thermosiphon collector is very favorable, because the pump and complex control circuits are not required. The device is recommended for flat roofs or on undeveloped site.

Swimming pool absorbers are made of plastic resistant to weathering and UV radiation without housing, thermal insulation, glass plates and containers. Optimally used to heat water in pools and in Central Europe only in the summer months are reaping good yields. Pool water flows through the absorber, which reach temperatures between 20 and 40 degrees. If it is desired to achieve a temperature of 50 ° C: Efficiency (summer): ~ 20 percent

Solar collectors on the air resemble flat collectors, but they are based on the air that circulates through the collectors and so is heated. The air is then used for heating the building and the ventilation air. To direct solar radiation can be achieved by increase in temperature to 40 degrees.

Hybrid solar systems combine solar and solar photovoltaic and solar thermal systems, therefore producing a combined electricity and thermal energy. The modules are dual-layer, and a higher-level set of photovoltaic cells, which convert light sunny to DC and that solar inverter converts the AC, synchronized with the voltage and frequency of the network. Below is a copper sheet, which collects infrared light. The heat is transported through pipes filled with water up to the roundabout hot water. It is a relatively new technique, so no much experience.