How to choose the right solar cells

The price of solar cells is crucial to whether you are a good investment. But what is the difference between the expensive and cheap ones? Read how solar cells work and which ones deliver the most electricity.

Prices of solar cells varies considerably and depends on the technology used in the panels. The different types is that they generally provide more power than the manufacturers promise, according to a test conducted by Nordic Folk Centre for Renewable Energy. Photo: Bigstockphoto
What types of solar cells are there?

The solar panels, which are on the Danish market today are almost all crystalline and based on silicon, ie monocrystalline or polycrystalline cells. Furthermore, there are non-crystalline (amorphous) solar cells and amorphous thin-film solar cells, which is based on powdered silicon. In recent years, there are new types on the market that are not based on silicon.

Today, 80 percent of the market solar cells based on crystalline silicon cell technology. The effectiveness of these is usually 13-16 percent, but there are also solar cells with an efficiency of up to 20-23 percent.

Monocrystalline solar cells

This type of solar cell is typically characterized by that it has a black or gray surface that is uniform and evenly distributed on the panel.

A monocrystalline solar cell consists of a single crystal of silicon. They may be round at the corners, but would be a particularly dense packing of the finished module, they can be cut into squares. Most often, the cells are divided into squares with smaller distance to get a higher power and thus greater efficiency.

This solar cell technology is made up of cells which are mounted on a grid of metal and act as a contact network. Then mount the cells between two layers of glass or between glass and a plastic layer. Often, the cells are monteren on a white background to reflect the light that penetrates the cells so that the cells can be kept cool. At higher temperature the efficiency decreases and thus for the effect of the solar cells.

Today you can get monocrystalline solar cells with bypass diodes, ensuring optimum production although there are shadow effects, bird droppings or other to block the sun's rays. Monocrystalline solar cells, the photovoltaic technology with the highest efficiency, but therefore also the most expensive.

Vendors promise now a panel efficiency of 17 percent, a benefit guarantee at least 90 percent after 10 years and 80 percent after 25 years. In addition, it is expected that the panel has a lifespan of between 30-40 years.

polycrystalline solar cells

Polycrystalline solar cells containing multiple silicon crystals, and they are often in shades of blue and square. They are formed by casting in a mold. The individual crystals in the solar cell reflects the light back differently, providing a "living" surface.

Polycrystalline cells have a slightly lower efficiency per. square meter than monocrystalline, but the closer packing of the module is often closer so it outweighs cell's lower efficiency. Panel Efficiency is on ca.13-19 percent and the typical lifetime for this type of solar cell technology is 40-50 years.

Netinverteren which converts the current to 230V, is expected to have a lifespan of 10-20 years, depending on the brand and quality.

Thin film solar cells and amorphous and non-crystalline type

Thin Film Solar cells are also called in some contexts for 2nd generation solar cells and is gaining ground on the market. We know the technology from calculators where they are characterized by having a homogeneous and dark surface. Some vendors claim to thin film solar cells work better in overcast skies than the crystalline, which is an advantage in our latitudes where it is often overcast.

They first developed thin film solar cells based on amorphous silicon (a-Si), and most recently, the arrival of solar cells include copper-indium-selenium (CIS) and cadmium telluride (CdTe). They have a low material and energy consumption in production. Since 2005, their market share has more than doubled.

Amorphous silicon cells belong to the family of thin film solar cells. The photoactive semiconductor is in this case, amorphous silicon (formless or non-crystallized silicon) on which is steamed a support substrate that is often glass. Material consumption is low, and it provides a considerable saving in the manufacture compared with crystalline silicon.

Amorphous silicon is by far the most developed technology. The efficiency is, however, somewhat lower, about 13-16 per cent against 20-23 per cent, as is the case with crystalline solar cells. Amorphous or mikromorfe solar cells can come in many forms.

One can also obtain the solar cell modules of metal foil and plastic, as opposed to the glass modules can be bent without damage. The color is reddish brown to black.

Another type is the CIS thin film solar cells (Cu = copper, indium, I = S = selenium) which is a silicon free technology. The color is black, and their effectiveness is comparable to crystalline cells. The type is very well suited for network connected systems.

integrated solar cells

Integrated solar cells can be used in the building facades and roofs, which means that the solar cells, in addition to the generation of energy, also acts as a weather screen.

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