What are solar cells?

Solar cells or photovoltaic cells are used to produce electricity from sunlight. It is the light (and not sunbeams) that activates the solar cell, so, to a certain extent, solar cells produce energy even when it is overcast. Solar cells produce direct current (DC), the strength of which depends on the size of the solar cell system and the intensity of the sunlight.

Conventional solar cells can convert 9-15% of the sun's energy to electricity, while the newest and best types can utilize up to 20% of the in-coming energy.

Solar cells can be divided into three types: mono- and polycrystalline and thin film solar cells, which are all based on silicon. There are also various types based on copper. The silicon based types are the most common.

Grid connected solar cells are part of a building’s energy system, which is connected to the public electricity grid.
Solar cells produce DC power. DC must be converted to alternating current (AC) before it can be used in the power outlets of a building. This is done through a network inverter placed inside the building close to the electricity meter. From the network inverter, the current mixes with electricity from the electric company and flows into the power outlets of the building.

Placing of solar cells

Solar cells are sensitive to shadows and should generally be positioned so that shadows do not hit them during the day. Solar cell panels are connected in series, which means that a shadow even on a small area can reduce the performance of a larger part of the system. It is therefore important to consider shadow risks such as trees, neighbouring buildings, attics, chimneys and the like, when choosing the location of the solar cells. Solar cells require a certion amount of space and typically take up between 6-15 per m2 pr. kWp (depending on the type) which for example means that a 3 kWp photovoltaic system requires about 20-45 m2.

Placing solar panels on the roof

A roof surface is often an optimal placement for solar cells, because it for the most part is slanted and shadow free with easy access to the electrical fittings of the building. Large surfaces without disturbing elements are generally preferable, both for aesthetic reasons and to ensure a uniform lighting. With smaller systems, a fine visual interaction between one or two solar cell modules around a window element or an attic can often be achieved.

Placing solar panels on a frame

If placing solar cell panels on the roof is not possible, they can be placed on a frame on the end wall or placed on racks on the ground. Solar cell panels placed on the ground, should be raised half a meter above the ground to avoid snow and ensure ventilation of the solar cells.

Integrated solar cell systems

Solar cells can be integrated into the building itself. This is especially relevant in new constructions or major renovations, such as a roof replacement. All or part of the roof surface can be built of solar modules, replacing the materials that otherwise would be used.

When integrating solar cell modules into a building, it is important to secure ventilation around the solar cells. Lack of ventilation around the solar cells increases the operating temperature and reduces the performance of the solar cells.

It is also important to check if there are any restrictions in the district plan, which prohibit installation of solar cells, and whether the building itself is listed.

Economics of solar cells

Purchasing solar cells is a long-term investment, all or part of the electricity consumption is purchased for the next several years at once. Whether an investment in solar cells is a good idea - in economic terms - basically depends on what you save by producing all or part of your electricity consumption yourself, compared to buying it as usual.

After November 20, 2012, the placement of solar cells is very important for the economy of a solar power system. Due to new regulations that settle the price by the hour, it is important to use most of the power produced by the solar cells within the same hour as it is produced.

Often electricity consumption in vicarages is not very high on weekdays between 8:00 and 16:00, which makes it important to optimise the output from the solar cells in the mornings and afternoons. This is best done by orienting the solar cells to the east and west rather than south, as has otherwise been common practice.

In a parish community centre with offices, a southern orientation of the solar cells could be a good idea.

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