Jari Marjo

Product Marketing Director,

Solar Energy

Vacon Plc

jari.marjo@vacon.com

Finland

Today the production of solar electricity is still controlled by decisions based on national energy and environmental policies all over the world. In practice this means that solar electricity production would not be financially profitable without various forms of national support, the most common being fixed feed-in tariff for a production plant, agreed upon in advance. Other forms of support include investment grants, tax allowances or inexpensive loans.

Although the maintenance costs of an operating production plant are very low, the decrease in the initial investments made in recent years has further diminished the significance of feed-in tariffs and other subsidies. The lower initial investment cost has mostly been due to the decrease in the price of solar panels and furthermore, the efficiency of panels has significantly increased in the recent years. The general development of the industry and the growing volumes have had such an impact that the prices of all other components have also come down and this development is likely to continue in the future as well. Solar electricity will become an important business domain and it can also be one way to solve the energy production problems in the world and diminish the emissions of fossil fuel use.

Production Plant Structure

A solar power plant consists of solar panels, their support structures, solar inverters, cabling, transformers, and communications systems. There are also often different monitoring and condition monitoring systems, weather systems or systems to turn the panels to follow the motion of the sun.

Solar panels in use.

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A structural diagram of a solar electricity production plant.

Solar panels (that is, solar cells) convert the radiation from the sun into direct current by means of photoelectric effect. The panels are first connected in series as panel groups to achieve the desired voltage level. These groups are then connected to each other in parallel to increase the current and to minimize field cabling.

The direct current feeds from the panels are finally connected to solar inverters which transform the direct current into alternating current suitable for the electrical network. The voltage of the alternating current is adjusted to the needs of the distribution network with a transformer. Production plants from a few hundred kilowatts and higher power are typically connected to a medium voltage network.

There are roughly speaking two main methods to install solar panels, either on the ground using support structures or on the roof of a building, directly on the slope of the roof or directed with support structures towards the sun. 

Panels that are installed on the ground have typically higher overall efficiency than the panels installed on a roof. A panel field of 1 MW requires an area of about one hectare, in roof installations the output power varies from a few hundred watts in household installations to hundreds of kilowatts in industrial establishments. The largest solar electricity plants currently under construction are located in the United States. Their power reaches 550 MW and as a reference the nominal power of the Loviisa nuclear power plant reactors in Finland is 488 MW.

Solar Inverters in Energy Production

The main task of solar inverters is to transform the direct current produced by solar panels to alternating current suitable for an electric network using power inversion technique. In addition to the electric transformation, the task of a solar inverter is to control the frequency and phase angle of the electricity being fed to the network and to control and protect the solar panels. A solar inverter also protects the electric network in various fault situations.

Solar Inverter Market

The global solar inverter market has grown strongly in recent years and this strong growth is expected to continue in the future. Currently the development of the market requires two favourable conditions: availability of solar radiation and an environment with energy policies allowing different subsidies. The largest installation base is in Germany where the long-term government support has developed the basis for extensive use of solar electricity. Support measures have made Germany the leading solar electricity production and competence area in the world and many of the major manufacturers of solar inverters are German.

Europe, The Middle East and Africa (EMEA) is still the largest market, even though the Asian and American markets are growing the fastest. At the end of the decade the markets will likely be divided fairly evenly between these three areas. During 2013 the United States is expected to grow into the biggest single market, China, Germany, Japan, Italy, and India following right behind. Smaller established markets will be formed in many countries on all continents.

The technology used in the industry has developed so that solar electricity plants produce electricity as feasibly as, or more feasibly than conventional production plants using fossil fuels. Another factor promoting the growth is the relatively easy distributability of solar electricity plants, for example in the sparsely populated areas of India, Africa, and South America. In fact, in many of these areas the cost of solar electricity production is already comparable to production based on fossil fuels. This turning point is timed differently in different countries and already now, under certain conditions, the electrical energy produced from solar radiation meets the market price. Good examples are the momentary electricity prices in Central Europe during peak consumption, or the above mentioned remote districts of India and South America, where diesel generators are used for electricity production.

The third advantage is the benefits and savings offered by solar electricity plants to network operators, also in densely populated countries. It is possible to move production plants in the megawatt range closer to the consumption which decreases network investments and improves the reliability of the network. Solar electricity plants enable to maintain the reliability of the network during voltage or frequency swings and these plants can also maintain the network by feeding reactive power into it during a short-term feed fault.

Future Outlook for Solar Electricity

The intensive development of the technology and the introduction of new innovations in different production subareas increase the energy and cost efficiency of solar electricity plants. Continuous development of the manufacturing techniques of components also improves their production capacity and reduces production costs.

The number of suitable objects for producing solar electricity is also continuously on the rise. For example, solutions directly integrated in buildings are becoming commercially viable. Good objects include large industrial and storage properties, shopping malls and apartment buildings. In such sites the production needs of solar electricity can be taken into account already in the building phase. Wall and roof surfaces can be covered with solar panels instead of traditional cladding. In sparsely populated areas larger and larger areas will be harnessed for solar electricity production and large, even 500–1000 MW plants will become common.

The production peak of solar energy is usually timed a few hours prior to the energy consumption peak. Energy must be stored and technical solutions related to energy storage are developing. In the future, plants will be able to store energy for a short period between the time of production to the peak of consumption. Development of the technical solutions for longer term storage will also enable regional independence from traditional forms of energy.

It has been estimated that in 2030, the share of solar electricity of the European energy production will be about 10 %.