Wind and solar energy

Wind power is the world's fastest growing production form of renewable energy. The size and efficiency of the power stations has grown and wind power has achieved a notable position in the energy production of many countries. Although there are amply of possible areas suitable for production in Finland, wind power still represents only a small share of the total supply of electricity [1]. The coast, sea and fells are the best areas for the production of wind power. According to clarifications, the wind power potential on the Finnish sea areas is tens of terawatt-hours per year [2].

Solar energy is another good production form of renewable energy. It can be utilised either passively or actively. In Finland, solar energy acts as a complementary form of energy alongside others and its use is emphasised to the period between March and September when, in Southern Finland, 90% of the whole year's radiation energy is received. Year-round utilisation is difficult in Finland and would require storing of the solar energy in the summer for the colder and darker periods in the winter. [3]

Use of wind power in Finland

When the air moves as a consequence of temperature and pressure differences in air masses, wind is created. In other words, also wind power originates in the sun. The kinetic energy in wind can be transformed into a rotating motion and further into electricity in a generator. Operation of a wind power station is based on the moving molecules of air whose kinetic energy is transformed into rotational energy with the help of the wind power station's blades. When the blades rotate, they move the axle that is connected to the generator and the rotational energy is transformed into electricity in the generator. Electricity created with wind power is lead to a transformer and then further to the electrical power network. [2]

With a combined power of 147 megawatts (MW), Finland's wind power capacity includes a total of 118 power stations (May 2010). Approximately 0.3% of the consumption of electricity in Finland is covered with electricity produced with wind power (approximately 277GWh in 2009) [4]. Over the last few years, size of the wind power station units has grown markedly. Nowadays, the size of constructed power stations is invariably at least 1MW, with the largest wind power stations on the market being 5MW. The most common size is 2-3MW, however. Main parts of a wind power station include the rotor (hub and blades), engine room, tower and foundations. Due to different technical solutions, models from different power plant manufacturers deviate from each other to some extent. In most cases, the greatest external difference is visible in the form and size of the engine room. Depending on the size and location of the power plant, the height of the tower varies from 50 to 130m [2]. The planned operating life of a wind power station is 20–30 years during which parts may have to be replaced and repaired. When constructing a new plant, it can be based on the foundations of an old power plant [5].

An area with several interconnected wind power stations is termed a wind farm. Such a farm is connected as one entity into the electrical power network. The power stations of wind farms are placed several hundred meters apart. This distance is defined according to several factors such as size of the turbine, number of power stations and their placement pattern [5]. One of the benefits of wind power stations is that their construction takes much less time than that of traditional power stations. [1]

Production of wind power varies daily and by season, which is why wind power cannot function as the only source of energy but it requires other production of electricity to even out the difference between consumption and production. Wind power is ideal for decentralised production of electricity. When wind power is used to produce only a part of the electricity, windless days, which are rare in Finland, do not form a problem. In addition to it being more windy in the winter than in the summer, freezing temperatures are not problematic for wind power. To start, a wind power station requires a wind of 4m/s. As the wind speed increases, so will the power of the plant. When the wind speed rises to 15-25m/s, power must be restricted with passive stall control or active adjustment of the blade angles, and to avoid damage to the equipment, the plant usually has to be stopped if the wind speed rises above 25m/s. [2]

Use of solar energy in Finland

In one hour, the globe receives more radiant energy from the sun than the whole mankind consumes energy in a year. In comparison, the annual amount of radiation in Finland totals approximately 1,000kWh/m². This energy can be utilised either passively or actively. Passive utilisation refers to the direct utilisation of sunlight and heat without a separate device. In active utilisation, the solar radiation is transformed either to electricity with solar panels or to heat with solar collectors. Both passive and active methods can be used in single-family houses. Using solar panels, approximately 15% of the radiation can be transformed into electricity and, with solar collectors, approximately 25-35% into heat [2]. Compared to Southern Europe, the radiation power in Southern Finland is approximately 50% smaller. In Finland, key market targets for solar energy include buildings, applications for the built environment and summer time and solar electricity applications in sparsely populated areas [3].

Although they are also suitable for heating dwellings, solar collectors are mostly used to heat tap water. A solar heating system can be combined to all main heating forms. It is a particularly good option in connection to a heating system that already has a boiler. Since the temperature of circulating liquid in a floor heating system is lower than in a radiator heating system, houses with floor heating receive more energy from a solar heating system. The most common technical solution is a fluid circulation flat-plate collector that uses a pump to circulate a mixture of water and glycol. The liquid that has heated in the collector runs through manifolds to a heat storage and the heat transfers through a heat exchanger to the hot tap water or the building's heating system. When a solar heat system is dimensioned, the starting point is the heat energy consumption during the summer months and mainly the need for tap water. The capacity of the boiler should be sufficient for the consumption of a few days. [2]

Evacuated tube collectors, which are more efficient than fluid circulation flat-plate collectors, are another alternative for water heating. These collectors can utilise the diffuse solar radiation more efficiently and produce approximately 30% more energy per square metre. In Southern Finland, the evacuated tube collectors begin to produce heat already in February and still provide heat in November. Before purchasing a collector, however, you should ensure that the sun shines on the roof also when it is low. The received benefit is also greatly affected by impediments in the terrain. [2]

Solar power is produced with solar panels. These panels consist of solar cells in which the energy of the solar radiation creates a voltage. A solar cell is an electronic semiconductor. Solar radiation creates a voltage between the lower and top surface of the cell. Volume of the current produced by the cells, or the solar panel, is directly proportional to the intensity of the solar radiation. For example, in cloudy weather, the intensity of the radiation is markedly weaker than in bright sunshine. [2]

In addition, solar power can be used to produce a notable part of the electricity needed by a household. Solar power systems can also be installed in residential and office buildings in which they produce a part of the energy needed in the building. The electricity produced by a solar panel can be stored in one or several batteries, which are used during the night and on cloudy days. The capacity of the batteries should cover normal consumption for a few days without charging. Any production exceeding the consumption can be fed into the general electrical power network. [2]

Passive utilisation of solar energy is inexpensive. In its most simple form, solar energy is utilised as daylight instead of artificial light. The purpose is to collect heat, promote the use of natural light and reduce heat loss. Using a range of structural solutions in the building, the efficiency of using sunlight and solar heat can be improved. With regard to collecting solar energy, the most favourable location for the building is a southern slope. Other factors include the shape of the house, size of the windows and building materials, these having a notable effect on the heating and lighting costs. [2]

In the summer, buildings must cater for the hindrances of overheating which can be prevented with roof and eaves solutions, ventilated conservatories, ventilation and blinds, curtains and other movable elements. The roof and eaves constructions can be designed so that they provide shading during the summer months but do not prevent the low shining sunlight in the late winter. Particular attention should be paid to arranging natural ventilation in the building. The best passive means include excellent insulation, materials that store heat, glazed porches and conservatories, bearing walls and having large windows on the southern side and small ones on the northern side of the building. [2]

To fight climate change, Finland is committed to reducing greenhouse gas emissions. The Finnish Climate and Energy Strategy (2008) has set a goal to increase the share of electricity produced with wind power and solar energy to six terawatt-hours by 2020. This means increasing the production capacity of mainly wind power to approximately 2,000MW during this time [2]. With respect to solar energy, increasing heating is considered to be more important then the production of solar power. This is mainly due to the lower costs of solar heating. The long-term climate and energy strategy states that a wider-scale implementation of solar power will be timed to future decades and is dependent on the results of research and development operations. [6]

 

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Figure 1. Wind Atlas provides information regarding the wind conditions in the whole of Finland. [1]

The Finnish Wind Atlas project (www.tuuliatlas.fi) produces information of the Finnish wind conditions. It aims to produce as accurate a description of the wind conditions as possible including speed, direction and turbulence of wind. The Wind Atlas includes a modelled extensive sampling of the wind conditions over the last 20 years and includes a dynamic map interface (figure 1) which can be used to study the conditions on different sides of Finland. When assessing the placement of power plants and the possibility of producing electricity with wind, the Wind Atlas is an important tool. It can be used to compare the annual and monthly variation in wind conditions in the whole of Finland or in specific, limited areas. The map interface can therefore be considered a significant tool for constructors and planners of wind power. For example, reserving areas in regional plans has been restricted by the lack of information regarding wind conditions on different sides of Finland, the inland in particular. [1]

Environmental impacts of wind and solar power

Use of renewable energy is also related to potential impacts on the diversity of nature. With regard to the utilisation of direct wind power and solar energy, impacts are scarce and some of the impacts may even be positive. Direct positive environmental effects include the reduction of greenhouse gas emissions to fight climate change while indirect impacts can, at best, consist of replacing fossil sources of energy with wind energy which prevents the release of harmful emissions in the air. If solar and wind power are used to replace bioenergy, at best, problems related to decrease of biodiversity can be avoided. Greenhouse gas emissions of both wind power and solar energy are mainly created during the construction phase. [7]

 

Environmental impacts of wind power are relatively minor. Production of electricity with wind power does not cause any CO2 emissions or any other emissions. In addition to impacts to the scenery, environmental nuisances during the use of wind power include effects related to operating noise and land use. The greatest nuisance is aimed at the scenery. Due to their large size and shape deviating from other buildings, wind power units stand out in the scenery. By placing the power stations at sea or to a location that is as unnoticeable as possible or to formations pleasant to the eye as a part of the cultural scenery, impacts to the scenery caused by wind power construction can be diminished. [7]

Noise nuisances caused by wind power stations are created by the aerodynamic noise of the blades and noise of the generator. At the base of a wind power station, the noise corresponds to the volume of normal speaking voice (60dB). In most cases, the noise from an industrial size wind farm (2–3MW) located on land is less than 40dB at a distance of 700–1,000 metres from the power station. However, the number of units, terrain and vegetation have an effect on the reduction of the noise level. [7]

Underwater environmental effects of onshore wind farms are very similar to other constructions requiring dredging. In addition to installation of underwater electrical cables, the seabed is mainly affected by dredging and construction of foundations. An onshore wind farm can have a negative impact on fishing and the nutrition of sea animals. On the other hand, constructions may liven the seabed by providing cover to the fauna and vegetation. In addition, power plants set restrictions on moving at sea. [7] The possible harmful effects of noise and vibration transmitted by onshore wind farms on fish are currently under investigation.

On a global scale, wind farms are known to be a threat to birds who have, on occasion, collided with wind power stations. The risk, however, is relatively small and estimated at 1/1,000, as birds can see and hear the power stations from afar. In most cases, a bird steers clear of the power station by 100–150 meters, also during the night. The size, power, colour and location of the power station on land or at sea has no notable bearing on the collision risk. Although the collision risk with wind power stations is small, it is recommended that the resting sites of migratory birds (e.g. Liminganlahti) and junction sites of great migratory flows on the coast (Porkkala, Hanko and Pellinki in particular) be avoided as the locations for new wind farms. [7]

As such, a solar heat system does not cause any emissions during its operation. Indirect emissions and environmental effects are created by the materials, installation work and electricity needed in a solar heat system for pumps, for example, during operation. Solar power does not produce any emissions during use. Its main environmental effects are created during the production phase of solar panels. In an accident, for example, harmful chemicals could be released to the environment. Environmental effects are greatly dependent on the solar cell technology used. [3]

References

  1. TEM 2008. Suomen tuuliatlas. http://www.tuuliatlas.fi/
  2. Motiva 2010. Uusiutuva energia 2009. Motiva, luettu 28.5.2010. Päivitetty 17.11.2009. http://www.motiva.fi/toimialueet/uusiutuva_energia
  3. SOLPROS AY 2001. Aurinkoenergia Suomen olosuhteissa ja sen potentiaali ilmastomuutoksen torjunnassa. Helsinki 2001. http://www.kolumbus.fi/solpros/reports/3rdeport_final.PDF
  4. VTT 2010. Suomen tuulivoimatilastot. http://www.vtt.fi/proj/windenergystatistics/
  5. Suomen Tuulivoimayhdistys ry. http://www.tuulivoimayhdistys.fi/
  6. Valtioneuvosto 2008. Pitkän aikavälin ilmasto- ja energiastrategia. Valtioneuvoston selonteko eduskunnalle 6. päivänä marraskuuta 2008. http://www.tem.fi/files/20585/Selontekoehdotus_311008.pdf
  7. Motiva 2010. Tuulivoiman ympäristövaikutukset 2010. Tuulivoimaopas, luettu 1.6.2010. Päivitetty 5.5.2010. http://www.tuulivoimaopas.fi/

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