Renewable Energy Sources

All our civilization is now based on energy. Energy, and in particular electrical energy, is needed to supply all equipment facilitating daily life. For the time being we have obtained it from fossil fuels such as coal, oil and natural gas. Is it possible that the main sources of energy will peter out one day? Yes, because the energy resources we are using now are non-renewable energy sources. Hence, they can become depleted one day, and what then?

 

The first serious warning, that is, the energy crisis, occurred in the 20th century. It mainly concerned problems with access to oil and, in turn, liquid fuels, but it was the first serious signal that supplies of cheap and easily accessible fuel can come to an end one day. A number of European countries took notice of this problem and exploration was undertaken to find other sources of energy. Attention was paid to substances such as: biomass of any origin, peat, and crop processing waste. Also, there were plans to utilize municipal waste and sludge. 

 

The exploration aimed to identify substances which – in a sense – could replace fossil fuels. However, we must assume that in many places fossil sources of energy cannot be eliminated for technical and, more strictly speaking, technological reasons. However, a decision was made to consider possibilities for using combustible waste in thermal processes so that they did not disturb the operation of a typical power boiler. In many countries fuels based on waste of organic, plant and animal origin were put into use. In parallel, works were carried out to use other sources of energy that could be considered auxiliary or renewable.

 

With time the term “renewable energy sources” was coined. So what are they? Non-renewable energy sources cannot be recreated in the contemporary reality. They are consumed, that is, utilized much faster than they are renewed so it is assumed that such resources are non-renewable. These include all fossil fuels such as: Hard coal, brown coal, peat, oil and gas, that are the underlying resources for the power industry, industry in general, transport, and households. Renewable energy sources are resources which, when used, will not be deficient in the long-term. They will be regenerated in quite a short time. Renewable energy sources include: solar and wind energy, biomass, biogas, geothermal energy and tidal energy.

 

There is a common belief that renewable energy is sustainable. Despite the occasional need to make compromises with environmentalists in its generation, renewable energy has been used for some time due to the potential depletion of fossil resources. In Poland, coal will remain the underlying source of energy for many years – be it hard coal or brown coal, but still coal. Works are pending to gradually replace part of the coal by adding renewable fuels in the form of biomass to the fuel mix. Of course, this refers to the big power industry.

 

In Poland there are a few options for obtaining energy from renewable sources. These comprise:

  • hydropower;
  • solar power;
  • wind power;
  • geothermal power;
  • biomass.

 

The share of renewable energy in Poland is ca. 4.4 GW. It includes:

  • biomass: 22%;
  • biogas: 4%;
  • solar plants: 0.03%;
  • hydroelectric power plants: 16%;
  • wind farms: 58%.

 

The availability of renewable energy sources requires ensuring the technical possibility to use them, which is not always easy to do. Suitable equipment and systems must be designed in which the sources of energy can be properly prepared, processed and used. It is also important to ensure that the costs of such an operation do not exceed the expected outcome – both economic and environmental. Investments in renewable energy sources are determined by multiple factors. 

 

 

Solar power

 

It is assumed that solar power is a commonly available, completely clean and the most natural source of energy. It can be used locally to satisfy the requirement of hot water and heat in general. Its advantage is easy adaptability, in particular for household purposes, although it is known that the systems are also useful in supplying larger housing estates.

 

From the point of view of a potential user, the most important parameters in using solar radiation energy are the annual insolation values. Insolation – although the term: solar light seems more appropriate – is the amount of solar energy reaching a flat surface in a specific time. So, how can the solar power resources be estimated? The average citizen can see the sun shining, enjoys the warmth it emits, until – convinced by other people or commercials – he/she starts thinking about investing in solar power. The main argument is that it is cheap to obtain – the sun shines for free and thanks to free energy the return on expenditure is very quick. Solar energy resources, just like other renewable energy sources, can be split into: theoretical, technical and economic resources. 

 

Theoretical potential – the amount of energy that can be used assuming that the efficiency of its obtainment is 100%. The theoretical potential (or theoretical resources) takes into account the use of all available resources for power generation purposes. Thus, its size to no extent reflects the actual possibilities of obtaining such energy.

 

Technical potential – a part of the theoretical potential also taking into account the efficiency of available equipment and technologies. An additional element of this potential is to take into account the geographical location and the possibility of storing energy.

 

Economic potential – a part of the technical potential. It depends on fuel prices, taxes, and potential support for specific energy-related activities. The potential is calculated based on detailed analysis of the profitability of a specific activity.

 

Solar energy seems very sustainable, clean and profitable – but is it identical everywhere? Not really, as the insolation is different in respective parts of Poland. Hence, in Poland the annual density of solar radiation on a horizontal surface ranges from 950 to 1250 kWh/m2. It must be emphasized that weather conditions characterised by very uneven distribution of solar radiation in an annual cycle have a large impact on insolation. In the territory of Poland, about 80% of the total annual sunlight is concentrated in the spring and summer season, that is, from the beginning of April until the end of September. The period of exposure to sunlight in summer is extended to 16 hours a day. In turn, in winter it is reduced to 8 hours a day. Clear differences in insolation in respective seasons of the year and weather anomalies disturb the image of solar energy potential. In planning such a system the possibilities of obtaining solar energy should be examined.

 

Taking into account data from the table, it can be concluded that exposure to sunlight is not sufficient enough to warrant investing in this type of power everywhere. In particular, the degree of insolation can vary considerably even during the day.  It must be assumed that in Poland solar energy is mainly used as the source of heat by means of solar cells heating air or water. For economic reasons, solar batteries are used in small power systems. They are mainly used to supply standalone structures situated far from the main grid, such as, for example, road signs, pedestrian crossing lights, garden lamps etc. Sometimes solar cells supply small units such as calculators. 

 

 

Wind power stations 

 

As its name suggests, such a power station uses wind force and energy. In other words, wind energy is converted into electricity. It would be excellent if the wind blew constantly and at the same time with great power. Unfortunately, wind does not blow all the time.

 

Thus, before we undertake a wind project, it is advisable to check the wind rose in Poland. It is necessary to identify areas where winds are most favourable to situate wind farms. Wind energy can be obtained both from a huge wind farm – where in the specific area several or more wind turbines are installed – or a single wind turbine, depending on the energy requirements.

 

Wind energy in Poland has been developing since the beginning of the 1990s. According to available information, the first wind turbine in Poland was erected in 1991 at the Hydroelectric Power Plant in Żarnowiec. The first commercial wind farm in Poland was built in the village of Cisowo in the West Pomeranian voivodeship. It was put into operation in March 2001 and comprised five power stations with the total capacity of 10 MW. It must be emphasized that wind farms have different installed power. They can generate power from a few to several dozen MW. To ensure that the effect of operation of the wind farm is economically satisfactory, it should be located on a site with good or very good wind conditions. The best wind conditions occur in the north of Poland and in the central and western part of the country. The wind power industry was shaped dynamically in the first years of the 21st century. At that time there was a considerable increase in investments in wind power as a renewable energy source. The potential of wind power stations progressively grew – in the last decade from 83 MW (in 2005) to 5005 MW (in 2015).

 

According to information provided by the Energy Regulatory Office, in Poland at the end of 2015 as many as 981 wind power systems of different size were in use. This data refers both to single units and large farms comprising a dozen or so turbines. ERO stated that the total power of wind turbines installed in Poland was 4117 MW. Wind power stations are “large size” units, which means they cannot be hidden far from sight, concealed etc. Building at least one wind turbine – not to mention a whole farm of a dozen or so or several dozen wind turbines – we interfere with public space. Every wind turbine erected in the lowlands, mountains or at the seaside significantly alters the landscape. Sometimes wind turbines, built in good faith in an open area, form obstacles on the migration routes of wild birds.

 

While there are profits in the form of renewable energy, we can also sustain losses caused by interference with the landscape and natural environment. Wise collaboration between a potential investor and environmentalists and ornithologists should result in solutions that are the friendliest and optimum for the natural environment.

 

 

A wind turbine – also referred to as a wind motor, wind tower, wind power station or wind generator – is a technical device converting the kinetic energy of wind into mechanical work in the form of rotary movements of the rotor. A standard turbine is a structure several metres tall with a diameter reaching a dozen or so metres. With regard to design differences in rotor axis position, turbines can be divided into turbines with a vertical axis of rotation and propeller turbines with a horizontal axis of rotation. The landscape of Poland is dominated by the second type. Their general operating rule is based on the impact of wind energy on the horizontal rotor in the form of a propeller mounted in a special nacelle. The nacelle is positioned “against the wind”. In turn, the propeller shaft supported on bearings through a transmission drives the generator that converts wind energy into electricity. The most popular wind turbine is a three-part propeller turbine. The whole structure is mounted on a tall tower. Of course, the angle of the blades can be adapted to wind force and speed. Like every structure, a wind turbine is not silent and it generates some noise. However, if the distance from buildings is considerable, the noise need not be onerous. 

 

 

Hydroelectric power plants

 

Historically, water downfall energy was used in water mills or forges. At present, water energy is most often converted into electricity. Hydropower engineering is mostly based on water dams that alter the local landscape. Dams are built where rivers can be dammed. On the one hand, a dam can stop excessive water flow, while on the other it disturbs local water relations. 

 

However, assuming that water flows into the reservoir all the time, the proper damming level guarantees supplies of energy for water turbines. Before electrical machines were invented and electrical power engineering was popularized, water energy was used to drive mills, forges, saw mills and other industrial works. It is assumed that water energy can be cheaper than energy from the combustion of fossil fuels (hard coal, brown coal or gas) or nuclear energy. Areas rich in water energy can be attractive for industry due to reduced prices of electricity. However, the development of power engineering and increased ecological awareness have contributed to the fact that the use of water energy is more and more often dictated by environmental protection and not price calculation. It is assumed that energy from water downfall can be cheap but at the same time it should not have a negative impact on the environment. 

 

At present, in Poland more than 16% of electricity produced by means of technologies involving renewable energy sources, derives from hydropower engineering. This information is provided by the Energy Regulatory Office. It accounts for less than 2% in the balance of total production of electricity in Poland. Due to the terrain in Poland being mostly lowlands without large natural downfall, the conditions are not favourable for building large hydroelectric power plants. With regard to hydrological conditions, the development of hydropower engineering is mainly connected with small hydroelectric power plants. The installed capacity of units generating electricity using water turbines is 937 MW, according to data provided by ERO. Such power is installed in 727 hydroelectric power plants that are currently in operation.

 

Most of them are small hydroelectric power plants often generating power for the needs of a local community that decided to use an old water mill with a small capacity turbine installed sufficient to supply a small human settlement.

 

However, there are also large plants in Poland besides small and very small power plants.

 

There are quite large time intervals between the construction of power plants. Most often, information that such a project is planned – irrespective of where in Poland – gives rise to protests from local inhabitants. After tedious negotiations finally an agreement is reached but the commencement of the project is delayed. Taking into account the mostly lowland terrain in Poland, most hydroelectric power plants are built on rivers. When the water table is properly dammed, turbines with various capacities can be installed. This is one of the methods of obtaining renewable energy.

 

 

Geothermal power

 

Geothermal power (geothermic energy or geothermics) is one of the types of renewable energy sources. It uses the heat energy of from the inside of the Earth, in particular in areas of intensive seismic activity. The operating principle of this phenomenon is that precipitation waters penetrate inside the earth and in contact with active magma are heated to considerable temperatures. 

 

Due to this process water raised towards the surface is either hot or it changes into water vapour. Geothermal water can be used directly, through a system of pipes, or indirectly transferring heat into cool water, based on the principle of heat exchange in a closed cycle. 

 

Geothermal energy comes from geothermal water extracted on the surface. This energy is renewable since it is sourced from the hot inside of the Earth – it is practically inexhaustible. To extract geothermal water, a hole must be drilled down to the water table level. This hole is called an intake. In addition, at a certain distance from the intake another hole called a return hole is drilled. There, geothermal water – after receiving heat from it – is pumped back inside the reserve to be heated again. This is how an inexhaustible energy source is obtained. However, this method comes with certain risks that can occur during the production of geothermal energy – the possibility of polluting deep water, and the risk of releasing radon, hydrogen sulphide and other gases. We should therefore be careful with obtaining geothermal energy on a wider scale. However, when appropriate technologies are used, this method can be one of the most efficient sources of renewable energy. Thus, what is the possibility of utilizing geothermal energy in Poland? 

 

Poland has very good conditions for utilizing geothermal energy as 80% of the area of the country is covered by 3 geothermal provinces: Central European, Fore-Carpathian and Carpathian. Water temperature in the above-mentioned areas ranges from 30 to 130°C (at some points even up to 200°C). Such water occurs in sedimentary rocks at a depth of 1 to 10 kilometres. Considerable depths at which geothermal waters occur can increase the costs of exploitation of such a reserve. Natural outflows of geothermal water are very rare. In Poland we can observe this phenomenon in the Sudetes (Cieplice, Lądek Zdrój). It is asserted that geothermal waters can be used in 40% of the territory of the country.

 

Extraction of such water is profitable when up to a depth of 2 kilometres the temperature is at least 65°C, and the content of salt in water does not exceed 30 g/l – on the assumption of sufficient resources. The first Geothermal Plant in Poland in Bańska-Biały Dunajec was built in 1989-1993. The drill holes and the systems are used by PEC Geotermia Podhalańska SA which supplies heat to most households in Zakopane. There are eight geothermal heating plants in Poland. These are: Bańska Niżna [4.5 MJ/s, ultimately 70 MJ/s], Pyrzyce [15 MJ/s, ultimately 50 MJ/s], Stargard Szczeciński [14 MJ/s], Mszczonów [7.3 MJ/s], Uniejów [2.6 MJ/s], Słomniki [1 MJ/s], Lasek [2.6 MJ/s] and Klikuszowa [1 MJ/s]. It can be seen that some plants have not reached the designed parameters yet. Where there are favourable technical and technological conditions, the capacity will be certainly increased. 

 

 

Biomass

 

It is assumed that energy from biomass kept the human race existing for some 100 000 years. Of course this is an estimated number but we have to take into account that biomass is still the main source of energy in many places on Earth. So, why is biomass such an important renewable energy source? Some people believe biomass is emission-free. This means that carbon dioxide emitted during combustion is immediately assimilated by the nearby vegetation in the process of photosynthesis. This idealistic assumption does not work with mass emissions of carbon dioxide into the atmosphere in a specific area. 

 

Biomass, as a renewable source of energy, makes up a considerable share in power generation. The following substances are classified as biomass:

  • waste timber;
  • straw;
  • energy crops;
  • agricultural waste;
  • forestry waste;
  • wood processing waste;
  • animal husbandry waste;
  • animal faeces;
  • sludge;
  • energy seaweed;
  • organic waste (beet pulp, corn stems and cobs, grass);
  • vegetable oils;
  • animal fats;
  • and many others.

 

So, what is biomass generally? It is normally defined as a biodegradable fraction of products, waste and residues from agriculture, forestry and other related industries, including fishery. This also includes biogas and biodegradable fractions of industrial and municipal waste. Biomass is first produced through photosynthesis where solar energy is accumulated in plant organisms. Next, animal biomass occurs in the food chain. Biomass occurs in the form of fresh (moist) pulp and dry matter (living organisms – dried out or evaporated). It is estimated that Poland uses only about 7% of the biomass potential compared to the average (20%) in EU countries. Adequate instruments must be implemented in order to increase biomass utilization.

 

Assuming that part of the biomass comes from the agricultural production of food, we will increase the amount of usable biomass by planting wasteland. It is assumed that the largest biomass production potential is with energy crops (e.g. energy willow). A considerable amount of energy can be obtained from the processing of excess straw, which is considered agricultural waste. It is estimated that more than 11 million tonnes of straw could be used for power generation purposes. Another excellent fuel is biogas obtained from the degassing of landfills and produced in biogas plants built within the territory of wastewater treatment plants.

 

In Poland the use of biomass for power generation purposes is to a large extent the production of heat in small local power plants. Some of them are household plants supplying heat to one family only. There are also larger plants – used on farms or being a small heating plant supplying heat to a small housing estate composed of several households. Recently, coal has been more and more often combusted with biomass in utility power engineering. A growth in the number of small biogas plants using agricultural waste, both of plant and animal origin, is worth noting. In addition, biogas plants can also use sludge produced in the wastewater treatment process.

 

The use of biomass should be supported by technical and technological equipment to produce not only liquid but also solid fuels such as pellets and briquettes. A barrier to using biomass can be its low specific gravity as an input material, which is associated with high costs of transportation from the production site to the processing site. A good solution would be to process input biomass in the direct vicinity of the place in which it was produced. The raw material after processing could be supplied directly to potential customers. Another solution would be processing and using the resultant biomass on the production site. Then, we would be dealing with a locally produced raw material and locally utilized fuel.