Compared to other RES, the use of solar energy is a relatively contemporary solution for energy generation. Extensive development of solar energy technologies and installation of solar panels in the world started only around 2005, while in Latvia it was even later – around 2012. However, solar energy is currently the third most widely used RES in the world. Even though the solar energy boom has begun, only 1% of all electricity produced globally in 2019 came from solar technology.

One of the myths is that solar energy is available only in southern countries, where the sun shines more and there are no winters like in Latvia. However, if we look at the solar intensity map of the EU, we can see that the solar intensity in Latvia is at the same level as in Denmark and Germany, where solar energy technologies have been used for a long time and on a much larger scale. Until now, the use of solar energy in Latvia has developed more rapidly as a microgeneration solution in households, however, in recent years, more and more companies have chosen to build their own solar stations, which are mainly intended to ensure the company's self-consumption.

Solar energy technologies convert sunlight and solar heat that reach the Earth into energy. To generate electricity, solar panels are used, which capture photocells from sunlight. On the other hand, thermal energy can be obtained by means of solar collectors, which make the solar heat reaching the Earth usable for heating buildings or production processes.

All solar technologies work on a similar principle – the basic technology captures solar radiation (heat or light), concentrates it at a point and transforms it into thermal energy or electrical energy, respectively. It is especially important to position the technologies correctly so that the sun shines on them for as long as possible. Most often, solar panels and solar collectors are recommended to be placed to the south with a slope of 42˚ to the horizon.

When choosing the capacity of solar technology to be installed, it is also important to consider the energy consumption of your company. It is clear to everyone that solar technology will produce energy during the day, and the amount produced will be greater in the summer months, when the sun shines much longer. The biggest financial benefit will be gained if the electricity produced by the panels can be consumed immediately, while in the case of collectors, it will not be necessary to install large storage tanks for heat storage.

Evaluation of solar panels

Evaluation of thermal collectors

The amount of wind energy within the total amount of electricity produced is highly dependent on the region's willingness to use and develop the wind energy industry. In general, only 5% of the world's electricity is produced from wind. The European Union (EU) has a higher share of wind energy, providing around 16% of total EU electricity production. The EU generates the most wind energy in Germany and Denmark. In Latvia, wind energy provides only 3% of the total amount of electricity generated.

In Latvia, all wind power plants (WPPs) are installed on land, moreover, no new wind capacity has been installed since 2017. Most of the WPPs are located on the coast of Kurzeme, which in terms of wind resources, is one of the richest regions in Latvia as well. Equivalent wind velocity is also available elsewhere in the highlands of Latvia, but the total area for useful energy generation is smaller. At the same time, five offshore WPP projects are being developed, however, so far, none of them have been commissioned.

Wind energy is generated by wind turbines or wind generators. Both vertical axis and horizontal axis wind turbines are available on the market. Horizontal axis wind turbines are most often installed in wind farms both onshore and offshore.

Wind farms at sea are called offshore wind farms. They have the greatest growth potential, as their installation is not restricted by land use regulations, buffer zones or land ownership. Compared to onshore wind farms, offshore wind farms generate more electricity as it is possible to install higher wind turbines and offshore wind velocity is higher than onshore.

The wind turns the turbine propeller or rotor, which generates electricity as it rotates. The amount of electricity generated by the wind generator can be increased by increasing the height of the rotor of a wind turbine or by improving the aerodynamics of the blades. Improved blade aerodynamics will allow them to start turning at lower wind velocity, making turbines suitable for countries with low wind volumes.

Although currently wind turbines are mostly installed in large parks with the aim of trading electricity on the stock exchange, companies also have the opportunity to install them on their territory to use energy for self-consumption. For tall horizontal axis wind turbines, the biggest problem could be the approval process and public reluctance to see such installations near their homes. The solution to this problem could be turbines of smaller power and size or, for example, vertical axis turbines, which are quieter and have less impact on the surroundings. Wind turbines make it possible to obtain cheap and environmentally friendly energy even when solar energy is not available.

Evaluation of wind turbines

Solid biomass is one of the most widely used forms of bioenergy worldwide and is used in both domestic and industrial applications. In households, biomass is mainly used only for heat. In industry, biomass is used for both thermal energy and electricity production. A particularly active user of biomass is the EU, which is not only the largest producer of wood pellets, but also the largest consumer in the world.

In Latvia, the heat supplied in the district heating system is mostly (approximately 80%) produced from solid biomass, mainly wood chips. At the same time, heat is also produced by burning firewood, wood pellets, briquettes, wood residues, and non-wood biomass. In cogeneration plants, where both heat and electricity are generated at the same time, biomass consumption is only 11% as it is still more efficient to use fossil resources in these plants.

Bioenergy is also available in gaseous form. The most widely used biogas today is biomethane. It is mainly obtained from agricultural manure by fermentation. The resulting gas is purified from various impurities to obtain almost pure methane. Biogas can also be obtained from other resources: algae, sewage sludge and waste of biological origin.

The EU is also the world's largest producer of biomethane. Taking into account that, in general, biogas is used in much smaller volumes than solid biomass in the world, it is also used less in Latvia, moreover, only in cogeneration stations.

As previously mentioned, biomethane can be used to generate heat and electricity. It can be added as an impurity to natural gas, reducing its impact on the environment, as well as in the transport sector, for the operation of gas vehicles.

There is no unequivocal view of bioenergy in the world. The treatment of bioenergy mainly depends on the resource. To be considered environmentally friendly, bioenergy must be produced from raw materials from which there is no possibility of obtaining a higher value product, and it must also help reduce the amount of GHG emissions generated. Currently, biomethane corresponds to a sustainable energy source in EU legislation. Therefore, several EU and Latvian planning documents envisage the development of biomethane generation from manure, thus reducing GHG emissions in the agricultural and energy sectors.

Evaluation of bioenergy

The most popular technology for obtaining geothermal energy in companies is ground source heat pumps. Heat pumps are used not only for heating commercial and public buildings, but also for production processes. Heat pumps consist of several parts: the pump, the heating system pipes (located in the building), the heat production pipes (located underground), the evaporator, the compressor, the expansion valve, and the heat carrier. The main part of the equipment is the pump, which ensures the pumping of heat sources from the ground to the building, as well as the circulation of the heat carrier in the heating system. Underground pipes for heat extraction can be placed in several ways – vertically, horizontally and in loops.

It is not necessary to pump hot water or its steam out of the ground to operate the geothermal heat pump. These heat pumps absorb the heat that is in the soil. The principle of operation of heat pumps is similar to that of refrigerators – heat is received from the ground and the building is heated with it (in a refrigerator, heat is taken from products and discharged into the kitchen through the cooling element at the back of the refrigerator). In summer, the heat pump can cool the building as well.

Electricity is required for the heat pump to operate and ensure the flow of the heat carrier in the heating system. Heat pumps with a higher COP work best. It shows how many units of heat the device generates by consuming one unit of electricity. It should be remembered that when the outside air temperature drops, the ground temperature also drops and, therefore, so does the efficiency of the heat pump.

Evaluation of geothermal energy