ALTERNATIVE ENERGY SOURCES
Earth’s natural resources are diminishing every year. Non-renewable energy sources such as coal, oil, and natural gas are the primary fossil fuels used today for energy production. The pollution generated through this process later infiltrates the air, soil, and water. Reducing carbon dioxide emissions is a priority in international environmental policy. Achieving set goals possible through the replacement of fossil fuels with renewable energy sources.
The utilization of renewable energy sources (RES) is not associated with a prolonged deficit, as their resources renew relatively quickly (renewable raw materials). Such sources include the sun, wind, water (rivers, tides, and ocean waves), as well as nuclear energy in a closed fuel cycle, biomass, biogas, bioliquids, and biofuels. Renewable energy also encompasses heat obtained from the ground (geothermal energy), air (aerothermal energy), and water (hydrothermal energy).
Conducting a broader analysis of renewable energy sources (RES) in terms of emissions and their availability, all RES can be divided into two categories:
- Material-Based Sources: These utilize fuel combustion processes (nuclear energy, biomass, biogas, and biofuels) or access to them is licensed by major institutional providers (rivers, tides, and ocean waves),
- Phenomenon-Based Sources: These leverage natural and generally available phenomena in the environment, such as solar radiation, wind, geothermal energy, aerothermal energy, and gravity.
Alternative Energy (AE): It represents a natural way of obtaining energy, independent of major institutional providers, derived from regularly occurring processes in the environment, used for the production of low-emission energy.
The main differentiator of AE is the systematic replenishment of the energy carrier from utilizing physical phenomena in the environment, making them practically inexhaustible.
In summary, renewable energy sources are a subset of alternative energy sources that focus on renewable energy sources such as solar, wind, water, geothermal, and biomass energy. Alternative energy sources are a general term encompassing diverse energy sources, both renewable and non-renewable, serving as an alternative to traditional fossil fuels.
The adoption of alternative energy sources is embedded in the concept of sustainable development and is crucial for the implementation of the energy transition in the economy. This transition aims to provide humanity with a secure and long-term future, as energy from alternative sources is and will likely continue to be widely used to power industrial facilities, public utilities, and households. These entities act as both energy producers and consumers, enabling significant savings on electricity consumption costs, as well as the final energy needed to provide heat and cooling.
With the current state of technology, a variety of generators are employed for the conversion of energy derived from alternative energy sources. These include small wind turbines, wind turbines, photovoltaic installations, solar collectors, heat pumps, and Free Cooling systems.
AUTONOMOUS ENERGY SYSTEMS
Sustainable economic development requires the rational and thoughtful utilization of renewable energy sources. Despite their advantages, renewable energy sources are characterized by seasonality and significant instability. To enhance the efficiency of harnessing the potential of renewable energy, autonomous power systems are employed.
Autonomous power systems (off-grid) are independent power sources that do not require connection to the power grid. Such a system operates in an isolated configuration and is used for reliable delivery of electrical energy from renewable sources. Autonomous power systems can be applied as an alternative power source for residential installations but also in the context of providing free power to energy-efficient industrial installations and anywhere the power grid does not reach.
Autonomous energy systems are also known as microgrid systems or autonomous microgrids. These are small, independent energy systems capable of generating, storing, and managing electrical energy at the local level. These systems are typically used to power separate areas or buildings and operate independently of traditional, centralized power grids.
The main features of autonomous energy systems include:
- Renewable energy sources: Autonomous energy systems often utilize renewable energy sources such as solar panels, wind turbines, or geothermal energy to generate electrical power. This allows for sustainable and environmentally friendly energy sources.
- Energy storage: Autonomous systems are often equipped with batteries or other energy storage devices that allow for the storage of excess energy, which can be used during periods of low production, such as at night or when there is a lack of sunlight.
- Energy management: These systems are equipped with advanced energy management systems that control the generation, distribution, and consumption of energy to optimize its use.
- Resilience to failures: Autonomous energy systems are often designed with resilience to failures in mind. In the event of a failure in the main power grid, a microgrid can still supply energy locally.
- Integrated technologies: These systems can integrate various technologies, such as renewable energy, smart meters, battery management systems, and control systems, to ensure efficient and reliable energy delivery.
Autonomous energy systems find applications in various environments, including remote areas, islands, rural areas, industrial and commercial facilities, as well as residential buildings. They represent an innovative approach to sustainable and independent electricity production, contributing to reducing dependence on traditional energy sources and addressing climate change.
Autonomous power systems can be combined to create a local network that automatically responds to energy shortages at different nodes by regulating the flow of electrical energy.
The basic system consists of a main power source, an additional energy source, an emergency power source, an energy storage device, a weather station, and a controller. The primary energy source accounts for 60-80% of the generated electrical energy and can utilize photovoltaics, small wind turbines, or cogeneration.
Additional sources account for 20-40% of the generated electrical energy supplied from a different type of renewable energy than the primary source. The energy mix depends on the geographical location of the system. The emergency power source can be implemented as an on-grid connection or using a backup generator. The energy storage system consists of batteries or supercapacitors and hydrogen energy storage facilities.
Hydrogen exhibits high efficiency, in part because it has the highest heat conduction coefficient among all gases. When burned, hydrogen yields about three times more energy than other fuels such as gasoline, propane, or methane. However, it has played a relatively small role in Europe’s power sector. In 2019, it accounted for less than 2% of the total energy production, mainly used in refineries, petrochemical plants, and metallurgy. Nevertheless, as ambitiously outlined in the European Union’s plans for 2050, it may constitute over 25%.
The role of hydrogen in the power system is becoming increasingly significant, especially in the context of efforts towards sustainable and clean energy production and the reduction of greenhouse gas emissions.
A hydrogen energy system can serve several roles and functions:
- Energy storage: Hydrogen can act as an energy carrier, allowing the storage of excess electrical energy generated from renewable sources such as solar and wind. Hydrogen can store energy chemically and deliver it when needed, stabilizing electricity supply and adapting to changing weather conditions.
- Electricity generation: Hydrogen can be used in fuel cells to produce electrical energy. Fuel cells transform hydrogen and oxygen into electrical and thermal energy without emitting harmful substances. This is particularly useful where direct generation from renewable sources is not possible, such as at night when there is no sunlight or wind.
- Transportation: Hydrogen can be used as an energy carrier in transportation, especially in hydrogen-powered vehicles. Fuel cells powered by hydrogen enable the production of electrical energy that drives the vehicle, contributing to emission reduction and improving the energy efficiency of transportation.
- Industry: Hydrogen can be employed as a heat and energy carrier in industrial processes, such as metal reduction and the production of heat and steam in industrial plants.
- Sustainable development: Hydrogen is a clean energy source that does not generate carbon dioxide or other harmful substances. Its use contributes to reducing the negative impact of human activities on the natural environment and promotes sustainable development.
With the dynamic growth in demand for renewable energy, there is also an increasing need for energy storage, highlighting the importance of hydrogen as a storage medium. For a long time, hydrogen has been considered one of the most promising substances for chemical energy storage, which can be converted back into thermal and electrical energy. This applies not only to large-scale industrial or energy installations but also to end-users.
The more we talk about hydrogen, the more we recognize its advantages over other alternatives. It’s worth noting that there are currently various energy storage technologies, differing primarily in capacity, energy storage time, charging and discharging times, and, of course, installation costs. Battery systems dominate among them, but there are also technologies utilizing kinetic and thermal energy, compressed air, or pumped hydroelectric storage. However, their average energy storage time remains relatively short, along with limited storage capacities.
In the case of batteries, energy is typically stored for several minutes to a few days, usually within the range of 10 MW. Kinetic energy provides average storage up to 100 MW for periods ranging from a few minutes to a dozen or so minutes. Thermal energy allows for average storage over 100 MW for periods ranging from a few days to a couple of weeks. Pumped hydroelectric storage, on the other hand, can provide even over 1000 MW for a few days. In contrast, hydrogen and hydrogen fuels, such as ammonia, stand out, enabling average energy storage up to 1000 MW over periods from several weeks to a few months. According to some analyses, with minimal losses, they can even allow for energy storage throughout the entire year. This becomes one of the key advantages of hydrogen in ensuring energy security.
Especially given the dominance of battery systems in the market, there may eventually be a shortage of lithium for battery production, including technologies like LFP (lithium-iron-phosphate), NMC (nickel-manganese-cobalt-oxygen), LCO (lithium-cobalt-oxygen), or LMO (lithium-manganese-oxygen). The demand for this resource is steadily increasing, partly due to the development of electromobility. Experts emphasize that with the current demand-driven increase in battery production (96 million units in 2018), lithium reserves estimated at 40 million tons could be depleted within the next 300 years—a somewhat optimistic scenario. With estimated reserves at 11 million tons, the depletion time frame is around the next 100 years.
For hydrogen production from renewable energy sources, the electrolysis method is employed. It involves the separation of water into hydrogen and oxygen under the influence of electric current. This results in the production of zero-emission green hydrogen, which can be used directly or stored for later use or converted back into electrical energy.
Several hydrogen storage technologies are currently available and continuously improved to provide the highest efficiency in storing hydrogen with specific physicochemical properties, ensuring safe usage. Hydrogen can be stored in specially adapted pressure vessels (compressed and liquefied), underground salt caverns (compressed and industrially stored), hydrogen-rich chemical compounds, in the form of metal hydrides, and in porous substances.
The re-conversion of hydrogen into energy is possible through hydrogen fuel cells, a much more efficient method than direct burning. The efficiency of fuel cells currently stands at around 60% (electric current), with the remaining 40% being released as heat.
In addition to hydrogen fuel cells, various types of power plants are used. According to the definition, a power plant, sometimes also referred to as an engine room, is a set of devices belonging to a larger system that converts a certain type of energy into mechanical energy.
In practice, we encounter various types of power plants. In marine propulsion systems, thermal engines are commonly used to drive the ship’s propellers. A steam power plant consists of a boiler room and an engine room, where electrical energy is generated for the ship’s propulsion. In addition to the main power plant driving the propellers, auxiliary power plants exist, containing, among other things, power generators and pumps.
In a thermal power plant, the term “power plant” often refers to a dedicated building housing a steam turbine, generator, and auxiliary devices such as control systems, pumps, pipelines, steam boilers, condensers, regenerative heat exchangers, etc.
A wind power plant includes the nacelle, housing the rotor, gearbox, generator, and control system. Although colloquially, the term “wind power plant” is sometimes used interchangeably with “wind turbine”.
A hydroelectric power plant consists of a water turbine, gearbox, generator, and auxiliary devices.
An innovative concept in the generation and storage of electrical energy is the Emission-Free Power Plant (BSE). BSE is used for converting useful electrical energy in autonomous power systems and hydrogen production through electrolysis from large-scale renewable and alternative energy installations. By investing in this field, the aim is to meet the needs of cities, municipalities, businesses, and end-users associated with energy and climate transformation.