Today there is a general global trend towards environmental awareness, and renewable energy sources (RES) are under close scrutiny. All of RES contribute something positive compared to fossil fuels — reducing carbon emissions, lowering fuel prices, lowering pollution levels, etc. According to the International Energy Agency (IEA), more than 25% of global electricity is currently supplied from renewable sources, with this percentage growing rapidly. When we hear about renewable energy, we subconsciously understand that it referring to obtaining energy from natural resources such as sunlight, wind, rain, waves, tides, the heat of the earth, as well as from biofuels (wood, vegetable oil, ethanol). We call these renewable energy sources traditional. And what do we know about non-traditional or non-standard RES? What technologies the mighty of this world invest in? Is it realistic and rational to use such sources in everyday life for energy? Let’s get it together.
According to the IEA market analysis, a significant increase in the share of renewable energy sources in the global energy balance is projected for the next 5 years (2019—2024). And the solar energy will be the front-runner (Fig. 1, 2).
As for non-standard RES, the selection is opened by lightning energy. Its essence is lightning to catch for its further conversion into electricity. The difficulty lies in this: it turns out not so simple to capture and redirect a discharge. It requires using powerful and expensive equipment. Moreover, only in the special parts of the world do thunderstorms occur frequently.
Venezuela is one of the most productive places on the planet in terms of the number of lightning storms: in some parts of the country, the sky is illuminated by a bright discharge of almost 300 nights a year. By the way, once navigators used these flashes of light like a beacon. A vivid example of this is Lake Maracaibo in the state of Zulia, Venezuela (photo 1), the number of days with thunderstorms here varies from 70 to 297 days a year.
The mouth of the reservoir on three sides is surrounded by mountain ranges. When cold, dry air from the mountains meets hot and humid air from the lowlands, it is creating ideal conditions for the lightning occurrence. Thunderclouds reach a height of more than a kilometer, and lightning flashes an hour after the formation of these clouds. Their frequency is rapidly increasing to 200 flashes per second. These phenomena can continue for 10 hours.
As a rule, each lightning carries about 500 megajoules of energy, which equals 38 liters of gasoline. This is enough to provide electricity for a medium-sized house for a week or to boil about 1,500 teapots of water.
According to research by American scientists, a single lightning strike can power the entire city of Santa Fe for about a minute. However, to accomplish this, it is necessary to solve the problem with lightning capture as an energy source, more precisely, with its getting into the receivers.
Even if people could compel the lightning to strike where necessary regularly, the problem of the intensity and duration of the strike would remain. Lightning is incredibly powerful and insanely fast: each stroke is about 50 thousand amperes to the battery in just microseconds. No existing battery can withstand this onslaught.
This is the accumulation of excess energy by liquefying air in refrigeration units. A cryogenic power plant accumulates energy from renewable energy or off-peak generation, liquefying air. When liquid air is heated, it expands and can drive a turbine to generate electricity.
One of the world’s largest installations for storing cold energy was commissioned in 2016 near Manchester, United Kingdom (photo 2). This 5 MW power plant can serve up to five thousand homes in three hours.
Highview Power Company, who developed the installation, believes that the technology incorporated in it has great potential for long-term use with environmental energy sources. The technology is similar to a localized version of a pumping hydraulic system.
Figure 3 shows how the refrigeration unit works. The cryogenic storage operates using renewable or off-peak electricity to cool the air to -190 ° C, which turns it into a liquid mixture of nitrogen and oxygen, which is then stored in an insulated tank, similar to a large thermos flask. To release stored energy, liquid air exposure to environmental conditions, causes it to expand back into the gas. A huge increase in volume, about 700 times, using to drive a turbine to generate electricity.
However, Highview Power’s cryogenic batteries are some of the most developed long-term storage solutions that can be located anywhere you need them. Working with private funding of $ 50 million, the company has already built five plants in its country, several more are under construction, and it is planning to build in the United States.
At the end of October 2019, representatives of Highview Power announced that they plan to build their first major commercial facility in the UK – 50 MW / 250 MW * h (photo 3). According to Highview Power, the plant will be located at the site of a decommissioned thermal power plant in northern England.
According to a recently published study in the academic journal Energy, energy storage in mountains by gravity can be a viable way of storing electricity for a longer time and on a larger scale than storing in lithium-ion batteries.
The use of mountains for storage can combine with hydropower and can be economically attractive for microgrids, islands, and areas with high-energy costs, according to a study published by the Austrian scientific group International Institute for Applied Systems Analysis (IIASA).
Researchers suggest that a motorized system, similar to a lift, can pull containers of sand to a crane on top of a mountain. Then the sand can be sent back from the mountain, driven only by gravity, while generating electricity.
The authors of the study argue that the Mountain gravitational energy storage (MGES) may open up opportunities for long-term storage in new places. Hydropower storage, one of the most common forms of energy storage currently in operation, is an example of long-term storage and can use stored energy for 6 to 20 hours.
One of the advantages of the gravitational energy storage system is that the sand is cheap and, unlike water, does not evaporate, so potential energy is never lost and can reuse countless times. This makes MGES a very attractive option for arid regions.
Energy Vault, the Swiss company, proposed gravity-assisted power storage, the basic concept similar to gravity storage technology. The company recently received over $ 100 million dollar investment from Japan’s SoftBank Vision Fund. This technology generates electricity through gravity, dropping concrete blocks in the tower.
The mechanism proposed by Energy Vault is a steel six-armed crane with a height of almost 122 meters (Fig. 4). Using proprietary software, the towering structure orchestrates the placement of 35-ton blocks of concrete in response to drop-offs in demand and fluctuations in environmental conditions.
When energy demand decreases, cranes surround themselves with concentric rings of concrete bricks, lifted by the leftover energy from the surrounding wind and solar farms. As demand increases, cranes begin to lower the bricks, which power turbines, converting kinetic energy into electricity that gets pumped back into the grid.
Another of the RES know — how is mirror mosaic in the Mojave Desert (photo 4). This is part of a Heliogen owned enterprise. This company is engaged in solar energy, developing a method of sunlight concentration.
The Array of mirrors directs light toward a single point on the tower. Once the light hits, liquid in the tower heats up, and thermal energy fuels a heat engine.
While solar farms produce electricity for homes and businesses, this process is designed for manufacturing plants that produce cement, steel, or petrochemicals. The production of these materials requires a temperature of at least 1000 ° C, while other renewable energy technologies are not able to generate that kind of heat. One of the richest people on the planet, Bill Gates is also among the first investors. In a statement, Gates called the company’s technology “a promising development in the quest to one day replace fossil fuel.”
Heliogen`s team, which includes scientists and engineers from Caltech and MIT, uses computer models to program mirrors to reflect light at precise angles. That ensures all the solar beams reach the exact same point, resulting in extremely high temperatures.
As we can see, time and technology do not stand still — everything is moving, changing and improving. Soon we will hear about new inventions that will help people make planet Earth cleaner and greener.