A crane stores energy

How concrete cube towers can store green energy and supply it to the electricity sector in Israel when needed

Dr. Daniel Mader, Angle - news agency for science and the environment

Renewable energies produced from the radiation of the sun and the wind are currently the most viable solutions for producing energy for human needs. Their environmental impact - on climate change, air pollution, water pollution, use of resources, damage to ecosystems and damage to health - is minimal compared to the damage produced by fossil fuels such as natural gas, oil and coal. Also, in recent years the trend has reversed, and generating electricity from the sun and wind has become cheaper than fossil fuels.

However, the weak point of renewable energies is the fact that "they cannot be trusted". That is, they usually do not produce electricity at a fixed rate known in advance for a long period of time, for the simple reason that the sun does not shine throughout the hours of the day, nor does it shine with the same intensity during the day, when clouds or dust hide it. The strength of the wind also changes frequently and sometimes unpredictably. That is why there are limitations on the relative share of these energies from the entire electricity sector: it is necessary to invest in a special electricity infrastructure that can deal with this volatility, and it is necessary to keep a significant part of the electricity sector operating using fossil fuels, hydroelectric energy or nuclear reactors as a backup.

A solution to this central problem is energy storage: energy that is produced during hours when there is wind or sun is stored, and is used later, when there is no wind or sun. We know such small solutions from our daily lives, in the form of electric batteries and accumulators. However, to supply electricity to homes, buildings and cities, much more extensive solutions are needed. Therefore, there is currently a race to develop various means of storing energy on a large scale - and a new development by a Swiss start-up company, which makes smart use of technology that already exists today, is another step on the way to their application.

Generate electricity from water

In the technological race to find solutions for energy storage, sophisticated technological developments often make headlines, such as huge batteries based on metals or various organic materials, or batteries based on flywheels (rotating mechanical components used for energy storage). These solutions attract a lot of media attention and therefore also the most investments; However, these solutions are still under development, and most likely they will be very expensive, at least in the first period of their operation, due to their complex and long development. This phenomenon can be seen happening in the car market: hybrid and electric cars are still very expensive, which makes it difficult for them to penetrate massively into world markets.

On the other hand, less sophisticated solutions already exist today, such as heat or cold storage, and potential energy storage of weight at high altitude (more on that later). But these have not yet been used on a large scale. A solution of this type already exists today, even in Israel, and is known as pumped storage: water is pumped from a low reservoir upwards and stored in a high reservoir when there is an excess of electricity in the network. When there is a need for electricity in the system, electricity is produced from the water fall into the lower water reservoir through a turbine that generates electricity.

This system has an advantage due to the short start-up time that allows electricity to be generated within seconds of starting the system (unlike coal and other power plants, which require a much longer initial start-up time - long minutes and even hours) and its efficiency is relatively high and stands at 80 percent - that is, if a ton of water is pumped into the reservoir The top, when it is released down, receives 80 percent of the energy invested in raising it, while 20 percent of the energy is lost due to the friction between the parts of the system and due to loss of water in the form of evaporation or seepage. Other disadvantages of the process are the need for an extensive infrastructure of reservoirs and tunnels, which takes a long time to build and which harms nature - toxic substances may seep into the groundwater during tunnel mining, and water pumping during mining may damage the groundwater balance. In addition to this, in order to establish the system, areas with height differences of hundreds of meters between them are needed, such as a mountain near a valley, or a plain with a deep mine; In order for the entire Israeli electricity network to rely on renewable energies and pumped storage, tens of square kilometers of pumped storage reservoirs will be needed. Land is an expensive resource that is not sure if it will be possible to provide in the small and dense Israel, which is not surrounded by towering mountains.

50 percent cheaper than any other technology

A new development by the Swiss start-up company Energy Vault may be able to provide a cheaper and greener alternative to the pumped storage method. The company recently developed an automatic crane, which by creating piles of concrete blocks - just like Lego - manages to store potential energy, and turn it into electrical energy when needed, which can be fed back into the electricity grid.

How It Works? very simple. The crane creates piles of concrete blocks while using excess electricity that exists in the general electricity grid (for example during the afternoon when the production power of solar energy is at its peak). An electric motor lifts the cubes up and places them up the stack. When additional electricity is needed for the grid, the crane grabs the cubes from the top of the stack and releases them towards the ground (when they are connected to a cable that is connected to the generator, turns it and produces electricity), in an action that converts the potential energy (height difference) into electrical energy - similar to the pumped storage system mentioned earlier.

How It Works? The crane of the company Energy Vault

Each crane can operate automatically when it receives a command to store or release energy. The automatic system remembers where it placed each cube, and where it should place the next cube in the most efficient way. The system is modular and can be built in several sizes. Each crane is able to store energy in the amount of 10-35 megawatt-hours (MWh) and more, and supply energy with a power of 2-5 megawatts. This system size is excellent for modular installation in many sites, without occupying a large area (in contrast to pumped storage that needs extensive and "special" areas such as mountains next to valleys). In this system, energy can be stored for an unlimited time, without energy loss, but while maintaining a quick response time of tens of seconds when it is necessary to inject electricity into the grid.

A disadvantage of the new development is that it is not possible to build very large systems from it, similar to a single pumped storage reservoir. However, tens or even hundreds of such automatic cranes can be controlled by one person in another control room. Therefore, the operating expenses of this system are extremely low, and each system has a lifetime of 30 years or more, with 90 percent efficiency.

Since this is an incredibly simple system, and since all the parts of the system have been in human use for decades and are stable and reliable (concrete, steel, cranes), the main development is creating the appropriate software for automating and optimizing the system. According to the company, the price of this system is currently at least 50 percent cheaper than any other storage technology on the market. Building the system is relatively simple and fast. The concrete blocks can be produced on the construction site itself, or transported to it. The energy storage material (the concrete) does not disappear from the system over time, so it does not need to be renewed, unlike pumped storage, where the water evaporates and seeps out of the system. It is convenient to set up the system in any industrial area or in an urban area with high construction (installation in an urban area with low construction or in open areas will cause landscape damage).

At the end of the system's life, all its parts can be easily reused. You can even use heavy waste to create the cubes, instead of landfilling. For example, to use a mixture of coal ash, construction waste, crushed asphalt and more. The system is safe to use, without the risk of leaking dangerous substances and without the need to use high temperatures. Theoretically, these facilities can even be built underground. Although their maintenance and construction will be more complicated and expensive, this way it will be possible not to waste space on them that could be used for other alternatives, and they will even be immune to combat incidents.

to change the rules of the game of the electricity grid

Israel currently relies on an electricity network with a capacity of about 15 gigawatts ~15 GW, which consumes about 65 terawatt-hours ~65 TWh of electricity per year. If Israel's entire electricity production system is based on renewable energies (mainly solar), which, as I remember, do not operate at a fixed and known rate in advance and therefore must be stored, 5,000-10,000 such cranes will be able to store and supply all of Israel's electricity consumption for over 24 hours, without any other power source. Such a distributed system could even save the construction and maintenance of an expensive electricity transmission system that covers the entire country.

Today, the electricity sector in Israel is centralized and vulnerable. A localized damage to the Rabin power plant in Hadera, for example, whether as a result of war, an earthquake or a tsunami, can disable about 20 percent of the total scope of electricity production in Israel. A point damage to a gas supply rig or a main transmission pipe can paralyze the gas supply to 60-70 percent of the power plants and many factories. If Israel switches to generating most of its electricity from the sun on buildings, every city will be able to generate and store its own electricity. But even if not, it will be possible to store electricity from the main grid for every city. In the event of a shutdown of the national electricity system, each city can have a backup and can continue to function.

Moreover, about 11 percent of all electricity produced today is "thrown away", because the electricity grid always produces more electricity than the amount of consumption at the same time, in order to deal with sudden increases in consumption. The excess electricity is grounded to the ground, and energy storage will be able to store these excesses, making it possible to produce less electricity each day.

The technology of the concrete towers (or those similar to it) is expected to change the rules of the game of the global power grids. From centralized networks that rely on expensive and polluting fossil fuels controlled by corporations and states, to decentralized networks that rely on clean energy and energy storage for an unlimited time.