Renewable energy is being widely used as a source of energy in the replacement of fossil fuel-generated energy. It will be great for the elimination of greenhouse gases from the environment. There are different kinds of renewable energies, like wind, solar, geothermal power. The most prominent among these is solar energy. Many countries are now adopting solar energy as an alternative source to meet their energy demands. Countries like Germany and the United Kingdom are already fulfilling many percentages of their need through this technology. China is leading in providing cheap solar panels all over the world.
Indeed, solar energy is gradually revolutionizing the energy world, but problems also exist. The energy generation capacity is going up, and prices are reducing, but the one thing that keeps it holding back is its storage problem. You cannot always get solar energy in the same capacity as there might be a cloudy atmosphere sometime or a night time. In this regard, you could not maintain the supply and demand balance.
The electric grids will be working well if there is a gap between supply and demand. Germany is already facing this problem as its capacity has skyrocketed and soon will meet half of its energy needs through solar power, but experts say any further installation beyond this point could cause permanent mid-day grid instability. Some ways have been devised to deal with this problem, like smart grid technology and storage through batteries, but some loopholes also exist. Let’s have a look at the storage problems of solar energy.
Storage energy storage problems
The main source of solar energy storage is batteries. But we could not get reliable batteries for properly storing solar energy. The people in the energy industry are trying very hard to get the most efficient batteries. The invention of lithium-ion batteries has been a huge success in this regard. These are extremely good for medium-scale applications. For instance, lithium-ion batteries in solar electronic devices like auto dark welding helmets have been proved very helpful as they can recharge your device quickly and offer a lot of power. These batteries are also being used in electric car batteries.
But if you talk about storing solar energy from big commercial farms, you need to have a warehouse full of massive batteries. The problem is the bigger the battery gets, the less useful it becomes. The storage at this level could also escalate the dangerous situation when you store it for a longer time.
Despite having these loopholes, the batteries are still being used in storing large off-grid energy. Some technological advancements have also been made in this regard, like using low-cost battery material, including aluminum, nickel-iron, lithium-ion replacement with lithium-sulfur, and the initiatives like Giga-factory for reducing battery costs.
Major challenges while dealing with a PV system
You have to face a lot of challenges while dealing with solar energy or renewable energy systems. We will summarize these challenges to easily assess the intensity of these challenges and have a complete overview of these challenges. Let’s have a look at these problems.
Low capacity factor
You could not predict or get the required power capacity from solar or wind power farms as you have to face many variations according to the environment. Thus, these would be only helpful when the sun or wind cooperates with you or according to your expectation, but if they are not, then you could not run the power plants at their original capacity.
In conventional or traditional power plants, you can easily control the frequency, and the voltage support would also be good enough. But in the solar energy case, you cannot easily control these factors, or you have to make a big investment for this purpose. For example: if you want to run a welding machine on solar power then you have to install enough panels and batteries to synchronize the power supply.
The intensity of the sun might be stronger at some places as compared to others. Some areas also lack the necessary transmission infrastructure to let the power reach where it most needs. Thus, it depends on location to location. If the sun is good at some location and the transmission infrastructure is also available, then the situation is ideal for generating and transmitting renewable energy from solar power farms. Otherwise, you have to face a lot of problems while maintaining the balance between solar energy generation and transmission.
It has become one of the most vexing and the biggest issues while dealing with solar energy problems. There are a lot of variations you have to face in this kind of energy generation. Sometimes, you get more energy than your required capacity, and sometimes, there will be a shortage of energy.
You could not predict the condition of the environment for days ahead with perfect accuracy. Thus, there must always be excess energy in reserves to meet all of your needs.
Potential solutions for dealing with solar energy storage problems
Potential solutions that we think are promising:
- Lead-acid batteries model
- Smart grid system
- Sensible heat storage system
- Mechanical ways to store energy
- Underground thermal energy storage system
- Electrochaea plants
Let’s dive into each one.
Lead-acid batteries model
Lead-acid batteries are widely being used as a storage device for the solar system. You can easily store excess energy produced by either PV solar system or by DG in these batteries. These batteries are good because they are easily available anywhere in the world, or the initial cost of these batteries is also quite lower.
Smart grid system
There are new kinds of electricity grids or smart grids available in the market, self-balanced or self-healing networks. In these grids, the energy production is optimized according to the prediction model and supply-demand response algorithms.
In this system, the energy producers can easily send all the excess supply to temporary storage sites, which is used when the electricity demand is at its peak. In this case, the intermittent energy producers don’t need to have their own storage devices as they are directly connected with the grid, which acts like a giant battery. You can also store your solar energy here for utilizing it at night times when the sun would not be available.
In this regard, many countries have also introduced smart metering devices for all households. With this technology, you can easily send the additional energy to the national grid after meeting your need and utilize this energy at night when you don’t have energy. In this way, the administration can also analyze the consumption habit of end-users and optimize the flow.
Sensible heat storage system
For large-scale energy storage, there are some liquids and solids available which can store sensible energy. Molten salts, pressurized water, heating oils, and liquid metals are good examples of liquid storage solutions for applying power to large-scale power plants. These are also good heat transfer fluids. In this regard, a two-tank TES system is being deployed for the large-scale concentration of solar power.
Solid, sensible heat energy storage is a little bit complex as you need to have an additional heat transfer fluid for transferring energy to the storage media and recover it from the solids.
Fire bricks and metals are the two main devices for solid storage solutions. Firebricks are good because they have alumina, silica, clay, and magnesite and metal constitutes steel and cast iron. In this case, the energy density depends upon the specific heat, material density, and temperature difference. Owing to this, molten salt is the most preferred choice as you can easily heat it to a high temperature without any degradation, but it also has a limitation of a higher freezing point.
For solids, firebricks are better than metals when it comes to cost, but the metals also have much higher energy density. As far as the selection of the particular material is concerned, it all depends upon the operation and process conditions. The traditional power plants operate at lower temperatures and only need to have pressurized water as a coolant, while the advanced power plants may use molten salts as a source of heat transfer.
Mechanical ways to store energy
Other than batteries, there are also many other mechanical ways to store excess energy. One of them is the water pumping. You can pump the water from any ground to the elevated lakes and latterly use its potential energy for various purposes. You can also generate power from this system.
Another way to store the energy mechanically is by compressing the air. Compressed air is widely being used in the world, especially in the big industries for valve control systems. In this case, you can apply your excess by compressing the air and latterly use this compressed air for various purposes. High-speed rotating disks are also a good source of the excess energy storage system.
Underground thermal energy storage system
All the above-mentioned mechanical ways are good enough for storing energy, but you cannot store energy between seasons through these ways. It is a problem the same like you have to face in the case of batteries. However, the thermal underground energy storage system is the best system for dealing with inter-seasonal problems.
In the depth of the earth at about 15 meters, the earth’s temperature remains the same at all the places like 10-degree centigrade. There would be natural insulation under the ground and you can easily utilize this system for storing excess energy. Several pilot projects in the world are utilizing this technology.
In this system, the solar panels use all the excess energy in heating gravels, water stored underground, and carrying chemicals. In this way, you can store heat for months and deliver it through heat pumps whenever you need it in nearby homes. It would be the best source of energy for running air conditioners. You might also have faced some problems while utilizing this system like it may be expensive to build or a space issue. Natural losses would also occur while transferring the heat from one place to another.
The electrochaea system is also being widely used globally to produce renewable methane, which can easily store excess solar energy. You can utilize this gas for running boilers, power plants, cars, and buses. It would be cleaner fuel as compared to coal or oil with the fewest emissions. Methane is also easily storable. There are different underground storage sites across Europe to store this kind of energy. For one unit of energy fed into the system, you can produce 0.75 units of energy in the form of renewable methane.
It might not be as efficient as lithium-ion batteries, but you can store energy indefinitely in the form of methane. It is the biggest advantage of this energy over lithium-ion batteries. It doesn’t degrade into other chemicals. You can easily resolve your inter-seasonal storage problems with the help of this system. Electrochaea plants could also exist anywhere from the solar farms. There is no restriction of closeness in this regard. The excess electricity could also be extracted from anywhere in the grid.
All the above mentioned potential solution for storing excess solar energy might not be the only solution for storing this kind of energy. Still, these are the most efficient ones, which we have tried our best to explain.