6 Types of Solar Energy Storage Systems

Have you ever been told that you can comfortably store solar energy? There are about 6 different types of solar energy storage systems you can adopt at your convenience. This article has been created to enlighten you about them.

Energy storage is one of the beautiful intriguing inventions of mankind. It is one of the few benefits the earth has received from our activities. Solar energy storage systems make the use of solar energy more attractive. Since the sun produces in-hour radiation that is enough to meet our annual energy demands, extra energy can be stored up for use when there is no sunlight.

As a homeowner having solar panels, you have options that have been given in this article as ways you can store solar energy. These options include the use of turbines, off-grid energy storage, on the grid storage, production of solar fuels and solar ponds.

Alongside the benefit of having backup power in events of a power outage of the public utility grid, the application of any of the types of solar storage systems helps you take advantage of time-of-use (TOU) rates. TOU rates are the period’s utility grid companies charge higher for electricity due to high energy demands on the grid during those periods.

About Solar Energy Storage Systems

Generally, energy storage systems are put in place to capture electricity, store it as chemical, mechanical or thermal energy and release it back as electrical energy when needed. Energy storage saves up excess energy generated during peak periods for future use.

Different types of solar energy storage systems can be adopted to have backup power when the grid goes down and to reduce the amount of money spent on electricity bills.

How Solar Energy Storage Systems are Built

Before we look at how solar energy storage systems are built, we need to briefly look at the general ways in which renewable energy can be stored. Renewable energy can be stored chemically and mechanically. Storage is based on some physical principles of matter.

The first principle on which solar energy storage systems are built is that of temperature change in the material upon its heating or cooling. Matter experiences bulk heating, where the value of the stored energy is proportional to the specific heat capacity of the material used. This leads to a phenomenon referred to as sensible heating.

The second principle upon which solar storage systems can be built is that of matter being able to absorb or release latent heat upon phase transition. If a certain phase transition is accompanied by heat absorption, the reverse process will release the same amount of heat, so the energy can be stored as long as a certain phase of matter is sustained.

The third is based on chemical reactions. Here, energy creates chemical compounds with high-energy chemical bonds, which then release their energy upon disruption.

Energy can be stored through the formation of weak chemical bonds, such as through the physisorption of water molecules on silica gel. Energy can also be stored through the formation of stronger bonds, such as the oxidation of silicon into silicon oxide (chemisorption). Energy density is lowest in materials that store chemical energy due to physisorption, and highest in those that store chemical energy through chemisorption. The storage capacity of the storage system will be equivalent to the consumed heat or free energy of the reaction.

The fourth principle that can be used for solar storage systems is that of dissociation of electron-hole pairs in electrical energy storage devices such as batteries. Photons can be directly captured from the sun and stored in these batteries.

Some of these principles guide the construction of various types of solar energy storage systems.

6 Types of Solar Energy Storage Systems

The types of solar energy storage systems are:

  • Offgrid Solar Storage System/The Use of Batteries
  • On-Grid Solar Storage System
  • Hybrid Solar Storage Systems
  • Solar Fuels
  • Solar Ponds
  • Stratified Solar Energy Storage Systems

1. Offgrid Solar Storage System/The Use of Batteries

Those who use this type of solar storage system are not connected to the public utility grid. In order to use an off-grid system, you will need to have enough batteries for storage. Your solar system should also be built in such a way that your home will be powered throughout the year.

Batteries are categorized under the chemical methods of energy storage. They convert chemical energy to electrical energy. This is made possible by the electrochemical cells used in producing these batteries.

The electrochemical cells in batteries are two electrodes, a cathode, and an anode. These cells are also electrical conductors and are separated by a separator. The separator itself is made of

Also in the battery is the electrolyte (between the cathode and anode) composed of ions. These ions react with the conductive materials of the cathode and anode. This reaction creates an electric current in the battery.

Batteries are made of different materials, come in different sizes and brands. Based on the material used, we have

Lead-acid batteries are the oldest and cheapest batteries used in the storage of solar energy. However, they have a low depth of discharge thus, need replacement faster than other batteries. Lithium-ion batteries are better used as types of solar storage systems in residential homes. They are more expensive but, have a longer lifespan than their lead-acid counterparts. They also have a high energy density which makes them able to store energy in small spaces.

Nickel-cadmium batteries are next. They are common in large-scale energy projects as they withstand high temperatures. The toxicity associated with Ni-Cd batteries and the difficulty in the disposal of cadmium is a major constraint in the use of Ni-Cd batteries. Flow batteries are the largest and most expensive batteries. They are the best for a large-scale installation. They have a low storage capacity and charge-discharge rate.

2. On-Grid Solar Storage System

On-Grid storage systems are also known as grid-tied systems. This system uses a standard grid-tied inverter and does not have any battery storage. As a homeowner who uses solar energy, you can store some energy on the public utility grid. Excess solar energy generated in your home can be exported in exchange for some credits or feed-in-tariff (FiT).

Feed-in_Tariffs_(FIT) are fixed electricity prices that you will receive for each unit of electrical energy you generate from your home solar panels and store in the public utility grid.

For a customer who uses this grid-tied system, when the solar panels are producing more than they are using, you can send power back to the grid. When your load is more than what the sun is generating, extra power can be purchased from the public utility grid as well.

Before you go for this type of solar energy storage system, you need to understand that whenever there is a blackout, your panels will not supply you with electricity. This is for safety reasons because linemen working on the power lines need to know there is no source feeding the grid. This simply implies that you do not have the luxury of enjoying some power during a blackout.

This type of solar energy storage system is perfect for you if you want to lower your energy bill and benefit from solar incentives.

3. Hybrid Solar Storage Systems

A hybrid energy system is one whereby a combination of two or more energy systems is used for energy production. This could be a combination of solar technology and wind turbine for energy production.

The hybrid solar storage system can be a combination of solar storage batteries and the public utility grid. When this type of solar storage system is used, solar energy generated is stored up in batteries while the customer makes use of the public utility. When the energy in the batteries is used up, you can comfortably switch to the utility grid. On the other hand, when there is a power outage from the public utility grid, you can also switch to your batteries.

4. Solar Fuels

This type of solar energy storage system is still a work in progress. It is not very common in the commercial energy market presently. Solar fuels are synthetic chemicals such as hydrogen, ammonia, and hydrazine that are produced and stored for periods when there is no sunlight.

Production of solar fuels can be from electricity from solar panels (electrochemically), from thermal heat generated from concentrated solar power (thermochemically), artificial photosynthesis (photobiological), or from photons (photochemically). All these work by driving some chemical reactions that translucent solar energy to chemical energy.

Solar fuels can also be produced directly or indirectly. Direct processes produce solar fuels from the sunlight without intermediary energy conversion. Indirect processes first convert solar energy to another form of energy (biomass or electricity) and this energy is further used to produce a fuel.

During energy conversion, some amount of energy is lost. This is the reason why indirect processes are less efficient than direct processes. The indirect processes are however easier to implement. More research is being carried out by scientists on how to improve direct processes for the production of solar fuels.

Solar fuels can be stored for as long as possible. They can also be transported from one place to the other transported anywhere, making them a valuable and flexible resource for a more reliable electric power grid.

5. Stratified Solar Energy Storage System

Solar energy can be harnessed and used in two ways; using PV cells and using CSP. Stratified energy storage system works with CSP. It involves the storage of solar energy as thermal energy which can be converted to electricity when needed.

Here, hot water storage tanks also known as hot water cylinders, heat storage tanks, or thermal storage tanks are used for storing water for space heating or for domestic purposes.

The hot water is stored in an insulated tank for as long as. If the energy is to be used to generate electricity, the heat is used to boil water and the resulting steam drives a turbine that generates electricity.

6. Solar Ponds

Solar ponds also work with Concentrating Solar-thermal Power systems.

A solar pond is a body of water that collects and stores solar energy as heat. Its working principle is the reverse of natural convection. Naturally, when sunlight hits a saline pond, it first heats up the water at the bottom of the pond. This water becomes less dense and through convection, its molecules rise to the surface.

In the solar ponds, the reverse is the case. The ponds are built to impede convection. The pond receives salt in a quantity that is enough to completely saturate the water at the bottom. When the water gets heated, as usual, the highly saline and hotter water does not completely mix up with the less saline and cooler water at the surface.

Mixing is mild and convection occurs separately in the top and bottom water. This effect reduces heat loss greatly. The more saline water can heat up to 90 ℃ while the top maintains temperature as low as 30℃

Later, the more saline hot water can be channeled to a turbine which it turns to generate electricity when demand is high.

FAQs

How many solar energy storage systems are there?

Solar energy storage systems are not limited to the five discussed in this article. There are a good number of them, most of which are still being developed. This article explained the ones that are common in the commercial energy market.

What is the best way to store solar energy?

There is no best way to store solar energy. Your choice of a particular type of solar energy storage system should be guided by your needs, budget, and location. For buildings located far away from the public grid, off-grid storage systems will be suitable. Buildings that are already connected to the grid but need some backup power will require a hybrid storage system.

Is solar battery storage worth it?

Yes, they are. Batteries can keep you going during power failure from the public utility grid. Depending on your budget, you can buy batteries that have up to 7 years lifespan.

How long can solar energy be stored?

Storage systems have different energy and power capacities. Energy capacity (measured in kilowatt per hour) is the amount of energy that can be stored while power capacity (measured in kilowatt) is the amount of energy that can be released at any time. This determines how long a storage system can serve when powering the load.

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