Energy storage systems for homes

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Written By Marc Helman

Tackling new challenges with a passion for the environment.

With increased interest in sustainable energy solutions for homeowners, there is a growing need to provide more efficient and cost-effective ways of storing energy generated by solar panels or wind turbines. The same goes for community microgrids, for example.

Below are a few options that may be worth considering if you’re looking to store excess energy from your home’s renewable energy source.

There are two main ways to store energy: chemical and mechanical.

Chemical means storing energy by converting it into another form, like hydrogen gas.

Mechanical means storing energy mechanically, which involves moving something back and forth. The best way to store energy is through a combination of both methods.

Chemical storage

If you want to go down the path of chemical storage, then look into batteries. You could even build a solar panel on top of a car battery if you wanted to make it efficient.

Since we are talking about storing energy for home use, let’s look at residential battery storage systems. 

Residential battery storage systems

The most common type of residential battery storage system is a lead-acid battery, which stores energy in chemical form.

The batteries are used to store electricity generated by solar panels or wind turbines and then use the stored power to run appliances such as air conditioners or electric heaters when needed.

A typical home has several different types of batteries that can be used to store excess energy from renewable sources. Some of these include:

Lead-acid batteries

These are the oldest type of rechargeable batteries available. They have been around since the early 1900s and are still widely used today. They are inexpensive but require periodic maintenance and replacement.

Nickel cadmium (NiCd) batteries

These batteries were developed in the 1970s and are commonly found in portable devices like cordless phones. NiCds are less expensive than lead-acid batteries and do not need regular maintenance. However, they contain toxic materials and should only be disposed of properly.

Lithium-ion batteries

These batteries are more expensive than nickel-cadmium batteries but last longer and are safer because there is no risk of explosion or fire. They also have a higher capacity than other types of batteries.

Hydrogen Fuel Cells

While not a typical household battery, fuel cells are becoming an increasingly popular option for those who want to cut their carbon footprint.

A fuel cell uses oxygen and hydrogen to create electricity via a chemical reaction. Because the process produces water as a waste product instead of dangerous gases, fuel cells are considered environmentally friendly.

However, because hydrogen is flammable, care must be taken to prevent fires.

Fuel cells work well in stationary applications like backup power supplies for hospitals and data centers. They’re also used in cars and other vehicles where the electric motors run off hydrogen fuel.

Mechanical storage

Mechanical energy storage would involve things like flywheels, compressed air, hydraulic pumps, or thermal storage.

Mechanical storage uses mechanical components to move energy back and forth. This includes things like flywheels, water pumps, and compressed air.

Flywheel Energy Storage System

One example of this kind of storage is a flywheel energy storage system. A flywheel is an object that spins very fast and efficiently stores kinetic energy.

When the spinning slows down, the flywheel continues to spin until its speed drops below that of the surrounding environment.

At that point, the flywheel releases all of its energy as rotational energy. Flywheel technology was first invented in the 19th century but didn’t become popular until the 20th century.

In the context of residential energy storage, a flywheel could potentially provide a way to store energy during low demand and release it at peak times.

Water Pump Energy Storage System

Another example of mechanical storage is a water pump energy storage system. Water pumps transfer energy from one place to another based on how much pressure is applied.

If you’ve ever driven your car up a hill, you may have noticed that the engine seems to work harder when you get to the top of the hill.

That’s because the engine must push against gravity to keep moving forward. The engine must apply more force to the wheels to overcome this resistance.

Similarly, when a water pump transfers energy from one location to another, it applies extra pressure to the pipes that carry the water.

Compressed Air Energy Storage System

Compressed air energy storage (CAES) is similar to water pump energy storage. It works by storing energy in compressed air instead of water. CAES takes advantage of the fact that air can be compressed to about twice its normal volume.

To create a compressed air energy storage system, you would build a large underground cavern where air could be pumped into the space and stored.

Then, if the area needed additional power, the compressed air could be released through a turbine and generator to produce electricity.

The problem with this approach is that creating a large enough cavern requires a lot of land and pumping equipment. Additionally, the air must be compressed at a high pressure, which increases the energy required to compress it.

Thermal Storage

Thermal storage uses heat to store energy. Thermal storage works in two main ways: sensible heat and latent heat. Sensible heat refers to the ability to feel warmth or coldness. 

Latent heat refers to the ability of something to absorb heat without feeling warm or cool.

In residential energy storage, thermal storage involves using either hot or cold liquids to store energy. The liquid is heated or cooled depending on whether it’s being used to generate or consume energy.

For example, solar panels use sunlight during the summer months to convert water molecules into hydrogen and oxygen. This process creates steam, turning into a turbine to make electricity.

During the winter months, the same process happens in reverse. During the night, the sun heats the water inside the tank. When morning comes, the water is turned back into steam, which drives the turbine to make electricity. This method of generating electricity is called hydroelectricity.

While these methods provide an effective way to store energy, they also have some drawbacks. For instance, heating or cooling liquids requires a great deal of energy.

Additionally, while the temperature change between the liquid and gas phases makes the liquid useful as a source of energy, the temperature difference means that the liquid will expand when heated and contract when cooled. This expansion and contraction cause stress on the container holding the liquid.

Finally, there are limits to how much energy can be stored in a liquid. A typical household refrigerator stores about 1 kWh of energy per day: if we wanted to store the same amount of energy in our home, we’d need a tank that holds 10,000 gallons of water. That’s roughly equivalent to filling a swimming pool every day.

 Mechanical or chemical storage: which one is best for me?

When choosing between these two, you should consider how much energy you need to store. If you’re looking to store more than 100 kWh (100kW·h), mechanical storage may be better.

However, chemical storage will probably be cheaper if you’re trying to store less than 100 kWh.

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