Types of Energy Storage for Residential Solar
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One of the most common solar storage options is battery backup; despite its commonality, it is oftentimes confused with backup/power supply. All batteries are a form of backup, but not all backup is battery-based.
The rule of thumb for remembering the difference is to think of battery backup as a bank into which you deposit solar power for use at the current time or a later date, whereas backup and power supply help provide a continuous flow of power to panels when the sun is out and shining.
Energy storage can store utility-scale power or charge a battery in a phone or laptop. It can provide power for anywhere from a couple of hours up to several days on end depending on your usage levels.
Determining which type of solar storage is best depends on the size of the project and the readily available storage options. Let’s take a look at some of these storage types and what makes each of them unique.
Energy Storage Device Options
Energy storage includes any device that can store energy. There are several different solar storage devices on the market.
Energy storage options can power the grid when regular electricity generation isn’t enough. They can also increase power continuity for renewable energy sources such as wind and solar.
While there are many energy storage options on the market, they all fit into three groups. These include thermal, mechanical, and battery.
Thermal storage systems use heating and cooling methods to store energy for on-demand use. Of the different thermal storage options on the market, two include molten salt and active solar heating systems.
Molten Salt as a Viable Thermal Storage Option
Molten salt uses concentrated solar power (CSP) to heat salt. The molten salt is then stored for use at a later date to provide mass electricity through a steam turbine. Large-scale energy storage projects are the best fit for molten salt projects.
How Active Solar Heating Systems Work
Solar heating systems heat a liquid or air. The heated element is then used to heat an object, such as a home, or stored for later.
Mechanical Storage Systems
Mechanical systems use machines to provide kinetic energy for on-demand electricity needs. Two types of mechanical energy storage commonly used include flywheels and pumped hydropower.
Mechanical Storage and Flywheels
Flywheels store energy in a spinning rotor. After being given an initial start, flywheels hold on to that kinetic energy, which then powers other objects until the flywheel stops spinning. They can provide up to 15 minutes of immediate electricity until other backup options come online.
Pumped Hydropower: a Mechanical Storage Option
Pumped hydropower is a reservoir of water let through a turbine to provide on-demand power. This storage type is one of the most common energy storage options for large-scale energy storage.
Several different battery storage options are also on the market. Some of these include lithium-ion, flow, lead-acid, sodium, and salt-water batteries.
Lithium-ion batteries are known for the amount of power they can pack in a small space. Lithium-ion home batteries are common in residential energy storage. These batteries, however, are also used in large-scale energy projects.
Flow Batteries and Battery Storage
A flow battery stores energy in two chemicals stored in their liquid state inside tanks. Flow batteries provide long-lasting power.
Sodium Battery Storage
Sodium batteries use salt in a solid state to produce an electrical current. While these batteries still have some problems holding them back from regular use, scientists are working on improving this battery option.
Salt-water batteries are another battery under development. These batteries use salt water, air, and magnesium to produce an electric current.
Why Residential Solar Requires Energy Storage
There are a couple of reasons why solar requires an energy storage option. The first reason is the unpredictability of solar power without it. Because of how solar panels work, the amount of energy the solar panels can produce depends on the weather.
Meteorologists can predict the weather, but they can’t control it. The possibility of clear sunny skies every day of the year is low, and if this did happen, it would cause problems. Solar arrays need to work in conjunction with some form of solar backup option, whether it be net metering or an energy storage device.
The second reason is solar can’t provide power during an outage without storage. Grid-tied solar, which is the most common, requires systems to have automatic disconnect switches so the array can turn off during an outage.
Finding a solar storage option optimal for residential solar is not required. However, if the customer wants to decrease their reliance on the grid, professionals recommend investing in an energy storage option designed for residential solar. This energy storage could be anything from net metering to battery backup.
The Best Storage Type for Residential Solar
While each storage type has its place, they aren’t all a good fit for residential solar. Residential solar requires a storage system that doesn’t take up much space or is overly expensive.
One competitor for residential solar storage is thermal storage. If solar panels aren’t taking up all the available space on the roof, heating systems can help decrease the cost of heating a pool. However, thermal storage isn’t an ideal option for powering a home, especially for areas with colder climates.
Battery storage has become the go-to option for residential solar for a couple of reasons. One reason is the comparative size of battery storage to other energy storage options. Another is the cost decline that battery storage has experienced over the past several years.
The Best Batteries for Residential Solar Power
The best battery backup options meet the energy needs of the customer without taking up too much space. They also have short charge times and long discharges.
Lithium-ion batteries are the battery backup option of choice for residential solar because they meet most of these expectations. However, lead-acid batteries are also lauded as a close second for residential solar storage.
Reviewing both of these options and why they’re viable helps homeowners determine which battery backup option is a good fit for them.
Pros and Cons of Lead-Acid Battery Backup
Lead-acid batteries have several things going for them. These batteries don’t require maintenance, they can withstand different charging rates, they can function after long-term inactivity, they have a long life cycle, and these batteries can withstand varying weather conditions.
While worth considering, these batteries do have a few drawbacks; they’re heavy, they have longer charge times, and deep cycling can decrease their lifespan.
Lithium-Ion Battery Backup
While lead-acid batteries are cheaper, lithium-ion batteries have benefits that outweigh the costs. These benefits include their weight-to-power ratio, their high-energy density, self-discharging at a lower rate, and there is no need to prime the batteries before the first use.
Go Solar Group offers several battery backup options for its customers. Most of these options are lithium-ion batteries. However, there is a lead-acid battery extension option, the Goal Zero Tank, for Go Solar Group’s level two battery backup.