How Battery Energy Storage Works
What is battery energy storage?
Battery storage systems are rechargeable battery systems that store energy from solar arrays or the grid and provide that energy to a home or business. Because they contain advanced technology not found in ordinary batteries, they can easily perform certain tasks that were difficult or impossible in the past, such as peaking and load shifting.
Step 1: Charging
During the day, the battery storage system is recharged with clean electricity generated by the sun.
Step 2: Optimise
Smart battery software uses algorithms to reconcile solar power generation, usage history, utility rate structures, and weather patterns to optimise the amount of time the stored energy is used.
Step 3: Discharge
During periods of high usage, energy is released from the battery storage system, reducing or eliminating costly demand charges.
The idea of combining solar arrays and batteries is not new. Early solar pioneers often connected a series of ocean deep cycle batteries to their solar arrays. Until net metering became commonplace, this was the only way to use stored solar energy at night. Modern battery storage systems are similar in concept, but more complex and powerful. If those old battery arrays were like flip phones, then modern battery storage systems are like the latest smartphones - they have the same main features, but everything else is worlds apart.
Modern battery storage systems typically include inbuilt inverters and computer control systems. This means they are all-in-one, turnkey systems that are easy to install, essentially maintenance-free, and require no effort or expertise on the part of the owner. They're also weatherproof and safe for both people and pets.
Applications - what energy storage can do
Battery energy storage systems have a wide range of applications. Commercial applications include peaking, load shifting, emergency backup and various grid services. Residential applications include self-consumption, off-grid homes and emergency backup.
Peaking - The most important application of energy storage in a commercial setting is peaking. For businesses with on-demand utility rates, 30 to 70 percent of the utility bill may consist of on-demand charges. For these businesses, a separate solar array is not always a sufficient solution. However, a battery storage system can ensure that no more than a predetermined threshold of power is drawn from the grid during peak hours. We'll discuss in more detail how solar + storage can eliminate demand charges and reduce commercial utility bills to near zero in our next post.
Load Shifting - Battery storage systems allow businesses to change the way they use energy by going solar or charging their batteries when electricity is cheapest and discharging them when electricity is more expensive. This is especially useful for businesses in rural electric cooperatives (RECs) or other utilities that do not offer net metering on an annual basis.
Emergency Backup - Like an uninterruptible power supply (UPS) under a desk or in a server room, a battery storage system can stay on during a power outage.
Microgrids - Energy storage opens up the possibility of building microgrids in conjunction with renewable energy sources. The scalability and turnkey simplicity of battery storage makes these systems economically viable. Island microgrids can be used for certain large commercial facilities or even entire communities. The switch from diesel generation to solar + storage at Ta'u on the island of American Samoa is a good example of this application.
Renewable Energy Integration - Energy storage can smooth the output of renewable energy. Solar power is cyclical - day vs. night, summer vs. winter. Energy storage enables solar production to mimic the consistency of fossil fuel energy.
Grid Services - For utility-scale customers, battery storage can provide many valuable applications, including reserve capacity, frequency regulation, and grid voltage control.
Solar Self-Consumption - For homeowners, solar self-consumption is the most important application for energy storage systems. Energy storage allows homeowners to store surplus energy generated by solar panels during the day and use it at night. This can be a good option for some utility customers who do not offer net metering.
Off-grid - Solar-powered off-grid homes require batteries. Modern battery storage systems far exceed the capabilities of the marine lead-acid batteries used by the solar DIY pioneers of decades past. Modern systems are easier to install, easier to configure, more scalable, cheaper per kWh of storage, and safer.
Emergency Backup - Battery storage gives you peace of mind by keeping the power on during a blackout. Energy storage works with or without solar power and is a safe, seamless alternative to small generators, which are one of the leading causes of carbon monoxide poisoning in the United States.
Technology - What's Inside
Each energy storage unit contains multiple components: one or more battery modules, on-board sensors, control components and an inverter. In DC-coupled units, a separate inverter is used. In AC-coupled units, the inverter is integrated into the system. These components make the energy storage system more than just a battery.
If one battery module fails, multiple replaceable battery modules prevent the entire energy storage unit from failing. The module can be exchanged for another without downtime.
Sensors ensure safe operation and allow remote monitoring. On-board sensors help maintain proper operating temperatures, monitor battery module failures and report usage data to you and your energy company.
The control component means that the energy storage system can be set up as needed to perform its intended job without any ongoing user intervention. For example, batteries can be configured to automatically charge when energy is cheapest and discharge when energy is most expensive, or they can be configured to simply store energy in the event of a power failure.
Integrated inverters make installation easy and inexpensive. While DC-coupled battery storage systems with standalone inverters are cheap, efficient and suitable for off-grid homes, they are much less flexible than AC-coupled units with integrated inverters. AC-coupled units, such as Tesla's Powerwall 2, are more versatile, work without a solar array, and are easier to install. Modern systems simply plug into the existing electrical network.
Best-in-class energy storage systems, such as the ones we offer, also have a number of key components: built-in cooling, weatherproof construction and scalable architecture.
Built-in cooling ensures optimal performance. Weatherproof construction means that the energy storage system can be installed outdoors without the added cost of a protective structure. Scalable architecture means that several storage units can be connected to form a larger system. Additional units can be added at any time in the future.
All in all, these components make battery energy storage systems safe, scalable and cost-effective.
Opportunities - changing our energy future
We believe battery storage systems will fundamentally change the way we interact with energy. They will make solar energy a no-brainer for more homes and businesses, bring greater independence from traditional utilities, and open the door to diverse energy options.
In the rest of this series, we'll explore these opportunities in more depth. Next up is a discussion of corporate peaking and reducing demand charges. Learn how we cut our customers' utility bills from around $9,000 per month to $20 per month with our peaking strategy.
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