How do you size a storage project?

In case you missed it, click here to read the third installment of our Energy Storage series discussing bespoke vs. pre-packaged energy storage systems.

Many factors go into appropriately sizing a battery system for a given application. This article will explore several of the important considerations in sizing battery systems.

Sizing an energy storage system involves determining the energy storage capacity in kilowatt-hours and the system’s power rating (maximum power output or input in kilowatts) to meet the specific needs of the commercial facility.

You can better understand a battery system’s capability by knowing the useful output power of the system and the duration this output can be maintained. A battery’s useful depth of discharge and discharge efficiency directly affect the usefulness of its output.

You must also consider the power conversion system size and inefficiencies. If the system is too small, it may decrease the battery system’s max power; if it is oversized, the excess power cannot be realized.

When sizing battery systems, you should also consider battery degradation, which occurs throughout a battery’s life. Degradation is steeper in the first few years of operation, so you may need to augment your battery system periodically throughout its lifespan to maintain useful power output levels. You should consider space and infrastructure requirements for augmentation when sizing a battery system.

The operational characteristics of a battery system will affect its degradation. For example, a smaller depth of discharge cycles, slower charge/discharge rates, and a lower resting state of charges will decrease degradation. Understanding how a battery system will be operated will help you determine the initial sizing of the system. Oversizing a battery system by an appropriate amount can minimize degradation, extend its useful life, and ease warranty concerns.

The considerations discussed in this article apply to battery systems whether they operate behind the meter to manage demand, in front of the meter providing ancillary services, or with a solar system to capture energy that would be otherwise clipped.

Some additional steps to consider when sizing an energy storage system:

1. Identify objectives:

Begin by identifying the primary objectives of your energy storage system. Do you hope to reduce energy costs, provide backup power, integrate renewable energy, enhance grid stability or some combination? Clearly defining your goals will help guide the sizing process.

2. Load analysis:

Conduct a detailed analysis of the facility’s electricity load profile. Examine historical electricity usage data to understand the patterns of energy consumption, peak demand periods, and load fluctuations. Identify critical loads that require continuous power supply and determine their power and energy requirements.

3. Peak demand management:

If one of the goals is to manage peak demand and reduce demand charges, analyze the facility’s electricity demand during peak periods. Assess the potential for load shifting or peak shaving, where excess energy is stored during low-demand periods and discharged during peak periods to reduce the overall demand from the grid.

4. Renewable integration:

If the goal is to integrate renewable energy sources, analyze the facility’s renewable generation capacity and its intermittency. Assess the excess energy generated during high production periods and determine the required energy storage capacity to store and utilize the surplus energy during low production periods.

5. Backup power requirements:

If the primary purpose is to provide backup power during outages, identify the critical loads it must support. Calculate the power and energy requirements of these loads to determine the appropriate capacity and power rating of the energy storage system.

6. System sizing calculation:

Use the gathered information to perform a system sizing calculation. This calculation involves considering factors such as the desired duration of backup power, the rate of energy discharge, and the system’s efficiency. It may also involve considering the desired depth of discharge, which determines the portion of energy storage capacity you can utilize to prolong the lifespan of the system.

7. Consider safety margins and future expansion:

It’s important to include safety margins when sizing an energy storage system to account for uncertainties, variations in load, and unexpected contingencies. Additionally, consider any future expansion plans or changes in energy demand that may influence the required system capacity.

To determine the best size for an energy storage system for your commercial facility, analyze the facility’s energy needs and goals. Consider factors like load profiles, renewable integration, backup power needs, and system efficiency.

In our next post in the series, we’ll be talking about the differences between grid-connected systems and microgrids. In the meantime, feel free to REACH OUT to Edison Energy as your storage experts and learn more about how we can help you tackle your energy storage needs.