In Part 1 of our Behind-the-Meter (BTM) Series, we laid out some key concepts, focusing on these energy systems & why they’re important. Join us for Part 2 of our series as we discuss the evolution of these systems, looking closer at BTM energy storage systems – old and new!
Contact: Betsy Barry
Communication Manager
706.206.7271
betsy.barry@acculonenergy.com
The increasing adoption of behind-the-meter (BTM) energy storage has been fueled by a confluence of factors, including the need to address the challenges of increased energy demand, an increase in energy costs, the growing integration of renewable energy sources, as well as a heightened focus on grid resilience and overall sustainable solutions.
Historically, BTM energy storage was primarily adopted by commercial and industrial (C&I) customers with critical operational needs that necessitate energy resilience during power outages, such as hospitals, airports, and telecommunications infrastructure. These legacy stationary applications mainly provided simple backup power to critical services. However, the landscape of BTM energy storage is evolving, with a growing number of diverse C&I customers adopting or considering these systems.
First, let’s look at the incumbents and discuss the pros/cons of each:
Generators and Fuel Cells
are predominantly run off either diesel, petroleum, natural gas, or hydrogen. Diesel and petroleum generators are the most prevalent based on being the cheapest, followed by natural gas generators, whereby fuel cells are the most expensive and tend to be deployed in relatively niche applications.
✅Advantages:
- Longer Run Times: Generators can provide extended power backup as long as fuel is available.
- High Power Output: They can handle large power loads, which is suitable for whole-building backup.
- Established Technology: Generators are a well-established and understood technology.
❌ Disadvantages:
- Environmental Impact: Fossil fuel combustion produces emissions, contributing to air pollution and greenhouse gases.
- Noise: Generators can be noisy, causing disturbances.
- Fuel Dependence: Reliance on fuel supply, which can be disrupted during emergencies.
- Maintenance: Regular maintenance is required, including oil changes and filter replacements.
- Operating Costs: Fuel costs can fluctuate and be significant.
- Slow Response Time: Not great for applications that require quick response.
While traditional solutions like generators & lead-acid batteries remain viable in certain contexts, emerging technologies such as sodium-ion are gaining traction due to their improved efficiency, safety, & scalability.
Lead-acid Batteries
are an older technology and less efficient, however, they are still used in some applications. They can deliver excellent pulsed power. However, they have a relatively limited cycle life and raise safety concerns because they release hydrogen and oxygen during charging via water electrolysis, so their installation outside of buildings is necessary.
✅ Advantages
- They can deliver excellent pulsed power, making them a potential technology for BTM applications.
❌ Drawbacks:
- They release hydrogen and oxygen during charging via water electrolysis, raising safety concerns and necessitating their installation outside of buildings.
- They have poor low-temperature performance, making them a less desirable option for cold climates.
- The sulfuric acid and lead used to form the electrolyte and the anode respectively are toxic and have a relatively limited cycle life.
- Periodic water maintenance, sulfation of the plates, low specific energy, and limited depth of discharge have been significant barriers to their introduction for BTM systems.
New Kid on the Block: Lithium Ion Batteries
are gaining popularity due to their high energy density and long cycle life. These include predominantly NMC and LFP variants of lithium-ion batteries.
✅ Advantages:
- They are the most commonly used battery technology for BTM applications.
- They outperform lead-acid batteries in terms of energy density, depth of discharge, and round-trip efficiency.
- They can operate in the range of -30 to 60 degrees Celsius.
❌ Drawbacks:
- They require more capital investment relative to lead-acid batteries.
- For NMC variants, the requirement for cobalt in the cathode puts a strain on limited cobalt sources.
- They are vulnerable to high temperatures and can catch fire easily, requiring a battery management system to prevent overcurrent, overheating, and overvoltage.
Emerging Technologies: Sodium-Ion Batteries
✅ Advantages:
- High Power Capability
- Comparable cycle life with LFP
- Ability to operate in a wider range of temperatures
- Safe to go to 0V state of charge
❌ Drawbacks:
- Relatively few deployments to date
- Reduced energy density vs. lithium-ion (67%-80% on average)
Flow Batteries
✅ Advantages:
- VRFBs have a fast response time, high efficiency, and long cycle life that can provide high storage capacity, making them ideal for industrial BTM ESSs.
- They may also be charged and discharged simultaneously and be used to minimize voltage and frequency fluctuations and provide load-leveling services.
- VRFBs are ideal for grid-scale applications such as voltage and frequency regulation services, distribution power quality, load shifting, and power output smoothing for large-scale renewable energy systems.
❌ Drawbacks:
- They have a complicated structure.
- They need an external power supply to power the pumps.
- The fluids are expensive, toxic, and corrosive, restricting their widespread adoption of BTM technology.
As BTM energy storage continues to grow and evolve, the diversity of available technologies offers both opportunities and challenges for C&I customers. While traditional solutions like generators and lead-acid batteries remain viable in certain contexts, emerging technologies such as sodium-ion are gaining traction due to their improved efficiency, safety, and scalability. Each technology comes with trade-offs in terms of cost, performance, and environmental impact, making it necessary for customers to carefully assess their specific energy needs.
The next piece in the series will examine specific BTM storage applications and see how these technologies compare against one another. Tune in next week!