I Want to Add a New Large Load to my Off-Grid System, How do I Proceed?

I’m wanting to add an electric fridge to my system, what steps should I take?

• Adding a new fridge
• Assess the New Load
• Evaluate Existing System Capacity
• Determine Additional Requirements
• ImplementationMonitoring and Testing

Adding a new fridge

I often have customers who include a fridge in their load list when designing their off-grid systems. However, I also encounter customers with existing systems who want to add a new appliance. Recently, someone inquired about adding a fridge to their system, which had been installed a couple of years ago and was working perfectly with the original loads.

Adding a fridge, depending on several criteria, isn’t as straightforward as adding a simple load like a light or a laptop charger. A fridge can consume a significant amount of energy and does so frequently throughout the day, especially every time it’s opened and closed.

Since the system is fairly new, assessing it is much easier. If it were an older system, we might have to consider replacing the inverter, adding new panels, or even upgrading the entire system. Given that our original design included a 3000-watt inverter charger on a 24-volt system, we know that the installed inverter can easily handle a fridge. However, we need to consider the capacity of the battery bank and the amount of daily solar power generated to ensure the batteries are adequately charged each day.

Assess the New Load

• Determine the Power Requirement: Identify the power consumption of the new load in watts (W) and its operating voltage. Also, understand its usage pattern (e.g., continuous or intermittent use). In our case it is a fridge so we would ask the customer the wattage of the fridge which would be located either on the appliance itself or if recently purchased possibly in the owners manual as well.
• Calculate Daily Energy Usage: Multiply the power consumption by the number of hours the load will be used daily to get the total daily energy consumption in watt-hours (Wh).
• Since our customers system is already installed we can test it by just plugging the fridge in and see how the system reacts.

Evaluate Existing System Capacity

• Battery Capacity: Check your current battery capacity in amp-hours (Ah) and ensure it’s sufficient to handle the additional load. Remember to consider only 50% of the total capacity for lead-acid batteries to avoid deep discharge. If you have a lead carbon battery you can use up to possibly 70% or more depending on the brand and if you have a lithium based battery you can almost use up the entire capacity or base it on 90% to avoid total discharge.
• In this case, our customer’s battery bank is sufficient for the existing loads. However, because a fridge uses a substantial amount of energy, especially when the compressor first starts, we need to carefully evaluate the additional demands it will place on the system. After testing, our customer’s fridge was causing the system to shut down halfway through the day, indicating that the battery capacity was not adequate.
• Solar Panel Output: Ensure your solar panels can generate enough power to replenish the additional energy consumed by the new load. Consider the average sun hours per day in your location. When I went to take a look at the system, it was sitting on float or fully charged. The customer wasn’t at their cabin so the inverter was off and there is no way to know how much use is being taken out of it but we can safely say that the sun at least for the moment keeps the system fully charged

Determine Additional Requirements

• Batteries: If your current battery bank is insufficient, calculate how many more batteries you’ll need to meet the increased demand. Since our customer had already tried using the fridge, and they observed that the system’s capacity fell short halfway through the day. Without turning on the generator, the batteries couldn’t keep up with the fridge’s energy demands. For this particular situation, since the batteries are relatively new, we will add a second set in parallel to double the capacity.
• Solar Panels: If necessary, calculate the additional solar panel capacity required to support the new load, ensuring you can fully charge the batteries even on cloudy days. Since we don’t yet know if the panels and sunlight can keep everything charged, we won’t add any new panels at this time to avoid unnecessary costs. Let’s first test the system with the upgraded second set of batteries and see how it performs.

Implementation

• Consult a Professional: It’s advisable to consult with a solar power professional to ensure all components are compatible and properly sized. We can help you with this, the design and the sale of any new equipment.
• Purchase and Install: Acquire the necessary components and proceed with installation. Follow safety guidelines and manufacturer’s instructions. Again if you need help with this please don’t hesitate to  contact us. 

Monitoring and Testing

• System Monitoring: After installation, monitor the system’s performance to ensure it meets your energy needs without overloading any components. In our case the customer will just test the batteries to see how the fridge handles the new capacity. They can then after a few days of use including a few cloudy days, can give us some feedback on how things are going with the upgrade.

Conclusion

We will proceed by adding a second set of batteries in parallel to double the capacity. Our next step involves verifying that the solar panels can adequately charge the expanded battery bank. Once confirmed, we will assess the system’s performance and make any necessary adjustments accordingly. After a few days of use, including some cloudy days, the customer can provide feedback on system performance. Specifically, they can report the state of charge (SOC) on an average day, whether the batteries reach float or full charge after the upgrade. It’s crucial to ensure that the panels effectively charge the new battery bank before making further assessments and decisions.

For individuals seeking consultation, education, or assistance in system designs related to off-grid solar applications, IOTG Solar stands ready to help. Our team is available to address questions, provide valuable insights, and offer support at every stage of the solar energy journey. Feel free to reach out to  IOTG Solar  anytime for expert assistance and comprehensive solutions tailored to your specific needs.

IOTG Solar…

Keeping you powered through education.