The Energy Management System: Controlling Power in a Solar Light
Posted by Stephen Shickadance in How Solar Lights Work.
The Energy Management System (EMS) is an efficiency system that ensures energy is stored in the battery properly and then is delivered to the fixture when the fixture needs it.
Some EMS systems have monitoring systems that check each light for functionality via satellite. These generally aren’t recommended because they reduce the ROI on solar lighting systems and add unnecessary monthly bills just to ensure a light is working.
The EMS consists of two components: the driver and the controller. These can either be separate components or a combined build.
Without either of these, your light won’t function properly and it could cause irreparable damage to the fixture, battery, or other components.
In more expensive energy management systems, these two components are combined into one for price and efficiency reasons. Generally you’ll find combined controllers and drivers to be of better quality.
What Does a Solar LED Driver Do?
Drivers are energy control modules for fixtures. What that means is they are able to conduct the flow of electricity to the fixture in order to raise the lights to certain brightnesses and protect the LEDs from high voltages. A fixture doesn’t just have one brightness setting--they can be dimmed at certain times during the day to give the proper level of illumination for a subject. Without a driver, the LEDs would stay on at full brightness all of the time and burn too much of the stored solar energy as well as reduce the longevity of the LEDs in the fixture.
What Makes a Quality Solar LED Driver?
It’s important to understand that the driver of a solar LED light is one of the most replaced components for a system. Drivers are under constant electrical load and if you don’t have a quality driver, you’ll need to replace it more often. The culprit behind driver failure is usually the electrolytic capacitor that uses a gel to conduct electricity. This gel evaporates over time with high heat. Check with your manufacturer to ensure the drivers used in their products are well-trusted, or else the expenditure of constantly replacing the driver will reduce the ROI of the system.
You’ll want a solar LED driver that provides constant voltage for parallel circuitry. Cheaper drivers may often give “spikes” in current which can cause LEDs to malfunction or fail. Higher-quality drivers dim the light fixtures by “blinking” current at several thousands of hertz (or cycles per second) and altering the blinking hertz instead of reducing the current.
As before, drivers are the most commonly replaced component so you’ll want external drivers on your solar lights so you can easily access them if and when the time comes. Ensure the external driver has an IP Rating to keep out dirt and water
Solar LED drivers are a component of the Energy Management System which is covered in another section.
How Controllers Work in an Energy Management System
Solar street light charge controllers regulate power between the panels and the batteries--they prevent the batteries from overcharging and stop reverse-current flow, or when electricity flows back from the batteries to the panels at night.
There are two main types of controllers on the market known as Pulse Width Modulation (PWM) and Maximum Power Point Tracking. It’s important to know the distinction between these types of controllers.
PWM controllers use heavily-tested technology and are less expensive than their counterparts. They’re sized up to 60 Amps and are very durable with passive heat sink cooling. However, the voltage on a PWM controller must match the voltage on the battery in order to regulate properly, and they have limited capacity for system growth.
PWM controllers lower the level of charge directed towards the battery as the battery approaches a fully-charged state. They’re great for protecting the lifespan of the battery since they tend to keep the battery at maximum charge without overcharging.
MPPT controllers are ideal for solar lighting systems because they reduce charge time for batteries, reduce power loss in cabling, and offer more power than PWM controllers (80 Amps). MPPT controllers convert excess voltage (12v for batteries) into amps, thus delivering the maximum voltage to the battery. This is important for a system because if a battery isn’t fully charged over a day cycle, the charge level could go beyond the recommended depth of discharge and sacrifice battery life over time.
MPPT controllers, although more expensive, are newer and better for solar lighting systems. Ensure your manufacturer uses these for quicker battery recharge and less power loss.
The energy management system is an incredibly important component of a solar LED light. They’re the most susceptible to failure because they’re under constant power load, so choosing an EMS with a proper controller and driver will last longer and ensure the return on investment of your solar project will be as high as possible.
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