The energy management system (EMS) controls the flow of energy between the solar panels, the battery and fixture. In a Carmanah EverGEN system, the EMS is made up of three components:
- EMS charger
- LED driver
- EMS controller
EMS Charger
The EMS charger is designed to transfer as much power as possible from the solar panel to the batteries. Using Maximum Power Point Tracking (MPPT) and Temperature-Compensated Maximum Power Point Tracking (in the EverGEN 1700), the charger monitors and optimizes power transfer to ensure the system is collecting as much available energy as possible.
The charger also supplies battery power to the rest of the system and protects from accidental reverse polarity connections between the solar panel and batteries.
Maximum Power Point Tracking (MPPT)
Solar panels have different voltage and current outputs depending on the load attached to them. The amount of power transferred between the panel and the battery in a solar LED lighting system is dependent on the load: certain load values will allow more power to be transferred than others. MPPT monitors the load value to ensure that the maximum amount of power is always being transferred from the panel to the battery. It does this by increasing and decreasing the load every so often to determine if there is an opportunity to increase the amount of power being transferred.
Let’s look at a simplified scenario: A 100W PV panel is providing 20V @ 5A output. A simple connection between panel and battery would supply about 13V @ 5A to the battery. This is equivalent to 65W, which equates to 65% efficiency from the circuit. Transferring power between the panel and battery in this way would require a much larger system than necessary to power the application throughout the year in all conditions than if MPPT were used.
With an MPPT circuit, the 100W PV panel will still be delivering 20V @ 5A but the system will be charging the battery at 13V @ 7.3A. This means that nearly all the power is being transferred to the battery.
MPPT is especially helpful during cloudy or cool days when collecting and storing as much available energy as possible is important.
For more on temperature-compensated MPPT, click here.
LED Driver
The main function of the LED driver is to provide a constant current output to the LEDs. The output current is set by the EMS controller depending on the operating profile desired. The LED driver takes the nominal 12V battery charge supplied by the EMS charger and converts this to the voltage and current necessary to drive the fixture LEDs. The driver also has output protection to prevent problems associate with accidental shorting.
EMS Controller
The EMS controller is the intelligence in the EverGEN solar LED lighting system. The controller gathers information from all other components of the system and makes decisions about how to control the energy flow.
The controller monitors the energy income of the system and watches battery state of charge, voltage and temperature to ensure the battery is being charged and discharged properly.
It also controls the energy output to the LEDs and determines how the LEDs should be operated based on the operating profile. The controller is responsible for dimming the lights to the required light level (or turning them off) at the times determined by the operating profile.
EverGEN 1700 Series Energy Management System
The EverGEN 1700 Series contains a specially designed energy management system. In addition to the three main components of charger, driver, and controller mentioned above, the energy management systems inside the EverGEN 1700 series lights also include:
EMS Radio
The EverGEN 1700 solar LED lighting series has a fourth EMS component, the EMS Radio, which allows systems to wirelessly communicate with each other via a 2.4 GHz mesh network based on the IEEE 802.15.4 radio protocol. The EMS radio enables advanced occupancy sensing, coordinated day/night transition, and system health monitoring.
Temperature-Compensated MPPT Charger
The EverGEN 1700 features a temperature-compensated MPPT charger and temperature sensors on battery terminals that enable accurate compensation.
In hot temperature extremes, temperature-compensated charging helps to prevent thermal runaway of the batteries by making adjustments based on the battery temperature to prevent unsafe charging. In cold temperature extremes, temperature-compensated charging ensures batteries are not undercharged by improving charge acceptance.
Temperature compensation protects battery health and system longevity and can be particularly helpful in areas that experience very high or very low temperatures.
Coordinated Light Transition
The EverGEN 1700 is able to activate all the lights in a network at the same time. The EMS in the 1700 series monitors the solar panel, rather than a photo cell, to determine day and night transitions. Using the radio to communicate with all the lights in the network, the EMS indicates when it is time to transition from off-to-on at dusk and from on-to-off at dawn. By using the solar panel instead of a photo cell, the EMS is immune to artificial light falsely triggering a transition of the lights.