SEC Controller MPPT Connection
In the European part of Russia, the sun finally began to shine brightly enough for a long time to be able to maintain autonomous system without turning to external power, such as electrical networks or generators. But there are several tricks that let you collect a little more energy with small modifications of the already existing system. The first is tracking the sun, the second is tracking the maximum power point for solar batteries. Let's start with the first and most interesting - a solar tracker.
The idea is not mine, but it shows the operating principle very clearly.
The tracker shown above can even be purchased on Ebay. It costs about 52,000 rubles by the end of April 2015 in Russia and it is able to hold only a couple of solar panels with a total capacity of up to 600 watts. Since the pay-back of solar energy is a very painful issue adding to the total estimate such a solar energy tracker will make the whole thing pay off for quite a long time. Therefore, DIY trackers with various controllers are extremely popular.
Here I should note that one should assess the usefulness of installing a solar tracker. Such a device lets the energy production increase 1,6 times using the same number of solar panels due to longer sun exposure on the panel and the optimal angle of installation of the solar system against the sun.
It is worth highlighting the main tasks that we have to solve when tracking the sun:
1. Creating a rather robust platform that will not only withstand the weight of the panels themselves, but also the gusts of wind. A tracker with 4-6 or more panels can be considered as a large sail.
2. Calculating the mechanics of turning a heavy platform with high wind resistance.
3. Setting up a control system for sun tracking.Let's start with the first issue. It is good to place the batteries in such a way that they do not shade each other and are attached as per required voltage.
For such a tracker you need a strong foundation and solid materials. Actuators suit the best out of all the tested devices for controlling the rotary platform. This tracker allows you to control the position of solar panels in two planes. However, you can set up only horizontal control and change the vertical angle a couple of times a year (in spring and in autumn).
As for the logic of the whole system there are several ways to choose from:
1. Tracking the brightest point
2. Turn and tilt according to the timer (sunrise and sunset are known and constant for each day)
3. Hybrid variant combining a constant angle of rotation and search for maximum brightness
In my previous article I talked about a hybrid inverter that can use energy with priority given to solar panels and only take the missing energy from the electricity network. How does this relate to the solar energy controller? The fact is that the Russian company MicroART has recently launched its own MPPT-controllers which can be connected with inverters of the same manufacturer on the common bus. Well, since I have already installed a hybrid inverter I decided to test a new controller in a new season.
I must say that it looks brutal compared to the two previous controllers which I already have in my household. There is a metal case, radiators on the sides (Chinese models have radiators on the rear wall), dark gray steel case.
The biggest advantage of this controller for me is its ability to pump the right amount of energy so that there is no need to borrow the energy from the battery, which reduces its resource. I've chosen the most popular and optimal voltage / current ratio controller ECO Energiya MPPT Pro 200/100 out of the three models that are presented by the manufacturer. The characteristics of the device say that the controller supports input voltage of up to 200V and output current of up to 100A. Taking into account the fact that my battery assembly is 24 V (battery voltage 12/24/48/96 V is supported), the controller will give a maximum power of 2400W which means that I have a twofold margin for increasing the number of solar panels. The maximum power of the controller is 11kW with 110V on the batteries (buffer voltage). The controller supports communication with the hybrid inverter MAC SIN Energiya Pro HYBRID v.1 24V via the I2C bus and can immediately add power when the inverter provides information about the increase in power consumption. The interaction of two devices produced by one company is usually a well-functioning system so it all comes down to plugging one wire in the necessary connectors of devices and activating the necessary parameters. I was also interested in the statement made by the manufacturer of this controller that this MPPT controller can also add power immediatelly when using an inverter from any other manufacturer. I wondered how that was implemented. Everything was as simple as that:
The current sensor is attached to the positive wire leading to the inverter (that is why the inverter manufacturer is not important) and using the Hall effect the controller calculates the power consumption. At this very moment, the solar energy controller itself comes into operation and it pumps up the required amount of energy. All the controllers I know increase the charging rate taking into account only the battery voltage.
Investigate the capabilities of the controller I came across the fact that it is equipped with three relays and their triggering can be programmed. For example, if there is enough sunny weather and there is no electricity consumption by the house, you can start heating an additional boiler or a pool. And vice versa: there is no sun, the voltage of the batteries has dropped to a critical level, the inverter can simply switch off and the energy consumption will continue. Then you can start a separate gasoline / diesel generator just closing the relay. However, to do this the generator must have a dry start contact or a separate automatic start system or ATS - Automatic Transfer Switch. Since I have a simple Chinese generator like most of the summer visitors but with a starter, I looked towards the automation of its launch and was delighted to learn that MicroART had been releasing its automatic equipment for a long time.
Let's return to the controller. Its installation process is standard: first connect the battery terminals, then connect the terminals of solar panels and set the parameters. If you install an external current sensor you can observe how much power the inverter consumes in real-time mode. So, we unreel the wires, mount the controller and start saving. The solar energy controller is purposely connected via an external current sensor to demonstrate the possibility of operation with any other inverter manufactured by a third party.
The solar energy controller corresponds to the declared characteristics and really pumps up the energy even when connected to the "foreign" inverter via a current sensor. The hybrid inverter actually pumps the energy from the solar panels (in the photo half of the 200 watts consumed, namely 100 watts, comes from the sun.) The controller will always take the minimum of 100 watts from the electricity network and the rest it will take from the sun, it is the device's feature. Simply put, the kit began to pay itself from the moment of connection. Unfortunately, the spring has suddenly changed to a blizzard and in the near future it is unlikely that we see the high efficiency of the kit (hybrid inverter + solar controller) but starting from May I expect almost full coverage of my energy needs with the help of the sun.