Complete energy autonomy or how to survive with solar panels in the outback (part 5. Sun Catcher)

In the European part of Russia, the sun finally began to shine bright enough and long enough to be able to maintain its autonomous system without attracting external energy — electricity grids and generators. But there are several tricks that allow with a small modification of an existing system to collect a little more energy. The first is tracking the sun, the second is tracking the maximum power point of the solar batteries. Let's start with the first and most interesting - the solar tracker.

“Moped is not mine”, but for understanding the principle of action is very clear.


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The tracker mentioned above can even be purchased on Ebay . It costs about 52,000 rubles at the end of April 2015 in Russia, and is capable of holding just a couple of panels, with a total capacity of up to 600 watts. And since with the payback of solar energy the question is very difficult, then with the addition of such a tracker to the estimate, solar energy will pay off for quite some time. Therefore, the popularity of self-made trackers with different controls is extremely high.

You should make a remark and evaluate the feasibility of installing a solar tracker. This device allows you to increase energy production with the same number of solar panels by 1.6 times due to the longer exposure of the sun to the panel and the optimal angle of the joint venture installation relative to the sun.

It is necessary to highlight the main tasks that will have to be solved while tracking the sun:
1. Create a sufficiently strong platform that will not only withstand the weight of the panels themselves, but also gusts of wind. A tracker with 4-6 or more panels can be considered a big sail.
2. Create the mechanics of turning a heavy platform with high windage.
3. Create a logic control mechanics, for tracking the sun.

Let's start with the first item. It is advisable to place arrays of batteries in such a way that they do not obscure each other and are attached multiple times to the required voltage.


For such a tracker requires a strong foundation and strong iron. Of all the devices tested, actuators are best suited for controlling the turntable. The control mechanic is clearly visible in the next photo.


This tracker allows you to control the position of the solar panels in two planes. However, you can make control only horizontally, and vertically change the angle a couple of times a year (spring and autumn).

As for the logic of the entire system, you can go several ways:
1. Tracking the brightest point
2. Turn and tilt on a timer (sunrise and sunset are known and constant for each day)
3. Hybrid version, combining a constant angle of rotation and the search for maximum brightness

The first method can be implemented independently or buy a ready device from the Chinese. The first to control the tracker in the same plane


The second to control the tracker in two planes


Roughly speaking, the Chinese want $ 100 to track the maximum brightness at one point. It is clear that these systems do not pose a great deal of difficulty for a person who understands the principles of operation of controllers, so a similar system can be assembled 10 times cheaper.
It will look like this

Well, the details of the project and implementation can be found here . The project is not mine, so I will not plagiarize.
More details about the independent production of the solar tracker can be read on the profile forum , where they empirically computed the optimal designs and the best equipment for this task.

Track the maximum power point of the solar cell (MPPT)
In the second part of my cycle, I talked about two different types of solar controllers. MPPT (Maximum Power Point Tracking) controller also monitors the sun, but from a different position of the entire system. For a simple explanation I will give a graph and a clarification after.


The graph shows that the maximum output power can be obtained when at the point of maximum power, which will always be on the green line. An ordinary PWM controller simply cannot do this. In addition, the MPPT controller allows you to connect an assembly of series-connected solar panels. This method of connection significantly reduces energy losses during transportation from solar panels to batteries. The economic feasibility of purchasing an MPPT controller appears if the power of the installed SPs is greater than 300-400 W. Based on my experience, I can say that it is worth acquiring a solar controller “for growth”, unless a powerful energy system is created immediately, which overlaps with the needs of the house. By the method of consistently increasing the number of solar cells, I came to a power of 800 watts - this is not much, but this is quite enough for a summer house in the summer, so as not to turn to electricity. According to the calculator, my power grid will averagely deliver 4 kWh of electricity per day from April to August. If you do not use an electric stove and a microwave for cooking, then this amount of energy is enough for a comfortable life for a family of 4 people. But there is still a powerful electricity eater in a private house in the form of a boiler for preparing hot water. It will take about 4.5 kWh of electricity to heat an 80 liter boiler. Thus, the autonomy should pay off at least by heating water or servicing other consumers.
In the last article, I talked about a hybrid inverter that can use energy with priority from solar panels and only take away the missing from the network. How does this relate to the solar controller? The fact is that the Russian company MikroArt has recently begun to produce its own MPPT-controllers , which can be connected to inverters of the same manufacturer via a common bus. Well, since I already have a hybrid inverter installed, with the new season I decided to try a new controller.



I must say that it looks brutal with respect to the two previous controllers, which I already have in my household. Metal case, radiators on the sides (Chinese models have radiators on the back wall), dark gray steel case. Recently, I began to like that in my household controllers begin to “communicate” with me in Russian. There used to be pictograms, numbers and English inscriptions. It can be considered a whim, but it's nice. I will not compare the new controller with the previous models in this article, but I will carry out testing with Chinese models in a separate text. Perhaps there I will also consider the expediency of acquiring a more or less powerful controller, features of work and reliability.
The biggest advantage of this controller for me is the possibility of pumping the required amount of energy so that energy does not come from the battery, which reduces its life. Of the three models that are presented by the manufacturer, I chose the most popular and optimal voltage / current ratio - ECO Controller Energy MPPT Pro 200/100 . Based on the characteristics of the device, we can say that the controller supports input voltage up to 200 V and output current up to 100A. Taking into account the fact that my battery assembly is 24 V (battery voltage of 12/24/48/96 V is maintained), the controller will allow to issue a maximum power of 2400 W, that is, I have a double reserve for building solar batteries. The maximum power of the controller is 11 kW at 110V on batteries (buffer voltage). The controller communicates with the hybrid inverter MAP SIN Energy Pro HYBRID v.1 24V on the I2C bus and can instantly add power when the inverter provides information about the increase in energy consumption. The interaction of two devices of the same company is, as a rule, a system that has been worked out, so it all comes down to plugging one cord into the necessary device connectors and activating the necessary parameters. I was also interested in the statement of the manufacturer of this controller that this MPPT controller can also instantly add power when using an inverter from any other manufacturer. It became interesting how it is implemented. Everything turned out to be extremely simple:

The current sensor is hung on the positive wire leading to the inverter (which is why the inverter manufacturer is not important) and using the Hall effect the controller calculates the power consumption. Here the logic of the solar controller itself comes into operation and it pumps up the necessary amount of energy. All controllers known to me rely on the battery voltage, and only considering it, increase the charge current.
Continuing the study of the capabilities of the controller, I was faced with the fact that it is equipped with three relays, the operation of which can be programmed. For example, if the weather is sufficiently sunny and there is no electricity consumption by the house, you can start heating an additional boiler or pool. Consider the opposite option: there is no sun, the battery voltage has dropped to a critical level, when the inverter can simply turn off and energy consumption continues. Then you can run a separate benzo / diesel generator, simply closing the relay. But for this, the generator must have a dry start contact or a separate automatic start system or SAP (also called ATS - Automatic Input Reserve). Since I, like most gardeners, have a simple Chinese generator, but with a starter, I looked towards automating its launch and was delighted to hear that MicroArt has been releasing its automation for a long time.
Let's go back to the controller. Its installation is standard: the battery terminals are first connected, then the solar battery terminals are connected and the parameters are set. By connecting an external current sensor, you can observe how much power the inverter consumes in real time.
So, unwind the wires, mount the controller and start saving. The following photo demonstrates the operation of the inverter in the hybrid mode, when only a part of the energy is consumed from the network, and the main part from the solar panels.


The solar controller is specifically connected via an external current sensor to demonstrate operation with any other inverter released by a third-party manufacturer.


Total
The solar controller complies with the declared characteristics and really boosts energy, even being connected to a “foreign” inverter via a current sensor. The hybrid inverter really pumps energy from solar panels into the network (in the photo, 200 watts consumed half, that is, 100 watts comes from the sun. The controller will always take the minimum 100 watts out of the network, and take the rest from the sun - this is a feature of the device). Simply put, the set from the moment of connection began to pay for itself. Unfortunately, spring has suddenly changed into a blizzard, and in the near future it is unlikely to be able to observe the high efficiency of the kit (hybrid inverter + solar controller), but since May I have been counting on the almost complete coverage of my energy needs at the expense of the sun.

Announcement
In the next, final article, I will compare the three solar controllers I have and will try to answer all the questions that have arisen during this material cycle. If any topic remains undisclosed and it will be of interest to a large number of readers, then I will try to get together and give a separate material. And now I am ready to answer questions. May the Power of the Sun be with you!