Green energy for base stations and only up to 2 kW - three years of experience with wind turbines, solar generation + geoprobe


    Installation of a wind


    generator A wind generator, a container with batteries, a geoprobe and a base station in Samara

    About 3 years ago, we started an experiment to provide base stations with energy from sources on site. Six months later, it became clear that the geosonde for base stations is a very useful thing in the middle lane, the solar batteries of the Zelenograd plant show themselves remarkably, but the main problem is not in generating energy, but in its transformation and accumulation.

    I’ll tell you about broken windmills and what we understood in three years, and a unique geoprobe for cooling racks with communication equipment.

    Experiment


    Test base stations are located in Samara and Murmansk. In Samara, the base station is powered by alternative energy and is insured by the usual industrial input from the "city". In the event of a power outage from our installation, the base station switches to the city network and continues to work. The second object on the coast of the Barents Sea immediately became autonomous; there was no urban network there. In the event of a power outage, a diesel generator set was installed with a daily fuel supply and a controller that allows it to be launched remotely.

    In Samara, we also drilled 25 meters down and put a geosonde, which allows us to get a good temperature difference with the surface.

    According to the results of three years, it can be said that everything works quite stably, but in order to reach this stability, it took a lot, a lot of rakes, experience and improvements. I’ll say right away about the payback - in Samara, the system goes into plus after five years in comparison with the work from DGU, in Murmansk it is much faster - in 3 years.

    Equipment


    Let me remind you that we put sensors on objects and collected data, plus used statistics. The results obtained diverged slightly with subsequent practice, but not critically. Here's what happened: in Samara, the average daily consumption is 19.2 kWh, the average annual wind speed is 5.2 m / s, the arrival of solar radiation is 4.5 kWh per square meter per day. In Murmansk, the average daily consumption is 26.4 kWh, the average annual wind speed is 6.5 m / s, the arrival of solar radiation is 3 kWh per square meter per day.



    In Samara, we installed a 4 kW wind generator and 6 solar panels of 200 watts each. The base station was on a hill, the winds in the region were on average quite good. The first problem was with the Israeli wind turbine, which, apparently, was designed for a special Israeli wind. In general, he was very smart and functional, but did not give out the declared characteristics. But the Dutch windmill was simple and reliable as a Kalashnikov assault rifle (and with a roughly comparable amount of automation, a “weather vane” with a passive wind orientation system), but it delivered exactly what was promised. All the time until one of the blades literally recently pulled out almost a hurricane atypical for the region. The same windmills are used in Africa, and there they have proven themselves well even in conditions of a mass of abrasives in the air.



    In Samara, a horizontal-axis wind turbine, the estimated wind speed is 12 m / s, the rated power is 4 kW, the rotor diameter is 4.2 m, the operating range is up to 55 m / s, the efficiency is 43%, the average daily output is up to 12.5 kW * h


    Plain, we are on a rise.

    In Murmansk there is also a horizontal-axis wind turbine, rated 12 m / s, nominal 4 kW, rotor diameter greater than 5 m, operating speed range up to 60 m / s, efficiency 45%, daily average output of as much as 38.6 kW * h


    Murmansk sea coast, installation site

    In Murmansk, the wind in Samara - the sun. The windmill begins to give sufficient current only when the wind is strong. There is almost a cubic dependence on wind speed, so it is really good only on cloudy days when there is no sun, and what a wind. But without this in any way - on such days you will not charge otherwise.



    The base station itself consumes about 500 watts, on average, the cooling system takes the same amount. Below, at a depth of approximately between 30 and 50 meters, it is warm and attractive: there, regardless of the season, the temperature is kept from +4 to +8. If you dig a kilometer, you can meet quite hot places, but such geoprobe are made for data centers in Iceland, for example. We have the opposite system - we lower the water down, wait until it becomes about +10, then raise the cooling equipment up. Instead of 500 watts for air conditioning, we got 15 watts for the pump. Cooling power - 2600 W, electricity consumption - 35 W (together with additional systems), well 25 meters.


    Water from a geosonde

    In Murmansk, you can’t get stuck with a geoprobe - the soil is rocky, and such a solution will definitely not be included in the series. Even in Samara, we got two drills stuck while everything was done. In Murmansk, such a good wind on the coast that bent the mast of one of the test wind generators at the very beginning of the project.


    But a lot of good support for the generator mast.


    Here is the mount



    System optimization


    Firstly, the equipment of the base station consumes 48 V. At the first stage, we crashed before entering the base station into the container. It turned out this way: we give out direct current, it must be converted to 220 for the standard BS input interface (designed for the city network), and then again get 48 to power the equipment. Still, I had to crawl into the typical configuration of the base station - we saved about 9% on these extra transformations. True, 220V on a BS is still necessary - this is monitoring equipment and other auxiliary things, but they consume little. To work this way, you need to mount the equipment in one container (thermal box) with the BS itself - initially, specifically on that BS, our container was separate.

    Secondly, it was necessary to dump excess energy in certain circumstances. We mounted small heating elements outside the container to warm the surrounding air in the case when you do not need to recharge the battery.


    Murmansk, equipment delivery, the BS container is visible

    Thirdly, it turned out that one more heater was needed inside the container. The fact is that once the temperature inside dropped to +5. Telecom rack is good, but the batteries (ours and UPS BS) - not very. But this is better than heating to +35, when the batteries age in front of our eyes, and with each new degree, the service life is floating directly. So, it is more efficient to spend energy on heating a thermal box than to lose capacity due to cold.


    Automation shield, solar panel controller and inverter

    Fourth, we put the first solar panels at the rate of "how much will fit on a container." Now in serial projects will include not 6, but 12 pieces - they are not very expensive, and the profit is very, very good from such a doubling. By the way, the batteries from Zelenograd themselves proved to be excellent - there have been no complaints about them from the first day, the output current has been stable and has not been falling for 3 years.


    Experienced installation

    Fifth, the work with the charge controller turned out to be very important. A more complex algorithm for calculating the optimal charge current and the optimal use of energy from a wind turbine and batteries in different modes made it possible to clearly find the optimal point from the curve of the charge characteristic. We constantly adjusted it on the basis of the data collected, and now we have a very good heuristic that is applicable in any region except the far north (but there it is a matter of a month or two to get the necessary data).


    Parallel ballast branch junction box

    Fifth, our bottleneck is the battery. It is the most expensive, in particular, because it requires regular replacement every few years. The first high-capacity salt battery with a molten salt inside was ideal, but fantastically expensive. The series will include ordinary lead elements. And here there is another important point - the batteries are already on the BS, these are UPS units, which last for several hours of broadcasting the station. Our battery is 800 ampere hours, the array available on the BS is 500 ampere hours. On one of the BSs, the operator proposed combining our batteries and them to get an array of a larger capacity. This is usually not done with different types of batteries (this reduces the life of the battery), but it was also important for the operator, and it was important for us to obtain experimental data from increasing the capacity. Connected. We will introduce such batteries in the series so that the battery bank is common. After the rectifiers are our controllers - they make power take-offs for our batteries and BS batteries. It also gave optimization in the event that, due to bad weather, it was necessary to start a diesel generator set.




    Sixth operator’s shield , we immediately made good monitoring. It required minor modifications, which was important - to put a new DGU control contactor in order to put the diesel into manual mode, start and stop. At first, often it was necessary to change the thresholds for starting a diesel engine with a low battery voltage, then, again, they gained the necessary experience. As a result, the sensors are at all sources and consumers, we see how much comes from solar panels, what is the output from a wind generator, voltage across all sections of the circuit, consumption. There are weather sensors (temperature-wind), two cameras for external and internal surveillance (it is convenient to look at the rack through the camera).


    The same operator’s shield

    Seventh, in Murmansk there was a freecooling system instead of a geoprobe. There was a difficulty with her. The problem is that the hot air valve was in the container wall on the opposite side of the cold fence. So, with strong winds, this valve (looking like a curtain) simply bent and opened in the opposite direction. Foreigners did not have such an experience. And our domestic manufacturer has already promised another tricky valve, which will not behave this way, now we are just mounting it.


    The wind generator controller

    Now on the way replacement of the battery, let's try another option.

    Series


    Total for the series we see the following scheme:
    - A wind power complex with a mast, for a number of regions it is a Dutch-made wind turbine with a passive orientation;
    - Solar energy complex with 12 panels;
    - Geothermal cooling system, if soil permits;
    - Free cooling system;
    - Power distribution and management;
    - A system of energy storage of 800 ampere-hours minimum;
    - Block container;
    - Video surveillance system;
    - Monitoring system;
    - SCADA scheduling system.

    Maintenance work:
    - Twice a year visual inspection, dust removal and check of mast stretch tension.
    - Once a year lowering the mast of the wind generator, pulling threaded connections, unwinding the cable of the wind generator, checking the batteries.


    BS in Murmansk, lifting the mast of a wind generator





    results


    Our solutions really liked the network operation service. The fact is that the number of trips decreased by 10-12 times. Previously, they went to the DGU refueling station as on duty. On average, 90–95% of the time in our diet, 5–10% of diesel can be obtained on almost any BS. Accordingly, the maintenance of the diesel engine is also done less frequently - it has a TTO for engine hours. By the way, the operators especially liked that when the power line fell nearby, “our” BS did not go off the network.

    Last year of tests after optimization, results. Samara: decrease in BS consumption by 30%, autonomy coefficient - 81%, alternative sources use coefficient - 60%. Murmansk: decrease in BS consumption by 15%, autonomy coefficient - 100% (lucky with the weather, it could be about 97%), utilization rate from alternative sources - 100%.

    I will answer the theoretical questions in the comments, and the practical ones specifically for your subject - in the mail PVashkevitch@croc.ru.

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