- Requirements for the construction site
- Hybrid grid configuration
- Power distribution equipment
- Improving the efficiency of autonomous systems
- Full and partial duplication
To be independent from the work of the city infrastructure, it is necessary to foresee in advance the possibility of power outages and come up with a backup power supply option. We will tell you about how to achieve full energy autonomy of a construction site or house.
You can use any of the currently known sources as a backup, it doesn’t matter. It will be about the general concept and construction of a set of equipment capable of converting electricity and maintaining its supply.
Requirements for the construction site
If the construction site really requires that the power system be kept connected at all times, it is necessary to allocate a room for special equipment. Among other things, it must contain the required amount of primary fire extinguishing means..
The door to the premises should be locked with a padlock to protect against strangers. A contact sensor should be installed on the door, connected to the alarm system and the circuit for transferring to manual mode.
In addition to the battery park, an emergency generator can be stored in the room. This is quite acceptable from a safety point of view, but if you plan to automatically start the generator indoors, then you need to equip with an exhaust system.
Hybrid grid configuration
The center of a hybrid power grid is always a device whose principle of operation is very similar to a water supply manifold. Electronically controlled devices allow you to set the operation algorithm through the service interface, relay circuits are not so easy to set up.
The second integral part is the battery park, the total capacity of which is calculated based on the maximum energy consumption of the facility and the longest period when the facility remains completely without power supply in the most negative scenario of eliminating the accident. This period can range from a few seconds (the time the generator is put into operation) to several tens of hours (with systematic rolling shutdowns).
1 – generator; 2 – solar panels; 3 – controller; 4 – batteries; 5 – counter; 6 – inverter; 7 – load control relay; 8 – consumers
The battery park has one or more inverters connected via a charge controller. As a rule, these consumers are given the highest priority, so the system always keeps the maximum battery charge level and primarily takes power from the network for its own needs..
The operating principle of the system is easy to imagine, based on the concepts of excess, shortage and capacity. Energy is always allocated on the highest priority line, even to the detriment of other consumers. If there is not enough energy in the network, one of the backup sources is involved. As soon as the demand for electricity disappears, power is removed from the consumer of the first priority and sent to the second, the rest to the third. If the system produces more energy than needed, it can dump the surplus into the city grid or stop the sources one by one..
Power distribution equipment
A rather complex algorithm of work is performed automatically. However, the degree of automation, as well as the number of connected sources and consumers, can vary greatly from model to model..
The first part of the system is a conventional solar controller such as MPPT Pro. It is assigned the task of choosing between the consumer of the first priority and the main load. Along the way, on the display you can see the current parameters of the first link of the system and set some operating parameters. Please note that the controller must be fully compatible with the inverter and deliver pure sinusoidal current. Common and inexpensive solar controllers are limited only to pre-filtering harmonics, but this can be filled with additional devices..
The second link is the load control unit, which distributes the load among all secondary consumers. In the simplest case, the unit includes one or more load control relays (priority relays like ABB LSS). The disadvantage of a relay device is that its settings are only manually set, and the current input power of the system is constantly changing. Therefore, such a distribution is acceptable only for the simplest networks, for example, when it is necessary to limit consumption during the day in order to allow the batteries to fully charge..
Please note that using three-phase priority relays, you can not only select priority consumers, but also priority power supplies. In such a case, you can create a rather complex scheme in which the reserve is represented by several sources: a solar farm, a second city input, a wind turbine or a generator..
Improving the efficiency of autonomous systems
Another way to increase energy autonomy is to fight for energy savings and increase system efficiency. This primarily applies to control equipment. Its losses and its own consumption are low, but constant: in large systems it can amount to several kW / day. The efficiency of relay equipment is much lower, while for semiconductor devices it is 90–98%.
You can also increase the efficiency of the system by increasing the efficiency of backup sources. Timely cleaning is essential for solar panels. It will not be superfluous to install azimuth tracking devices so that the light always hits the panel plane at an angle close to a straight line. An advanced ignition and choke control system is critical to the generator. During periods when consumption drops slightly, the generator consumes part of the fuel idle.
It is very reasonable to minimize the load on the system in affordable ways: purchase equipment with a high energy saving class, switch to LED light sources, and minimize electricity costs for heating. A good help in this matter can be the laying of a low-voltage lighting network and a direct supply of 12 or 24 volts to household appliances (with its conversion), bypassing the inverter. Such organizational measures often give even more results at a lower cost than a constant increase in capacity..
Full and partial duplication
To increase the fault tolerance of the system, it is necessary to test it in the first months of operation and identify weaknesses. An example would be the case when, over several cloudy days in a row, a solar farm in total produces less energy than is required, which is why the batteries are on the verge of discharge. The energy deficit can be very small (1–2 kW / day), but in a few days it absorbs the entire available reserve. The solution to the problem is an additional fleet of small-capacity batteries, which is able to replenish the daily need in case of a lack of generation.
It is also recommended to duplicate control and conversion devices, but their cost is too high. It makes sense to add an additional inverter (to the three already standing ones), so that if one fails, it can be instantly replaced. Sometimes it makes no sense to duplicate an expensive controller, so it is replaced with a simpler relay circuit that can work according to an elementary scenario during repair work.