The changes to the Energy Law proposed by the Ministry of Climate and Environment have recently caused quite a lot of controversy, both among installers who assemble photovoltaic installations and end customers who are afraid of the lack of profitability of the investment. Observing the photovoltaic markets of neighboring countries, it is easy to notice that with the growing dynamics of photovoltaic investments, legislators are abandoning the net-metering settlement system.
A solution that can significantly contribute to the profitability of investing in your own photovoltaic power plant may be an increasingly wider offer of electricity storage units designed to work with solar inverters. These solutions not only ensure a higher consumption rate, but also eliminate the problem of the installation shutting down when the voltage in the power grid is too high. The above occurs especially in single-family housing areas, where a large number of installations and, at the same time, low electricity consumption during the day contribute to frequent switching off of inverters due to reaching a voltage value exceeding the permissible level in accordance with the IRiESD of the energy company to whose network the installation is connected. .
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The changes proposed in the draft bill are aimed at abolishing net-metering and the discount system, which have been known for years. This will mean the inability to store electricity produced by a micro-installation in the power system at a time when the installation achieves a high level of production with a simultaneous low consumption and its subsequent use during a shortage. According to the change proposed by the ministry, settlement is to be based on the principles of resale of surplus energy to the distributor at wholesale prices and purchase of energy at much higher retail prices in the event of a shortage. If the draft amendment to the RES Act of June 2, 2021 is accepted by the Sejm and the Senate, and the act is finally signed by the President of the Republic of Poland, after January 1, 2022, any investor who decides to install micro-installations will be able to resell only surplus electricity. However, the above changes will not apply to installations that were connected to the power system before the end of 2021. In this case, the current settlement method is to operate for another 15 years.
Energy storage from renewable energy sources
Photovoltaic installations, especially in residential buildings, generate a lot of electricity during the day, especially in spring and summer, when the auto consumption rate is relatively low due to the lack of residents. This results in the need to introduce significant electricity into the power system in order to be able to use it later in the afternoon. The existing net-metering system made it possible to receive, respectively, 80% (for installations with a capacity of up to 10 kWp) and 70% (for installations from 10 kWp to 50 kWp) of the electricity "stored" in the power system at no additional costs. With a properly sized installation, the prosumer was only charged with transmission fees.
Taking into account the proposed changes, it is quite easy to see that the interest in electricity storage should increase significantly.
Changes in the RES Act – expected price increase
Based on the current electricity prices on the Polish market, it is estimated that the supplier will pay approximately PLN 256 for 1 MWh introduced into the power system, and the recipient, in the event of a shortage of electricity, will pay approximately PLN 667 for its purchase for 1 MWh. Therefore, prosumers should expect an increase in their electricity bills of up to PLN 1,000 per year (according to estimates presented on the website Wysokinapiecie.pl).
Energy storage – offer overview
Most of the solar inverters available on the market can be retrofitted with electricity storage in order to increase the self-consumption rate, which may contribute to minimizing losses related to discounts and significantly increase the profitability of the installation in the case of the new settlement method that is the subject of the draft amendment to the Act.
The main principle of cooperation between the inverter and the energy storage is based on the storage of electricity, which in the classic on-grid solution was sent to the power system. Electric energy storage systems are specialized solutions, much more technologically advanced than the previously known island systems based on a charging controller and batteries (usually in lead technology) operating
in simple off-grid installations, such as autonomous lighting poles. The distinguishing feature of this solution is the technology of the batteries used (made using lithium-iron-phosphate Li-FePO4 or lithium-ion Li-Ion technology) and the possibility of expanding the storage system. It is worth mentioning, however, that despite the modular structure of most solutions currently available on the market, the possibility of expanding the energy system is limited in time, which results from the different discharge characteristics of the batteries in use compared to the new units. Most warehouse manufacturers allow for system expansion within no more than 2 years from the start of the installation. With this in mind, it is important to properly dimension the storage system already at the investment stage.
An additional functionality obtained by using energy storage in the installation is the ability to obtain emergency power supply (buck-up), usually a separate part of electrical circuits in the event of a lack of primary power supply (from the power grid). The above functionality is possible when using automatic reserve switching systems and, depending on the inverter used, it can function with single- or three-phase emergency power supply, even though the inverter itself has a three-phase output. Taking into account the capacity of the warehouse, emergency power supply is usually limited to a separate area
loads of strategic importance (in a single-family house, it is usually the power supply circuit for a refrigerator, lighting or building automation).
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Another quite important way to increase the self-consumption rate is to control electricity consumption by switching on loads with relatively high energy consumption, such as the heater in the domestic hot water tank. This solution can be achieved, for example, by installing an Ohmpilot device in an installation with a Fronius inverter, which controls heating devices via the inverter's automation. For this purpose it is necessary to apply
electricity meter at the entrance of the installation in order to monitor online the consumption of energy produced by the micro-installation by loads connected to the receiving installation. If the inverter detects too low energy consumption, it will switch on the heating devices. A similar solution can be used in Solaredge devices, here, apart from the water heating device, it is possible to control the switching on of the plug sockets to which the loads are connected or the switching on of the charging point of an electric car.
The appearance of LUNA 2000 series energy storage units in HUAWEI's offer significantly increases the attractiveness of the offer in terms of new arrangements. The system is characterized by simple installation, high level of safety and reliability, used in single- and three-phase systems, and is intended for installation in both home and commercial installations. Thanks to its modular structure, it is possible to scale the warehouse with a capacity ranging from 5 to 30 kWh. The warehouse consists of a control module and energy storage modules attached to it. Each SUN2000 M1 series inverter allows you to connect up to 2 energy storage units, each with a capacity of 5 to 15 kWh. The compact design of the system means that its use does not require a special room, and thanks to the housing with IP66 protection level and operating temperature from -10 to +55°C, it can even be installed outside the building.
MSc. Jan Makowski
Regional Technical Advisor – Designer
Onninen Technical Consulting Department
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