The global generation of solar system has grown fast from 2010 because many countries have adapted advanced technologies. Recently, the main focus in distributed PV system, commercial solar system is, how to get rid of subsidy dependence and how to achieve grid parity have become the main problem and urgently require to be solved. Solar power grid parity for photovoltaic power station need further decrease in cost and increase in efficiency. Inverter is the key equipment of photovoltaic system, while the proportion in the whole system cost is not high but by improving the parameters and performance to optimize the system design, intelligent on-line service operations can
The cost reduction and efficiency increase method for inverter is shown below
Adopt new high-efficiency, high-power module and use adaptable inverter
The cost of photovoltaic modules accounts for more than 50% of the initial investment, which directly affects the cost of the project. However, the attenuation of solar panel efficiency leads to the increase of electrical cost. The attenuation rate of solar panel is calculated according to (10% in 10 years and 20% in 25 years). Due to the adoption of new high-efficiency high-power modules, the initial investment of photovoltaic system will drop more than 10%.The improvement of photovoltaic module conversion efficiency greatly reduces the parallel strings. Besides photovoltaic modules, inverters and other devices, including BUS boxes, DC cables, holder and foundations, will also be reduced.
For example a 1MW unit, adopt the same inverter and consider LONG JI brand 350W solar panel as an example, the number of solar panel can be reduced by 280~616 pieces, and the installation and transportation cost solar panel can be reduced by 7.6% to 16.6%.The number of strings can be reduced by 28 strings, saving more than 15% of the cost of holder and DC cables. According to the calculation of about 4800USD of DC cable materials and laying cost per MW and 50700 USD of holder materials and installation cost per MW, the whole system cost per MW can be saved by more than 8300USD.
The new high efficiency and high power solar panel can reduce the system cost, but due to the high power solar panel with high current puts new requirements for inverter and the inverter input current must meet the new efficient solar panel. Growatt new generation MAC and MAX series inverters were designed according to 12.5 A, it is new high efficient and high-power solar panel gold partner and best match with the new advancements.
Due to solar panel loss, dust, shelter, line loss, series-parallel mismatch, insufficient sunshine factors, inverter actually receives the input power is often has reached around 87% – 92% of output power component, which cause the overall loss around 8% – 13%. As the industrial and commercial solar panel mostly use color steel tile roof installation, which cause loss of radiation, if solar panel and inverter according to 1:1 configuration, inverter with light load condition for a long time cause the utilization rate very low, so improve the system capacity ratio and appropriately over-match can improve the whole system benefits and reduce the electricity cost as well. This operation has been widely used, especially in areas such as the United States and Japan, where the ratio can exceed 1.5 times.
Growatt commercial inverters MAC and MAX series have up to 1.3 times of DC over-matching capacity, and 1.1 times of overload capacity for AC, making over-matching easier and more secure.
Adopt aluminum cable instead of copper cable
In large commercial projects, cables account up to 10% of the system cost, higher than inverters cost. In fact as long as the design and installation are proper, under the condition of ensuring the normal operation and safety of the system, some AC cables are made of aluminum, which can reduce the investment cost of the system. Compared with the cost of copper cable, aluminum cable cost is lower, installation is more convenient, weight is lighter, and aluminum cable in the application of photovoltaic system has become more and more common.
However, under the same over current capacity, the diameter of aluminum wire is obviously larger than copper wire, and which need higher requirements for ac connection terminals of inverter and AC connector and waterproof terminals must be large enough to support aluminum cable with larger diameter. Currently, the MAC series of 50- 70kw inverters are compatible with up to 50 square mm aluminum wire, the MAX series of 60-70kw inverters are compatible with up to 70 square mm aluminum wire, and the MAX series of 80-100kw inverters are compatible with up to 95 square mm aluminum wire.
According to local conditions, select the appropriate MPPT strings inverter
At present, there are many specification of MPPT inverter in the market. As the commercial 60kw inverter for an example, there are 1 ,3,4 or 6 strings number of MPPT inverter, Growatt 60KW inverter has three models: single MPPT Growatt 60KTL3 – HE, 3 MPPTs MAC 60KTL3 – X LV and 6 MPPTs MAX 60KTL3 LV model.
The choice of different MPPTs has influence on the power generation of the system. From the point of view of solving the mismatch problem, the fewer strings is best for one MPPT. In terms of stability and efficiency, it is better to have more strings for one MPPT, because the more MPPTs then higher the cost of the system, the worse stability, and the more losses. In the real-time application, the appropriate scheme should be selected according to the practical application scenario.
According to different application scenarios, Angle and orientation of solar array, shielding conditions of solar panel and consistency of the number of solar panel in each string, inverters with different MPPTs can reduce procurement and maintenance cost of power station, also improve economic benefits.
(1) In the case of flat roof without shelter, uniform orientation of solar array and complete consistency of group strings, it is recommended to choose one MPPT inverter, which can improve system reliability and reduce system cost;
(2) In the case of partial shelter, inconsistent orientation of solar array, and different number of solar array per strings, it is recommended to choose 3 MPPTs inverter, which can not only meet the design requirements, reduce the mismatch loss, but also reduce the cost;
(3) In the case of multiple orientations, multiple angles and large difference in number of solar array per strings, it is recommended to select 6-7 MPPTs inverters, which can maximize the mismatch loss and improve the design flexibility.
It is known to all, photovoltaic power station is an up to 25 years of the life cycle of products, price bidding and grid parity. And the time has come, people more and more care about electricity cost, the investment of charge include construction costs and power plant generating cost, also there is a very important part is service and maintenance cost, thus how to reduce the service and maintenance cost of the power station and improve service efficiency to become the industry focus.
Solar inverter as the only intelligent devices in photovoltaic power station, in the process of power plant service intelligence plays an important role, it is not just an inverter, also a steward of the photovoltaic power station. It is not only realize intelligent diagnosis, warning remote parameter setting and the firmware upgrade, but also for photovoltaic modules intelligent IV curve scanning and accurate fault location, optimize the grid power quality , active and reactive power scheduling, Intelligent one-click diagnosis of the installation process and environment of the power station.
Growatt MAC and MAX series commercial inverters have the above intelligent service functions, which can improve service efficiency and reduce service cost for commercial photovoltaic power stations.
Solar power grid parity time has emanated, and trade of photovoltaic power station cost reduction become very critical. Solar inverter selection is particularly important, a smart and efficient inverter can help improve the efficiency of power generation, also to optimize the design of the system, improve life time cycle generating revenue, and reduce the construction cost of power plant. Intelligent service can save the cost of service in the complete life cycle. In order to regulate cost optimal, the selection of inverter become crucial.