In September 2020, China clearly put forward the goals of “carbon peaking” by 2030 and “carbon neutrality” by 2060, namely the “dual carbon goals”. Solar photovoltaic power generation is a typical form of green energy, and vigorously developing solar photovoltaic power generation is an important measure to achieve the dual carbon goals. Building large-scale solar photovoltaic power stations in suitable locations is the main form of solar power generation.

I. What is a Distributed Solar Photovoltaic System?

1. Relatively small output power. Generally, the capacity of a distributed PV project ranges from several kilowatts to within one megawatt. Unlike centralized power stations, the size of a distributed PV station has little impact on power generation efficiency, and thus has little impact on its economy. The investment return rate of small-scale PV systems is no lower than that of large-scale ones.
2. Low pollution and prominent environmental benefits. During the power generation process of distributed PV projects, there is no noise, and no pollution is caused to air or water.
3. Photovoltaic power generation has a peak-shaving effect. It can alleviate the local electricity supply shortage to a certain extent and reduce the pressure on the power grid during peak electricity consumption periods.
4. Concurrent power generation and consumption. Large-scale ground-based power stations boost the voltage of generated electricity and connect to the transmission grid, operating only as power generation stations; while distributed PV systems connect to the distribution grid, enabling concurrent power generation and consumption, with the requirement to consume electricity locally as much as possible.
5. Increasingly prominent economy. As the costs of equipment such as photovoltaic modules and controllers decrease, and coupled with national subsidy policies, the investment returns of PV projects built by many industrial and mining enterprises, shopping malls, and buildings are increasing. According to the latest calculation of the price difference between industrial commercial electricity and the cost of electricity generated by PV, the investment payback period is about 5 years (with an annual investment return of approximately 20%). As solar PV technology develops and the cost of modules further decreases, the investment returns of distributed PV will be even higher.
6. Alignment with national policy directions and access to policy dividends. Relevant plans released by the state clearly propose to encourage the construction of distributed PV systems integrated with buildings in central and eastern China. Although subsidy plans vary across provinces and cities, most of them are still in implementation. In the future, building PV projects on residential premises and constructing PV parking lots by enterprises and public institutions may become promising investment targets.

II. Network Connection Solution for Distributed PV Systems

Once a distributed photovoltaic (PV) system is connected to the network, it not only enables real-time collection of power generation and consumption data from distributed points via a centralized management system, but also allows real-time access to on-site high-definition images. This facilitates security for the system as well as management, operation, and maintenance for users.

Based on years of experience in solving network connection needs across various industries and scenarios, Guoxin Longxin has summarized two solutions suitable for distributed PV system networking. They are as follows:

1. Wireless Private Network – iMAX 5G WMAN (Wireless Metropolitan Area Network) System

A Wireless Metropolitan Area Network (WMAN, abbreviation of “Wireless Metropolitan Area Network”) refers to a locally distributed wireless network that transmits information between distributed nodes covering an urban area geographically, i.e., a wireless network built on the basis of a metropolitan area network (MAN). A wireless private network, as the name implies, is a dedicated wireless network built by a specific enterprise or public institution and not open to the public (some private networks have public network interfaces to facilitate Internet access).

Large industrial and mining enterprises are well-suited to build private networks within their premises, mainly for two reasons: first, private networks are used exclusively, ensuring higher security and reliability; second, they require a one-time investment with no subsequent link rental fees or data traffic charges, resulting in better economic efficiency.

The iMAX 5G WMAN system provided by Guoxin Longxin boasts unique technical advantages and outstanding performance, which are unmatched by other wireless broadband devices. These advantages include support for multiple networking modes, IP67 protection standard, long-distance transmission, high bandwidth, strong anti-interference capability, high reliability, easy installation, and convenient maintenance.

The iMAX wireless communication system is designed to build wireless cities or solve ultra-long-distance network interconnection in outdoor environments, so all series of its devices offer extremely long communication distances. Among them, the iMAX-6000 series serves as the urban backbone network, while the iMAX-8000S and iMAX-8000H series act as edge access networks.

• Communication Distance: Under line-of-sight conditions, the iMAX 5G dedicated wireless network communication system – specifically the iMAX-8000 series – can easily meet access requirements with a radius of 10 km or even 50 km in point-to-multipoint networking mode. In point-to-point mode, the maximum distance can reach 100 km.
• Transmission Bandwidth: The iMAX-8000H is a 300/600 Mbps point-to-multipoint communication system, the iMAX-8000S is a 100 Mbps point-to-multipoint communication system, and the iMAX-6000 is a 150/300/600 Mbps point-to-point communication system. Additionally, base station bandwidth can be increased by N times through frequency division to enhance the total system bandwidth. High bandwidth and large video capacity are its greatest advantages.

For on-site information points (such as data acquisition and control points, video surveillance points) of distributed PV systems in industrial and mining areas, network access can be fully achieved through the iMAX 5G WMAN system. For the backbone network, solutions such as self-built/leased operator optical cables (dedicated lines) or SD-CX private cloud virtual private networks (VPNs) can be selected based on actual communication conditions. If conditions permit, the iMAX 5G backbone wireless system can also be directly used.

By adopting iMAX WMAN technology to solve the wireless private network access of distributed PV systems, the video surveillance system can optionally use the current mainstream IP digital network video surveillance system. Generally, there are not many on-site surveillance points, and the storage time is not too long. Therefore, configuring IP network cameras (IPCs) at front-end surveillance points and using network video recorders (NVRs) for storage offers the highest cost-effectiveness. To meet the demand for 24/7 uninterrupted surveillance at construction sites, infrared integrated network bullet cameras or infrared network high-speed dome cameras are suitable choices for IPCs, which can be matched with corresponding NVR systems.

After the iMAX wireless private network system is built, each distributed PV information point will essentially have its own dedicated office private network. A variety of services can be directly deployed on this network, including high-definition video surveillance, video conferences, office OS systems, and information acquisition and control. In other words, this solution can provide user units with more usage possibilities and further enhance the application value of the solution.

The network topology diagram of the iMAX 5G wireless private network for campus distributed PV systems is as follows:

Benefiting from the advantages of convenient and flexible networking of the iMAX 5G Wireless Metropolitan Area Network (WMAN) private network, the monitoring and detection points of distributed photovoltaic (PV) systems can not only be fixed points, but also deploy movable portable monitoring points or vehicle-mounted monitoring points, further enhancing their applicability.

2. Remote Wide Area Network (WAN) Networking Across Locations – Cloud Exchange SD-CX + VPN Virtual Private Network Solution

For large-scale PV investment enterprise groups, their invested distributed PV projects are distributed across the country. While wireless private network can be used within a single project, it is not suitable to adopt wireless private network technology for networking between different project locations, especially for remote networking across locations. If distributed PV projects nationwide need centralized network management, WAN technology must be adopted. Combining Guoxin Longxin’s valuable experience accumulated over years in the Internet of Things (IoT) industry, a solution based on the integration of “cloud exchange” and multi-mode gateways is proposed.

A cloud computing platform, also known as a cloud platform, refers to a service based on hardware and software resources that provides computing, network, and storage capabilities. Cloud computing platforms can be divided into three categories: storage-oriented cloud platforms focusing on data storage, computing-oriented cloud platforms focusing on data processing, and comprehensive cloud computing platforms that balance both computing and data storage/processing. With the development of cloud computing, almost every enterprise is using or planning to use cloud computing, which has three different cloud models: public cloud, private cloud, and hybrid cloud.

The cloud is “in the sky” – how to connect “on-the-ground” services to the cloud? For public clouds, the Internet is usually selected, with common options being broadband access from telecom operators; for private clouds, VPN or dedicated line access is chosen, with common methods including dedicated line access from telecom operators and self-built optical fibers or wireless private networks by users. Since private networks are exclusively used and isolated from public networks, their connection bandwidth, reliability, and security are significantly higher than ordinary broadband. Whether for public clouds or private clouds, there is the challenge of how to connect edge nodes to the cloud.

Guoxin Longxin’s iMWB-5GW1000 series 5G WAN multi-mode edge VPN gateways and iMAX-4GW300 series 4G WMAN dual-mode wireless gateways are powerful tools for connecting cloud computing edge nodes to the cloud. Taking the iMWB-5GW1000 as an example, it provides multiple Ethernet ports and can be used as a multi-network convergence gateway. In terms of wireless communication, it can not only leverage 5G wireless technology to achieve high bandwidth, high reliability, and high capacity, but also support local high-performance WiFi 6 coverage, providing users with more flexible and optimal wireless networking solutions.

Why is Guoxin Longxin’s SD-CX solution considered the best solution for remote cross-location networking of distributed PV systems?

First, Powerful Hardware Products

The iMWB-5GW1000 is the first 5G multi-mode wireless gateway system under the iMWB brand. It supports both 5G WAN (SA & NSA) and WiFi 6 wireless local area network (WLAN) coverage (2.4GHz & 5.8GHz), and provides 2 Ethernet ports, which can be used as an edge VPN access gateway for cloud exchange platforms. While utilizing WiFi 6 wireless technology to achieve high bandwidth, high reliability, and high capacity, it also supports 5G network access from telecom operators’ public networks, providing users with more flexible and optimal wireless networking solutions.

The iMAX-4GW300 is a dual-mode wireless gateway system under the iMWB brand, supporting both iMAX Wireless Metropolitan Area Network (WMAN) and 4G LTE (FDD-LTE & TDD-LTE) technologies. It provides 3 Ethernet ports and can be used as a multi-network convergence gateway. While leveraging iMAX wireless private network technology to achieve high bandwidth, high reliability, and high capacity, it also supports 4G LTE network access from telecom operators’ public networks—this enhances the applicability of the system’s wireless networking and provides users with more flexible, optimal wireless networking solutions.

Both devices feature an indoor design, with small size, light weight, and low power consumption. They can not only provide IoT terminal networking in industries such as environmental protection, ports, water conservancy, and electric power, but also meet the built-in needs of integrated systems (e.g., UAVs, portable monitoring points, vehicle-mounted, ship-mounted, and aircraft-mounted systems). They are ideal choices for high-quality multi-mode wireless communication in the IoT industry.

In other words, based on networking via access methods such as LAN interconnection, MPLS dedicated line access, Internet broadband access, iMAX Wireless Metropolitan Area Network (WMAN) private network, and 4G/5G Internet access, these two devices can serve as integrated switching gateways to enable interconnection among various TCP/IP network devices (e.g., IP cameras, computers, tablets, advertising screens, PLCs, IP phones, and IP broadcast speakers).

In addition, for users who need to build a private cloud via home broadband wired networking, Guoxin Longxin offers a low-cost edge VPN gateway option—the Layer 3 routing VPN gateway product iMWB-ROUTE400G. This product is a 5-port intelligent managed routing VPN gateway device with full Gigabit ports. It supports intelligent network management and Layer 3 routing configuration, and can be used as an enterprise-level router or a VPN access terminal.

Second, Secure and Reliable Cloud Interconnection Framework

Guoxin Longxin’s SD-CX solution is an Internet solution based on cloud platforms. It can be deployed on private clouds, public clouds (e.g., Tencent Cloud), or hybrid clouds. The cloud-system-based SD-CX is referred to as “Cloud Interconnection SD-CX (SDN-based Cloud Exchange)”. Guoxin Longxin focuses more on users’ actual application needs, with the fundamental system design tenets of enhancing security, reducing costs, and meeting requirements—this reflects Guoxin Longxin’s capability to implement technical solutions.

Specifically, Guoxin Longxin’s SD-CX solution customizes the integration and cloud interconnection of “Wide Area Network (WAN) + Wireless Metropolitan Area Network (WMAN)/Wireless Local Area Network (WLAN) + VPN technology”, where VPN technology serves as the core of the solution’s security assurance.

Virtual Private Network (VPN) technology establishes a “private network” on a “public network” (or an encrypted private network on a dedicated network to enhance security) for encrypted communication. VPN technology mainly relies on tunnel encryption protocols, with typical tunnel protocols including PPTP, L2TP, and IPSec. Hsinchu Technology’s solution adopts a hardware-VPN-device-centric approach of “VPN server + VPN gateway”, which undoubtedly offers higher reliability and security.

It should be noted that some distributed PV equipment manufacturers can provide cloud platforms to aggregate and manage the system’s operation data. However, connecting one’s own production and operation data to a third-party public platform has two major drawbacks: first, it is not secure enough, making information leakage and even network intrusion likely; second, its reliability and stability are poor, increasing the risk of data loss. Building a self-owned distributed PV operation and management system is a necessary measure for technologically advanced management and keeping data in one’s own hands.

The topology diagram of a typical SD-CX distributed PV system for multi-point centralized networking is as follows:

In summary, Guoxin Longxin’s SD-CX solution can connect to various IP terminals, including computers, IP cameras, video conference terminals, PLCs, sensors, IP broadcasts, and large screens. To a certain extent, this solution can address the networking needs of any device based on TCP/IP networks. As an IP network channel, whether for wired or wireless connections, optical networks or wireless networks, we adhere to the principle of recommending what users need and what is suitable for them, and customize comprehensive link solutions for users. Our starting point has always been network security and stability, as well as service availability and practicality.

It is important to emphasize that Guoxin Longxin’s SD-CX solution is a comprehensive service-oriented solution based on GL Technologies’ proprietary multi-mode gateways. It is no longer a mere product, but a set of methods and ideas for solving networking challenges. Therefore, customization can only be achieved on the basis of researching and in-depth studying users’ actual business needs.

In addition, when adopting 4G/5G for networking, the initial one-time investment is relatively low, but there will be ongoing operational costs such as data traffic fees, dedicated line fees, and cloud service fees. Furthermore, this networking solution cannot be used in areas without 4G/5G signals from telecom operators. Even in areas with 4G/5G signals, due to the inherent “tidal effect” of public networks, their bandwidth, reliability, and service quality are weaker compared to private network solutions. For projects requiring high system reliability, wired or wireless private network solutions should still be selected.

It is also important to emphasize that this solution can provide users with relatively secure means to meet their security needs for business networking, especially when connecting to public networks. Networking through this solution can effectively prevent cyber security issues such as hacker intrusions caused by “exposed connections” on the Internet.

Among the two aforementioned solutions, the wireless metropolitan area network (WMAN) private network is suitable for networking within a specific area of an enterprise or public institution, while the wireless wide area network (WWAN) is suitable for centralized remote networking across multiple locations nationwide. These two solutions are complementary and can be integrated into a combined design.

To address the specific networking and management needs of distributed PV systems, it is often necessary to conduct repeated communication and research with users to design an ideal solution. Guoxin Longxin will leverage its rich past experience and solid technical capabilities to customize the most reasonable networking solution for enterprises, public institutions, or PV industry investment groups.