ELECTRIC, WITH AN EDGE
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ELECTRIC, WITH AN EDGE
Low-voltage power grid distribution stations bear the function of power transmission and distribution from substations to users in the power system, and the quality of power supplied by them directly affects the quality of power consumption by users and the stability of the power grid. In some remote areas, low-voltage power grid distribution network is weak, and the complexity of the area, the scattered nature and the diversity of user loads lead to low-voltage, low power factor and other power quality problems are more prominent. For power quality control, conventional low-voltage grid upgrading project has large investment, long construction period, and can not be flexibly configured.Mobile Energy Storage, as a subcategory of energy storage equipment, has high application value in comprehensive power quality control of power distribution stations with its flexible configuration characteristics.
Mobile Energy Storage is an emerging solution for power quality management by improving power quality and power supply reliability, and solving problems such as three-phase imbalance and power factor.
When the distribution line is too long or the conductor, cable cross-sectional area is too small, the resistance and inductance of the line when the current passes through the line will cause the voltage to be reduced, which will lead to a reduction in the terminal voltage. The rural distribution network is widely distributed and scattered, and some old stations are not renovated in time, and the radius of power supply reaches more than 1.5 km, so the problem of low voltage is more prominent, and the problem is especially significant during the peak load period.
The daily power consumption load in the station area is diverse and fluctuates greatly, the nature of power consumption and power demand of different equipments are different, as well as the unsynchronization of single-phase load users and the access of high-power single-phase loads, which will cause the three-phase load imbalance of the line. Three-phase load imbalance of the line will affect the operating efficiency of the equipment, increase the loss of the power system, may also produce harmonics affect the stability of the power system.
With the improvement of living standards of the masses, the number of household appliances is increasing, but the distribution network is not upgraded in time, which will lead to the distribution transformer working in the heavy overload state, affecting the stability of the power supply system. Part of the heavy overload problem also exists in seasonal characteristics, such as urban villages are prone to summer air conditioner load triggered by heavy overload, some remote rural areas during the Festivals due to the sharp increase in the load of electricity used by the returnees led to short-term heavy overload, and so on.
There are many inductive loads (electric motors, refrigerators, electric fans, etc.) in the station area, which generate a large amount of inductive reactive power during the peak load period, leading to the problem of low voltage in the station area. The traditional solution to the low voltage problem in power distribution stations is to install capacitors, reactive power compensators, reactive power generators and other reactive power compensation devices, which can improve the power factor, but can only solve a single problem, not comprehensively improve the power quality of the station area, and is not cost-effective.
Mobile Energy Storage consists of a lithium iron phosphate battery storage solution system, a bi-directional converter for energy storage, an energy management system, a fire-fighting system, an air conditioning system and a monitoring system. In order to facilitate deployment between different stations, the capacity of a single energy storage device is generally less than 500 kWh, which has the advantages of flexible deployment, multi-functionality of a machine, installation with electricity, automatic control, cloud platform management and so on. The working modes of applying Mobile Energy Storage for power quality management are as follows.
For the low voltage caused by long lines, small conductors and cables, or over-concentrated loads at the end of the station area, the strategy of charging in the low load period and discharging in the peak load period is adopted to alleviate the load pressure on the front-end lines, and at the same time take into account the reactive power compensation and three-phase imbalance management, so as to achieve the effect of lifting up the voltage of the last section of the lines and ensure the reliable use of electricity by the residents.
For areas where distribution transformer capacity is insufficient and users’ seasonal overloading causes heavy overloading of distribution transformers, when the short-term power consumption is greater than the capacity of distribution transformers, the advantages of rapid discharge of the energy storage system are utilized to avoid long-term heavy overloading. At the same time, Mobile Energy Storage can also be flexibly deployed between different stations to reduce the transformation cost of seasonal heavy overload stations.
In response to the problem of three-phase imbalance of loads, the energy storage system monitors the voltage, current, power and other data of distribution transformers in real time, and controls the power of output phases by phases, so as to improve the pressure on the lines and power loss.
For the problem of low power factor caused by more inductive loads during the peak load period, the energy storage system controls the output reactive power compensation in real time according to the power factor of the distribution transformer, so as to achieve the effect of improving the power factor, increasing the load carrying capacity and reducing the voltage loss.
Mobile Energy Storage can simultaneously solve multiple power quality problems in the distribution area and set corresponding control strategies according to the actual situation.
For example, when there are low voltage problems caused by three-phase imbalance and low power factor in the station area, the converter can decouple active and reactive power outputs on the one hand, i.e., it can first output reactive power to boost part of the voltage, and then output active power to boost the voltage when it cannot boost the voltage only by outputting reactive power; on the other hand, it can control and adjust the outputs of one or two phases individually to make the three-phase loads balanced. On the other hand, adjusting the output of one or two phases individually makes the three-phase load balanced, which makes the management of power quality problems in the station area more efficient through comprehensive means.
The distribution transformer capacity of a rural area is 630kVA, and the actual load is 30%~ 50% of its capacity, but the heavy overload circuit breaker tripping of the distribution transformer occurs many times during the peak time of electricity consumption in winter evening, which has led to many customer complaints and brought more pressure to the operation and maintenance personnel.
At the same time, there is also a three-phase load imbalance problem in the area, exacerbating the risk of tripping the distribution transformer outgoing circuit breaker. The operation and maintenance personnel put forward the conventional transformation program and mobile energy storage system program to improve the power quality of the station area, and will be 2 kinds of program construction investment and governance effect of the comparison, the conventional transformation program and mobile energy storage system program comparison table as shown in Table 1.
Comparison Table of Conventional Retrofit and Mobile Energy Storage Solutions | ||
Comparison Project | Conventional retrofit programme | mobile energy storage system |
Construction content | Addition of 500 kVA box substation and upgrading of low voltage lines Approx. 200 m | Add 200 kW/400 kWhmobile energy storage |
Estimated Investment | Approx. 500,000 | Approx. 650,000 |
Construction period | 3 months | 5 days |
Access method | Power outage required to reconnect loads | Power-accessible stations |
Utilization rate | Equipment is fixed and cannot be redeployed | The station can be redeployed to other problematic stations after a drop in load |
Implementation effect | Completely solves overloading problems, but non-winter load factor is very low, asset utilization is low, and increases station line loss rate
| Rapid reduction of distribution substation load factor, short implementation period, asset recycling |
As shown in Table 1, although the first investment of mobile energy storage system is slightly higher than that of the conventional retrofit scheme, it can be deployed to multiple stations, and the Mobile energy storage cost is lower than that of the conventional retrofit scheme. At the same time, the mobile energy storage system has the advantages of short implementation period and can be connected with electricity. Through comparison, mobile energy storage system was selected for power quality management of the station area, and the construction personnel completed the site leveling, equipment lifting in place and access to the low-voltage main tap box in 5 days. 68% of the maximum load rate of the distribution transformer was put into operation after Mobile Energy Storage, and the three-phase load imbalance rate was significantly reduced, which improved the terminal voltage and reduced the line voltage. After Mobile Energy Storage was put into operation, the maximum load ratio of the distribution transformer was 68%, the three-phase load imbalance rate was significantly reduced, the terminal voltage was increased and line loss was reduced, which achieved the expected effect.
Choosing a pad-mounted transformer for mobile energy storage systems can offer several advantages, particularly in applications where space, safety, and accessibility are key considerations. Here’s why pad-mounted transformers are a favorable choice in this context:
Space Efficiency: Pad-mounted transformers have a compact design, making them well-suited for locations where space is limited. This is especially important for mobile energy storage applications where the entire system needs to be transportable and easy to deploy in various environments.
Safety and Security: These transformers are often encased in tamper-proof, locked metal cabinets. This design enhances safety, making them a suitable choice for public spaces or areas where unauthorized access needs to be prevented. This feature is particularly beneficial in mobile energy storage systems that might be deployed in diverse and potentially unsecured locations.
Aesthetics and Low Visual Impact: Pad-mounted transformers are often more aesthetically pleasing compared to other types of transformers. They can be painted and designed to blend with the environment, which is beneficial in urban or residential areas where a mobile energy storage system might be temporarily placed.
Ease of Installation and Maintenance: Pad-mounted transformers can be easier to install and maintain due to their accessibility at ground level. This can be crucial for mobile energy storage systems, which may require quick deployment and easy maintenance in the field.
Reduced Noise Levels: These transformers are generally quieter than other types, which is an important consideration in populated areas or for applications like film production, events, or residential applications where noise reduction is critical.
Durability and Weather Resistance: Pad-mounted transformers are built to withstand outdoor conditions, including various weather elements. This makes them durable and reliable for mobile energy storage applications that might be exposed to different environmental conditions.
Compatibility with Renewable Energy Sources: In the context of mobile energy storage, which often involves renewable energy sources like solar or wind, pad-mounted transformers can effectively handle the variable outputs from these sources, ensuring efficient energy conversion and distribution.
In summary, the choice of a pad-mounted transformer in a mobile energy storage system is influenced by factors like space efficiency, safety, aesthetics, ease of maintenance, noise reduction, durability, and compatibility with renewable energy sources. These features make them an attractive option for mobile applications where these factors are crucial.
Here’s an overview of notable mobile energy storage companies as of 2024, with a focus on their key contributions and capacities:
Moxion Power: This U.S.-based mobile energy storage company has specialized in mobile battery energy storage systems (BESS). They have provided eco-friendly and noise-free power solutions for events, art exhibits, and film sets. Moxion Power’s systems were notably employed by Amazon Studios for various film projects, emphasizing their effectiveness in indoor operations and noise reduction.
Nomad Transportable Power Systems (NOMAD): As a mobile energy storage company, NOMAD emerged from a joint venture between Northern Reliability Inc. (NRI) and KORE Power. They are focused on providing renewable energy-based mobile energy storage systems across various industries in the U.S., showcasing their versatility and commitment to sustainable energy solutions.
Power Edison: Power Edison is a prominent mobile energy storage company that has been developing renewable energy solutions. Their expertise includes land and marine-based BESS and Electric Vehicle (EV) charging infrastructure. With a substantial development and sales pipeline, Power Edison has established itself as a key player in the mobile energy storage sector.
EOS Energy Storage: EOS is a renowned U.S.-based mobile energy storage company, offering grid-scale energy storage solutions and commercial solutions for peak shaving and energy demand management. Their innovative zinc-based battery technology is scalable and has been a significant contribution to the mobile energy storage market.
Enapter: This German mobile energy storage company is recognized for its AEM electrolyzer, which produces hydrogen from water using renewable energy. Enapter’s technology is a promising solution for long-term and seasonal renewable energy storage, making them a critical player in the mobile energy storage industry.
LAVO: LAVO, an Australian mobile energy storage company, has developed an integrated hybrid hydrogen battery system connected to solar systems. This system offers a high storage capacity and long-term durability, illustrating LAVO’s innovative approach in the mobile energy storage field.
Allye: Specializing in mobile BESS solutions using EV batteries, Allye is a mobile energy storage company focused on both commercial and residential markets. Their approach to using EV batteries for energy storage is aimed at supporting the transition to cleaner, more affordable energy, positioning them as a forward-thinking entity in the mobile energy storage sector.
Each of these mobile energy storage companies brings unique strengths and innovations to the table, contributing significantly to the diversity and advancement of the industry. From battery-based systems to hydrogen energy storage, their efforts reflect a growing commitment to developing efficient and sustainable energy solutions.