Triple hybrid stand–alone power generation system
Mitsubishi Heavy Industries, Ltd.
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Outline
Renewable energy power stations such as solar power plants and wind turbine generators are not suitable as stand-alone power plants in off-grid areas because their output is unstable and unreliable due to changes in the weather. As a solution to this problem, MHI Group developed a triple hybrid power generation system called “EBLOX” and constructed a demonstration facility on the premises of the Sagamihara Machinery Works (Figure 1) in our Group company. EBLOX is a combined power generation system that can use renewable energy sources such as solar power and is equipped with an energy storage system (ESS) and engine generator. We are promoting the use of EBLOX in off-grid areas where diesel engine generators are still the primary power generation system. EBLOX makes the most of renewable energy and results in a substantial reduction in carbon emissions.
Description
The EBLOX demonstration facility in the Sagamihara Machinery Works incorporates our engine generator set with a self-made 500kW GS6R2 gas engine and 1152 photovoltaic (PV) panels laid out on the rooftop of the Factory Building, which gives it a total output of 300 kW, a battery-based ESS with an output of 500 kW, and an energy storage capacity of 331kWh (Figure 2).
A power supply from a stand-alone power system means that the supply of electric power is to loads (something that consumes electric power) that are located in areas where a public utility is not available (off-grid areas). For EBLOX that utilizes three different power sources with a stand-alone system, it is crucial to control the output from each source in the most optimized way. Figure 3 depicts the EBLOX schematic and the control system COORDY. COORDY was developed with the most sophisticated technologies and is characterized by the following two features;
Feature 1: Optimal control of multiple power sources from a stand-alone power system.
To reduce CO2 emissions to the maximum from a hybrid power generation system in stand-alone operation, it is indispensable to assign the power outputs for 3 electrical sources optimally and to utilize solar power as much as possible during the day. To achieve this, COORDY is programmed to minimize the operation of the engine generator. In the case that clouds block the sun and decrease the output from the PV system, it can start the power supply from the ESS and increase the output from the engine generator as appropriate to instantly compensate for the drop in the output.
Feature 2: Capability to stabilize the local grid
If a local grid is connected to a public grid, the public grid keeps the frequency and voltage of the local grid constant by absorbing the fluctuations caused by a large increase or decrease in the output from a PV system. On the other hand, in a stand-alone power supply system that is not connected to a public grid, fluctuations in the output from the renewable energy system such as PV system directly affect the frequency and voltage of the local grid as they are not absorbed by the public grid, resulting in paralleling off of the power system itself from the local grid (opens the circuit and stops the power supply). To avoid this, COORDY can stabilize the local grid by immediately commanding the ESS to charge or discharge when the frequency or voltage of the local grid fluctuates. This new function is made possible by combining the Virtual Synchronous Generator from the our Group’s Research & Innovation Center with our droop control technologies and technology for coordinating the different types of motors that were acquired through many years of engine generator development.
Our advantages to apply triple hybrid power generation system in off-grid areas are as follows.
Generally, when using solar power with an engine generator in a stand-alone power supply system, the engine generator must compensate for the fluctuations in the output of the PV system, which generally limits the maximum capacity of the PV system to only 20% of the rated capacity of the engine generator. However, with the EBLOX system and COORDY control, a PV system with a capacity equivalent to that of the engine generator can be introduced, which allows the stand-alone power supply system to make full use of the advantages of solar power. Using the demonstration facility, we had verified that the output from the PV system is in fact equivalent to the output from the engine generator, making the most of renewable energy in a hybrid stand-alone system.
Furthermore, making realistic proposals to potential customers to introduce EBLOX in off-grid areas is now possible by simulating the stand-alone operation at each site at the expected power demand.
In the near future, the electrification rate in off-grid areas in Africa, Southeast Asia and other newly industrialized regions will greatly increase, which will cause an increase in carbon emissions. It is MHI Group’s mission with EBLOX to reduce the carbon footprint by encouraging the use of renewable energy sources in off-grid areas.
Partner(s)
Mitsubishi Heavy Industries, Engine & Turbocharger, Ltd
Supplementary information
News release
http://www.mhiet.co.jp/en/news/20190624.html
Video of EBLOX
https://www.youtube.com/watch?v=JODYrTGmI90&feature=youtu.be
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