Microgrids: Promoting Local Production for Local Consumption of Renewable Energy
Supporting the Transition away from Fossil Fuels with the Power of Electronic Components
03 Sep, 2024. 6 min read
This article was first published on
article.murata.comThe effective utilization of renewable energies such as solar and wind power is an essential element to achieve carbon neutrality. According to the Statistical Review of World Energy 2023 report published by the Energy Institute in the U.K., renewable energies including hydropower already account for approximately 30% of the world's power supplies. The total amount of that renewable energy is 8,539 TWh. This means it has grown more than four times the 2,058 TWh that it was in 1985.
When it comes to ways to fully utilize renewable energy, many people may think of large-scale power generation in places brimming with natural energy. Examples of that include solar power generation in vast places like deserts or grasslands and wind power generation on the sea. However, there are forms of renewable energy even in the middle of any big city. In fact, efforts are being proactively promoted to introduce power generation with renewable energy in urban areas. In Japan, for instance, solar panels are being installed on the rooftops of buildings and the roofs of houses. The amount of power these solar panels generate is small. This means they are being positioned as auxiliary power supplies. Nevertheless, they are being effectively utilized. Moreover, new efforts are underway to also develop and introduce solar power generation technologies on the walls and in the windows of buildings and technologies that generate power using the vibrations that come from people walking.
Looking at the situation from a global perspective, many small and medium-sized cities are striving to achieve local production for local consumption in which the power consumed locally is supplied by utilizing wind power, solar power, hydropower, and other forms of renewable energy in that locality. Furthermore, an increasing number of companies are also participating in RE100. RE100 is an international initiative the aim of which is for companies to supply the power they use in their businesses with 100% renewable energy. These companies are proactively introducing power generation equipment into their factories and other facilities to generate as much power as possible on their own (Fig. 1).
Microgrids: Supporting the Local Production for Local Consumption of Renewable Energy
We can call efforts to achieve local production for local consumption by converting renewable energy into power an extremely effective means of utilizing energy. This is because it is possible to minimize the power loss that always occurs in power systems during the transmission and distribution of that power.
Large-scale power plants are located far from cities where a large amount of power is consumed in current power systems. The power generated in those power plants is transmitted and distributed to the areas where it is consumed to be utilized in daily life and socio-economic activities. However, approximately 30% of the power generated in the power plants is wastefully lost in the process up to its use via the power transmission and distribution network (also known as the grid). This is because a large amount of power is dissipated as heat or electromagnetic waves due to power lines and power converter loads. The shorter the distance of power transmission and distribution, the fewer times the power is converted, making it possible to reduce power loss. Therefore, we can minimize the occurrence of power loss by achieving local production for local consumption using the natural energy all around us as a distributed power supply.
*This linked page is in Japanese.
A small-scale power network aiming to achieve local production for local consumption of power is called a microgrid (Fig. 2). In addition to effectively utilizing renewable energy, microgrids have other benefits, as they are distributed power systems. For example, microgrids are capable of stably supplying power to communities even in the event of a large-scale power outage during an emergency such as a disaster. This allows us to maintain our daily life and business activities.
Major Prerequisite of Operating Power Systems: Balancing Principle
The concept of microgrids is simple. However, realizing microgrids is not that easy. This is because there is a major principle to the building and operating of power systems called the "balancing principle."
The balancing principle is the rule that the amount of power supplied from a power plant must always match the amount of demand for power no matter what the power system. If we operate a power system in violation of this principle, the voltage of the power will become unstable and the equipment may fail, leading to a large-scale power outage.
However, power derived from renewable energy like solar power is produced from unstable natural phenomena. Accordingly, we cannot conveniently adjust the amount of power generated. Therefore, it is difficult to supply the power we use and to fully use it with only power generated in the community. This means it is necessary to employ a mechanism that accommodates for surpluses and deficiencies with advanced operation and management like the fine adjustment of the balance in supply and demand in the community or the utilization of a large energy storage system (ESS).
Smart Grids: Major Prerequisite for the Realization of Microgrids
The means to solving this issue is a very similar concept to the microgrid called a "smart grid." A smart grid is a mechanism that automatically controls the necessary power so it can be supplied without surpluses or deficiencies by utilizing smart meters and other telecommunications devices to visualize in real time power demand in each individual household, business establishment, or other facility.
Microgrids and smart grids are different concepts. Nevertheless, it is difficult to realize a microgrid that achieves local production for local consumption of power efficiently and effectively without introducing a smart grid mechanism. Smart grids grasp in real time and in detail the amount of power generated in distributed renewable energy power generation facilities and the amount of power consumed in daily life and business to achieve a balance between both while managing the charging and discharging of multiple distributed ESSs. If there is a deficiency in the power generated with just the charging and discharging permissible values of the installed ESSs, smart grids procure and release power from the wider grid to preserve the balance.
The technology that uses IoT technology to control the amount of power supplied as if the multiple pieces of power generation equipment and ESSs in a microgrid were one power plant is called a "virtual power plant (VPP)." Meanwhile, smart meters are used to grasp in real time the power consumption situation in households and business establishments. Looking at the situation globally, smart meters are rapidly spreading. Smart meters began to be installed in households in 2014 in the greater Tokyo Metropolitan area in Japan. Installation was completed in almost all households and business establishments by the end of FY2020. The installation of smart meters across Japan is scheduled to be completed by the end of FY2024. In other words, we can say that the groundwork to promote the building of microgrids is steadily being laid.
DC Power Transmission and Distribution Systems Aiming for Further Improvements in Efficiency
Attempts are also being advanced to further raise the energy utilization rate with microgrids. Currently, technological development is underway to introduce a new power transmission and distribution network called a "DC microgrid." This DC microgrid will transmit and distribute DC power instead of the AC power used for commercial power supplies.
DC power supplies such as solar batteries and storage batteries are often used on the power supply side of microgrids. On the other hand, looking at the power consumption side, telecommunications devices made using semiconductors and electronic components and energy-saving electronic goods made using inverters operate on DC power. This means both sides handle DC power.
Currently, however, AC power is being transmitted and distributed, so it is necessary to convert the power both when it is transmitted and when it is used. Power loss occurs at that time. DC microgrids are a technology aiming to minimize this waste. It is envisioned that DC buses of about 400 V will be laid in place of conventional AC 200 V / 100 V power lines and that high-voltage commercial grids will operate by being connected via a bidirectional AC/DC converter. In addition to microgrids, DC power transmission systems are being used to transmit power over long distances. There are already examples of this technology being put to practical use in Europe and America.
The building and operation of microgrids will no doubt progress at the same time as there is an expansion in the usage settings of renewable energy. It is expected that demand will further increase for even more highly efficient and flexible microgrids that can handle various usage settings and the electronic components that support the building of those microgrids.