So far we have introduced smart grids which connect IT to existing power systems in order to manage the production, transmission, distribution, and consumption of electricity. In this posting, we will have a look at microgrids.
A microgrid is similar to a smart grid in that it also combines IT to a power system to control production and predicts the amount of generation and consumption. The difference is that microgrids are much smaller in scale compared to smart grids, and they don’t require any transmission equipment as the consumer’s very close to the generator.
Then let’s take a look at what a microgrid is, and what kind of effects we can expect by adopting one.
The U.S. Department of Energy (DOE) defines microgrid as follows.
A microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid.
In other words, a microgrid is a localized power system which connects consumers with distributed energy resources (DER) such as wind and solar power. It operates independent from the entire power system (off-grid) for self-sufficiency, but it can also work with the system (on-grid) when necessary.
Simply connecting the consumer to DER, however, is not enough to create and run a microgrid. This is because generation easily changes in wind or solar power systems depending on the wind velocity and sunlight. When these generators are connected to a power supply system without additional controllers, the quality of electricity can be very difficult to predict and manage.
Microgrids are especially affected by this unstable electricity quality from renewable energy generation as the size of the network is much smaller. This is why microgrids require technology that can prevent these problems. Most microgrids also include an energy storage system (ESS) in order to secure stability in both the quality and supply of electricity.
ESS stores power when there is a surplus of power and then sends it to the consumer when the demand increases in order to maintain the stability of quality and supply.
Another thing necessary is a system which monitors and controls the consumer and DER connected to the microgrid as well as ESS. These systems help keep the supply stable by controlling the generator and consumer according to the microgrid’s condition.
It also helps enhance energy efficiency and creates added value by predicting supply and demand while enabling additional services such as peak cut, load shift, and demand response.
Each country has a different context for the emergence and utility of microgrids.
In U.S.A., microgrids were adopted for system stability and efficiency at campuses or for military reason.
On the other hand, they are mostly used to ensure a better use of renewable energy and environment in Europe and Japan, where microgrids tend to be adopted for local communities as an alternative energy source. Japan started using microgrids as a safety net for natural disasters like earthquakes which commonly cause blackouts. ESS can be loaded into a car as a DER in this case.
China uses microgrids to supply power to remote regions which have a hard time getting power transmissions and distribution facilities. This is also the most common use of microgrids in Korea, besides those being used for university campuses.
One of the great things about microgrids shared by these various cases is that they neither require expenses for electricity transmission facilities nor do they waste any energy during transmission, as most power produced through microgrids is used in the nearby region.
Microgrids can be divided into different types: residential, commercial for small businesses, and commercial for larger businesses according to the amount of electricity they handle. They can be categorized into military, campus, and community microgrids as well, depending on their purpose. Lastly they’re classified into connected and separated microgrids according to their operational mode.
The U.S. Department of Energy also defined the ownership models of microgrids as the following.
Utility model: distribution utility owns microgid and supplies electricity to lower cost.
Landlord model: landlord owns microgrid and supplies electricity and heating to the tenants through a contract.
Co-op model: multiple individuals and companies construct and manage microgrid and are then supplied with electricity from it
Customer-generator model: an individual or a company owns and manages microgrid and supplies electricity to oneself or neighbors.
District heating model: an independent company owns and manages micrigrid and sells electricity and heating service to consumers.
One of the great examples of microgrid application in Korea is the solar power microgrid in Tae-an, which is planned to be constructed in several islands such as Geomundo, Jodo and Ulleungdo with other various services. Let’s take a look at some of these cases.
Tae-an solar power plant installed 69,712 solar modules on top of the 295,166m2 (about 73 ac) to produce 13.77MW. It produces 52MWh (3.8 hours) daily and 1,600MWh monthly.
Tae-an solar power plant used to pay for on-site power (the power used to run the plant and manage equipment) use. Additional plant facilities and ESS were adopted to supply the on-site power so that the plant can be operated independently.
They also used ESS to save energy and be prepared for the day/night time peaks. Energy management system (EMS) was also introduced to manage the optimal operation mode according to the generation, load, and rate.
The Ullengdo microgrid is planned to be built as an independent microgrid with more various services. Ulleungdo Island has a population of 10,672 on 72.9km2 of land, and over 400,000 travelers visit each year. The island is currently relying on diesel generators totaling 18.5MW (one for 10.5MW and another for 8MW), and some also use small hydro and solar power generators.
Right now, Ulleungdo pays about 15 cents per kilowatt to supply the power but sells it at 13 cents. This means they are losing about $ 23 million every year due to the excess cost for generation.
The goal for LG CNS is to build a microgrid operation center as well as a 20MWh ESS, 8MW wind power plant, and 1MW solar power plant on Ulleungdo Island by 2017, which are expected to cover about 30% of the entire energy expenditure of the island.
They are also planning to create a self-energy-sufficient island by adopting ESS, fuel cells, geothermal generation, smart meters, and electric cars by 2021. The island will be able to remove inefficiency while reducing carbon emissions.
A monitoring system that can read the status of microgrids is necessary in order to have DER and consumers within a microgrid working together according to the energy status. A monitoring and control system which controls the resources according to the situation is also crucial for this.
EMS which not only monitors and controls the system, but also predicts the supply and creates/applies the optimal algorithm will make the microgrid even more efficient and stable. This EMS is being placed on Ulleundo Island, and its main function is to predict generation and load for the best generation plan then to control generation automatically.
The three key software factors of EMS for microgrids are data reliability, forecast accuracy, and data visibility. Each can be defined as follows.
Data reliability: once data collected from the microgrid is distorted while being transmitted to EMS, EMS detects it and makes modifications to secure reliability. Higher data reliability results in a more precise operational record for the microgrid administrator. Collected data helps make accurate generation and demand forecasting.
Forecast accuracy: various algorithms for analysis can be applied to enhance forecast accuracy. Higher forecast accuracy enhances energy efficiency, and in turn results in more economic microgrid operation
Data visibility: Operation can become much easier when the information about generation and demand as well as unexpected errors in microgrids is all visible. Visible data also helps improve energy efficiency by showing where the energy is being wasted.
As mentioned earlier, monitoring and controlling various DERs such as wind/solar power and consumers is a crucial factor for microgrids. This is because forecasting generation and consumption, establishing an operation plan, and controlling according to schedule using EMS makes the system much more efficient compared to simple methods which only control and monitor the system. With this, microgrids can be operated in a much more stable manner.
Choosing the best EMS which secures the highest data reliability and visibility as well as forecast accuracy is especially important in maximizing these functions.
LG CNS Smart Green Solution (SGS) stands out in this sense for its verified control and monitor functions based on the Smart Green Platform (SGP). The system can be implemented without individual development, and it also provides the EMS service based on SGP.
SGS not only forecasts electricity consumption and generation, but also improves its forecast and reporting accuracy by verifying and analyzing the data.
Today, we had a chance to cover LG CNS SGS and SGP that are being used in various fields. I believe there will be more diverse service fields based on SGS and SGP which control and monitor various devices with simple setting adjustments.
I look forward to seeing SGS and SGP in more various fields in the near future.
Written by Dong-young Shin, analyst at LG CNS Smart Green Solution R&D Center
Links for previous article series
(1) B2B Software Leading New Enterprises
(2) Industry 4.0, the Fourth Industrial Revolution with IT and the Manufacturing Industry
(3) Smart Green Platform, Connect and Combine for New Value
(4) How to Enhance Energy Efficiency through Software
(5) EMS for Efficient Energy Use