Modeling Electric Microgrids
For Megacity citizens, energy supply is a constant worry. In the largest megacity in the world, Tokyo, companies and households are required to save energy in the wake of the Fukushima Daiichi disaster. Local microgrids are being discussed as a solution, according to the principle "local production for local consumption". Producing your own energy is relatively easy, but what do you do if you produce more - or less - energy than what you need?
The highest priority among Megacity challenges for their citizens, however, is transportation. Environment and emissions is another priority. Using electric cars minimizes the pollution, but they connect your transportation with the energy supply in a new way. When you have an electric car and solar cells on your roof - like most new houses in Japan - you are pretty independent of the electric utility, at least during the daytime.
But there are several cases which have not been possible before, that now become concerns. What happens when you want to give your neighbor electricity? And how do you handle it when an appliance manufacturer wants to give you credit for the electricity you use?
These and other business models have been studied in a project Ericsson Japan has sponsored at Tokyo University.
Traditionally, electric energy is routed along paths of least resistance. This works fine when the electricity is produced by large facilities and is distributed through massive grids, and electric consumption is predictable, so the generation facilities can be controlled accordingly. But in microgrids, the production is not as easy to control.
In the Tokyo University model of the electric grid, the way electric production and consuming appliances are addressed and the description of their properties are linked. This means you can specify if you want to get your energy from renewable sources or from the general grid. Since you can specify the properties you want on a very detailed level, you can decide if you want, for instance, Electrolux to pay when you use the vacuum cleaner. While vacuum cleaners can not yet report their energy consumption, it can be done through gateways that can sense which devices are used. Other devices, in particular solar energy production systems and electric cars, are able to report when they produce or consume energy.
If the energy supply from the renewable sources fails, for instance, because a cloud moves in front of the sun, the energy supply is re-routed to an energy supply which has energy to spare. The charging information for the electric microgrid can also be routed separately, so the information about who is supposed to pay for the energy, and how much, can be forwarded to the server managing the billing.
The electricity supply will find the nearest energy source that suits the requirements of the user, and requests energy from there. Alternatively, the energy consuming device can stop automatically. Delivery is switched automatically.
Ericsson has extensive collaborations with several universities, Tokyo University among them. University collaborations are an important piece in the research activities at Ericsson, providing us with fresh insights into relevant problems, like the current prototype.
As part of the project, we created a model of a microgrid system that has let us model these new business models on a grand scale, to verify their robustness. Tokyo University has also built a small demonstrator, where you can see how the electricity consumption is balanced when, for instance, a cloud covers the sun.
The next step is to include electric vehicles in the model. In Japan, all electric and hybrid cars can be charged from the grid and provide electricity into it. Since they can serve both as electric consumers and suppliers, and can appear and disappear in different places, the traditional demand and response models will not work. In particular, cars will have more energy than they need, and could sell it to the grid at times. On the other hand, if you could balance the demand for energy with the production and storage, renewable energy might be sufficient, and polluting energy sources can be closed.
Would you let someone else use your car as a battery, if that meant the electricity provider was able to close coal-burning power plants?