As I discussed last month, one of the most complicated problems electrical utilities face is integrating alternative-energy sources into the traditional grid. In addition to the traditional large electrical generation sources—fossil fuels, hydroelectric and nuclear—utilities must now deal with large numbers of smaller sources of power.
Alternative-energy sources vary from a few kilowatts from residential solar-power systems to megawatts (MW) from commercial solar stations and wind farms. Alternative energy contributions are not trivial. Parts of the Midwest and Southwest get up to 20 percent of their power from wind. California is home to the largest geothermal, wind, solar thermal and solar photovoltaic (PV) power plants in the world, getting more than 25 percent of its electrical power from alternative-energy sources. However, such diverse energy sources create new network management problems.
Utilities began using fiber optics for managing their grid as long as 30 years ago. Early systems used sensors (some made with fiber optics) to measure grid current and voltage, control distribution relays and provide the data needed to make the grid more efficient. Newer fiber systems expand the monitoring and control, some right to the customer’s meter, along with offering new services such as broadband internet over fiber to the home.
Alternative energy refers to solar and wind primarily, although there also are some geothermal systems. Solar and wind create a problem for utilities because their outputs are not easily dependable. PV systems create electricity when the sun shines; wind farms create electricity when the wind blows. Even the amounts of electricity created vary, depending on to how much the sun shines, how much the wind blows and how efficiently the systems are managed.
To maximize efficiency, solar-power systems often follow the sun; PV panels move as the sun crosses the sky. Geothermal systems such as the 480-MW facility at Ivanpah, Calif., have mirrors that follow the sun to keep it focused on the generation towers. Ivanpah has 360,000 of these mirrors connected to 13,000 fiber optic cables installed by workers from IBEW Local No. 357 of southern Nevada.
The solar-thermal (steam) generation systems such as Ivanpah use the sun to create steam to run turbines, so some storage of superheated water enables the period of electrical output to be extended beyond the peak solar hours.
Wind-power systems are perhaps even more complicated to manage. They need to be aimed into the wind, and blades must be set to maximize output or feathered when power is not needed. In addition, the output must be synchronized with the grid. Basically, every tower is connected using fiber to provide the controls needed to efficiently manage its output.
The goal has been to even out the power produced by solar and wind systems using storage methods that are reliable and cost-effective. There is certainly no lack of ideas.
The best solution
The reality is that storing energy in batteries seems the best solution. Battery research and development has been a big part of the development of electric vehicles, and pioneers in that market, such as Tesla, are also focusing on battery storage for solar and wind systems (see page 38).
Early experiments in battery storage were problematic. Lead-acid batteries had short lifetimes when subjected to the high demands of grid storage. Several early projects ended with fires. However, the engineering being done on lithium-ion batteries used in many consumer electronics devices and electric and hybrid vehicles seem capable of withstanding the demands of grid storage when properly managed.
In Southern California, several large battery facilities are coming online right now. San Diego Gas & Electric is building the largest power-storage facility in the world in Escondido, Calif. This facility will have 19,000 battery modules spread out over 24 trailers with enough electrical storage to power 20,000 homes for more than four hours.
It’s complicated to manage all these new storage systems. With more sources of power—some with timing issues—grid management becomes difficult. Utilities are expanding fiber optic communications networks, leasing dark fibers and using wireless communications of all types to create complex networks capable of providing the monitoring and control of their grids.
The focus of grid management is getting more localized. For better management and higher reliability, utilities are now looking to microgrids, some not bigger than a few square blocks, that can be managed with the complex fiber optic networks they operate.