Taking Green to the Grid

THE REGULATORS ARE COMING, AND THEY ARE GOING TO FORCE CHANGES IN OUR INDUSTRY. In the United States, more than 30 states now have renewable portfolio

THE REGULATORS ARE COMING, AND THEY ARE GOING TO FORCE CHANGES IN OUR INDUSTRY. In the United States, more than 30 states now have renewable portfolio standards — mandatory percentages of power that have to be produced and delivered from renewable sources by specific dates. In some cases, the requirements kick in as soon as 2010, in others, the first real requirement is in 2025.

To evaluate the impact of renewable sources on the electric grid, it helps to separate the renewables into several categories and address each category separately:

  • Schedulable central station generation (S-Cent). This includes biomass and other alternative fuels, and is so similar to conventional generation that it offers few or no issues in integration into the grid. Because it is simple to integrate, where appropriate, S-Cent should be considered as the first choice in deployment. A sample of the facilities that fit into this include large wood-fired power plants, garbage and post-consumer waste incinerators, landfill gas generation facilities, pumped hydro facilities and run-of-the-river current farms.

  • Variable central station generation (V-Cent). Wind farms are the best-known examples of this asset class. Large solar- and wave-power installations also fit into this category. Facilities run when the environment is right, not when they are needed. In most cases, these sources provide power 7% to 40% of the time, depending on the location and type of resource. Obviously, these systems require some level of other generation to provide support. As more and more of the generation becomes V-Cent, the ability of the operator to prevent a blackout will decrease and more of the grid may be at risk.

  • Schedulable distributed generation (S-Dist). Normally, these generation facilities will be found on farms, in businesses and in homes. Another good example would be wood-fired combined heat and power generation. Schedulable distributed generation is connected to the distribution network. Because it can be scheduled, it offers the ability to provide highly distributed power close to where the customers consume it. Changing the grid to support S-Dist means changing the relaying and the protective devices installed in the grid to allow power to flow backwards (on the grid). S-Dist devices typically generate single-phase power, so a utility can experience large phase imbalances and see big differences in voltage on a phase-to-phase basis.

  • Variable distributed generation (V-Dist). This is the category that most environmentalists mean when they discuss the next generation of the electric network. These are solar- and wind-powered devices that are owned by business owners and homeowners. Because they are deployed in the low-voltage network, they are likely to cause issues with harmonics and with phase imbalance. To put larger numbers of V-Dist units in the rural areas and move the power to people who will use it may involve reconductoring, which is not an inexpensive undertaking.

Renewable generation is an important part of the future for the electric industry. We cannot avoid it and we cannot hide from it. We have to work through these problems and make integration of renewable easy. IEEE-1547 provided the basic interface for renewables to the grid, so the interconnection — the largest stumbling block a decade ago — has been solved. Some of the issues can be solved with planning. Relaying and protection schemes can be redesigned, and the new standard can be deployed as circuits are maintained or built.

Dealing with variability is tough. The choices are ancillary services, demand response or storage. To date, we have few good answers for storage. Harmonics, reactive power and power quality are harder problems. Capacitor banks are helpful in managing reactive power, but typically they do not exist out in the distribution network, and the sensors and controls to use them effectively do not exist. With the exception of storage, the good news is that nothing new needs to be invented, only improved and deployed.

Fuel price swings and the move to carbon markets will tend to accelerate the move to renewable energy sources. The new energy team under President Obama also will accelerate this move in the United States and that will have an impact on the rest of the world. Regulators, customers, utilities, manufacturers and independent power producers will all have to work together to make this work. For more than 100 years, we have been improving, perfecting and investing in the existing electric grid. One estimate for transmission alone indicates that the United States would have to spend more than US$900 billion to support a plan like the Pickens Plan. Globally, it would amount to trillions of dollars.

We have a long way to go, but knowing the issues we will encounter along the way and planning for them in advance will make the journey more likely to succeed. This is a journey that we need to take, so let us proceed in a fashion that provides the highest possible chance to succeed.

Doug Houseman ([email protected]) is associate director with Capgemini and facilitates the Smart Energy Alliance.

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