Building a Continental Renewable Super Grid
By Roy Morrison | May 28, 2009
As the planet warms and the economy cools, renewable resources are emerging as a realistic means to solve both problems in a timely fashion. Advocates of renewable energy want trillions of dollars spent in the coming decades on a continental-scale smart grid that will slash global greenhouse gas emissions and turn society toward a prosperous and ecological future.
How can we build such a grid? What are the next steps? Are we trapped in a future of false promises on clean coal, more nuclear proliferation, resource wars for oil, rising pollution, and business as usual?
The wind doesn't blow constantly and the sun doesn't always shine. Aren't renewables, by their sporadic nature, limited to contribute 20 percent of grid power in a system mainly reliant on coal and nuclear plants for baseload power?
Fortunately not. A hard-nosed, scientific design for a complex and responsive continental renewable resource grid is emerging from behind the coal and nuclear cooling towers. Prospects are moving from rudimentary calculations to data-driven models and computer simulations.
German scientist Gregor Czisch modeled such a super grid for Europe [PDF 2.15MB]. He and I are currently co-developing a proposal for modeling a North American super grid.
In late April 2009, Jon Wellinghoff, Chair of the Federal Energy Regulatory Commission (FERC), said that renewables in a properly designed smart grid can meet our energy needs. He stated that new coal and nuclear plants may be a thing of the past. "We may not need any ever," he told a U.S. Energy Association Forum. The transformation from baseload power plants that pollute to a renewable future will be similar to the rise of distributed computing networks to replace a world of mainframe computers.
Principles and Prospects for a Renewable Super Grid
The current grid is based on hundreds of large, central, fossil fuel and nuclear generators, with a substantial contribution from large-scale hydroelectric and some emerging wind, solar, geothermal, and other renewable power sources. This system relies on regionally based central control and one-way communication with limited long-distance alternating current (AC) transmission interconnection. The regional AC transmission backbone feeds local distribution nodes with limited local generation and storage.
A sustainable super grid system would be based on tens of thousands of renewable energy generators of various types on a continental scale with appropriate storage resources. A high-voltage direct current (HVDC) transmission backbone would link these generators to bring energy from sources to sinks on a continuous basis. The scale of a continental renewable grid using HVDC allows it to be inherently more self-managing than regional grids with more limited power and storage resources. When the wind is not blowing in the east, for example, it may be blowing in the west or the north. Continental scale can take advantage of a variety of storage resources, such as storage hydro and pumped-storage hydro, compressed air, batteries, and flywheels.
System resources are integrated with many millions of locally distributed renewable generators, cogenerators, and storage systems within local power nodes that both reduce demand on the continental system and greatly improve system reliability and responsiveness. These distributed resources include, but are not limited to, rooftop photovoltaics (PV), basement and block cogeneration systems to replace furnaces and boilers, district heating and cooling systems, ground-source and water-source heat pumps, fuel cells, storage batteries, electric car batteries, and flywheels.
The smart grid system combines central and local control with two-way information flows that allow energy users and distributed generators to respond very quickly to price and load signals to help balance the system. Spot price signals, detected at shorter and shorter intervals, are a good proxy for system state. Current Automatic Generation Control (AGC) signals, calling for major power plant response within 2 seconds to balance the system, can become a common standard for distributed smart grid response.
As load increases, prices rise, to which your programmable local control responds by reducing load by duty cycling, deferring non-essential tasks, using storage, or increasing generation. As load and price decreases, local control may increase usage, decrease generation, or fill storage. Complete price signals sent to end users can include location-specific pricing right to the transformer feeding your house, sending price signals that encompass costs for local distribution line loads. As an alternative path for distributed control, a smart grid can use local detection of small electric system frequency variations to keep the system in balance from the bottom to the top and make issues such as AGC an artifact of the past.
Quick price response of user devices is not unrealistic. My associate Pentti Aalto has produced a working prototype of a load controller scraping 5-minute ISO-NE price signals from the web, and using a satellite pager network system to transmit changes in price to a local computer controller that can record energy use and price as well as operate several end-use devices.
In sum, a renewable super grid will:
- Be continental in scale,
- Use HVDC transmission for long-distance power flows,
- Integrate system and distributed power resources and storage,
- Meet all power needs reliably year round,
- Be responsive,
- Be substantially self-regulating and self-healing and protect against common mode failure,
- Be adaptable to technological changes, and
- Maintain a dynamic and evolving balance between system and distributed power resources and storage.
Sophisticated modeling and computer simulations are crucial to designing such a renewable grid. We need good data. We need a thorough understanding of current energy use, by node, across the continent on a continuous basis using the shortest time intervals available. We need an understanding of current power plant resources and performance, data on current transmission resources and power flows, data on potential renewable resources and their performance based on comprehensive weather and geotechnical data, access to necessary storage to balance the system, infrastructure for future DC transmission and power flow paths, the ability to integrate this system with increasing distributed generation and storage resources, and future options for interconnection with neighboring continental grid systems.
The working model needs to include optimization of the cost of the system and the price of power; needed changes in regulatory framework, such as proper incentives for distribution utilities and ways to facilitate HVDC construction with proper regional and local participation; potential investment tools to facilitate entrepreneurial and user participation such as use of renewable energy hedges by developers and end users that give users reasonable long-term energy costs and developers long-term reasonable income streams, such as the 15-year wind hedge negotiated between Southern New Hampshire University and PPM Energy. Such hedge arrangements can be used, as well, between HVDC power line builders and energy users to facilitate financing and construction.
The technical and business challenges of planning and constructing a twenty-first century renewable grid system are substantial but not insurmountable. The greatest challenge at the moment is perhaps a crisis of the imagination.
There is clear self-interest in the status quo by the mega-polluters and those who profit from business as usual. What should also be clear is that we are on a path toward self-destruction. We have to bring to the table a clear-eyed understanding that the current path is radically unsustainable. If scientists such as James Hansen are right, we may have limited time before we pass a point where we can no longer merely turn down the thermostat by reducing carbon emissions. Instead of despair or false hopes from clean coal and more nukes, we can embrace the prospects and enormous benefits—economically, ecologically, and socially—of building the renewable super grid.
The super grid can be the key to the successful pursuit of sustainability. It is not all that we must do. But it is a necessary step in evolving from self-destructive industrialism to a twenty-first century ecological civilization.
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