Development of a Smart Grid Roadmap for High Voltage Long Distance AC/DC System with High Penetration of Renewable Energy

By Fred Fletcher and Robert Schulte

What if the Bulk Electric System (BES) was repurposed, so that it could be best used to collect renewable energy over the entire continent or potentially the world and deliver such energy to Independent System Operators (ISOs) or other large regional power system operators? Developing a network to span the entire continent is a recognized approach to infrastructure architecture. The Interstate Highway System, the Internet, and natural gas pipelines span the continents and make modern society practical. These continental networks were established based on specific economic objectives and purposeful standards and methods.

The intermittent nature of wind and the diurnal cycle of solar do not align well with the customers’ need for electricity. Studies have shown that over a very large area there is high assurance of the availability of electricity produced by wind and solar. The Mid Continent Independent System Operator has found that such geographic diversity can improve the reliability of wind. These observations have given rise to the following questions. How might such energy be most economically collected and transmitted to the various ISOs located 2000 miles apart? How large is the area needed and what value might storage have in making such renewable energy dependable? Who might be interested in building such facilities? It was these questions that Power from the Prairie, a company formed for the purpose of conducting business and technical studies and plans to aid in the development of wind energy in the North Central United States, considered in defining the studies needed in order to best unleash the vast wind and solar resources available across the continent.

The Department of Energy is currently conducting studies that consider the technical and production cost of a national or continental sized DC power grid. The studies are expected to show that such a grid is feasible both technically and financially.

Ten years ago Distributed Energy Resources looked both technically and financially feasible. As a result, IEEE and other technical entities developed standards and Roadmaps for Distributed Energy Resources. These standards defined the operations and requirements for an agreed-upon approach. As a result, Distributed Energy Resources have become a viable source of energy. With the economics and need for a power grid of the scale of the Interstate Highway System and even the Internet soon to be better understood it is time to define the next set of Standards as well as the Roadmap for such a network. Such efforts will define new players to build and operate the elements of this new network. Without such a Roadmap developers of large transmission or renewable energy projects will find developing a profitable business case difficult or impossible.

Power from the Prairie was formed to consider the practical ramifications of such a large system and conduct power cost studies. We have begun to understand the limitation of the current model and, like others, see the need for roles that go beyond the typical utility service area and show the vitality of such a new approach and its new players. One interesting approach considered in the initial view of such a large system is the concept of “Electronic Generators” that would be located to best feed power into the existing power grid and then fuel these generators with a large DC power grid that would be as large in geographic scope as the current natural gas pipeline system.

Across any continent there are many regions where low-cost solar and wind electricity can be best developed. There are sites where geologic energy storage can be developed. Geologic energy storage includes Pumped Hydro Storage and Compressed Air Energy Storage. These two methods of storage are cost effective today and can be built to the scale required of a large power grid. A Bulk Electric System Road Map could use such energy storage to make wind and solar across the entire continent plentiful, reliable, and economic.

But the challenges of supporting such a large market may best be done by allowing each of the Independent System Operators to maintain its current practices and markets rather than attempting to merge them into one. Current markets and regulatory structures as well as governmental policies must be complimented, in order for the acceptance of such an approach. This proposed model basically replicates the current natural gas pipeline with high capacity DC transmission operated as an intelligent network. Such a DC smart network would provide energy from regional energy collector transmission systems, much like collector pipelines collect natural gas from natural gas production facilities and deliver such natural gas to the pipeline.

The major components of this Smart Grid Road Map for the Bulk Electric System would be the following:

Electronic Generator;DC to AC converters that acts as a generator in a specific ISO

DC Grid Interconnection;AC to DC converter that moves electricity from ISO to DC Grid

DC Grid;a multi node DC mesh network

Renewable Electricity Collector;an electric transmission system that is specifically operated to collect renewable electricity

DC Grid Storage;A grid level electricity storage facility

Electricity Scheduling and Renewable Energy Accounting;a system for the scheduling and dispatching of both DC power within the DC Grid and AC power into and out of the DC Grid

It is time that we begin the process of considering such a large network and how such a network can be used to allow renewable energy to be economically harvested and put it to work where it can be used.

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