Problems with the Grid

Overview

The existing grid has a number of problems, among them:

  1. The wide area grid is susceptible to cascading failures - The energy grid has been developed with extensive interconnections and grids often spanning continents.  The purpose of this interconnection is to improve reliability through redundancy, yet in fact increases the risk of wide area failures because any imbalance can be propagated quickly over an ever widening area.
  2. Grid stability cannot be maintained with >30% penetration of renewables – Although many regions are mandating 20-30% of renewable energy, many experts believe that voltage/frequency stability cannot be maintained at such levels if predominately variable wind and solar generation.
  3. Grid capacity is saturated in many locations and requires additional transmission lines – The cost and environmental impact of new transmission lines is considerable, yet still is planned as the only alternative in locations from California to Texas.  However, these new lines only defer the stability and reliability problems.For grid reliability, transmission assets are sometimes deployed in duplicate, then used at low capacity in case of failure – the planned under-utilization of expensive assets is wasteful.  Alternative pathways to assure reliability should use redundancy such as is commonplace in the internet, and does not require under utilized assets.
  4. Wide-area grid topography results in inefficient energy flows by routing around mountains and lakes– energy flows across the grid according to Ohm’s law, and often takes undesirable detours due to geographic features, wasting transmission capacity.
  5. Energy flows cannot be identified or traced- Energy flows into and out of the grid at millions of points, and there is no tracing of the energy.  This makes it impossible for a user to ascertain that they are in fact using green energy. This also makes it difficult to allocate expenses for transmission appropriately.

The Interconnected Grid is Prone to Failure

Today's energy grid has been developed with extensive interconnections of grids which span continents.  The purpose of this interconnection is to improve reliability through redundancy.  However, in some ways, this interconnection increases the risk of wide area failures because any imbalance can be propagated quickly over an ever widening area.
The satellite photo depicts the grid failure in the Northeast in 2003, which affected 50 million people, and illustrated by the large black section stretching from Ohio to New York.  This blackout began with the failure of a single transmission line, and quickly spread across the region.
Large synchronized electrical systems are susceptible to large-scale failure.  Variable power generation such as PV and wind can cause the same fluctuations which lead to failures.  As the penetration of wind and solar increases, the grid will become increasingly susceptible to the same type of cascading failure.  The power industry is becoming increasingly concerned about these issues.  Three articles in the current Sept/Oct 2010 issue of IEEE Power and Energy address the issues of dealing with variable renewable energy on the grid.  The Digital Grid restricts any failure to the original cell and prevents cascading failures.

Increasing Proportions of Renewable

Many states in the United States have set goals of from 10% to 30% renewable energy.  Europe has set a target of 20% of energy to be produced by renewable sources.  Japan has set a target of 53 GW photovoltaic (PV) generation by 2030 , more than 25% of peak demand.  In the UK, it is projected that $10-$12 billion investment in grid infrastructure will be necessary to connect the planned 40 GW of wind generation by 2020.

The map, produced by the National Renewable Energy Resources Lab of US DOE, shows the potential wind resources available in the US.  Since the wind energy availability does not match population centers, where energy is consumed, an extensive new set of transmission lines, shown as green lines on the chart, has been proposed.

Our proposal with the Digital Grid is to segment the grid, and use energy storage within each cell of the grid to become energy independent, with only occasional energy transfers between cells.

Grid Inefficiencies

As pointed out by Eric Lerner*, electric power does not travel by the shortest route from source to sink, but also by parallel paths through other parts of the system (right above).  When the grid stretches around large geographical features, such as mountains, rivers and lakes, loop flows around the obstacle are set up that can drive as much as 1 GW of power in a circle, taking up transmission line capacity without delivering power to consumers (right below).

The first example wastes energy and the second wastes transmission capacity.  The Digital Grid eliminates these effects by providing for controlled flows of energy

*"What's Wrong with the Grid?", Eric J. Lerner, The Industrial Physicist, Oct/Nov. 2003

The Digital Grid Solution

The Digital Grid solution to these transmission grid control issues is to segment the grid into substantially self-sustaining regions or “cells”, then control the flow of energy between those cells using controlled, scheduled energy flows.
This segmentation can be done gradually, and the existing transmission lines can be used, therefore, making the cost no greater than current plans for upgrading the grid but without the need for costly new HVDC lines.
Any failure on the digital grid cannot spread outside the originating cell, improving the total grid reliability.
The map illustrates this concept compared to Japan where three such cells have already been implemented on the nationwide grid.  In Japan the cells were created due to the need to bridge the gap between islands and to integrate regions using different frequencies, though the same result of grid reliability has been achieved.