Push to add wind and solar expected to force changes
in US power grid
by Eileen O'Grady
17-04-09
The push to add more renewable wind and solar MW to the US electric mix
will force changes in the way the power grid operates to keep electricity
flowing reliably, said an industry watchdog.
Climate-change concerns have led more than half of US states to mandate that
a percentage of future electric supply come from less-polluting resources,
such as wind and solar power that emit no greenhouse gas.
US legislators are also discussing a federal mandate. However, a report from
the North American Electric Reliability Corp (NERC) points out that many
types of renewable power are much different from power plants that burn coal
or natural gas, plants that can be turned off and on as needed to meet power
demand. That lack of control, or variability, creates thorny integration
issues for operators of the bulk-power network -- the large power lines that
move electricity from plants to neighbourhoods, NERC said.
The push for more renewable power, "has the potential to fundamentally
change how the system is planned, operated and used -- from the grid
operator right down to the customer," said Rick Sergel, NERC president.
In 2008, a record 8,300 MW of wind generation was installed in the United
States, according to the wind industry. NERC estimates that 145,000 MW of
all types of variable generation could be added to grid in the next 10
years.
"Even if only half of this capacity comes into service, it will represent a
350 % increase of variable power from 2008," said Mark Lauby, a NERC
director.
Already recognised is the need for thousands of miles of new transmission
lines to connect distant wind and solar facilities to power-hungry cities.
About 7 % of the US population lives in the 10 states where the capacity for
wind generation is the greatest, the grid group said. While daunting, that
is just one challenge facing the industry as it seeks to reduce carbon
dioxide emissions from electric production, NERC said.
Another issue is the tendency for wind generation to be strongest at night
when electric demand is low and weak during the day when power use soars.
Managing the often rapid jump or drop in wind output is another obstacle for
other power plants on the grid since electricity is consumed in real-time
and can't be stored in large amounts, NERC said. If electric demand is high
and wind generation falls off, other power plants must increase output
quickly to balance the system to prevent blackouts or other disruption.
NERC's study calls for reducing obstacles to build power lines. Other
recommendations include better wind forecasting and spreading variable
resources across large geographic areas to lessen the impact of weather
changes on output.
NERC's recommendations may fall short of some renewable power industry
goals. Some want new transmission lines to be dedicated to "renewable-only"
generation and have suggested that NERC relax some long-standing operating
standards related to grid frequency. Lauby, however, said the NERC study
calls for wind and solar generation to be integrated within NERC's current
operating requirements.
Source: http://planetark.org |