Rooftop solar cells blossom, posing new
challenges for power grid
Nov 09 - North County Times, Calif.
Solar power installations are sprouting on California rooftops like
leaves in the spring, but all that renewable energy poses new problems
for the aging power grid.
Solar panels and wind turbines offer the promise of clean electricity by
deriving their power from wind and the sun. But both suffer from the
problem of intermittency: A gust of wind can cause a mill to spin
faster, producing a power spike down the line, and a cloud passing over
a solar cell can cause a sudden drop in electricity.
Meanwhile, utilities are rushing to upgrade the ability of the region's
interconnected power grid, which is based on 100-year-old technology, to
tap renewable resources without causing problems for users.
"We're going to see more change in the next 10 years than we've seen in
the last 100," said Chris Baker, chief information officer for San Diego
Gas & Electric Co. "This is happening fast."
California utilities don't have a lot of choice in the matter, either.
The state has required them to get 20 percent of their power from
renewable sources by 2010 and 33 percent by 2020. Today, much of that
power is derived from large installations of solar panels or windmills,
a central generation model that resembles the traditional electrical
infrastructure of nuclear, coal and natural-gas plants.
But the state and federal government have both enacted subsidies for
homeowners who want to install their own rooftop solar cells. Those
subsidies, combined with a 9 to 13 percent drop in the cost of solar
systems, have driven a sharp increase in demand for new solar systems.
Utilities each manage their own branches of a subsidy program called the
California Solar Initiative. Southern California Edison's branch of the
initiative said it has received more applications for solar cells in the
first three quarters of 2009 than it did in all of 2008. In San Diego
County, the program helped install 2.1 megawatts of rooftop solar
capacity in October, the most ever for a month.
As the program meets new capacity goals, the government subsidies are
reduced.
"The incentive is decreasing, yet the adoption rate is increasing," said
Timothy Treadwell, an analyst for San Diego's initiative.
Rooftop installers say they're so busy, they're hiring new staff and new
crews.
Daniel Jagudnik, a sales manager with Natural Energy in Escondido, said
he has hired eight new salesmen and the company has brought on 10 new
technicians since the first of the year.
Jeff Van Dam, director of contractor services for HelioPower in
Murrieta, said he had to hire a third crew last month, and his company
has started a solar cell distribution division.
Managing energy variation
But renewable energy, and especially the kind produced all over the grid
by homeowners, creates new problems for utilities' power infrastructure.
Traditionally, power has flowed from generator to end user, with
occasional rerouting to manage peak demand.
Renewable energy flows at a variable rate: Solar power can't be
generated at night, and winds can die down, cutting output from windmill
generators.
Sudden drops could cause localized brownout conditions, or even brief
blackouts that shut down computers or medical equipment. If winds
suddenly gust, turbines spin faster, causing power spikes that could
blow out expensive televisions or at least blow out fuses.
Rooftop solar complicates matters further because buildings with excess
power can sell it back to the grid, creating a need for a system smart
enough to reverse the stream every time the sun rises or a cloud passes
by.
"That doesn't happen on today's grid naturally. The grid was built over
100 years ago; it does what it does," Baker said.
SDG&E's smart grid has five major components: smart meters, information
processing, sensors, communications and storage.
A new wireless communication system will be funded by a $28.1 million
federal grant won by SDG&E's parent company, Sempra Energy. The utility
plans to upgrade all 900,000 gas meters with communications modules by
2011. At the same time, it will install 1.4 million "smart" electricity
meters that will have the ability to measure and manage each household's
energy use, or possibly, production.
Over the next 10 years, Baker said, they will install sensors on each
part of the grid to measure the load and monitor usage, and an enormous
information technology infrastructure will be needed that can take in
all the real-time data and output it in a way that makes it possible for
system operators to use.
Big batteries on the way
And then there's that cloud-over-the-sun problem. Traditional
fossil-fuel generators can't modify their own output fast enough to
compensate for power fluctuations caused by variations in wind and
sunlight. Baker said utilities will need distributed energy storage to
smooth out power supply levels.
Batteries and other types of storage will have to be placed at many
different points in the electricity infrastructure, including generation
sites, transmission sites and even on homeowners' property. When
generation levels fluctuate, the batteries will absorb or release energy
to even out the load.
Baker said he isn't worried about this problem -- yet. SDG&E's renewable
energy portfolio will only hit 17 percent at the end of the year, and
Baker said he's comfortable with the grid's ability to handle even 20
percent renewables. More than that, and he gets worried.
As for rooftop solar, the problem is still too small to be a concern.
There are so few solar electric systems installed each month that SDG&E
can make individual appointments to install smart meters.
And all of Edison's rooftop solar capacity put together adds up to just
150 megawatts, roughly 0.7 percent of its peak load of 23,000 megawatts.
The problem of intermittency, and the real strain on the grid from
small-time generators such as homeowners, hasn't really hit yet.
But the state's requirement for 33 percent renewable energy by 2020
means SDG&E and Edison have 10 years to get all this grid work done.
The California Independent System Operator has oversight of the state's
energy grid. The agency is studying the challenges that will be involved
in creating a large smart grid like the one that will be required, but
it is optimistic that the job can get done.
"We are working towards these solutions," said Gregg Fishman, a
spokesman for the ISO. "I don't want to give the impression that there's
no problem, that everything is solved. The vision is there of how
smart-grid technology can provide the tools and the information flow to
make those tools work. It is coming together."
Call staff writer Eric Wolff at 760-740-5412.
-----
To see more of the North County Times or to subscribe to the newspaper,
go to http://www.nctimes.com.
Copyright (c) 2009, North County Times, Escondido, Calif.
Distributed by McClatchy-Tribune Information Services.
(c) 2009,
McClatchy-Tribune Information Services
|