Rooftop solar cells blossom, posing
new challenges for power grid
Nov 09, 2009- North County Times
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
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
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
"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
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
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.