NEWS IN THE WORLD OF POWER AND INTEGRATED BUILDING SYSTEMS
> SPRIG ELECTRIC is one of the first
electrical contractors (ECs) in the country
to pair Tesla’s Powerpack battery with a
350-kilowatt (k W) commercial rooftop
photovoltaic (PV) system. In its first
month, the paired system has cut energy
costs at its San Jose, Calif., headquarters
by 80–95 percent.
“The solar system has been producing
about a third of our overall load in a day,”
said Michael Clifton, operations manager
of Sprig Electric’s Energy Efficiency
Division. “In two to five years, [energy
storage] will be a huge market for ECs.”
This system includes 1,177 solar panels
on 20,000 square feet of the building’s
roof. Sprig installed a 500-kilowatt-
hour/250-k W Tesla Powerpack battery
in the parking lot and connected it to the
grid and PV system. It also includes five
100-k W Powerpack commercial batteries,
a 250-k W inverter and a direct-current
combiner. It can expand with additional
Powerpacks and inverters up to hundreds
of megawatts. The battery and solar-power systems are separate and parallel.
By acting as energy storage for grid
and PV power, the Tesla system optimizes
energy savings, increasing utility savings
from solely using solar electricity. Other
parts of the country use similar battery
systems to take the load off existing
generators by allowing the system to
correct frequency regulation, Clifton said.
A control system provides regulation.
It factors in the amount of energy from
the panels, amount of power stored in the
battery and building load and moves power
around based on these factors.
The batteries charge in low demand
periods when an energy surplus is available
and then discharge stored power during
times of high demand and higher rates.
Load shifting and peak shaving are
two advantages of the system.
Sprig Electric went with Tesla because
of the smaller system footprint, compact
batteries and cooling technology, and
easy-to-use control system, Clifton said.
Tesla Powerpack batteries are based
on lithium-ion technology, and their
modular design was adapted from Tesla
Sprig Electric expects this system to
dramatically reduce energy costs. Rebates
and tax credits are also available.
Companies with high peak demands,
such as manufacturing facilities or
utilities, will appreciate the system’s
ability to smooth out loads. It also offers
load shifting for companies with certain
rate structures or large ratios between
peak and off-peak.
> FROM WAVES TO WOOD CHIPS TO GRASS, the renewable
energy era has been all about generating power from unlikely
sources. A Washington, D.C., utility has taken this trend one step
further and is harnessing power from sewage effluent.
Last fall, DC Water unveiled a $470 million waste-to-energy
project at its Blue Plains site. According to the utility, the project
is producing net 10 megawatts (MW) of electricity from the
The project broke ground in 2011, incorporating an
innovative technology from Sweden known as the Cambi
thermal-hydrolysis process, which had never been used before
in North America.
The Blue Plains facilities include a dewatering building; 32
thermal hydrolysis vessels; four concrete, 80-foot-high anaerobic
digesters that hold 3. 8 million gallons of solids each; and three jet-engine-sized turbines. DC Water called it the largest of its kind.
Thermal hydrolysis uses high heat and
pressure to cook the leftover solids at
the end of the wastewater treatment
process. It breaks down the cells to
make the energy easily accessible
to the organisms in the next stage of the process, anaerobic
digestion, which produces methane gas. The system captures the
gas and feeds it to three turbines to produce electricity.
“This project embodies a shift from treating used water as
waste to leveraging it as a resource,” said George S. Hawkins, DC
Water CEO and general manager.
The process also produces other benefits. The solids are
cleaner at the end of the hydrolysis, and DC Water uses the bio-solids as a compost-like material for urban gardens and green
Washington, D.C., Generates Electricity From Sewage Sludge
Sprig Electric Cuts Energy Costs With Unique System