IEEE Electrification Magazine - March 2015 - 66

Table 7. a Summary of Currently available energy-Storage Technologies.
Technology

Maximum
Current Rate

Energy
Density

Cycle
Life

Calendar Life

Maintenance
Requirements

Technology
Maturity

Minimum
Scale

Lithium-ion

High

Medium

Low

High

1 kW

Lead-acid

Medium

Low

High

1 kW

Sodiumsulfur

Low

Medium

High

Low

High

1 kW

NaNiCl

Medium

High

Low

Medium

100 kW

Flow battery

Low

High

Low

100 kW

Flywheel

High

Medium

High

Low

Medium

200 kW

maintenance requirements, are a flexible energy-storage
technology appropriate for a variety of applications. NaNiCl
technology provides an excellent energy density and cycle life
without the need for heating, ventilating, and air conditioning
systems or other auxiliary loads. In both cases, battery modules are combined into a sophisticated
energy-storage system with multiple
levels of control and protection. Each
container includes a dedicated batterymanagement system (BMS), circuit
breaker, and contactors as well as current and voltage sensors. A master
BMS provides control across multiple
racks and/or modules. The specifications of the complete battery systems
are shown in Table 8.

power. Because solar is not a base load power source,
the solar system is oversized based on electricity
consumption requirements during these peak production
hours and store the energy for off-peak production hours,
the period of time when the solar system is not producing
power, using advanced energy storage. The system is also designed to
eliminate the inherent inability of
renewable power production to loadfollow due to peak power design or
constantly changing input power
levels from variations in the sun,
wind, or other production sources.
The total budget of the solar
power deployment initiative is
US$13.136 million, of which US$3
million is sponsored by a U.S. Department of Agriculture grant and the
remaining US$10.136 million is cost-shared by Veriown.
Upon the completion of the initiative, 3.3 MW of solar PVs
will be installed and operational at UVI's two campuses.
Veriown will enter into a PPA with UVI. The PPA is a financing arrangement that allows UVI to purchase solar electricity with little to no upfront capital cost. To achieve this, UVI
provides unused rooftop, land, or parking lot space as a
location for a solar installation. Veriown pays for the cost of
the solar installation and assumes all responsibility for
ownership, operation, and maintenance once the solar

S&C's Storage
Management System
is an example of a
utility-grade powerconversion system.

Project Performance Measures
Table 9 shows the quantifiable project performance measures that will be achieved as a result of the solar power
deployment initiative.

Project Financing for the Solar Power
Deployment Initiative
In the solar power deployment initiative, Veriown will use
solar production to lower the cost of energy to UVI by
more than 40% during peak production hours, defined as
the period of time when the solar system is producing

Table 8. The Desired System-level battery Specifications.

Item

St. Croix

St. Thomas

Technology

Lithium-ion

NaNiCl

Total embedded energy
(beginning of life)

2,000 kWh

3,000 kWh

2,400 kWh usable
3,000 kWh embedded

Cycle life

6,000 cycles

4,500 cycles

Round-trip dc efficiency

At least 90%

Operating temperature range (to be
maintained by high-voltage ac system)

23 ± 5 °C

−10 °C to +40 °C

I E E E E l e c t r i f i cati o n M agaz ine / March 2015

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2015