Environmental Engineering Reference
In-Depth Information
ofshore wind energy, environmental impact and energy policy. In
the paragraphs below, I will summarise our work in two of these
areas: hybrid power systems and wind resource assessment.
Hybrid energy systems have been defined as “combinations of
two or more energy conversion devices (e.g., electricity generators
or storage devices), or two or more fuels for the same device, that
when integrated, overcome limitations that may be inherent in
either.” In our work at UMass, we have focused particularly on
those hybrid systems, which included, at least, wind turbines and
diesel generators; these are usually referred to as “wind/diesel
systems”.
Hybrid power systems are intrinsically interesting because
(1) they are potentially quite useful to many people in the world
with limited access to conventional electricity and (2) they are
technically quite challenging. They are also interesting because they
serve as microcosms for some of the same issues that are just
beginning to be encountered as large amounts of renewable
generation begins to be added to much larger central power
networks.
Work at UMass has involved a number of topics in this area.
The key question was how to provide a very large fraction of the
electricity in an isolated electrical network from a fluctuating
resource, such as is the natural wind. We considered fluctuations
over all time scales ranging from seconds to seasons. The studies
we undertook included systems engineering as well as time domain
and frequency domain simulations. To study the electrical aspects
of such systems, we designed and built a complete hybrid power
system hardware test bed. This test bed included a wind turbine
simulator (using a purpose-built DC motor-AC generator with
computer control), diesel generators, electrical load simulator,
rotary converter (for voltage support), optional battery storage
and specialised controllable devices (for power control and/or
frequency control). A schematic of the UMass simulator is shown
in Fig. 24.3.
The hybrid system studies lead to the development of the
Kinetic Battery Model, which has since become used throughout the
world in a wide range of battery applications. Further development
and expansion of this model is still continuing at the present time.
One of the major accomplishments of our hybrid power
system work was the development of the Hybrid1 computer code
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