EDITOR’S CHOICE
RENEWABLE ENERGY OPTIONS
CRESSALL
RENEWABLE RESISTORS
In recent years, renewable energy options
have become much more efficient and
feasible. This has led to a large adoption
of these applications, an especially
poignant point in the face of current
environmental issues. However, just like
all other power generation methods these
applications require resistors. Here Simone
Bruckner, managing director at power
resistor manufacturer, Cressall, explains
the challenges in designing resistors for
renewable applications.
In May 2019, the UK went two weeks without
using any coal to generate electricity. This was
the longest period of time that the UK has
not burned coal since 1880. A large part of
this success was put down to the increasing
availability of renewable energy sources such
as wind, solar and tidal energy.
Renewable technologies are reaching a level
of maturity where they are heavily impacting
many nations’ energy mixes. In fact, a few
days prior to the coal-free period, solar
energy accounted for 25 per cent of energy
generated.
With the recent news that E.ON UK plans
to power more than 3.3 million customers
with 100 per cent renewable electricity as
standard, it is clear that renewable energy
is starting to take the main stage and the
growth of the sector is set to continue. This is
reaffirmed by public perception, as a YouGov
survey found that more than three in five
Britons currently on a standard electricity
deal would switch to a renewable electricity
supplier if the price was reasonable.
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PECM Issue 41
Although embracing renewables is great for
the environment, it does face its own set of
challenges. Each source of renewable energy
is dependent on the environment around
it, meaning that production can suddenly
soar and require the system to be capable of
dealing with a sudden influx of power.
For example, wind turbines are generally
connected to the distribution network
through step-up transformers. When these
are energised, high inrush currents occur.
These currents cause overvoltages on the
distribution network, likely damaging
equipment upstream.
Issues like these can be remedied by using
technologies such as pre-insertion resistor
(PIR) in the circuits. PIRs, such as those offered
by Cressall Resistors, are a three-phase
resistor, insulated for the full system voltage,
typically 33kV and fitted with isolating
devices as required.
PIRs have a high thermal mass allowing them
to absorb energy from high inrushes while
still being compact enough to fit efficiently in
a transformer substation.
These problems also extend to solar power.
For example, when installing new solar panels
or disconnecting existing installations from
the grid for maintenance, the panels continue
generating electricity. As a result, discharging
this excess energy must be prioritised to
prevent damage occurring to the solar
panel system. Resistors are crucial in safely
dispersing this excess energy.
Dummy loads resistors transfer the excess
energy into heat and release it into the
environment to prevent the solar panel from
overloading. Cressall offers a large range of
different varieties of high-power dummy load
banks that can be customised for diverse
applications, such as low noise versions for
urban locations.
Once in operation many solar farms equip
panels with small electric motors to maintain
the cells at the optimum angle compared to
the sun for the longest amount time, in order
to maximise energy generation. As such, they
require braking systems to ensure they are at
the correct angle.
For this reason, Cressall also provides dynamic
braking systems that not only ensure correct
positioning but also that the braking energy
is not wasted but is put back into the system.
Renewable energy is becoming an
increasingly important part of our energy
mix. The growth in the efficiency of
these technologies means that adopting
renewables becoming more achievable
than ever. As these technologies develop, so
too will the resistors that integrate into the
current power network.
For more information on Cressall’s
renewable energy offering,
visit the website:
www.cressall.com/renewables