Renewable Energy Installer December/January 2014 | Page 20

Knowledge: PV
Broadening horizons
Whilst the commercial PV market is beginning to grow, this sector is still only
realising a fraction of its true potential. Hannah Bell, technical advisor at PV
distributor Krannich Solar, discusses how rethinking system configuration can
open-up a wealth of installation possibilities
any of the installers we speak
to are making the transition
from domestic to commercial
installation. This progression is
not without its challenges, of course, both
technically and in terms of market conditions.
Some of these factors are far easier to deal
with than others, however, and one specific
area where we find installers are creating
unnecessary barriers for themselves is by
misunderstanding how to make the most
of a site, or even what constitutes a viable
installation opportunity.
M
The only way is… south?
We all know that, in theory, a south-facing
installation is optimal due to its higher
peak output, but what many people seem
to underestimate is how productive a dual
aspect system can be – i.e. only about 8
percent less than a south-facing array.
Installing modules in an east/west orientation
gives a longer generation window throughout
the day, thanks to the east-facing modules
harvesting the morning sun and the west-
facing ones generating later in the day. This
is ideal for commercial premises which want
to use the energy they generate, as it gives a
more useable production curve throughout
the day – an excellent selling point for
prospective customers.
East meets west
Using an east/west mounting system, such
as the D-Dome solution by K2 Systems,
also offers excellent space utilisation and
can enable the installation of a significantly
larger system. The low (10°) pitch of the K2
D-Dome system not only facilitates a low
ballast requirement, making it ideal for roofs
with a low weight threshold, but also negates
or reduces the shading issues which other
flat roof mounting systems can create. Whilst
10° is not the optimum generation incline,
it still offers a good yield and can make an
20 | www.renewableenergyinstaller.co.uk
installation possible where it might not
otherwise have been, or can simply enable
consumers to get more from their roof space.
The generation game
The comparison below between two systems
shows that using an east/west configuration
enables the installation of a larger system
within the same space:
Orientation South East/West
Number of
modules
possible 33 44
Generation
capacity 8.25kW 11kW
Approx. annual
system output 7,319.1 kWh 9,100.3kWh
Approx. annual
output per m² 61.0 kWh 75.8 kWh
These calculations are for a 120m² roof
area, using 1640 x 990mm modules at a
10°inclination and are based on London
weather and irradiation data.
As these figures show, utilising the
east/west system enables the installation
of 33 percent more modules and the system
would have a 24 percent higher annual
output capacity. So, whilst the efficiency of
modules is slightly lower in an east/west
orientation than when south-facing, this
system comparison demonstrates that the
overall system output can still be higher and
therefore produce a greater ROI.
New view: Using an east/west mounting system,
such as the D-Dome solution by K2 Systems,
offers excellent space utilisation enabling the
installation of a significantly larger system, says
PV distributor Krannich Solar
Current affairs
As with any installation, inverter choice is
critical and – for east/west array splits –
inverters with dual MPP trackers are ideal
because the separate MPPTs ensure that the
production of both orientations is maximised
independently. This eradicates the crippling
limitations you would experience with a
single MPPT, multi-string configuration.
Similarly, it’s worth noting that dual trackers
are also very versatile on single orientation
arrays in the presence of module shading or
unbalanced string loads.
Keep your options open
Considering an east/west configuration is
just one example of how choosing the right
mounting solution can broaden the horizons
of your installation work. It’s all too easy to
become preoccupied with what is considered
optimal and underestimate how productive
a system can be when you consider other
options.
Ultimately, installing a system which best
meets the customer’s needs whilst delivering
the maximum ROI can only increase
consumer confidence in solar energy and
contribute to the much needed growth of
our industry.