No one can control floods, but yes, it is possible to control the damage to solar PV
plants due to them. The destruction of solar PV plant components largely depends upon
the flood volume, velocity, duration and depth. Here are a few of the flood consequences
on solar PV plants:
- Plant may get completely submerged and thus damage can set in.
- Module mounting structure (MMS) foundation may settle down because of soil erosion
or water logging.
- Corrosion may accelerate resulting in damage of MMS posts.
- Underground cables and cables present in control and inverter stations may submerge
in water amounting to high plant downtime.
- In case of huge water pressure, boundary wall of plant may collapse.
To avoid all such situations, it may be essential to conduct an in-depth hydrology study
during the project planning stage, as we believe in ‘Prevention is better than Cure’.
The study considers flood occurrence, distributions and water movements. Next, it is
required to consider technical aspects for flood water treatment, in case, there is a
flood situation due to unavoidable reasons, like inaccessible location or others; then
this helps treating the affected plant components effectively and minimize the losses.
SgurrEnergy is known for its thorough and practical approach towards conducting hydrology
studies for large utility scale solar PV plants; our team is proficient at identifying
all the possible associated risks and coming up with effective mitigations well before
the project gets into execution phase. This study helps the project stakeholders to
cater a feasible and an economical solution.
INTRODUCTION
A flood risk analysis is a beneficial procedure before solar plant installation. However,
it is advisable to hire technically educated and experienced professionals who can
ensure accurate mathematical calculations for flood prevention at a given site. Flood
can be of many types; they may be broadly classified as river flood, flash flood, ground
water flood, sewer flood and coastal flood.
Investors should take a look at all the conditions and emphasize on drainage assessment
in order to avoid the future troubles. Hydrology studies essentially play a pivotal role
at odd sites, which are prone to frequent floods. The study reveals all the possible
outcomes and its prevention techniques before the actual arrival of flood.
TYPES OF FLOODS AT A GLANCE
River flood: When the solar PV plant is located near a river, then there is a possibility
of floods as heavy rainfall can lead the river to cross its limit and overflow the
banks.
Flash flood: In case of heavy rainfall, it becomes impossible for ground and drainage
system to absorb water quickly. The water then drains in the area of solar plants and
causes damage to its components.
Ground water flood: Prolonged rainfall causes saturation of ground, which means the
ground is incapable of absorption of extra water. Thus, the excess water raises the
ground level and results in flood in PV plant area.
Sewer flood: This situation arises due to a blockage in sewer. But usually the PV plants
are built in remote areas, hence the possibility of sewer flood is comparatively low.
Coastal flood: Situations like low tides, high tides or tsunamis cause major damage to PV
plants situated near coastal areas.
NEED FOR EFFICIENT DRAINAGE SYSTEM
It goes without saying that an efficient drainage system can handle the flood water
effectively. In case of any fault in the natural drainage, artificial drainage systems
can be provided for water management. Another solution is to clean or widen the natural
drainage and improve its performance and efficiency. It is important to remember that
proper functioning of natural or artificial drainage depends upon the site topography.
Below mentioned are some conditions which further worsen the drainage situation:
- Low level of site as compared to neighbouring locations
- Huge watershed area in nearby location
- Shallow ground water table
- Impermeable soil
- Steep slope of land
In few of the conditions even mechanical de-watering may be of limited use.
ALTERNATIVE WAYS OF BYPASSING FLOOD WATER
In case the drainage system is not a feasible solution for any site, then an alternative
way is to channelize the excess water from the outside of plant boundary. If the site
topography does not permit this, then one can restrict the water entry inside plant
through an effective retaining structure. At times, it may be required to forcefully
drain off water using water pumps.
It may be note that channelizing water or restricting it outside the plant premises may
create social issues. In addition water channelizing or construction of retaining
structure may require huge capital expenditure; hence it is important to make a choice
between:
- Channelization
- Diversion of water
- Design the solar plant components by keeping in mind the flood impact on them
DAMAGE ON PLANT COMPONENTS DUE TO FLOOD
Flood can cause a substantial damage to PV plant components. Components like PV modules,
DC cables and electrical equipment may not be covered under warranty in such a
situation. Floods may lead to in shutting down of plant / inverter section which
resulting in a revenue loss.
Below mentioned are the damages that may affect the plant components.
PV modules: Due to submergence of PV modules, floating debris can cause
damage to PV modules. In such situation module replacement may be required.
Cables and electrical equipment: DC cables are not designed for
submerged conditions, in this condition the isolation resistance dips to the lowest
leading inverter tripping and plant shutdown. Huge capital, efforts, and time may be
required for cable replacement.
Structure foundations: Water logging can cause settlement of foundation.
In such cases, cohesive soil will cause more damage as compared to non-cohesive soil.
Recovery from such situation requires dismantling of table which is a time-consuming
task.
Accessibility: Heavy flood may hamper the accessibility which means that
it will become difficult for technicians to approach plant due to water logging.
Steel posts and foundations: Erosion of foundation and corrosion of
steel post may happen because of excessive water. Usually zinc coating is applied at the
corroded segment of post and additional concrete is applied to the foundation.
Boundary Walls: Excess water may damage boundary walls. This may cause
huge damage to property and livelihood.
Warrantee: PV plant component which are not designed by considering
flood will void the warrantee.
SGURRENERGY APPROACH
SgurrEnergy has years of experience is assessing flood risks for large utility scale
solar PV plants. Our team is capable in making precise computation for generating an
optimal solution during pre or post construction. We are here to make our clients aware
about the possible consequences of floods at their site and the best solution for the
same.
SgurrEnergy considered rainfall and topography to be the key parameters for commencing
hydrology studies. Rainfall information is preferably collected from meteorological
stations, but in absence of meteorological data, statistics from TRMM (Tropical Rainfall
Measuring Mission) are used. Information measure for ground elevation in the watershed
area is considered quite accurate. However, in case of unavailability of such data
satellite based SRTM (Shuttle Radar Topography Mission) with 30m resolution can be a
good assumption. Other factors that may be assessed for flood risk analysis are ground
water table, soil properties, land cover etc.
SgurrEnergy typically uses industry known tools like HEC-RAC, HEC-HMS, QGIS and Civil 3D
for flood analysis; this computes the flood volume, distribution, depth, and velocity of
flood; basis of which internal drainage system or diversion or restriction of flood
water from the plant premises and impact of excessive water on plant components are
planned.
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