Engineering Earth’s Development, Preserving Earth’s Integrity
RISKS AND OPPORTUNITIES IN THE
OPERATION OF LARGE SOLAR PLANTS
Originally Presented at:
Solar POWER-GEN 2013
San Diego, CA, USA
Article Re-Print
Main Author: Francesco Belfiore
Co-Authors: Tekla Taylor, Beth Moisan,
Mario Zappia, Ettore Cinarelli
1.0INTRODUCTION
A primary objective for any power plant is to
ensure the plant continuously and reliably operates,
thereby generating the maximum economic and
energy performance returns.
Solar Photovoltaic (PV) power plants are no exception. The operation and maintenance (O&M) of
large PV plants requires an integrated management
system that is implemented throughout the entire
lifecycle.
Since PV power plant management practices are
still emerging and evolving, Golder’s experience in
managing a very large facility in Italy, can provide
critical insight to the actual risks and opportunities
involved in the operations as well as their impact on
return on investment.
The consortium of the international investors for
the Montalto di Castro PV Plant retained Golder to
conduct a Technical Due Diligence of the project
in 2010 while the project was under construction.
Golder analyzed and validated both general and
technical factors affecting the productivity of the
power stations. Since 2011 Golder has supervised
the completion of construction and continues to
provide supervision of the O&M activities.
In the U.S., Golder is able to provide ad hoc integration of engineering and environmental services
for the entire solar project lifecycle (such as the
Montalto di Castro PV plant) from site selection,
planning and environmental permitting through
commissioning and operation and finally, decommissioning phases for any solar PV project.
This paper is based, in part, on the experience of
Golder in the assessment and supervision of O&M
activities of the Montalto di Castro power station
and other similar large scale PV plants.
lated to the upstream phases of the project lifecycle
(siting, development, design, etc.) and may have
very significant effects on the downstream phase
(performance, production).
The operation model presented here assumes that
a primary O&M contractor has direct responsibility, using its own resources or sub-contractors, to
manage all electrical generation and transmission
systems, security systems, visual mitigation (green
areas on the perimeter) management and pest
control. Other contractors are responsible for civil
works and general housekeeping, including cleaning of the panels, and specific parts maintenance.
In particular, on behalf of the owner of the plant
Golder directly supervises the entire operational
structure and related activities.
Our practical experience suggests that many issues
emerging during the O&M phase are strongly re-
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Article Name
from tax incentives currently available only to
fossil fuel projects. The proposed Master Limited
Partnership Parity Act (S 3275) would amend the
federal tax code to allow wind and solar schemes to
fall under the attractive Master Limited Partnerships business structure and thereby be taxed as a
partnership with access to capital at a lower cost.
Figure 1: Renewable portfolio generation goals
1.1THE US ENERGY POLICY AND
MARKET FOR LARGE SCALE
SOLAR PV PROJECTS
The current political climate in the US and lack of
a long term energy strategy make it increasingly
unlikely that a federal renewable energy plan
will emerge any time soon. The extension of key
stimulus programs remains uncertain and continued
political stalemates will almost certainly delay any
progress in renewable energy programs.
One example of this uncertainty is the end of the
federal PV solar investment tax credit (ITC) set to
expire in December 2016. There is a permanent
10% ITC for solar that will remain available after
the 30% rate expires, however, unless there is a
renewal of the ITC, there will be added pressure to
lower balance of system costs. In the absence of
comprehensive federal legislation and regulation,
the States have continued to evolve their solar
programs and incentives to fill the void, primarily
through the enactment of legally binding Renewable Portfolio Standard (RPS) legislation or the
establishment of non-binding renewable portfolio
goals. Specifically, twenty-nine states and the
District of Columbia have enacted RPS legislation
that specifies the percentage of renewable energy
the state’s utilities must contribute by a certain
future date. In seventeen of these states, there are
specific minimum solar contributions (or carve-outs)
required under the RPS. Another eight states and
two territories have renewable portfolio generation
goals. (See Figure 1)
Recent attempts to establish new RPS standards in
several states (e.g., Kentucky, South Carolina and
Oklahoma) have been unsuccessful. However, other
bills in 2012 have passed to strengthen or adjust
RPS requirements in Maryland and New Jersey,
providing further confirmation of the continued
patchwork regulatory and incentive status that
solar developers must contend with across the US.
Despite the challenges and uncertainty, the US
continues to be a bright spot in the global solar
market. The trend in the US is toward larger capacities for utility scale projects and it is estimated that
a total of 3.2 gigawatts (GW) will be installed in
2012, representing an increase of approximately
70% from 2011.
The top utility scale PV projects rated by installed
MW currently under construction are located in
California and Arizona, due to California’s aggressive RPS and ideal climate conditions in the western
US. Other western states, such as Oregon, Nevada
and New Mexico are also experiencing increased
utility scale development activity. The second quarter of 2012 experienced the largest growth period
in US history for solar utility installations, with 742
MWs of solar PV installed. The growth is primarily
attributed to two Arizona projects, Agua Caliente
project (290 MW) and Mesquite project (170 MW).
Once complete, the Agua Caliente project will be
the largest solar PV power plant in the world.
The Update and Streamline REIT Act (H.R. 5746)
calls for revisions to the tax code to clarify the
eligibility of renewable energy generation to allow
for REIT financing. Like Master Limited Partnerships, REITs avoid the double taxation of traditional
corporate structures, and are limited to investing in
certain asset classes, which in this case means real
property. REITs pass through their income, rather
than their tax liability to investors and the dividends
are treated as ordinary income to the investor. It
is perhaps unlikely that such bills will be passed
so late in an election year, but it may herald a new
vision of renewables financing in the US.
The US Department of Interior, in an effort to
promote solar development has identified 17 solar
energy zones across six western states totalling 285,000 acres of public lands, which will be
regarded as “priority areas” for solar projects. New
projects in these energy zones will benefit from
faster (streamlined) permitting procedures. It is estimated that the energy zones could support 23.7GW
of generating capacity.
These initiatives provide a positive message for
future growth in the utility scale PV market. Along
with this growth will be continued improvement in
equipment technology and operational practices
that ensure plant reliability and enhanced performance. Sharing of best management practices
as the industry evolves will further support these
objectives.
It is predicted that the utility scale solar market
will continue to experience annual growth from
2012-2016 in the 25% to 30% range (SEIA Solar
Market Insight Report Q2 2012, http://www.seia.
org/research-resources/solar-market-insight-report2012-q2). This growth will be dependent on increasing regulatory certainty through standardized
or streamlined permitting processes and providing
access to affordable capital.
Two US senators have introduced legislation that
would allow renewable energy projects to benefit
Figure 2: Aerial view of the Montalto di Castro
solar PV farm
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Article Name
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1.2 CASE STUDY: THE MONTALTO DI
CASTRO PV PLANT
The Montalto di Castro PV plant is located in central
Italy and occupies over 345 acres at two locations.
The two locations have a combined capacity of 51
MW (45 + 6) and together represent one of the
largest PV farms in Europe. This PV plant delivers
enough clean energy to the grid to meet the needs
of over 30,000 households annually. (See Figure 2)
The 45 MW PV plant is structured in 210 building
blocks, each block consisting of a self T0 tracking
system, 148,488 modules, or 12,374 stings with 12
modules per string. The power is converted to AC
by 68 inverters, each coupled with a 630 kVA transformer that raises the voltage to 20,000 V. The 5
inverter cabins contain inverters, transformers and
auxiliary systems are distributed in two main areas
of the power station. Each inverter cabin is linked
by medium voltages distribution lines grouped in six
main distribution rings. The three rings of each area
connect to the interconnection switchyard placed
approximately in the middle of the power plant. The
interconnection switchyard then connects to the
Terna (National Transmission System
Operator) Substation by means of redundant
20,000 V interconnection lines, where two 25 MVA
transformers raise the voltage to 150,000 V and
allow the power to flow on the grid.
The 6 MW PV plant is structured in 34 building
blocks, each block consisting of a self T0 tracking
system, 20,088 modules, or 1,674 strings with
12 modules per string.. The power is driven by 9
inverters, each coupled to a 630 kVA transformer
that raises the voltage to 20,000 V. The 5 inverter
cabins contain inverters, transformers and auxiliary systems that are linked by medium voltages
distribution lines which form distribution rings that
connect to the interconnection switchyard placed
approximately in the middle of the power plant. The
interconnection switchyard then connects to the
National Transmission System Substation, operated
by Terna, by means of redundant 20,000V interconnection lines, where two 25 MVA transformers
raise the voltage to 150,000 V and allow the power
to flow on to the grid.
The Montalto di Castro PV plant is equipped with
single axis tracking systems that track the sun on an
east-west direction maximizing the exposure of the
panels during the day. The tracking system is also
capable of a special behavior of “backtracking” so
that when the mutual shadings between the rows
of panels begin, the tracking system does not follow
the sun, but adjusts to prevent any panel shading.
(See Figure 3)
Figure 3: Ground level view of solar array
2.0 OPERATION AND MAINTENANCE
ISSUES
2.1INTRODUCTION
Compared to many other power generating
technologies, PV plants have minimal maintenance
and service requirements. However, a continuous
O&M program is essential to optimize energy yield
and maximize the lifetime and viability of the entire
plant and its individual components.
Many aspects of O&M practices are interrelated
and significantly affect the performance of all the
components in the generation chain and project
lifecycle. Our experience in PV plant assessment
and supervision allows us to define risks and
liabilities, in terms of downtime, production performance, operational costs and time to complete the
required activities, that can then be turned in opportunities to meet or even exceed the expectations
of the developers and owners in terms of return on
the investment.
In particular, suitable planning, supervision and
quality assurance activities are critical at all stages
of the PV plant in order to minimize the risk of damages and outages, optimize the use of warranties,
avoid dilution of resources and ultimately optimize
the overall performance of the PV plant.
For convenience of presentation, the O&M issues
have been broadly classified in the following
categories:
QQ Land availability
QQ Engineering features
QQ Grid connection
QQ Contractors’ selection
QQ Extreme weather events
QQ Data acquisition
QQ Security
QQ Housekeeping
QQ Environment, Health & Safety
QQ Stakeholder management.
2.2LAND AVAILABILITY
Land use and availability may be an issue both in
terms of the actual plant site and along the main
transmission line interconnection route. These
issues need to be addressed early enough in the
process to avoid any problems during the operational phase.
Typically, the transmission line must cross plots of
land held by different owners, which can present
a challenge to purchasing or leasing the land. This
can ultimately result in some access or availability
restrictions to properties along the preferred route.
Solar parks are not typically proposed in landscapes designated for natural beauty, or protected
areas of archaeological or ecological importance.
Nevertheless, a careful assessment of these types
of potential fatal flaws should be performed early in
the project feasibility stage.
In the US, environmental laws and regulations vary
significantly from state to state and even county to
county, increasing the need for a fatal flaw assessment when siting a project. Depending on the state
or county, strict environmental requirements could
result in lengthy permitting and approval processes.
Proper regulatory review is critical to insure appropriate environmental studies are conducted.
In the US, lands that are used for solar development
are often owned by the federal or state government
or are Native American tribal lands. Different mechanisms for leasing public lands are used by each
State and the federal government. Many of these
entities are well-acquainted with granting grazing
or mineral rights but can be less familiar with the
installation of utility-scale solar projects. Developers
should consider the various forms of land-control
rights available from the state or federal government. The Bureau of Land Management has adopted
regulations specifying procedures for obtaining land
rights, referred to as Right of Way (“ROW”) grants.
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owner of the plant then requested authorization
from the Municipality to proceed with the split of
the municipality road and register it as a new land
parcel which would include a perpetual easement
right in favor of the plant, all without costs on the
Municipality side.
Thus, it is important to check in depth the cadastral
documents, the ownership titles, the land acquisition and easement agreements and the length of
the actual availability of the land, and possibly
request accurate topographic measurements of the
plant and connection line from the EPC contractor.
Moreover it may help to push the EPC contractor to
perform frequent topographic measures during the
construction stage.
Figure 4: Panel tracking system
Leasing or obtaining a right-of-way on Native
American tribal land is an option, particularly in the
Southwest. Developers should be aware that leases
and rights-of-way on Native American tribal land
require approval by the Bureau of Indian Affairs.
Developers should consult with the specific tribe regarding potential archaeological or other resources
on the tribal land because each tribe is in the
best position to evaluate which sites have cultural
importance and to determine issues associated with
leasing lands for solar projects.
In the US, the Environmental Protection Agency
has established the RE-Powering America’s Land
Initiative, which promotes the reuse of potentially
contaminated lands for renewable energy project
development. This initiative aims to revitalize
degraded land by promoting renewable energy as
a productive end use, when aligned with the community vision for the site aiming to turn liabilities
into assets for surrounding communities. Of the 60
sites developed thus far, 49 sites are PV solar facilities. In less than four years, RE-Powering tracked
a compound annual growth rate of 40%. While
the proportion of renewable energy projects on
contaminated lands is relatively small, RE-Powering
is seeing a marked trend, showing that this land
development strategy is gaining momentum.
Agricultural land may be suitable for solar farms,
especially if it is not used for arable applications,
since grazing remains possible within array fields
and indeed is particularly synergistic as it prevents
vegetation growth which may in due course shadow
the solar arrays. Solar farms have been proven to
even have the potential to increase the biodiversity
value of a site if the land was previously intensively
managed. However, it should be noted that political
and legal pressure to preserve agricultural lands,
particularly in California, are creating controversies
when attempting to permit utility scale projects on
agricultural lands. In the last few years, concerns
over conversion of agricultural land for utility use
have begun to gain political steam putting pressure
on local officials approving projects.
Early management of the above issues may result
in a more efficiently managed project from both a
time and cost perspective for the permitting, construction, start-up and operation processes.
Any grant of a property right must contain certain
legal elements no matter where the property is
located in the US. Many states require the grant
of a solar easement to describe the dimensions of
the easement, the estimated amount of sunlight
directed to the system, any permitted shading by
vegetation and other plantings, the corresponding
reduction in access to sunlight, and any proposed
compensation to the grantor of the easement. The
solar easement must also contain state-specific
requirements. A state’s focus may be affected by
terrain, character of the area or weather. Some
states may be height- or design-sensitive (California, Colorado) or locale-sensitive (Hawaii), or may
focus on visibility and placement (North Carolina),
orientation (Wisconsin), zoning (Rhode Island), or
setback issues (Oregon).
2.3ENGINEERING FEATURES
Many important technical aspects concerning the
plant should be addressed in the planning and
design phases. Issues such as the selection between
fixed mount or tracking systems, and centralized
(maximum production) or distributed (maximum
availability) conversion systems, and the possibility
to have flexible control over the power production,
in relation to the electricity market demand, should
be carefully evaluated in terms of potential implications well before the plant enters into operation.
As a practical example of above issues, in our
case history the facility was designed to occupy a
former cattle-track owned by the Municipality, not
recognized until the plant was actually built. The
A common choice at the design stage is the type
of tracking system. Mono-axial tracking systems
have a better yield compared to fixed systems (up
to 25%), but may cause an increase in maintenance
costs due to the presence of moving parts and
management of a larger number of spare parts. In
our experience, the incidence of additional O&M
costs over a two year timeframe is quite small, but
could increase with time. (See Figure 5)
Figure 5: Terna switchyard
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Figure 6: Damages from heavy rainfall
Considering the effect on O&M activities as well
as costs, a choice can be made between a system
with a higher number of smaller electrical components, particularly inverters and transformers, or a
system with larger but fewer components. With the
latter configuration the production is maximized,
but in the case of failure of a component, replacement may be more difficult due to poor availability
or long waiting time. Because of the potential
yield loss that could result, it is our opinion that the
choice of the size of the electrical equipment units
should be based on their actual commercial availability and guaranteed supply time.
Furthermore, during the operation of the plant
it is necessary to have good capability to control
and regulate the energy output on the basis of the
actual electricity market demand. With the typical
current plant configuration, this regulation is only
possible by reducing the plant output. As a possible solution, the use of a suitable energy storage
system would allow a better flexibility in order to
match the actual demand in either case of reduction
or increase.
2.4GRID CONNECTION
The issues related to the grid connection can
often be crucial, both in terms of continuity and
convenience of the energy delivery. A reliable and
proactive relationship with the transmission system
operator can definitely help, especially when unexpected events or emergencies occur.
Interruption prevention measures, as well as clear
contingency plans and restart procedures, are key
to minimizing plant downtime. Failures caused
by either faults on the transmission line to the
interconnection switchyard or major interruptions
downstream in the utility area should be identified
and communicated quickly. (See Figure 5)
When emergencies occur, there may be many enti-
Figure 7: Repair of connection lines
ties involved in the location and repair of the failed
equipment. Different areas of the plant and utility
involve coordination of the utility operators, O&M
contractors, substation workers, local authorities
and health and safety agencies, which need to be
properly trained and prepared to manage the situation in a coordinated and knowledgeable manner to
minimize downtime and maximize plant availability
and production.
a number of factors, such as:
In our experience, preventive maintenance training
and sharing of plans and procedures with the other
stakeholders play a huge role in addressing and
resolving unscheduled outages and emergencies in
the shortest possible time.
A critical issue is to make sure that all the operations and activities that a certain contractor is
responsible for are identified early enough and that
the suitable conditions or permits are in place.
Another aspect that is relevant to the relationship with the transmission system operators is the
management of energy delivery required by new
dispatching regulations and procedures.
Recently the Italian authorities required operators
to predict the energy fed to the grid day by day, to
adopt a system to modulate the production in case
of emergency and to change the calibration of the
inverters to support the national electricity grid
during transient voltage or frequency variations
or to compensate excessive reactive power. These
adjustments are necessary due to the fast growth of
the production of energy from non-programmable
renewable energy sources. A positive relationship
with the transmission system operators can help to
implement solutions and investments in the right
direction to minimize the resources necessary to
meet these requirements.
2.5 Contractors’ selection
The O&M activities are complex and usually involve
a series of different skills and experience that may
require the contribution of various contractors and
sub-contractors. These should be selected based on
Familiarity with the site and equipment;
Proximity of the contractor’s premises;
QQ Number and qualification of staff;
QQ Level of experience and references;
QQ Financial status;
QQ Health and Safety record;
QQ Proper permits and licenses.
QQ
QQ
We recently had an issue with the contractor in
charge of panel cleaning who had not obtained
the required licence to extract groundwater from a
public well. This resulted in a delay of the cleaning
activities and consequently in a certain loss of
production.
2.6Extreme weather events
Extreme natural events, particularly those related
to climate change, such as hailstorm, typhoons
and floods, may cause serious damage in solar
plants. Severe structural and economic losses may
be incurred if specific components are damaged
such as structural elements, electrical parts and
components, control and inverter rooms, and connection lines.
Flooding can affect different functions of the plant,
both on the electrical generation side and on the
balance of plant (BOP) side, including connection
lines continuity, accessibility of different parts of
the plant, erosion of roads and other infrastructures, fence functionality and interference with
electrical, data monitoring and security systems.
In one particular case, the effect of excessive water
run-off due to an extreme rainstorm created insta-
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Figure 8: Elevated inverter room
Figure 9: Drainage system, perimeter fence and security cameras
bility on a slope which washed out the ground that
covered both the main and backup underground
lines which ran alongside each other, for a length
of around 200 meters and subsequently caused the
interruption of production for a few days until the
ground cover was stabilized and the lines repaired.
tion (SCADA) systems might not always be reliable
due to possible temporary losses of connection. A
regular check of the data, based on the physical
reading of the meters to compare the records is
strongly advised to confirm the final data.
Due to the same weather event, the main control
room was also partially flooded.
In general, these types of events can be prevented
by running a comprehensive risk assessment of
the possible impacts on the continuity of the plant
resulting from climate change, and particularly
extreme weather events. (See Figures 6 and 7)
Redundant systems for evacuation and connection
lines, as well as for monitoring and security systems, have to be carefully planned and designed in
order to constitute a viable alternative to the main
systems and guarantee the overall continuity of the
plant, under any circumstances.
Critical rooms, particularly those containing control
systems and critical electrical equipment, should be
designed to be raised above the floor of the site and
above the possible maximum elevation of water.
(See Figure 8)
Run-off and drainage systems should be designed
for extreme events to guarantee the functionality of
civil infrastructures, such as roads and fencing, and
grid connection systems. (See Figure 9)
2.7Data acquisition
Data acquisition is a crucial issue to be considered
to track and maintain optimal system and plant
performance. Accurate and reliable monitoring
data are also necessary to comply with regulatory
reporting requirements.
Based on our experience, production data collected
through the Supervisory Control and Data Acquisi-
Another aspect related to data acquisition is the
implication on the contractual goals set for the
O&M contractor in terms of guaranteed Performance Ratio, i.e. the overall plant production
efficiency. The minimum guaranteed parameters
are usually based on relatively safe assumptions by
the contractor and therefore an accurate technical assessment is needed to avoid an overall low
performance objective.
The assessment of the objectives of the contractor
is essentially based on the measurements of the
meteo station. iIt is critical that these are representative of the actual situation and therefore the
instruments need constant calibration and certification. It is also critical that the dust cover conditions
of the irradiance sensors are consistent with those
on the panels, in order to be comparable, i.e. cleaning should preferably be done at the same time. It
could also be advisable to keep additional sensors
to be cleaned more frequently in order to act as
benchmarks for the optimum values of irradiance.
The cleaning schedule can then be optimized
based on the difference between the measured
irradiance in the two sets of sensors. As a final
confirmation of the data, the continuous correlation
between different sources of the same data (e.g.
different meteo stations on site) can also supply an
early warning of problems in the data acquisition
systems.
2.8Security
Security systems are essential for a suitable operation of a solar farm in order to avoid damages and
possibly plant downtime from theft and vandalism.
In fact, a recent study on German PV plants shows
that up to 16% of the monetary impact of all the
possible damages are related to these aspects. The
access of unauthorized people to the plant has to
be prevented both for security and safety reasons.
In order to minimize the occurrence of such events a
suitable balance between a remote control system
and on site security personnel should be achieved,
depending on the size of the plant, the morphology
and extension of the site and the general environmental context. (See Figure 10)
The anti-intrusion software typically used is able to
detect moving objects, but not to recognize false
alarms due to movements not necessarily generated
by unauthorized access to the site. In our case,
when the security operator receives an alarm, he
has to verify the real source of the alarm and then
assign the proper category/level of attention, based
on a predefined classification (i.e. people, animals,
vegetation, weather), and record the event
accordingly. To address this issue, we are planning
to upgrade the software to learn from the past
events and to be able to systematically discern
between a real and a false alarm, at least for
repetitive movements.
Figure 10: False alarms detection software
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Thus, in our experience a specific combination of
operators, video cameras and dedicated software
has to be implemented to insure a sustainable level
of security of the plant, and specifically manage
alarms, discerning between real and false ones.
2.9Housekeeping
Typical housekeeping activities on a large PV plant
include a variety of concerns, such as management of water run-off and drainage, cleaning of
panels, control of vegetation, maintenance of civil
structures and roads.
In our case, we have successfully adopted a very
sustainable way to control the development of
vegetation, especially in the areas where the
modules are located, by letting a substantial flock
of sheep live and graze within the plant boundaries.
Besides the positive effect on cultural and social
continuity (the shepherds did not have to move
away from their historical land), we can avoid any
damage of the panels associated with the use of
mechanical equipment typically employed to trim
the vegetation.
Another common issue with PV plants is the presence of rodents and their negative effect on cables
integrity. In this case, we found out that most of the
rats on site were actually introduced at construction
stage through the containers used to deliver the
different pieces of equipment.
Suitable preventive measures include therefore a
more careful control of this specific issue at the
equipment delivery stage and the use of reinforced
cables to ideally withstand the bites.
At the operational stage, additional measures may
consist in intensifying the frequency of pest control
routines to mitigate access by animals and filling
the cable connection pits with sand in order to
prevent theft of cables. (See Figure 11)
In some instances the preventive measures may
actually clash with specific permit requirements.
At the Montalto di Castro Plant, the operating
permit required the plant owner to create holes
in the fence in order to allow land continuity for
the passage of local fauna, typically medium-sized
animals. Once again, having a solid relationship
with the local authorities proved to be very helpful
and a solution was finally reached. In fact, we were
able to demonstrate, through a well-documented
photographic survey, that there were already
enough pathways through the fence, naturally created by small soil settlements or drainage ditches,
and therefore no additional work was necessary.
Figure 11: Sheep grazing in the panels area
In warmer climates, the temperature in the inverter
cabins, as well as in spare parts storage rooms, can
raise significantly thus reducing the efficiency of the
equipment, therefore it is advisable to design suitable air cooling system, especially for the former.
In order to be effective, the cooling system typically
needs to be of significant capacity, thus requiring
a high energy input. It is then critical to insure its
efficiency through an appropriate maintenance
program, suitably integrated in the O&M activities.
A possible optimization of the system design could
entail a proper management of hot and cool air
flows within the cabin, by considering the actual
heat transfer and flow direction between the equipment and the environment, in order to maximize
the air cooling equipment yield. In the photo below,
for instance, the hot air exhaust that comes from an
inverter is conveyed out of the cabin without mixing with the fresh air that comes from the cooling
system. (See Figure 12)
As a good practice during the operational stage,
the temperature in the cabins should be monitored
constantly and recorded through the SCADA system
so it can represent an early warning in case of
problems.
2.10Environment, Health and
Safety
There are potential environmental and health and
safety issues associated with the full project life
cycle that need to be addressed at all stages of development. In particular, we have identified oil spills
from the transformers and noise in the inverter
cabins as two of the most significant impacts to be
managed during the operation of the plant.
All transformers at some stages may be subject to
leaking, which can be prevented through proper
monitoring of their oil temperature, pressure and
level, possibly with the aid of an automated system
Figure 12: Air temperature management in the
inverter cabin
connected to the general control software, which in
turn leads to a proper plan for routine maintenance.
We actually experienced a few oil spills from transformers, but a suitable containment system had
been designed in the space under the cabins which
allowed us to manage the issue properly through
the planned disposal of the resulting waste.
With reference to specific health and safety
hazards, the inverters noise may be quite high,
especially in specific periods of the day and of the
year. The exposure of the O&M operators when performing activities inside the inverter room should be
carefully controlled, through a proper assessment of
the actual equipment emissions. In our case, after
having identified the issue, we requested specific
personal protection equipment to be included in the
contractor’s health and safety plan.
THIS ARTICLE WAS PRESENTED AT SOLAR POWER-GEN 2013 AND HAS BEEN REPRODUCED WITH PERMISSION FROM Solar POWER-GEN. THE LAYOUT HAS BEEN CHANGED FOR THE PURPOSE OF THIS REPRINT.
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2.11Stakeholder management
Considering the local context, it is always advisable
to proactively engage and involve the local community and key stakeholders in order to keep them
informed on the plant development and operation
at all stages, build positive, trusting relationship
with the community and relevant authorities,
provide adequate avenues for community feedback
and ensure social issues are identified at an early
stage, managed and, where feasible, resolved.
Proactive and consolidated stakeholders communication lines can definitely improve the management
of a number of issues during the plant operation.
In terms of dealing with local authorities and regulators, general administrative procedures, as well as
contingencies and emergencies, can be managed in
a much more straightforward way if the quality and
reputation of the plant operator allow establishing
a relationship based on trust.
The same holds true for communities or neighbours
around the plant, where favourable and personal
relationships can lead to sharing of information that
would not be available otherwise and to peaceful
resolution of minor conflicts.
In the case of the former cattle-track described earlier, the situation became even more complicated
since the authorities had previously authorized
another plant to place its connection line under
the cattle-track. The other plant’s EPC contractor
was under a tight schedule to connect the system
in order to maximize revenues. Thanks largely to
solid relationships held with the local authorities we
were able to avoid the positioning of the line under
our plant by the other plant’s EPC contractor, who
could only obtain authorization to modify its route.
Another example of the use of a proactive and
positive relationship with the authorities was given
earlier on, when presenting the issue of having to
insure the land continuity through the plant for the
local fauna.
We were also able to witness that if local contractors and citizens are engaged in the operations,
the community will be happy to help if needed. For
example, as mentioned earlier, the previous owners
of some plots of land were shepherds. We agreed
with them to let their sheep graze inside the plant.
This gives many advantages to the operation of the
plant, since by controlling the height of the vegetation in such a sustainable way, the risk of fires or
panel shading is greatly reduced. Moreover the
shepherds and other local people typically provide
useful feedback about the local situation and its
evolution.
3.0CONCLUSIONS
Our experience in the assessment and supervision of the operation of large scale solar farms is
presented through the case study of the 51 MW PV
plant in Montalto di Castro in Italy.
This case shows that an integrated approach to
planning, execution and monitoring of the activities
can lead to an optimal performance of the plant.
The integration should be accomplished throughout
the project lifecycle phases (siting, development,
design and operation) and across the different
tasks within each phase, in order to identify all the
possible synergies, thus minimizing the risks and
leveraging the opportunities.
All the O&M activities can be recognized as related
to upstream lifecycle phases and should be properly
considered at the relevant stage.
For instance, a proper response to extreme weather
events implies the consideration of the associated
issues at the siting and planning stage, through
the assessments of the risk and the consequent
design mitigation measures, and the presence of
an adequate response plan in terms of emergencies
and repair procedures.
In the operation phase, it would still be possible
to address most of the critical issues presented in
the paper. Periodic audits of the plant can help
identify weak points in the systems or margins for
their improvement, consequently finding effective
solutions.
Such audits can be run at a qualitative level by
conducting reviews of the design and operational
documentation, including historical performance
data and records of anomalies, visual inspections of
the plant systems, assessments of the operational
activities and plans in place, random testing of
representative electrical components and direct
measurements of key plant performance indicators.
Critical issues can then be reviewed at a deeper,
more quantitative level with further targeted testing and development of specific analytical models.
Based on our international work on PV plants, we
can conclude that many of the concepts and practices that have been presented in this paper, suitably adapted for general context and site specific
conditions, are applicable to diverse and different
contexts, including similar large scale developments
in the US.
In fact, based on the history of PV plants in Europe,
a large overall capacity of PV plants could be
developed in a relatively short time period, over 2
to 3 years, but will have to be operated effectively
for a much longer time, in the order of 20 years,
during which period the existence and application
of sound plans and practices will be able to effect
the real success of the project. Thus, a thorough
planning, execution and monitoring approach to
O&M activities will optimize plant performance
and maximize production yield, with reference to
the potential capacity given by the engineering and
design features of the project.
About Golder
As a global, employee-owned organisation with
over 50 years of experience, Golder Associates is
driven by our purpose to engineer earth’s
development while preserving earth’s integrity.
We deliver solutions that help our clients achieve
their sustainable development goals by providing a
wide range of independent consulting, design and
construction services in our specialist areas of
earth, environment and energy.
For more information, visit golder.com.
THIS ARTICLE WAS PRESENTED AT SOLAR POWER-GEN 2013 AND HAS BEEN REPRODUCED WITH PERMISSION FROM Solar POWER-GEN. THE LAYOUT HAS BEEN CHANGED FOR THE PURPOSE OF THIS REPRINT.