Frequently
asked
questions

General Questions

How to identify water bodies on which Hydrelio® can be installed?

Ciel & Terre wishes to preserve the environment and recommends studying floating PV projects on artificial water bodies.
Ideal water bodies conditions are:

  • Regular shape
  • Limited depth and water level variation
  • Easy access by road for logistics
  • Space on the banks for construction and storage
  • Proximity with the grid is a plus for the project development

What is the yield compared to ground PV plants?

Thanks to water proximity, a cooling effect enhancing the energy production can be expected.
The Solar Energy Research Institute of Singapore (SERIS) observed a PV panels temperature 3 to 10 degrees lower on floating PV plants compared to rooftop systems in Singapore with a yield increase of 5 to 10%.
The Solar Energy Application Centre (SEAC) recorded a decrease up to 6 degrees in PV panels temperature in the Netherlands with a yield increase estimated at 2 to 3%.

What is the installable capacity per hectare?

A 1 MWp floating PV plant has a footprint of approximately 1 ha on the water body.
Distance between the floating arrays and the banks is required which means that the maximum coverage ratio of the water body is 65% in average.

What is the whole process for the Hydrelio® purchase?

After filling in the contact form , you will be put in contact with the closest Sales Department which will help you establish the technical and financial feasibility of your project.
The Sales Department will make the link with Ciel & Terre’s Engineering team to execute the detailed anchoring design.
At the project implementation phase, the Hydrelio® floating system is delivered. Then, an on-site training session will be done by an Engineer of Ciel & Terre to explain the assembly process.

Where can I buy Hydrelio®?

You can contact the closest office to your project location by visiting the Contact page or by filling in the Contact forms .
Ciel & Terre or one of its partners will then contact you back to study your project.

Where is Hydrelio® manufactured?

Hydrelio® parts are manufactured in France, the USA, Brazil, Japan, South Korea, Thailand, India, Malaysia, Taiwan and China. For more details, please, refer to the manufacturing page.
For large scale projects, Ciel & Terre may consider a local manufacturing.

What are the selling points of the Hydrelio® products?

Hydrelio® and Ciel & Terre offers different advantages such as:

  • References. Ciel & Terre is a pioneer in the floating PV market since 2011 and has the widest track record worldwide in terms of number of projects realized. This experience allows us to offer the most suitable technical advice and solutions.
  • Bankability. The Hydrelio® technology has been tested by third parties to ensure the quality of the system.
  • Market adapted solutions. Since its first floating PV pilot in 2010, Ciel & Terre has developed the Hydrelio® products and its technical services to adapt your needs. We now offer many options regarding products , plant configuration and anchoring solutions
  • Proximity. Ciel & Terre has 9 offices, 3 licensees and 10 manufacturing sites all over the world to provide a support as close as possible from its Clients’ project.
  • Technical assistance. Throughout the project development and implementation, Ciel & Terre will help you and assist you technically with a wide range of services.
  • Cost-competitiveness. Ciel & Terre solutions have been developed to be price-competitive on their market while ensuring the quality of the materials and products.

What is the delivery time?

Delivery time will vary depending on your project location and the availability of the production lines.
The floats are produced in just-in-time flow and a minimum of 8 weeks after the order placement is to be expected before the first delivery on the site.

How many floats can fit into one container?

Using 370 W panels, a container can approximatively transport an average capacity of 67 kWp for Hydrelio® aiR and a capacity of 41 kWp for Hydrelio® Classic in average.

Do banks financially support floating PV projects?

Yes, most of floating PV plants built in the world has been financed and supported by banks including some of the world’s top-ranked banks.
For example, in Japan, projects have been financed by both national and regional banks, and in France, the 17 MWp O’MEGA1 project has been financed with around €12 million of non-recourse financing.

What is the product standard warranty of Hydrelio®?

Ciel & Terre gives a 10-year warranty for the Hydrelio® system, to cover replacement and repair of any potential defective component of the Hydrelio® system. An extension of additional 5-, 10- or 15-years warranty can be discussed.

How is O&M done on the floating PV arrays?

Maintenance walkways between PV panels rows allow operators to move easily on the floating PV plant to do O&M tasks such as PV panels cleaning and parts replacement.

Product

What are the components of Hydrelio®?

Floats are made of HDPE (High Density Polyethylene), connection pins are in Polypropylene and PV panels fixations in Aluminum. Additives are added to the raw materials to ensure the product lifetime.

Can the color of the Hydrelio® floats be changed?

Floats colors cannot be changed.
The grey color of the floats allows UV resistance and light reflection.

What are the possible tilts for Hydrelio®?

The Hydrelio® products offer several tilts to the floats to answer different markets’ needs. To see the available options, find more information on the Products page .

What is the buoyancy of the Hydrelio® floats?

The floats have been designed to enable operators to move easily on the floating PV array and safely carry out O&M.

What is the yield of floating PV compared to ground PV plants?

Thanks to water proximity, a cooling effect enhancing the energy production can be expected.
The Solar Energy Research Institute of Singapore (SERIS) observed a PV panels temperature 3 to 10 degrees lower on floating PV plants compared to rooftop systems in Singapore with a yield increase of 5 to 10%.
The Solar Energy Application Centre (SEAC) recorded a decrease up to 6 degrees in PV panels temperature in the Netherlands with a yield increase estimated at 2 to 3%.

Does Ciel & Terre have a solution to prevent bird excrements?

Some solution like lasers or distress sounds have been identified and should be studied case by case. However, as this is a specific matter to each site, Ciel & Terre does not recommend a specific solution.

What tests have been conducted to determine the Hydrelio® resistance?

The Hydrelio® floats and its fixation have been tested with mechanical tests (fatigue and static) and wind tunnel tests by 3rd party institutes.

Is Hydrelio® certified?

As floating solar is a recent concept, there is no certification regarding the floats yet. Ciel & Terre bases its tests protocols on relevant standards and has, for example, obtained certifications for drinking water compliance.

What is the lifetime of Hydrelio®?

Hydrelio® is designed to withstand a period of over 25 years.
The floats can be recycled at the end of their lifetime since the HDPE and aluminum are recyclable.

How is O&M performed?

Maintenance walkways between PV panels rows allow operators to move easily on the floating PV plant to do O&M tasks such as PV panels cleaning and parts replacement.
In addition to operation, preventive and corrective maintenance tasks must be considered.
O&M manual, including checklists and controls, is delivered to client prior to plant operation.

Site conditions

How to identify water bodies where floating solar can be installed?

Ciel & Terre wishes to preserve the environment and recommends studying floating PV projects on artificial water bodies.
Ideal water bodies conditions are:

  • Regular shape
  • Limited depth and water level variation
  • Easy access by road for logistics
  • Space on the banks for construction and storage
  • Proximity with the grid is a plus for the project development

Can Hydrelio® be installed on drinking water ponds?

Hydrelio® floats are made of HDPE (High Density Polyethylene) which has a neutral impact on water.
Hydrelio® is compliant with the standard BS 6920:2000 (odor & flavor test for non-metallic material for use with drinking water), which proves that it is suitable for contact with water intended for human consumption.

Can Hydrelio® be installed on salty waters?

The floats are made from HDPE (High Density Polyethylene) and salty water has no effect on this material. The raw materials of metallic pieces will be chosen to withstand salinity. Ciel & Terre is developing a solution that can withstand salinity.
The PV panels and electrical equipment will also need to resist these conditions.
An appropriate O&M plan, especially regarding the electrical parts, will have to be considered.

Can Hydrelio® be installed on polluted waters?

A water quality analysis will be required to check that Hydrelio® can be installed safely. The EPC should also check the feasibility of the project regarding the electrical equipment.

Can Hydrelio® resist to high winds?

Hydrelio® is designed to withstand winds up to 210 km/h (130 mph).
The floating PV plant is designed case by case and its anchoring is defined with the Client, according to site conditions.

Can Hydrelio® be installed on oceans or seas?

The Hydrelio® system is not suitable for harsh offshore conditions. However, it can be installed on closed seas or lagoons where water current, tide and waves are limited.

Can Hydrelio® be installed in cold environments (frost and snow)?

Hydrelio® has been installed in regions such as Colorado, Sweden and South Korea and no damages due to cold climate have been noted.

What happens in case of drought?

In case of droughts, floats will lie on the bottom of the water body without being damaged.
If the water body bottom is not flat or has some obstacles (pipes, rocks…), the site is not eligible due to the risk of damage to the floating system.

Can Hydrelio® be installed if there is a risk of overflow?

Risk of overflow is not a problem for Hydrelio® if the project is located in an area protected against drifting obstacles such as trees.
However, Ciel & Terre must be informed of potential overflow in order to consider it when executing the anchoring design.

Is Hydrelio® compatible with fishing and fish farming?

An environmental study by a specialized consultant will allow Ciel & Terre’s engineers to design the floating PV plant to preserve fishing and fish farming.

Environmental impacts

Does Hydrelio® prevent algae growth?

Covering a pond with Hydrelio® floats means that less sunlight is available for algae to grow which reduces their proliferation.
An environmental consultant can help you assess the impact.

Does Hydrelio® prevent evaporation?

Since a significant part of the water body will be covered or shadowed by the floating PV plant, reduction of the evaporation is expected but difficult to quantify as it is specific to climate conditions.

What is the impact of Hydrelio® on aquatic life?

Both light and heat are expected to decrease creating a new balance for the reservoir’s fauna and flora. The specific impacts on a site can be investigated with the help of a local environmental impact’s specialist.
Environmental consultants usually highlight that under 50% coverage, the floating PV plant impact is limited.

What is the impact of Hydrelio® on water quality?

Hydrelio® floats are made of HDPE (High Density Polyethylene) which has a neutral impact on water.
Hydrelio® is compliant with the standard BS 6920:2000 (odor & flavor test for non-metallic material for use with drinking water), which proves that it is suitable for contact with water intended for human consumption.

Are there any permanent effects of Hydrelio® on the site’s environment after the operation decommissioning the plant?

There are few permanent consequences on the site’s environment since Hydrelio® is made to be as neutral as possible.
During the decommissioning phase, the floating PV arrays will be dismantled easily on the banks.

Is Hydrelio® recyclable?

HDPE is a recyclable material; there is a set of profitable channels for the use of recycled HDPE. Aluminum parts are also recyclable.

Floating PV array design

Is there any limitation of size or capacity?

There is no limitation of size for a whole floating PV plant. However, because of anchoring reasons, there is a limitation for an individual solar array. Thus, big-scale projects are composed of several single arrays.
As an example, the 70 MWp project of Anhui Cecep (China) is composed of 13 floating PV arrays.

What is the buoyancy of the Hydrelio® floating PV array?

The floats have been designed to enable operators to move easily on the floating PV array and safely carry out O&M.

Can the floating PV arrays move and hit the banks?

Because it is anchored with several anchors on each side, the movement of the floating PV array will be limited. During the anchoring design execution, the Engineering team calculates the movement of the floating PV plant and ensure that it won’t hit the banks.

What happens when the water level drops?

The floating PV array and anchoring designs are carried out to adapt the water level variation. Due to the slack of the mooring lines, the floating PV array will move on the surface according to the magnitude of the water level variation.

What PV panels orientations are possible with Hydrelio®?

Depending on the products chosen, single and dual orientation (east-west) may be considered.
The dual orientation is set in a back-to-back way (/\ _ /\). This configuration avoids shadow on the PV panels and optimizes wind profiling.
Sun-tracking is not available.

Are all the PV panels compatible with Hydrelio®?

One PV panel is fixed on one single Hydrelio® float. Therefore, PV panels must respect specific dimensions.
Hydrelio® is compatible with most standard crystalline PV panels available on the utility-scale market.

What is the bi-facial PV panels performance on Hydrelio®?

Light reflection (albedo) is restricted behind the PV panels since the light reflection on water is of 8% only. Also, floats and surrounding PV panels shadows will partially block the light reflection from coming to the back of the PV panels. As a result, the back face of the PV panel will produce limited electricity.

Can frameless PV panels be installed on Hydrelio®?

Hydrelio® is primarily designed for framed PV panels but solutions to fix frameless PV panels can be found depending on the configuration. Frameless PV panels are, however, more fragile and thus, less adapted to floating PV plants.

How to install the electrical cables between the floating PV arrays and the banks?

Ciel & Terre recommends 2 options:

  • UV resistant-electrical conduits fastened on isolated floats between the floating arrays and the banks.
  • UV resistant floating conduit with electrical cables inside

Is it safe to have PV panels connectors in contact with water?

Ciel & Terre recommends reducing risks of contact with water by attaching DC cables to the PV panels before the floats are launched on water, by using stainless steel clips for instance.

What is the information required for the plant design?

For a first site assessment, GPS coordinates are enough. For a more detailed assessment, the following data are required:

  • Depth and water level variation
  • Bank’s slope angle

These data will allow the Engineering team to determine the exploitable surface.

Electrical specifications

How does water proximity impact electricity generation?

Water proximity is an advantage for your floating plant.
Water provides a natural cooling effect when the production is at its maximum. This reduces the temperature variation peaks thus provides a cooler environment. This cooling effect enables PV panels to generate more power.

How to do the PV panels cabling?

The PV panels cabling is done on the banks during the floats together and the PV panels together. They are then pushed strings by strings on the water.
Cables are connected behind the PV panels and fixed to the frame to avoid any contact with the water.

Is it safe to have PV panels connectors in contact with water?

Ciel & Terre recommends 2 options:

  • UV resistant-electrical conduits fastened on isolated floats between the floating arrays and the banks.
  • UV resistant floating conduit with electrical cables inside.

Does the material need to have a BOS specification (weight, IP code, size)?

Ciel & Terre recommends using at least IP 66 equipment. Regarding the weight, the lightest the equipment are, the better.
Because of permanent movement, cables suppliers recommend using copper cables.
Possible local regulations regarding electrical equipment must be observed by the EPC.

Are the inverters installed on the floating PV arrays?

In most cases, plants are designed with central inverters located on the banks and junction boxes on the floating PV arrays.
Depending on the product chosen, string inverters can be installed on the floating PV arrays. Ciel & Terre can advise the EPC regarding this matter.

How does grid connection work for floating PV plants?

The grid connection of a floating PV plant works the same way as a ground-mounted plant.

What are the recommendations for earthing/grounding?

Ciel & Terre recommends complying with local electric standard.
On the Hydrelio® products, PV panels grounding holes are used to do the grounding between PV panels.

How can I protect the DC cables?

Because of UV exposure and permanent movement of the floating PV arrays, Ciel & Terre recommends using UV resistant flexible conduits.

How to install the electrical cables between the floating PV arrays and the banks?

Ciel & Terre recommends 2 options:

  • UV resistant-electrical conduits fastened on isolated floats between the floating arrays and the banks.
  • UV resistant floating conduit with electrical cables inside.

Anchoring design

What is the information required for the anchoring design?

The anchoring design is executed at an advanced stage of the project planning, when the final floating array design is approved. The critical data to perform an anchoring design are:

  • Topography of the banks
  • Bathymetry
  • Water level variation (over the lifetime of the plant)
  • Waterflow data if there is any wind speed on site is calculated from national building code and approved by the client.

What are the possible anchoring systems?

Ciel & Terre Engineering team will advise the most relevant anchoring system among the following, depending on the site conditions and the site owner’s preference:

  • Anchoring at the bottom of the reservoir
  • Anchoring at the banks
  • Hybrid anchoring mixing banks and bottom anchoring

What type of anchors can be used?

Ciel & Terre proposes three main types of anchors: drilled anchors, percussive anchors and concrete blocks.
In the event that none of these can be used, other types of anchors can be studied.

How does water level variation impact the anchoring system?

The water level variation will generate slack or tension in the mooring lines, leading to array movement on the water surface. Consequently, an important water level variation means more movement and will require longer mooring lines.
Therefore, it is highly critical to perform the anchoring design on accurate and reliable data, so the anchoring system is safe at any water level.

Can the floating PV arrays move and hit the banks?

Because it is anchored with several anchors on each side, the movement of the floating PV array will be limited. During the anchoring design execution, the Engineering team calculates the movement of the floating PV plant and ensure that it won’t hit the banks.

Can the floating PV plant lie on the bottom of the reservoir?

In case of droughts, floats will lie on the bottom of the water body without being damaged.
If the water body bottom is not flat or has some obstacles (pipes, rocks…), the site is not eligible due to the risk of damage to the floating system.

What is the resistance of the anchoring system?

The anchoring system is designed to resist environmental loads: wind, waves, current.
Wind loads are calculated based on CFD, wind tunnel tests and wind speed calculated from national building code.
Wave loads are calculated based on array, reservoir layouts and wind speed.
Waterflow loads are calculated based on array and reservoir layouts and waterflow data.

Do the mooring lines rust?

Equipment must be chosen depending on site conditions. Usually, galvanized steel cables and polyester ropes are used to mitigate the risk of corrosion.

Does Ciel & Terre supply the anchoring and mooring systems?

Ciel & Terre’s typical scope of work is to define the location of each anchor and the applicable load on each anchor and each mooring line length. Anchoring material specifications are also provided. As the floating solar expert with a strong and unique experience in anchoring, Ciel & Terre provides you the support you need to ensure your floating PV plant is correctly anchored. Upon request, the supply and the installation of the anchoring system by Ciel & Terre can be discussed.

How is the floating PV arrays movement avoided during the works?

Final anchoring system must be installed prior to floats assembly and used during floats installation.
Additional temporary anchors and mooring lines are installed to maintain the arrays. The temporary anchoring system must be as resistant as the final anchoring.

Construction

How to mount Hydrelio® in case the banks are too steep?

If the banks are too steep, a wooden platform with scaffolding should be installed to reduce the banks’ slope for safety reasons.

What area is needed for construction?

There is no requirement in terms of installation platform’s size. However, the bigger the area is, the better. To reach a minimum efficiency Ciel & Terre recommends a 10m large area with a length equal to one string of PV panels.

How to assemble the Hydrelio® floating PV array?

The assembly of the Hydrelio® system is simple and is like a Lego-type construction.
Ciel & Terre provides:

  • A training session on site at the start of the assembly
  • Advice to increase the assembly efficiency
  • Construction drawings in order to ease construction for the installation team

How many people are needed to install Hydrelio®?

Ciel & Terre recommends a team of 15 persons. To improve the mounting rate for large-scale projects, multiple teams can work on separate areas.

Which tools are needed to install Hydrelio®?

No heavy or specific tools are required. During the planning phase, Ciel & Terre will provide a list of tools.
In addition, a boat and all the adapted protective equipment (PPE) such as life jackets, helmets, security boots, etc. are systematically required.

How is the Hydrelio® floating PV array launched on the water?

When two or three rows of floats and PV panels are assembled, they are pushed on the water manually to liberate space on the assembly platform.
Once a block is completed (the size of each block will be defined with Ciel & Terre during the planning phase), they can be towed by boat to their final locations and connected to the anchoring system.

How long does it take to install a Hydrelio® floating PV plant?

To install the floating array, including connection to the anchoring system and electrical cables installation, an average ration of 2.5 PV panels per hour and per worker can be considered.
For instance, a team of 15 persons would install about 12 kWp/hour

How do you avoid the Hydrelio® floating PV arrays moving during the work?

If the banks are too steep, a wooden platform with scaffolding should be installed to reduce the banks’
slope for safety reasons.

How to secure floating PV plants?

The plant can be secured by:

  • Video surveillance / CCTV next to the electrical installation on the banks
  • Fencing the land
  • Installing a floating barrier around the floating PV plant

Is there a training session for the installation?

Ciel & Terre provides a training session on site at the start of the assembly and gives advice to increase the assembly efficiency. Typical duration is 2 days and can be adapted depending on the EPC needs.