PUTTING SOLAR PANELS ON WATER

Although very helpful as far as carbon neutralisation is concerned, land acquisition for putting Solar Plants is a very costly affair these days. Thus, the latest trend is putting floating solar plants. However, there are other risk factors involved. Can we overcome those?

Solar energy is plentiful, clean and green, and is key in reducing carbon footprint. The conventional renewable energy farms like solar and wind needs space – a lot of it. We require about  five acres of land  for setting up a one MW solar photo-voltaic plant on ground.

There are many advantages in going for ‘Floating Solar Power Plants’. The main advantage is that they do not take up any valuable land consumption, except for the limited area required for electrical panels and grid connections.

The Floating Solar Panel Structure provides a large area of Shade for the water – and thus reduces evaporation of water from these reservoirs / lakes /dams. This is particularly beneficial to areas susceptible to draught, since continuous water loss to evaporation over a time contributes to water shortage. The shades provided by these Floating Solar Systems also help in reducing the presence of algae blooms in bodies of fresh water, thus improving the quality of water.

The significant benefit of Floating Solar Plant is that it does not take up the valuable space on land, meaning that it can be used for other purposes such as agriculture, Construction of Buildings, development of Industry etc.

Another advantage is that the presence of water exerts a cooling effect, which improves the performance of Solar PV Panels by 5-10%. Solar PV Panels being themselves water proof, rain or floating water can’t damage them.

Floating solar PV system on Tengeh reservoir

Singapore is one of the smallest countries in the world, and it is also among the biggest per capita carbon dioxide emitters in Asia. Renewable energy is a challenge for this country with no rivers for Hydro Electricity & no wind that is strong enough to power Wind Turbines. In a bid to tackle climate change, the country is building one of the world’s largest floating solar farm.

The conventional renewable energy farms, like Solar and wind, need space – a lot of it. This important factor places a bottleneck on the green energy ambitions of Singapore, an island state with a population of 5.63 million and a land area of 724 sq. kms. The high levels of urbanization and the towering metropolis are not favourable to solar and wind farms.

Singapore’s National Water Agency, & Sembcorp  Floating Solar Singapore, which are partnering  to  build a 60 Mega Watt- peak (MWp) Floating Solar PV system on Tengeh  Reservoir,  with 122,000-panels solar farm, will be one of the biggest in South-East Asia covering an area, the size of about 45 football pitches.(Fig.1). Despite there is some  delay in  the  project execution due  to  the  pandemic  situation, it is likely  to  be  commissioned before end  of 2021.

Fig. 1: 60MWp floating solar PV system on Tengeh Reservoir, Singapore…

To ensure operational excellence, sustainability and safety of the large scale project, every component of the Floating Solar System has been carefully chosen & designed. This includes the need to maximise energy generation, minimise environmental impact, and be durable enough to last its entire life span of 25 years.

Another very important factor in selection of this project was to overcome Singapore’s Land Constraints in pursuit of greater renewable energy generation, thus contributing to the national climate change mitigation. The aim is to reduce reliance on fossil fuels, cut emissions and build climate resilience. The Singapore  Government recently unveiled a wide-ranging ‘green plan’ that includes steps such as planting more trees, reduce  the amount of waste sent to landfills and build  more  battery charging points to encourage the use of electric cars.

The energy generated from  this floating Solar project is sufficient  in greening the Singapore’s water works, that is, the energy  generated is sufficient  to meet  the  needs of Singapore’s water works, which will be one of  the few in  the  world to  be  100% green. This is equivalent to the reduction of carbon emission equivalent to 7000 cars.

The floats are made of UV-resistant High Density Polyethylene (HDPE), and the solar panels are made of double-glass modules to increase their durability and life span. PV panels are tilted for efficient energy generation and rainwater drainage. They are also coated with anti-reflective materials to minimize glare. The floats are anchored to the reservoir beds using steel cables / chains.

Currently, many countries are going in for Floating Solar PV projects. Kyocera Corp. of Japan, has come up with a smart way to build and deploy floating solar power plants without gobbling up precious agricultural land in space-challenged Japan, by building the plants on freshwater dams and lakes. This Japanese 13.7 MWp floating photovoltaic plant sits behind the Yamakura Dam at Ichihara in Chiba Prefecture. It can power nearly 4,700 homes and is saving more than 7,800 tonnes of CO2 a year. It consists of 50,000 solar panels.  It is located in 13 ha of water area. This project, which is Japan’s largest floating PV power plant, was inaugurated by Kyocera in March 2018 at the Yamakura Dam in Ichihara City, Japan. (Fig.2)

Fig. 2: Floating Solar PV Plant – Yamakura Dam, Japan…

Unfortunately,  during  the  second  week  of  September 2019, part  of  the  above Floating Solar  Plant  at Yamakura Dam  was  damaged  by the  125 mph  wind  brought by the  Typhoon Faxai. Then it caught fire. It  was suspected that   the  high speed  wind,  tore  several  floating  modules  of the  project and stacked them one above the other. This is suspected to be an anchor failure. The  fire  fighters  were  of  the  opinion  that the  contact between  live loose panels and those that remained moored to mounting structures, might have  caused  short circuit  / overheating of  the modules, creating the conditions for a fire.  This  incident need  to  be  kept  in  mind  when  planning  Floating Solar PV Plants  in  areas  experiencing high speed winds & typhoons. Properly  designed and strengthened anchoring  of  the  panels is a  must  to  avoid  such  incidents. (Fig.3)

Fig. 3: Image: Solar Power Plant Business /Nikkei Business Publications, Inc…

After the outermost row had ripped off, the wind-facing edge did not have any ballast anymore to counter uplift from wind. The modules and floaters began to curl-up with the result of an electrical fire. (Fig.4)

Fig. 4: Japan’s largest floating PV plant catches fire after Typhoon Faxai impact…

India’s biggest floating solar power plant is coming up in Telangana

National Thermal Power Corporation (NTPC) has a 2,600 MW Super Thermal Power Station at Ramagundam, Telengana. This  project  has  its  own  water  Reservoir meeting  the  requirements  of  the  Thermal  Power  Plant.  Now  NTPC is setting up India’s biggest Floating  Solar Power Plant  in  this  reservoir,  with  a  capacity  of 100 MW,  which  is  expected  to  become   operational in Telengana soon. This floating solar project, spread over 450 acres, will have 4.5 Lakhs PV panels, at a cost of Rs.423 crores.

Conventional Solar PV  plants  when  located on land, require about five acres of land per MW capacity. Given the challenges in land acquisitions, NTPC is going for the floating method.Further, NTPC is planning a 92 MW Floating Solar plant at Kayamkulam Gas plant in Kerala, as well as a 25MW Floating Solar Plant at Simhadri Power Plant in Vizag. This is in line with our country’s commitment towards development of Renewable Energy.  As  per NTPC  officials, setting up Floating Solar units on water  bodies and huge  reservoirs help them in  cutting  down  on  the  costs.  Floating Solar Units prove to be cost effective when compared to Ground- Mounted solar plants.

NTPC  in  its  enthusiasm  to  expand its power generation  by  introducing  Floating  Solar  PV  Projects,  has  to  keep  in  mind  the damages  caused  by  the  typhoon  in  Japan – and ensure  that  proper  anchoring  designs are  followed  in  the  Floating Solar  Plants  to  prevent  such  mishaps.

Hybrid systems

According  to  the  researchers at the US Department of Energy’s National Renewable Energy Laboratory (NREL),  hybrid systems of Floating Solar Panels  &  Hydro Power Plants  will  hold the technical potential  to  produce a  significant portion of the  electricity generated annually  across  the  globe. Floating solar farms on existing hydropower reservoirs could cut solar costs and meet 40% of the world’s energy needs, they found.

Following are  the  technical  potentials of  the hybrid  systems using Hydro Power  Reservoirs for Floating PV panels,  instead  of using  lakes  or  ponds.

The most important one is that the solar power system can use the existing infrastructure and transmission lines of the hydropower facility, which cuts capital costs. Plus, the two technologies can balance each other since solar power has the most potential during dry seasons – while rainy seasons are best for hydropower. So, at a hybrid plant, operators could store excess solar power using pumped storage hydropower, where electricity is used to pump water to a higher elevation.  (Fig.5)

Fig. 5: A schematic of a hybrid floating PV & hydropower system…

Usage of Floating Solar  PV Panels  on  the  reservoirs of Thermal  Power  Plants, as  conceived  by  NTPC, can  also  form  an Hybrid  version  which  will  save  lot  of  land  acquisition costs  as well as develop Renewable  Energy to  cut  down  Carbon  Emission. “Putting Solar Panels on Water Is a Great Idea—Yes, it will work.”


 

 

 

 

C.V. Govinda Raju is a former Executive Director of Karnataka Vidyuth Karkhane Ltd., Bangalore & the Former President  of  ISPAT  group of Company.

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