CASE STUDY
Foreword from the Editor in Chief:
It amazes me to see how rapidly things can change in the power industry. Take for example the term “Floatovoltaics”. It sounds like something out of a Star Trek movie. “Mr. Spock, prepare the floatovoltaics for landing on the surface of the planet.” But as the word suggests, it is a series of floating solar panels used for making solar farms less land intensive. And given the vastness of the oceans, lakes or seas, that might overcome the objection “Not in my backyard, please.” As this amazing article details, the world is changing to newer and greater demands for alternative, non-fossil fuel generation.
As the world continues its quest to source more renewable energy, the latest frontier is adding solar fields above water. Installing solar fields on water provides new surface areas for power generation once only reserved for land use.
However, as the industry considers the added environmental risks and implications of integrating liquid immersed transformers into these installations, more-and-more are turning to natural ester units that not only mitigate the impacts in case of a spill in water contamination, but also deliver superior load capacity, longevity and lower costs.
Such floating solar projects are mostly taking advantage of water surface in areas which were not explored otherwise. The performance of the photovoltaic panels is favored by the cooling provided by the water and impacts on the environment are kept as low as possible. Floatovoltaics cost less to install than traditional land-based solar panels because there is no need to clear the land or treat the soil.
The solution avoids land expropriation, does not interfere with the existing ecosystem as much, especially when using lakes formed by the hydropower dams, and allows for using the same substations and transmission lines from the existing powerplant. As previously mentioned, covering the surface of one hydropower dam lake would lead to peak generation that is 1.6 times higher than the power generated by the turbines of the power plant – so, at a fraction of the cost of the investment for a hydropower plant, its peak capacity could be more than doubled.
In fact, among the more than 60 countries pursuing the installation of Floatovoltaics, 35 are home to an estimated 350 operational systems, which up until the end of August 2020 had a cumulative capacity of approximately 2.6 GW. Although still considered a niche, floating photovoltaic (FPV) is projected to grow at a rate of more than 20% in the next five years. And the use of natural ester in transformers has the tendency to become a new standard solution for these applications.
Derived from 100 percent renewable plant sources, Cargill produces its FR3 dielectric fluid, which has already been used by several utilities and industrial customers as the dielectric fluid for their transformers for over 20 years.
Floating photovoltaic is projected to grow at a rate of more than 20% in the next five years, and the use of natural ester in transformers has the tendency to become a new standard solution for these applications.
The fluid has also been seeing significant growth as the industry brings more floating solar projects online. In 2020 alone, the global agricultural and bio-industrial firm has been involved in the first floating solar fields in Brazil, China and India.
In all these projects it was decided to use step-up transformers filled with Cargill’s natural ester. This option also suits the utilities that seek to minimize the risks and maximize the profits. As in any process from a traditional solution that has been in use for over a hundred years to a new technology, the transition is being performed very carefully, as it should be. Transformers have a useful life expectation in the range of three decades or more, and the overall replacement ratio is estimated to be around 1% - 2% a year. So, gradually but continuously, the electrical system is being converted, one transformer at a time.
Making Waves in China
The CGN’s floating solar project in Hunan Province is 100 MW. Considering 1,500 h/year of the equivalent full-loading cycles, the plant produces 100 MW x 1500 h = 150,000 MWh of electricity per year, or around 411 MWh per day. The investment in solar projects in China is about 4.5 CNY/W, or 661 USD/kW. Depending on the project type, some of the projects are backed by government allowance of approximately 0.18C NY/kWh of electricity produced. However, as the solar industry in China develops and the market plays a bigger part, most projects do not have that allowance and investors are paying more and more attention to cost.
“The advantages of natural ester are already recognized in China,” said Revin Wang, Cargill Technical Application Manager in China. “Furthermore, we can see important activities related to development of national standards, such as the group of standards for natural ester filled transformers in general requirements, technical parameters, transformer assessment using dissolved gas analysis (DGA), operation and maintenance parameters and economic analysis guides in addition to the very relevant fire protection guide.”
In addition, utilities like State Grid Corporation of China (SGCC) and China Southern Grid (CSG) have published corporate standards requiring their distribution transformer bids to be focused on natural ester filled units. In several provinces SGCC already started pilot bulk tenders for natural ester filled distribution transformers. CSG is also working on a pilot project of a large natural ester filled power transformer at the voltage level of 220 kV and started an R&D project for 550 kV natural ester filled transformers.
These advancements are aligned with the government-led policy of green development that will leverage the adoption rate of natural esters, such as FR3 fluid, to become the main insulating liquid used in new transformers in China.
Since the beginning of its commercial use about 25 year ago, no pool fire has ever been reported in any FR3 filled transformer.