Mineral and Vegetable Transformer Oils Equally Green

Tag: Overhead Conductor

Vegetable transformer oils are often perceived as more environmentally friendly than mineral oils. But is this really true? To find the answer, one needs to make a thorough investigative comparison. A useful tool for such comparisons, life cycle assessment (LCA), can be used to examine the cradle-to-grave environmental consequences of making and using products. Dealing with environmental impact categories such as acidification potential, global warming potential and resource depletion, LCA is a continuing process, and new findings force users to frequently re-evaluate studies and results.

Unfortunately, there are no LCA studies comparing mineral and vegetable ester oils for use in transformers. However, the production of mineral oil and rapeseed oil and their use in hydraulic fluid has been studied, as has the environmental impact of transformers. From these, one can assess the environmental influence of the entire life cycle of mineral and vegetable transformer oils.

Two LCA studies comparing the environmental impact of the production of mineral and rapeseed oil show slightly differing results due to the use of different limitations and LCA models. However, both studies indicate the overall impact does not differ much between the production of mineral and rapeseed oil. Some find this surprising, but they may not have considered all factors involved.

The production of rapeseed oil requires seedbed preparation, sowing, fertilizing, crop protection (pesticide use), rapeseed growth, harvesting, drying and storing, and crushing or extraction and refining. For mineral oil production, drilling and extraction of crude oil is followed by refining. These contrasting production methods have very different effects on the environment. The main difference between mineral oil and vegetable oil is of course the raw materials used, but the cultivation stage, with the use of fertilizers and pesticides, and the extensive further processing involved in vegetable oil production affect the results, making vegetable oil production more energy-intensive.

How the oil is used will also influence its environmental impact. It can be argued that, since almost all used transformer oil is reused as fuel, it gives back some of the energy consumed during production. Nevertheless, if the combustion or final degradation of oil is included this will have a large negative impact on the global warming potential and the total environmental impact of mineral oil, especially in comparison to vegetable oil that is made from renewable resources and therefore not burdened by this. The performance of the oil in transformers and how this affects the life of transformers will also contribute greatly to its environmental impact.