New requirements for a better sustainable energy policy around the world is easy to observe, many projects in sustainable energy are developed wherein the academia works together the authorities and commercial firms such as electrical grid utilities. In distribution transformers one of the suggested solutions is to replace mineral oils used as dielectric and coolant for natural ester fluids, they provide improved technical properties making them a safe substitute of mineral oil. Natural esters are based on clean technology in order to guarantee requirements from utilities. The main goal of the present paper is to present a technical-economic analysis obtained from five years of applications of oil-immersed transformers using natural ester fluids in Colombia. The methodology considers forty-four oil-immersed distribution Transformers, a half use mineral oil and the other side use natural ester, operating under the same load regime. Results evidenced the feasibility of implementing this technology because the costs are very similar and the reduction of risks and environmental impact is considerable.

Compressed air is one of the most widely used application energies in the industry, such as good transportability, safety, purity, cleanliness, storage capacity and ease of use. In many countries, compressed air systems account for approximately 10% of the industry's total electricity consumption. Despite all its advantages, compressed air is expensive, only between 10% and 30% of the energy consumed reaches the point of final use. Energy is lost as heat, leaks, pressure drop, misuse, among others. Energy efficiency measures such as: reducing compressor pressure, lowering air inlet temperature, adequate storage capacity, recovering residual heat from the air compressor and reducing leakage, can produce energy savings between 20% and 60%, with an average return on investment lower than 2 years. This paper analyzes the main energy efficiency measures that can be applied in the CASs, the potential energy savings, implementation costs and return rate of each of them are being calculated giving a necessary tool for companies in their objectives to reduce greenhouse gas emissions and energy consumption.

Compressed air (CA) is one of the most common systems used in industry. In countries such as Australia, Italia, France, China and USA, energy consumption of CA systems (CASs) contributes about to 10% of the total electricity consumption in industry. In Colombia, this value reaches 8%, highlighting the textile industry, with a 24% of consumption. Despite of all its advantages, CA is expensive, between 10 and 30% of consumed energy reaches the end-use point. Improvements to CASs can achieve between 20 and 60% of energy savings, with pay-back periods lower than two years. These are the reasons that they can be considered as one of the main targetsystems while planning energy efficiency actions in industry. Colombia through different strategies has proposed to implement a group of measures to improve energy efficiency and reduce electricity consumption to 2021 around 7%. Implementation of good practices in CASs is one of them. This paper is showed the share cost, electricity consumption and the savings potential of the CASs in the different divisions of the Colombian manufacturing sector, the main sectors to be involved as well as the potential savings and reduction of dioxide carbon emissions.