ORC stands for Organic Rankine Cycle, one of the best technologies nowadays to use renewable resources. Exergy, Italian company leader in developing solutions for power production from renewable resources, has created and patented the Radial Overflow Turbine, a turbine which is by far more efficient and has better performances if compared to “old” steam turbines used to produce green energy. How does this system work and why is it so important, even in our daily life?
The purpose of the ORC system is to generate power from various heat sources. Its working principle is a lot like the one behind the Clausius-Rankine Cycle, with some differences. The biggest one is the fact that the Clausius uses either water or steam as its working fluid. The ORC, on the other hand, operates exclusively by using organic fluids. These have a lower boiling point and are characterized by higher vapor pressure. This results in the ability to use lower temperature heat sources for the production of electricity.
There is a variety of organic fluids that can be used to power an ORC system. Since not all heat sources are the same, these substances need to be carefully chosen before they are introduced in any particular ORC cycle. The main factors here are the different thermodynamic properties of each heat source. Choosing the right organic substance means making the system a lot more efficient than it could be otherwise.
Why are ORC systems so important?
We have already established that they are capable of generating electricity by using heat sources at a lower temperature. By saying this, we refer to sources with temperatures ranging from 80 to 350°C. Before Organic Rankine Cycle systems, such heat sources were wasted because there was no technology capable of exploiting them.
Now that such technology exists, we can benefit from two equally important points of view. First of all, ORC-Units are able to utilize otherwise wasted energies from biomasses to convert them into power, which is a huge step forward. And second, we can use it to power plants that, due to their size, couldn’t have been powered by renewable energy before. Furthermore, ORC systems are valuable for a wide range of applications, including not only geothermal but solar, biomass and waste heat recovery applications.
Organic Rankine Cycles: A Brief History
Although the first patent on an organic Rankine cycle was filed in 1892, it wasn’t until the 1950’s that commercial applications began to emerge. During World War II, Germany developed a process called “Klima Technik” that utilized a closed loop organic Rankine cycle to generate electric current from natural gas. After the war ended, Klima Technik became known as the Lindenstruth plant, after its inventor, Dr.
Lindenstruth. The United States also experimented with this technology during the same time period, although no plants were ever built. In 1953, General Electric introduced their own version of the Lindenstruth system, which used a mixture of diethyl ether and water as the working fluid. GE eventually sold off the rights to the Lindenstruth patents to Honeywell International Inc., who then licensed them out to other companies including Mitsubishi Heavy Industries Ltd. and Toshiba Corporation. These licenses expired in 2000, at which point several new companies entered into licensing agreements with Mitsubishi Heavy Industries. One of these licensees is Energetics Corp., whose product line includes both open-loop and closed-loop versions of the Lindenstrut system.
In addition to being efficient, another advantage of using an organic Rankine cycle over traditional systems is that there are fewer moving parts. This makes maintenance easier and less costly. Another benefit of the organic Rankine cycle is that it can be operated without any external cooling source. Although some conventional power cycles require large amounts of energy to operate, the organic Rankine cycle requires very little heat input. As a result, the organic Rankine system has lower operating costs compared to most other types of power generation technologies.
Another type of thermal engine that utilizes an organic Rankine cycle is the Organic Electrochemical Power Source or OECS.
Working principle of the ORC
The organic Rankine Cycle is a thermodynamic power generation process that converts heat into mechanical work.
The Organic Rankine cycle is a thermodynamic process that converts heat into mechanical work. It was first described by the Russian scientist Nikolay Semenov in 1892, and has been used for power generation since then.
The first commercial application for an Organic Rankine Cycle system occurred at the General Electric Company’s plant in Schenectady, New York, where it powered electric generators from 1902 to 1912.
The ORC can be considered as a combination of two other well-known processes: steam engine and Brayton cycle.
FEATURES
• High efficiency: up to 90%.
• Very compact design.
• Simple installation.
• Easy start/stop control.
• Reliable performance over time.
• Can be used both as a primary and secondary source of renewable energy.
Capturing Waste Heat with Organic Rankine Cycle Systems
The ORCs have been around for more than 100 years, but they’ve only recently become commercially viable due to the development of high-efficiency organic working fluids such as ethylene glycols and propane derivatives.
The use of organic fluids to convert waste heat into useful work is an old idea dating back at least as far as the 19th century when it was first proposed by Nikola Tesla in his patent application for “a method of generating electric current” filed on May 1st, 1891. The basic concept behind this technology has been around since then but only recently have we seen significant progress towards commercialization.
What is the difference between Rankine cycle and Organic Rankine Cycle
Rankine cycles are used in power generation plants where steam is generated from water by boiling it at a higher temperature. The heat energy produced can be converted into electricity or mechanical work using turbines. In contrast, an organic rankine cycle uses a fluid that boils at lower temperatures instead of water. This allows you to use less expensive equipment and also reduces corrosion problems associated with metal parts being exposed to hot water.
In addition, because there is no need to boil water, this type of system has much better thermal efficiencies compared to conventional systems. For example, when converting 50% of the chemical potential energy stored in coal into electrical energy, the overall conversion efficiency will be about 30%. However, if we were able to convert all of the chemical potential energy into electricity without producing any waste products, then our overall conversion efficiency would increase to 60%, which is close to what nuclear reactors achieve.
