Mechanical and plant engineering

Orcan Energy – efficienty PACKs turn waste heat into clean electricity

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Using heat instead of wasting it unused – according to this motto, Orcan Energy's efficiency PACKs convert waste heat from engines, industrial and cooling processes into clean, CO2 -free electricity. They operate efficiently, in close proximity to heat sources and produce electricity at an extremely low cost of less than 5 ct/kWh. In the last five years, more than 500 plants have been put on the market, saving around 48,000 t of CO2 emissions in over 3 million operating hours in Europe alone. Since 2015, oil analyses from OELCHECK have been used in the efficiency PACKs to safeguard the high demands placed on the refrigeration compressors.

Rethinking a well-established principle

Based on the ORC principle, the Orcan efficiency PACKs function similarly to a steam power plant. ORC stands for Organic Rankine Cycle, whose mode of operation was developed by the Scottish physicist Rankine. However, an organic liquid with a much lower evaporation temperature than that of water vapor is used as the working medium. In a closed ORC system, this working medium is evaporated in a cycle and then condensed. The high pressures that build up in the process drive a generator to produce electricity. The special feature of the ORC process is that it can make heat usable for electricity generation even at a relatively low temperature level. However, previous plants based on the ORC principle could only be operated with relatively large amounts of waste heat and were sized accordingly. Orcan Energy rethought the proven technology and developed second generation ORC solutions with a high number of pieces at low cost. The patented efficiency PACKs are much smaller, require little maintenance and can be used flexibly.
With the help of the efficiency PACKs, clean electricity can be generated from waste heat, regardless of whether it is exhaust gases, exhaust air, exhaust steam, cooling or process water, or water from geothermal energy. They are suitable for any waste heat from 80 to 800 °C, and their components are accommodated in compact housings in a small space. Only elements, that have proven themselves many times over in industry, such as screw compressors used as compressors for refrigeration systems, are used.

Orcan Energy generally uses pentafluoropropane (R245fa) as the working fluid. It is neither flammable nor toxic and is also particularly efficient. In the evaporator, it is converted from its liquid to its vapor state. Evaporation takes place using thermal energy, which in the case of efficiency PACKs is basically waste heat that would otherwise flow unused into the environment. After the working medium has passed through the evaporator, it is fed as superheated steam to an expansion machine. The pressurized steam is used to rotate the screw expansion machine, which drives a generator that produces the electricity. The working medium flowing out of the expander at lower pressure is in turn liquefied in the condenser, brought to high pressure in the downstream pump and fed to the evaporator again. This closes the cycle and the process starts again. The electricity generated is consumed directly on site or fed into the power grid.

A tailor-made special oil – checked by OELCHECK

The efficiency PACKs are basically low-maintenance. Consequently, the working fluid, together with the oil for lubricating and sealing the expander, also remains in the system throughout its service life. In operation, the flow of the working medium is loaded with a small quantity of oil. The working fluid and oil do not operate separately and accordingly must be in tune with each other. The bearings and the paired worm shafts of the expansion machine are supplied with oil droplets, which are separated from the oil mist in the vapor of the working medium and thus return to the expander in oil form.

For use in the efficiency PACKs, a polyol ester-based oil was developed that can be nebulized very well and then separates easily from the oil again at the pressure difference in the expansion machine. As a lubricant, it is exposed to comparatively low temperatures, which is why hardly any temperature-related oxidation occurs. Oxygen, which could accelerate the aging of the oil, is also not present in R245fa. The oil can therefore remain in service for well over 50,000 operating hours. Once an efficiency PACK is opened as part of quality control, Orcan Energy's service technicians also replace the oil and send a sample to OELCHECK. However, a proportion of the volatile working medium inevitably enters the sample bottle with the oil. Therefore, only a gas-tight 80 ml aluminum sample bottle from OELCHECK is used. It is resistant to oils as well as refrigerants and withstands the internal pressure that can be built up by working or refrigerant residues in the sample.

 

Even if the oil in an efficiency PACK is not subjected to high thermal loads, analyses are important as part of quality control. After all, the performance of the oil and its interaction with the working fluid have a decisive impact on the service life of the compressor. The OELCHECK tribologists therefore look at, among other things, the values of any wear metals that may come from bearing points or the worm shafts. Since polyol esters react very sensitively to water, a determination of the water content according to Karl Fischer and a critical assessment of water contents above 50 ppm is an essential criterion.

 

Saving costs and reducing CO2

Well-known companies such as BASF, Bertelsmann or the Portland cement plant Wittekind, reduce their electricity costs with Orcan efficiency PACKs and at the same time achieve a significant improvement in their eco-balance. A more recent, typical example is Nordenhamer Zinkhütte GmbH. It is part of the Glencore Group and produces about 175,000 tons of fine zinc and zinc alloys per year. Instead of "blowing" the unused heat into the environment, it uses Orcan's compact plants to generate more than 5,000 MWh of electricity per year and reduce the company's carbon footprint by 2,800 tons annually. The efficiency PACKs are not only used in a wide range of industries, but increasingly also on ships around the world. The energy generated from the waste heat of the ship's engines is fed to the drive train or fed into the power grid on board. With the intelligent use of the waste heat from the engines, which often have over 100,000 hp, fuel savings of 7-9 % can be achieved. The "Green Jade" from Taiwan, one of the largest offshore installation ships for wind turbines, will soon also benefit from this. Eight efficiency PACKs will recycle its waste heat from engine exhaust and cooling water into electricity in such a way that a net output of more than 500 kW is generated on board.

 

OELCHECKER Summer 2021, Seiten 1-2

For further information visit: www.orcan-energy.com

 

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