As challenges with energy independence, carbon emission reduction, and water conservation increase, it becomes necessary to maximize efficient use of available heat, including waste and low-grade sources. Organic Rankine Cycle (ORC) systems represent a proven means for energy generation from low-grade sources like geothermal reservoirs and waste heat recovery from power plants and other industrial processes. Typical power plant waste heat sources include cooling tower water, auxiliary cooling water systems, and flue gases. Other industrial processes, like refineries, glass and cement factories, smelters, etc., also present great opportunities for waste heat recovery.
MiTi offers cost-effective, highly configurable ORC Turboalternators that convert waste and low-grade heat into reliable power. MiTi’s high efficiency oil-free ORC Turboalternators are sized to generate up to 35, 50 and 100 kWe. These can be operated individually or as modules that can be aggregated to achieve higher capacity points. Depending on the nature of the installation site, they can serve as bottoming cycles, directly increasing overall plant thermal efficiency, or co-generate from waste heat in auxiliary cooling water systems, exhaust, and other heat carrying streams. At approximately 12% thermal efficiency and >95% electrical conversation efficiency, MiTi’s systems present some of the highest ORC efficiencies available today.
The benefits are easily seen from an example: Consider a modern Diesel generator in the 1 to 3 MWe class, characterized by a thermal efficiency of approximately 50%. For every MWe generated, such system rejects heat at a rate of up to 400 kW to housing cooling water, and up to 600 kW to the exhaust gases. A MiTi® ORC Turboalternator using waste heat from the cooling water alone could produce up to 42 kWe extra per baseline MWe, which is equivalent to a nominal thermal efficiency gain of 2.4%. The economic advantages from fuel consumption reduction over the life of the system are obvious.
At the core of MiTi’s ORC turbogenerators are MiTi® 4th Generation high-efficiency compliant foil gas bearings. Since they use the process fluid vapor as lubricant instead of oil, they are characterized by a negligible operating power penalty, which allows for the development of ultra high-speed and power-dense machines with unprecedented high mechanical efficiency. In addition, foil bearings are low cost, and require virtually no maintenance. Each of these are primary considerations for installing power systems, where reliability under the harshest conditions is critical, and where both intermittent peak performance or nearly unmonitored continuous use are equally important.
MiTi has two main families of ORC Turboalternators. Our high speed axial turbine engines, are characterized by relatively flat adiabatic efficiency curves under a broad range of specific speeds, making them ideal for use in highly variable environmental conditions, as in geothermal sites, or where condensation temperatures fluctuate widely with the seasons. Our radial inflow devices exhibit a high single stage power density, and accommodate larger flow rates at lower spin speeds, which may be preferable for industrial applications with steadier operating conditions.
All of our engines are designed for use with standard organic refrigerants, such as R134-a, R245-fa, or HFO-1234yf. Process fluid is selected in accordance with customer’s operating conditions (e.g.: condensation/evaporation temperatures, level of superheat, flow rate, etc.), and the highly configurable engines are fitted with the corresponding modular nozzle assembly and turbine wheel. Special adaptations for use with other fluids like ammonia and super-critical CO2 are possible.
MiTi® ORC Turboalternators are characterized by aerodynamic components of high isentropic efficiency. Axial or radial, our turbine wheels and nozzles are carefully designed to perform over the broadest possible range of operating conditions, including off-design points and transient events.
Working fluid selection is performed by matching its thermodynamic and transport properties to the prevalent application site operating conditions. Our highly configurable units are equipped with modular turbine wheels and nozzle rings, which are selected according to the fluid chosen.
MiTi® ORC Turboalternators are equipped with a low part count, highly reliable, automatic flow throttling and control mechanism that can adjust turbine performance to operating condition variations, such as high pressure and temperature reservoir variations, weather or seasonal variations of condensation temperature, low loading, and other off-design conditions to improve year-round operating performance.
|Power||35, 50, 100 kWe|
|Voltage||230 VAC/120 VAC|
|Speed||20,000 to 60,000 RPM|
|Working Fluids||R134-a, R245-fa, HFO-1234yf, etc.|
Special Conditions: Supercritical CO2 Ammonia
|Max Operating Temperature||180C|
|Typical Pressures||6.5 bar (R-245-fa) to 20 bar (R134-a)|
|Typical Refridgerant Flow Rates||2 to 10 kg/sec|