Organic Flash Cycles for Intermediate and High Temperature Waste Reclamation

The Berkeley Lab energy reclamation technology uses an Organic Flash Cycle (OFC) that increases exergetic efficiency with isentropic or "dry" aromatic hydrocarbons as working fluids that almost perfectly match the temperature of the thermal resource, reducing a major contributor of system energy conversion inefficiencies. Heat addition takes place completely in the liquid phase of the cycle with the working fluid vaporized during flash evaporation.

The OFC invention has several configurations, each suited to different conditions and cycle requirements. For high temperature applications between approximately 200ºC and 400ºC, the single flash OFC achieves efficiencies comparable to the optimized Organic Rankine Cycle (ORC), but uses a simpler configuration. For lower temperature thermal resources in the range of approximately 80ºC to 150ºC, a secondary flash stop vaporizes more fluid for additional reclamation gains.

Another variation on the basic OFC replaces the throttling valve with a more efficient two-phase expander to reduce system irreversibility. The OFC outperforms the basic ORC with approximately 20% to 50% greater thermal energy utilization. It has approximately 90% heat addition efficiency compared to about 70% for basic ORC, about 75% for a zeotropic Rankine cycle with a binary ammonia-water mixture, and about 80% for a CO2 transcritical cycle.

Current cycle technologies for reclaiming waste heat are extensively used in traditional manufacturing industries including petroleum refining, pulp and paper, iron and steel, food and beverages, cement, fabricated metals. The implementation of OFC in these industries has the potential of an annual recovery of up to 1,703 quadrillion BTUs from waste heat with an approximate savings of $5.8 billion per year. The OFC is also a promising reclamation strategy for renewable energy sources such as solar thermal, geothermal, and biomass.

• Temperature matching for improved cycle efficiency
• Improved thermal energy utilization (approx. 20% - 50%)
• Reduced energy consumption / costs and greenhouse gas emissions
• Potential energy savings of $5.8B in existing manufacturing applications
• Uses existing plant components

• Renewable energy sources (geothermal, solar, biomass)
• Industrial thermal waste heat reclamation from
• Petroleum refining
• Pulp and paper processing
• Iron and steel production
• Food and beverage processing
• Cement production

Ho T., Mao S., Greif R.  “Comparison of the Organic Flash Cycle (OFC) to other advanced vapor cycles for intermediate and high temperature waste heat reclamation and solar thermal energy.”Energy 2012; 42: 213-223.

Ho T, Mao SS, Greif R.  “Increased power production through enhancements to the Organic Flash Cycle (OFC).”  Energy 2012; 45: 686-695.