Solar Field

OptionalThermal Storageor Boiler

Hot Thermal Fluid

Cold Thermal Fluid

ORC

Electric PowerOutput

Optional Heat Recovery from ORC Condenser

Pump Pump

Organic Rankine Cyclefor Small Scale Solar Power Generation

SkyFuel White Paper

© 2012 SkyFuel, Inc. All Rights Reserved.SkyFuel White Paper – Organic Rankine Cycle 2012.05

Organic Rankine Cycle With Solar Thermal Source

The Organic Rankine Cycle (ORC) uses the same thermodynamic processes as a steam turbine to convert thermal energy into electricity via a generator. A heat transfer fluid (HTF) is circulated through the solar field, where it is heated to the desired inlet temperature of the ORC system. The ORC’s evaporator vaporizes an organic fluid at lower temperatures and pressures than that of a steam turbine. The characteristics of the ORC make it an ideal energy conversion system for smaller scale concentrating solar power systems.

Advantages• ORC turbine is delivered as a pre-engineered,

skid-mounted, packaged power plant.

• Packaged units are produced in quantity, lowering unit cost for engineering and manufacturing.

• Pre-engineered units are delivered faster, shortening construction schedule.

• ORC plant is fully automated for unmanned operation.

• Heat is easily extracted from the condenser, making the ORC turbine ideal for combined heat and power (CHP) applications.

• ORC has a higher cycle efficiency at 150 to 350 ºC than a steam cycle.

Nameplate CapacityORC turbines are most economical in the range 500 kW to 10 MW electric output – a good match for industrial applica-tions, particularly when heat is also used at the same loca-tion. ORC turbines are available as packaged units, both with and without a thermal output option. As an example, a 10 MWe combined heat and power (CHP) unit requires a thermal input of 40 MW and delivers 30 MW of thermal power from the ORC condenser for Industrial Pro-cess Heat (IPH) applications.

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SkyFuel White PaperOrganic Rankine Cycle for Small Scale Solar Power Generation

For more information, please contact:Info@SkyFuel.comSkyFuel, Inc.18300 West Highway 72, Arvada, CO 80007 303.330.0276www.SkyFuel.com

Optional Energy Storage and Hybrid OperationThe capacity factor and dispatchability of the system can be increased significantly by the addition of thermal storage and /or a boiler, which can be fueled with biomass, biodiesel, or natural gas. Stored hot fluid can be withdrawn as needed and used to power the ORC, or the cold fluid can be heated with an alternative fuel source when it is desirable to operate the ORC during cloudy weather or at night.

The SkyTrough® Concentrating Solar CollectorThe SkyTrough® is a high performance, low cost, parabolic trough con-centrating solar collector for use in utility scale solar thermal power plants or industrial process heat applications. Each SkyTrough® solar collector assembly is 115 meters long with an aperture that is 6 meters in width. The collectors are modular and allow solar fields of different sizes to fit a wide variety of applications. SkyTrough® solar fields produce heated fluid at controlled temperatures from 150 to 550 °C.

System EfficiencyIn the range of operating temperatures of ORC systems, the SkyTrough® collects heat very efficiently (over 75 % of incident radiation converted to heat). An ORC used for combined heat and power has a thermal utiliza-tion rate of up to 98 %. The thermal to electric conversion efficiency can be as high as 25 %, and if the heat rejected in the condenser is used fully, then thermal losses and auxiliary power only amount to 2 % of the thermal energy delivered from the solar field.

Example System SpecificationGross Electric Output at 1000 W/m2 10 MW

ORC Gross Thermal to Electric Efficiency 25 %

Number of SkyTrough® SCAs (Solar Multiple = 1) 84

Total Aperture Area of Solar Field 55104 m2

Thermal Input from Solar Field 40 MW

Thermal Power to ORC Condenser 30 MW

Auxiliary Power Consumption 0.5 MW

Net Electric Power Output 9.5 MW

SkyTrough® 1000 W/m2 Efficiency Curve

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