Organic Rankine Cycle (ORC) Waste Heat Generator (WHG) Technical Information provided by Greenvironment plc confidential
Waste Heat Generator (WHG) • Converts waste heat into electricity – Capable of using ‘low grade’ waste heat
•Waste Heat Generator (WHG)
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Turbines • Devices that converts fluid flow into work – Gas turbine • Working fluid is combustion products and air
– Water turbine (hydro) • Working fluid is water
– Steam turbine • Rankine Cycle – water is boiled to vapor before passing through turbine – Working fluid is water vapor (steam)
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Rankine Cycle • Thermodynamic cycle which converts heat into work – Working fluid is often steam • Requires high temperatures to vaporize water • 80% of all power in the world is produced with this technology • Low Temperature heat sources produce little useable steam • Inherit problem is
•CONDENSER •Water
high latent heat of water in liquid-vapor phase change 3
Organic Rankine Cycle • For many (low temperature) waste heat applications, we need a fluid that boils at a lower temperature than water – Historically, such fluids have been hydrocarbons - hence the name Organic – Modern Working Fluids include: Propane / Pentane / Toluene / HFC-R245fa • These Working Fluids allow use of Lower-Temperature Heat Sources because the liquid-vapor phase change, or boiling point, occurs at a lower temperature than the watersteam phase change Water
R245fa
1 bar (0 psig)
100°C (212°F)
15,6°C (60°F)
19,6 bar (270 psig)
212°C (413°F)
121°C (250°F) 4
Waste Heat Sources • Waste heat is any source of otherwise unused heat – that is why ‘fuel’ is free – Waste heat from MicroTurbine exhaust – Waste heat from industrial processes • Process stacks from drying or heating processes
– Heat from waste fuel • Biomass or Biogas is burns to produce heat directly
– Not waste heat • A boiler creates heat for vaporization in a closed loop system – not free fuel 5
The Complete System •Integrated Power Module
•Generate •125 kW
•R245fa
•Heat Source •375F (190C)
•Evaporative
•3 MBTU/H
Condenser
•Evaporator
•Pump 6
How it Works - 1 •Integrated
•Generate
Power
•125 kW
•R245fa
Module
•Liquid •85F (29C) •26psig
•Heat Source •375F (190C)
•Economizer
(1.8bar)
•3 MBTU/H
•Evaporator
•Evaporativ e Condenser
•Liquid •85F (29C) •230psig (16bar)
•Receiver •Pump
The working fluid is in the receiver as a liquid at the condensing pressure and temperature. It enters the pump where the working fluid’s pressure is raised to the evaporating pressure. 7
How it Works - 2 •Integrated
•Generate
Power
•125 kW
•R245fa
Module
•Liquid •85F (29C) •26psig
•Heat Source
•Economizer
•375F (190C) •3 MBTU/H
•Evaporator
(1.8bar)
•Evaporative
•Liquid •118F
Condenser
•Liquid
(48C)
•85F (29C)
•220psig
•230psig
(15bar)
(16bar)
•Receiver •Pump
The working fluid passes through a heat exchanger (Economizer) to take heat out of the gas leaving the Integrated Power Module. This improves system efficiency. The working fluid is now 8 a warmer, high pressure liquid.
How it Works - 3 •Integrated Power Module
•Generate •125 kW
•R245fa
•Vapor •240F (115C) •220psig (15bar)
•Heat
•Liquid
Source
•85F (29C)
•375F (190C)
•26psig
•Economizer
•3 MBTU/H
(1.8bar)
•Evaporative
•Liquid
•Evaporator
•118F
Condenser
•Liquid
(48C)
•85F (29C)
•220psig
•230psig
(15bar)
(16bar)
•Receiver •Pump
The working fluid enters the Evaporator, where the working fluid is exposed to waste heat which 9 evaporates the fluid to a high pressure vapor.
How it Works - 4 •Integrated
•Generate
Power
•125 kW
•R245fa
Module •Vapor •240F
•Vapor
(115C)
•145F
•220psig
(63C)
(15bar) •Heat Source
•Evaporator
•85F (29C)
•26psig (1.8bar)
•375F (190C) •3 MBTU/H
•Liquid
•26psig
•Economizer
(1.8bar)
•Evaporative
•Liquid •118F
Condenser
•Liquid
(48C)
•85F (29C)
•220psig
•230psig
(15bar)
(16bar)
•Receiver •Pump
The working fluid (now a vapor) enters the turbine of the IPM. The working fluid’s pressure drops across the turbine to the condensing pressure, spinning the turbine (which is connected to the generator) in the process. The driving force is the pressure difference across the turbine. 10
How it Works - 5 •R245fa •Vapor
•Vapor
•240F
•Vapor
•85F
(115C)
•145F
(29C)
•Liquid
•220psig
(63C)
•26psig
•85F (29C)
•26psig
(1.8bar)
(15bar) •Heat Source
(1.8bar)
•Economizer
•375F (190C) •3 MBTU/H
•Evaporator
•26psig (1.8bar)
•Evaporative
•Liquid •118F
•Liquid
(48C)
•85F (29C)
•220psig
•230psig
(15bar)
(16bar)
Condenser
•Receiver •Pump
The working fluid still has an enormous amount of heat, some of which is transferred to the pumped liquid in the economizer. This helps in two ways: 1) this heat would have otherwise been extracted in the condenser and; 2) there is less heat required at the evaporator due to the 11 liquid being pre-warmed. •1
How it Works - 6 •R245fa
•Vapor •85F (29C) •26psig
•Vapor
•Vapor
(1.8bar)
•240F
•Vapor
•85F
(115C)
•145F
(29C)
•Liquid
(63C)
•26psig
•85F (29C)
•26psig
(1.8bar)
•220psig
•Heat
(15bar)
Source •375F
(1.8bar)
(190C) •3 MBTU/H
•Evaporator
•Economizer
•26psig
•Ambient
(1.8bar)
Air 75F (24C)
•Evaporative •Wet Bulb
•Liquid •118F
•Liquid
(48C)
•85F (29C)
•220psig
•230psig
(15bar)
(16bar)
Condenser
•Receiver •Pump
The working fluid (still a vapor) then flows to the condenser where heat is extracted and the 12 working fluid condenses to a liquid.
How it Works - 7 •R245fa
•Vapor •85F (29C) •26psig
•Vapor
•Vapor
(1.8bar)
•240F
•Vapor
•85F
(115C)
•145F
(29C)
•Liquid
•220psig
(63C)
•26psig
•85F (29C)
•26psig
(1.8bar)
(15bar) •Heat Source
(1.8bar)
•375F (190C) •3 MBTU/H
•Evaporator
•Economizer
•26psig
•Ambient
(1.8bar)
Air 75F (24C)
•Evaporative
•Liquid •118F
•Wet Bulb
Condenser
•Liquid
(48C)
•85F (29C)
•220psig
•230psig
(15bar)
(16bar)
•Receiver •Pump
The low pressure, liquid working fluid drains back to the receiver and is ready to be pumped to 13 high pressure and flow towards the integrated power module.
Applications • Turbines Exhaust – Waste heat from exhaust
• Industrial Stack Gas – Refineries – Incinerators – Drying processes
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Applications • Geothermal – Water or Steam
• Solar Thermal – After steam process – Indirect evap source
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The ORC Power Skid • Capstone supplies the ORC ‘Power Skid’ – Includes electronics, receiver, economizer, power module and various pumps – Needs external evaporator and condenser
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Power Skid Fluid Connections •Hot Vapor from Evaporator
•Cool Liquid from Condenser •Warm Liquid to Evaporator
•Warm Vapor to Condenser
Power Skid Components •Separator
•Inlet Control
•Slam
•Integrated
Valve
Valve
Power Module
•Programmable Logic Controller (PLC) & Magnetic Bearing Controller (MBC)
•Receiver •Field Connections
•Power •Electronics •Bypass •Economizer
•Separator Drain Valve
•VFD for Pump
Valve •Pump
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Power Skid Specs • Turbine Expander and Generator – Hermetically sealed power module – no leaks – Magnetic Bearings – no lubricants – 26,500 rpm – no vibration
• Power electronics – 125 kW – Grid Connect only – 380-480V, 3 phase, 3 wire 50/60 Hz
• Working fluid HFC-R245fa • Dry weight 7,000 lbs • 46” w x 112” l x 79.5” h 19
Evaporator • Transfers waste heat energy to refrigerant, resulting in vaporization – Direct, heat transfers directly from the waste heat source to the working fluid • Likely choice for a Microturbine application where waste temperatures are low and exhaust stream is clean • Heat source needs to be near ORC
– Indirect, thermal transfer medium is used between the heat source and the working fluid (e.g. thermal oil, hot water, steam) • Requires more ancillary equipment • Less efficient overall • Good fit if heat source is far from ORC 20
Condenser • Rejects latent heat of working fluid, resulting in condensation – Direct – The working fluid passes through a heat exchanger that rejects heat directly to the environment. – Indirect – A medium such as water is passed through a heat exchanger and takes the rejected heat out of the working fluid. The medium then transfers the heat somewhere else. – Cooling towers, air cooled condenser (Dry Cooler), ground water, evaporative condenser • Cooling towers (if already existing) and direct evaporative condensers are likely the best match for MicroTurbine applications 21
Installation Considerations • Evaporator & Condenser must be within 50ft of the ORC power skid – Minimize refrigerant run length • Minimize heat loss / absorption • Minimize amount of R245fa used
• Condenser must be elevated (flow to receiver) • Qualified technician required to handle R245fa • Internal cleanliness (of R245fa loop) important
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Complete Installation
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Heating, Cooling, Power • Cycle effectiveness is determined by the heat source and condensing source – Determine total heat and temperature available – Determine total cooling available
• Power available is determined by multiplying the heat available by the cycle effectiveness – More heat available => less cooling required – Less heat available => more cooling required
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Available Power Output • More heat is required for a given power production as condensing temp increases. • Size heat source and condenser for ambient conditions. 25
ORC with MicroTurbines • Typical MicroTurbine implementation – 6 to 8 Capstone C65 MicroTurbines – One ORC WHG Power Skid – One direct MT exhaust to refrigerant heat exchanger – One direct evaporative cooling tower or piggyback on existing cooling tower.
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Free Electricity? • Or, how to build a ORC WHG value proposition – System uses low grade heat that is usually wasted – no other good use – Increase overall efficiency of systems – Consumes no additional fuel – Produces no additional emissions – Wasted energy into electric power may • Reduce demand charges • Capture carbon credits • Qualify for renewable energy incentives 27
Calculating New Efficiency • Using waste heat to generate electric power increases overall system efficiency – Low grade waste heat is used, so assume it can not be used for any other purpose – Example, 6 Capstone C65s • • • •
Produce 390kW at 29% Electric Eff A 125kW ORC WHG is added 515kW is produced, using no added fuel new efficiency is – (New power/old power)*old Efficiency = 38%
• The ORC increases electric efficiency to over 38% 28
Case Study • Biomass boiler test site in the south east USA.
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Case Study Payback • Free fuel and low Maintenance Cost provide payback Annual Run Hours
8,400
Net Electrical Output
107kWe
Annual Production Gross Revenue
8,400 x 107 = 898,800 kWh 898,800 x $0.18 = $161,784
Maintenance Cost 898,800 x $0.0075 = $6,741 Net Annual Revenue
$155,043
Cost of Project
$298,000
Simple Payback
< 2 years
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Technology Advantages • Very similar to those of Capstone MicroTurbines High Speed Generator
Increased Efficiency, Reliability, no gear box
Magne
Increased Efficiency, Reliability, Reduced losses
Power Electronics
Efficient variable speed opera
No lubrica
Increased Reliability, Reduced parasi
No coupling
Increased reliability, fewer components
Variable speed opera
Op
Herme
Higher reliability, fewer wear components
Single moving part
Increased reliability
Modular Design
Simple Integra
