ElectraTherm ORC Technology Frequently Asked Questions

What is the Power+ Generator™? The Power+ is a waste heat to power generator that uses Organic Rankine Cycle (ORC) technology to convert industrial waste heat to usable electricity. What is waste heat? Waste heat refers to heat produced by industrial machines, electrical equipment, and processes for which no useful application is found.  For instance, a diesel fired generator rejects heat into both the jacket water and the exhaust, where there is typically no use for these heat sources.  A furnace or boiler also produces hot exhaust, where it is usually expelled through the exhaust stack into the atmosphere. What types of applications are suitable for power production using the Power+ Generator?

How is the Power+ Generator different than other ORCs?

  • Operates at a relatively low temperature (from 77°C up to 122°C)
  • Uses a proprietary  twin screw expander as a power block which can accept two phase flow (i.e. a mix of gas and liquid)
  • The expander operates at low speeds (<5000RPM)
  • Variable output range, allowing the Power+ to continually produce power over a wide range of input parameters
  • Modular and mobile footprint

If the Power+ Generator can accept hot water above boiling temperatures, then how is it possible to make hot water above 100°C that is not steam? By maintaining pressure in a closed plumbing system, hot water can be maintained as a liquid above the atmospheric boiling point.

What size machine does ElectaTherm make?  Can smaller or larger machines be made? Will custom machines be offered? The currently offered Power+ can produce up to 65kWe gross at optimal input heat source conditions.  Hot Water temperature, condensing temperature, the available thermal power, plus to a lesser degree the hot water flow rate will determine how much power the Power+ will make at each site.  The Power+ has the capability to “turn down” or produce less power than 65kWe, but it cannot make more than 65 kWe.  Custom machines are not available, however ElectraTherm has several varieties of the standard machine and one of these should be able to cover your needs.

How do I buy a Power+ Generator? ElectraTherm sells through a distributor network. Please contact ElectraTherm to be put in contact with a distributor.

How much does a Power+ Generator cost? The Power+ Generator ORC equipment is not a stand-alone device.  It is part of a complete installed system.  The price of the Power+ is only a part of a complete installed system. The total installed cost of the Power+ is a function of the Power+ costs and the balance of plant.  The balance of plant refers to everything required to operate the Power+ Generator.  This includes plumbing, electrical, and site construction costs that are site specific. Depending on the actual installation site, the varying total installed costs can vary up to three times.  Every site will have different installed costs or material costs specific to that particular location’s requirements. If you have a project in mind, the next step is to fill out a Project Evaluation Form (PEF) at www.electratherm.com/pef.  With this information, ElectraTherm can determine the appropriate Power+ for the project and balance of plant requirements. An ElectraTherm applications engineer will provide you with a free project assessment, including performance estimates and expected return on investment.

What is the installed cost per kWe? The installed cost per kWe is determined by the total installed plant cost (CapEx) divided by the plant output (kWe).  Given that the total plant cost can vary, and the Power+ Generator’s output will vary depending on the heat source and the condensing solution, this metric again can vary widely. Cost per kWe is not the preferred metric to compare waste heat to power technologies, as it does not relate to hours of operation during the year, operating expenses (fuel costs) and maintenance costs.  For example, if comparing the installed cost per kWe of a Power+ to an internal combustion engine, there is no correlation in numbers, as the fuel costs and maintenance costs are not included.  Power+ maintenance costs are low, and being driven from waste heat, there is no cost of fuel.

What the appropriate metric to compare power producing technologies? Levelized cost of power produced (LCOP) which refers to the life cycle cost of power.  This takes into account OpEx + CapEx + Fuel costs (in most cases, the fuel input costs to the Power+ are free). LCOP shows the actual cost of producing the electrical output by the different technologies. Contact ElectraTherm to find out LCOP comparisons between Power+ technology and other power generation technologies.

What is the ROI for a Power+ Generator installation? The return on investment (ROI) is driven by three key components—the value of power associated with the project, hours of run time per year and the net power output of the Power+ Generator. There can be additional economic and environmental benefits if the time is taken to quantify them.  Avoided cooling costs, peak load offset and other problem solving events are a few of them. In certain geographies, there can be additional incentives available including emission credits, carbon tax offsets, capital cost rebates or enhanced power value for green power production. If you have a specific project you wish to look at, or want to understand more of how the Power+ can generate revenue, please fill out a Contact Us inquiry, or fill out a Project Evaluation Form here 

How does the Power+ generate electricity/connect to the grid? Power is produced through the use of an induction generator.  The generator requires a grid connection to generate power.  The Power+ Generator can be connected to smaller, isolated micro grids, if the total capacity of the grid is three times the gross output or greater.

How does the twin screw expander work? Twin Screw ExpanderA twin screw expander is also called a Lysholm motor. The twin-screw type expander is a positive displacement device that operates when a gas or dual phase flow is pushed through a pair of meshing close-tolerance screws similar to a set of worm gears. The twin screws rotate when a pressure differential is high enough to turn the screws creating a mechanical work output. 

What makes the ElectraTherm twin screw expander advantageous over turbine based technology? The ElectraTherm twin screw expander works like a twin screw compressor, only in reverse.  However ElectraTherm twin screw expander has a patented, licensed profile that is the most efficient profile created for twin screw expanders. Additionally the rotor surfaces roll across each other, as opposed to sliding. The Power+ also has a patented in process lubrication system, simplifying and reducing the capital costs and maintenance costs of the system.  Twin screw expanders have very low rotational speeds, < 5000 RPM, as compared to turbine based technology.

What are the advantages of twin screw expander “part load operation”? The Power+ Generator can provide part load performance down to virtually zero kWe output.  This allows the Power+ ORC to operate over a widely varying heat source input range. The robust, solid steel rotors are unaffected by perturbations in vapor quality, temperature and flow. The Power+ simply follows the waste heat input. This is particularly advantageous when load following an engine’s throttle position or varying process heat.

What refrigerant does the Power+ Generator use? Honeywell R245fa. Benefits include low greenhouse gas producing, non toxic and non flammable.

I have exhaust stack heat, how do I connect a Power+ Generator? The Power+ can utilize exhaust stack heat with the use of an exhaust gas heat exchanger. ElectraTherm will assist in specifying the correct model for your application.

Can the Power+ Generator directly use thermal oil or hot exhaust gas as a waste heat input medium? No. The Power+ is designed to accept pure hot water, condensed steam, or a hot water and glycol mix as the heat input medium.  For waste heat recovery applications that are not water based, a secondary water lop will be needed as an intermediary loop between the waste heat source and the water loop needed for the Power+ input.