Frequently Asked Questions

What is “Waste Heat” and where is it Available?
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.

Read more about waste heat from our partner organization, Heat is Power Association, here.

Waste heat is found in virtually every industry – and comes in many forms from jacket water and exhaust gases to geothermal brine and hot water from boilers.

Typical Applications Include:
// Combustion Engines
// Boilers
// Industrial Waste Heat
// Solar Thermal
// Geothermal and Co-Produced Fluids
// Oil & Gas Heat Recovery

See our Applications Page for more info.

Will ElectraTherm’s waste heat recovery solutions work on any recoverable heat source?
The Power+ performs best with hot water flows of 50-365 GPM (3.2-23 l/s) at 158-302°F (70-150°C). If the hot water source temperature falls above our upper limit, there is still potential to reduce the hot water source via a secondary loop. Gaseous heat sources can also be utilized with the integration of a heat exchanger.

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 loop will be needed as an intermediary loop between the waste heat source and the water loop needed for the Power+ input.

What is the Power+ Generator?
The Power+ Generator is an Organic Rankine Cycle (ORC) based waste heat-to-power generating system. It captures waste energy from distributed hot water sources such as stationary engine jacket water, biomass boilers, solar thermal and geothermal/co-produced fluids to generate up to 125kWe of fuel-free, emission-free electricity.

What is the Active Cooler?
The Active Cooler is ElectraTherm’s premier cooling solution that uses the same ORC process as the Power+ Generator in order to provide a net-zero power cooling solution that is also able to generate profitable power during times of low utilization. It serves as the radiator replacement that makes you money.

How are the Power+ Generator and Active Cooler different than other ORCs?
// Operates at low temperatures (hot water from 70°C to 150°C).
// Uses a proprietary twin screw expander that can accept dual-phase flow (mix of gas and liquid).
// The expander operates at much lower speeds (<5000 rpm) compared to turbine technologies, drastically reducing wear and tear.
// Variable output range allows ElectraTherm’s ORC solutions to continually produce power (or cool your system in the case of the Active Cooler) over a wide range of input parameters.

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 machines does ElectaTherm make?
The Power+ Generator 4400B and 4400B+ can generate up to 75 kWe while the 6500B and 6500B+ can generate up to 125 kWe. The Active Cooler also comes in two versions, the AC800 (for 800 kWth) and the AC1800 (for 1800 kWth). Hot water temperature, condensing temperature, available thermal power, and the hot water flow rate will determine how much power can be generated at each site.

How do I buy a Power+ Generator?
ElectraTherm sells through a distributor network. Please reach out through our Contact Us page to be put in touch with the appropriate person(s).

How much does a Power+ Generator or Active Cooler cost?
ElectraTherm’s ORC solutions are not stand-alone devices. They are part of a complete installed system.  The price of the module is only a part of a complete installed system. The total installed cost of the ORC system is a function of the module costs and the balance of plant.  The balance of plant refers to everything required to operate the ORC module.  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  With this information, ElectraTherm can determine the appropriate product 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 ORC system’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+ Generator to an internal combustion engine, there is no correlation in numbers, as the fuel costs and maintenance costs are not included. Product maintenance costs are low, and being driven from waste heat, there is no cost of fuel.

What is 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+ or Active Cooler are free). LCOP shows the actual cost of producing the electrical output by the different technologies. Contact ElectraTherm to find out LCOP comparisons between our ORC heat to power technologies and other power generation technologies.

What is the ROI for an ORC heat to power 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+ Generator and Active Cooler can generate revenue, please fill out a Contact Us inquiry, or fill out a Project Evaluation Form here.

How does ElectraTherm’s offerings 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 modules 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?
A 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.

What is the environmental impact of using ElectraTherm heat to power systems?
None. Units are self contained, fuel-free, 100% environmentally friendly and produce zero CO2 emissions. No EPA permitting is required.

How much maintenance is required?
Minor items, such as annual belt inspection, filter changes, along with standard pump, generator and dry cooler maintenance add up to minimal estimated costs, approximately 1-1.5 US cent/kWh generated, or approx. $5,000 – $7,500 (USD) annually. Water condensing may require filter changes and/or chemical treatment, often part of pre-existing cooling system management conducted by the host facility. The Power+ employs a positive displacement power block so the working fluid carries system lubricants in suspension. No oil pump, gear box or oil to change means minimal life cycle maintenance.

How much operator time is required?
Minimal. ElectraTherm systems are self-contained with on-board monitoring and controls, allowing either hands on or remote operation. The unit can be stopped, started and monitored at an offsite location via the remote monitoring software.


Contact us and we will be happy to help.

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