Technology

The INRESOL Stirling technology has developed since the 1990’s in many areas, such as design, materials, mechanics, mechatronics, tribology, thermal management, electronics, software and others. The V2-6 core engine is a new version of the “gamma-type” Stirling engines, where new innovations have been implemented in several areas.

The V2-6 engine has the following features:
  • Clean engine tribology technology
  • Dry lubricated bearings and pistons
  • Low speed permanent magnet generator
  • Water cooling in crank case, generator and bearings
  • Nitrogen gas generator
  • Low filling pressure design
  • Automatic electric gas pressure control
  • Virtual Flywheel (anti vibration and automatic balancing)
  • Flexible speed of the power generator
  • High peak power output up to 4 times nominal power
  • And more…
The target is to mass-produce cost effective Stirling engines that have a quality standard seldom seen today, with aerospace quality nodal steel in the crank case, high quality bearings, high durability water cooled cylinders and advanced alloys in heat exchangers. This engine is built to last. No welding where nuts and bolts can be used, making the engine possible to overhaul and recyclable. This is the machine, you need to learn how to maintain for the next generation to inherit.

Inresol make connecting rods in an Aluminium Titanium type alloy, a material similar to the ones used in Drag Racing industry and high performing racing motorcycles (Al-Ti-Cr-Cu-Fe-Mg-Mn-Si-Zn).

Crank shafts are made in a steel alloy with multistep forging, also most often used in racing. In the stirling application we keep the loads well below the racing applications to enable long service life.
The crank shaft, connecting rods and the bearings are integrated in the generator unit with the stator and its liquid cooling system. The entire mechanism contains 1/50th in number of parts compared to the typical 4-stroke engines.

​​​​​​​The balancing of the engine is necessary to achieve low noise levels. This is done by simulation calculations during the design stage. The V2-6 engine also does its own optimization of balancing even during operation to manage a change in operational speed with different heat sources. 
With the use of a high voltage generator and power electronics and many more state of the art technologies, its power output has the stability comparable to large power generators. The power generator is well optimized and it can run at constant “straight line” torque from 0 – 1200 rpm.
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The V2-6 engine is designed to be operated with Dry lubrication technology as an alternative to oil lubrication. This is enabled with bearings adapted to dry conditions, cylinder coatings that are very hard and have low friction surface topology, pistons with dry lubricated piston rings, cooling system that replaces the typical oil, oil filters, oil pumps etc.
The cylinder coatings give the engine long life and this type of high durability coatings have been applied in Formula 1 since the 1990’s with championship winners.

Heat exchangers on the hot side of the engine are designed for operation at high temperatures of 600 – 1100C for extended periods. The heat exchangers are designed to operate on heat from any heat source as the engine is not operated on the combustion itself but the action of heat that pressurise a working gas inside the engine.

Combustion of biofuels as wood pellets or biogas or other fuels from crop waste or other renewable energy source. The range of different crop waste fuels are also wide (rice husk, coconut shells, wheat bran, corn stalk, palm shavings, bamboo dust, nut shells, bagasse, verge grass, miscanthus and more).

​​​​​​​At Inresol we have spent years on trials on different fuels and also on other heat sources as waste heat and high temperature energy storage systems.
The hot heat exchanger in typical service is to be in a red hot glowing state. The combustion temperature is controlled to be high and the burner operates on pre-heated air that is heated by the exhaust flue gas. This heat recovery is essential to achieve high efficiency.
The entire combustion chamber is heated to a near uniform temperature where the Heater on the engine is “red hot” in normal operation. Even the chamber walls are heated above ignition temperature of the fuel and becomes self-cleaning of char and other combustible substances by pyrolysis. All combustible substances are efficiently incinerated and in combination with the continuous combustion the exhaust emissions are low, even without any catalysts.

​​​​​​​The generator is a designed as a brushless permanent magnet torque motor/generator that acts as a starter motor and as a power generator in one. This type of generator has a very long service life and very high efficiency.
The built in inverter system produces a real sine wave power output in 1- to 3-phase connection. The power generator can produce the desired voltage of 110-240Vac and 50-60Hz, in 1-phase connection. There is also a connection to the 3-phase inverter inside at 400Vac available.
The power generator is optimised for the rpm range of 700 – 1200 rpm where the net electrical efficiency including the rectifier circuit is 91-94%.
The INRESOL Stirling engine power output is made through a multimode inverter where the power can flow bidirectional between the power loads, the grid connection and the internal battery storage. The generator operates at 5kW producing 565Vdc via a rectifier that feeds the power into a DC-bus. The DC-bus then feeds a grid inverter to power electrical loads and a DC/DC converter that charges a battery at 300Vdc. The battery DC/DC converter is bidirectional, so the power can flow in any direction in the generator, depending on current situation and power needed.
  • NOTE: Add figure…
Operating modes include:
  • Stirling power to load
  • Stirling power to battery charger
  • Stirling power to grid
  • Grid power to load
  • Grid power to battery (aux charge of battery)
  • Power sharing
  • Grid power limiter
  • Battery power to load (UPS mode)
  • Battery power to grid (sell excess power to grid)
  • Standby (no power needed)
​​​​​​​It is possible to connect external energy storage battery pack’s for applications where there is a need for higher electrical storage capacity.

STIRLING TECHNICAL DATA

DATA RECOVERY AND ANALYSIS

​​​​​​​The INRESOL Stirling V2 power generator has a cloud server connection where the internal power meter and data logger are transferred to the cloud with an internet dashboard. Any device with a web browser is enough to connect to the cloud supervised INRESOL Stirling V2. The cloud service can also be used to create “virtual power plants” where a larger number of units are monitored and controlled through the cloud, as if it’s a single large power plant.
​​​​​​​This feature enables a versatile range of functions for utilities and end users. The basic software application license is already installed upon delivery, and included in the basic price of your INRESOL Stirling V2. Additional more advanced features are available at an optional license fee, to advanced users, power utilities and others.

Inresol statistics

  • Alternative Biomass Fuel Breakdown