Institute of Fluid-Flow Machinery
Polish Academy of Sciences

One of the new promising directions of modern energy, complementing the centralised energy sector, is the distributed energy sector, where electricity is produced in cogeneration with heat. There is a number of distributed energy technologies with low power generation and heat. According to our knowledge, the shortest time horizon is associated with the use of Rankine steam circuits for low boiling agent (Organic Rankine Cycle - ORC) in a micro-power plant. On this basis, the concept of Home Micropower Plant was created at the Institute of Flow Machinery PAS. This ORC micropower plant is designed to produce electricity and heat for domestic use [I/7]. In the future, the CHP plant will replace conventional boilers for heating objects such as: single-family cottages, multi-family houses, settlements, etc. Gabaritically, the boiler with the Micro power plant will be very different from the heating boiler to date, but it will generate electricity in addition to the heating function. A steam engine for a low boiling factor, operating in a range of significantly lower temperatures than a combustion engine and a gas turbine, requires less valuable materials and is easier to produce. It makes it possible to generate electricity at prices close to the prices of energy produced in traditional high power gyms. The improved use of fuel energy in CHP plants leads to a reduction of harmful emissions associated with the fuel burning process. A small cogeneration gym can be fully automated and does not require operation. The basic components of the micro power plant are: boiler (evaporator), steam turbine, condenser (condenser), electric generator and power pump. A new concept of a micro-gym requires solving a number of new problems. One of them was to develop in 2010 the concept of computational algorithms and the design of condenser and evaporator heat exchangers for the circulation of home power plants. In order to use compact heat exchangers with intensive heat exchangers in the micro power plant circulation, an analysis of the various structures of exchangers with microchannels: mantle-tube, plate, microchannels was carried out. Microchannels (with diameters of ten parts of a millimeter) recuperators result in a significant reduction in the volume occupied by the exchanger compared to recuperators with conventional channel diameters. In addition to the development of calculation programs for the designed exchangers, the work of these exchangers was analysed at partial heat loads of the micro power plant, i.e. at different heat consumption in the condenser. Dynamic states of future heat exchangers have been analysed. A new concept of a tube tube type mantle-tube heat exchanger has been developed. This exchanger reduces the operation of the circulation pump in the ORC micro-gym.

In addition to theoretical works, experimental works are carried out in cooperation with the Gdańsk University of Technology (Cathedral Engineering) on an experimental stand, built in previous years, simulating the work of a micro-gym. In 2010, three different positive-type centrifuge machines (helicopter expander and expanders with sliding blades) were tested. The results received are encouraging. In further experimental studies, the expander will be replaced by microturbine of its own construction. Original prototypes of such radial and axial microturbines have already been made and will be tested in the near future [I/1,I/3].

Depending on the configuration, the heat source of the micro power plant may be gas from the combustion of natural resources or biomass, geothermal deposits or solar collectors. Waste heat from technological processes may also be used as a heat source. Electricity is produced by a microturbine-driven generator operating on a water vapour or a low boiling agent pair. The power of the designed turbine is within a range of several to several dozen kilowatts, depending on the applications. The advantage of a micro-gym is its compactness and small dimensions. Small dimensions of the gym are achieved through the use of modern materials and modern microtechnology. Small dimensions of turbines and heat exchangers lead to low costs of generating electricity and heat. A very beneficial feature of the micropower plant is also easy and safe operation due to its full automation.