Mehtiyev A. D., Bulatbaev F. N., Neshina E. G., Bilichenko A. P.,

Balandin V.S.

Karaganda state technical University, Kazakhstan

Prospects for the use of mini co-generation plant based on Stirling engine for power supply of residential and industrial buildings

The generated electrical and heat energy is transferred over long distances, which is associated with considerable losses and material costs. The introduction of alternative energy sources, mini co-generation plants for power supply of residential and industrial buildings enables the generating energy directly on the site. It is more rational to reduce the loss of one kilowatt-hour of energy produced than to develop it, especially this circumstance concerns the heating systems of cities and towns. Today it is necessary to pay attention to the problems of Small Energy.

The development of high performance power supply systems directly affecting the economic development is accompanied by an increase in energy consumption and in mining operations and leads to depletion of natural resources and environmental pollution. The preferred directions include the works on development of the energy sector, the creation of new and effective scientific methods and techniques, providing the economical and environmentally friendly power consumption. The energy supply of the modern cities are built on the basis of the centralized scheme, which has the huge materials consumption, structural complexity, high accident rate and as a result a constant increase in the excessive costs on maintenance and repair of these systems.

Let us consider some issues of functioning of modern power supply systems associated with energy supply of remote consumers of low power, which may include for example farm enterprises, wintering, private buildings of small and medium business, holiday cottages, auto repair shops etc. For the operation of such facilities it requires the electric and heat energy supply.

An electric current is passed through the power lines from electricity generating plant to consumers sometimes with significant losses, especially when it concerns the remote consumers of low power, for example cottages, peasant farms and agro-industrial enterprises. In such cases the costs of energy carriers transporting are substantially increased due to the low power and large distances.

One of the solutions of these problems is the creation of independent power complexes of mini co-generation plants which have no analogues in the Republic of Kazakhstan and will significantly reduce the costs of electrical and heat energy consumed for residential buildings maintenance. It will be necessary for it to rethink and begin to implement a new strategy of electric and heat supply, the main principle of which is based on the fact that energy must be produced by the area of its consumption and consumed with a specific need, to change gradually over from traditional heating systems to energy saving technologies that require no further maintenance costs, and also to modify the accounting and payments systems for consumed heat, etc.

The constructive basis of the mini co-generation plant can be R.Stirling engine [1]. Stirling engine has several advantages compared to internal combustion engines: the ability to work on any type of fuel (gas, fuel wood and coal), low toxicity of exhaust gases, since the fuel combustion occurs at atmospheric pressure and also the long lifetime. The fuel consumption takes place outside the working cylinders. Another advantage of the engine is the simplicity of design, increased resource, efficiency and environmental friendliness. A number of foreign companies produce Stirling engines with specifications superior than the internal combustion engine and gas-turbine units have. The main disadvantages are the bulkiness and materials consumption, the lowest capacity indicator per kg of weight compared with internal combustion engines and electric motors [1].

We are working on a four cylinder engine with liquid cooling system, driving the electric generator. This power unit is able to generate electricity, and the generated heat is directed to the heat carrier warming for the heat supply system. The basic principle of Stirling engine is based on the difference in temperature between the hot and cold part of the working cylinder and the greater the temperature difference the higher effectiveness and efficiency factor. Due to the fact that the cooling of the working cylinders is carried out by circulating heat carrier, it’s achieved the best cooling mode of low-temperature part of the working cylinders.

The principal difference of cooling system developed by us is the use of the heat pipes, which work efficiently to remove the heat from the operating space into the heating area of the heat carrier. It allows creating the mini electric power plants with forced cooling and also sharply improving the efficiency factor in winter due to the natural factors using. The second difference is the use of linear AC generator without rotating parts. This difference will allow increasing the reliability and significantly simplifying the design of the generator.

Another distinctive feature is turbo inflating of air supplied to the combustion chamber, wherein the air is pre-heated due to the reserved heat of the cooling area of the working cylinders. The efficiency factor of the plant may increase up to 5 % due to the heated air supply.

An important feature of the mini co-generation plant developed by us is the creation of ceramic combustion chamber with multilayered thermal insulating and with 16 layers of aluminum foil. The chamber is made of porous ceramics with two walls. The technical vacuum is created in the internal cavity, which allows reducing the heat losses on the thermos principle.

The outgoing combustion gases have significant energy that can be used for additional warming of the heat carrier of the heat supply system.

The main advantage of mini co-generation plants and mini electric power plants is the ability to work on any type of fuel. For generator operation it requires only a heat source, therefore for the production of heat and electric energy it is suitable the low-calorie industrial and agricultural wastes, for example the slate stones.

The large prospect is the use as the drive of mini electric power plants the low-temperature Stirling engines with enlarged piston diameter, which can convert the energy of solar irradiation into electrical energy with an efficiency factor of 35 – 40 % and it excels more than twice the efficiency factor of the solar modules but it is much simpler in production technology and value. In this installation it will be used the heat pipes for increasing of cooling efficiency.

The conclusion is that there is a huge prospect of using of mini co-generation plants and mini electric power plants based on Stirling engine for power supply of residential and industrial buildings. The creation of the co-generation alternative energy sources based on heat engine with recuperative heat exchanger and a linear or rotating AC (alternating current) generator will allow creating a waste treatment facility for industrial and agricultural wastes, and also using the heat sources of the processing chain of production of outputs. The good prospect for the electric-power production is the use of low-temperature Stirling engines as an alternative to solar modules.

Bibliography:

1. Walker G. Stirling Engines. Short translation from English by Sutugina B.V. and Sutugina N.V.. Moscow, Mashinostroenie [Machine building], 1985, 408 p., illustr.