Patent Application
20130283792
There is described a thermal power station system wherein at least one heat engine is connected to at least one work receiver. Also described is a method for energy supply to a building or a vessel.
Thermal power stations have lately become more and more relevant, as it often turns out to be favourable to produce electric power in addition to heat from a heat source. The terms CHP (Combined Heat and Power) and μCHP (micro-CHP) are used for thermal power stations. In the following the term CHP is used for any form of thermal power station.
The CHP system produces both electric power and thermal energy (heat) from several different heat sources. Heat sources may i.a. be sun, fuels and geothermal wells. Fuels may be oil, gas, wood, wood chips, straw, wood pellets, refuse, alcohols etc. To produce electric power in CHP systems a heat energy engine, or more generally also called a heat engine, is most often used. A heat engine is a device that converts heat energy to mechanical energy, which in turn may be converted to electrical power by means of a generator. Previously several systems for CHP are known. Examples of modern CHP systems are i.a. illustrated in US 2010/0244444 A1 and WO 2007/082640.
The advantage of CHP is that a high energy utilisation of the heat may be achieved, as the waste heat left after some of the energy is converted to electricity may be used directly for heating, achieving a very high total efficiency in the system.
The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art, or at least to provide a useful alternative to the prior art.
The object is achieved by the features disclosed in the below description and in the subsequent claims.
In connection with implementation of CHP systems several special considerations have to be made, as the systems are often to be operated in connection with buildings or vessels, such as dwellings or boats. Such considerations may be that the costs have to be minimised, that the size of the CHP plants must be minimized due to space limitations, the reliability must be high, exhaust must be diverted in a safe manner, components with high temperature must be made inaccessible so that humans or animals cannot be hurt etc. Due to such considerations there will often be a need to implement special measures ordinarily not necessary in corresponding technology installed in other contexts.
Measures extra favourable to implement are to ensure that the technology is as cheap as possible, that maintenance is as simple as possible, that operational reliability is as high as possible and that space and weight are small. As CHP systems utilise heat engines to produce electricity, it will be natural to focus on special measures to ensure that the heat engines have just these properties.
In current practice there are only a few heat engine technologies utilised for CHP systems. The most common are Stirling engines, ORC engines and redesigned Otto engines (petrol engines) utilising such as natural gas instead of petrol. All have various advantages and drawbacks, but some common denominators for the existing technologies are that they are often expensive and require advanced maintenance.
Stirling engines often work at very high working pressures, making the mechanical loads large, again hitting cost, reliability and the maintenance situation. ORC machines often utilise turbines as expansion mechanisms, and these are very expensive, in addition to requiring an evaporator, a component taking up much space. Rebuilt Otto engines are expensive, require relatively advanced maintenance i.a. due to their internal combustion, and they cannot utilise other heat sources than fuels suited for just internal combustion.
As an improved alternative to these technologies a piston based two-phase heat engine with at least one internal heat exchanger in at least one expansion volume will be able to be utilised. A two-phase heat engine is characterised in that it utilises a fluid alternating between a liquid and a gas phase.
Two-phase heat engines have the advantage of achieving relatively high power density even at lower pressures, as the phase transition from liquid to gas may give a high expansion ratio, at the same time as it requires relatively little energy to pump a fluid in liquid form prior to the expansion, as opposed to a heat engine where only a gas is utilised. The power density of a heat engine is often defined as energy output per machine volume unit or energy output per machine mass unit. By utilising a two-phase heat engine having an internal heat exchanger in the expansion volume, extra heat may be supplied during the expansion, like in a Stirling engine, leading to increased power density, which may contribute to further reducing the size of the engine. An ORC has only adiabatic expansion, i.e. expansion without heat supply, and will not be able to benefit from this advantage. For expanders the piston principle is the simplest and cheapest alternative. Moreover most engines produced today are piston engines, making production of piston baaed engines based on very available technology. This has a positive effect on i.a. cost and maintenance.
By utilising 2-phase piston based heat engines having internal heat exchangers in the expansion volumes, improving current CHP systems regarding cost, size, weight, reliability and maintenance is possible.
In a first aspect the invention relates more particularly to a thermal power station system wherein at least one heat engine is connected to at least one work receiver, characterised in that the heat engine is arranged to be able to utilise an operating fluid alternating between liquid and gas phase, and there in the heat engine is arranged at least one heat exchanger in thermal contact with at least one expansion chamber.
The work receiver may be a generator. The work receiver may alternatively be a shaft.
In a second aspect the invention relates more particularly to a method for power supply to a building or a vessel, characterised in that the method comprises the following steps:
In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:
a and b show examples of expansion arrangements for a heat engine having a heat exchanger in the expansion chamber.
In
In
Reference is then made to
The heat engine 32 is connected to a work, receiver 34, typically a generator, and from this there may via a power outlet 392, typically an el-power outlet, be delivered energy PEL to the power end user 4.
From a residual heat flow QK between the heat engine and the cold source 33 there may by means of a waste heat tapping point 329 be delivered residual heat energy QAK to the energy end user 4 via a waste heat outlet 393.
The heat source heat outlet 391, the el-power outlet 392 and the waste heat energy outlet 393 together form the multi energy outlet 39. The multi energy outlet 39 forms a practical interface between the thermal power station system and a distribution network (not shown) at the energy end user, for example distribution of electrical power for heating and light and also heat energy for room heating etc.
In
The thermal power station system 3 is positioned in the building 1 or in the vessel 2 where there is a need for energy supply QAV, PEL, QAK to one or more energy end users 4. The heat source 31 procures high-grade heat energy QV to the heat, engine 32 for example by burning wood chippings, wood pellets, oil or gas, heat recovery from ventilation air and other waste heat sources, process water etc. A share of the heat energy QV, may, if needed, be used in tapping from the heat tapping point 311 for use in end user(s) 4 in the need of high grade energy to function efficiently.
The heat engine 32 converts a portion of the supplied heat energy QV to mechanical energy by the working fluid m in a per se known way expanding in the expansion chamber 322 due to the heating. The expansion provides, possibly by means of transforming a translation movement to rotation, operation of the work receiver 34, which in a preferred embodiment is a generator able to produce electric power, which via the el-power outlet 392 may be distributed in a distribution network (not shown) at the end user 4.
When needed a portion of the residual heat QK normally being transferred from the heat engine 32 to the cold source 33, may be distributed via the waste heat outlet 393 to the end user 4 where recipients (not shown) able to utilise low-grade energy, make use of this waste heat in an appropriate manner, such as for heating. If the heating demand at the end user 4 is large enough, all of the waste heat QK may be distributed from the heat engine 32 to the end user 4, and consequently the cold source 33 will not have to receive any of this. In a further example where the end user 4 guaranteed will be able to use all the waste neat QK from the heat engine 32, the function of the independent cold source 33 may then be constituted by the end user 4, so that this will also have the function of cold source 33.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20101725 | Dec 2010 | NO | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NO2011/000054 | 2/16/2011 | WO | 00 | 7/22/2013 |
