DE10008123A1 - ORC energy conversion apparatus useful for generating electricity comprises one or more solar collectors employing an organic heat-transfer medium - Google Patents

Abstract

Energy conversion apparatus based on thermal ORC cycle processes comprises one or more solar collectors employing an organic heat-transfer medium (I).

Description

The invention relates to a device for energy conversion based on thermal ORC cycle processes according to Stamm registration 199 07 512.3 especially for solar thermal application with a preferably one-stage low temperature ORC process.

For converting solar thermal energy into electrical energy On the one hand, there is the possibility of direct heating of water and overheating of water vapor in solar col proof, which generates dry steam, which in turn drives a turbine with a generator or a Dynamo machine is connected.

Alternatively, a thermal oil can be heated in collectors are used and this for indirect heating of a fluid be, this fluid generating steam in a sepa advise plant serves.

However, a very high tech African effort are operated. The investment cost for the steam generation, e.g. B. relaxation in a drum and subsequent overheating is significant. Furthermore it is problematic in the collectors with two different Physical states or phases of water, namely liquid and gaseous to work because here extremely different Density values are available.  

With a primary circuit made of thermal carrier oil, one is fine large amount of energy lost in the circulation of the oil to the maximum permissible so-called film temperature not to be exceeded stride.

With all known thermal carrier materials it takes place an near the permissible limit temperature wanted decomposition instead and the liquid changes its physico-chemical properties.

From the above, it is therefore an object of the invention to Device for generating energy based on thermal ORC Cycle processes indicate which is able to new appli to develop cations in the field of renewable energies.

The object of the invention is achieved with a front direction according to the features of the claims.

According to the invention it is provided that for the ORC group necessary thermal energy by means of a or several solar collectors is won, being in the solar collectors an organic medium, preferably hexamethyl disiloxane flows.

In the proposed device, the working fluid Hexamethyldisiloxane used on the hot side, it will Fluid at a pressure near or above the critical pressure of heated essentially 20 bar above the critical temperature. The steam obtained is then in a known ORC Plant used to generate electrical energy.

The proposed special working fluid hexamethyldisiloxane is extremely temperature stable, with decomposition upper half of essentially 350 ° C only low boilers are formed, which are in balance again to the original join together.

The emergence of unwanted long chain polymers or cyclical connections are almost impossible.  

The critical point of the fluid used is less than 20 bar and a temperature of essentially 246 ° C. At the Heating the fluid with this pressure lowers the density and it the volume increases almost continuously even when exceeded the critical temperature. This delivers an essential one utilizing difference compared to water vapor circuit pro or conventional ORC systems which are used in the Usually without overheating below the critical point, d. H. operated without steam overheating.

At 400 ° C and a pressure of 20.6 bar, the density of hexamethyldisiloxane is still approx. 70 kg / m ³ . In a cycle with about 60 ° C on the cold and about 400 ° C on the hot side, the density of the medium and thus the given volume flows only change by a factor of <10. The phase change takes place without major volume changes and not, as in Water vapor, at the same pressure due to sudden expansion.

The high density of organic vapor and that due to expansion increasing flow speeds allow an optimal Heat transfer with further, desired overheating.

According to the invention, the fluid can be directly in the pipelines of the Collector or heater to be heated and overheated without that in operation an additional evaporator vessel, for. Legs Drum or a so-called flash tank is necessary. Also will a primary circuit with thermal oil is superfluous.

The continuous increase in volume also increases the Flow rate continuously, even at constant pipe diameter the maximum permissible Speed considering the flow resistance not exceeded and also the minimum speed (film temperature) is not fallen below. This allows the The design of the heater is very simple become.

The invention is intended below with the aid of figures are explained in more detail.

Here show:

Fig. 1 is a structural formula of hexamethyl disiloxane;

Fig. 2 is an enthalpy-temperature diagram in comparison hexamethyldisiloxane and water;

Fig. 3 is an entropy-temperature diagram with details of the critical temperature point in comparison hexamethyl disiloxane and water or water vapor;

Fig. 4 is a temperature / volume diagram in comparison specific hexamethyldisiloxane and water; and

Fig. 5 shows a basic arrangement of the device according to the invention, wherein a solar or solar collector is used to heat hexamethyldisiloxane within an ORC cycle.

As can be seen in particular from FIG. 3, the ORC cycle using hexamethyldisiloxane as carrier liquid has a very high efficiency.

It has been shown that when the fluid is heated in the area the critical pressure the density decreases and the volume almost continuously increases even when the critical temperature is exceeded. This overheating, which according to the invention is usable, leads to an improvement in efficiency the combination of solar collector / ORC process.

Fig. 4 makes it clear that the phase change compared to water takes place without a major change in volume and there is no sudden expansion.

The high density of organic vapor and that due to expansion increasing flow velocity improve heat transfer if further desired and used overheating occurs.  

The arrangement of FIG. 5 assumes a small ORC power plant with the direct heating of the fluid using a suns collector made. The thermal energy is fed to a turbine, which in turn is connected to a generator or a dynamoelectric machine. A regenerator and a condenser with a feed pump are used to make the carrier fluid available again. In addition, the possibility is provided to dissipate excess thermal energy for the purpose of condensing the carrier liquid. Here it is conceivable to make this energy available to another cycle.

In the embodiment according to FIG. 5, a single-stage ORC arrangement is assumed, although a multi-stage or cascaded cycle can of course also be implemented.

Claims (2)

1. Device for energy conversion on the basis of thermal ORC cycle processes, characterized in that the thermal energy required for the ORC cycle process is provided by means of one or more solar collectors, an organic medium, preferably hexamethyldisiloxane, flowing in the solar collector (s). 2. Device according to claim 1, characterized in that the hexamethyldisiloxane in a cycle above the critical Temperature in the range of 240 ° C to ≦ 500 ° C, preferably 400 ° C is subject to heating and overheating.