Energetic and economic investigation of Organic Rankine Cycle applications

TLDR: The use of organic working fluids for the realization of the so-called organic rankine cycle (ORC) has been proven to be a promising solution for decentralized combined heat and power production (CHP) as discussed by the authors.

About: This article is published in Applied Thermal Engineering.The article was published on 2009-06-01 and is currently open access. It has received 474 citations till now. The article focuses on the topics: Organic Rankine cycle & Rankine cycle.

Figures

Table 2: List of working fluids

Fig. 12 shows the setup of such a system. A biomass fired boiler (1) heats a thermal oil loop (2). The thermal oil then preheats (3), evaporates (4) and superheats (5) the organic working fluid. As expansion machine a scroll type expander (6) can be used.

Fig. 8 shows the schematic setup of such a system. The Organic Rankine Cycle, which is similar to the ORC presented in the Introduction chapter, is heated with the excess heat of the combustion engine.

Fig. 10 T-s-Diagram R245fa (0-1 compression in feed pump 1-2 preheating 2-3 evaporation 3-4 superheating 4-5 expansion 5-6 desuperheating 6-0 condensation)

Table 3: Cost assumptions for efficiency calculations

Fig. 1 Main components of the ORC

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Energetic and economic investigation of organic rankine cycle applications" ?

In this paper the state of the art of ORC applications will be presented together with innovative systems which have been simulated in a process simulation environment using experimental data. 

Q2. What is the common way to desalinate water?

The most common way to desalinate water is by means of processes with phase change like Multi-Stage-Flash-Evaporation (MFS) [20], Multi-Effect-Distillation (MED) [21] and others. 

Q3. How is the efficiency of a waste heat recovery utility determined?

The efficiency of a waste heat recovery utility is strongly dependent on the interest rate and the full load hours of the system. 

Q4. Why is the working fluid used in the regenerator?

Due to the fact, that the used working fluid is after the expansion still in the area of superheated vapour, it is used in the regenerator (18) in order to preheat the liquid working fluid. 

Q5. Why is the water flow to the side with the higher concentrated solution higher?

Due to the water flow to the side with the formerly higher concentrated solution the liquid level and therefore the hydrostatic pressure (equal to the osmoticpressure) is higher. 

Q6. How much is the energy production cost of a scroll type expander?

By using a scroll type expander with a pressure ratio =3, the condensation temperature will be around 91°C, which is sufficient for heating purposes. 

Q7. What is the main reason for the desalination of seawater?

Since a large part of the world population is concentrated in coastal areas, the desalination of seawater seems to be a promising solution. 

Q8. Why is the liquid working fluid used for preheating?

Due to the negative inclination of the vapour saturation line (see Fig. 10) between evaporation (2-3) and condensation (6-0), the sensible heat that rests in the expanded vapour (5) can be used for preheating the liquid working fluid. 

Q9. What is the advantage of a stand-alone solar desalination system?

The advantage of such a system is that it combines an efficient desalination technology (Reverse Osmosis) with a renewable energy source (solar radiation). 

Q10. What is the optimum working fluid for a scroll expander?

The working fluid R134fa has itsoptimum at moderate live steam temperatures, the optimum will not be reached due to too low condensation temperature of < 10 °C. 

Q11. What is the dependency of the membrane?

This dependency is described with equation (10).( )PmemPP wwABwm −⋅⋅=⋅ * (10)At the surface of the membrane there is a higher concentration of solute because the pure water is forced through the membrane and the solutes are hold back. 

Q12. How many kW of power can be produced by the organic Rankine Cycle?

the Organic Rankine Cycle can be characterised as the only proved technology that is commonly used in ranges of a few kW up to 1 MW. 

Q13. What is the optimum evaporation temperature of the working fluid?

According to the literature, there is an optimum evaporation temperature of the working fluid, which depends on the quantity of the recycled geothermal water, at which the capacity of the Clausius–Rankine is the highest [15]. 

Q14. What is the critical temperature of the fluids?

The fluids are given in the order of rising critical temperature Tc and normal boiling temperature Ts, 1 bar , whereas the critical pressure pc and the vapour pressure at 20 °C decline. 

Q15. What is the purpose of this paper?

In this paper the state of the art of ORC applications will be presented together with innovative systems which have been simulated in a process simulation environment using experimental data.