Technical and economical feasibility of the Rankine compression gas turbine (RCG)

The Rankine compression gas turbine (RCG) is a new type of combined cycle, i.e. combined steam and gas turbine installation, that returns all shaft power on one free power turbine. The novelty of the RCG is that the steam turbine drives the compressor of the gas turbine cycle. This way, the turbine of the gas turbine acts as a free power turbine. With its free power turbine the possible field of application of the RCG is mechanical drives. The RCG can be designed with components that can all be referred to as existing technology, which makes the RCG robust and technologically feasible. Thermodynamic calculations show that a thermal efficiency of about 40% is realistic. This is higher than simple cycle gas turbines, and equal to gas turbines with a recuperator. The calculations also show that the specific power of an RCG is up to twice as high than that of both simple cycle and recuperative cycle gas turbines. Finally, economical assessments show that the extra investments of an RCG compared to a simple cycle have an expected payback time of 2–4 years. This makes the RCG economically appealing, but further study is necessary to obtain more exact figures on the economical feasibility

Realization of a 4kW thermochemical segmented reactor in household scale for seasonal heat storage

Replacing fossil fuel by solar energy as a promising sustainable energy source, is of high interest, for both electricity and heat generation. However, to reach high thermal solar fractions and to overcome the mismatch between supply and demand of solar heat, long term heat storage is necessary. A promising method for long term heat storage is to use thermochemical materials, TCMs. The reversible adsorption-desorption reactions, which are exothermic in the hydration direction and endothermic in the reverse dehydration direction, can be used to store heat. A 250L setup based on a gas-solid reaction between water-zeolite 13X is designed and tested. Humid air is introduced to a packed bed reactor filled with dehydrated material and by the resulting adsorption of water vapour on TCM, heat is released. The reactor consists of four segments of 62.5L each, which can be operated in different modes. The temperature is measured at several locations to gain insight into the effect of segmentation. Experiments are performed for hydration-dehydration cycles in different modes. Using the temperatures measured at different locations in the system, a complete thermal picture of the system is calculated, including thermal powers of the segments. A maximum power of around 4kW is obtained by running the segments in parallel mode. Compactness and robustness are two important factors for the successful introduction of heat storage systems in the built environment, and both can be met by reactor segmentation. With the segmented reactor concept, a high flexibility can be achieved in the performance of a heat storage system, while still being compact

Temperature control of evaporators in automotive waste heat recovery systems

his paper presents a control strategy for the steam generation process in automotive waste heat recovery systems that are based on the subcritical Rankine cycle. The central question is how to regulate the flow of water into the evaporator such that dry steam is generated at its outlet, subject to large variations in the heat input. Tight control of this process increases the amount of recovered energy while ensuring safe system operation. The method consists of inversion-based feedforward combined with output feedback on the temperature of the evaporator, which is estimated using exhaust gas measurements. As this method does not require a high fidelity evaporator model, it is easy to implement. It is demonstrated on an experimental setup, where the exhaust flow is imitated by electrically heated air. On an automotive driving cycle, steam was generated reliably with a superheating temperature of 10-20 [K]