Gheorghe Popescu

Model of optimized solar heat engine operating on Mars

An endoreversible Carnot cycle is used to describe heat engine operation. This provides upper limits for real performance. The output power is maximized. Meteorological and actinometric data provided by the Viking Lander 1 are used as inputs. Four strategies of collecting solar energy are considered. Results concerning the following three parameters are briefly reported: (1) optimum solar collector surface area, (2) optimum solar collector temperature and (3) maximum output power.

Design and optimisation of a combination solar collector–thermal engine operating on Mars

A “dynamic” solar power plant (which consists of a solar collector–thermal engine combination) is proposed as an alternative for the more usual photovoltaic cells. A model for heat losses in a selective flat-plate solar collector operating on Mars is developed. An endoreversible Carnot cycle is used to describe heat engine operation. This provides upper limits for real performances. The output power is maximized. Meteorological and actinometric data provided by Viking Landers are used as inputs. Two strategies of collecting solar energy were considered: (i) horizontal collector; (ii) collector tilt and orientation are continuously adjusted to keep the receiving surface perpendicular on the Sun’s rays. The influences of climate and of various design parameters on solar collector heat losses, on engine output power and on the optimum sun-to-user efficiency are discussed.

SIMULATION OF A THERMAL SOLAR POWER PLANT OPERATING ON MARS UNDER CLEAR SKY AND DUST STORM CONDITIONS

Abstract The power plant analyzed in this work consists of a selective solar collector–thermal engine combination. The paper focuses on solar power plant operation under various weather conditions during all seasons on Mars. Meteorological data measured at Viking Landers (VL) sites were used in computations. Two strategies to collect solar radiation were analyzed: a solar horizontal (H) collector and a solar collector whose tilt and orientation are continuously adjusted to keep the receiving surface perpendicular to Sun rays (P). Both a low and a high efficiency thermal engine were considered. All the computations were performed for a selective solar flat-plate collector similar in size to the Mars Pathfinders Sojourner. Results show that generally the influence of latitude on performance is important. In some situations, the meteorological effects compensate the latitudinal effects and the output power is quite similar at both VL1 and VL2 sites. In case a low-efficiency engine is coupled to a horizontal collector, the solar efficiency does not exceed 0.13 at VL2 site. It is lower during summer and higher during winter dust storms. In case the low-efficiency engine is coupled to a P collector, the solar efficiency increases during summer. The solar efficiency is as high as 0.18 in case of a horizontal collector attached to a high-efficiency engine. If the high-efficiency thermal engine is connected to a P collector the solar efficiency increases significantly during summer and spring but does not exceed 0.18. The power provided by a system consisting of a horizontal collector and a low-efficiency engine does not exceed 7 W . Using a high engine coupled to a horizontal collector leads to a power output up to 13 W during spring, autumn and winter. The P collector is recommended mainly during summer and spring in combination with high-efficiency engines. In this case the solar efficiency could be as high as 25 W . The performance of PV cell power systems and properly designed dynamic solar power plants operating on Mars is comparable.

Mathematical Modelling of a Hybrid Micro-Cogeneration Group Based on a Four Stroke Diesel Engine

Abstract The paper presents a part of the work conducted in the first stage of a Research Grant called ”Hybrid micro-cogeneration group of high efficiency equipped with an electronically assisted ORC” acronym GRUCOHYB. The hybrid micro-cogeneration group is equipped with a four stroke Diesel engine having a maximum power of 40 kW. A mathematical model of the internal combustion engine is presented. The mathematical model is developed based on the Laws of Thermodynamics and takes into account the real, irreversible processes. Based on the mathematical model a computation program was developed. The results obtained were compared with those provided by the Diesel engine manufacturer. Results show a very high correlation between the manufacturer’s data and the simulation results for an engine running at 100% load. Future developments could involve using an exergetic analysis to show the ability of the ORC to generate electricity from recovered heat