Multi-objective optimisation of remote community energy systems with consideration of noise disturbance

A multi-objective evolutionary algorithm developed at the Laboratory of Industrial Energy Systems is used to determine the best technological solutions to satisfy the electrical needs of a remote community. Simulations of the community are based on a superstructure in which organic Rankine cycle, diesel engine, photovoltaic and other technology options (heat storage, cogeneration engine, cooling tower, parabolic through,...) are included in the form of modules. These modules model the most significant factors: thermodynamic behaviour, economic trends, gaseous and noise emissions. An objective function including noise level, impact, and location is used to characterise the noise disturbance. Optimising such a superstructure along Pareto curves (optimal trade-off curve between the economic and noise objectives) while simultaneously accounting for time availability is performed by the evolutionary algorithm. Trends on the optimum power technologies as well as the relation to their geographical location are shown for different situations.

Multicriteria Optimisation of Small Hybrid Solar Power System.

Daniel Favrat, El Hadj Malick Kane

A new concept of small hybrid solar power system (HSPS) has been successfully demonstrated in the context of a project called SPS (Solar Power System). This plant integrates two rows of solar collectors, two superposed Organic Rankine Cycles (ORC) each equipped with a scroll hermetic expander-generator and a heat engine. In operation with solar energy only, the heat is supplied by a thermal fluid (presently pressurized water) heated in the vacuum insulated focal tubes of sun following, flat concentrators made of series of thin plate mirrors (CEP). In hybrid mode additional heat is supplied by heat recovery from the exhaust gases of the engine in series with the solar network and by a separate network recovering heat from the cooling of the engine block at an intermediate temperature level. This paper presents the results of a multi-criteria optimization of a 22 kWe HSPS, including aspects such as energy performance, economic and financial analysis, and environemental aspects. The so called mini-maxi methodological approach with genetic algorithm is used considering three principal criteria such as the energy efficiency of the superposed ORCs, the minimal cost of the installation and the minimum emission of CO2 . Taking into account of the solar radiation time dependence, the elecricity supply variation and the change of configuration (night and day operation), the performance analysis is based essentially on the yearly energy simulation in which the off-design physical models of components are considered. A comparison of HSPS with pure fossil fuelled Plants (DEPU-Diesel Engine Power Unit) is reported for the same electrical power load curve, with an economic sensitivity analysis. Results show that the solar electricity costs are still high and depend considerably on the size of the Solar Field (the HSPS Levelized Electricity Cost with 5 to 16% of annual solar share is about 17% to 49% higher than a similar size Diesel Engine Power Unit). However, a reduction of CO2, emission up to 26% could be obtained when replacing the Diesel Engine Unit by a similar HSPS. Those hybrid solar thermal power systems may already be competitive if a tax of about 42 Swiss cts/kgCO2 would be considered.

2002

Small Hybrid Solar Power System

Daniel Favrat, El Hadj Malick Kane, Diego Larrain

This paper introduces a novel of mini-hybrid solar power plant integrating a field of solar concentrators, two superposed Organic Rankine Cycles (ORC) and a (bio)Diesel engine. Turbines for the organic Rankine Cycles are hermetic scroll expander-generators. Sun tracking solar collectors are composed of rows of flat mirror bands (CEP) arranged in a plane, which focus the solar energy onto a collector tube similar to those used in SEGS plant in California. The waste heat from both the exhaust gases and block cooling of the thermal engine are also heat sources for the ORCs. Such units are considered to meet electricity, cooling and pumping needs of remote settlements in the sun belt areas or on special sites requiring low temperature heating such as swimming pools or greenhouses. The thermal engine guaranties a minimum level of both power and heat availability at night or during cloudy periods. Laboratory tests, made with the superposed ORCs only, confirmed adequate operational characteristics with good performances over a broad range of conditions. A few preliminary tests on the site of the solar power plant when coupled with the engine confirmed a reasonable behavior and the interest of the concept even at part load or during sharp variations of the thermal supply. The performances are satisfactory for a hybrid solar plant of this power range (10 to 25 kWe) and working so far with rather low temperature solar supply (165°C). First Law efficiencies of conversion in hybride mode is of the order of 41% when considerating only the fossil fuel input (total electrical power / LHV of the fuel). This already represents an efficiency increas of close to 50% compared to the Diesel engine alone. These results are encouraging particularly when one considers that excellent prospects exist for further increasing the supply temperature. However due to an over sizing of the turbines and a solar collector efficiency lower than expected, the tests reported here were made at very partial load and the efficiency in mode "solar only" was limited to 7.74%.

2001

Small Hybrid Solar Power System

Daniel Favrat, El Hadj Malick Kane, Diego Larrain

2003

Multicriteria Optimisation of Small Hybrid Solar Power System.

Daniel Favrat, El Hadj Malick Kane

2002

Small Hybrid Solar Power System

Daniel Favrat, El Hadj Malick Kane, Diego Larrain

2001