Exergetic analysis and dynamic simulation of a solar-wind power plant with electricity storage and hydrogen generation

Abstract

The ambitious vision of off-grid renewable energy autonomy of remote regions has yet to come to fruition. The development of comprehensive energy production systems would be needed to achieve such a goal. This study consists of the simulation and exergetic evaluation of a novel hybrid power plant for stand-alone operation aiming to provide electricity autonomy of a Mediterranean island. The considered power plant is simulated dynamically over an annual cycle and accounts for both energy input fluctuations and electricity surplus. The plant combines a photovoltaic array with wind turbines for energy input, coupled with electricity storage and a hydrogen generation facility for stable output. Unlike other similar studies, the energy system presented here relies on real-case weather and demand data of a relatively large remote community and is optimized to ensure continuous operationeven under extreme conditions. It is seen that this stand-alone hybrid power plant constitutes a robust and secure alternative to the current conventional energy situation; the combined renewable technologies succeed in complementing each other and offer stable performance throughout the year 1 without the requirement of additional support by fossil fuels. The mean annual exergetic efficiency of the plant is found to be 17.9 %, producing approximately 25,000 MWh of electricity per year, along with a secondary product (hydrogen) produced in the electrolyzer of the plant. Although this additional product is associated with additional investment cost, it offers the possibility to stabilize the power plant's performance and can be used as an additional source of financial input to the community.

Capacity Expansion Pathways for a Wind and Solar Based Power Supply and the Impact of Advanced Technology—A Case Study for Germany

“…Selected results were successfully checked based on alternative spreadsheet calculations of the modeling. Furthermore, published studies for selected elements of the approach underline the validity of the presented approach [11,25,31,40,45,59,73].…”

Reviewing energy system modelling of decentralized energy autonomy

“…The methods employed in the reviewed literature (cf. Table 5) range from simple energy balancing calculations (e. g. [71,100,105]) to simulations (e. g. [80,95,103]), metaheuristics (e. g. genetic algorithm [70], discrete harmony search [89], artificial bee swarm optimization [90,91] or flower pollination algorithm [114]), mixedinteger linear optimizations (e. g. [31]) and multi-objective optimizations (e. g. [113]). When investigating the methods, it is striking that in most cases only simplified calculations are carried out.…”

“…As already shown in section 1, however, costs are not the only reason for energy autonomy projects. In a few studies, a different target criterion than costs is applied, but these analyses do not represent an improvement since also only one criterion is considered: technical feasibility [86,117], annual efficiency [103,104] or coal consumption [130]. However, beside the above-mentioned MCDA approaches, other multi-objective approaches represent improvements.…”

“…Further studies try to robustly design off-grid energy systems by taking extreme conditions into account. In Petrakopoulou et al [103,104], the plants of the energy system are over-dimensioned and complementary technologies are used. In addition, the optimization model in Weinand et al [8] considers extreme days on which demand is particularly high and no wind or solar radiation is present.…”

“…As shown in Table 9, diesel, therefore, is the most frequently considered in the studies after PV, wind and stationary batteries. [35][36][37]66,70,85,91,115,116,134], these uncertainties are at least addressed via LPSP and in another study [103] by including extreme conditions. Even more than in other studies, the results of the completely autonomous energy systems in Al-Shetwi et al [32], Khan et al [76], Kim et al [77] and Mas`ud [137] must therefore be questioned, in which only volatile energy technologies and no uncertainties are considered.…”