Showing papers by "Umberto Desideri published in 2023"

Hybridizing solid oxide fuel cells with internal combustion engines for power and propulsion systems: A review

Abstract: There has been a growing demand to develop new energy conversion devices with high efficiency and very low emissions for both power and propulsion applications in response to the net zero-carbon emission targets by 2050. Among these technologies, solid oxide fuel cells (SOFCs) have received attention due to their high electrical efficiency (above 60%), fuel flexibility, low-emission, and high-grade waste heat, which makes them particularly suitable for a large number of applications for power and propulsion systems. The higher operating temperatures make SOFCs suitable candidates for integration with an additional power generation device such as an internal combustion engine (ICE) by (a) using the residual fuel of the anode off-gas in the engine, which further increases overall system efficiency to values exceeding 70%, (b) decreasing combustion inefficiencies and (c) increasing waste heat recovery. This paper reviews the published work on hybrid SOFC-ICE systems considering various configurations. It has been found that integrated SOFC-ICE systems are promising candidates over conventional engines and stand-alone SOFCs to be used in stationary power generation and heavy-duty applications (e.g., marine and locomotive propulsion systems). The discussion of the present review paper provides useful insights for future research on hybrid electrochemical-combustion processes for power and propulsion systems. • A critical review of the latest progress in research and development of hybrid SOFC-ICE systems. • Various design and operating characteristics of the hybrid systems are reviewed. • Hybrid SOFC-ICE systems are promising candidates for stationary power generation and marine applications. • Future trends and challenges on technological aspects are discussed.

Research opportunities and challenges in fuel cell science and engineering

Abstract: The fuel cell technology is an emerging technology for electric power generation for stationary, mobile and portable applications. While tremendous technological progress has been made in the last 10 years, it is going to take another 10 years for commercialization and considerable penetration of power generation by fuel cell systems. The most promising fuel cell types are proton exchange membrane (PEMFC), molten carbonate (MCFC) and solid oxide fuel cells (SOFC) while the phosphoric acid fuel cells (PAFC) are commercially available for up to about 200 kW units. Direct methanol fuel cells (DMFC) are considered for portable power applications such as electronic devices. After a brief discussion of these fuel cell systems, the major challenges and research opportunities are outlined for automotive, stationary and portable power generation applications. This includes electrocatalysis, water and thermal management, modeling, and other challenges. The focus is on the R & D needs for each of these fuel cells starting at the cell level, followed by stack level, system level including combined gas turbine and cogeneration systems as well as fuel processing.

Assessment of the optical efficiency in solar collectors: experimental method for a Concentrating Solar Power

Abstract: The amount of incoming solar radiation captured by an absorber in a solar collector is known as optical efficiency. However, applications at medium–high temperatures necessitate thermal insulation of the absorber, which lowers the collector's capacity to absorb solar energy. This fact justifies the requirement for experimental investigation of optical efficiency for all solar devices. This assignment typically entails evaluating the instantaneous efficiency of a solar collector when the absorber and surrounding temperatures are equal. However, this strategy's fundamental disadvantage is that a lack of adequate mass flow rate value might impact heat transmission and lead to misleading results. The significance of this study is to design a more robust and repeatable methodology to assess the optical efficiency of a solar collector. Consequently, this aim proposes the transient heating of the empty collector as an indicator to deduce its optical efficiency, thus avoiding measuring the fluid temperature increase. As a case study, the research methodology experimentally investigated an existing CPC and evacuated pipe to compare the proposed technique with the other based on fluid heating. These methods provided comparable optical efficiency values for airflow rates higher than 5 kg/h with corresponding uncertainties between 7.8 and 9.5% and 5.2–8.6%, respectively.

Thermally integrated pumped thermal energy storage for multi-energy districts: Integrated modelling, assessment and comparison with batteries

Abstract: Integrating large shares of renewables into energy systems requires energy storage technologies able to efficiently dispatch and convert different energy vectors at a local level (multi-energy storage). The paper investigates the performance of multi-energy storage based on the Thermally Integrated Pumped Energy Storage (TIPTES) technology. TIPTES stores electric energy as thermal exergy at temperatures higher or lower than the environment but also exploits additional low-temperature thermal sources, commonly from renewables or waste heat recovery, to boost the charging or discharging phases. In the paper, two different multi-energy TIPTES (mTIPTES) systems are modelled and simulated in three residential case studies where electric and thermal vectors are present, together with solar electric and thermal production. The mTIPTES annual operation is optimised via mixed-integer linear programming, linearising the operating characteristics of mTIPTES components (heat pumps, chillers, organic Rankine cycles and thermal energy storage). Finally, mTIPTES was compared against lithium-ion batteries, a benchmark for residential energy storage. The comparison is based on thermodynamic and economic figures, with the mTIPTES capital cost estimated based on cost models from the literature. The results showed that mTIPTES perform better than the battery from a thermodynamic point of view, reducing the curtailment of renewables. In economic terms, for large penetrations of renewables, this translated into an operating cost reduction of up to around 15 % compared to a system without storage, which is five percentage points lower than what was achieved with batteries. Similar results were found for CO2 emissions and primary energy consumption, for which reductions larger than batteries and up to 20 %, compared to a case without storage, can be found. Despite the operating cost reduction, the mTIPTES total annualised cost (including capital costs) is around double compared to BES, and, for the investigated configurations, mTIPTES could not achieve financial feasibility.

Towards a Power Production from 100% Renewables: The Italian Case Study

Abstract: The need to reduce greenhouse gas emissions is driving many actions to decarbonize the most impactful sectors. Among these, the energy sector accounts for almost one third of emissions. Increasing the penetration of renewable energy in the energy mix could easily reduce the emissions of this sector. Theoretically, the target to aim for would be 100% renewable energy production. However, the variable nature of power production from photovoltaic and wind systems, which are expected to play a key role in the energy transition, may pose several limitations to the effective penetration of renewable energy. Many concerns arise when one considers the large diffusion of renewable energy that would be required to meet green targets, and the operating conditions of other systems in charge of compensating for renewable energy variations. This study aims to investigate the potential impact of an increase in the amount of renewable energy installed in a country, particularly in Italy. A simplified approach has been used, based on the assumption of knowing the hourly demand and power generation mix, and multiplying the intermittent power generation by a certain factor. Although not accurate, this approach allows the authors to highlight some critical aspects regarding the potential surplus of renewable energy and the operating conditions of other energy sources. The results of this study may provide a useful basis for a preliminary system evaluation, in particular to assess the feasibility of surplus recovery and the operability of residual generation systems. In addition, it may be easily replicated in other countries for similar estimations.