Recently, the research interest regarding ammonia applications in energy systems has been increasing. Ammonia is an important hydrogen carrier that can also be obtained starting from renewable energy sources. Furthermore, ammonia can be used as a carbon-free fuel in combustion systems. In particular, the behavior of internal combustion engines (ICEs), fueled by ammonia, needs to be further investigated. The main disadvantage of this kind of fuel is its low laminar flame speed when it is oxidized with air. On the other hand, considering a spark-ignition (SI) engine, the absence of knock phenomena could allow a performance improvement. In this work, a 1D numerical approach was used in order to assess the performance and the operating limits of a downsized PFI SI engine fueled with pure ammonia. Furthermore, the reliability of the 1D model was verified by means of a 3D approach. Both throttled and unthrottled engine operation was investigated. In particular, different boost levels were analyzed under WOT (wide-open throttle) conditions. The potential of the 1D approach was also exploited to evaluate the effect of different geometrical compression ratio on the ammonia engine behavior. The results show that the low laminar flame speed of ammonia–air mixtures leads to increased combustion durations and optimal spark timings more advanced than the typical ones of SI engines. On the other hand, knock phenomena are always avoided. Due to the engine operating limits, the maximum rotational speed guaranteeing proper engine operation is 3000 rpm, except for at the highest boost level. At this regime, the load regulation can be critical in terms of unburned fuel emissions. Considering increased compression ratios and no boost conditions, even the 4000 rpm operating point guarantees proper engine operation.

Fuel cells, which have seen remarkable progress in the last decade, are being developed for transportation, as well as for both stationary and portable power generation. For residential applications, the fuel cells with the largest market segment are the proton exchange membrane fuel cells, which are suitable for small utilities since they offer many advantages: high power density, small footprint, low operating temperature, fast start-up and shutdown, low emissions, and quiet operation. On the other hand, polymer electrolyte membrane (PEM) fuel cells require high purity hydrogen as fuel. Currently, the infrastructure for the distribution of hydrogen is almost nonexistent. In order to use PEM fuel cell technology on a large scale, it is necessary to feed them with conventional fuel such as natural gas, liquefied petroleum gas, gasoline or methanol to generate hydrogen in situ. This study aims to predict the performance of a PEM fuel cell integrated with a hydrogen generator based on steam reforming process. This integrated power unit will be able to provide clean, continuous power for on-site residential or light commercial applications. A precommercial natural gas fuel processor has been chosen as hydrogen generator. This fuel processor contains all the elements—desulphurizer, steam reformer, $CO$ shift converter, $CO$ preferential oxidation (PROX) reactor, steam generator, burner, and heat exchanger—in one package. The reforming system has been modeled with the ASPEN PLUS code. The model has a modular structure in order to allow performance analysis, component by component. Experimental investigations have been conducted to evaluate the performance of the fuel cell fed with the reformate gas, as produced by the reformer. The performance of the integrated system reformer/fuel cell has been evaluated both using the numerical results of the reformer modeling and the experimental data of the PEM fuel cell.