To improve energy efficiency in industry, low-grade heat recovery technologies have been advanced continuously. This chapter aims to provide a basic understanding of state-of-the-art technologies for low-grade heat recovery and utilization in industry, which are developed based on the concept of thermodynamic cycles. The technologies include adsorption, absorption, liquid desiccant, organic Rankine cycles (ORC), and Kalina cycles. The definition of low-grade heat sources, the working principle, recent advances in research and development (R&D), and commercial applications of the technologies (if any) will be discussed, followed by concluding remarks on advantages and disadvantages, future outlook, barriers, and opportunities.
Photovoltaic and wind systems have been used for a few years to bring a new power supply to many applications, while preserving the environment. This chapter is interested in this work at low and medium power, a few 100 W, for applications to housing and buildings. The works consider a system in which the various sources of renewable energies are connected to each other in a parallel structure which supposes the use of specialized converters accepting at the input voltages of the order of a few tens of volts, and giving out several hundred of volts. The DC-DC converters with magnetic coupling will be analyzed more particularly to show the technological limits. In particular, the influence of the magnetic circuit and the leakage flows will be studied in more detail.
Biofuels represent a viable contribution in increasing the energy system sustainability. Since a long time, ethanol has been used as a fuel for spark-ignition engines and, nowadays, it is being tested also in compression-ignition engines. Furthermore, in order to exploit the emulsifying properties of gasoline, small amounts of this fuel can be added to the ethanol-diesel blends. Due to the presence of bio-mass derived fuels, and considering that ethanol is an oxygenated fuel, this kind of fuel mixtures, fired in high efficiency engines, could lead to the reduction of both CO2 and particulate emissions. In order to deeply investigate the behavior of the above mentioned mixtures, when they are injected at high pressure in the combustion chamber of Diesel engines, numerical analyses have been carried out by using the AVL-FIRE 3-D code. First, the spray characteristics of diesel fuel, injected into a quiescent chamber in non-evaporative conditions, have been numerically evaluated and the obtained results have been compared to the available experimental data. Later, in order to obtain useful information on both the combustion process and the engine emissions, the behavior of the ternary diesel-ethanol-gasoline blend, injected and fired in a Diesel engine available at the test bench, has been numerically simulated. Referring to the simulations of the combustion chamber of the compression-ignition engine, the most remarkable result shows the combustion of oxygenated fuel blends leads to an important reduction of soot production. Furthermore, using diesel-alcohol mixtures, lower NOx emissions have been observed at the analyzed operating points.
The contribution of this chapter is to deepen and widen existing knowledge on municipal solid waste (MSW) management by analyzing different energy recovery routes for MSW. The main aspects related to the composition of waste are addressed, as well as the technological routes for thermochemical and biochemical energy usage. Within the thermochemical route, incineration is currently the most utilized technology for energy recovery of waste, with generation of electricity and heat and also a decrease in the volume of the produced waste. Gasification and pyrolysis are alternatives for the production of chemical products from wastes. The biological route is an interesting alternative for the utilization of the organic fraction of MSW, as aerobic or anaerobic processes enable the production of biogas and of a compound that can be utilized as a fertilizer. Depending on the size of the population, composition of waste, and products to be obtained (energy or chemical), more than one technology can be combined for a better energy usage of waste.
This chapter book aims to present some key aspects, which play a crucial role to optimize the energy conversion process occurring in microbial fuel cells (MFCs): fluid dynamics and the materials selected as anodic electrodes. MFCs are (bio)-electrochemical devices that directly convert chemical energy into electrical energy, thanks to the metabolic activity of some bacteria. In the anodic compartment, these bacteria, named exoelectrogens, are able to oxidize the organic matter, directly releasing the electrons to the anode surface. The conversion process can be deeply influenced by how the electrolyte solution, containing the carbon-energy source, moves inside the device. For this reason, fluid dynamic modeling is an important tool to explain the correlation between the fluid flow and power output production, optimizing also the overall MFC performance. Moreover, the morphology of anode electrodes results to be essential to guarantee and enhance the bacteria proliferation on them, improving the energy conversion.
