• Energy Research

The revamping of existing high temperature district heating systems with low temperature solutions will ensure a better usage of primary energy thanks to the reduction of thermal losses through the networks and to the possibility of use low grade enthalpy heat for the scope, including renewables and waste heat. However, several criticalities are present that make the evolution from the 3rd to the 4th generation of district heating not immediate. The paper aims to identify general technological and non-technological barriers in the revamping of traditional district heating networks into low temperature ones, with a particular focus on the Italian framework. Possible solutions are suggested, including also relevant advices for decision makers. Furthermore, the paper analyses how the possible solutions required for the up-grade of the existing district heating network can be classified through the Analytic Hierarchy Process (AHP) to prioritize the best resulting ones for more advanced evaluations. International Journal of Sustainable Energy Planning and Management, Vol 20 (2019)

The paper deals with the main features of an experimental pneumatic conveying plant developed at University of Bologna Lab. The main goal of this plant is to characterize transport properties of bulk solids conveyed in pneumatic plants. The facility is designed and instrumented to give information on flow conditions along the whole pipeline. The installation has all main characteristics of an industrial conveying plant, to supply with data comparable with those running in industrial process. It is also paired with a similar plant built in Reggio Emilia, Italy (a cooperation between Ariostea S.p.a. and University of Bologna), that completes the range of pneumatic conveying typology which can be analyzed. Measures, obtained during test runs, allow to validate prediction of a mathematical model developed to assist conveying plants design. To improve results given by the system, a strategy have been worked out, which allows to monitor many points of the plant by a smaller number of instruments. The communication between control system, instrumentation and actuators is realized by a Profibus DP/PA network, managed by a dedicated software developed in Visual Basic

Abstract Fine particulate matter (PM) emission from biomass boilers for non-industrial heating represents one of the most important causes (together with the transport sector) of air pollution, in particular during winter. Separation technologies for fine PM are already well-known and adopted on an industrial scale, as a consequence of strict limits set by national and international regulations. On domestic boilers, the same technologies utilized on an industrial scale are not feasible due to high investment costs. Moreover, the emission limits for small size biomass boilers are higher than for industrial boilers, so high efficiency separation technologies are not needed, and are sometimes not present at all. The main goal of the paper is the development and testing of a mathematical model that is able to foresee the PM removal efficiency of a wet scrubber device. After an experimental validation based on several tests, it was possible to approach the preliminary design of an innovative wet scrubber, which is described in the paper. The main characteristics are (i) removal efficiency over 99.9%, (ii) specific energy consumption under 36 kJ m−3, which is an industrial reference, and (iii) relatively low investment, operation and maintenance costs.

One of the most critical greenhouse gases in the atmosphere is carbon dioxide (CO2) due to its long-lasting and negative impact on climate change. The global atmospheric monthly mean CO2 concentration is currently greater than 410 ppm which has changed dramatically since the industrial era. To choose suitable climate change mitigation and adaptation strategies it is necessary to define carbon dioxide mass distribution and global atmospheric carbon dioxide mass. The available method to estimate the global atmospheric CO2 mass was proposed in 1980. In this study, to increase the accuracy of the available method, various observation platforms such as ground-based stations, ground-based tall towers, aircrafts, balloons, ships, and satellites are compared to define the best available observations, considering the temporal and spatial resolution. In the method proposed in this study, satellite observations (OCO2 data), from January 2019 to December 2021, are used to estimate atmospheric CO2 mass. The global atmospheric CO2 mass is estimated around 3.24 × 1015 kg in 2021. For the sake of comparison, global atmospheric CO2 mass was estimated by Fraser’s method using NOAA data for the mentioned study period. The proposed methodology in this study estimated slightly greater amounts of CO2 in comparison to Fraser’s method. This comparison resulted in 1.23% and 0.15% maximum and average difference, respectively, between the proposed method and Fraser’s method. The proposed method can be used to estimate the required capacity of systems for carbon capturing and can be applied to smaller districts to find the most critical locations in the world to plan for climate change mitigation and adaptation.

This paper describes an innovative process to increase superheated steam temperatures in waste-to-energy (WTE) plants. This solution is mainly characterised by a fluidised bed reactor in which hot flue gas is treated both chemically and mechanically. This approach, together with gas recirculation, increases the energy conversion efficiency, and raises the superheated steam temperature without decreasing the useful life of the superheater. This paper presents new experimental data obtained from the test facility installed at the Hera S.p.A. WTE plant in Forlì, Italy; discusses changes that can be implemented to increase the duration of experimental testing; offers suggestions for the design of an industrial solution.

Optimizing the hydrogen value chain is essential to ensure hydrogen market uptake in replacing traditional fossil fuel energy and to achieve energy system decarbonization in the next years. The design of new plants and infrastructures will be the first step. However, wrong decisions would result in temporal, economic losses and, in the worst case, failures. Because huge investments are expected, decision makers have to be assisted for its success. Because no tools are available for the optimum design and geographical location of power to gas (P2G) and power to hydrogen (P2H) plants, the geographic information system (GIS) and mathematical optimization approaches were combined into a new tool developed by CNR-ITAE and the University of Bologna in the SuperP2G project, aiming to support the interested stakeholders in the investigation and selection of the optimum size, location, and operations of P2H and P2G industrial plants while minimizing the levelized cost of hydrogen (LCOH). In the present study, the tool has been applied to hydrogen mobility, specifically to investigate the conversion of the existing refuelling stations on Italian highways to hydrogen refuelling stations (HRSs). Middle-term (2030) and long-term (2050) scenarios were investigated. In 2030, a potential demand of between 7000 and 10,000 tons/year was estimated in Italy, increasing to between 32,600 and 72,500 tons/year in 2050. The optimum P2H plant configuration to supply the HRS was calculated in different scenarios. Despite the optimization, even if the levelized cost of hydrogen (LCOH) reduces from 7.0–7.5 €/kg in 2030 to 5.6–6.2 €/kg in 2050, the results demonstrate that the replacement of the traditional fuels, i.e., gasoline, diesel, and liquefied petroleum gases (LPGs), will be disadvantaged without incentives or any other economic supporting schemes.

Abstract Biomass boiler plants of small thermal power (under 35 kW thermal), in particular for domestic heating, have greatly contributed to the rise in particulate emissions. Several technologies, like fabric filters or electrostatic precipitators, can achieve high particulate removal efficiency, over 99%. However, the application of these technologies is limited by excessive prices and operational problems, since the high cost does not allow their use in small size plants. The paper shows a comparative performance analysis of different scrubber systems which have been designed, realized and tested with flue gas produced by biomass combustion in a 25 kW thermal boiler. The experimental campaigns were realized in the laboratory of the Department of Industrial Engineering of the University of Bologna. Experimental results demonstrate the achievements of particulate removal efficiency which is comparable with the efficiency of industrial technologies. Moreover, a preliminary energy balance was carried out to assess the energy cost of the different scrubber systems tested.

This paper describes the context, the basic assumptions and the main findings of a joint research project aimed at identifying the optimal breakdown between material recovery and energy recovery from municipal solid waste (MSW) in the framework of integrated waste management systems (IWMS). The project was carried out from 2007 to 2009 by five research groups at Politecnico di Milano, the Universities of Bologna and Trento, and the Bocconi University (Milan), with funding from the Italian Ministry of Education, University and Research (MIUR). Since the optimization of IWMSs by analytical methods is practically impossible, the search for the most attractive strategy was carried out by comparing a number of relevant recovery paths from the point of view of mass and energy flows, technological features, environmental impact and economics. The main focus has been on mature processes applicable to MSW in Italy and Europe. Results show that, contrary to a rather widespread opinion, increasing the source separation level (SSL) has a very marginal effects on energy efficiency. What does generate very significant variations in energy efficiency is scale, i.e. the size of the waste-to-energy (WTE) plant. The mere value of SSL is inadequate to qualify the recovery system. The energy and environmental outcome of recovery depends not only on "how much" source separation is carried out, but rather on "how" a given SSL is reached.