Mario Motta

• Doctor of Engineering
• Head of Department at Politecnico di Milano

Given the strong decentralization of renewables and the raising interest in energy networks (e.g. heat, gas, hydrogen, etc.), spatial detail has become an important feature that energy system models have to take into account. However, a trade-off is needed between systems representation quality and models computational burden, also considering the...

Given the ambitious targets for greenhouse gas emissions reduction set by the European Union and the importance of cities in achieving these goals, there is an increasing need to analyze a city's environmental footprint with a life cycle approach. The life cycle assessment is considered the leading methodology for environmental metrics, permitting...

The aim of this work is to present a fast and accurate district heating simulation tool conceived to support the implementation of successful integrations of renewable energy sources along district heating networks. New generation district heating systems are facing new challenges related to increasing integrations of distributed renewable energy s...

The aim is to assess the impact of the civil sector’s heat demand electrification on the entire energy system, in the Italian case study. The hourly heat demand profiles are estimated at census cells level using the BIN method or monitoring data. Profiles are used as input in the oemof-based NEMeSI model employed to optimize both the capacity expan...

District heating and cooling networks represent a compelling energy system solution due to their capacity to integrate renewable energies and leverage local surpluses of thermal resources. The meticulous design and optimization of network infrastructure are imperative to fully exploiting the potential of these energy systems. The Life Cycle Assessm...

The composition of electricity varies significantly throughout the year. As a result, the environmental impact of the electricity mix is also highly variable. However, most LCA studies assume a static annual average electricity mix and neglect these fluctuations. Therefore, this study examines the time-varying environmental impacts of electricity g...

Net-zero emissions and positive energy districts are innovative urban planning solutions for reaching the decarbonization targets defined by the European Commission. Districts are gaining wide attention representing communities where different elements and energy systems are interconnected, leading to potential opportunities for achieving climate n...

This paper presents a newly developed methodology aimed at assessing at national level the techno-economic potential of district heating (DH) based on renewables and excess heat sources. The novelty of the model lies in the use of an optimization approach to match heat demand and heat sources at large scale level, while keeping a high degree of spa...

Given the paramount importance of a life cycle approach to the building sector and its significant share of the total energy consumption and the subsequent impacts on the economic aspects of the sustainable development goals, this chapter aims to review the current frameworks and provide an introduction for the standard methods of life cycle costin...

The application of life cycle thinking and the life cycle assessment method is becoming increasingly important in Europe, with the decarbonization targets set by the European Commission. Electric heat pumps (vapor compression) are considered one of the most promising solutions for reducing a building’s greenhouse gas emissions. Applying the life cy...

Given the ambitious climate reduction targets of the European Commission for the building sector and the adoption of the life cycle assessment method for the environmental metrics, the authors of this research present a new tool that allows for an extensive evaluation of buildings (operational and embodied environmental profile). The tool developed...

Identifying decarbonization strategies at the district level is increasingly necessary to align the development of urban projects with European climate neutrality objectives. It is well known that district heating and cooling networks are an attractive energy system solution because they permit the integration of renewable energies and local excess...

Increasing concerns over climate change and energy poverty have triggered the transition toward a decentralized energy system through the widespread adoption of renewable energy technologies. Although this transition was led, over past decades, mainly by major investors and large industrial players, citizens and local authorities are increasingly p...

Net-zero climate districts are gaining wide attention at the European and international levels. Urban regeneration competitions have been launched recently to stimulate development; nevertheless, the literature does not yet provide a shared scope definition (i.e., product system). Using the process-based life cycle assessment method, the authors ev...

The hydrogen vector stands as a potentially important tool to achieve the decarbonization of the energy sector. It represents an option to store the periodic excesses of energy generation from renewable electrical sources to be used as it is as a substitute for fossil fuels in some applications or reconverted into electricity when needed. In this c...

This work aims at defining the optimal technological mix which minimizes the total cost of the energy system in 2030 in the Lombardy region, in northern Italy. The goal is reached through a bottom-up model built on a linear optimization problem considering different technical and economic inputs and constraints. Civil sector is one of the sectors t...

Gas-driven absorption heat pumps are a valid alternative to condensing boilers for non-insulated buildings with radiators as emission system. In fact, they can provide high supply water temperatures with a limited performance degradation. However, their seasonal performance is often limited by suboptimal operation at partial load conditions, due to...

Given the ambitious greenhouse gas emissions reduction targets set by the European Union and the importance of cities in achieving these goals, there is an increasing need to analyze their environmental footprint with a life cycle approach. The life cycle assessment is considered the leading methodology for environmental metrics, permitting a holis...

In the energy sector, the issue of what fraction of fuel consumed by an energy conversion plant should be allocated among several products, such as electricity and heat is still open. In this work, procedures used to deal with this aspect in attributional Life Cycle Assessment studies were reviewed. In particular, the authors analyzed three approac...

District heating networks have present and future great potential in decarbonization and in general for improving the environmental profile of the European building sector. It is due to the integration of solar-thermal energy and other renewable sources, flexibility by thermal storage, and mainly the ability to recover industrial and municipal wast...

In this study, the long-term transient response of a single-effect ammonia-water gas-fired absorption heat pump prototype is investigated both numerically and experimentally. For the numerical model, heat and mass transfer components are divided into four groups; (a) tubular heat exchangers comprising condenser, evaporator, absorber, solution and r...

The process of achieving decarbonization and greenhouse emissions’ reduction goals is facilitated and accelerated by the implementation of renewable-based DH rather than multiple individual renewables systems. This work presents an application case that demonstrates how an energy system based on conventional and carbon-emitting heat supply sources...

The goal of this work is to present challenges and opportunities for the development of 4th generation district heating in future decarbonized scenarios for the Italian city of Milano. The work has been developed in the framework of a Climate-KIC project to support Milano municipality in developing decarbonization measures. The first part of the wo...

This manuscript presents the results of an experimental study carried out to evaluate the delay of the transient responses of five capacitive hygrometers with respect to four chilled mirrors. Several experiments were carried out changing the values of air flow rate, temperature, and relative humidity in the test chambers in the RELAB research group...

This work deals with the HVAC systems retrofitting of a residential building located in Valencia (Spain), that is a pilot site in the European R&D project Heat4Cool. Using TRNSYS 17, the proposed layout has been modelled including a solar thermal system and a solar thermally driven adsorption chiller and varying the collectors' surface. The simulat...

Cities and nations worldwide are pledging to energy and carbon neutral objectives that imply a huge contribution from buildings. High-performance targets, either zero energy or zero carbon, are typically difficult to be reached by single buildings, but groups of properly-managed buildings might reach these ambitious goals. For this purpose we need...

This work aims at developing a methodology for the assessment of district heating (DH) potential through the mapping of energy demand and waste heat sources. The presented method is then applied to the Metropolitan City of Milano as a case study in order to investigate the current and, especially, the future sustainability of DH with the foreseen b...

Residential and commercial buildings are responsible for almost 50% of the total electricity consumption in Egypt. This percentage is expected to increase due to the global warming effect. This work deals with the cooling energy use reduction strategies for residential buildings compatible with the Egyptian market accounting for the global warming...

This work aims at showing the unexploited potential of waste and renewable heat in Italy through detailed mapping of these sources. The ambition is to highlight the areas with an important heat recovery potential that could be exploited through DH expansion. The recoverable heat sources have been analysed in terms of geographical location, and reco...

The evaluation of the district heating network investment costs requires the knowledge of its topology. However, when assessing district heating potential, the topology is not known a priori and a simulation is required. One method for modelling future heat networks involves the use of Minimum Spanning Tree, from the graph theory. In this work, the...

The target of the full decarbonisation by 2050 requires high penetration of renewables, with the development of overgeneration situations in the energy system. Hydrogen and electro-fuels could play a key role in hard-to-abate sectors and in grid balancing. By means of the developed NEMeSI model we study the Italian future energy mix, including seve...

Gas absorption heat pumps represent an alternative to condensing boilers for space heating and domestic hot water production in existing buildings. In particular, they enable fuel saving and the exploitation of renewable energy even in heating systems based on radiators, which require high supply temperature. However, in order to provide useful ind...

Robust and fast dynamic simulation tools are crucial for the sizing of the components of complex HVAC system and for the definition of the optimal control strategy. In this work, a first step towards the extension of OpenBPS, a new building energy performance simulation tool, to the dynamic simulation of HVAC systems is presented. In particular, th...

Adsorption chillers can provide energy efficient cooling and have large potential for performance increase and cost reduction compared to conventional chillers. Among the different R&D activities currently in progress in the field, the development of advanced cascading adsorption cycles is an effective way to improve the performance of standard ads...

Multiple-lift absorption cycles are an interesting option for cooling and refrigeration driven by waste or renewable heat. Compared with single effect cycles, they allow higher thermal lift or lower thrust, but they often require the use of controlled valves, which can cause stability and control issues. The self-adapting concept, firstly introduce...

When designing a gas driven heat pump, the selection of the cycle impacts both on complexity and efficiency. Among absorption cycles, the nominal efficiency usually increases with complexity. However, heat pumps are required to operate over a wide range of conditions, of different temperatures and capacity. In this research, three alternative cycle...

Energy efficiency in buildings is a crucial topic to reduce worldwide energy consumption and fight climate changes. A key aspect is the assessment of the heat transfer through the opaque elements of the building envelope. One way to do it is modeling the element as a resistors and capacitors network (RC), using the thermal-electrical analogy. In th...

-The environmental concerns related to global warming and ozone layer depletion along with the growing worldwide demand for heating and cooling have brought an increasing attention toward ecological and efficient Heating, Ventilation, and Air Conditioning (HVAC) systems. Furthermore, since space heating accounts for a considerable part of the Europ...

Development of a reliable and convenient dynamic modelling approach for ground source heat pumps remains as an important unresolved issue. As a remedy, in this work a novel, computationally-efficient modelling framework is developed and rigorously validated. This is based upon an implicit computational modelling approach of the ground together with...

The recent rise of renewable energy technologies in the building sector is expected to reduce fossil fuel consumption but leads to a greater complexity in the design and control of Heating, Ventilation, and Air Conditioning (HVAC) systems. As a consequence, the traditional control approach does not fully exploit the potential of the photovoltaic-as...

In district energy systems planning, the calculation of energy needs is a crucial step in making the investment profitable. Although several computational approaches exist for estimating the thermal energy need of individual buildings, this is challenging at the district level due to the amount of data needed, the diversity of building types, and t...

In the last years, the EU and scientific community put a lot of effort in trying to increase the sustainability in renovated buildings by introducing novel concepts and technologies. This paper presents the outcomes of a retrofit case study carried out within the Heat4Cool H2020 project concerning space heating (SH) and domestic hot water (DHW) sys...

In this work, novel composite silicone-SAPO-34 foams have been prepared and experimentally characterized for application in desiccant open cycles. Water adsorption isotherms of several samples have been measured by a gravimetric dynamic vapour sorption analyser at 30°C and 70°C up to the relative humidity RH= 75%, representing typical process and r...

In the present study, an in-tube vertical falling film absorber with gas and falling film in counter-current flow arrangement, which utilizes NH 3 −H 2 O pair as the working fluid, has been built and is then integrated with a single effect absorption heat pump. Twelve sets of tests have been designed and conducted, taking into account the standard...

The aim of this paper is to present and analyze the monitoring data of an innovative solar Direct Steam Generation plant for industrial processes. The objective is to quantify and evaluate the performance for two different periods of approximatively two weeks each, in winter and in summer. Pressure distribution, pressure drops and liquid level vari...

This work deals with the mapping of industrial excess heat recovery through district heating. In this paper a methodology to estimate industrial waste heat recovery in a given territory is presented and applied. The method is particularly suitable for a relatively large, but limited, geographical region, with a significant number of industrial faci...

This paper presents a new numerical approach to model the heat transmission over long pipes, such as those encountered in district heating networks. The model is suitable for fast and accurate simulation of complex network dynamics. For fast calculation, the model is based on the method of characteristics. For high accuracy, the model splits the wa...

The paper describes the general structure of the PMT_01 tool developed to assess the environmental impacts of different dairy products as Protected Designation of Origin (PDO) cheeses of Lombardy Region (Po Valley - Northern Italy) and High Quality fresh pasteurized milk in a cradle-to-distribution center gate approach. Based on the PEF Product Env...

The aim of this paper is to report on a two-year operational experience with a solar driven desiccant and evaporative cooling (SDEC) system coupled with a vapour compression heat pump. The main objectives are to analyse the benefits and drawbacks of this innovative hybrid SDEC system, to compare the monitoring results against the expected theoretic...

The steady-state mathematical modelling of advanced absorption cycles can be time-consuming and error-prone. In this work, a computer tool based on a modular approach and supported by a comprehensive methodology is described. The solver automatically eliminates redundant mass and species balance equations, detects the existence of paired interconne...

The selection of the proper device for space heating and domestic hot water for a building is crucial to achieve good energy and economic performances. For a single-family house, the most common heating device is the condensing boiler. Solar systems, electric heat pumps and gas driven sorption heat pumps represent suitable alternatives for improvin...

In this work a numerical study is carried out on the addition of the VX concept to the GAX cycle implemented in a commercial gas driven absorption heat pump (GAHP). The performance of the two cycles are compared in terms of Gas Utilization Efficiency (GUE) over a wide range of water temperature and for air temperature ranging from -10°C to 10 °C. T...

Based on recently obtained experimental data, a thermodynamic model for a water-ammonia heat transformer is developed. To conform the model to the real behaviour of the prototype, we called into question a few commonly used assumptions and replaced them with empirical correlations. The result is a tuned model effectively able to give an accurate pi...

A prototype water-ammonia absorption heat transformer has been built and thoroughly tested. Compared to water-salts mixtures, water-ammonia allows operating the machine in a lower temperature range, fostering recover of low-grade heat. Driving temperatures between 60 °C and 64 °C were tested, with condenser temperatures of 8–16 °C. The unit proved...

Large effort has been made to fill up databases of failures and diagnosis for all types of technologies and they will remain open lists as systems are dynamically improving. This paper’s purpose is to provide support in decision making, quantification and diagnosis of failures in temperature sensor signal for a vapor compression system. The main ch...

Waste-heat driven refrigeration technology represents a promising alternative for food preservation on-board, that could help reducing pollutant emissions and, at the same time, limiting fuel consumption. Aim of the present work is the assessment of possible benefits arising from the use of thermally driven systems, with focus on two technologies:...

In the present study, a numerical model of a vertical in-tube falling film absorption heat exchanger utilizing NH3−H2O pair as working fluid is developed. At first, the results of the simulations are validated with experimental data obtained from the absorber of an Absorption Heat Transformer (AHT). Then, in order to comprehend the effect of measur...

This work investigates the use of a water-ammonia double-lift absorption cycle for low temperature refrigeration driven by low-grade heat, as waste-heat or solar energy. Among the various double-lift cycles, the investigation focuses on the self-adapting two-pump series cycle, using water-ammonia as working pair. At first, by means of a numerical i...

This paper describes the methodology and results of monitoring several heat pump systems installed in public buildings in the North of Italy. The three-year project, led by the Energy Department of Politecnico di Milano, aimed at evaluating the performance of heat pump systems on field; it involved several kinds of technologies, including gas drive...

In the present paper, a simulation tool in TRNSYS environment is presented, aimed at assessing the feasibility of two sorption chillers, namely an adsorption activated carbon/ethanol chiller and an absorption ammonia/water chiller, for the air conditioning of a fish storage cell on board of fishing vessels. A case study, typical of Italian fishing...

The use of reliable, representative and reproducible data for the assessment of the quality level of HVAC systems and components on seasonal basis is crucial, especially in view of the obligation of energy labelling, which will be due by the next September, and the market surveillance. An analysis on the current normative framework dedicated to ad...

The study concerns the theoretical investigation of the performances of a fixed-bed adsorption dehumidifier, based on the results of a comprehensive testing campaign. By analyzing the batch operation of the system and fitting the experimental data related to different operating conditions, two semi-empirical formulas have been developed to accurate...

This work deals with the development and testing of a fixed-bed adsorption dehumidifier, designed to manage the latent load in air conditioning. The system is based on the batch operation of two finned tube heat exchangers, where silica gel grains are packed between the fins. The water flow in the tubes provides the required heat supply and rejecti...

Direct Steam Generation (DSG) Concentrated Solar technology, based on Linear Fresnel Reflectors (LFR) and aimed at supplying saturated steam to industrial processes, is a promising application; nevertheless, nowadays few case studies and very few installations have been developed. A methodology for the design optimization of a MW solar DSG plant is...

The experimental analysis of a gas-driven NH3-H2O heat pump whose cycle approaches the GAX concept is carried out. Full load operation is investigated by varying hot water temperatures and partial load operation is investigated by decreasing gas input down to 50% of the full load value. Numerical simulations bolster measurements accuracy and provid...

Double-lift absorption cycles represent a suitable solution for air-cooled thermally driven cooling applications. Among the several existing double-lift configurations, semi-GAX cycles are known as the most promising in terms of efficiency. These cycles incorporate the GAX effect in a pressure staged cycle, by means of a split on the solution leavi...

This is a theoretical and experimental study on porosity and pressure losses in a packed bed of spheres between parallel walls. It is focused on small values of the ratio of the distance p between the walls to the average diameter dav of solid particles: p/dav ⩽ 2. We report a semi-empirical formula for the prediction of porosity of monodisperse pa...

This paper presents a model to simulate the combined heat and mass transfer processes that occur in a gas-fired generator of an ammonia water absorption heat pump. The model comprises three interconnected components: the gas furnace, the distillation column and the rectifier. The furnace is modeled like a well-stirred single volume. The distillatio...

In this work a numerical investigation of the energy needs of the Italian historical building Castle of Zena (XXIII century) and a feasibility study for the retrofit of its HVAC plant is presented. About the building envelope behaviour two types of numerical analyses have been performed. First of all, free floating conditions (no temperature contro...

The aim of this paper is to define and implement a continuous commissioning methodology that can be effectively applied to a solar driven desiccant and evaporative cooling (DEC) system. The objective is to assess the energy performance of the system's components and identify possible operation faults. The methodology consists in the breakdown and a...