Despite the high energy consumption of wine making processes, little efforts have been spent so far, both at the industrial and scientific level, to search for alternative energy systems in wine ...cellars. In fact, almost all the existing cellars take electricity from the grid and burn natural gas or other fossil fuels to fulfil their energy demands. This paper analyses the energy demands of a real Prosecco wine cellar in the North East of Italy, which can be considered as a “reference” cellar for dimensions and wine production. The goal is to find the best energy conversion system in terms of maximum profits, efficiency and share of renewable energy utilization. Four alternative design configurations are proposed, and each one optimized considering the three objectives. Results show that a 35% gain in the maximum profits is obtained by including a natural gas fueled CHP internal combustion engine and an absorption chiller. This configuration is also the best one to achieve the maximum efficiency (61%), resulting in 18% reduction of primary energy consumption. Conversely, the utilization of a biomass boiler and an absorption chiller allows maximizing the share of renewable energy consumption, which is about 35% considering the existing availability of biomass from pruning harvesting and the relative limited surface available for photovoltaic generation. This option may become economically interesting when the price of natural gas increases of at least 50%.
The increasing penetration of intermittent renewable sources in power generation at local and building-level poses growing issues in balancing generation and demand. To avoid imbalances, it is ...therefore necessary to ensure adequate levels of flexibility in the building energy system. This can be done both on the generation side, through the coupling of different energy carriers (cogeneration, power-to-heat solutions) and/or the integration of storage systems, and on the demand side, through smart “demand response” programs. This paper considers a tourist facility located in central Germany as a case study to evaluate the energy, economic and environmental benefits that can be obtained from the application of appropriate demand response strategies. The electrical demand data of the facility are monitored at both aggregate and individual load levels and made available by means of a cloud platform. The facility includes two stationary combined heat and power internal combustion engines powered by natural gas and a photovoltaic system. The results show how, thanks to appropriate load management, it is possible, on the one hand, to increase the self-consumption of PV-generated energy and, on the other hand, to keep more constant the load of the engines, which can therefore operate with better efficiencies. This results in both a reduction in energy expenses and a decrease in carbon dioxide emissions attributable to the building.
An effective way to enlarge the utilization of renewable energy consists in creating a correct interface between producers, consumers, and storage devices, i.e., a so-called “energy hub”. This opens ...a difficult challenge, especially in the urban areas where the availability of room for the installation of renewable plants is limited. This paper considers a university campus in the center of Lisbon that requires a significant amount of electricity and natural gas to support the internal activities. The idea is to fulfil part of the energy consumption of the campus with the excess of energy supplied by solar systems installed in the surrounding residential buildings. The goal is to find the number and type of solar equipment that maximize the reduction of annual energy costs of both residents and campus, where the campus is seen as a virtual storage. Results of the optimization show that, considering the best-exposed 100 buildings in a radius of 500 m around the campus, the campus can reduce the annual energy expenses up to 8.61%, whereas the money-saving for the residents is of the order of 24% to 29%, depending on solar exposure. A sensitivity analysis shows also the higher benefits for both the campus and users deriving from expected decreasing costs of photo-voltaic (PV) panels.
Fresh water availability is gradually decreasing and may limit the primary needs of drinking water and irrigation, as well as other activities, such as energy conversion, tourism, etc. A high number ...of desalination plants are being built to provide clean water. One of the main strategies is the brine volume minimization by means of either membrane or thermal processes. The present study focuses on the development of a techno-economic analysis of a Single Effect-Mechanical Vapor Compression (SE-MVC) system for purposes of brine volume minimization. The aim is to evaluate the thermodynamic and economic performances as well as the capital and operating expenditures of the brine concentrator when being part of a near zero liquid discharge (near-ZLD) application. This is achieved by developing the thermodynamic and economic models of the system, which are then combined together in a single integrated procedure. Brackish water analysis is used as starting point for this work. Water properties are modeled using Pitzer's equations as well as correlations found in the literature. The economic evaluation of the investment is performed by calculating the Net Present Value and Internal Rate of Return, key parameters to assess the investment viability of the project. The evaporator model provides the necessary input variables for the economic model. For a feed flow of 10.147 kg∙s-1 and a heat duty of 18080 kW, the annualized capital cost of equipment is 594.93 k€∙y-1, while the operating expenses are 854.40 k€∙y-1 The total annualized cost of the process is 1449.33 k€∙y-1.
Concentrating solar power plants projects have been rapidly increasing over the last few years driven by the advances in the solar technology. The operational issues associated with the variable ...nature of solar energy could be overcome by integrating the solar input into fossil-fuelled power plants. In this paper solar energy is added to the bottoming part of a state-of-the-art three pressure level natural gas combined cycle and parabolic trough, linear Fresnel and solar tower technologies are considered in the search for the optimum integration. Detailed models of the combined cycle and solar field are built in the Thermoflex® environment to evaluate the performance of different integrated solar combined cycle system configurations. Results show how the placement of solar heat addition affects the heat absorption in the heat recovery steam generator and, in turn, the overall system performance. Unlike solar-only power plants which call for the highest temperature concentrating solar technologies to maximize thermal efficiency, the best integration is obtained here using moderate temperature concentrating solar technologies which enable a significant reduction of the heat transfer irreversibility in the heat recovery steam generator. Accordingly, high solar radiation-to-electricity conversion efficiencies approaching 30% are achieved using well-established solar technologies.
•A selected number of integrated solar combined cycle layouts is analyzed.•Parabolic trough, linear Fresnel and solar tower technologies are considered.•In the best layout solar heat is used for evaporation of high pressure saturated water.•High solar radiation-to-electrical efficiencies approaching 30% are achieved.•The exergy analysis explains why some layouts make a better use of solar energy.
Food spoilage represents an urgent issue in tropical developing countries because of the lack of correctly refrigerated post-harvest storage, transportation and distribution facilities. This paper ...searches for the best choice of configuration and design parameters of food refrigeration systems integrated with renewable conversion units in tropical areas using a multicriteria approach (energetic, exergetic and economic). Fourty-four technically feasible integrated configurations are identified for three preservation temperatures of the food (8, 2 and −20 °C). Each configuration is simulated from the energetic, exergetic and economic point of view during one year of operation using detailed design and off-design models. A thermal storage or the connection with the electric grid is considered in the integrated configurations fuelled by solar energy to guarantee a continuous operation. Results show that the PV-powered flash-intercooled compression system is the most efficient integrated configuration for each food storage temperature (annual average COP in the range 2.3–5.7) but it represents the most economically viable option only for the highest food preservation temperature. At lower temperatures, the single-effect absorption cycle coupled with a bagasse-fired boiler shows lower costs because of the very low price of bagasse in tropical countries. On the other hand, all options including the half-effect absorption cycle result to be the less promising in terms of both COP and costs.
•Flesh-intercooled systems show the highest COP (2.2–4.5) for Tfood = 8,2,-20 °C.•Best annual COPs (0.9–2.1) are obtained by compression systems + PV-panels.•Best average annual ηex are of the order of 10% (compression) and 5% (absorption).•Compression systems show the lowest total annual costs (575 to 935€/kWcooling).•Selling the electricity from absorption + biogas-ICE options leads to economic gains.
•The hybrid system efficiency strongly depends on integration point and solar share.•The best design option consists in the by-pass of the highest-pressure preheaters.•Maximum hybrid system thermal ...efficiency (41.31%) is obtained at 7.63% solar share.•A solar field area of ∼0.3 km2 can save 15.4 Mt of coal per year.•Larger areas result in higher fuel savings but lower efficiency.
The integration of Concentrating Solar Power (CSP) technology in large scale fossil-fuelled power plant is one of the best options to promote the necessary transition to a totally renewable electric system starting from the present system. This work provides a complete overview of the possible integration of CSP systems into a real 320 MW coal-fired steam power plant aimed at fuel saving. To this end, detailed off-design models of the existing steam power plant are first built and validated using experimental data measured on the field. Design and off-design models of solar section are then added considering several placement points. Unlike most of the literature, all technical constraints associated with maximum and minimum load of the existing components are also taken into account. The most efficient integration points proposed in the literature plus four new ones are considered in combination with parabolic trough collectors, linear Fresnel collectors or solar towers, for a total of twenty-two different design options. The best integration point results to be in the high-pressure preheater/s: (i) the highest hybrid thermal efficiency (42.67%) is obtained using parabolic trough/molten salt collectors to generate additional high-pressure steam from the drainage water of the last two parallel preheaters (HPH3), (ii) similar thermal efficiencies are achieved in a wide range of solar share (up to 9.1%) by including parabolic through/thermal oil collectors to heat part of the feedwater stream of HPH3 and (iii) 15,400 tons per year of coal can be saved when the solar field area is approximately four times as much the area of the existing coal storage area.
This paper evaluates the thermodynamic and economic performance of four different heat recovery systems (HRSs) applied to two hollow glass furnaces providing 1.2 to 4 MWt of wasted heat at 450 °C. ...Organic Rankine Cycle (ORC), two configurations of supercritical CO2 Brayton-Joule cycle (sCO2) and an innovative regenerative air Brayton-Joule cycle generating compressed air and/or power are modeled at both design and off-design conditions. The aim is to find the most commercially attractive HRS for the considered glass furnaces, as representative of small-to-medium size ones, taking into account all physical and technological constraints. The optimized designs of all systems are first obtained by identifying “average” heat recovery conditions from real data. Off-design simulations are then conducted to predict the behavior of the HRSs considering ambient temperature variations and furnaces ageing process. Results show that the ORC systems are the most attractive HRS available in the market for small-size furnaces while the air Brayton-Joule cycle appears to be the best choice when bigger furnaces are considered. On the other hand, the sCO2 cycle systems show the highest power output in the whole range of furnace sizes while being still penalized by the too high costs deriving by their early-stage pre-commercialization phase.
•ORC is the most commercially attractive technology for small size furnaces.•Air Brayton-Joule cycle system has lowest ROI for medium size furnaces.•sCO2 systems diffusion is hindered by turbomachinery uncertain cost.•Innovative combustion air preheating systems brings high thermal efficiency.
•Dynamic models of many ORC systems allowed suitable control strategies to be found.•The detailed design models of the components are suitable for real applications.•The supercritical two-stage ...system achieves the maximum annual electrical energy.
A diesel-electric propulsion system is generally used in large scale ships to allow a free placement of Internal Combustion Engines (ICEs), to acoustically decouple engines and hull, and reduce total weight and volume. On long voyages, the speed of a vessel can be more or less constant. Thus, to a first approximation, it can be considered that the engines operate most of the time at steady-state conditions. On this basis, Organic Rankine Cycle (ORC) systems can be conveniently installed aboard to generate additional electric power by recovering ICEs waste heat and increase in turn the overall system efficiency. The ICEs-ORC combined cycle system has to be designed properly to maximize the work production and guarantee at the same time a stable operation during both transient and steady-state working conditions.
This paper presents the design and off-design dynamic and steady-state models of three ORC system configurations that exploit the waste heat of four dual fuel diesel ICEs on board a LNG carrier. One single-stage and two (subcritical or supercritical) two-stage ORC system configurations are considered. The available heat is taken from charge air, jacket and oil cooling systems, while the exhaust gases are not considered to be available being already used for other ship internal needs. Dynamic simulations are employed to define the control strategies that lead to stable operation of all the considered ORC system configurations after transients of the ship operation. Steady-state off-design models are then used to identify the best system design point taking into account the real ship operation during a reference year. Results show that the best performing single-stage ORC is designed for a ship speed of 16.5 knots on loaded voyage, and has an annual work production of 1665.8MWh with a peak thermal efficiency of 6.5%. The supercritical configuration reaches the best performance among the two-stage ORC systems, achieving a work production of 2306.6MWh and a thermal efficiency of 12.6% at 15.5 knots.
Energy communities are regulatory tools promoting aggregations of users to foster the shift towards a renewable distributed generation. First in the literature, this paper addresses together three ...main aspects affecting the convenience of these aggregations: the complementarity between generation and demand of different prosumers, the criterion allocating the operating costs of energy communities, and the application of demand-response programs. The goal is quantifying the relative weight of these aspects using Mixed-Integer Linear Programming to minimize the operating costs of citizen and renewable energy communities, where prosumers are connected to the grid as single entity, or separately. Incentive- or price-based demand-response programs and a novel cost allocation criterion, which rewards the members with the highest economic benefit in passing from simple consumers to prosumers, are applied to each community configuration. Results allow identifying general guidelines for the optimal economic operation of energy communities: i) complementarity may reduce costs by 15–20%, ii) a fairer cost allocation criterion may reduce the bills of prosumers using free-of-charge renewables by 20–30% compared to those using dispatchable sources, and iii) price-based demand-response may reduce community costs beyond 50%. Eventually, directions of further research, as the impact of energy communities on a national power system, are drawn.
•Three main aspects affect the aggregation of prosumers in energy communities.•Optimal complementarity of prosumers allows to reduce costs in the range 15–20%.•A novel cost allocation criterion for energy communities is proposed.•Price-based demand response reduces the renewable energy community costs up to 60%.•Citizen energy community has up to 39% lower costs than the renewable energy one.
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