Flexibility Services in a Mediterranean Small Island to Minimize Costs and Emissions Related to Electricity Production from Fossil Fuels

The design of multi-carrier energy systems (MESs) has become increasingly important in the last decades, due to the need to move towards more efficient, flexible, and reliable power systems. In a MES, electricity, heating, cooling, water, and other resources interact at various levels, in order to get optimized operation. The aim of this study is to identify the optimal combination of components, their optimal sizes, and operating schedule allowing minimizing the annual cost for meeting the energy demand of Pantelleria, a Mediterranean island. Starting from the existing energy system (comprising diesel generators, desalination plant, freshwater storage, heat pumps, and domestic hot water storages) the installation of solar resources (photovoltaic and solar thermal) and electrical storage were considered. In this way, the optimal scheduling of storage units injections, water desalination operation, and domestic hot water production was deduced. An energy hub model was implemented using MATLAB to represent the problem. All equations in the model are linear functions, and variables are real or integer. Thus, a mixed integer linear programming algorithm was used for the solution of the optimization problem. Results prove that the method allows a strong reduction of operating costs of diesel generators also in the existing configuration.

In today’s world, it has become ever more important to design homes and buildings with considerations that will reduce the total energy requirement and reliance on fossil fuels. Energy conservation is the first important consideration. The construction and appliance components that reduce energy consumption will be presented. Various systems are being included in the design of this off-grid 100% renewable home. The home will incorporate: passive solar design; solar hot water for radiant heat and domestic hot water; woodburning heat with backup hot water coils for domestic hot water and radiant heat; a hybrid electric system with PV and windmill sources and backup diesel generator (modified to use vegetable oil); a rainwater collection system; a graywater treatment system and blackwater treatment. The heating and air conditioning system combines the efficiency of radiant heat with evaluated tube solar hot water technology. A heating coil is incorporated in a masonry heater as the backup. The sizing considerations of the systems are discussed along with the description of methods to discharge excess hot water. Passive solar building design has been a focal point of the home. The heat gain has been considered as the heating system has been designed. The domestic hot water is discussed to compare the demand vs. production of hot water vs. storage. The practices of the homeowner to minimize the need for air conditioning and the design features that improve the conditioning of the air in the summer are presented. The integration of electrical generation will utilize PV, windmill and diesel generator backup (that will be converted to vegetable oil). This combination is used to take benefit of the wind potential while there are periods of little or no electricity generated from the PV system. The size of the systems has been optimized to balance the cost of production vs. storage. The sizing criteria are presented with the optimization calculations for each of the systems. The system design of a rainwater collection system is presented describing the rain water available, the size of the collection area, and the storage capacity. Equipment considerations are discussed with pre and post storage treatment of collected water. A graywater treatment system is designed to take advantage of the passive solar orientation of the home. The system incorporates graywater management practices, sizing of filtration and discussion of placement of components of the system. A blackwater system is also incorporated in the design of the home. The considerations of various systems are presented along with the sizing and utility requirements. The effective design of a 100% off-grid renewable home must first consider the efficient use of all energy. Secondly, the integration of systems is complex and requires the flexibility of the operations of the systems to produce a range of potential capacity to ensure comfort. The systems incorporated in this design are automated to an extent that is practical, however, monitoring of the systems must be conducted to ensure proper operation.

Experimental investigation of gas bubble diameter distribution in a domestic heat pump water heating system

Integrated Solar Thermal System for Water and Space Heating, Dehumidification and Cooling

During last years, air conditioning demand has spread, both in the commercial and the residential sector. This caused a sensible increase in primary energy consumption. The innovative desiccant-based air handling units are a very interesting solution for air conditioning of buildings as they operate with low temperature thermal energy, such as waste heat recovered from a microcogenerator or especially solar energy. Solar radiation is widely available in summer and simultaneously there are the greatest demands for cooling, but solar energy can be used advantageously also to balance the winter thermal load. In the most common configuration, desiccant cooling system are equipped with a desiccant wheel, in which moist air is dehumidified by the adsorbent material and then cooled down by the evaporation of water and/or through an electric chiller (hybrid plants). A hybrid air conditioning device with silica-gel desiccant wheel is installed in the laboratories of the Universita degli Studi del Sannio (Benevento, Italy), and currently operate coupled with a microcogenerator and a natural gas boiler. The system in its actual configuration can operate only in cooling mode. In this thesis the operation of the experimental air handling unit, considering the coupling of the innovative air handling unit with different solar collectors types (flat plate, evacuated tube, concentrated photovoltaic and thermal collectors), is analyzed through dynamic simulations performed with the commercial software TRNSYS 17. In order to allow the system operation even in winter mode, suitable modifications have been identified and implemented in the model. Furthermore the influence of climatic conditions on the performance of the system is assessed, and also modifications to the air handling unit layout are considered. Finally, for completeness, the system constituted by the desiccant-based air handling unit and the microcogenerator is studied. The innovative air conditioning systems were used to balance the sensible and latent load of a 63.5 m2 university classroom. Moreover, during the intermediate period, in the weekends and whenever there is a surplus of thermal energy the possibility of exploiting this energy in excess for further heating purpose is considered. TRNSYS models were used to simulate the operation of the innovative system and that of a conventional system in order to evaluate operational data and performance parameters. Primary energy saving, equivalent CO2 avoided emission and simple pay back period were evaluated. The performed analyzes showed that the desiccant-based air handling unit fed with a renewable energy source such as solar energy can advantageously replace a conventional air conditioning systems equipped with electrically-driven vapor compression cooling units if only energy and environmental performance are taken into account. However economic feasibility is still hard to obtain. For the considered application economic benefits do not occur together with the advantages mentioned above, although one considers incentives for the production of thermal energy from a renewable source. Only if the use of solar thermal is maximized considering other low temperature heating purposes (for example domestic hot water or swimming pools heating) in addition to the air conditioning economic advantages can take place.

Computational and experimental performance analysis of a novel method for heating of domestic hot water with a ground source heat pump system

Novel energy station by natural fluid <scp> CO ₂ </scp>

Energy, exergy and exergoeconomic analyses of a combined renewable energy system for residential applications

Hospitality buildings are among the highest energy consumers due to their extensive demand for lighting, domestic hot water need, and ventilation, air conditioning and heating (VACH) systems. This study examines the energy-use patterns of hotels in Minna, Nigeria, focusing on consumption trends, management practices, and electricity supply challenges. A mixed-methods approach, combining energy audits, direct observations, and structured interviews was employed. Six hotels were purposively selected in Minna and assessed in this study. Findings indicate that occupancy rates significantly influence energy consumption, with air conditioning and lighting as primary contributors. The study reveals a substantial gap between estimated energy demand and actual supply, leading to heavy reliance on diesel generators. Guests’ behavior was identified as a critical factor in energy wastage, underscoring the need for awareness programs and conservation incentives. The study emphasizes the importance of energy-efficient solutions, including smart VACH systems, sub-metering, and the integration of renewable energy. Addressing these inefficiencies through policy interventions, architectural strategies, and improved energy management practices can enhance sustainability in the Nigerian hospitality sector.

Domestic hot water heat use prediction modelling is an important instrument for increasing energy efficiency in many buildings. This article addressed hourly domestic hot water heat use prediction, using a Norwegian hotel as a case study. Since the information available for buildings may vary, two widespread situations with different input variables were studied. For the first situation, the prediction is based only on data obtained from historical measured domestic hot water heat use. For the second situation, additional variables that affect domestic hot water heat use were applied. These variables were determined using the Wrapper approach. The Wrapper approach showed that factors related to the guests presence have the most significant influence on the domestic hot water heat use in the hotel. Nevertheless, daily data about the number of guests booked at the hotel did not appear to be informative enough for precise hourly modelling. Therefore, to improve the accuracy of the prediction, it was proposed to use an artificial variable. This artificial variable explained the hourly intensity of the guests domestic hot water use. In order to select the best model for the domestic hot water heat use prediction, ten advanced time series and machine learning techniques were tested based on the criteria of models adequacy. For both considered situations, the Prophet model showed the best results with R2 equal to 0.76 for the first situation, and 0.83 the second situation.

This paper identifies and characterizes the technical measures and policy instruments that can be used to promote energy efficiency and the use of renewable sources for domestic hot water (DHW). DHW presents a considerable potential for abatement of greenhouse gas emissions around the world. Measures were characterized in terms of level of transformation, impact and scope, among others. Policy instruments were characterized in terms of target groups, competences required for implementation, major challenges and nature of the instruments. A matrix showing the applicability of policy instruments per technical measure was derived, enabling policy makersto better choose articulated measures and policy instruments for their policy packs.

Trends in research of heating, ventilation and air conditioning and hot water systems in building retrofits: Integration of review studies

Heat is mainly used for space heating purposes, domestic hot water production and air conditioning. In Poland, this represents more than 31 % of the total energy consumption. A quarter of the value above is needed to generate domestic hot water. Heat pumps are considered to be environmentally friendly means of energy generation and they are particularly suitable as a replacement for conventional heating devices in energy upgrading of buildings. They are easy to install and to be integrated into the existing heating systems. The proper choice of such equipment requires taking into account not only the heat demand, but also the local climatic conditions. The paper analyses the coefficient of performance COPbin of the air-to-water heat pump, with CO2 as a working fluid. The pump is applied to the heating of domestic hot water under climate conditions in the city of Kielce recorded in a single year. Heat pump performance at partial loads is also taken into account.

Renewable energy potential analysis in non-interconnected islands. Case study: Isla Grande, Corales del Rosario Archipelago, Colombia

This article has no abstract.