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Over the past decades, combined heat and power production (CHP) has proven itself to be an efficient means of meeting both heat and power demands. However, high efficiency can be achieved with CHP plants when the heat load is sufficient, while lower-priority CHP plants must deal with the excess heat associated with power generation. This excess heat can be used for district cooling with absorption chillers. Although the absorption chiller is an efficient technology for using excess heat for cooling generation, its efficiency is very sensitive to driving hot water temperature. This paper provides a detailed analysis of how cooling generation in CHP plants using absorption chillers affects power generation and primary energy consumption. This study is based on the operational parameters of the Mustamäe CHP plant (Tallinn, Estonia) and the cooling demand of the Tehnopol science and business campus and proposes a sufficient cooling production capacity based on the estimation of the campus' cooling demand. Additional cooling production opportunities to meet district cooling demand are discussed and compared in this paper in terms of primary energy savings and economic profit. The study finds that for the effective use of CHP excess heat and efficient cooling production, the use of an 0.8 MW absorption cooler and 11.6 MW heat pumps is recommended. This system would use 1.9 times less primary energy for cooling generation than local cooling. [ABSTRACT FROM AUTHOR]

In this paper, the coupling of a high temperature heat pump with a combined cooling, heat, and power system is investigated. The plant converts the input energy source (natural gas) into electricity and useful thermal energy by means of a cogenerator. Part of the thermal energy feeds an absorption chiller that produces the cooling energy to satisfy the cooling load of an existing industrial building located in northern Italy. The heat pump enhances the low temperature heat from the condenser and absorber of the absorption chiller to high temperature heat to integrate the hot water produced by the cogenerator. The energy performance of the entire plant is analyzed by means of steady-state simulations at both fixed conditions and on an annual operation to meet the heating, cooling, and electric needs of the building varying different parameters and compared to traditional systems for energy production. As the main results, the integrated system provides flexibility and achieves valuable energy performances, in the range of a few tens of percent with respect to benchmark energy production systems. [ABSTRACT FROM AUTHOR]

The electricity required for air conditioning is soaring worldwide. Absorption chillers represent an alternative to classical vapor compression systems, using heat instead of electricity. However, absorption chillers powered by renewable geothermal heat have received little attention so far. This paper introduces a system using a hot geothermal fluid (typically in the range of 80–110 °C) to produce cooling through a single-effect absorption chiller, and Domestic Hot Water (DHW) through a heat exchanger. It considers a hotel located in Martinique, a French Caribbean island. The electric consumption of every subsystem has been thoroughly estimated. The originality of this paper is twice: i) the system is modelled in TRNSYS software considering dynamic conditions, ii) the system undergoes surrogate modelling and multi-objective optimization to minimize both the cost and the CO 2 content of the delivered thermal energy. Several scenarios are considered, depending upon the geothermal temperature, mass flow rate, well remoteness, and demand size. The studied system appears to be systematically more expensive than a combination of a classical vapor compression chiller and a boiler for DHW. However, it can significantly decrease the CO 2 content of the provided energy, especially in an island where most electricity is generated from fossil fuels. The proximity of the geothermal well and the use of the warm water leaving the absorption generator (here for DHW production) appear to be key factors for system relevance, along with a hotter geothermal fluid (e.g., 110 °C instead of 80 °C). • A geothermal absorption chiller in tropical climate is modelled. • The influence of design parameters on electricity consumption is investigated. • The system undergoes multi-objective optimization. • The well proximity and geothermal temperature are keys to the system relevance. [ABSTRACT FROM AUTHOR]

Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the high investment costs and total energy efficiency. This paper aims to discuss the current changes in energy supply and energy prices in terms of the feasibility of the application of a small absorption SHC system in a mild Mediterranean climate. The existing hospital complex restaurant SHC system with evacuated tube solar collectors and a small single-stage absorption chiller was used as a reference system for extended analysis. Dynamic simulation models based on solar thermal collectors, PV modules, absorption chillers and air-to-water heat pumps were developed for reliable research and system comparison. The results showed that primary energy consumption in SHC systems designed to cover base energy load strongly depends on the additional energy source, e.g., boiler or heat pump. Absorption SHC systems can be price competitive to air-to-water heat pump (AWHP) systems with PV collectors only in the case of reduced investment costs and increased electricity price. To reach acceptable economic viability of the absorption SHC system, investment price should be at least equal to or lower than a comparable AWHP system. [ABSTRACT FROM AUTHOR]

The building sector has great potential for contributing to the 2030 EU goals of decreasing greenhouse gas emissions and increasing production from renewable sources. This is even more important considering the increasing cooling energy needs. Among the available technologies, solar cooling (SC) represents a good alternative to traditional electric chillers. However, its use in residential buildings is still limited. The aim of this paper is to analyse the potential of solar cooling system in multi-family buildings. A dynamic model of a complete SC system with auxiliary components was developed in TRNSYS to meet the energy demand of a representative nearly zero energy multi-family building in Italy. The performance of different system design alternatives was analysed in eight different climates with special focus on energy storages. The results show how solar cooling should be optimally designed and provide quantification of achievable renewable energy ratios and related costs in the different climates. • Weather is a determining factor for the design of Solar Cooling (SC) systems. • Solar Cooling represent a valuable alternative for nZEB space cooling. • Dynamic modelling for optimization of thermal storage is crucial to ensure SC performance. • Global design choices should include cost-optimal analysis. • A best design scenario has been identified economically and energetically. [ABSTRACT FROM AUTHOR]

This paper proposes the first application of a split-range control technique on a concentrating solar collector to improve an absorption plant production. Solar absorption plants have solar power availability in phase with cooling demand under design conditions. Thus, it is a powerful cooling technology in the context of renewable energy and energy efficiency. These plants need control systems to cope with solar irradiance intermittency, reject irradiation disturbances, manage fossil fuels backup systems and dump closed-loop thermal-hydraulic oscillations. In this work, control techniques are proposed and simulated in an absorption plant in Spain. The plant consists of a concentrating Fresnel solar collector connected to an absorption chiller. The objectives are to operate with 100% renewable solar energy and avoid safety defocus events while reducing temperature oscillations and control actuators effort. Firstly, the current available plant controllers are defined, then two modifications are proposed. The first modification is a split-range controller capable of manipulating both flow and defocus of the Fresnel collector, the second modification is a PI controller to substitute the original chiller on-off controller. The results compare, through validated models, the different control systems and indicate that using both proposed controllers reduces 94% of the sum of actuators effort and 43% of the integral of absolute set-point tracking error compared to the plant's factory pre-set controllers. The suggested controllers increase 66% of energy production and 63% of exergy production. Besides, the split-range technique can be extended to any concentrating solar collector control. [Display omitted] [ABSTRACT FROM AUTHOR]

In hot coastal regions where fresh water is scarce, absorption chillers driven by industrial waste heat and cooled by seawater are suitable to achieve cooling demands, and it contributes to improving energy efficiency and reducing CO 2 emissions. However, seawater cooling strategy is a trade-off between performance and cost for practical applications, and there are few direct seawater-cooled absorption chillers. In addition, the integration of absorption chillers into a waste heat utilization network is often not well planned, and thus the waste heat is usually not used efficiently. This paper presents the direct seawater cooling strategy for the absorption chiller in terms of high performance and low cost by comparing different seawater cooling strategies numerically and experientially. To realize efficient energy utilization, an existing waste heat utilization network is analyzed graphically based on pinch method, and the available heat for absorption chillers is obtained by the position of the pinch point. According to the available heat, the direct seawater-cooled absorption chiller with a designed cooling capacity of 4200 kW is developed by using titanium tubes, anticorrosive paints and rubber covers to construct the corrosion-resistant condenser and absorber. The site testing results show an average cooling capacity of 3043 kW and an average COP of 0.77 of the absorption chiller when the temperatures of the hot water, seawater and chilled water varies from 98.7 °C to 80.7 °C, from 30.2 °C to 34.2 °C, and from 14.4 °C to 8.6 °C, respectively. Due to the integration, the energy and exergy efficiencies of the waste heat utilization network is improved by 55.9% and 86.1%, respectively. The application demonstrates that the direct seawater-cooled absorption chiller holds the promise for waste heat utilization in coastal regions. • Different seawater cooling strategies for an absorption chiller are compared. • Direct seawater cooled absorption chiller of 4200 kW is developed. • Titanium tubes, anticorrosive paints and rubber covers are employed for anti-corrosion. • The direct seawater cooled absorption chiller is integrated into a waste heat utilization network. • The energy and exergy efficiencies of the network is improved by 55.9% and 86.1%. [ABSTRACT FROM AUTHOR]

Refrigeration systems claim increasing research attention as the climate crisis intensifies. One of the most well-established viable and feasible solutions is solar cooling, as the necessary cooling energy is produced by exploiting the available solar irradiance. The utilization of solar thermal energy to produce cooling energy by absorption chillers fed by a driving heat source (such as solar energy) to produce cooling power. Existing works in the literature present mainly case studies and simulations for small-scale systems (less than 50 kWc). The case study presented investigates the performance of a single-effect 316 kWc absorption chiller under different renewable-only driving heat source scenarios (solar-driven, biomass-driven, and a hybrid approach). The results indicate a significantly advantageous performance in combined heat generation (solar field and biomass boiler connected in series) compared to the scenarios of biomass or solar energy as a sole heat source. Moreover, an absorption chiller's economic indicators appear more fetching than a centrifugal electric chiller of the same capacity, as the payback period is significantly reduced. The Net Present Value (N.P.V. – over 75% greater in the case of absorption chiller compared to the centrifugal electrical chiller) and Return on Investment (R.O.I.) values are increased in the case of the absorption chiller option (18.03% against 15.24% of the centrifugal electrical chiller). The system described in this paper operates in Eastern Macedonia and Thrace, Greece, and is part of one of the largest self-sufficient energy communities. The case study presented is the first attempt at performance evaluation of a large-scale (more than 250 kWc) cooling system operating in a local energy community. [ABSTRACT FROM AUTHOR]

When the typical operation temperature of the Proton Exchange Membrane Fuel Cell (PEMFC) reaches 333.15–363.15 K, the ratio of electrical energy to waste heat generated by the PEMFC is about 1. In this paper, an absorption chiller with LiBr/[BMIM]Cl/CH 3 OH as the working pair is proposed to convert the waste heat into cooling capacity. The PEMFC and absorption chiller (AC) systems have been studied from the energy and efficiency point of view. The COP of the integrated system can reach a maximum of 0.85, which is remarkably 0.35 higher than that of the individual PEMFCs. The electrochemical process of the PEMFC and the thermodynamic process of the AC systems are calculated using MATLAB. The results show that the PEMFC operation temperature of 353.15–358.15K is sufficient to drive the AC and meet the requirement of 273.15–283.15K evaporation temperature and 308.15–313.15K condensation temperature. Meanwhile, when the electric power output from the PEMFC is 100 kW, the AC can output approximately 60 kW cooling capacity, which is sufficient to meet the cooling demand of the commercial bus. • Absorption chiller utilizing low-temperature PEMFC waste heat was proposed. • LiBr/[BMIM]Cl/CH 3 OH was used as a novel working pair in the absorption chiller. • Overall efficiency of the absorption chiller - PEMFC integrated system exceeds 0.8. [ABSTRACT FROM AUTHOR]

Innovative hybrid source for electricity, cooling and desalinated water production based on a mixed fossil fuel/solar energy supply, equipped with triple-component chiller configuration, has been presented in the paper. The system was erected and recently commissioned in King Abdulaziz City for Science and Technology (KACST) in Kingdom of Saudi Arabia to operate as a working laboratory supplying media to adjacent buildings of the Solar Village complex. In the Arabian Gulf region, increased demand, especially for cooling and desalinated water, as well as fluctuating availability of electricity from the grid in summer period is visible, what makes such a stand-alone installation operation justified especially in remote areas. Abundant availability of intermittent solar energy correlated with cooling demand led to development of novel triple-component chiller configuration consisting of absorption, adsorption and compressor chiller. Two Diesel internal combustion engines had been selected to supply electricity and heating when solar energy is not available. Paper presents results of installation commissioning, during which the performance of the system for three different operating scenarios was assessed. Maximum efficiency was achieved for maximum renewable energy production option reaching 324.91% with renewable share at a level of 89.99%. For the maximum cooling capacity production, the efficiency of the system was 124.89% with 18.6% share of renewable energy. The lowest efficiency, of 93.09%, system obtained for the night scenario. • Novel, patented triple-component configuration of chillers has been presented. • Hybrid source for energy and desalinated water production has been commissioned. • Solar panels integration enabled maintaining cooling and distillate production. • Efficiency in max. Renewable energy scenario has reached 325% during commissioning. • Renewable energy share has reached 90% during commissioning. [ABSTRACT FROM AUTHOR]

Distributed generation (DG) using renewable energy sources is of widespread interest. For example, modern centralized conventional fossil fuel power generation commonly adds DG using renewable energy resources to the grid. Therefore, in these changes, it is necessary to optimize renewable energy systems to increase energy efficiency and reduce emissions. In previous studies, meta-heuristic algorithms were used to optimize DG location and capacity, but different types of DG systems and integrated energy hub conditions were not considered. Determining the most effective DG type for an integrated energy hub is critical. Accordingly, this study presented a methodology for selecting the most cost-efficient DG for metropolitan residential customers of energy hubs. In this paper, we model energy hubs for residential customers and the most cost-efficient DG type using MATLAB and HOMER software, considering microturbine (MT), photovoltaic (PV), wind turbine, and fuel cell (FC) power sources. For this purpose, the energy hub was modeled as a combined cooling heat and power (CCHP) system and selected a specific metropolitan area as a testbed (Atlanta, USA). For practical simulation, the total active power of the Atlanta community was measured by multiplying the average load profile data of residential houses collected by open energy information (OpenEI). The first case study showed that optimal-blast MTs without absorption chillers (AbCs) were the most cost-efficient compared to other optimal-blast DG systems without AbCs. Additional second case studies for optimal and full-blast MTs with AbCs were performed to verify the results for energy consumption, costs, and emissions savings. As a result, full-blast MTs with AbCs comprise the most cost-efficient DG type in the CCHP system for metropolitan residential customers, reducing energy consumption, cost, and emissions. [ABSTRACT FROM AUTHOR]