Renewable Energy Heat Research Articles

Application analysis of green building technology in rural housing

In the process of construction and use of traditional rural buildings in China, the phenomenon of environmental pollution and resource waste is very serious. The introduction and use of green buildings can make natural resources more widely and rationally utilized through scientific overall design. This paper mainly studies the application of green building in rural housing. Firstly, the characteristics of rural green building design are analysed from three aspects: water saving and water resource utilization, energy saving and renewable energy utilization, material saving and greenhouse gas emission reduction. Then, through the detailed introduction of renewable energy utilization technology and clean energy heating and cooling technology, the application of rural green building technology is specified. Finally, the paper summarizes the green design, construction and use strategy system suitable for Chinese contemporary rural buildings. It is hoped that the research of this paper will provide effective reference for the design and use of rural residential green buildings.

Modelling and performance assessment of a two-bed adsorption chiller at different operating conditions

The study aims to assess the performance of an adsorption chiller using the Maxsorb III-methanol as an adsorbent pair. A modified transient lumped parameter model was developed to evaluate the dynamic behavior of the system at various operating parameters. Methanol is used as refrigerant as it has a significant latent heat of evaporation, high normal boiling point, low melting point and environmentally friendly. The results showed that the modified transient lumped parameter model can predict well the dynamic behavior of the adsorption chiller under different operating conditions. The system was able to produce about 13.65 kW (227 W kg-1) cooling capacity with a thermal COP of 0.73 at 85 and 30 oC driving source and cooling temperatures respectively. In addition, simulation tests were made to compare the performance of the Maxsorb III-methanol system with the different working pairs at the same physical dimensions of the present system components and operating parameters. At heat source temperatures of 85 oC which can be gained from waste heat or solar energy, the COP of the Maxsorb III-methanol cycle was about 12.0%, 44.0% and 6.6% higher than that of ACF-ethanol, silica-gel-water and activated charcoal/methanol cycles. The Maxsorb III/methanol adsorption cycle can work effectively with low grade heat sources, which can be gained from renewable energy or waste heat sources.

Modelling and performance assessment of a two-bed adsorption chiller at different operating conditions

The study aims to assess the performance of an adsorption chiller using the Maxsorb III-methanol as an adsorbent pair. A modified transient lumped parameter model was developed to evaluate the dynamic behavior of the system at various operating parameters. Methanol is used as refrigerant as it has a significant latent heat of evaporation, high normal boiling point, low melting point and environmentally friendly. The results showed that the modified transient lumped parameter model can predict well the dynamic behavior of the adsorption chiller under different operating conditions. The system was able to produce about 13.65 kW (227 W kg-1) cooling capacity with a thermal COP of 0.73 at 85 and 30 oC driving source and cooling temperatures respectively. In addition, simulation tests were made to compare the performance of the Maxsorb III-methanol system with the different working pairs at the same physical dimensions of the present system components and operating parameters. At heat source temperatures of 85 oC which can be gained from waste heat or solar energy, the COP of the Maxsorb III-methanol cycle was about 12.0%, 44.0% and 6.6% higher than that of ACF-ethanol, silica-gel-water and activated charcoal/methanol cycles. The Maxsorb III/methanol adsorption cycle can work effectively with low grade heat sources, which can be gained from renewable energy or waste heat sources.

Towards a Cleaner Textile Industry: Using ASEC to Decrease the Water Footprint to Zero Liquid Discharge

Textile manufacturing is the second most polluting industry. It involves a series of processes that require large amounts of water and generates highly polluting wastewater. Four liquid wastes collected at different steps from two different textile factories (synthetic and natural fibers) were treated using a new disruptive technology (Adiabatic Sonic Evaporation and Crystallization—ASEC). After the treatment of the contaminated fluids, the byproducts obtained (freshwater and crystallized solids <1% humidity) were characterized to determine depuration efficiency and their potential commercial reuse. The physicochemical parameters were analyzed in the liquid and solid phases. The results evidence a completely efficient separation of the contaminants and solutes from the liquids analyzed, resulting in 100% pure water with the characteristics of distilled water (an electrical conductivity below 20 µS/cm) suitable for other industrial processes or water reuses, including human consumption. This implies an estimated annual reduction in the water consumption of these factories of between 16 and 103 Olympic pools. It would also avoid the disposal of 181 and 966 ton/y dried residue by the current synthetic and natural fiber textile processing factories, respectively. More than 75% of the resulting solid residue was S from the synthetic fiber industry, and light elements from the natural fiber residues. The installation of ASEC technology in different phases or at the end of industrial textile processing lines could change the paradigm of water consumption to a minimum, thus reducing consumption and resulting in the complete recycling of water. Using renewable energy and residual heat transforms the system into a zero-pollution technology; it makes it possible to attain almost 0% CO2 emissions, fulfilling the European Green Deal objectives such as a circular economy, the decarbonization of the textile industry, the protection of the biodiversity of river basins, and zero pollution.

Capacity determination of renewable energy systems, electricity storage, and heat storage in grid-interactive buildings

If renewable energy systems, electricity storage equipment, and heat storage equipment do not have a reasonable capacity, then a large amount of energy will be wasted even if the supply and demand sides have rational energy scheduling, affecting the safe and stable operation of a power grid. The rational allocation of energy storage equipment and renewable energy systems can significantly improve the power flexibility potential of buildings, save equipment costs, and prevent the occurrence of light and electricity abandonment. In this study, the flexible allocation strategy model proposed in previous studies is modified to determine the reasonable capacity of renewable energy systems, electricity storage equipment, and heat storage equipment in grid-interactive buildings. The modified capacity determination model can also be used to determine the operation strategy of each flexible source under reasonable capacity. Under extreme weather conditions, the upper and lower limits of the power stability coefficients of various cases in this study are 110 % and 94 %, respectively, and the frequency of the extremum is relatively low. The power and thermal flexibility coefficients during the peak period of electricity consumption are both 1, indicating that the flexible potential and utilization are reasonable.

Geological carbon storage in northern Irish basalts: prospectivity and potential

Carbon mineralization and storage in basaltic rock sequences is a developing technology but faces challenges with uptake and increases in scale. Northern Ireland (UK) is a useful analog for many parts of the world where thick basalt sequences could be used to aid in reaching carbon reduction and removal targets. Here I reanalyze and reinterpret available lithological, geochemical, and geophysical data to assess carbon storage potential. The physical and geochemical properties of the basalts are indistinguishable from those used for successful carbon sequestration in Iceland and Washington State (USA). Based on the thickness, composition, and potential permeability, I propose that this is a viable location for a series of small-volume stores (total volume ~9–12 MTCO2) suitable for capture at industrial point-sources or purpose-built CO2 “harvesting” facilities. The case for exploiting the CO2 storage potential in Northern Ireland is strengthened by (1) an increasingly urgent need to find socially and economically just decarbonization pathways needed to meet NI's targets, (2) increasing realization among policy experts that point-source CO2 capture and industrial decarbonization will be insufficient to meet those goals, due in part, to the size of the agricultural sector, and (3) the coincidence with plentiful renewable energy and geothermally-sourced industrial heat. These serendipitous relationships could be leveraged to develop CO2-“farms” where direct air capture operations are supplied by renewable energy (biomass and geothermal) and on-site geological storage. I envisage that these sites could be supplemented by CO2 from locally produced biomass as farmers are encouraged to transition away from raising livestock. Because CO2 can be captured directly from the atmosphere or via suitable biomass anywhere, NI's small size and position on the periphery of the UK and Europe need not be a disadvantage. Instead, NI's access to geological storage, renewable energy, and agricultural land may be a boon, and provide new opportunities to become a leader in carbon removal in basalt-covered regions.

Investigating effect of various time varying load models in grid connected microgrid system integrated with renewables and cogeneration units

ABSTRACT The optimal allocation of sources considering voltage-dependent load models is essential as the power consumption of the loads is sensitive to voltage magnitude. In this paper, optimal allocation of microgrid system with cogeneration units, renewable energy sources (RES), shunt capacitors and heat boiler are determined for constant, residential, industrial, commercial and mixed load models. The cost, emission, energy loss, voltage deviation and voltage stability values for each load model is determined using particle swarm optimisation (PSO) integrated fuzzy max–min approach while the uncertainties in RES are taken into account. Results demonstrate that the cost, energy loss and voltage deviation values are maximum for constant power (CP) load model compared with other load models. Furthermore, the system with constant impedance (CZ) load achieves maximum loading capability than with other types of constant loads. The proposed method is validated on 33-bus grid-connected microgrid system with all the load models.

Design, Integration, and Control of Organic Rankine Cycles with Thermal Energy Storage and Two-Phase Expansion System Utilizing Intermittent and Fluctuating Heat Sources—A Review

In order to lessen reliance on fossil fuels, a rise in interest in the utilization of fluctuating and intermittent heat sources derived from renewable energy (such as solar thermal, ocean thermal, and geothermal) and waste heat has been observed. These heat sources could be used to generate electricity at relatively low and medium temperatures, for example, through the organic Rankine cycle (ORC). In some case studies, various approaches have been developed to deal with and design ORCs in the desired operating condition utilizing suitable working fluids. This article aims to review some designs and integrated systems of ORC with thermal energy storage (TES) and a two-phase expansion system focusing on the utilization of medium- and low-temperature heat sources in which some subcritical ORCs are presented. Moreover, several possible control systems (both conventional and advanced ones) of ORC with TES and a two-phase expansion system are reported and compared. At the end of this article, the possible future developments of design and control systems are discussed to describe advanced ORC for utilizing low-grade heat sources. This study aims to provide researchers and engineers with an insight into the challenges involved in this process, making industrialization of ORC technology more extensive, in particular when combined with TES and a two-phase expansion system.

Supporting climate-neutral cities with urban energy modeling: a review of building retrofit scenarios, focused on decision-making, energy and environmental performance, and cost

Climate deadlines are fast approaching, and city action plans must address slashing carbon emissions using scarce financial resources. Urban energy modeling (UEM) supports building sector transformation by quantifying energy use and emissions in baseline and retrofit scenarios. Additionally, many UEM studies evaluate retrofit costs and financial returns. This review of 26 UEM studies critically analyzes how studies decide to model retrofit measures or impose scenario constraints, and how energy, emissions, and costs are quantified. The results show divergent quantification approaches among the reviewed literature, hindering the usefulness and comparability of the studies for policymakers. The findings also indicate challenges with renewable energy production and heating via heat pumps, including increased peak electrical loads and seasonal mismatches in generation and consumption, which are mitigated by measures reducing building energy demand and energy use, demand-response measures to curtail peaks, and district sources of endogenous energy. The value of the decision-making analysis is to signal pathways toward innovation and stakeholder collaboration for city plans, highlighting approaches using context analysis to generate and share energy in districts, economic criteria to mirror real-world conditions, and stakeholder engagement to meet local priorities. Finally, perspectives for future UEM studies support policymakers guiding the transformation to climate neutrality.

A Multicriteria Optimal Operation Framework for a Data Center Microgrid Considering Renewable Energy and Waste Heat Recovery: Use of Balanced Decision Making

The rapid development of data centers (DCS) leads to a huge challenge in their energy consumption and environmental impact. It is promising to establish DC microgrids (DCMGs) for solving these issues, considering utilizing renewable energy (RE) generation and waste heat recovery systems. However, the efficient energy management of a DCMG is a topic to be pursued. In this article, we propose a multicriteria optimal operation framework for the DCMG by coordinatively scheduling the energy supply and demand. In this framework, multiple criteria are comprehensively considered via a multicriteria optimization (MCO) approach. Then, we adopt an augmented constraint algorithm to address the corresponding MCO problem. Afterward, a balanced decision-making (BDM) method is further proposed to determine the optimal scheduling solution. Finally, a case study and results analysis verify the effectiveness of the proposed multicriteria optimal operation framework for the DCMG.

Increasing Thermal Efficiency: Methods, Case Studies, and Integration of Heat Exchangers with Renewable Energy Sources and Heat Pumps for Desalination

The article presents an overview of modern analytical methods and experimental studies on the use of heat exchangers as part of different schemes, as well as technologies that increase the efficiency of heat exchangers using renewable energy sources. The main types of heat exchangers, and the principles of their operation, are considered. In addition, modern technologies for increasing the efficiency of heat exchangers through design are described. The practical experience of using plate heat exchangers in industry has been studied. An overview of the software development that is used in the design and optimization of heat exchange devices, as well as for the improvement of their energy efficiency, is presented. The presented mathematical models can be used for software that is applicable both to individual segments of plates of heat exchangers and heat exchangers in general, taking into account the dependence of the installation of the entire circuit on environmental parameters and location. In conclusion, recommendations are given for further research directions in the field of using heat exchangers with the inclusion of renewable energy sources. The technique of an energy technology complex, including a heat pump, a photovoltaic panel, and a desalination plant, is presented. The methodology is built around the basic design and energy balance of the complex, and it is also considered from the point of view of the exergetic balance. This allows for the use of additional components, such as a turbo expander for the implementation of the organic Rankine cycle, a wind turbine, and a solar concentrator. This scientific approach can become unified for the design and operation of an energy technology complex. In addition, an exergetic calculation method is presented for a thermal desalination plant operating as part of an energy technology complex with renewable energy sources.

Carbon Neutrality in Municipalities: Balancing Individual and District Heating Renewable Energy Solutions

Carbon neutrality in municipalities can be achieved by combining individual heating and district heating solutions involving the use of renewable energy sources. Each approach has advantages and disadvantages, but the best solution depends on the specific circumstances of each municipality. As an environmentally friendly and efficient energy use, a decentralised heat supply contributes to achieving energy conservation and emissions reduction goals. Decentralised energy use, such as solar collectors with thermal energy storage or biomass as a resource, reduces dependence on centralised heat generation and transmission. The appropriate infrastructure for connection to district heating networks has not yet been built. On the other hand, it is easier to make investments to construct proper infrastructure in the case of large-scale centralised heat supplies. Moreover, a centralised heat supply with renewable energy sources can provide more inhabitants with renewable heat energy. Within the framework of the study, the possibilities of using renewable energy sources in one of the municipalities of Latvia—the Carnikava parish of Ādaži Municipality—are analysed. The study examines two scenario complexes including individual heating solutions in buildings or district heating solutions with a centralised approach. The study evaluates several alternatives to increase the share of RES (solar collectors, biomass, heat pumps, etc.) in the centralised heat supply. To evaluate individual RES solutions in various municipal buildings, this study evaluates alternatives with different technical solutions that increase the use of RES in heat supply.

Investigation of optimization methods for metal foam with two-dimensional porosity gradient in shell-and-tube latent heat storage

The latent heat thermal energy storage (LTES) strengthened by metal foam can promote the development of renewable energy and waste heat recovery. In this study, superposition method and 2D iterative method are established to optimize the 2D porosity gradient of metal foam, which is infiltrated in phase change material (PCM) for heat transfer enhancement in LTES with shell-and-tube configuration. The optimization process in these new methods takes the interaction between horizontal and vertical porosity gradient into account and the evolution of two-dimensional metal foam porosity is numerically investigated. Melting behaviors of optimal cases with different methods are compared and analyzed. The numerical results demonstrated that the optimal case obtained by 2D iterative method has best heat transfer performance. Compared with the uniform distribution, a 11.32 % reduction in full melting time can be achieved by the 2D iterative optimal case due to its better temperature uniformity and stronger natural convection.

Sustainability and carbon neutrality in UK's district heating: A review and analysis

The UK is currently approaching a critical point in the fight against climate change. To achieve carbon neutral by 2050, it is crucial that the way in which buildings are heated are reviewed to determine the most suitable solution. The UK government has acknowledged that district heating (also referred to as heat networks) forms an important part of their plan for future sustainability in heating homes as well as improving energy costs. At present, there are five generations of district heating with distinctive improvements between each. However, research shows a lack of progression with only minor improvements to efficiencies and carbon emissions in the past two decades. Therefore, this paper aimed to review the key technologies and design principles of the low-impact network which shall be implemented into future networks to ensure sustainability and carbon neutral. Furthermore, data were utilised from UK government's ‘Heat Network Project Pipeline’ documents which cover a wide range of projects supported through the development stage by the UK Heat Network Delivery Unit. A statistical analysis was also undertaken to identify popular heat source technologies currently being implemented into the UK networks. Information such as technologies, size and costs were analysed to establish the intercorrelations, which may influence the type of technologies being selected. The results show that 56% of total networks contained Combined Heat and Power (CHP) as a primary heat source, of which over 40% were gas fired CHP, displaying the current dominance of the technology. Overall, it is evident in the UK that, the new networks have been improved from previous generations with a high concentration of renewable energy technologies and heat recovery methods being used. However, there is still a high reliance on natural gas, which does not fulfil the characteristics of a low-impact heating network.

Retrofitting of the District Heating System Based on the Application of Heat Pumps Operating with Natural Refrigerants

The implementation of renewable energy sources and heat pumps with natural refrigerants in the existing 3rd-generation district heating (DH) systems is a promising technology for the conversion to a 4th-generation DH system. This paper aims to investigate this transition through a case study for the existing DH system in Croatia. The district of Rijeka, which is considered in the case study, has an existing 3rd-generation DH system with a capacity of 9.2 MW, which was originally designed for a temperature regime of 130/70 °C and produces thermal energy from natural gas. In order to use heat pumps efficiently in such a system, the temperature of the distribution system and the energy consumption should be reduced. Trnsys software was used to perform complete dynamic simulations of the DH system. Used baseline models were validated according to the actual energy consumption reported by the heat supplier. The application of heat pumps with natural refrigerants in combination with on-site electricity production (PV system) can almost eliminate system CO2 emissions, reduce primary energy consumption and lower operation costs. Simulations were performed for 18 different scenarios that included 2 different building envelope variants. The results were compared, then discussed and conclusions were drawn.

Evaluation of a heat pump coupled two-stage humidification-dehumidification desalination system with waste heat recovery

Humidification and dehumidification (HDH) desalination technology has attracted wide attention in the field of small-scale dispersed fresh water demand, because of its advantages such as simple configuration, low investment, and utilization of low-grade renewable energy and waste heat. In this paper, a heat pump coupled two-stage humidification-dehumidification desalination system with waste heat recovery is proposed, where the waste heat is used to heat the feed seawater of the first-stage humidifier, and the brine leaving the bottom is further heated by the condenser of heat pump and then taken as the feed of the second-stage humidifier, while the evaporator of heat pump is used to recover the heat of humid air from the first-stage dehumidifier. Performance evaluation of the proposed system with various working fluids are conducted regarding the fresh water production mpw, gained output ratio (GOR), recovery ratio (RR), specific entropy generation stot, and unit cost of fresh water production Zpw, and parametric studies are performed to identify the key operating parameters. Results show that the largest entropy generation occurs in evaporator, followed by the first-stage humidifier and condenser. Taking R22 as the working fluids is corresponding to the largest mpw, while the lowest Zpw and stot, and the highest GOR are obtained by R600. Higher spraying temperature of the first humidifier T4 is conducive to improving the mpw and Zpw, but leading to a larger stot. The GOR increases first and then decreases with the rise of T4, and the peak value is 4.57 at T4 = 340.65 K. The mass flow rate ratio of the first stage MR1 has significant effects on the system performance. When MR1 is about 3.5, the mpw, GOR and RR reach the peak. However, the bottom value of Zpw is 8.74 $/m3 corresponding to the MR1 of 2.2–2.5. With the increase of compression ratio (CR) of heat pump subsystem, the mpw, GOR and RR climb up first and then decrease, while Zpw and stot get raised.

Energy Conservation in a Livestock Building Combined with a Renewable Energy Heating System towards CO2 Emission Reduction: The Case Study of a Sheep Barn in North Greece

Cold stress in sheep is usually overlooked, even though the animals’ welfare and productivity are affected by low temperatures. The aim of this research was to find out if and to what extent the temperature inside a sheep barn could be maintained within the range of the thermoneutral zone during winter, primarily to increase feed conversion and to reduce GHG emissions. For this reason, an automation system was installed at a sheep barn in northern Greece, and heat losses from the building were calculated. The biogas potential of the sheep barn waste was examined in the laboratory via the BMP method. The results showed that the installation of an automation system together with a hypothetical biogas heating system could maintain the barn’s temperature in the range of a sheep’s thermoneutral zone during winter for the 94% of the scenarios examined if the total energy of the biogas was utilized, while heating energy that was instantly and continuously used succeeded in 48% of the investigated cases. The surplus of energy produced by biogas could potentially raise the water temperature that animals drink up to 2.9 °C. The absence of cold stress decreases the dry matter intake and the CH4 produced by ruminal fermentation. Moreover, lower GHG emissions are achieved as waste is treated through anaerobic digestion, which would likely be released into the environment if left untreated.

A novel multilevel decision-making evaluation approach for the renewable energy heating systems: A case study in China

Renewable energy (RE) sources are important alternatives to mitigate the energy crisis and achieve sustainable development. Appropriate selection of RE system solutions is extremely crucial. Selection of the best RE technology requires the consideration of conflicting qualitative and quantitative evaluation criteria. Many evaluation criteria are judged with subjectivity and uncertainty. However, the description of uncertainty in the evaluation process remains a large research gap. Therefore, a novel combined evaluation method is developed to describe and visualize the uncertainty in the assessment process. The proposed evaluation method is tested for RE heating system selection. The RE systems are evaluated based on five dimensions and 15 evaluation indicators. This multidimensional indicator framework not only includes the three basic evaluation groups of energy, economy, and environment, but also extends to the performance of technology and policy. The combined weights of the evaluation indicators consist of objective weights and subjective weights. The objective weights are obtained by the Criteria Importance Through Intercriteria Correlation (CRITIC) method and subjective weights are calculated by the improved Fuzzy Analytic Hierarchy Process (FAHP). The set pair analysis (SPA) is introduced to assess the performance of different RE systems. It considers the uncertainty of indicator performance. A novel approach to visualizing the fuzziness of SPA evaluation is developed using the cloud model. Finally, the RE system ranking calculated by the proposed method is performed. The originality of this work is offering a promising method for RE selection and clarifying the degree of ambiguity in the evaluation process. It helps decision makers have an exact idea about the accuracy of the evaluation. It provides insights into multi-objective decision-making problems.

Thermal Performance and Heat Dynamics Energy and Exergy of Integrated Asphalt Collector Storage: Sources of Thermal Energy, and Thermoelectric Energy

Having kilometers of asphalt road, yet with this heat going to waste, an attempt has been made in this research to extract the road's renewable energy heat. The purpose of the experiment is to compare the energy and exergy efficiency of various materials of asphalt solar water heaters (ASWH), as well as heat transmission through the water tube and how friction affects exergy destruction. The water flow rate of one ASWH was 0.01 kg/s, while that of the other was 0.02 kg/s. Each ASWH has an area of 0.5 square meters. The copper tube is buried 10 mm deep in the asphalt. 15 degrees is the angle of inclination. The results indicate that the energy and exergy efficiencies are reasonably high for the water flow rate of 0.02 kg/s. Depending on the water flow rate, asphalt temperature, and sunlight intensity, the energy and exergy efficiencies changed from 32% to 65% and 5.8% to 16%, respectively. The water flow rate is an essential parameter for estimating the internal convective heat transfer coefficient and Reynolds number in order to calculate the friction factor in the copper tube based on internal convection heat transfer. In contrast, the friction factor is a consequence of the pressure loss and exergy degradation induced by friction.

Renewable Energy Heat Source Desing and Modelling

Rising fossil fuel prices and growing environmental awareness are leading to a search for alternative energy sources for heating. This paper deals with the design of a heat source based on the use of renewable energy sources. The aim is to propose an efficient, sustainable, and environmentally sustainable solution that minimizes the negative impact on the environment and contributes to the reduction of greenhouse gas emissions. In the introductory part of this paper, the status and importance of using renewable energy sources for heat generation compared to traditional fossil fuels is assessed. The next section focuses on the detailed design and modelling of such a system, analysing various parameters and factors such as available solar energy, control and regulation system, energy conversion efficiency, heat storage and distribution of the heating system.