Renewable Heat Research Articles

The “four Ds” and support for Local Smart Grids: analysis from national surveys in the UK and Canada

AbstractLocal Smart Grids are emerging during the climate crisis, as governments and industry recognize the need to better integrate intermittent renewable energy, storage, transportation, heating, and smart technologies. Such projects can represent profound changes to the status quo of energy and citizen lifestyles. They are also being associated with the “four Ds,” whereby Local Smart Grids are decarbonizing, decentralizing, digitalizing, and potentially democratizing energy systems. Yet, due to their recent arrival, there is very little social scientific research that has aimed to better understand public views, expectations, and support for this change. We attempt to fill this important gap in the literature through the analysis of two nationally representative surveys in the UK (n = 3034) and Canada (n = 941). This analysis highlights within- and between-country trends, including how the variation in responses regarding the “four Ds,” demographic factors, and other variables may explain the differences we see in terms of support for energy system change in the UK and Canada. Our analysis also shows that there are common elements, including the importance of the decentralization, and especially the democratization of energy in shaping support. We hope that this study will help governments, industry, community groups, and local residents themselves in both countries come together to advance the kind of Local Smart Grids that address climate change and represent a supported, just energy transition.

Optimizing energy hubs with a focus on ice energy storage: a strategic approach for managing cooling, thermal, and electrical loads via an advanced slime mold algorithm

Abstract Amidst the increasing incorporation of multicarrier energy systems in the industrial sector, this article presents a detailed stochastic methodology for the optimal operation and daily planning of an integrated energy system that includes renewable energy sources, adaptive cooling, heating, and electrical loads, along with ice storage capabilities. To address this problem, it applies the 2 m + 1 point estimation method to accurately assess system uncertainties while minimizing computational complexity. The “2 m + 1 point” technique swiftly evaluates unpredictability through Taylor series calculations, capturing deviations in green energy output, and the demand for both electric and thermal energy across power networks, while also considering the oscillating costs associated with senior energy transmission systems. In addition, this article proposes a novel self-adaptive optimization technique, called the enhanced self-adaptive mucilaginous fungus optimization algorithm (SMSMA), dedicated to overcoming the intricate nonlinear challenges inherent in the optimal daily operation of an energy system. The advanced self-adaptive strategy relies on wavelet theory to enhance the capability and effectiveness of the original mucilaginous fungus algorithm in optimizing daily schedules for an integrated energy system. Numerical analyses demonstrate that the introduced stochastic daily scheduling framework, coupled with the SMSMA optimization algorithm, effectively reduces the operating costs of the energy system.

Modelling and Experimental Characterisation of a Water-to-Air Thermoelectric Heat Pump with Thermal Energy Storage

Nowadays, increasing the penetration of renewable heat technologies is an important approach to minimise global primary energy use and reduce CO2 emissions for a sustainable future. Thermoelectric heat pumps, which have some unique characteristics in comparison with conventional vapour compression heat pumps, can be integrated with solar thermal energy storage to form a promising renewable heat technology. However, currently, a reliable numerical model for TeHPs suitable for building energy simulation is lacking and the benefits achievable for a TeHP thanks to the integration with heat storage are unclear. To solve these issues, in this work, an experimental apparatus consisting of a water-to-air TeHP unit with a heat storage tank is modelled and tested for the first time, under the scenarios with thermal energy storage and without thermal energy storage, respectively. The results found that the developed numerical model could well predict the output performance of the TeHP unit, with deviations within 12%. Additionally, the output performance of the TeHP unit when combined with a heat storage tank is better than that of the TeHP unit without heat storage, in terms of the maximum temperature achieved in the testing box, the temperature response speed of the testing box, and the coefficient of performance (COP) of the TeHP unit. This work not only paves the way for the following building-integrated simulations of TeHP units, but also provides guidance for the design of the integrated systems that include TeHPs and thermal energy storage.

Evaluation of potassium glycinate as a green solvent for direct air capture and modelling its performance in hollow fiber membrane contactors

Current direct air capture (DAC) technology is largely cost-prohibitive for large scale implementation due to the excessive energy required to operate a combined absorption–desorption cycle. As the desorption process consumes much of the supplied energy, there is a demand to find more sustainable sorbent materials that maintain high absorptive capacities yet can be regenerated at lower working temperatures. This work evaluates potassium glycinate (GlyK) as one such alternative absorbent. Through conducting vapor–liquid equilibria and wetted wall column kinetic studies, GlyK is found to have comparable working capacities and liquid mass transfer coefficients to those reported for the industrial standard, monoethanolamine (MEA), yet outperforms it with regards to its distinctly low regeneration temperature. To further understand how GlyK would perform in an industrial scale DAC system, an Aspen Custom Modeler® (ACM) model is developed that integrates the experimentally obtained equilibria and kinetic data with the performance characteristics of a gas-solvent hollow fiber membrane contactor (HFMC). Full-scale simulations show that via implementing a 20°–90 °C absorption–desorption cycle, GlyK can capture up to 83 % of the CO2 in atmospheric air and be 55 % regenerated within a single membrane contactor pass. As these low working temperatures vastly outperform the conventional ∼ 40°–140 °C temperature swing currently implemented in industrial CO2 processing, GlyK is concluded to be a viable and sustainable option for use within energy-efficient DAC technology whereby renewable heat sources can be used.

Trends for Stirling Engines in Households: A Systematic Literature Review

Reliable heat and power supply are among the basic household needs nowadays. It is especially topical in rural or distant locations that may be cut off from the energy grid due to extreme weather or other events. Nonetheless, the sustainability of our power production systems has to be considered to sustain our planet’s long-term abilities to provide energy resources and a viable environment. Renewable energy resources must be prioritized in rural and remote areas, simultaneously strengthening distributed production ability and self-sufficiency. In this context, the use of the Stirling engine for heat to power generation in households, on the scale of small communities, and by using only renewable resources is becoming increasingly topical. Therefore, this research aims to identify the current state-of-the-art for Stirling engine applications using biomass as a renewable energy source, in the context of sustainability and energy security. The paper summarizes the current research tendencies at the household level in the use of biomass-based Stirling engines for renewable heat and power generation in decentralized energy systems. The methodology applied is a structured literature review and content analysis. The research results corroborate the progress towards the use of renewable resources and towards increased energy efficiency because the keyword and overlay analysis showed more frequent publishing in these areas. The content analysis on two more specific sub-directions of interest, i.e., biomass-fuelled Stirling engine use in households and Stirling engine implications on energy security, showed that though research activity in these directions has increased lately, more profound research is needed, especially on aspects of energy security and independence. The content analysis revealed a lack of in-depth analysis on the effects of Stirling engine use on energy security or energy independence, which is suggested as a topical subject for future research.

The techno-economics of transmitting heat at high temperatures in insulated pipes over large distances

This study reports a systematic techno-economic assessment of the cost-optimal transmission for air as the heat transfer fluid at temperatures of up to 1200 °C, at scales of 1 to 1000 MW and at distances of up to 10 km. It employs a steady state heat transfer analysis, with energy balances, to assess the effect of scale, temperature and insulation on the heat losses and efficiency of the thermal transmission system, following by a techno-economic assessment. The sensitivity of the Levelised Cost of Heat, LCOHtr, to variations in thermal scale, operating temperature, distance, refractory and insulation thickness, ratio of the thickness of refractory and insulation, cost of any supplementary heat and lifetime is reported. The results show that LCOHtr decreases with an increase in thermal scale, as expected. The role of insulation is much more complex, since increasing the thickness of thermal barrier increases both cost and efficiency of the transmission, requiring an economic optimum to be determined for each of the various conditions assessed. Parameters are also coupled because a higher cost of supplied energy/ heat justifies the use of more insulation material. For a large GW scale thermal system, we estimate that it is possible to achieve a minimum overall LCOHtr,min of 0.16–0.36 USD/GJ/km of the length of the thermal transmission system, excluding additional location-specific costs such as land-access and local construction costs. These estimated costs are sufficiently attractive to justify ongoing development of systems to transport renewable heat to industry from sources such as concentrated solar thermal energy.

REVIEW OF MONITORING TECHNOLOGIES USED IN HYBRID PHOTOVOLTAIC SYSTEMS

In the present context, due to the increase in global energy demand and the need to reduce greenhouse gases, hybrid systems that produce electricity and heat from renewable sources have been proposed, designed and implemented. Most of the available solar energy is captured using photovoltaic systems and converted into electricity. Today's modern systems refer to combinations of photovoltaic and thermal panels (PV/T) to obtain electricity and domestic hot water, and systems consisting of photovoltaic panels with wind turbines which provides only electricity. With an optimal design, PV/T systems can provide buildings with 100% renewable electricity and heat. This is done in a more cost-effective and efficient way compared to using photovoltaic and solar thermal systems separately. The areas required to install photovoltaic systems can be reduced by using hybrid energy production systems. The introduction of a hybrid photovoltaic-wind system reduces the land area from 1.5 ha/MW to 0.4 ha/MW. Due to the influence of environmental factors affecting the functionality of hybrid systems and the need to achieve optimal performance, the development and implementation of advanced monitoring methods has become a mandatory requirement. The paper presents different methods of monitoring hybrid systems, their progress and performance.

Multivariable QFT Controllers Design for Heat Exchangers of Solar Systems.

This paper addresses the control of a heatexchanger placed in a solar water heating system and influencedby external disturbances at plant output. Heat exchangers playan essential role in industries that use renewable sources forenergy generation and water heating, i.e. geothermal, solar,ocean, etc. One of the main control targets of such systems is toachieve a simultaneous and accurate control of sometemperatures. A multivariable (MIMO) model of the heatexchanger of a solar plant, and a robust controller able togovern the system despite the external disturbances and loopinteractions are developed in this work. The MIMOmethodology for the non-diagonal controller design is based onthe Quantitative Feedback Theory (QFT).

ПРИМЕНЕНИЕ МЕХАТРОНИКИ В ПРОИЗВОДСТВЕ И АВТОМАТИЗАЦИИ

The article is devoted to the study of the application of mechatronics in production and automation. The main principles of mechatronic systems, their integration into production processes, the use of robotics, sensor technologies and adaptive control systems are considered. Methods for increasing the energy efficiency and sustainability of mechatronic systems are analyzed, including the introduction of renewable energy sources and heat recovery technologies. Modern innovations such as artificial intelligence, 3D printing and the Internet of Things are discussed. Examples of successful application and forecasts for the development of technologies are given, and the economic and practical benefits and challenges associated with the integration of mechatronics into production are assessed.

Optimising Resource Utilisation: A Case Study on Oleofinos’ Advanced Line 4

This study presents significant advancements in the refinement of vegetable oils, demonstrating a 40% increase in processing capacity and a 30% reduction in production time. Additionally, energy consumption was reduced by 25%, leading to a 20% decrease in greenhouse gas (GHG) emissions. These improvements are attributed to the implementation of renewable energy technologies and heat recovery systems. With these advancements, Oleofinos has enhanced its safety and quality standards, maintaining the FSSC 22000 Certification for Food Safety Risk Management and the Rainforest Alliance Certification, which is recognised as the world’s leading certifier under the Forest Stewardship Council® (FSC®) with over 25 years of experience in environmental certification. Currently, Oleofinos is the largest plant of its kind in Mexico, boasting an unprecedented processing capacity of 500,000 tonnes per year. The results of this study underscore the significance and transformative impact of research, establishing a benchmark for future initiatives aimed at process improvement in the sector and reinforcing the commitment to operational excellence and environmental responsibility.

Investigation of solar air collectors with concave air duct

In this article study attempts to study the thermal performance of solar air collectors with submersible air ducts and pipes. This study is conducting numerical analysis of the solar collector with pin wings and turbulators to study the effects on the Nusselt number. The paper begins with a numerical analysis of conventional air collectors and compares them with theoretical results. Reynolds numbers range from 2000 to 2500. Next, after the solar collector's performance is evaluated with the bath air with channels, the effects of turbulators of different heights on the Nusselt number are analyzed, followed by the combined effects of pin wings and turbulators. The results are comparable to conventional solar collectors, and suggest that the combined effects of pin wings and turbulators can significantly improve the thermal performance of solar air collectors. The results of this study may contribute to the development of renewable energy-based air conditioning, ventilation and heating systems.

RESEARCH OF HEAT GENERATION AND CONSUMPTION MODES IN COMBINED HEAT SUPPLY SYSTEMS USING ALTERNATIVE ENERGY SOURCES

Alternative energy currently has all the technical means that allow it to be considered a classic addition to traditional methods of energy production. Modern energy technologies require a more effective and reliable solution to the problem of energy supply based on the integrated use of various types of renewable energy sources, energy accumulators of various types, heat pumps, combined means of thermal modernization of buildings and alternative fuel energy backups. In modern heat supply systems using alternative energy sources, usually at least 2 heat sources are used - a renewable heat source and a traditional source as reserve and peak. The operation of gas, solid fuel, pellet and electric boilers, solar collectors, various types of heat pumps in the heat supply systems of buildings and civilian buildings is analyzed. The high-quality operation of the heat supply system is affected by various schemes of connecting consumers to heat generators. The specifics of the effective operation of the combined heat supply system are the coordination of various hydraulic “generator-consumer” modes. In practice, three approaches are used to coordinate the modes of operation of alternative heat supply systems with consumers: regulation of the power of the heat source, programming of heat consumption modes, introduction of heat accumulators. It is important to find out the conditions for the effective use of heat accumulators for intermittent heating mode, which can ensure a decrease in the thermal power of a heat generator operating in superheat mode. The operation of the pilot plant of the integrated system of alternative heat supply (ISAHS) was studied, the technical and economic indicators obtained for the heating period for three different types of heat generators: gas boiler, pellet boiler, heat pump were analyzed. An experimental study of the combined heat supply system for various heat supply facilities made it possible to establish that for public buildings, a rational way to increase their efficiency is the use of intermittent heating modes, a two-stage storage system, and coordination of structural and mode parameters of the main contours of the system. Keywords: combined heat supply system, boiler, solar collector, heat pump, heat accumulator

Energy supply for the building stock of tomorrow – A case study

Reducing energy consumption and using renewable energy sources for the building operation is crucial to achieve lower overall greenhouse gas (GHG) emissions. In this case study we conduct a building energy system optimisation for a new residential district in Darmstadt, Germany under different boundary conditions using the optimisation software Sympheny. Boundary conditions of the year 2023 lead to similar results to the owner’s plan, which is mainly based on natural gas-fired cogeneration plants. However, different scenarios with predicted emission factors and energy prices for 2050 lead to a shift towards the usage of renewables. As planners tend to use current boundary conditions for their calculations, we assess the possibility of switching to a renewable heat supply after the expected life span of the cogeneration plants. The obstacles identified mainly concern the temperature level, but also the space that will not be accessible at that time. The results emphasise (1) that the decarbonisation of space heating in Germany goes hand in hand with the need to decarbonise the electricity grid and (2) the need for planners to start considering future developments as part of building energy system planning.

ОБОСНОВАНИЕ ЭНЕРГОСБЕРЕГАЮЩЕЙ ФУНКЦИОНАЛЬНОЙ СХЕМЫ АККУМУЛЯЦИОННОЙ УСТАНОВКИ ДЛЯ НАГРЕВА ВОДЫ НА ФЕРМАХ КРС

Analysis of electric energy consumption on cattle farms has shown that hot water supply is one of the energy-intensive technological processes on such farms. In order to save energy resources when heating water, a functional scheme of an accumulator installation has been developed that allows heating water for watering cows and providing technological needs. The standard water temperature for drinking is 12-15 degrees Celsius, for technological needs - 55-65 degrees Celsius. (Research purpose) The research purpose is substantiating and developing a functional scheme of an energy-saving installation for heating water using solar radiation for technological needs and thermal energy of ventilation air removed from the premises for watering cows on cattle farms. (Materials and methods) Applied patent search on the websites of Rospatent and Yandex.Patents. The analysis of analytical calculation dependencies was performed to determine the main technical characteristics of water heating installations for animal watering and technological purposes. (Results and discussion) A functional scheme of the hot water supply installation was proposed, including a water heater for technological needs using solar radiation energy and a water heater for animal watering using a thermoelectric heat pump and the heat of the ventilation air removed from the farm premises. (Conclusions) Developed a functional scheme of an accumulative water heating unit for watering cows and technological needs on cattle farms. It has been shown that the proposed scheme allows using the heat of the air removed from the premises and the renewable heat of solar radiation as alternative sources to traditional methods of heating water. The possibility of using low-potential thermal energy of the removed ventilation air for hot water supply of the animal watering system using a thermoelectric heat pump and heat pipes, as well as a solar collector for heating water for the technological needs of the farm, was investigated.

Combining expansion turbines, heat pumps, and low-temperature solar heat for enhanced primary energy savings in gas pressure regulating stations

According to previous studies, gas pressure regulating and metering stations (GPRMS) in Germany account for a primary energy consumption between 1.4 and 2.0 TWh/a for the preheating of natural gas flowing through. This work assesses the potential of reducing this consumption through the combined use of expansion turbines, heat pumps, and solar thermal collectors. For this purpose, operation data of 57 GPRMS of a German gas network operator are used to design systems combining in different scenarios two and three of these technologies in each GPRMS. Using an in-house model developed in Python the 57 systems are simulated over one year with an hourly time step. The results show a potential for the installation of expansion turbines with a total capacity of 3.57 MWel, leading, combined with the renewable heating technologies, to a reduction of more than 99 % of the original gas consumption for gas preheating. The results are then extrapolated to the whole country using scaling factors, showing a potential for feeding-in between 510 and 1,140 GWh/a of surplus electricity into the grid, on top of the almost complete elimination of the gas consumption for gas preheating. In total, the use of the complete technical potential available would lead to net primary energy savings between 1,710 and 3,650 GWh/a and net CO2 emissions reductions between 470 and 1,010 kt/a. Overall, this work demonstrates that the combination of expansion turbines and heat pumps technically allows an almost complete decarbonation of the operation of GPRMS in Germany. In addition, significant amounts of electricity could be fed into the grid, especially during the winter months, which would contribute to decarbonise the electricity mix of the country. The amount of electricity fed into the grid can be increased with the additional use of low-temperature solar thermal systems. To exploit this potential in the future, current regulations should be adapted and targeted support programmes launched.

Nearly-zero carbon optimal operation model of hybrid renewable power stations comprising multiple energy storage systems using the improved CSO algorithm

In light of the abundant renewable energy resources in Northwestern China, this study introduces a novel hybrid power plant structure known as the (Renewable energy-concentrating solar power-combined heat and power) RCC system. The RCC system integrates various energy sources, including the photovoltaic, the wind power plant, the concentrating solar power (CSP) plant, and the combined heat and power (CHP) plant. It also incorporates power-to-gas (P2G) technology to convert wind and solar power surpluses into methane. Moreover, carbon capture and storage (CCS) technology is applied to capture carbon dioxide emissions from the CHP plants, which serves as a raw material for the P2G process. To address the energy trilemma, we develop a nearly-zero carbon emission optimization model for the RCC system, considering different renewable energy source (RES) endowments. The fuzzy membership function method is employed to identify the optimum satisfaction target across multiple attributes. An enhanced CSO algorithm is introduced and validated using a simulation study on a CSP plant in Dunhuang. The results show that compared with traditional power stations, the proposed RCC system can reduce the investment cost by 34.45 %, increase the operating income by 17.7 %, and reduce carbon emission by 3.2 %. At the same time, the methane stock in the system increased by 53.7 % compared with the traditional power station containing P2G equipment, which helps the hybrid power station to participate in the methane market and obtain more profits. In addition, the direct energy supply ratio of RES decreased by 83.16 %, reducing the risk of the system caused by the uncertainty of RES. To sum up, the proposed RCC system has a good development prospect.

Preparation and assessment of ionic liquid and few-layered graphene composites to enhance heat and mass transfer in adsorption cooling and desalination systems

Adsorption systems can utilise low-temperature renewable and waste heat sources, which have emerged as a feasible alternative to conventional water desalination and cooling systems. However, the material of poor heat and mass transfer performance stall their widespread utilisation. This article presents the development and investigation of new composites employing few-layered graphene platelets and ionic liquids, namely ethyl-methylimidazolium methane sulfonate ([EMIM][CH3SO3]) and Ethyl-methylimidazolium-chloride ([EMIM][Cl]) to address such challenges. The impact of the few-layered graphene platelets, thermal properties, water adsorption properties of the developed composites and their thermal diffusivity were experimentally investigated. Besides, the overall cyclic performance was studied experimentally at the material level and computationally at the component level by employing a previously validated 2D dynamic heat and mass transfer model. The experimental investigation indicated that pristine few-layered graphene has a surface area of 56.8978 m2/g and a relatively high thermal diffusivity of 22.23 mm2/s. The developed composites showed higher thermal diffusivity than the baseline adsorbent silica gel. The highest thermal diffusivity was 11.84 mm2/s for GP-CH3SO3-10, 394 times higher than silica gel. Water adsorption characteristics of the composites were carried out, and the Dubinin–Astakhov (D-A) model was employed to model the experimental isotherms with good accuracy. The cumulative advanced adsorption and thermal characteristics of the developed composites resulted in higher cyclic performance by up to 82 % and 85 % than that of the baseline silica gel.

Multiple fragmentation as a challenge for municipal heat transition with biogenic residues and waste in rural areas in Germany

In Germany, heating accounts for half of the final energy consumption and is still based mainly on fossil fuels. Nevertheless, the transition to renewable heat has been widely criticized for progressing too slowly. To accelerate the heat transition, an increased use of biogenic residues and waste is discussed as a possible approach, as model calculations show considerable potential for these materials. This paper examines the barriers to an increased use of biogenic residues and waste in the context of municipal heat transition, including their use in district heating networks. The results are based on qualitative stakeholder and expert interviews and focus groups in rural municipalities in Germany. As a central finding, this study identifies the main barriers as multiple fragmentations in different areas (material, utilization paths, actor structure, framework conditions and knowledge) and their interdependencies. These findings contribute to a better understanding of structural obstacles of heat transitions.

Potential Analysis and Feasibility Study on the Hydrothermal Utilization of Rivers—Using Marburg on the Lahn River as Case Study

Due to their high specific heat capacity and constant thermal regeneration through flow, rivers are a promising renewable environmental heat source. The suitability of a river for hydrothermal use depends on river section-specific and site-specific factors. This paper presents a methodological proposal for a river section-specific potential analysis and site-specific feasibility study. The presentation of measured values in the form of hydrographs and duration curves as well as the use of suitable mean values and confidence intervals are central steps in the evaluation. The application of the potential analysis showed that the discharge in particular influences the size of the heat potential, while the water temperature determines whether and how the hydrothermal use is possible. The focus of this work was on the analysis of water temperature. Its significance for hydro-thermal use is multi-layered, and an assessment should be carried out at different levels. Using two specific sites on the Lahn river as a case study, the feasibility study method is demonstrated in this paper.

ДОСЛІДЖЕННЯ ВИКОРИСТАННЯ АЛЬТЕРНАТИВНИХ ВИДІВ ПАЛИВА НА ПОЛТАВЩИНІ

The possibilities of using energy-resource solid household waste, agricultural waste, logging waste from forestry enter-prises, green waste from landscaping and growing energy crops as alternative renewable fuels to meet the goals of small-scale heat and power generation in Poltava Oblast are investigated. To study this issue, the specialists from the Departments of Applied Ecology and Nature Management and Heat and Gas Supply, Ventilation and Heat Power En-gineering of National University "Yuri Kondratyuk Poltava Polytechnic" were invited to join the project and a new specialization "Renewable Heat and Power Engineering, Alternative Fuels and Environmental Protection" was opened in the specialty 183 "Environmental Protection Technologies". The problem was included in the strategic development plan of Poltava region and included in the development of the Action Plan for Sustainable Energy Development and Climate of Poltava City Territorial Community until 2030 in accordance with the European initiative "Covenant of Mayors for Climate and Energy". The assessment of the bioenergy potential may become a significant environmental and economic basis for improving the regional bioenergy sector in Poltava Oblast in the future. A complex of methods of system analysis and the method of data analysis has been applied to achieve the goal of the research. An analysis of modern international literary sources, an analysis of the morphological composition of municipal and green waste, and an analysis of the energy potential of plant biomass were reviewed. As a result of research, the scientific and applied task of using local energy resources at the level of each individual community of the Poltava region, taking into account ecological, economic and social development, has been formulated and substantiated. Ref. 10, figure. Keywords: energy security, environmental security, alternative fuels, renewable energy sources, energy crops, solid household waste, small-scale energy, environmental impact.